Reduction of interference caused by a simultaneous transmission signal in the same frequency band as the received signal in the received signal

Abstract

In one embodiment, the remote antenna unit includes a transmitter, a receiver, an antenna array, and first and second interference circuits. The transmitter is configured to generate at least one transmit signal, and the receiver is configured to process at least one receive signal. The antenna array includes one or more antennas, at least one of which is coupled to the transmitter and configured to radiate a respective downlink signal in response to a respective one of the at least one transmit signal, and at least one of which is coupled to the receiver and configured to generate a respective one of the at least one receive signal in response to an uplink signal. The first and second interference circuits are coupled to the transmitter and the receiver, respectively, and each configured to reduce interference in each of the at least one receive signal.

Description

SUMMARY OF THE INVENTION

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 948,024, filed December 13, 2019, entitled "REDUCE, IN A RECEIVE SIGNAL, INTERFERENCE CAUSED BY SIMULTANEOUS TRANSMIT SIGNAL IN A SAME FREQUENCY BAND AS THE RECEIVE SIGNAL", which is hereby incorporated by reference in its entirety.

[0002] FIG. 1 is a block diagram of a distributed antenna system (DAS) 10 configured to couple to one or more base stations 12 and including one or more remote antenna units 14. Typically, each base station 12 corresponds to and is controlled by a particular mobile carrier such as T-Mobile®, Verizon®, or ATT®, and is configured to receive uplink signals and transmit downlink signals via one or more of the remote antenna units 14. For example, each base station 12 may be configured to receive uplink signals and transmit downlink signals via all of the remote antenna units 14 such that each mobile carrier is provided with the entire signal service area in which the DAS 10 is configured to function.

[0003] When the DAS 10 is invoked to operate in a radio access network (RAN) where the uplink-downlink patterns of multiple signals can change dynamically and may not be synchronized with each other, and operates according to a standard such as the 5G New Radio (5GNR) standard, the antenna 16 of one remote antenna unit 14 can receive an uplink signal while that antenna, or another antenna on the same or a different remote antenna unit, is transmitting a downlink signal in the same frequency band as the uplink, or even at one or more of the same carrier frequencies. In the conventional TDD mode, the DAS 10 would switch between Tx and Rx. That is, the uplink-downlink patterns of all TDD signals within the band are statically and synchronously switched between Tx / Rx in synchronization with the predictable pattern of the synchronized TDD signals carried by the DAS 10. In contrast, in newer standards such as 5GNR, the TDD signals within the band are changing dynamically and are not necessarily synchronized with each other, and therefore, in this case, there is no predictable Tx / Rx pattern to follow that would apply to all channels, making it difficult, at best, to operate the DAS 10 in the conventional TDD mode.

[0004] Unfortunately, when the antenna 16 of the remote antenna unit 14 is receiving an uplink signal while the antenna, or another antenna on the same or a different remote antenna unit, is transmitting a downlink signal, the received signal generated by the antenna in response to the uplink signal can include interference (e.g., non-linear distortion such as adjacent channel noise and amplifier noise) resulting from the transmit signal driving the antenna or one or more downlink signals transmitted by one or more other nearby antennas.

[0005] The transmitted signal that excites the receiving antenna 16 and one or more downlink signals transmitted by one or more other antennas are much more powerful at the receiving antenna than the uplink signal, so the transmit interference in the received signal typically "swamps" the uplink component of the received signal.

[0006] For example, while a 100 milliwatt (mW) signal with a -45 dBc channel leakage power ratio (ACLR) is transmitted simultaneously in an adjacent channel, to achieve a 5 dB noise figure for the received signal at a receiver coupled to the receiving antenna 16 with a 5 MHz uplink channel bandwidth, it is expected that the remote antenna unit 14 needs to be configured to reduce the total effective transmit interference power in the uplink channel by approximately 77 dB.

[0007] Therefore, there is also a need for a separation circuit and an interference cancellation circuit configured to reduce the transmit interference in the received signal generated by the remote antenna unit 14 of the DAS 10 operating in a radio access network to an acceptable level, and a need for a remote antenna unit incorporating such circuits.

[0008] In one embodiment, a remote antenna unit capable of satisfying the features described above includes a transmitter or a part thereof, a receiver or a part thereof, an antenna array, and first and second interference circuits. The transmitter, or a part thereof, is configured to generate at least one transmission signal, and the receiver, or a part thereof, is configured to process at least one reception signal. For example, as used herein, "transmitter" and "receiver" are understood to mean at least a part of a transmission or reception chain that can be split between a host location (e.g., base station 12 or master unit 18) and remote antenna unit 14. For example, generation (modulation) and processing (demodulation) may be performed back at base station 12 rather than at remote antenna unit 14. In one example, remote antenna unit 14 includes an RF front-end circuit, which may include, for example, a digital-to-analog converter (DAC), an upconverter, and a power amplifier on the downlink path, and a low-noise amplifier, a downconverter, and an analog-to-digital converter (ADC) on the uplink path. The antenna array includes one or more antennas, and each of at least one of the one or more antennas is coupled to the transmitter and is configured to radiate a respective downlink signal in response to each of the at least one transmission signals, and each of at least one of the one or more antennas is coupled to the receiver and is configured to generate a respective one of the at least one reception signals in response to an uplink signal. And the first and second interference circuits are each coupled to the transmitter and the receiver, and in each of the at least one reception signals, at least one transmission signal, at least one downlink signal radiated by one of the one or more antennas on the same remote antenna unit, and at least one interfering downlink signal radiated by one of the one or more other antennas on one or more other remote antenna units, and are each configured to reduce the interference caused by one or more of them.

[0009] For example, such a remote antenna unit may include a plurality of different interference reduction circuits that together provide an appropriate level of interference reduction for the received signal.

[0010] As a further example, one of the interference reduction circuits may be a separation circuit configured to separate a transmitter from a receiver to reduce interference caused by a transmitted signal to an antenna from a received signal from the same antenna, where the transmitted and received signals at least partially overlap in time and the interference includes passive intermodulation (PIM).

[0011] In yet a further example, one of the interference reduction circuits may be an analog interference cancellation circuit configured to provide primary linear correction by canceling a downlink signal from an adjacent antenna on the same or a different remote antenna unit where the transmitted signal to the same antenna, or the transmitted or downlink signal, at least partially overlaps in time with the received signal.

[0012] In still a further example, one of the interference cancellation circuits may be a digital interference cancellation circuit configured to provide primary linear correction and non - linear correction to the received signal. The digital interference cancellation circuit may provide primary linear correction to the received signal in the same manner as the analog interference cancellation circuit described above and may provide non - linear correction by canceling out - of - band distortion (also called frequency sidebands and frequency "skirts") that may still be close enough to the frequency of the received signal such that it is difficult to reduce this distortion to an acceptable level with conventional filtering.

[0013] In yet another example, each of one or more of the interference reduction circuits may include one or more control loops, and two or more of the interference reduction circuits may form or otherwise be part of a control loop. For example, the digital interference cancellation circuit may use negative feedback to control the parameters of the separation circuit to further reduce the level of transmit interference in the received signal.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0015] As used herein, the terms “about,” “substantially,” and similar words indicate that a given quantity b can be within the range of b ± 10% of b, or within the range of b ± 1 if |10% of b| < 1. As used herein, the terms “about,” “substantially,” and similar words also indicate that a range b to c can be b - 0.10(c - b) to c + 0.10(c - b). With respect to the flatness of a surface or other region, as used herein, the terms “about,” “substantially,” and similar words indicate that the difference in thickness between the highest and lowest points of the surface / region does not exceed 0.20 millimeters (mm).

[0016] As described above, FIG. 1 is a diagram of a DAS 10 coupled to one or more base stations 12 and including one or more remote antenna units 14.

[0017] In an embodiment, one or more of the remote antenna units 14 can be configured to reduce interference in one or more received signals caused by one or more respective transmit signals to the same antenna and by one or more downlink signals from antennas on the same remote antenna unit or on one or more different remote antenna units.

[0018] The remote antenna unit 14 of the DAS 10 is typically distributed within a building (e.g., an office building, a warehouse, a mall, a sports complex) or in or around an outdoor area (e.g., a stadium, downtown, an outdoor event venue, a park, a beach) so that people can use their wireless devices (e.g., smartphones, tablets, laptops) while inside the building or outdoor area, providing a wireless communication service range. Examples of types of wireless service ranges that the DAS can provide include Wi-Fi (registered trademark), cellular phone service, and data service for one of many available Long-Term Evolution (LTE) frequency bands (e.g., B1, B3, B7, B25, and B66). And the frequency range in which the DAS 10 can be configured to operate is, for example, approximately 600 MHz to 71 GHz. For example, the DAS 10 can be configured to operate in the 5GNR frequency band of approximately 3.4 GHz to 3.8 GHz.

[0019] In addition to the remote antenna unit 14, the DAS 10 is coupled to or includes one or more master units 18 that are communicatively coupled to the remote antenna unit 14. In further embodiments, the DAS 10 includes a digital DAS, and DAS traffic is distributed in digital form between the master unit 18 and the remote antenna unit 14. In other embodiments, the DAS 10 is at least partially implemented as an analog DAS, and DAS traffic is distributed in at least a portion of the path between the master unit 18 and the remote antenna unit 14 in analog form.

[0020] Each master unit 18 is also communicatively coupled to one or more base stations 12. One or more of the base stations 12 may coexist with each respective master unit 18 to which it is coupled (e.g., a base station 12 may be dedicated to providing base station capacity to the DAS 10). Also, one or more of the base stations 12 may be located remotely from each respective master unit 18 to which it is coupled (e.g., a base station 12 may be a macro base station that provides base station capacity to a macro cell in addition to providing capacity to the DAS 10). In the latter case, the master unit 18 may be coupled to a donor antenna (not shown in FIG. 1) to wirelessly communicate with the remotely located base station 12. Further, one or more of the one or more base stations 12 may each be coupled to a master unit 18 using a respective network of attenuators, combiners, splitters, amplifiers, filters, cross-connects, etc., each network of which is referred to by each respective network as a point of interface (POI) circuit 20. This is done so that in the downlink, a set of desired RF carriers output by the base station 12 can be extracted, combined, and routed to the appropriate master unit 18, and in the uplink, a set of desired carriers output by the master unit 18 can be extracted, combined, and routed to the appropriate interface of each base station.

[0021] The base stations 12 may each be implemented as respective conventional monolithic base stations. Also, the base stations 12 may each be implemented using a distributed base station architecture in which a baseband unit (BBU) (not shown in FIG. 1) is coupled to one or more remote radio heads (RRHs) (not shown in FIG. 1), and the fronthaul between the BBU and the RRH uses a stream of digital IQ samples. Examples of such an approach are described in the specifications of the Common Public Radio Interface (CPRI), the Open Base Station Architecture Initiative (OBSAI), and the Open RAN (O-RAN) family, which are incorporated herein by reference.

[0022] Each master unit 18 can be configured to use a broadband interface or a narrowband interface to the base station 12, respectively. Further, each master unit 18 can be configured to interface with the base station 12 using an analog radio frequency (RF) interface or a digital interface (e.g., using CPRI, OBSAI, or an O-RAN digital interface), respectively.

[0023] Conventionally, each master unit 18 interfaces with each base station 12 using an analog radio frequency signal by which each base station communicates with user equipment (e.g., smartphones, tablets, laptops) 22 using a suitable air interface standard. The DAS 10 operates as a distributed repeater for such radio frequency signals. An RF signal transmitted from each base station 12 (also referred to herein as a "downlink RF signal") is received by one or more master units 18. Each master unit 18 uses the downlink RF signal to generate a downlink transport signal that is distributed to one or more of the remote antenna units 14. Each such remote antenna unit 14 receives the downlink transport signal, reconstructs a version of the downlink RF signal based on the downlink transport signal, and the reconstructed downlink RF signal is radiated from at least one antenna array 16 included in or otherwise coupled to that remote antenna unit.

[0024] The same process is carried out in the uplink direction. An RF signal transmitted from the user equipment 22 (also referred to herein as the "uplink RF signal") is received by one or more remote antenna units 14. Each remote antenna unit 14 uses the uplink RF signal to generate an uplink transport signal that is transmitted from the remote antenna unit 14 to the master unit 18. Each master unit 18 receives the uplink transport signal transmitted from one or more remote antenna units 14 coupled thereto. The master unit 18 synthesizes the data or signals communicated via the uplink transport signal received at the master unit and reconstructs a version of the uplink RF signal received at the remote antenna unit 14. The master unit 18 communicates the reconstructed uplink RF signal to one or more base stations 12. Thus, the signal and communication service range of the base station 12 can be extended using the DAS 10.

[0025] One or more intermediate units 24 (some of which are also referred to herein as "extension units") can be disposed between the master unit 18 and one or more of the remote antenna units 14. This can be done, for example, to increase the number of remote antenna units 14 that a single master unit 18 can supply, to increase the distance from the master unit to the remote units, and / or to reduce the amount of wiring necessary to couple the master unit to its associated remote antenna units.

[0026] As described above, DAS 10 can be implemented as a "digital" DAS. In a "digital" DAS, signals received from and provided to base station 12 and user equipment 22 are used to generate digital in-phase (I) and quadrature (Q) samples that are communicated between master unit 18 and remote antenna unit 14. This digital IQ representation of the original signals received from base station 12 and from user equipment 22 still maintains the original modulation (i.e., changes in the amplitude, phase, or frequency of the carrier) used to convey voice or data information according to the cellular air interface protocol used for wireless communication between the base station and the user equipment. Note that examples of such cellular air interface protocols include, for example, 5G NR, Global System for Mobile Communications (GSM®), Universal Mobile Telecommunications System (UMTS), and Long Term Evolution (LTE) air interface protocols. Also, each stream of digital IQ samples represents or includes a portion of the radio spectrum. For example, digital IQ samples can represent a single radio access network carrier (e.g., a 5 MHz UMTS or LTE carrier) over which voice or data information is modulated using the UMTS or LTE air interface. However, each such stream can also represent multiple carriers (e.g., a band of the frequency spectrum or a sub-band of a given band of the frequency spectrum).

[0027] Furthermore, one or more of the master units 18 may be configured to interface with one or more base stations 12 using an analog RF interface (e.g., via either the analog RF interface of a conventional monolithic base station 12 or an RRH). As described above, the base station 12 may also be coupled to the master unit 18 using a network of attenuators, combiners, splitters, amplifiers, filters, cross-connects, etc. (collectively, sometimes referred to as a “point of interface” or “POI” 20). This is done so that, in the downlink, a set of desired RF carriers output by the base station 12 can be extracted, combined, and routed to the appropriate master unit 18, and, in the uplink, a set of desired carriers output by the master unit can be extracted, combined, and routed to the appropriate interface of each base station.

[0028] Each master unit 18 may generate digital IQ samples from an analog radio signal received at radio frequency (RF) by downconverting the received signal to an intermediate frequency (IF) or baseband, digitizing the downconverted signal to produce actual digital samples, and digitally downconverting the actual digital samples to produce digital in-phase (I) and quadrature (Q) samples. These digital IQ samples may also be filtered, amplified, attenuated, and / or resampled or decimated to a lower sample rate. Digital samples may be generated in other ways. Each stream of digital IQ samples represents a portion of the radio frequency spectrum output by one or more base stations 12. Each portion of the radio frequency spectrum may include, for example, a band of the radio spectrum, a sub-band of a given band of the radio spectrum, or an individual radio carrier.

[0029] Similarly, on the uplink, each master unit 18 can generate an uplink analog radio signal from one or more streams of digital IQ samples received from one or more remote antenna units 14 by digitally synthesizing (e.g., by digitally adding such digital IQ samples) a stream of digital IQ samples representing the same carrier or frequency band or sub-band, digitally up-converting the synthesized digital IQ samples to generate actual digital samples, performing a digital-to-analog process on the actual digital samples to generate an IF or baseband analog signal, and up-converting the IF or baseband analog signal to a desired RF frequency. The digital IQ samples can also be filtered, amplified, attenuated, and / or resampled or interpolated to a higher sample rate before and / or after being synthesized. The analog signal can be generated in other ways (e.g., the digital IQ samples are provided to a quadrature digital-to-analog converter that directly generates an analog IF or baseband signal).

[0030] One or more of the master units 18 can be configured to interface with one or more base stations 12 using (additionally or instead of) a digital interface that interfaces with one or more base stations via an analog RF interface. For example, the master unit 18 can be configured to interact directly with one or more BBU's using a digital IQ interface used for communication between a BBU and an RRH (e.g., using a CPRI serial digital IQ interface).

[0031] On the downlink, each master unit 18 terminates one or more downlink streams of digital IQ samples provided to it from one or more BBU's, and, if necessary, converts them (e.g., by resampling, synchronizing, combining, separating, adjusting gain, etc.) into a downlink stream of digital IQ samples that are compatible with the remote antenna units 14 used in the DAS 10. On the uplink, each master unit 18 receives an uplink stream of digital IQ samples from one or more remote antenna units 14, digitally combines (e.g., by digitally adding such digital IQ samples) streams of digital IQ samples representing the same carrier or frequency band or sub-band, and, if necessary, converts them (e.g., by resampling, synchronizing, combining, separating, adjusting gain, etc.) into an uplink stream of digital IQ samples that are compatible with one or more BBU's coupled to that master unit.

[0032] Each master unit 18 may also be implemented in other ways.

[0033] On the downlink, each remote antenna unit 14 receives a stream of digital IQ samples from one or more master units 18, and each stream of digital IQ samples represents a portion of the radio frequency spectrum output by one or more base stations 12.

[0034] Each remote antenna unit 14 is communicatively coupled to one or more master units 18 using, for example, one or more optical fibers or cables, one or more Ethernet-compatible cables 26 (e.g., one or more CAT-6A cables), or any other suitable coupling medium. For example, in this embodiment, each remote antenna unit 14 is directly coupled via a single Ethernet cable 26, or indirectly via a plurality of Ethernet-compatible cables 26 such as a first Ethernet cable connecting the remote antenna unit to a patch panel or an expansion / intermediate unit 24 and a second optical fiber cable 28 connecting the patch panel or the expansion / intermediate unit to the master unit, to the master unit 18. Each remote antenna unit 14 can be coupled to one or more master units 18 in other ways. Also, the master unit 18 or the expansion / intermediate unit 24 can include one or more instances of a power sourcing equipment (PSE) configured to provide power to the remote antenna units 14.

[0035] In the exemplary DAS 10 shown in FIG. 1, it is shown that a remote antenna unit 14 has another coexisting expansion unit 14 (also referred to herein as an “expanded remote antenna unit”) communicatively coupled thereto. Subordinating a coexisting expanded remote antenna unit 14 to another remote antenna unit 14 can be done to expand the number of frequency bands radiated from the same location and / or to support MIMO services (e.g., different coexisting remote antenna units radiate and receive different MIMO streams for a single MIMO frequency band). The remote antenna unit 14 is communicatively coupled to the expanded remote antenna unit 14 using an optical fiber cable, a multi-core cable, a coaxial cable, etc. In such an implementation, the expanded remote antenna unit 14 is coupled to the master unit 18 of the DAS 10 via the remote antenna unit 14.

[0036] FIG. 2 is a diagram of a portion of the remote antenna unit 14 of FIG. 1 according to an embodiment in which a portion of the remote antenna unit includes one or more interference reduction circuits. As used herein, the word "reduce" includes reducing interference to a non-zero value and reducing interference to approximately zero value, the latter also being referred to as "removing" interference.

