Frequency shift passive intermodulation reduction

Abstract

A system for reducing or eliminating PIM interference in an RX signal is disclosed. The system is configured to generate a frequency-shifted output using RX and TX signals. The frequency-shifted output includes an RX carrier signal component of the RX signal and first and second TX carrier signal components of the TX signal, positioned in the spectrum such that the frequency interval between the first and second TX carrier signal components and the frequency interval between the RX carrier signal and the closest of the first and second TX carrier signal components are smaller than the frequency interval between the RX carrier signal components and the frequency interval between the first and second TX carrier signal components in the TX signal. The system can then use the frequency-shifted output to generate an estimate of the PIM signal component in the RX signal.

Description

[0001] Cross-references to related applications

[0002] This application relates to PCT application No. PCT / CN2020 / 089369, filed May 9, 2020, entitled “Frequency Shift Passive Intermodulation Reduction”, and U.S. Patent Application No. US 16 / 890,265, filed June 2, 2020, entitled “Frequency Shift Passive Intermodulation Reduction”, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to electronics, and more specifically, to reducing nonlinear effects caused by passive intermodulation. Background Technology

[0004] A radio system is a system that transmits and receives signals in the form of electromagnetic waves in the radio frequency (RF) range of approximately 3 kHz to 300 GHz. Radio systems are commonly used for wireless communication, with cellular / wireless mobile technologies (e.g., LTE and 5G systems) being a prominent example. The linearity of the various components of such a system plays a crucial role.

[0005] The linearity of an RF component or system is theoretically easy to understand. That is, linearity generally refers to the ability of a component or system to provide an output signal that is proportional to the input signal. In other words, if a component or system is perfectly linear, the ratio of the output signal to the input signal is a straight line. Achieving this behavior in real-world components and systems is far more complex, requiring the resolution of many challenges related to linearity, often at the expense of other performance parameters, such as efficiency.

[0006] Made of semiconductor materials, power amplifiers are inherently nonlinear and must operate at relatively high power levels. When considering the linear design of RF systems, active components (such as power amplifiers) are typically analyzed first. Power amplifier outputs with nonlinear distortion can lead to reduced modulation accuracy and / or out-of-band emissions. Therefore, wireless communication systems have stringent specifications regarding the linearity of power amplifiers, and various techniques (e.g., digital predistortion) have been developed to improve the performance of power amplifiers and other active devices during the design and operation phases.

[0007] It's easy to forget that passive devices used in RF systems, such as loose cable connections, aging antennas, suboptimal duplexers, or dirty connectors, can also introduce nonlinear effects. Although sometimes relatively small, these nonlinearities can severely impact system performance if left uncorrected. Passive intermodulation (PIM) is one example of a nonlinear effect caused by the nonlinearity of passive components. Several factors affect the cost, quality, and robustness of PIM reduction solutions in RF systems. Physical constraints, such as space / surface area, and regulatory limitations can further restrict the requirements or specifications of PIM reduction circuitry. Therefore, trade-offs and subtleties must be carefully considered when designing passive intermodulation reduction solutions for RF applications. Attached Figure Description

[0008] To gain a more complete understanding of this disclosure and its features and advantages, reference is made to the following description in conjunction with the accompanying drawings, wherein like reference numerals denote like parts, wherein:

[0009] Figure 1 A wireless communication system according to some embodiments of the present disclosure is shown, wherein PIM reduction using frequency shift can be achieved;

[0010] Figure 2 shows a schematic block diagram of a communication system using traditional PIM to reduce circuitry;

[0011] Figure 3 shows a schematic frequency domain representation of the steps for performing PIM reduction using a conventional PIM reduction circuit;

[0012] Figure 4 A schematic block diagram of a communication system employing a PIM reduction circuit with frequency shift is shown according to some embodiments of the present disclosure;

[0013] Figure 5 Flowcharts are provided for a method for achieving PIM reduction using frequency shift according to some embodiments of the present disclosure;

[0014] Figure 6 A schematic frequency domain representation of the steps for performing PIM reduction using a PIM reduction circuit with frequency shift is shown;

[0015] Figure 7 A schematic block diagram of a communication system employing PIM reduction circuitry with frequency shifting, according to some embodiments of the present disclosure, is shown, and example details of the transmitter and receiver are further shown; and

[0016] Figure 8 Schematic block diagrams of example data processing systems according to some embodiments of the present disclosure are provided. These exemplary data processing systems can be configured to achieve at least a portion of PIM reduction with frequency shift.

[0017] This disclosure

[0018] Non-limiting aspects of this disclosure are set out in the following numbered clauses.

[0019] 1. A system for reducing passive intermodulation (PIM) in a received signal (RX signal) including an RX carrier signal component and a PIM signal component, the system comprising:

[0020] One or more frequency shift circuits are configured to, when a signal to be transmitted (TX signal) includes at least first and second TX carrier signal components, such that the frequency interval between the first and second TX carrier signal components is a first value, perform frequency shifting of one or more signal components of the RX signal and the TX signal to generate a frequency shifted output, the frequency shifted output including aligned PIM signal components with the first and second TX carrier signal components, such that the frequency interval between the first and second TX carrier signal components, and the frequency interval between the PIM signal component and the closest one of the first carrier signal component and the second TX carrier signal component, are a second value, wherein the second value is less than the first value; and

[0021] The PIM estimation circuit is configured to generate an estimate of the PIM signal component to be applied to the RX signal based on the frequency shift output, so as to generate an RX signal with reduced PIM.

[0022] 2. The system according to Clause 1 further includes a combiner circuit configured to apply an estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0023] 3. The system according to Clause 1, wherein the