[0037] The remote antenna unit 14 includes one or more transmitter circuits 40, an antenna array 42, a transmit-receive separation circuit 44, an analog interference cancellation circuit 46, a control circuit 48, a digital interference cancellation circuit 50, and one or more receiver circuits 52. The circuit diagram of FIG. 2 includes a single transmitter circuit 40 and a corresponding single receiver circuit 52, but the illustrated circuits can be repeated for each additional interference-related pair of corresponding transmitter and receiver circuits, provided that regardless of the number of transmitter and receiver circuits 52, the remote antenna unit 14 can include a single antenna array 42 and a single control circuit 48. Further, the antenna array 42 includes a plurality of antennas 60. For a non-multiple-input multiple-output (non-MIMO) configuration, each antenna 60 operates to transmit, receive, or both transmit and receive a single downlink signal or a single uplink signal at any given point in time, and each antenna can include one or more antenna elements configured to transmit or receive the same signal, possibly with respective phase shifts or respective amplitude attenuations (e.g., the antenna is a phased array antenna). In a MIMO configuration, each group of a plurality of antennas 60 within the antenna array 42 is configured to transmit or receive a downlink signal or an uplink signal, and during at least the transmission period of the MIMO configuration, each antenna within the group of a plurality of antennas is configured to transmit a respective distinct component of the MIMO downlink signal. Further, each transmitter circuit 40 can also be referred to as a downlink circuit, a downlink path, a transmission path, a partial transmitter, etc., and similarly, each receiver circuit 52 can also be referred to as an uplink circuit, an uplink path, a reception path, a partial receiver, etc.

[0038] Each transmitter circuit 40 located on the remote antenna unit 14 includes a digital-to-analog converter (DAC) 54, a frequency upshift circuit 56, and a power amplifier 58. The DAC 54 is configured to receive a digital baseband information signal generated by a signal processing circuit (not shown in FIG. 2) built into the remote antenna unit 14 to include data (or other information) from the base station 12 (FIG. 1), and is configured to convert the digital baseband information signal into an analog baseband information signal. The frequency upshift circuit 56 is configured to modulate a carrier signal using the analog signal, and the carrier signal has a carrier frequency within a frequency band (e.g., 3.4 GHz to 3.8 GHz) in which the DAS 10 (FIG. 1) is configured to operate. For example, a portion of each transmitter circuit 40 on the remote antenna unit 14 may upshift each DAC output signal using different carrier frequencies within the same frequency band. The power amplifier 58 is configured to amplify the modulated carrier signal to generate a transmission signal and drive one or more antennas of the antenna array 42 using the transmission signal. The digital baseband information signal may itself include or be modulated using one or more carrier signals, and thus the carrier signal that the frequency upshift circuit 56 may use to upshift the DAC output signal (hereinafter referred to as the upshifted carrier signal) is added to such other one or more carrier signals. Further, the circuit for transmitting the downlink signal may be fully included on the remote antenna unit 14 as the transmitter circuit 40, or may be included in both the remote antenna unit and the base station 12 or the master unit 18 (FIG. 1). Therefore, the transmitter circuit 40 may include the entire transmission circuit or only a portion of the transmission circuit. In related embodiments, the transmitter circuit 40 implements the DAC using digital upconversion (DUC).In such an embodiment, a digital upconverter (not shown in FIG. 2) is located on the input side of the DAC54, receives the baseband IQ stream, digitally upconverts (upshifts) the IQ stream to a higher frequency band, and provides the upshifted IQ stream to the DAC54 that converts the upshifted IQ stream from a digital signal to an analog signal.

[0039] The antenna array 42 includes one or more antennas 60, each of which is configured to operate as both a transmit antenna and a receive antenna (other embodiments, such as one or more embodiments described below, may include one or more transmit antennas configured for transmission only and one or more receive antennas configured for reception only). For example, the antenna array 42 can be a multiple-input multiple-output (MIMO) antenna array that includes two or more antennas 60. Alternatively, the antenna array 42 can include only a single antenna 60. In operation during the transmit mode, each antenna 60 of the array 42 is configured to convert the transmit signal from its respective transmitter circuit 40 into a respective downlink signal, i.e., in response to being excited by the transmit signal, each antenna radiates its respective downlink signal, e.g., to the user equipment 22 of FIG. 1. When the antenna array 42 is a MIMO array, the combination of the signals radiated by the antennas 60 of the array can be considered a single downlink signal, but as described below, each MIMO component transmit signal is considered separately for the purpose of interference cancellation. In operation during the receive mode, each antenna 60 of the array 42 receives an uplink signal, e.g., from the user equipment 22 of FIG. 1, and converts the uplink signal into a respective receive signal. When the antenna array 42 is a MIMO array, the combination of the signal components received by the antennas 60 of the array can be considered a single uplink signal, but as described below, each MIMO component receive signal is processed by its respective receiver circuit and considered separately for the purpose of interference cancellation.

[0040] The transmit-receive separation circuit 44 is configured to reduce interference in the received signal from the antenna 60 of the antenna array 42 caused by the transmit signal from the transmitter circuit 40, particularly when the transmit and receive signals are simultaneous or otherwise temporally overlapping. Since the transmit signal path by which the transmit signal propagates from the transmitter circuit 40 to the antenna array 42 can at least partially overlap with the receive signal path by which the received signal propagates from the antenna array to the corresponding receiver circuit 52, a portion or component of the transmit signal can "leak" into the received signal. Also, since the transmit signal is typically significantly stronger than the received signal, even a small amount of such leakage can cause the transmit signal to "swamp" the received signal in the receiver circuit 52. To limit such leakage to an acceptable level for the application, the transmit-receive separation circuit 44 is configured to electrically isolate the receiver circuit 52 from the transmitter circuit 40. For example, the transmit-receive separation circuit 44 can provide a separation that is approximately 10 dB to 20 dB higher than that of a conventional separation circuit (e.g., a circulator), for example. Further, one or more parameters of the transmit-receive separation circuit 44 can be adjustable by the digital interference cancellation circuit 50, particularly when the transmit-receive separation circuit and the digital interference cancellation circuit operate as part of a closed feedback control loop to reduce transmitter interference in the received signal to the lowest achievable level. Additional embodiments of the transmit-receive separation circuit 44 are described in detail below in conjunction with FIGS. 7-16.

[0041] The analog interference cancellation circuit 46 is configured to further reduce interference from the transmit signal coupled to the same antenna 60 that generates the received signal in the corresponding received signal to the receiver circuit 52. That is, the transmit-receive separation circuit 44 and the analog interference cancellation circuit 46 together can reduce transmitter interference in the received signal to a level lower than the level of interference reduction that either of the two circuits 44 and 46 can provide alone.

[0042] The analog interference cancellation circuit 46 may be configured to provide first - order correction to the received signal by removing or otherwise canceling from the received signal the components of the transmitted signal that enable the transmit - receive separation circuit 44 to leak into the received signal. The analog interference cancellation circuit 46 generates an estimated first - order representation of the leaked components of the transmitted signal as an analog correction signal so as to appear in the corresponding receiver circuit 52, and provides the analog correction signal to the receiver circuit 52 configured to reduce transmit interference by combining the correction signal with the received signal, thereby performing such first - order correction. For example, the receiver circuit 52 may be configured to subtract the analog correction signal from the received signal to remove or otherwise cancel some or all of the leaked components of the transmitted signal from the received signal. Alternatively, the analog interference cancellation circuit 46 may be configured to correct for sources of interference other than leakage of the transmitted signal into the received signal. For example, if the impedance of the corresponding antenna 60 of the antenna array 42 does not match well with the effective output impedance of the transmit - receive separation circuit 44, this impedance mismatch may redirect a portion of the transmitted signal to the antenna 60, and thus, the redirected portion of the transmitted signal may be superimposed on the received signal. Further, a portion of the downlink signal radiated by the antenna 60 of the array 42 in response to the transmitted signal may be reflected from an object external to the remote antenna unit 14 and return to the antenna 60. Therefore, the analog interference cancellation circuit 46 may be configured to generate a first - order analog correction signal that also takes into account the redirected portion of the transmitted signal and the redirected portion of the downlink signal superimposed on the received signal at the antenna 60. Further, the analog interference cancellation circuit 46 may include or be part of one or more control loops configured to reduce transmit interference in the received signal to a minimum achievable value. The analog interference cancellation circuit 46 is further described below in conjunction with FIGS. 3 - 6 and FIGS. 17 - 19.

[0043] The control circuit 48 is configured to control the operation of the analog and digital interference canceler circuits 46 and 50, and may also be configured to control the operation of one or more other circuits built into the remote antenna unit 14. For example, the control circuit 48 can be, or can include, one or more microprocessors or microcontrollers. Further, the control circuit 48 can implement some or all of one or both of the analog and digital interference canceler circuits 46 and 50. For example, the control circuit 48 can be, can include, or can be disposed on or implemented by a digital signal processor (DSP) or a field programmable gate array (FPGA) configured to implement the digital interference canceler circuit 50.

[0044] The digital interference canceler circuit 50 is configured to further reduce interference from the transmission signal coupled to the antenna 60 configured to generate a received signal in the corresponding received signal to the receiver circuit 52. That is, the transmit-receive separation circuit 44, the analog interference canceler circuit 46, and the digital interference canceler circuit 50 together can reduce the level of transmission interference in the received signal more than any one of the three circuits 44, 46, and 50 alone.

[0045] The digital interference canceler circuit 50 can be configured to provide first-order linear correction and non-linear correction to the received signal by removing or otherwise canceling components of the transmission signal that allow the transmit-receive separation circuit 44 to leak into the received signal.

[0046] The digital interference cancellation circuit 50 can be configured to perform such a linear correction by providing a digital correction signal to a receiver circuit configured to reduce transmit interference by generating an estimated linear representation of the leaked components of the transmit signal such that the components appear in the corresponding receiver circuit 52 as a digital correction signal and by combining the correction signal with the received signal. For example, the receiver circuit 52 can be configured to subtract the digital correction signal from the analog-corrected and digitized received signal to remove some or all of the leaked components of the transmit signal that pass through the separation circuit 44 and reach the analog interference cancellation circuit 46 from the received signal. Alternatively, the digital interference cancellation circuit 50 can be configured to correct for sources of leakage other than the transmit signal leaking into the received signal. For example, the digital interference cancellation circuit 50 can be configured to generate a first-order digital correction signal that also takes into account the redirected portions of the transmit signal and the redirected portions of the downlink signal superimposed on the received signal at the antenna 60, as described above in conjunction with the analog interference cancellation circuit 46.

[0047] The digital interference cancellation circuit 50 can also be configured to perform non-linear correction by generating an estimated representation of the non-linear leaked components of the transmit signal as part of the digital correction signal such that the non-linear leaked components appear in the corresponding receiver circuit 52. For example, one or more of the DAC 54, the frequency up-shift circuit 56, and the power amplifier 58 of the transmitter circuit 40 can introduce non-linear components, such as total harmonic distortion, into the transmit signal. Such non-linear components often give rise to "skirt" signals that appear as frequency sidebands that "skirt" the transmit signal and the corresponding downlink signal.

[0048] The digital interference cancellation circuit 50 may be configured to perform non-linear correction by generating an estimated representation of the non-linear component that the receiver circuit 52 may introduce into the received signal as part of the digital correction signal. For example, one or more of the low noise amplifier 64, the frequency downshift circuit 66, and the analog-to-digital converter (ADC) 68 of the receiver circuit 52 may introduce non-linear components into the received signal, such as total harmonic distortion. Such non-linear components may combine with the non-linear components of the transmitted signal to form the above-mentioned skirt signal at the output of the receiver ADC.

[0049] Each receiver circuit 52 located on the remote antenna unit 14 is configured to adjust the received signal from each antenna 60 of the antenna array 42 and provide the adjusted received signal to the signal processing circuit on the remote antenna unit 14. The signal processing circuit is configured to provide the processed received signal to the base station 12 (FIG. 1) of the DAS 10. The receiver circuit 52 includes a first signal combiner 62, for example, an adder, a low noise amplifier (LNA) 64, a frequency downshift circuit 66, an ADC 68, and a second signal combiner 70, for example, an adder. The signal combiner 62 is configured to combine the analog correction signal from the analog interference cancellation circuit 46 with the received signal from each antenna 60 of the antenna array 42. For example, the signal combiner 62 is an adder configured to subtract the analog cancellation signal from the received signal. The LNA 64 is configured to amplify the once-corrected received signal, and the frequency downshift circuit 66 is configured to downshift the once-corrected received signal to the baseband frequency range. The ADC 68 is configured to convert the analog baseband received signal into a digital baseband received signal, and the combiner 70 is configured to combine the digital correction signal from the digital interference cancellation circuit 50 with the once-corrected digital received signal. For example, the combiner 70 is an adder configured to subtract the digital correction signal from the once-corrected digital received signal to generate a twice-corrected digital received signal. Then, the signal processing circuit built into the remote antenna unit 14 or elsewhere (e.g., the master unit 18, the base station 12 in FIG. 1) is configured to convert the twice-corrected digital received signal into several modulated subcarriers so as to recover the data carried by the signal received by the signal processing circuit. The signal processing circuit may include an error correction circuit and other circuits so as to affect data recovery. Further, the circuit for receiving the uplink signal may be completely included on the remote antenna unit 14 as the receiver circuit 52, or may be included in both the remote antenna unit 14 and the base station 12 or the master unit 18 (FIG. 1).Accordingly, the receiver circuit 52 may include the entire receiving circuit or only a part of the receiving circuit.

[0050] Referring further to FIG. 2, the operation of the remote antenna unit 14 is described according to an embodiment in which the remote antenna unit 14 receives an uplink signal using the same antenna 60 and simultaneously transmits a downlink signal using the antenna 60.

[0051] The base station 12 (FIG. 1) transmits a signal to a signal processing circuit (not shown in FIGS. 1-2) built into the master unit 18 or the remote antenna unit 14. The signal processing circuit modulates one or more baseband carrier frequencies using data in the digital domain and generates a digital time-domain signal from the one or more modulated carrier frequencies. For example, the signal processing circuit may modulate the baseband carrier using 16 or 64 quadrature amplitude modulation (16-QAM, 64-QAM). Alternatively, the base station 12 performs this modulation.

[0052] Next, the DAC 54 converts the digital time-domain signal from the signal processing circuit into an analog time-domain signal.

[0053] Next, the frequency upshift circuit 56 upshifts the analog time-domain signal in frequency to the broadcast frequency band (e.g., 3.4 GHz to 3.8 GHz) in which the remote antenna unit 14 is configured. The frequency upshift circuit 56 may perform this frequency upshift in any suitable manner, such as by modulating the carrier signal with the analog time-domain signal.

[0054] Next, the power amplifier 58 amplifies the frequency upshifted analog time-domain signal (e.g., amplifies the modulated carrier signal) to generate a transmission signal.

[0055] Next, the transmit-receive separation circuit 44 couples the transmission signal to the antenna 60 while reducing the magnitude of the component of the transmission signal that "leaks" into the receiver circuit 52.

[0056] Next, in response to being excited by the transmission signal, antenna 60 radiates a downlink signal including data in the transmission signal.

[0057] While antenna 60 is radiating the downlink signal, control circuit 48 controls analog and digital interference cancellation circuits 46 and 50 to generate an analog correction signal and a digital correction signal, respectively. Analog interference cancellation circuit 46 generates an analog correction signal from the transmission signal or in response thereto, and digital interference cancellation circuit 50 generates a digital correction signal from the digital time domain signal from the signal processing circuit or in response thereto. Further, control circuit 48 may control digital interference cancellation circuit 50 to generate an adjustment signal for reducing the leakage of the transmission signal to receiver circuit 52 to the lowest achievable level in transmit-receive separation circuit 44. For example, digital interference cancellation circuit 50 may be coupled to receiver circuit 52 in a control loop configuration, may monitor the level of the transmit leakage component in the received signal or a signal derived therefrom, may dither the adjustment signal to determine the lowest achievable level of transmit signal leakage in the received signal or a signal derived therefrom, and then may set the value of the adjustment signal to maintain the level of transmit signal leakage at or near the determined lowest achievable level.

[0058] Antenna 60 also receives an uplink signal while radiating the downlink signal and converts the uplink signal into a received signal.

[0059] Signal combiner 62 combines the analog correction signal with the received signal to generate a once-corrected received signal. For example, if signal combiner 62 is an adder, signal combiner 62 subtracts the analog correction signal from the received signal to generate a once-corrected received signal.

[0060] The low-noise amplifier 64 amplifies the once-corrected received signal, and the frequency downshift circuit 66 frequency-shifts (e.g., demodulates) the once-corrected received signal into an analog time-domain received signal.

[0061] The ADC 68 converts the analog time-domain received signal into a digital time-domain received signal.

[0062] The signal combiner 70 combines the digital correction signal with the digital time-domain received signal to generate a twice-corrected digital time-domain received signal. For example, when the signal combiner 70 is an adder, the signal combiner 70 subtracts the analog correction signal from the digital time-domain received signal to generate a twice-corrected digital time-domain received signal.

[0063] A signal processing circuit (not shown in FIG. 2) decomposes the twice-corrected digital time-domain received signal into its data-modulated frequency components, and recovers the data carried by the uplink signal from the data-modulated frequency components.

[0064] Reduction of the linear and non-linear transmit interference in the data-modulated frequency components is typically provided by the transmit-receive separation circuit 44 and the analog and digital interference cancellation circuits 46 and 50, enabling the signal processing circuit (not shown in FIG. 2) to recover the data more accurately than the signal processing circuit with the separation and interference cancellation circuits omitted from the remote antenna unit 14.

[0065] Continuing to refer to FIG. 2, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, one or two of the transmit-receive separation circuit 44, the analog interference cancellation circuit 46, and the digital interference cancellation circuit 50 may be omitted from the remote antenna unit 14. Further, the control circuit 48 may include or otherwise implement the digital interference cancellation circuit 50. For example, the control circuit 48 may be a microprocessor, a microcontroller, an FPGA, or a combination or partial combination of a microprocessor, a microcontroller, and an FPGA, and may be configured to implement the functions and operations of the digital interference cancellation circuit 50. Further, the analog and digital interference cancellation circuits 46 and 50 may incorporate circuits or implement techniques disclosed in one or more of the following references incorporated herein by reference: U.S. Patent Publication No. 2017 / 0170903 to Jain et al., U.S. Patent No. 9,698,861 to Braithwaite, U.S. Patent No. 10,020,837 to Braithwaite, Full Duplex Radios, Bharadia et al. (2013), and IEEE 802.11 - 18 / 019 Ir0. In addition, each of the analog and digital interference cancellation circuits 46 and 50 may incorporate a circuit that is a modified version of a circuit disclosed in one or more of the above references, and may implement one or more techniques that are each a modified version of a technique disclosed in one or more of the above references. Further, a portion of the transmitter circuit 40 located on the remote antenna unit 14 may be modified from that described. For example, the frequency upshift circuit 56 may be omitted, and the base station 12, the master unit 18, or the transmitter circuit 40 may perform all frequency upshifts prior to the DAC 54 that is configured to generate a frequency upshifted analog time domain signal and provide it to the power amplifier 58. Or, the DAC 54 may be configured to perform some or all of the frequency upshift of the analog time domain signal. For example, the DAC 54 and the frequency upshift circuit 56 may be combined into a DAC frequency upshift circuit.Furthermore, a portion of the receiver circuit 52 located on the remote antenna unit 14 can be modified from what has been described. For example, the frequency downshift circuit 66 may be omitted, and the ADC 68, the base station 12, the master unit 18, or a combination or partial combination thereof may perform all frequency downshifts of the signal from the low noise amplifier 64 to generate a downshifted digital received signal. For example, the ADC 68 and the frequency downshift circuit 66 may be combined into an ADC frequency downshift circuit. Additionally, the topology (e.g., the order of components coupled in series) of a portion of the transmitter circuit 40 and the receiver circuit 52 located on the remote antenna unit 14 can be arranged in any suitable configuration. Further, in the receiver circuit 52, the LNA 64 can be located between the transmit-receive separation circuit 44 and the signal combiner 62 instead of being located between the adder and the frequency downshift circuit 66, and there may be a plurality of LNAs coupled in series, and other circuit topologies are contemplated. Furthermore, although described as operating in an open-loop mode, the analog interference cancellation circuit 46 may operate in a closed-loop mode, or may operate in both open-loop and closed-loop modes, and may further have one or more simultaneously functioning open-loops and closed-loops. Similarly, although described as operating in open-loop and closed-loop modes, the digital interference cancellation circuit 50 may operate in only one or more closed-loop modes or only one or more open-loop modes. Additionally, the embodiments described above in conjunction with FIG. 1, or below in conjunction with FIGS. 3 - 19, may be applicable to the remote antenna unit 14 of FIG. 2.

[0066] FIG. 3 is a diagram of the remote antenna unit 14 of FIG. 1, and the analog and digital interference cancellation circuits 46 and 50, according to one embodiment. In FIG. 3, reference items with the same numbers are common to FIGS. 1 - 3.

[0067] In the example shown in FIG. 3, the analog interference cancellation circuit 46 includes one or more filter paths 821 - 82 nand a finite impulse response (FIR) filter 80 including a signal combiner 84, such as an adder.

[0068] Each filter path 82 includes a respective delay circuit 86, a respective phase shift circuit 88, and a respective gain circuit 90. Each delay d of each delay circuit 86 configured to be applied to the transmission signal can be determined and set in advance in response to any suitable calculation algorithm or during a calibration procedure performed while the remote antenna unit 14 is not being used to transmit or receive downlink and uplink signals. Alternatively, each delay d can be dynamically adjusted by one or more control loops built into the remote antenna unit 14. Similarly, each phase shift ps and each gain a of each delay circuit 88 and gain circuit 90, respectively configured to be imparted to the delayed transmission signal, can be determined and set in advance in response to any respective suitable calculation algorithm or during respective calibration procedures performed while the remote antenna unit 14 is not being used to transmit or receive downlink and uplink signals. Alternatively, each of the phase shift ps and each gain a can be dynamically adjusted by one or more control loops built into the remote antenna unit 14. Further, each gain a of each amplifier 90 can be less than 1, equal to 1, or greater than 1.

[0069] The signal combiner 84 is configured to generate an analog correction signal in response to the output signals from paths 821 to 82 n For example, if the signal combiner 84 is an adder, the signal combiner 84 is configured to generate an analog correction signal equal to the sum of the output signals from paths 821 to 82 n

[0070] Referring further to FIG. 3, the digital interference cancellation circuit 50 includes a linear distortion estimator circuit 92, a non-linear distortion estimator circuit 94, a signal combiner 96, and a separation circuit controller 98. ​

[0071] The linear distortion estimator circuit 92 is configured to generate a first-order linear correction signal in response to a digital time-domain signal from the signal processing circuit, and the non-linear distortion estimator circuit 94 is configured to generate a non-linear correction signal in response to the same digital time-domain signal.

[0072] The signal combiner 96 is configured to generate a digital correction signal in response to the first-order linear and non-linear correction signals. For example, if the signal combiner 96 is an adder, the signal combiner 96 is configured to generate a digital correction signal equal to the sum of the first-order linear and non-linear correction signals.

[0073] The separation circuit controller 98 is configured to generate a control signal for adjusting one or more separation characteristics or parameters of the transmit-receive separation circuit 44 in response to the first-order linear and non-linear correction signals.

[0074] Referring further to FIG. 3, the operation of the remote antenna unit 14 is described according to an embodiment in which the remote antenna unit 14 receives an uplink signal using the same antenna 60 and simultaneously transmits a downlink signal using the antenna 60.

[0075] The remote antenna unit 14 operates as described above in conjunction with FIG. 2, and in addition to, instead of, or in place of one or more of the operations described above in conjunction with FIG. 2, performs the following operations.

[0076] The analog interference cancellation circuit 46 operates as follows.

[0077] Each delay circuit 86 applies a respective delay d to the transmission signal from the transmitter circuit 40.

[0078] Each phase shift circuit 88 applies a respective phase shift ps to the delayed transmission signals from the respective delay circuits 86 of the same path 82.

[0079] Each gain circuit 90 amplifies or attenuates the phase-shifted and delayed transmission signal from each phase shift circuit 88 by its respective gain a.

[0080] The signal combiner 84 generates an analog correction signal in response to the amplified, or attenuated, phase-shifted, and delayed version of the transmission signal output from the amplifiers 901 to 90 n For example, if the signal combiner 84 is an adder, the signal combiner 84 generates a digital correction signal equal to the sum of the amplified, or attenuated, phase-shifted, and delayed versions of the transmission signal output from the amplifiers 901 to 90 n The digital interference canceling circuit 50 operates as follows.

[0081] The linear distortion estimator circuit 92 generates a linear correction signal in response to the digital time domain signal from the signal processing circuit, which is either built into or not built into the remote antenna unit 14 although not shown in FIG. 3.

[0082] The non-linear distortion estimator circuit 94 generates a non-linear correction signal in response to the digital time domain signal.

[0083]

[0084] The signal combiner 96 generates a digital correction signal in response to the linear and non-linear correction signals from the estimator circuits 92 and 94, respectively. For example, if the signal combiner 96 is an adder, the signal combiner 96 generates a digital correction signal equal to the sum of the linear and non-linear correction signals.

[0085] ​Furthermore, the isolation circuit controller 98 generates a control signal for adjusting one or more isolation characteristics or parameters of the transmit-receive isolation circuit 44 in response to the primary linear and non-linear correction signals. For example, the controller 98 may dither the control signal to cause the transmit-receive isolation circuit 44 to achieve the highest level of isolation between the transmitter circuit 40 and the receiver circuit 52, and thus determine and maintain the operation of the transmit-receive isolation circuit 44 in terms of achieving the lowest level of leakage of the transmit signal into the received signal.

[0086] Continuing to refer to FIG. 3, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, each of one or more of the paths 82 of the analog interference cancellation circuit 46 may lack the phase shifter 88. Further, the digital interference cancellation circuit 50 may lack the isolation circuit controller 98. Additionally, the analog interference cancellation circuit 46 may include circuits such as those disclosed in Full Duplex Radios, Bharadia et al., which are incorporated herein by reference, or may include the disclosed circuits modified for inclusion in the remote antenna unit 14 configured to operate in the TDD mode. Similarly, the digital interference cancellation circuit 50 may include circuits disclosed in Full Duplex Radios, Bharadia et al., or may include the disclosed circuits modified for inclusion in the remote antenna unit 14 configured to operate in the TDD mode. In addition, the circuits on the remote antenna unit 14 notify one or more base stations 12 (FIG. 1) that the transmitter circuit 40 is generating a transmit signal while the antenna 60 is receiving an uplink signal, whereby the one or more base stations 12 may adjust the generation of the transmit signal of the transmitter circuit so that the generation of the transmit signal of the transmitter circuit does not coincide with the antenna 60 receiving the uplink signal. Further, the embodiments described above in conjunction with FIGS. 1 and 2, or below in conjunction with FIGS. 4-19, may be applicable to the remote antenna unit 14 of FIG. 3.

[0087] FIG. 4 is a diagram of the remote antenna unit 14 of FIG. 1 according to an embodiment configured to reduce transmission interference from one or more other antennas 602-60 of the same antenna array in the received signal generated by the antenna 601 of the antenna array 42. In FIG. 4, reference items with the same numbers are common to FIGS. 1-4. n In addition to the transmitter circuit 401, which is similar to the transmitter circuit 40 of FIGS. 2-3, the remote antenna unit 14 includes one or more other transmitter circuits 402-40

[0088] n which are each coupled to a respective one of the antennas 602-60 of the antenna array 42 and are otherwise similar to the transmitter circuit 401. n n n

[0089] In addition to the transmit-receive separation circuit 441, which is similar to the transmit-receive separation circuit 44 of FIGS. 2-3, the remote antenna unit 14 includes one or more other transmit-receive separation circuits 442-44 n which are each coupled between one of each of the transmitter circuits 402-40 n and one of each of the antennas 602-60 n and are otherwise similar to the transmit-receive separation circuit 441.

[0090] And in addition to the receiver circuit 521, which is similar to the receiver circuit 52 of FIGS. 2-3, the remote antenna unit 14 includes one or more other receiver circuits 522-52 n (not shown in FIG. 4) which are each coupled to the other antennas 602-60 of the antenna array 42 and are otherwise similar to the receiver circuit 521. n n

[0091] The other antennas 602-60 nIf one or more of them are each emitting a respective downlink signal while antenna 601 is receiving an uplink signal, since the downlink signal is typically much stronger than the uplink signal, one or more downlink signals will "swamp" the uplink signal such that the received signal generated by antenna 601 will include transmission interference that is much stronger than the component of the received signal corresponding to the received uplink signal.

[0092] Therefore, analog interference cancellation circuit 46 is configured not only to reduce transmission interference from the transmission signal generated by transmitter circuit 401 in the received signal from antenna 601, but also to reduce transmission interference from downlink signals transmitted by one or more of the other antennas 602 - 60 n Analog interference cancellation circuit 46 is therefore also configured to reduce transmission interference from downlink signals transmitted by one or more of the other antennas 602 - 60. Therefore, analog interference cancellation circuit 46 includes respective analog canceller circuits 1021 - 102 n for each transmitter circuit 401 - 40 n and, for example, each analog canceller circuit can be the same as FIR filter 80 in FIG. 3. Each analog canceller circuit 1021 - 102 n is configured to generate respective components of an analog correction signal, and signal combiner 104 is configured to generate an analog correction signal in response to the components. For example, if signal combiner 104 is an adder, signal combiner 104 generates an analog correction signal equal to the sum of the component signals from analog canceller circuits 1021 - 102 n .

[0093] Similarly, digital interference cancellation circuit 50 is configured not only to reduce transmission interference from the transmission signal generated by transmitter circuit 401 in the received signal from antenna 601, but also to reduce transmission interference from downlink signals transmitted by one or more of the other antennas 602 - 60 in the same antenna array 42 to which antenna 601 belongs. Therefore, digital interference cancellation circuit 50 includes respective digital canceller circuits for each transmitter circuit 401 - 40 n and is also configured to reduce transmission interference from downlink signals transmitted by one or more of the other antennas 602 - 60. Therefore, digital interference cancellation circuit 50 includes respective digital canceller circuits for each transmitter circuit 401 - 40n each of the digital canceller circuits 1061 to 106 with respect to n including, for example, each digital canceller circuit may include each linear distortion estimator circuit 92, each non-linear distortion estimator circuit 94, and each signal combiner 96 arranged as shown in FIG. 3. Each digital canceller circuit 106 is configured to generate each component of the digital correction signal, and the signal combiner 108 is configured to generate a digital correction signal in response to the components. For example, when the signal combiner 108 is an adder, the signal combiner 108 generates a digital correction signal equal to the sum of the component signals from the digital canceller circuits 1061 to 106 n Furthermore, the separation circuit controller 98 generates a control signal to the transmit-receive separation circuit 441 in response to either the component signals from the digital canceller circuits 1061 to 106 n or the component signals from the signals output by each of the linear and non-linear distortion estimator circuits 92 and 94 of the digital canceller circuit.

[0094] Continuing to refer to FIG. 4, when the antenna 601 receives an uplink signal and at the same time each of one or more of the transmitter circuits 401 to 40 n generates its respective transmission signal, the operation of the remote antenna unit 14 may be the same as the operation described above in conjunction with FIG. 2 and may also be the same as the operation described above in conjunction with FIG. 3, and the following operations may be added, or one or more of the following operations may replace one or more of the operations described above in conjunction with FIGS. 2 and 3.

[0095] The analog interference cancellation circuit 46 generates an analog correction signal in response to each of one or more transmission signals generated by each of the transmitter circuits 401 to 40 n respectively.

[0096] The digital interference cancellation circuit 50 generates a digital correction signal and a separation control signal in response to one or more digital time domain signals respectively generated by the signal processing circuit.

[0097] Although not shown, in some examples, the analog interference cancellation circuit 46 includes respective sets of the analog canceler circuits 102 for each of the other receiver circuits 522-52 n and each set of analog canceler circuits is similar in topology and operation to the set of analog canceler circuits 1021-102 n In other examples, the analog correction signal from the signal combiner 104 may be provided to each respective receiver circuit 52.

[0098] Similarly, although not shown, in some examples, the digital interference cancellation circuit 50 includes respective sets of the digital canceler circuits 106 for each of the other receiver circuits 522-52 n and each set of digital canceler circuits is similar in topology and operation to the set of digital canceler circuits 1061-106 n In other examples, the digital correction signal from the signal combiner 108 may be provided to each respective receiver circuit 52.

[0099] Although not shown, in some examples, the digital interference cancellation circuit 50 includes respective separation circuit controllers 98 for each of the other transmit-receive separation circuits 442-44 n and each separation circuit controller is similar in topology and operation to the separation circuit controller 98. In other examples, the control signal from the separation circuit controller 98 may be provided to a plurality of transmit-receive separation circuits 44.

[0100] Continuing to refer to FIG. 4, in an alternative embodiment, instead of or in addition to reducing transmit interference in the received signal, the remote antenna unit 14 may, while each of the one or more receiver circuits 52 is receiving a received signal, the transmitter circuits 401-40 nincluding a circuit configured to detect that one or more of them are each generating respective transmission signals, and configured to take corresponding measures in response to such detection. In other words, the remote antenna unit 14 is configured such that while at least one of the antennas is also receiving an uplink signal, antennas 601 to 60 n including a circuit configured to detect that one or more of them are each transmitting respective downlink signals. For example, the remote antenna unit 14 may be configured to send a notification to one or more base stations 12 (FIG. 1) that the remote antenna unit 14 is experiencing downlink transmission and uplink reception simultaneously, and in response to the notification, one or more base stations 12 may coordinate the transmission of downlink signals by the remote antenna unit 14 with the reception of uplink signals by the remote antenna unit 14 to reduce or eliminate simultaneous transmission and reception by the remote antenna unit 14. Alternatively, the remote antenna unit 14 may, while one or more of the antennas are each receiving an uplink signal, cause transmission separation circuits 441 to 44 n one or more of them to decouple respective transmission signals from each of antennas 601 to 60 n This latter measure may cause data loss, so the remote antenna unit 14 is also configured to notify one or more base stations 12 of the decoupled transmission signals such that one or more base stations 12 retransmit blocked or otherwise lost data for retransmission.

[0101] Continuing to refer to FIG. 4, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, the embodiments described above in conjunction with FIGS. 1 to 3, or below in conjunction with FIGS. 5 to 19, may be applicable to the remote antenna unit 14 of FIG. 4.

[0102] FIG. 5 is a diagram of the remote antenna unit 14 of FIG. 1 according to an embodiment in which the remote antenna unit is configured to reduce transmission interference from one or more other antennas on one or more other remote antenna units in the received signal generated by the antenna 601 of the antenna array 42. In FIG. 5, reference items with the same numbers are common to FIGS. 1 to 5.

[0103] In addition to the transmitter circuit 401 and the antenna 601, the remote antenna unit 14 includes one or more "sniffer" antennas 1201 to 120 m and one or more corresponding "sniffer" receiver circuits 1221 to 122 m As described above in conjunction with FIG. 4, the remote antenna unit 14 may also include one or more other transmitter circuits 402 to 40 n one or more other transmit-receive separation circuits 442 to 44 n one or more other receiver circuits 522 to 52 n and one or more other antennas 602 to 60 n (these other transmitter circuits, other transmit-receive separation circuits, other receiver circuits, and other antennas are omitted from FIG. 5 for clarity).

[0104] While the antenna 601 is receiving an uplink signal, if each of one or more other remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 5) is transmitting its respective downlink signal, the downlink signals (even those from another nearby remote antenna unit) are typically much more powerful than the uplink signal, so one or more downlink signals will "swamp" the uplink signal such that the received signal generated by the antenna 601 will include transmission interference that is much more powerful than the component of the received signal corresponding to the received uplink signal.

[0105] Since the antenna 60 (not shown in FIG. 5) on the remote antenna unit 14 is typically directional at the frequencies used in cellular wireless communication, each sniffer antenna 1201 to 120 mmay have respective orientations that increase the effective gain of the sniffer antenna with respect to each antenna 60 on another remote antenna unit 14. For example, the installer of the DAS 10 (FIG. 1) may orient each of the sniffer antennas 1201-120 m such that the main beam of m is directed at one or more antennas 60 on another remote antenna unit 14, in response to the location of each nearby other remote antenna unit 14. m Each of the sniffer antennas 1201-120

[0106] is configured to receive one or more respective downlink signals that interfere with the uplink signal received by the antenna 601 from each other remote antenna unit 14 (the other remote antenna units are not shown in FIG. 5) and to generate a respective sniffer readout signal in response to the one or more received downlink signals. m Each of the sniffer antennas 1201-120

[0107] is configured to convert each respective sniffer readout signal into a corresponding amplified sniffer readout signal suitable as an input to the analog interference cancellation circuit 46 and into a sniffer digital time domain signal suitable as an input to the digital interference cancellation circuit 50. Each of the sniffer receiver circuits 1221-122 m includes a respective LNA 124, a respective frequency downshift circuit 126, and a respective ADC 128, which may be similar to the LNA 641, the frequency downshift circuit 661, and the ADC 681 of the receiver circuit 521, respectively. Aligning the LNA 641 and 124, the frequency downshift circuit 661 and 126, and the ADC 681 and 128 may increase the level of transmit interference reduction that the digital interference cancellation circuit 50 can provide. For example, such alignment may be achieved by placing the LNA 641 and 124, the frequency downshift circuit 661 and 126, and the ADC 681 and 128 on the same integrated circuit die. m

[0108] ​ Therefore, the analog interference cancellation circuit 46 is configured not only to reduce transmission interference from the transmission signal generated by the transmitter circuit 401 in the received signal from the antenna 601, but also to reduce transmission interference from one or more downlink signals transmitted by one or more other antennas 60 on one or more other remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 5). Therefore, the analog interference cancellation circuit 46 includes the analog cancellation circuit 130 for the transmitter circuit 401 m+1 and, in addition to including, for each of the sniffer receiver circuits 1221 to 122 m the respective analog cancellation circuits 1301 to 130 m For example, each of the analog canceller circuits 1301 to 130 m+1 can be the same as the FIR filter 80 in FIG. 3. Each of the analog canceller circuits 1301 to 130 m+1 is configured to generate respective components of the analog correction signal, and the signal combiner 104 is configured to generate an analog correction signal in response to these components. For example, if the signal combiner 104 is an adder, the signal combiner 104 is configured to generate an analog correction signal equal to the sum of the component signals from the analog canceller circuits 1301 to 130 m+1

[0109] Similarly, the digital interference cancellation circuit 50 is configured not only to reduce transmission interference from the transmission signal generated by the transmitter circuit 401 in the received signal from the antenna 601, but also to reduce transmission interference from one or more downlink signals transmitted by one or more other antennas 60 on one or more other remote antenna units 14 (other remote antenna units not shown in FIG. 5). Therefore, the digital interference cancellation circuit 50 includes respective digital canceller circuits 1321 to 132 m for each of the sniffer receiver circuits 1221 to 122 m and the digital canceller circuit 132 m+1 ​including, for example, each digital canceller circuit 1321 - 132 m may include respective linear distortion estimator circuits 92, respective non - linear distortion estimator circuits 94, and respective signal combiners 96 arranged as shown in FIG. 3. Each digital canceller circuit 1321 - 132 m+1 is configured to generate respective components of a digital correction signal, and the signal combiner 108 is configured to generate a digital correction signal in response to the components. For example, if the signal combiner 108 is an adder, the signal combiner 108 is configured to generate a digital correction signal equal to the sum of the component signals from the digital canceller circuits 1321 - 132 m+1 Furthermore, the separation circuit controller 98 is configured to generate a control signal to the transmit - receive separation circuit 441 in response to either a component signal from the digital canceller circuits 1321 - 132 m+1 or a component signal from the signals output by each of the respective linear and non - linear distortion estimator circuits 92 and 94 of the digital canceller circuits 1321 - 132 m+1

[0110] Continuing to refer to FIG. 5, while the antenna 601 is receiving an uplink signal and each of one or more antennas 60 on one or more other nearby remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 5) is radiating its respective downlink signal, the operation of the remote antenna unit 14 may be similar to the operation described above in conjunction with FIG. 2 and may also be similar to the operation described above in conjunction with FIGS. 3 - 4, but the following operations may be added to the operations described above or one or more of the operations described above may be replaced.

[0111] The analog interference canceller circuit 46 generates an analog correction signal in response to the transmit signal generated by the transmitter circuit 401 and in response to each of one or more amplified sniffer receive signals generated by respective LNAs 124 of one or more of the sniffer receiver circuits 1221 - 122 m ​​

[0112] The digital interference cancellation circuit 50 generates a digital correction signal and a separation control signal in response to a digital time-domain signal from the signal processing circuit to the transmitter circuit 401 and in response to each of one or more digital time-domain signals generated by each of one or more of the ADCs 128 of 1221 to 122 m of the receivers.

[0113] Although not shown, in some examples, the analog interference cancellation circuit 46 includes respective sets of analog canceller circuits 130 for each of the other receiver circuits 522 to 52 n (not shown in FIG. 5), and each set of analog canceller circuits may be similar in topology and operation to the set of analog canceller circuits 1301 to 130 m+1 In other examples, the analog correction signal from the signal combiner 104 may be provided to each respective receiver circuit 52.

[0114] Similarly, although not shown, the digital interference cancellation circuit 50 includes respective sets of digital canceller circuits 132 for each of the other receiver circuits 522 to 52 n (not shown in FIG. 5), and each set of digital canceller circuits may be similar in topology and operation to the set of digital canceller circuits 1321 to 132 m+1 In other examples, the digital correction signal from the signal combiner 108 may be provided to each respective receiver circuit 52.

[0115] Although not shown, the digital interference cancellation circuit 50 includes respective separation circuit controllers 98 for each of the other transmit-receive separation circuits 442 to 44 n (not shown in FIG. 5), and each separation circuit controller is similar in topology and operation to the separation circuit controller 98 shown and described above in conjunction with FIG. 3. In other examples, the control signal from the separation circuit controller 98 may be provided to a plurality of transmit-receive separation circuits 44.

[0116] Continuing to refer to FIG. 5, in an alternative embodiment, instead of or in addition to reducing transmission interference in the received signal from antenna 601, remote antenna unit 14 includes circuitry configured to detect that while one or more of receivers 521 - 52 n are receiving a received signal, one or more of sniffers 1221 - 122 m are receiving a readout signal from respective ones of sniffing antennas 1201 - 120 m and to take measures in response to such detection. In other words, remote antenna unit 14 includes circuitry configured to detect that while at least one of antennas 601 - 60 n internal to remote antenna unit 14 is receiving an uplink signal, one or more of antennas 60 on one or more other nearby remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 5) are transmitting respective downlink signals and to take measures in response to such detection. For example, remote antenna unit 14 may be configured to notify one or more base stations 12 (FIG. 1) that remote antenna unit 14 is experiencing downlink transmission and uplink reception simultaneously, and in response to the notification, one or more base stations 12 may coordinate the transmission of downlink signals by other remote antenna units 14 with the reception of uplink signals by remote antenna units to reduce or eliminate simultaneous transmission and reception by multiple remote antenna units 14 in the same general location or “vicinity”. Or, while one or more of antennas 601 - 60 n are receiving an uplink signal, one or more of transmit - receive separation circuits 441 - 44 n each couple a respective one of receivers 521 - 52 n to respective ones of antennas 601 - 60 nBecause this latter action may cause a loss of uplink data from one or more of the user equipment 22 (FIG. 1), the remote antenna unit 14 may also be configured to notify one or more of the user equipment 22 of the decoupled uplink signals so that the one or more user equipment 22 may retransmit the blocked data to the remote antenna unit 14 (or another remote antenna unit 14).

[0117] 5, alternative embodiments of the remote antenna unit 14 are contemplated. For example, the embodiments described above in conjunction with Figures 1-4 or below in conjunction with Figures 6-19 may be applicable to the remote antenna unit 14 of Figure 5.

[0118] FIG. 6 illustrates how remote antenna unit 14 may detect a received signal generated by antenna 601 of antenna array 42 as being transmitted through one or more other antennas 602-604 on one or more other remote antenna units. n 6 is a diagram of the remote antenna unit 14 of FIG. 1 according to an embodiment configured to reduce transmission interference from the remote antenna unit 14 of FIG. 1 and from one or more other antennas on one or more other remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 6). Thus, in effect, the remote antenna unit 14 of FIG. 6 is a combination of the remote antenna units 14 of FIGS. 4 and 5. In FIG. 6, like-numbered reference items are shared with FIGS. 1-6.

[0119] In addition to transmitter circuit 401, remote antenna unit 14 includes one or more other transmitter circuits 402-404. n (Transmitter circuits 401 and 40 n 6), which are each connected to a respective antenna 602-603 of the antenna array 42. n (Antennas 601 and 60 n 6) but is otherwise similar to transmitter circuit 401.

[0120] Furthermore, in addition to the transmit-receive separation circuit 441, the remote antenna unit 14 includes one or more other transmit-receive separation circuits 442 to 44 n (only the transmit-receive separation circuits 441 and 44 n are shown in FIG. 6), each of which is coupled between one of each of the transmitter circuits 402 to 40 n and one of each of the antennas 602 to 60 n and is otherwise the same as the transmitter separation circuit 441.

[0121] Furthermore, the remote antenna unit 14 includes one or more "sniffer" antennas 1201 to 120 m and one or more corresponding "sniffer" receiver circuits 1221 to 122 m (only the sniffer antenna 1201 and the sniffer receiver circuit 1221 are shown in FIG. 6).

[0122] And, in addition to the receiver circuit 521, the remote antenna unit 14 includes one or more other receiver circuits 522 to 52 n (not shown in FIG. 6), each of which is coupled to the other antennas 602 to 60 n of the antenna array 42 and is otherwise the same as the receiver circuit 521.

[0123] The analog interference cancellation circuit 46 is configured not only to reduce transmission interference from the transmission signal generated by the transmitter circuit 401 in the received signal from the antenna 601, but also to reduce transmission interference from the downlink signals transmitted simultaneously by one or more other antennas 602 to 60 n .

[0124] Furthermore, the analog interference cancellation circuit 46 is configured to reduce transmission interference from one or more downlink signals transmitted by one or more other antennas 60 on one or more other remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 6).

[0125] Therefore, the analog interference cancellation circuit includes respective analog canceller circuits 1401 to 140 n for each of the transmitter circuits 401 to 40 m and for each of the sniffer receiver circuits 1221 to 122 n+m For example, each of the analog canceller circuits 1401 to 140 n+m may be the same as the FIR filter 80 of FIG. 3. Each of the analog canceller circuits 1401 to 140 n+m is configured to generate respective components of the analog correction signal, and the signal combiner 104 is configured to generate an analog correction signal in response to the components. For example, if the signal combiner 104 is an adder, the signal combiner 104 is configured to generate an analog correction signal equal to the sum of the component signals output from the analog canceller circuits 1401 to 140 m+n .

[0126] Similarly, the digital interference cancellation circuit 50 is configured not only to reduce transmission interference from the transmission signal generated by the transmitter circuit 401 in the received signal from the antenna 601, but also to reduce transmission interference from one or more downlink signals transmitted by one or more of the other antennas 602 to 60 n .

[0127] The digital interference cancellation circuit 50 is also configured to reduce transmission interference from one or more downlink signals transmitted by one or more of the other antennas 60 on one or more other nearby remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 6).

[0128] Therefore, the digital interference cancellation circuit 50 includes respective digital canceller circuits 1421 to 142 n for each of the transmitter circuits 401 to 40 m and for each of the sniffer receiver circuits 1221 to 122 n+m . For example, each of the digital canceller circuits 1421 to 142 n+mmay include respective linear distortion estimator circuits 92, respective non-linear distortion estimator circuits 94, and a signal combiner 96 arranged as shown in FIG. 3. Each digital canceller circuit 142 is configured to generate respective components of a digital correction signal, and the signal combiner 108 is configured to generate a digital correction signal in response to the components. For example, if the signal combiner 108 is an adder, the signal combiner 108 is configured to generate a digital correction signal equal to the sum of the component signals from the digital canceller circuits 1421 - 142 n+m and is configured to generate a digital correction signal equal to the sum of the component signals from the digital canceller circuits 1421 - 142 n+m or from any of the component signals from the linear and non-linear distortion estimator circuits 92 and 94 from each of the digital canceller circuits 1421 - 142 n+m in response to the control signal to the transmit-receive separation circuit 441.

[0129] Continuing to refer to FIG. 6, while the antenna 601 is receiving an uplink signal and while one or more of each of the transmitter circuits 401 - 40 n is generating a transmission signal, and while one or more of each of the antennas 60 on one or more other remote antenna units 14 is radiating its respective downlink signal, the operation of the remote antenna unit 14 is the same as the operation described above in conjunction with FIGS. 2 - 5 and further described below.

[0130] The analog interference cancellation circuit 46 generates an analog correction signal in response to each of one or more transmission signals generated by each of the transmitter circuits 401 - 40 n and in response to each of one or more sniffer receiver signals generated by each of the sniffer receiver circuits 1221 - 122 m .

[0131] The digital interference cancellation circuit 50, when the signal processing circuit is the transmitter circuits 401 - 40 nIn response to each of one or more digital time domain signals generated for each of those among, and the sniffer receiver circuits 1221 to 122 m of the ADCs 1281 to 128 m In response to each of one or more digital time domain signals generated by one or more of those among, generate a digital correction signal and a separation control signal.

[0132] Although not shown, in some examples, the analog interference cancellation circuit 46 includes respective sets of analog canceller circuits 140 for each of the other receiver circuits 522 to 52 n (not shown in FIG. 6), and each set of analog canceller circuits may be similar in topology and operation to the set of analog canceller circuits 1401 to 140 n+m In other examples, the analog correction signal from the signal combiner 104 may be provided to each respective receiver circuit 52.

[0133] Similarly, although not shown, in some examples, the digital interference cancellation circuit 50 includes respective sets of digital canceller circuits 142 for each of the other receiver circuits 522 to 52 n (not shown in FIG. 6), and each set of digital canceller circuits is similar in topology and operation to the set of digital canceller circuits 1421 to 142 n+m In other examples, the digital correction signal from the signal combiner 108 may be provided to each respective receiver circuit 52.

[0134] Although not shown, in some examples, the digital interference cancellation circuit 50 includes respective separation circuit controllers 98 for each of the other transmit-receive separation circuits 442 to 44 n Each separation circuit controller is shown and described in conjunction with FIG. 3 and is similar in topology and operation to the separation circuit controller 98. In other examples, the control signal from the separation circuit controller 98 may be provided to a plurality of transmit-receive separation circuits 44.

[0135] Continuing to refer to FIG. 6, in an alternative embodiment, instead of or in addition to reducing transmission interference in the received signal from antenna 601, remote antenna unit 14, while each of one or more of receiver circuits 52 is receiving the received signal, one or more of transmitter circuits 401 - 40 n each generating their respective transmission signals, and one or more of sniffer receiver circuits 1221 - 122 m each detecting that one or more of them is receiving a read signal from each of one or more of sniffer antennas 1201 - 120 m and configured to take measures in response to the detection. In other words, remote antenna unit 14, while at least one of antennas 601 - 60 n internal to remote antenna unit 14 is receiving an uplink signal, one or more of antennas 601 - 60 n each transmitting their respective downlink signals, and is configured to detect that one or more of antennas 60 on one or more other nearby remote antenna units 14 (the other remote antenna units 14 are not shown in FIG. 6) are each transmitting their respective downlink signals. For example, remote antenna unit 14 may be configured to send a notification to one or more base stations 12 (FIG. 1) that remote antenna unit 14 is experiencing downlink transmission and uplink reception simultaneously. In response to the notification, one or more base stations 12 may coordinate the downlink signal transmission by remote antenna unit 14 with the uplink signal reception by remote antenna unit 14, and the downlink signal transmission by other remote antenna units 14 with the uplink signal reception by the remote antenna unit, to reduce or eliminate simultaneous transmission and reception by remote antenna unit 14 and by multiple remote antenna units 14 in the same "vicinity". Or, remote antenna unit 14, while one or more of the antennas are receiving an uplink signal, to one or more of transmission - reception separation circuits 441 - 44 n each of one or more of antennas 601 - 60 ndemodulate each of the respective transmission signals from each of them, or to each of one or more of the transmit-receive separation circuits, antennas 601 to 60 n demodulate each of the respective receiver circuits 521 to 52 from each of them n can be demodulated. Since these latter measures can cause data loss, the remote antenna unit 14 also notifies one or more base stations 12 of the demodulated transmission signals so that one or more base stations 12 can retransmit data that has been blocked or otherwise lost for retransmission, and one or more user equipment 22 can retransmit blocked or otherwise lost data to the remote antenna unit 14 (or to another remote antenna unit 14), and is configured to notify one or more of the user equipment 22 of the demodulated uplink signals.

[0136] Continuing to refer to FIG. 6, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, each antenna 60 may be configured for use by respective operators or service providers (e.g., Verizon®, T-Mobile®, Sprint®, ATT®), which may coordinate the transmission of downlink signals with the reception of uplink signals to prevent simultaneous transmission and reception by the same antenna 60. Such coordination of transmission and reception may further improve the isolation between the transmitter circuit 40 and the receiver circuit 52 sharing the same antenna 60, and thus may allow for the omission of one or more of the transmit-receive separation circuits 44 (and the omission of one or more separation circuit controllers 98). Further, the isolation between the transmitter circuit 40 and the receiver circuit 52 may be further improved by configuring all of the antennas 60 on the remote antenna unit 14 for use by a single operator or service provider, which may coordinate the transmission of downlink signals and the reception of uplink signals such that there is no antenna transmitting a downlink signal while the same or another antenna on the remote antenna unit 14 is receiving an uplink signal. Further, the embodiments described above in conjunction with FIGS. 1-5, or below in conjunction with FIGS. 7-19, may be applicable to the remote antenna unit 14 of FIG. 6.

[0137] FIG. 7 is a diagram of a transmit-receive separation circuit 441 of FIGS. 2-6, according to one embodiment. One or more other transmit-receive separation circuits 442-44 n (FIG. 4) each may be similar to the separation circuit 441, it is understood.

[0138] The transmit-receive separation circuit 441 includes a single-pole double-throw electronic switch 150.

[0139] In the coupled state shown by the solid lines, the switch 150 is configured to couple each transmitter circuit 40 to the corresponding antenna 60 and decouple the antenna 60 from the corresponding receiver circuit 52.

[0140] In the coupled state indicated by the dashed line, switch 150 is configured to couple each antenna 60 to the corresponding receiver circuit 52 and decouple the antenna 60 from the corresponding transmitter circuit 40.

[0141] In any of the described coupled states, switch 150 is configured to reduce transmit interference in the received signal generated by antenna 60 and provided to receiver circuit 52.

[0142] During operation, the circuits built into the remote antenna unit 14 (Figs. 1 - 6) control the coupled state of switch 150. For example, as described above in conjunction with Figs. 3 - 6, in response to a command from one or more base stations 12 (Fig. 1), the circuit decouples the corresponding transmitter circuit 40 from antenna 60 and couples antenna 60 to the corresponding receiver circuit 52 while antenna 60 is receiving an uplink signal and converting the uplink signal into a received signal for receiver circuit 52. Alternatively, in response to a command from one or more base stations 12 (Fig. 1), the circuit decouples receiver circuit 52 from antenna 60 while antenna 60, or another antenna on the same or a different remote antenna unit 14, is radiating a downlink signal. Or, the separation circuit controller 98 (Figs. 3 - 6) controls the state of switch 150 in response to one or more signals generated by the digital interference cancellation circuit 50 (Figs. 2 - 6).

[0143] Continuing to refer to Fig. 7, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, the embodiments described above in conjunction with Figs. 1 - 6, or below in conjunction with Figs. 8 - 19, may be applicable to the transmit - receive separation circuit 44 of Fig. 7.

[0144] Fig. 8 is a diagram of the transmit - receive separation circuit 441 of Figs. 2 - 6 according to one embodiment. It is understood that each of one or more of the other transmit - receive separation circuits 442 - 44 n (Fig. 4) may be similar to separation circuit 441.

[0145] The transmit-receive separation circuit 441 is configured to couple the transmission signal from the transmitter circuit 401 (Figs. 2-6) to the antenna 601 (Figs. 2-6) and at the same time couple the received signal from the same antenna 601 to the receiver circuit 521 (Figs. 2-6) while electrically insulating the receiver circuit 521 from the transmitter circuit 401. That is, the transmit-receive separation circuit 441 enables the antenna 601 to radiate a downlink signal and at the same time receive an uplink signal while reducing the interference in the received signal caused by the transmission signal to a suitable level. In other words, the transmit-receive separation circuit 441 is configured to electrically insulate the receiver circuit 521 from the corresponding transmitter circuit 401 while the transmitter circuit 401 provides a transmission signal to the antenna 601 and at the same time the receiver circuit 521 receives a received signal from the antenna 601. For example, such a level of insulation configured to be provided by the transmit-receive separation circuit 441 can be approximately 20 dB or more.

[0146] As described below, the transmit-receive separation circuit 401 is configured to provide such electrical insulation by dividing the transmission signal into a plurality of components, interfering the components to reinforce each other at the antenna 601, and interfering any leakage components of the transmission signal to weaken each other at the receiver circuit 521 such that the transmission signal power is not coupled to the receiver circuit 521 ideally.

[0147] The transmit-receive separation circuit 441 includes a transmitter port 160, an antenna port 162, a receiver port 164, a first phase shift coupler 166, a transmitter end impedance or load 168, a first circulator 170, a second circulator 172, a second phase shift coupler 174, an antenna end impedance or load 176, a third phase shift coupler 178, and a receiver end impedance or load 180.

[0148] The transmitter port 160 is configured to be coupled to a transmitter circuit 401 (Figs. 2-6), the antenna port 162 is configured to be coupled to an antenna 601 (Figs. 2-6), and the receiver port 164 is configured to be coupled to a receiver circuit 521 (Figs. 2-6).

[0149] The first phase shift coupler 166 includes a first path 182 configured to shift the phase of a first component of a transmission signal input to the transmitter port 160 by a first amount (e.g., -90°), a second path 184 configured to shift the phase of a second component of the transmission signal by a second amount (e.g., 0°), and a terminal port 186 configured to be coupled to a transmitter termination load 168, which can be any suitable resistive, reactive, or complex impedance circuit or device. Further, the first and second paths 182 and 184 each generate a first and a second component of the transmission signal, respectively, having approximately the same power level.

[0150] The first circulator 170 can be a conventional passive circulator and has a first circulator port 188 coupled to the first path 182 of the first phase shift coupler 166, a second circulator port 190, and a third circulator port 192.

[0151] The second circulator 172 can be a conventional passive circulator or, otherwise, can be similar to the first circulator 170 and has a first circulator port 194 coupled to the second path 184 of the first phase shift coupler 166, a second circulator port 196, and a third circulator port 198.

[0152] For the purpose of explaining the structure and operation of the first and second circulators 170 and 172, it is assumed that, in the following operation description, the first and second circulators 170 and 172 are given the same attenuation and the same phase shift so that the attenuation and phase shift imparted by the first and second circulators 170 and 172 are ignored. One way to at least approximately realize this assumption is to electrically match the first and second circulators 170 and 172, for example, by forming the circulators 170 and 172 on the same integrated circuit die.

[0153] The second phase shift coupler 174 includes a first path 200 configured to shift the phase of a first secondary component of a first component of a transmission signal received from the circulator port 190 by a first amount (e.g., -90°), a second path 202 configured to shift the phase of a second secondary component of the first component of the transmission signal by a second amount (e.g., 0°), and a terminal port 204 configured to couple the first path 200 to an antenna terminal load 176, which can be any suitable resistive, reactive, or complex impedance circuit or device. For example, the first and second paths 200 and 202 are configured to generate the first and second secondary components of the first component of the transmission signal such that the first secondary component with respect to the load 176 has little or no power, if any, and the second secondary component with respect to the antenna port 162 has most, but not all, of the power of the first component of the transmission signal.

[0154] The second phase shift coupler 174 is coupled to the second circulator port 196 of the second circulator 172 and is configured to shift the phase of the first secondary component of the second component of the transmission signal by a third amount (e.g., 0°), and further includes a third path 206 and a fourth path 208 configured to shift the phase of the second secondary component of the second component of the transmission signal by a fourth amount (e.g., -90°). For example, the third and fourth paths 206 and 208 are configured to generate the first and second secondary components of the second component of the transmission signal such that the first secondary component with respect to the load 176 has little power, if any, and the second secondary component with respect to the antenna port 162 has most, but not all, of the power of the second component of the transmission signal.

[0155] Furthermore, the second path 202 of the second phase shift coupler 174 is also configured to shift the phase of the first component of the received signal from the antenna port 162 by a second amount (e.g., 0°), and the fourth path 208 is configured to shift the phase of the second component of the received signal from the antenna port by a fourth amount (e.g., -90°). Further, the second and fourth paths 202 and 208 are configured to generate each of the first and second components of the received signal having approximately the same power level.

[0156] The third phase shift coupler 178 is coupled to the third circulator port 192 of the first circulator 170 and is configured to shift the phase of the first secondary component of the first component of the received signal by a first amount (e.g., -90°), a first path 210, a second amount (e.g., 0°) is configured to shift the phase of the second secondary component of the first component of the received signal, a second path 212, and a terminal port 214 configured to couple the second path 212 to a receive termination load 180, which can be any suitable resistor, reactance, or complex impedance circuit or device. Further, the first and second paths 210 and 212 are configured to generate the first and second secondary components of the first component of the received signal such that the first secondary component with respect to the load 180 has little, if any, power and the second secondary component with respect to the receiver port 164 has most, but not all, of the power of the first component of the received signal.

[0157] The third phase shift coupler 178 is further coupled to the third circulator port 198 of the second circulator 172 and is configured to shift the phase of the first secondary component of the second component of the received signal by a third amount (e.g., 0°), a third path 216, a fourth amount (e.g., -90°) is configured to shift the phase of the second secondary component of the second component of the received signal, a fourth path 218. Further, the third and fourth paths 216 and 218 are configured to generate the first and second secondary components of the second component of the received signal such that the first secondary component with respect to the load 180 has little, if any, power and the second secondary component with respect to the receiver port 164 has most, but not all, of the power of the second component of the received signal.

[0158] Ideally, there is no leakage of the first component of the transmitted signal from the third circulator port 192 of the first circulator 170 and no leakage of the second component of the transmitted signal from the third circulator port 198 of the second circulator 172.

[0159] However, in reality, there may be such a leakage.

[0160] Therefore, the first path 210 of the third phase shift coupler 178 is configured to shift the phase of the leakage secondary component of the first component of the transmission signal by a first amount (e.g., -90°), and the third path 216 is configured to shift the phase of the leakage secondary component of the second component of the transmission signal by a third amount (e.g., 0°).

[0161] Continuing to refer to FIG. 8, the operation of the transmit-receive separation circuit 441 according to an embodiment is described in which any leakage secondary components of the transmission signal interfere with each other at the receiver port 164 to reduce the interference caused by the simultaneous transmission signal to the antenna 601 in the received signal. Further, in the following description, any losses imparted by the first, second, and third phase shift couplers 166, 174, and 178, and the first and second circulators 170 and 172 are ignored, any energy coupled by the first, second, and third phase shift couplers 166, 174, and 178 to the termination loads 168, 176, and 180 respectively is ignored, any phase shifts imparted by the circulators 170 and 172 to the signals propagating within the circulators are ignored, the phase shift couplers 166, 174, and 178 are assumed to impart only the phase shifts they are configured to impart to the signals, the paths within the phase shift couplers 166, 174, and 178 are assumed to divide the signal input to a plurality of the paths into signal components having equal power, and any received signal energy propagating from the antenna port 162 to the transmitter port 160 is ignored.

[0162] The transmission signal of power T from the transmitter circuit 401 (FIGS. 2 - 6) propagates into the transmitter port 160 and to the first phase shift coupler 166.

[0163] The first component of the transmission signal having power T / 2 propagates along the first path 182 of the first phase shift coupler 166 that shifts the phase of the first component by an amount such as -90°, and the second component of the transmission signal having power T / 2 propagates along the second path 184 that shifts the phase of the second component by an amount such as 0°.

[0164] The first component of the transmission signal propagates from the first path 182 of the first phase shift coupler 166 to the first circulator port 188 of the first circulator 170, propagates from the first circulator port 188 to the second circulator port 190 of the first circulator 170, and propagates from the second circulator port 190 to the second path 202 of the second phase shift coupler 174.

[0165] The second component of the transmission signal propagates from the second path 184 of the first phase shift coupler 166 to the first circulator port 194 of the second circulator 172, propagates from the first circulator port 194 to the second circulator port 196 of the second circulator 172, and propagates from the second circulator port 196 to the third path 206 of the second phase shift coupler 174.

[0166] The second path 202 of the second phase shift coupler 174 couples the first secondary component of the first component of the transmission signal to the antenna port 162 with a phase shift such as 0°, and the fourth path 208 of the second phase shift coupler 174 couples the second secondary component of the second component of the transmission signal to the antenna port 162 with a phase shift such as -90°. Since the first path 200 and the third path 206 of the second phase shift coupler 174 each couple approximately zero energy to the termination load 176, the first secondary component of the first component of the transmission signal and the second secondary component of the second component of the transmission signal each have approximately signal power of T / 2.

[0167] Since both the first secondary component of the first component of the transmission signal and the second secondary component of the second component of the transmission signal have approximately the same phase (e.g., -90°) at the antenna port 162, these first and second secondary components are added so as to reinforce each other so as to "reconstruct" a transmission signal having approximately the complete transmission signal power T at the antenna port 162.

[0168] In the manner described above, the first phase shift coupler 166, the first and second circulators 170 and 172, and the second phase shift coupler 174 effectively provide the antenna 601 (Figs. 2 to 6) with a reconstructed transmission signal having approximately the same power T as the transmission signal at the transmitter port 160. That is, the transmit-receive separation circuit 441 couples the transmission signal from the transmitter port 160 to the antenna port 162 with relatively low signal loss.

[0169] Ideally, the first circulator 170 does not couple any portion of the first component of the transmission signal from the first circulator port 188 to the third circulator port 192.

[0170] However, in actual operation, the first circulator 170 may couple a leakage secondary component of the first component of the transmission signal from the first circulator port 188 to the third circulator port 192.

[0171] The first path 210 of the third phase shift coupler 178 couples the leakage secondary component of the first component of the transmission signal to the receiver port 164 with a total phase shift such as -180° (e.g., -90° from the first phase shift coupler 166 and -90° from the third phase shift coupler 178).

[0172] Also ideally, the second circulator 172 does not couple any portion of the second component of the transmission signal from the first circulator port 194 to the third circulator port 198.

[0173] However, in actual operation, the second circulator 172 may couple the leakage secondary component of the second component of the transmission signal from the first circulator port 194 to the third circulator port 198.

[0174] The third path 216 of the third phase shift coupler 178 couples the leakage secondary component of the second component of the transmission signal to the receiver port 164 with a total phase shift such as 0° (e.g., 0° from the first phase shift coupler 166 and 0° from the third phase shift coupler 178).

[0175] As a result, since the leakage secondary components of the first and second components of the transmission signal have approximately opposite phases (e.g., 0° and 180°) at the receiver port 164, the leakage components interfere with each other in a way that at least ideally, any leakage energy from the transmission signal is not coupled to the receiver circuit 521 (Figs. 2 - 6) via the receiver port 164.

[0176] Furthermore, in the operation of the transmit - receive separation circuit 441, ideally, the second phase shift coupler 174 receives an input received signal having power R from the antenna 601 (Figs. 2 - 6) at the receiver port 162.

[0177] The second path 202 of the second phase shift coupler 174 shifts the phase of the first component of the received signal having power R / 2 by an amount such as 0°, and the fourth path 208 of the second phase shift coupler 174 shifts the phase of the second component of the received signal having approximately R / 2 power by an amount such as - 90°.

[0178] The first component of the received signal propagates from the second path 202 of the second phase shift coupler 174 to the second circulator port 190 of the first circulator 170, and the second component of the received signal propagates from the fourth path 208 of the second phase shift coupler 174 to the second circulator port 196 of the second circulator 172.

[0179] The first component of the received signal propagates from the second circulator port 190 to the third circulator port 192 of the first circulator 170 and from the third circulator port 192 to the first path 210 of the third phase shift coupler 178. The first path 210 of the third phase shift coupler 178 imparts a phase shift of an amount such as -90° to the first component of the received signal at the receiver port 164 so that the first component of the received signal has a total phase shift such as -90° (e.g., 0° from the second phase shift coupler 174 and -90° from the third phase shift coupler 178).

[0180] The second component of the received signal propagates from the second circulator port 196 to the third circulator port 198 of the second circulator 172 and from the third circulator port 198 to the third path 216 of the third phase shift coupler 178. The third path 216 imparts a phase shift of an amount such as -90° to the second component of the received signal at the receiver port 164 so that the second component of the received signal has a total phase shift such as -90° (e.g., -90° from the second phase shift coupler 174 and 0° from the third phase shift coupler 178).

[0181] As a result, both the first and second components of the received input signal have approximately the same phase (e.g., -90°) at the receiver port 164, so they interfere constructively and thus effectively reconstruct a received signal having approximately the total power R at the receiver port.

[0182] In summary, the transmit-receive separation circuit 441 effectively splits the transmit signal at the transmitter port 160 into a plurality of components that interfere constructively at the antenna port 162 so that the antenna 601 radiates the reconstructed transmit signal of approximately the total power and interfere destructively at the receiver port 164 to reduce the interference caused by the simultaneous transmit signal to the same antenna 601 in the received signal.

[0183] Continuing to refer to FIG. 8, an alternative embodiment of the transmit-receive separation circuit 441 is contemplated. For example, in practice, the separation circuit 441, although it may not be ideal, can still couple the transmission signal from the transmitter circuit 401 (FIGS. 2-6) to the antenna 601 with a suitable level of attenuation and other distortions, and reduce the interference in the received signal caused by the transmission signal to the receiver circuit 521 to a suitable level. Further, the embodiments described above in conjunction with FIGS. 1-7 or below in conjunction with FIGS. 9-19 may be applicable to the transmit-receive separation circuit 441 of FIG. 8.

[0184] FIG. 9 is a graph 230 of the frequency response 232 of each of the circulators 170 and 172 in FIG. 8 from the first circulator ports 188, 194 to the second circulator ports 190, 196 according to one embodiment. According to the frequency response 232, when the signal propagates from the first circulator ports 188, 194 to the second circulator ports 190, 196, the transmission insertion loss exhibited by the signal in the frequency band of 3.4 GHz to 3.8 GHz is less than 1 dB.

[0185] FIG. 10 is a graph 240 of the frequency response 242 of each of the circulators 170 and 172 in FIG. 8 from the second circulator ports 190, 196 to the third circulator ports 192, 198 according to one embodiment. According to the frequency response 242, when the signal propagates from the second circulator ports 190, 196 to the third circulator ports 192, 198, the reception insertion loss exhibited by the signal in the frequency band of 3.4 GHz to 3.8 GHz is less than 1 dB.

[0186] FIG. 11 is a graph 250 of the frequency response 252 of each of the circulators 170 and 172 in FIG. 8 from the first circulator ports 188, 194 to the third circulator ports 192, 198 according to one embodiment. According to the frequency response 252, in the frequency band of 3.4 GHz to 3.8 GHz, the isolation from the first circulator ports 188, 194 to the third circulator ports 192, 198 is in the range of more than 30 dB to more than 50 dB.

[0187] FIG. 12 is a graph 260 comparing the frequency responses 262 of each of the circulators 170 and 172 in FIG. 8 from the first circulator ports 188, 194 to the second circulator ports 190, 196, the frequency response 264 of the transmit-receive separation circuit 441 in FIG. 8 from the transmitter port 160 to the antenna port 162, and the frequency responses 266 of each of the circulators from the first circulator ports 188, 194 to the third circulator ports 192, 198 compared to the frequency response 268 of the transmit-receive separation circuit 441 in FIG. 8 from the transmitter port 160 to the receiver port 164, according to one embodiment. According to the frequency responses 262, 264, 266, and 268, in the frequency band of 3.4 GHz to 3.8 GHz, the transmit-receive separation circuit 441 has approximately the same transmit insertion loss (less than 1 dB) between the transmitter port 160 and the antenna port 162 as would be had by the circulators 170, 172, but provides a level of isolation (greater than 30 dB) that is significantly higher than that which would be provided by the circulators (25 dB or less) between the transmitter port 160 and the receiver port 164.

[0188] FIG. 13 is a diagram of the transmit-receive separation circuit 441 of FIGS. 2-6, according to another embodiment. It is understood that one or more of each of the other transmit-receive separation circuits 442-44 n (FIG. 4) can be similar to the separation circuit 44i of FIG. 13. Further, items common to FIGS. 8 and 13 are labeled with the same reference numerals.

[0189] The transmit-receive separation circuit 441 of FIG. 13 is similar to the transmit-receive separation circuit 441 of FIG. 8, but the addition of two adjustable phase couplers 280 and 282 enables effective pre-execution, execution, or dynamic adjustment of the phase shifts imparted by the first, second, and third phase shift couplers 166, 174, and 178. Such phase adjustment can improve the level of electrical isolation provided by the transmit-receive separation circuit 441 between the transmitter circuit 401 (FIGS. 2-6) and the receiver circuit 521 (FIGS. 2-6).

[0190] The adjustable phase coupler 280 includes a phase shifter 284, which may be similar to the phase shifters 166, 174, and 178, a phase regulator 286 including two electronically adjustable capacitors such as varactors 288 and 290, and at least one control line 292. The phase shifter 284 includes first, second, third, and fourth phase shift signal paths 294, 296, 298, and 300, an input node 302, and an output node 304. Further, the adjustable phase coupler 280 may include a single control line 292 shared by the capacitors 288 and 290, two control lines 292 that are one control line for each of the capacitors 288 and 290, or more than two control lines having one or more control lines for each of the capacitors 288 and 290. Further, at least one control line may be coupled to any other circuit on the respective isolation circuit controller 98 (Figs. 2-6), the control circuit 48 (Figs. 2-6), or the remote antenna unit 14 (Figs. 2-6).

[0191] The operation of the adjustable phase coupler 280 is described according to an embodiment in which the capacitances of the capacitors 288 and 290, and thus one or more phase shifts imparted by the adjustable phase coupler 280, are controlled by one or more signals from the corresponding isolation circuit controller 98 (Figs. 2-6). Further, for the purposes of the following description, it is assumed that the adjustable phase coupler 280 divides the signal at the input node 302 into two signal components of approximately equal power that propagate along the first and second paths 294 and 296, respectively, and that any losses introduced by the adjustable phase coupler are ignored.

[0192] An input signal enters the input node 302, and a first component of the input signal having power P / 2 propagates along a path 294 that imparts a phase shift, such as -90°, to the first component.

[0193] The capacitor 288 imparts a second phase shift to the first component of the input signal that has been phase-shifted once, and the magnitude of the second phase shift is controlled by a signal from the separation circuit controller 98 (Figs. 2 - 6). For example, the second phase shift can be within an approximate range of a ratio up to about 10°.

[0194] The capacitor 288 effectively redirects the first component of the input signal that has been phase-shifted twice to a third path 298 that imparts a third phase shift, such as 0°, to the first component so that the first component that has been phase-shifted three times is at the output node 304.

[0195] Similarly, the second component of the input signal having approximately P / 2 power propagates along a second path 296 that imparts a phase shift, such as 0°, to the second component of the input signal.

[0196] The capacitor 290 imparts a second phase shift to the second component of the input signal that has been phase-shifted once, and the magnitude of the second phase shift is controlled by a signal from the separation circuit controller 98 (Figs. 2 - 6). For example, the second phase shift can be within an approximate range of a ratio up to about 10°.

[0197] The capacitor 290 effectively redirects the second component of the input signal that has been phase-shifted twice to a fourth path 300 that imparts a third phase shift, such as -90°, to the second component so that the second component that has been phase-shifted three times is at the output node 304.

[0198] Assuming a matching operation where the total phase shift imparted to the first component of the input signal by the first path 294, the first capacitor 288, and the third path 298 is equal to the total phase shift imparted to the second component of the input signal by the second path 296, the second capacitor 290, and the third path 300, at the output node 304, the first and second components of the input signal interfere constructively to generate a phase-shifted version of the input signal having approximately power P.

[0199] The phase shift imparted by capacitor 288 to the first component of the input signal can be the same as the phase shift imparted by capacitor 290 to the second component of the input signal, but it does not have to be. For example, in a non-matching operation where the total phase shift imparted by the first and third paths 294 and 298 to the first component of the input signal is -92°, and the total phase shift imparted by the second and fourth paths 296 and 300 to the second component of the input signal is -89°, then capacitor 288 can be controlled to impart a phase shift that is offset by +3° with respect to the phase shift imparted by capacitor 290 such that the first and second components of the input signal have the same phase at output node 304.

[0200] The adjustable phase coupler 282 can have a structure, configuration, and operation similar to the structure, configuration, and operation of the adjustable phase coupler 280.

[0201] Continuing to refer to FIG. 13, the operation of the transmit-receive separation circuit 441 according to an embodiment is described in which any leaked secondary components of the transmit signal interfere with each other to weaken at the receiver port 164, thereby reducing the interference caused by the simultaneous transmit signal in the received signal. Further, in the following description, any losses imparted by the phase shift couplers 166, 174, and 178, the adjustable phase couplers 280 and 282, and the circulators 170 and 172 are ignored, any phase shifts imparted to the signals propagating within the circulators are ignored, any signal energy coupled by the phase shift couplers 166, 174, and 178 to the terminating loads 168, 176, and 180 respectively is ignored, the paths within the couplers are assumed to divide the signals supplied to a plurality of the paths into signal components having equal power, and any signal energy propagating from the antenna port 162 to the transmitter port 160 is ignored.

[0202] The transmit signal of power T from the transmitter circuit 401 (FIGS. 2-6) propagates to the transmitter port 160 of the first phase shift coupler 166.

[0203] The first component of the transmission signal having power T / 2 propagates along a first path 182 that shifts the phase of the first component by an amount such as -90°, and the second component of the transmission signal having power T / 2 propagates along a second path 184 that shifts the phase of the second component by an amount such as 0°.

[0204] The first component of the transmission signal propagates from the first path 182 of the first phase shifter 166 to the first circulator port 188 of the first circulator 170, propagates from the first circulator port 188 to the second circulator port 190 of the first circulator 170, and propagates from the second circulator port 190 to the second path 202 of the second phase shifter 174.

[0205] The second component of the transmission signal propagates from the second path 184 of the first phase shifter 166 to the first circulator port 194 of the second circulator 172, propagates from the first circulator port 194 to the second circulator port 196 of the second circulator 172, and propagates from the second circulator port 196 of the second circulator 172 to the third path 206 of the second phase shifter 174.

[0206] The second path 202 of the second phase shifter 174 couples the first secondary component of the first component of the transmission signal to the antenna port 162 with a phase shift such as 0°, and the fourth path 208 of the second phase shifter 174 couples the second secondary component of the second component of the transmission signal to the antenna port 162 with a phase shift such as -90°. Since the first path 200 and the third path 206 of the second phase shifter 174 each couple approximately zero energy to the termination load 176, the first secondary component of the first component of the transmission signal and the second secondary component of the second component of the transmission signal each have approximately signal power of T / 2.

[0207] Since both the first secondary component of the first component of the transmission signal and the second secondary component of the second component of the transmission signal have approximately the same phase (e.g., -90°) at the antenna port 162, these first and second secondary components are added so as to reinforce each other to "reconstruct" a transmission signal having approximately the full transmission signal power T at the antenna port 162.

[0208] In the manner described above, the first phase shift coupler 166, the first and second circulators 170 and 172, and the second phase shift coupler 174 effectively provide the antenna 601 (Figs. 2 - 6) with a reconstructed transmission signal having approximately the same power T as the transmission signal at the transmitter port 160. That is, the transmit-receive separation circuit 441 effectively couples the transmission signal from the transmitter port 160 to the antenna port 162 with a relatively low insertion loss.

[0209] Ideally, the first circulator 170 does not couple any portion of the first component of the transmission signal from the first circulator port 188 to the third circulator port 192.

[0210] However, in actual operation, the first circulator 170 may couple a leakage secondary component of the first component of the transmission signal from the first circulator port 188 to the third circulator port 192.

[0211] The adjustable phase coupler 280 operating as described above shifts the phase of the leakage secondary component of the first component of the transmission signal from the circulator port 192 of the first circulator 170 by an amount such as -90° + θ cap1 which is the phase shift imparted to the leakage secondary component of the first component of the transmission signal by one or more control signals on one or more control lines 292 to the capacitors 288 and 290 (θ cap1(which can be positive or negative). For example, the isolation circuit controller 98 (Figs. 2 - 6) can generate one or more control signals as part of a feedback control loop that acts to dynamically reduce the amount of interference caused by the transmission signal input to the transmitter port 160 at the reception signal output at the receiver port 164.

[0212] The first path 210 of the third phase - shift coupler 178 couples the once - phase - shifted leakage secondary component of the first component of the transmission signal, with a total phase shift such as - 270°+θ cap1 (- 90° from the first phase - shift coupler 166, - 90°+θ from the adjustable phase coupler 280 cap1 and - 90° from the third phase - shift coupler 178), to the receiver port 164.

[0213] Ideally, the second circulator 172 also does not couple any portion of the second component of the transmission signal from the first circulator port 194 to the third circulator port 198.

[0214] However, in actual operation, the second circulator 172 may couple the leakage secondary component of the second component of the transmission signal from the first circulator port 194 to the third circulator port 198.

[0215] The adjustable phase coupler 282, which operates as described above with respect to the adjustable phase coupler 280, shifts the phase of the leakage secondary component of the second component of the transmission signal from the third circulator port 198 of the second circulator 172 by an amount such as - 90°+θ cap2 which is the phase shift imparted by one or more control signals on one or more control lines 310 to the capacitors 312 and 314 for the leakage secondary component of the first component of the transmission signal (θ cap2(which can be positive or negative). For example, the isolation circuit controller 98 (Figs. 2 - 6) can generate one or more control signals as part of a feedback control loop that acts to reduce the amount of interference caused by the transmission signal input to the transmitter port 160 at the reception signal output from the receiver port 164.

[0216] The third path 216 of the third phase - shift coupler 178 couples the once - phase - shifted leakage secondary component of the second component of the transmission signal to the receiver port 164 with a total phase shift such as (0° from the first phase - shift coupler 166, - 90°+θ from the adjustable phase coupler 282, cap2 and 0° from the third phase - shift coupler 178). cap2 As a result, in the formula, θ

[0217] = θ cap1 or θ is used to compensate for the phase difference of the path through which the leakage secondary component propagates. cap2 Unlike when θ cap1 is θ cap2 since the secondary components of the first and second components of the transmission signal have approximately opposite phases (e.g., - 90° and - 270°) at the receiver port 164, the leakage components interfere with each other to weaken each other so that at least ideally, any leakage energy from the transmission signal is not coupled to the receiver circuit 521 (Figs. 2 - 6) through the receiver port 164. Further, the control loop described above acts to dynamically vary θ cap1 and θ cap2 to maintain the transmission signal leakage energy at the receiver port 164 at the lowest achievable level.

[0218] Further, in the operation of the transmit - receive isolation circuit 441, ideally, the second phase - shift coupler 174 receives an input reception signal having power R from the antenna 601 (Figs. 2 - 6) at the receiver port 162.

[0219] The second path 202 of the second phase shifter coupler 174 shifts the phase of the first component of the received signal having power R / 2 by an amount such as 0°, and the fourth path 208 of the second phase shifter coupler 174 shifts the phase of the second component of the received signal having power approximately R / 2 by an amount such as -90°.

[0220] The first component of the received signal propagates from the second path 202 of the second phase shifter coupler 174 to the second circulator port 190 of the first circulator 170, and the second component of the received signal propagates from the fourth path 208 of the second phase shifter coupler 174 to the second circulator port 196 of the second circulator 172.

[0221] The first component of the received signal propagates from the second circulator port 190 to the third circulator port 192 of the first circulator 170 and from the third circulator port 192 to the adjustable phase coupler 280.

[0222] The adjustable phase coupler 280 operating as described above shifts the phase of the first component of the received signal by an amount such as -90° + θ cap1 which is the phase shift imparted to the first component of the received signal by one or more control signals on one or more control lines 292 to the capacitors 288 and 290 (θ cap1 can be positive or negative).

[0223] The first path 210 of the third phase shifter coupler 178 imparts a phase shift of an amount such as -90° to the twice-phase-shifted first component of the received signal such that at the receiver port 164, the first component of the received signal has a total phase shift of -180° + θ cap1 (0° from the second phase shifter coupler 174, -90° + θ cap1 from the adjustable phase coupler 280, and -90° from the third phase shifter coupler 178).

[0224] The second component of the received signal propagates from the second circulator port 196 to the third circulator port 198 of the second circulator 172 and from the third circulator port 198 to the adjustable phase coupler 282.

[0225] The adjustable phase coupler 282 operating as described above shifts the phase of the second component of the received signal by an amount such as -90° + θ cap2 which is the phase shift imparted to capacitors 312 and 314 by one or more control signals on one or more control lines 310, to the second component of the received signal (θ cap2 can be positive or negative).

[0226] The third path 216 of the third phase shift coupler 178 imparts a phase shift of an amount such as -90° to the twice-phase-shifted second component of the received signal at the receiver port 164 so that the second component of the received signal has a total phase shift of -180° + θ cap2 (-90° from the second phase shift coupler 174, -90° + θ cap2 from the adjustable phase coupler 282, and 0° from the third phase shift coupler 178).

[0227] As a result, both the first and second components of the received input signal have approximately the same phase (e.g., -180°) at the receiver port 164, so they interfere constructively and thus effectively reconstruct a received signal having approximately the total power R at the receiver port. This is the case when θ cap1 = θ cap2 or assuming that θ cap1 and θ cap2 are such that they equalize the total phase shift experienced by the first and second components of the received signal.

[0228] In summary, the transmit-receive separation circuit 441 effectively splits the transmit signal at the transmitter port 160 into a plurality of components that interfere with each other at the antenna port 162 to cause the antenna 601 to radiate the reconstructed transmit signal of approximately all the power, and interfere with each other at the receiver port 164 to reduce the interference caused by the simultaneous transmit signal to the same antenna 601 in the received signal from the antenna 601.

[0229] Continuing to refer to FIG. 13, an alternative embodiment of the transmit-receive separation circuit 441 is contemplated. For example, since the components of the transmit and receive signals traverse different paths, the values of θ cap1 and θ cap2 that are optimal for transmit interference cancellation may not be optimal for reconstructing the received signal at the receiver port 164, and vice versa. Therefore, the separation circuit controller 98 (FIGS. 2-6), and one or more control loops including the separation circuit controller 98, may be weighted to prioritize cancellation of transmit interference over reconstruction of the received signal, or vice versa. Further, instead of being controlled by the separation circuit controller 98, the adjustable phase couplers 280 and 282 may have their phase shifts set to fixed values during the manufacture or assembly of the remote antenna unit 14 (FIGS. 2-6), or set to values calibrated during a calibration procedure performed once or periodically. Further, the embodiments described above in conjunction with FIGS. 1-12, or below in conjunction with FIGS. 14-19, may be applicable to the transmit-receive separation circuit 441 of FIG. 13.

[0230] FIG. 14 is a graph 330 of the frequency responses 332 between the transmitter port 160 and the antenna port 162, the frequency response 334 between the antenna port 162 and the receiver port 164, and the frequency response 336 between the transmitter port 160 and the receiver port 164 of the transmit-receive separation circuit 441 of FIG. 13 according to one embodiment. According to the frequency responses 332, 334, and 336, in the frequency band of 3.4 GHz to 3.8 GHz, the transmit-receive separation circuit 441 has a relatively low (e.g., about 0.5 dB to 1.0 dB) transmit insertion loss between the transmitter port and the antenna ports 160 and 162, as well as a relatively low receive insertion loss between the antenna port and the receiver ports 162 and 164, but provides a relatively high level (e.g., about 38 dB or more) of electrical isolation between the transmitter port and the receiver port.

[0231] FIG. 15 is a graph 340 comparing the frequency response 344 of the transmit-receive separation circuit 441 of FIG. 13 from the transmitter port 160 to the antenna port 162 with the frequency responses 342 of each of the circulators 170 and 172 of FIG. 13 from the first circulator ports 188, 194 to the second circulator ports 190, 196, and comparing the frequency response 348 of the transmit-receive separation circuit 441 of FIG. 13 from the transmitter port 160 to the receiver port 164 with the frequency responses 346 of each of the circulators 170 and 172 of FIG. 13 from the first circulator ports 188, 194 to the third circulator ports 192, 198 according to one embodiment. According to the frequency responses 342, 344, 346, and 348, in the frequency band of 3.4 GHz to 3.8 GHz, the transmit-receive separation circuit 441 of FIG. 13 has approximately the same transmit insertion loss (e.g., less than 1 dB) as the circulators 170, 172 would have, but provides a significantly higher level of isolation (e.g., over 38 dB) than the circulator (e.g., 25 dB or less) would provide between the transmitter port 160 and the receiver port 164.

[0232] FIG. 16 is a diagram of the transmit-receive separation circuit 441 of FIGS. 2 to 6 according to yet another embodiment. Other transmit-receive separation circuits 442 to 44 nIt is understood that one or more of them may be the same as the transmit-receive separation circuit 441.

[0233] The separation circuit 441 includes a transmitter port 360, an antenna port 362, a receiver port 364, a circulator 366, a balun 368, a filter circuit 370, a signal combiner 372, and a received signal strength indicator (RSSI) circuit 374.

[0234] The transmitter port 360 is configured to be coupled to the transmitter circuit 401 (Figs. 2 - 6), the antenna port 362 is configured to be coupled to the antenna 601 (Figs. 2 - 6), and the receiver port 364 is configured to be coupled to the receiver circuit 521 (Figs. 2 - 6).

[0235] The circulator 366 may be the same as the circulators 170 and 172 in Figs. 8 and 13.

[0236] The balun 368 may be a conventional balun and is configured to generate a reference signal in response to a transmission signal at the transmitter port 360. For example, the reference signal can be a low - power replica of the transmission signal.

[0237] The filter circuit 370 is, for example, a FIR filter, and one or more of its coefficients are controllable by the RSSI circuit 374. The filter circuit 370 may be an analog or digital filter circuit (in the latter case, the filter circuit 370 may include an ADC for converting the reference signal from the analog to the digital domain and a DAC for converting the filtered reference signal from the digital domain to the analog domain).

[0238] The signal combiner 372 is configured to combine the filtered reference signal with the received signal from the antenna 601 (Figs. 2 - 6) via the circulator 366 to generate a received signal with transmission interference canceled at the receiver port 364. For example, the signal combiner 372 may be an adder circuit.

[0239] The RSSI circuit 374 determines the strength of the received signal from which transmission interference has been canceled, and is configured to control parameters of a filtering algorithm for the filter circuit 370 to filter the reference signal in response to the determined strength. For example, as described above, the RSSI circuit 374 is configured to control one or more coefficients of the FIR filter implemented by the filter circuit 370.

[0240] Continuing to refer to FIG. 16, the operation of the transmit-receive separation circuit 441 according to one embodiment will be described.

[0241] The transmitter circuit 401 (FIGS. 2 to 6) generates a transmission signal that propagates to the antenna 601 (FIGS. 2 to 6) that radiates a downlink signal in response to the transmission signal at the transmitter port 360, through the balun 368, to the circulator port 376 of the circulator 366, and through the circulator 366, to another circulator port 378.

[0242] The balun 368 generates a reference signal in response to the transmission signal, and the filter circuit 370 filters the reference signal using an algorithm having one or more coefficients or one or more other parameters set by the feedback signal from the RSSI circuit 374.

[0243] While radiating the downlink signal, the antenna 601 (FIGS. 2 to 6) receives an uplink signal and generates a received signal at the circulator port 378 of the circulator 366 in response to the uplink signal.

[0244] The received signal propagates from the circulator port 378 to the circulator port 380 of the circulator 366.

[0245] Since the circulator 366 is non-ideal, components of the transmission signal leak into, for example, interfere with, the received signal.

[0246] Therefore, at the circulator port 380, the received signal includes transmitted signal interference that distorts the received signal.

[0247] The distorted received signal propagates from the circulator port 380 to the signal combiner 372, and combines with the filtered reference signal to obtain an undistorted (e.g., interference-canceled) received signal at the receiver port 364. The undistorted received signal may still include some transmitted interference, but the transmit-receive separation circuit 441 reduces the transmitted interference in the received signal to a level lower than the level of the transmitted interference of the received signal at the circulator port 380.

[0248] The transmit-receive separation circuit 441 operates on the principle that adjusting the distorted received signal to have the lowest achievable strength or power at the receiver port 364 provides the highest achievable cancellation of transmitted interference from the received signal.

[0249] As a result, the feedback loop including the filter circuit 370, the signal combiner 372, and the RSSI circuit 374 acts to maintain the power of the received signal output from the signal combiner 372 at the minimum achievable level.

[0250] When the transmission circuit 401 (Figs. 2 - 6) is not generating a transmitted signal, the reference signal is approximately zero so that the received signal does not substantially change as it propagates through the combiner 372.

[0251] Continuing to refer to Fig. 16, an alternative embodiment of the transmit-receive separation circuit 441 is contemplated. For example, the filter circuit 370 may be or implement a suitable filter other than an FIR filter. Further, the balun 368 may be replaced with another suitable circuit such as a high-frequency buffer or a current mirror. Further, the embodiments described above in conjunction with Figs. 1 - 15 or below in conjunction with Figs. 17 - 19 may be applicable to the transmit-receive separation circuit 441 of Fig. 16.

[0252] FIG. 17 is a diagram of the remote antenna unit 14 of FIG. 1 according to one embodiment. The remote antenna unit is similar in structure and operation to the remote antenna unit of FIG. 2, but includes an optical analog interference cancellation circuit 390 instead of the analog interference cancellation circuit 46 of FIG. 2. Further, like numbers refer to components common to FIGS. 2-6 and FIGS. 17-19.

[0253] The analog interference cancellation circuit 390 may include electrical and optical circuits similar to the electrical and optical circuits disclosed in U.S. Patent Publication No. 2017 / 0170903 to Jain et al., which is incorporated by reference. For example, the analog interference cancellation circuit 390 includes an electro-optical converter 392 configured to convert a transmission signal from the transmitter circuit 401 from the electrical domain to the optical domain, and an opto-electrical converter 394 configured to convert an analog cancellation signal from the optical domain to the electrical domain. In some examples, the analog interference cancellation circuit further includes an optical filter (not shown) between the electro-optical converter 392 and the opto-electrical converter 394.

[0254] Continuing to refer to FIG. 17, alternative embodiments of the transmit-receive separation circuit 441 are contemplated. For example, the analog interference cancellation circuit 390 may complement rather than replace the analog interference cancellation circuit 46 of FIG. 2. Further, the analog interference cancellation circuit 390 may complement or replace one or more of the analog interference cancellation circuits 46 of FIGS. 3-6. Further, the embodiments described above in conjunction with FIGS. 1-16, or below in conjunction with FIGS. 18 and 19, may be applicable to the transmit-receive separation circuit 441 of FIG. 17.

[0255] FIG. 18 is a diagram of the remote antenna unit 14 of FIG. 1 according to an embodiment in which the remote antenna unit 14 is similar to the remote antenna unit 14 of FIG. 6 but has separate (e.g., non-shared) transmit and receive antennas 60. That is, each antenna 60 is dedicated either to transmitting a downlink signal or a component thereof or to receiving an uplink signal. Being composed of separate transmit and receive antennas 60 improves the overall separation between the transmit antenna and the receive antenna, and thus enables the transmit-receive separation circuit 44 to be omitted from the remote antenna unit 14. Omitting the transmit-receive separation circuit 44 enables the separation circuit controller 98 to be omitted from the digital interference cancellation circuit 50. In FIG. 18, reference numerals with the same numbers are common to FIGS. 1-6 and FIGS. 17 and 18.

[0256] Except for changes in operation due to the absence of the transmit-receive separation circuit 44 and the separation circuit controller 98, the circuitry of the remote antenna unit 14 may operate in a manner similar to that described above in conjunction with FIG. 6.

[0257] Continuing to refer to FIG. 18, alternative embodiments of the remote antenna unit 14 are contemplated. For example, the embodiments described above in conjunction with FIGS. 1-17 or below in conjunction with FIG. 19 may be applicable to the remote antenna unit 14 of FIG. 18.

[0258] FIG. 19 is a diagram of the remote antenna unit 14 of FIG. 1 according to an embodiment, where the remote antenna unit 14 is similar to the remote antenna unit 14 of FIG. 6, but each operator has its own shared transmit and receive antenna 60 and its own transmitter circuit 40 and its own receiver circuit 52. That is, each antenna 60 is dedicated to each operator and is configured for both transmitting a downlink signal or a component thereof and receiving an uplink signal in a manner adjusted and synchronized for the operator. That is, the operator synchronizes the transmission of the downlink signal and the reception of the uplink signal on each antenna 60 so that such transmission and reception do not overlap in time. A switch 400, which may be similar to the switch 150 of FIG. 7, is configured to provide separation between each receiver circuit 52 and each antenna 60 while the remote antenna unit 14 is transmitting a downlink signal, and is configured to provide separation between each transmitter circuit 40 and each antenna while the remote antenna unit is receiving an uplink signal. In FIG. 19, reference numerals with the same numbers are common to FIGS. 1 - 6 and FIGS. 17 - 19.

[0259] Continuing to refer to FIG. 19, an alternative embodiment of the remote antenna unit 14 is contemplated. For example, the embodiments described above in conjunction with FIGS. 1 - 18 may be applicable to the remote antenna unit 14 of FIG. 19.

[0260] The methods and techniques described herein may be implemented in analog electronic circuits, digital electronic circuits, or in programmable processors (e.g., dedicated processors, general-purpose processors such as computers, microprocessors, or microcontrollers), or other circuits (e.g., FPGAs), firmware, software, or combinations thereof. Apparatuses embodying these techniques may include appropriate input and output devices, a programmable processor, and a storage medium tangibly embodying program instructions for execution by the programmable processor. The processes embodying these techniques may be implemented by a programmable processor executing a program of instructions to perform the desired functions by operating on input data and generating appropriate outputs. The techniques may advantageously be implemented in one or more programs executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Generally, the processor will receive instructions and data from read-only memory and / or random access memory. Suitable storage devices tangibly embodying computer program instructions and data include, by way of example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and DVD disks. Any of the foregoing may be supplemented by, or incorporated in, specially designed application specific integrated circuits (ASICs).

[0261] Exemplary embodiments Example 1 is a remote antenna unit, including a first transmitter configured to generate at least one first transmission signal, a first receiver configured to process at least one received signal, and one or more first antennas respectively coupled to at least one of the first transmitter and the receiver, a first antenna array, wherein each of at least one of the first antennas is configured to radiate a respective downlink signal in response to each of at least one of the first transmission signals, and each of at least one of the first antennas is configured to generate one of at least one received signal in response to an uplink signal; a first and a second interference circuit, each coupled to the first transmitter and the receiver respectively, and each configured to reduce interference caused by one or more of at least one first transmission signal, at least one downlink signal radiated by one of the one or more first antennas, and at least one interfering downlink signal radiated by one of the one or more other antennas in each of at least one received signal.

[0262] Example 2 further includes a second transmitter and a second receiver, and the antenna array includes a multiple-input multiple-output antenna array having at least two antennas respectively coupled to the first and second transmitters and the first and second receivers, including the remote antenna unit of Example 1.

[0263] Example 3 includes the remote antenna unit of Example 1 or 2, wherein the antenna array includes a single antenna.

[0264] Example 4 includes the remote antenna unit of any one of Examples 1 to 3, wherein one of the first and second interference circuits includes a separation circuit configured to electrically isolate the receiver from the transmitter.

[0265] Example 5 includes an analog interference cancellation circuit in which one of the first and second interference circuits is configured to generate a corresponding correction signal for each received signal, and the first receiver is configured to generate a respective interference-canceled received signal in response to each received signal and the corresponding correction signal, and includes a remote antenna unit according to any one of Examples 1 to 4.

[0266] Example 6 includes an analog interference cancellation circuit in which one of the first and second interference circuits is configured to generate a corresponding correction signal for each received signal, and each signal combiner is configured to generate an interference-canceled received signal in response to each received signal and the corresponding correction signal, and includes a remote antenna unit according to any one of Examples 1 to 5.

[0267] Example 7 includes a remote antenna unit according to Example 5 or 6, in which the analog interference cancellation circuit includes a finite impulse response filter.

[0268] Example 8 includes an electro-optical converter configured to generate an optical transmission signal in response to a transmission signal, an optical filter configured to generate a corresponding optical correction signal in response to the optical transmission signal for each received signal, and an opto-electrical converter configured to generate each corresponding correction signal in response to the corresponding optical correction signal, and includes a remote antenna unit according to any one of Examples 5 to 7.

[0269] Embodiment 9 includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal, where one of the first and second interference circuits is included, the receiver includes an analog-to-digital converter configured to generate respective digital received signals in response to each received signal, and the receiver is configured to generate respective interference-canceled received signals in response to each received signal, the respective digital received signals, and the corresponding correction signals, and includes any of the remote antenna units of Embodiments 1 to 8.

[0270] Embodiment 10 includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal, where one of the first and second interference circuits is included, the receiver includes an analog-to-digital converter configured to generate respective digital received signals in response to each received signal, and respective signal combiners configured to generate interference-canceled received signals in response to the respective digital received signals and the corresponding correction signals, and includes any of the remote antenna units of Embodiments 1 to 9.

[0271] Embodiment 11 further includes an interference antenna array including an interference receiver configured to process at least one interfering received signal and one or more interference antennas, where the one or more interference antennas are each coupled to the interference receiver and are each configured to generate one of each of the at least one interfering received signals in response to one or more of at least one interfering downlink signal, and at least one of each of the first and second interference circuits is coupled to the interference receiver and is configured to reduce interference caused by one or more of at least one interfering downlink signal in each of the at least one received signals, and includes any of the remote antenna units of Embodiments 1 to 10.

[0272] Example 12 further includes a second transmitter configured to generate at least one second transmission signal, and a second antenna array including one or more second antennas, where the one or more second antennas are each coupled to the second transmitter and are each configured to radiate a respective second downlink signal in response to each of the at least one second transmission signals, and at least one of each of the first and second interference circuits is coupled to the second transmitter and is configured to reduce interference caused by the one or more second downlink signals in each of the at least one received signal, and includes a remote antenna unit according to any one of Examples 1 to 11.

[0273] Example 13 includes a remote antenna unit according to any one of Examples 1 to 12, where at least one transmission signal and at least one reception signal are in the same frequency band.

[0274] Example 14 includes a remote antenna unit according to any one of Examples 1 to 13, where at least one transmission signal and at least one reception signal include at least one same frequency.

[0275] Example 15 includes a remote antenna unit according to any one of Examples 1 to 14, where each respective downlink signal and uplink signal are in the same frequency band.

[0276] Example 16 includes a remote antenna unit according to any one of Examples 1 to 15, where each respective downlink signal and uplink signal include at least one same frequency.

[0277] Example 17 includes a remote antenna unit according to any one of Examples 1 to 16, where the downlink signals and uplink signals radiated by one of the one or more other antennas are in the same frequency band.

[0278] Example 18 is a distributed antenna system including a master unit and at least one remote antenna unit coupled to the master unit, each of the at least one remote antenna unit including a respective transmitter configured to generate at least one transmission signal, a respective receiver configured to process at least one received signal, and one or more antennas each coupled to at least one of the transmitter and the receiver, each antenna array being such that at least one of the antennas is configured to radiate a respective downlink signal in response to each of the at least one transmission signals, and at least one of the antennas is configured to generate each of the at least one received signals in response to an uplink signal; and first and second interference circuits each coupled to the transmitter and the receiver and each configured to reduce interference caused by one or more of at least one transmission signal, at least one downlink signal radiated by one of the one or more antennas, and at least one interfering downlink signal radiated by one of the one or more other antennas in each of the at least one received signals.

[0279] Example 19 includes the distributed antenna system of Example 18, further comprising at least one base station coupled to the master unit and each configured to generate one or more respective downlink data signals and receive one or more respective uplink data signals, each transmitter being configured to generate a respective at least one transmission signal in response to each of the one or more downlink data signals, and each receiver being configured to generate each of the one or more uplink data signals in response to a respective at least one received signal.

[0280] Example 20 includes the distributed antenna system of Example 19, wherein at least one of at least one base station is configured to cause at least one of the transmitters of at least one remote antenna unit to generate a transmission signal only while the receiver of the same remote antenna unit is not processing the received signal.

[0281] Example 21 includes a distributed antenna system according to any one of Examples 18 to 20, including: a first interference receiver configured to process at least one interfering received signal, and an interference antenna array including one or more interference antennas, wherein the one or more interference antennas are each coupled to the interference receiver and each configured to generate one of the at least one interfering received signal in response to one or more of the at least one interfering downlink signals from another one of the remote antenna units; and at least one of the first and second interference circuits is coupled to the interference receiver and configured to reduce interference caused by one or more of the at least one interfering downlink signals from another one of the remote antenna units in each of the at least one received signal.

[0282] Example 22 includes a method including reducing interference in a received signal caused by at least one of a transmission signal generated by a remote antenna unit and a downlink signal radiated by the remote antenna unit using a first interference circuit, and further reducing interference in the received signal caused by at least one of the transmission signal and the downlink signal using a second interference circuit.

[0283] Example 23 includes the method of Example 22, further including generating a received signal using an antenna in response to an uplink signal, and coupling a transmission signal to the antenna while generating the received signal using the antenna.

[0284] Example 24 includes the method of Example 22 or 23, further comprising generating a received signal using an antenna and transmitting a downlink signal using another antenna while generating the received signal using the antenna.

[0285] Example 25 includes the method of any one of Examples 22 to 24, wherein reducing interference in a received signal using a first interference circuit includes electrically insulating the received signal from a transmitted signal using the first interference circuit.

[0286] Example 26 further includes generating a downlink signal in response to different transmitted signals, and reducing interference in the received signal includes generating a cancellation signal in response to different transmitted signals and generating a corrected received signal in response to the received signal and the cancellation signal, and includes the method of any one of Examples 22 to 25.

[0287] Example 27 includes the method of any one of Examples 22 to 26, wherein reducing interference in a received signal includes generating a cancellation signal in response to a downlink signal and generating a corrected received signal in response to the received signal and the cancellation signal.

[0288] Example 28 further includes generating a downlink signal in response to different transmitted signals, and further reducing interference in the received signal includes generating a cancellation signal in response to different transmitted signals and generating a corrected received signal in response to the received signal and the cancellation signal, and includes the method of any one of Examples 22 to 27.

[0289] Example 29 includes the method of any one of Examples 22 to 28, wherein further reducing interference in a received signal includes generating a cancellation signal in response to a downlink signal and generating a corrected received signal in response to the received signal and the cancellation signal.

[0290] Embodiment 30 is a transmit-receive separation circuit, including a transmitter port configured to receive a transmission signal, an antenna port configured to be coupled to an antenna, a receiver port configured to receive a reception signal, a first signal path between the transmitter port and the antenna port and configured to impart a first phase shift to a first transmission portion of the transmission signal, a second signal path between the transmitter port and the antenna port and configured to impart approximately the first phase shift to a second transmission portion of the transmission signal, a first leakage path between the transmitter port and the receiver port and configured to impart a second phase shift to a first leakage portion of the transmission signal, and a second leakage path between the transmitter port and the receiver port and configured to impart a third phase shift approximately opposite to the second phase shift to a second leakage portion of the transmission signal.

[0291] Embodiment 31 includes the transmit-receive separation circuit of Embodiment 30, wherein the first signal path includes a first phase shifter configured to impart a first phase shift to a first transmission portion of the transmission signal, a second phase shifter configured to impart approximately zero phase shift to the first transmission portion of the transmission signal, and a first circulator coupled between the first and second phase shifters; and the second signal path includes a third phase shifter configured to impart approximately zero phase shift to a second transmission portion of the transmission signal, a fourth phase shifter configured to impart approximately the first phase shift to the second transmission portion of the transmission signal, and a second circulator coupled between the third and fourth phase shifters.

[0292] Embodiment 32 includes the transmit-receive separation circuit of Embodiment 31, and further includes a first coupling circuit including the first phase shifter and the third phase shift, and a second coupling circuit including the second phase shifter and the fourth phase shift.

[0293] Embodiment 33 includes the transmission-reception separation circuit of Embodiment 31 or 32, in which the first, second, third, and fourth phase shifters are configured such that the first and second transmission portions of the transmission signal have approximately the same signal power at the antenna ports.

[0294] Embodiment 34 further includes a first coupling circuit including a first phase shifter and a third phase shifter, and a second coupling circuit including a second phase shifter and a fourth phase shifter, and the first and second coupling circuits are configured such that the first and second transmission portions of the transmission signal have approximately the same signal power at the antenna ports, including the transmission-reception separation circuit of any one of Embodiments 31 to 33.

[0295] Embodiment 35 includes a first signal path including a first phase shifter configured to impart a first phase shift to a first transmission portion of a transmission signal, a second phase shifter configured to impart approximately a zero phase shift to the first transmission portion of the transmission signal, and a first circulator having a first port coupled to the first phase shifter, a second port coupled to the second phase shifter, and a third port coupled to a receiver port, and a second signal path including a third phase shifter configured to impart approximately a zero phase shift to a second transmission portion of the transmission signal, a fourth phase shifter configured to impart approximately a first phase shift to the second transmission portion of the transmission signal, and a second circulator having a first port coupled to the third phase shifter, a second port coupled to the fourth phase shifter, and a third port coupled to the receiver port, including the transmission-reception separation circuit of any one of Embodiments 30 to 34.

[0296] Embodiment 36 includes a first phase shifter configured to impart a first portion of a second phase shift to a first leakage portion of a transmission signal, a second phase shifter configured to impart a second portion of the second phase shift to the first leakage portion of the transmission signal, and a first circulator coupled between the first and second phase shifters. The second leakage path includes a third phase shifter configured to impart a first portion of a third phase shift to a second leakage portion of the transmission signal, a fourth phase shifter configured to impart a second portion of the third phase shift to the second leakage portion of the transmission signal, and a second circulator coupled between the third and fourth phase shifters. It includes a transmit-receive separation circuit according to any one of Embodiments 30 to 35.

[0297] Embodiment 37 further includes a first coupling circuit including the first phase shifter and the third phase shifter, and a second coupling circuit including the second phase shifter and the fourth phase shifter, and includes the transmit-receive separation circuit of Embodiment 36.

[0298] Embodiment 38 includes the transmit-receive separation circuit of Embodiment 36 or 37, in which the first, second, third, and fourth phase shifters are configured such that the first and second leakage portions of the transmission signal have approximately the same signal power at the receiver port.

[0299] Embodiment 39 further includes a first coupling circuit including the first phase shifter and the third phase shifter, and a second coupling circuit including the second phase shifter and the fourth phase shifter, and the first and second coupling circuits are configured such that the first and second leakage portions of the transmission signal have approximately the same signal power at the receiver port, and includes the transmit-receive separation circuit according to any one of Embodiments 36 to 38.

[0300] Example 40 includes a first phase shifter configured to impart approximately a 90° phase shift to a first leakage portion of a transmission signal, a second phase shifter configured to impart approximately a 90° phase shift to the first leakage portion of the transmission signal, a first circulator having a first port coupled to the first phase shifter, a second port coupled to an antenna port, and a third port coupled to the second phase shifter, and includes a second leakage path including a third phase shifter configured to impart approximately a zero phase shift to a second leakage portion of the transmission signal, a fourth phase shifter configured to impart approximately a zero phase shift to the second leakage portion of the transmission signal, a second circulator having a first port coupled to the third phase shifter, a second port coupled to the antenna port, and a third port coupled to the fourth phase shifter, and includes a transmit-receive separation circuit according to any one of Examples 30 to 39.

[0301] Example 41 includes a first phase shifter configured to impart a first phase shift to a first transmission portion of a transmission signal, a second phase shifter configured to impart approximately zero phase shift to the first transmission portion of the transmission signal, a first circulator having a first port coupled to the first phase shifter, a second port coupled to the second phase shifter, and a third port. The second signal path includes a third phase shifter configured to impart approximately zero phase shift to a second transmission portion of the transmission signal, a fourth phase shifter configured to impart approximately a first phase shift to the second transmission portion of the transmission signal, a second circulator having a first port coupled to the third phase shifter, a second port coupled to the fourth phase shifter, and a third port. The first leakage path includes a first phase shifter configured to impart a first phase shift to a first leakage portion of the transmission signal, and a fifth phase shifter coupled to the third port of the first circulator and configured to impart approximately a first phase shift to the first leakage portion of the transmission signal. The second leakage path includes a third phase shifter configured to impart approximately zero phase shift to a second leakage portion of the transmission signal, and a sixth phase shifter coupled to the third port of the second circulator and configured to impart approximately zero phase shift to the second leakage portion of the transmission signal, and includes a transmit-receive separation circuit according to any one of Examples 30 to 40.

[0302] Example 42 includes a first phase shifter configured to impart a first portion of a second phase shift to a first leakage portion of a transmission signal, a second phase shifter configured to impart a second portion of the second phase shift to the first leakage portion of the transmission signal, a third phase shifter configured to impart a third portion of the second phase shift to the first leakage portion of the transmission signal, and a first circulator coupled between the first and second phase shifters. The second leakage path includes a fourth phase shifter configured to impart a first portion of a third phase shift to a second leakage portion of the transmission signal, a fifth phase shifter configured to impart a second portion of the third phase shift to the second leakage portion of the transmission signal, a sixth phase shifter configured to impart a third portion of the third phase shift to the second leakage portion of the transmission signal, and a second circulator coupled between the fourth and fifth phase shifters. The transmit-receive separation circuit includes any of the transmit-receive separation circuits of Examples 30 to 41.

[0303] Example 43 includes the transmit-receive separation circuit of Example 42, wherein the second phase shifter is configured to change the second portion of the second phase shift in response to a first control signal, and the fifth phase shifter is configured to change the second portion of the third phase shift in response to a second control signal.

[0304] Example 44 includes the transmit-receive separation circuit of Example 42 or 43, wherein the first, second, third, fourth, fifth, and sixth phase shifters are configured such that the first and second leakage portions of the transmission signal have approximately the same signal power at the receiver port.

[0305] Example 45 includes a first circulator having a first port coupled to the first phase shifter configured to impart approximately a 90° phase shift to the first leakage portion of the transmission signal, a second electronically adjustable phase shifter configured to impart approximately a 90° phase shift to the first leakage portion of the transmission signal, a third phase shifter configurable to impart approximately a 90° phase shift to the first leakage portion of the transmission signal, a first port coupled to the first phase shifter, a second port coupled to the antenna port, and a third port coupled to the second phase shifter, and a second leakage path includes a fourth phase shifter configured to impart approximately a zero phase shift to the second leakage portion of the transmission signal, a fifth electronically adjustable phase shifter configured to impart approximately a 90° phase shift to the second leakage portion of the transmission signal, a sixth phase shifter configured to impart approximately a zero phase shift to the second leakage portion of the transmission signal, a first port coupled to the fourth phase shifter, a second port coupled to the antenna port, and a third port coupled to the fifth phase shifter, and includes a transmit-receive separation circuit according to any one of Examples 30 to 44.

[0306] Embodiment 46 includes a first phase shifter configured to impart a first phase shift to a first transmission portion of a transmission signal, a second phase shifter configured to impart approximately zero phase shift to the first transmission portion of the transmission signal, and a first circulator having a first port coupled to the first phase shifter, a second port coupled to the second phase shifter, and a third port. The second signal path includes a third phase shifter configured to impart approximately zero phase shift to a second transmission portion of the transmission signal, a fourth phase shifter configured to impart approximately a first phase shift to the second transmission portion of the transmission signal, and a second circulator having a first port coupled to the third phase shifter, a second port coupled to the fourth phase shifter, and a third port. The first leakage path includes a first phase shifter configured to impart a first phase shift to a first leakage portion of the transmission signal, a fifth electronically adjustable phase shifter coupled to the third port of the first circulator and configured to impart approximately a first phase shift to the first leakage portion of the transmission signal, and a sixth phase shifter configurable to impart approximately a first phase shift to the first leakage portion of the transmission signal. The second leakage path includes a third phase shifter configured to impart approximately zero phase shift to a second leakage portion of the transmission signal, a seventh electronically adjustable phase shifter coupled to the third port of the second circulator and configured to impart approximately a first phase shift to the second leakage portion of the transmission signal, and an eighth phase shifter configured to impart approximately zero phase shift to the second leakage portion of the transmission signal, and includes a transmit-receive separation circuit according to any one of Embodiments 30 to 45.

[0307] Example 47 is a remote antenna unit, comprising a transmitter configured to generate a transmission signal, a receiver configured to process a received signal, and one or more antennas respectively coupled to the transmitter and the receiver, the antenna array being configured to radiate respective downlink signals in response to each of at least one transmission signal, and configured to generate each of at least one received signal in response to an uplink signal, an antenna array, a transmit-receive separation circuit coupled to one of the one or more antennas, the transmitter, and the receiver, the transmit-receive separation circuit being between the transmitter and the antenna and configured to impart a first phase shift to a first transmission portion of the transmission signal, a first signal path, between the transmitter and the antenna and configured to impart an approximately first phase shift to a second transmission portion of the transmission signal, a second signal path, between the transmitter and the receiver and configured to impart a second phase shift to a first leakage portion of the transmission signal, a first leakage path, between the transmitter and the receiver and configured to impart a third phase shift approximately opposite to the second phase shift to a second leakage portion of the transmission signal, a second leakage path, including a remote antenna unit.

[0308] Example 48 is a distributed antenna system comprising a master unit and at least one remote antenna unit coupled to the master unit, each of the at least one remote antenna unit including a respective transmitter configured to generate a transmission signal, a respective receiver configured to process a received signal, and one or more antennas each coupled to the transmitter and the receiver, each antenna array being configured to radiate a respective downlink signal in response to each of the at least one transmission signals and to generate a respective one of the at least one received signal in response to an uplink signal, and each antenna array including a respective transmit-receive separation circuit coupled to one of the one or more antennas, transmitters, and receivers, the transmit-receive separation circuit being between the transmitter and the antenna and being configured to impart a first phase shift to a first transmission portion of the transmission signal, a second signal path between the transmitter and the antenna and being configured to impart an approximately first phase shift to a second transmission portion of the transmission signal, a first leakage path between the transmitter and the receiver and being configured to impart a second phase shift to a first leakage portion of the transmission signal, and a second leakage path between the transmitter and the receiver and being configured to impart a third phase shift approximately opposite to the second phase shift to a second leakage portion of the transmission signal, the distributed antenna system including the distributed antenna system of Example 48.

[0309] Example 49 further includes at least one base station coupled to the master unit and each configured to generate one or more respective downlink data signals and receive one or more respective uplink data signals, each transmitter being configured to generate a respective transmission signal in response to each of the one or more downlink data signals, and each receiver being configured to generate a respective one of the one or more uplink data signals in response to the respective received signal, the distributed antenna system of Example 48.

[0310] Example 50 is a method that includes applying a first phase shift to a first transmission portion of a transmission signal that propagates from a transmitter to an antenna on a first transmission path, applying approximately the first phase shift to a second transmission portion of the transmission signal that propagates from the transmitter to the antenna on a second transmission path, applying a second phase shift to a first leakage portion of the transmission signal that propagates from the transmitter to a receiver on a first leakage path, and applying a third phase shift that is approximately opposite to the second phase shift to a second leakage portion of the transmission signal that propagates from the transmitter to the receiver on a second leakage path.

[0311] Example 51 further includes making the first and second transmission portions of the transmission signal have approximately the same signal power at the antenna, and making the first and second leakage portions of the transmission signal have approximately the same signal power at the receiver, and includes the method of Example 50.

[0312] Example 52 further includes electronically controlling the phase shift applied to one of the first and second transmission portions of the transmission signal, and includes the method of Example 50 or 51.

[0313] Example 53 further includes electronically controlling the phase shift applied to one of the first and second leakage portions of the transmission signal, and includes any of the methods of Examples 50 to 52.

[0314] Example 54 includes any of the methods of Examples 50 to 53, where the first phase shift is approximately 90°.

[0315] Example 55 includes any of the methods of Examples 50 to 54, where the second phase shift is approximately 180° and the third phase shift is approximately 0°.

[0316] Example 56 includes any of the methods of Examples 50 to 55, where the second phase shift is approximately 270° and the third phase shift is approximately 90°.

[0317] Example 57 is a method that includes generating a plurality of leakage components of a transmission signal and interfering with the leakage components to weaken each other to reduce interference in the received signal.

[0318] Example 58 is a transmit-receive separation circuit that includes a transmission port configured to receive a transmission signal, a reception port configured to provide a received signal, a first interference path disposed between the transmission port and the reception port and configured to carry a first component of the transmission signal, and a second interference path disposed between the transmission port and the receiver port and configured to carry a second component of the transmission signal and adjust the second component such that the first and second components of the transmission signal interfere with each other to weaken each other at the receiver port.

[0319] Example 59 includes the transmit-receive separation circuit of Example 58, wherein the first interference path is configured to adjust the first component of the transmission signal by imparting a first phase shift to the first component of the transmission signal, and the second interference path is configured to adjust the second component of the transmission signal by imparting a second phase shift that is approximately opposite to the first phase shift to the second component of the transmission signal.

[0320] Some embodiments of the present invention defined by the following claims are described. Nevertheless, it will be understood that various modifications to the described embodiments can be made without departing from the scope and spirit of the claimed invention. Accordingly, other embodiments are within the scope of the following claims. [Configuration 1] A remote antenna unit, a first transmitter configured to generate at least one first transmission signal, a first receiver configured to process at least one received signal, a first antenna array including one or more first antennas each coupled to at least one of the first transmitter and the receiver, each of at least one of the first antennas being configured to radiate a respective downlink signal in response to each of the at least one first transmission signals, each of at least one of the first antennas being configured to generate a respective one of the at least one received signals in response to an uplink signal, a first antenna array; first and second interference circuits each coupled to the first transmitter and the receiver and each configured to reduce interference caused by one or more of the at least one first transmission signal, at least one downlink signal radiated by one of the one or more first antennas, and at least one interfering downlink signal radiated by one of one or more other antennas in each of the at least one received signals; A remote antenna unit comprising. [Configuration 2] A second transmitter; A second receiver, and further comprising, The remote antenna unit according to Configuration 1, wherein the first antenna array includes a multiple-input multiple-output antenna array having at least two antennas respectively coupled to the first and second transmitters and to the first and second receivers. [Configuration 3] The remote antenna unit according to Configuration 1, wherein the antenna array includes a single antenna. [Configuration 4] The remote antenna unit according to Configuration 1, wherein one of the first and second interference circuits includes a separation circuit configured to electrically insulate the receiver from the transmitter. [Configuration 5] One of the first and second interference circuits includes an analog interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The remote antenna unit according to Configuration 1, wherein the first receiver is configured to generate respective interference-canceled received signals in response to the received signals and the corresponding correction signals for each received signal. [Configuration 6] One of the first and second interference circuits includes an analog interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The remote antenna unit according to Configuration 1, wherein the receiver includes respective signal combiners configured to generate interference-canceled received signals in response to the received signals and the corresponding correction signals for each received signal. [Configuration 7] The remote antenna unit according to Configuration 5, wherein the analog interference cancellation circuit includes a finite impulse response filter. [Configuration 8] The analog interference cancellation circuit an electro-optical converter configured to generate an optical transmission signal in response to the transmission signal; an optical filter configured to be configured to generate a corresponding optical correction signal in response to the optical transmission signal for each received signal; an opto-electrical converter configured to generate each corresponding correction signal in response to the corresponding optical correction signal; The remote antenna unit according to Configuration 5, comprising: [Configuration 9] One of the first and second interference circuits includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The receiver includes an analog-to-digital converter configured to generate respective digital received signals in response to the received signals for each received signal. The receiver is configured to generate respective interference-canceled received signals in response to the respective digital received signals and the corresponding correction signals for each received signal. The remote antenna unit according to Configuration 1. [Configuration 10] One of the first and second interference circuits includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The receiver, for each received signal, an analog-to-digital converter configured to generate respective digital received signals in response to the received signal; Each signal combiner configured to generate an interference-canceled received signal in response to each of the digital received signals and the corresponding correction signals The remote antenna unit according to Configuration 1, comprising [Configuration 11] An interference receiver configured to process at least one interfering received signal An interference antenna array including one or more interference antennas, wherein the one or more interference antennas are each coupled to the interference receiver and are each configured to generate one of the at least one interfering received signals in response to one or more of the at least one interfering downlink signals Each of at least one of the first and second interference circuits is coupled to the interference receiver and is configured to reduce interference caused by one or more of the at least one interfering downlink signals in each of the at least one received signals The remote antenna unit according to Configuration 1 [Configuration 12] A second transmitter configured to generate at least one second transmission signal A second antenna array including one or more second antennas, wherein the one or more second antennas are each coupled to the second transmitter and are each configured to radiate a respective second downlink signal in response to a respective one of the at least one second transmission signals Each of at least one of the first and second interference circuits is coupled to the second transmitter and is configured to reduce interference caused by the respective second downlink signals in each of the at least one received signals The remote antenna unit according to Configuration 1 [Configuration 13] The remote antenna unit according to Configuration 1, wherein the at least one transmission signal and the at least one received signal are in the same frequency band [Configuration 14] The remote antenna unit according to Configuration 1, wherein the at least one transmission signal and the at least one received signal include at least one same frequency [Configuration 15] The remote antenna unit according to Configuration 1, wherein each of the respective downlink signals and the uplink signal are in the same frequency band [Configuration 16] The remote antenna unit according to Configuration 1, wherein each of the downlink signals and the uplink signals includes at least one same frequency. [Configuration 17] The remote antenna unit according to Configuration 1, wherein the downlink signals and the uplink signals radiated by one of the one or more other antennas are in the same frequency band. [Configuration 18] A distributed antenna system, a master unit, and at least one remote antenna unit coupled to the master unit, wherein each of the at least one remote antenna unit includes a respective transmitter configured to generate at least one transmission signal, a respective receiver configured to process at least one received signal, and a respective antenna array including one or more antennas each coupled to at least one of the transmitter and the receiver, wherein each of at least one of the antennas is configured to radiate a respective downlink signal in response to each of the at least one transmission signals, and a respective antenna array, wherein each of at least one of the antennas is configured to generate each of the at least one received signals in response to an uplink signal, a first and a second interference circuit each coupled to the transmitter and the receiver and each configured to reduce interference caused by one or more of the at least one transmission signal, at least one downlink signal radiated by one of the one or more antennas, and at least one interfering downlink signal radiated by one of the one or more other antennas in each of the at least one received signals, A distributed antenna system including the above. [Configuration 19] further comprising at least one base station coupled to the master unit and each configured to generate one or more respective downlink data signals and receive one or more respective uplink data signals, wherein each transmitter is configured to generate the respective at least one transmission signal in response to each of the one or more downlink data signals, Each receiver is configured to generate one of the one or more uplink data signals in response to each of the at least one received signal for each of them. The distributed antenna system according to Configuration 18. [Configuration 20] The distributed antenna system according to Configuration 19, wherein at least one of the at least one base station is configured to cause at least one of the transmitters of at least one of the at least one remote antenna unit to generate a transmit signal only while the receiver of the same remote antenna unit is not processing the received signal. [Configuration 21] One of the at least one remote antenna unit An interference receiver configured to process at least one interfering received signal, An interference antenna array including one or more interference antennas, wherein the one or more interference antennas are each coupled to the interference receiver and each configured to generate one of the at least one interfering received signal in response to one or more of the at least one interfering downlink signals from another one of the remote antenna units. Each of at least one of the first and second interference circuits is coupled to the interference receiver and configured to reduce interference caused by one or more of the at least one interfering downlink signals from the other one of the remote antenna units in each of the at least one received signal. The distributed antenna system according to Configuration 18. [Configuration 22] A method comprising: Reducing interference in a received signal caused by at least one of a transmit signal generated by a remote antenna unit and a downlink signal radiated by the remote antenna unit using a first interference circuit; Further reducing the interference in the received signal caused by at least one of the transmit signal and the downlink signal using a second interference circuit; A method including the above. [Configuration 23] The method according to Configuration 22, further comprising generating the received signal using an antenna in response to an uplink signal and coupling the transmit signal to the antenna while generating the received signal using the antenna. [Configuration 24] generating the received signal using the antenna; while generating the received signal using the antenna, radiating the downlink signal using another antenna; The method according to Configuration 22, further comprising. [Configuration 25] The method according to Configuration 22, wherein reducing interference in the received signal using the first interference circuit includes electrically insulating the received signal from the transmitted signal using the first interference circuit. [Configuration 26] further comprising generating the downlink signal in response to different transmit signals, wherein reducing interference in the received signal is, generating a cancellation signal in response to the different transmit signals; generating a corrected received signal in response to the received signal and the cancellation signal; The method according to Configuration 22, comprising. [Configuration 27] wherein reducing interference in the received signal is, generating a cancellation signal in response to the downlink signal; generating a corrected received signal in response to the received signal and the cancellation signal; The method according to Configuration 22, comprising. [Configuration 28] further comprising generating the downlink signal in response to different transmit signals, wherein further reducing interference in the received signal is, generating a cancellation signal in response to the different transmit signals; generating a corrected received signal in response to the received signal and the cancellation signal; The method according to Configuration 22, comprising. [Configuration 29] wherein further reducing interference in the received signal is, generating a cancellation signal in response to the downlink signal; generating a corrected received signal in response to the received signal and the cancellation signal; The method according to Configuration 22, comprising.

Claims

1. A remote antenna unit, a first transmitter configured to generate at least one first transmission signal, a first receiver configured to process at least one received signal, a first antenna array including one or more first antennas each coupled to at least one of the first transmitter and the first receiver, wherein each of at least one of the first antennas is configured to radiate a respective downlink signal in response to each of the at least one first transmission signals, a first antenna array, wherein each of at least one of the first antennas is configured to generate a respective one of the at least one received signals in response to an uplink signal, first and second interference circuits each coupled to the first transmitter and the first receiver and each configured to reduce interference caused by one or more of the at least one first transmission signal, at least one downlink signal radiated by one of the one or more first antennas, and at least one interfering downlink signal radiated by one of one or more other antennas in each of the at least one received signals, comprising, wherein one of the first and second interference circuits includes a separation circuit configured to electrically insulate the first receiver from the first transmitter, the separation circuit being configured to adjust one or more separation characteristics or parameters in response to a control signal, the remote antenna unit.

2. a second transmitter; and a second receiver, further comprising, The remote antenna unit according to claim 1, wherein the first antenna array includes a multiple-input multiple-output antenna array having at least two antennas respectively coupled to the first and second transmitters and the first and second receivers.

3. The remote antenna unit according to claim 1, wherein the first antenna array includes a single antenna.

4. wherein one of the first and second interference circuits includes an analog interference cancellation circuit configured to generate a corresponding correction signal for each received signal, The remote antenna unit according to claim 1, wherein the first receiver is configured to generate a respective interference-canceled received signal in response to each received signal and the corresponding correction signal.

5. One of the first and second interference circuits includes an analog interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The remote antenna unit according to claim 1, wherein the first receiver includes respective signal combiners configured to generate an interference-canceled received signal in response to each received signal and the corresponding correction signal.

6. The remote antenna unit according to claim 4, wherein the analog interference cancellation circuit includes a finite impulse response filter.

7. The analog interference cancellation circuit includes an electro-optical converter configured to generate an optical transmission signal in response to the at least one first transmission signal. and an optical filter configured to generate a corresponding optical correction signal in response to the optical transmission signal for each received signal. and an opto-electrical converter configured to generate each corresponding correction signal in response to the corresponding optical correction signal. The remote antenna unit according to claim 4.

8. One of the first and second interference circuits includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The first receiver includes an analog-to-digital converter configured to generate respective digital received signals in response to each received signal. The first receiver is configured to generate a respective interference-canceled received signal in response to each received signal and the corresponding correction signal for each of the respective digital received signals. The remote antenna unit according to claim 1.

9. One of the first and second interference circuits includes a digital interference cancellation circuit configured to generate a corresponding correction signal for each received signal. The first receiver, for each received signal, includes an analog-to-digital converter configured to generate respective digital received signals in response to the received signal. Each of the respective signal combiners configured to generate an interference-canceled received signal in response to each of the digital received signals and the corresponding correction signals; The remote antenna unit according to claim 1, comprising:

10. An interference receiver configured to process at least one interfering received signal; An interference antenna array including one or more interference antennas, wherein the one or more interference antennas are each coupled to the interference receiver and are each configured to generate one of the at least one interfering received signals in response to one or more of the at least one interfering downlink signals; and Each of at least one of the first and second interference circuits is coupled to the interference receiver and is configured to reduce interference caused by one or more of the at least one interfering downlink signals in each of the at least one received signals; The remote antenna unit according to claim 1.

11. A second transmitter configured to generate at least one second transmission signal; A second antenna array including one or more second antennas, wherein the one or more second antennas are each coupled to the second transmitter and are each configured to radiate a respective second downlink signal in response to one of the at least one second transmission signals; and Each of at least one of the first and second interference circuits is coupled to the second transmitter and is configured to reduce interference caused by the respective second downlink signals in each of the at least one received signals; The remote antenna unit according to claim 1.

12. The remote antenna unit according to claim 1, wherein the at least one transmission signal and the at least one received signal are in the same frequency band.

13. The remote antenna unit according to claim 1, wherein the at least one transmission signal and the at least one received signal include at least one same frequency.

14. The remote antenna unit according to claim 1, wherein each of the respective downlink signals and the uplink signal are in the same frequency band.

15. The remote antenna unit according to claim 1, wherein each of the respective downlink signals and the uplink signals includes at least one same frequency.

16. The remote antenna unit according to claim 1, wherein the downlink signals and the uplink signals radiated by one of one or more other antennas are in the same frequency band.

17. A distributed antenna system, comprising a master unit, and at least one remote antenna unit coupled to the master unit, wherein each of the at least one remote antenna unit has respective transmitters configured to generate at least one transmission signal, respective receivers configured to process at least one received signal, and respective antenna arrays each including one or more antennas respectively coupled to at least one of the transmitters and the receivers, wherein each of at least one of the antennas is configured to radiate respective downlink signals in response to respective ones of the at least one transmission signal, and respective antenna arrays wherein each of at least one of the antennas is configured to generate respective ones of the at least one received signal in response to uplink signals, first and second interference circuits respectively coupled to the transmitters and the receivers and each configured to reduce interference caused by one or more of the at least one transmission signal, at least one downlink signal radiated by one of the one or more antennas, and at least one interfering downlink signal radiated by one of one or more other antennas in each of the at least one received signal, including, wherein one of the first and second interference circuits includes an isolation circuit configured to electrically isolate the respective receivers from the respective transmitters, and the isolation circuit is configured to adjust one or more isolation characteristics or parameters in response to a control signal, a distributed antenna system.

18. Further comprising at least one base station coupled to the master unit and configured to generate one or more respective downlink data signals and to receive one or more respective uplink data signals, Each transmitter is configured to generate a respective at least one transmission signal in response to each one of the one or more downlink data signals, Each receiver is configured to generate a respective one of the one or more uplink data signals in response to each respective at least one received signal, The distributed antenna system according to claim 17.

19. The distributed antenna system according to claim 18, wherein at least one of the at least one base station is configured to cause at least one of the at least one remote antenna unit to generate a transmission signal only while a receiver of the same remote antenna unit is not processing a received signal.

20. One of the at least one remote antenna unit, An interference receiver configured to process at least one interfering received signal, An interference antenna array including one or more interference antennas, wherein the one or more interference antennas are each coupled to the interference receiver and are each configured to generate a respective one of the at least one interfering received signal in response to one or more of the at least one interfering downlink signals from another one of the at least one remote antenna unit, Each of at least one of the first and second interference circuits is coupled to the interference receiver and is configured to reduce interference caused by one or more of the at least one interfering downlink signals from the other one of the at least one remote antenna unit in each of the at least one received signals, The distributed antenna system according to claim 17.

21. A method comprising: Reducing interference in a received signal caused by at least one of a transmission signal generated by a remote antenna unit and a downlink signal radiated by the remote antenna unit using a first interference circuit; Using a second interference circuit to further reduce interference in the received signal caused by at least one of the transmission signal and the downlink signal; including; One of the first and second interference circuits includes an isolation circuit configured to electrically isolate the receiver of the remote antenna unit from the transmitter, and the isolation circuit is configured to adjust one or more isolation characteristics or parameters in response to a control signal.

22. Generating the received signal using an antenna in response to an uplink signal; and coupling the transmission signal to the antenna while generating the received signal using the antenna. The method according to claim 21, further comprising.

23. Generating the received signal using an antenna; Radiating the downlink signal using another antenna while generating the received signal using the antenna. The method according to claim 21, further comprising.

24. Further comprising generating the downlink signal in response to different transmission signals; Reducing interference in the received signal using the first interference circuit; Generating a cancellation signal in response to the different transmission signals; Generating a corrected received signal in response to the received signal and the cancellation signal. The method according to claim 21, comprising.

25. Reducing interference in the received signal using the first interference circuit; Generating a cancellation signal in response to the downlink signal; Generating a corrected received signal in response to the received signal and the cancellation signal. The method according to claim 21, comprising.

26. Further comprising generating the downlink signal in response to different transmission signals; Further reducing interference in the received signal using the second interference circuit; Generating a cancellation signal in response to the different transmission signals; Generating a corrected received signal in response to the received signal and the cancellation signal. The method according to claim 21, comprising.

27. Further reducing interference in the received signal using the second interference circuit; Generating a cancellation signal in response to the downlink signal; Generating a corrected received signal in response to the received signal and the cancellation signal; The method according to claim 21, comprising:

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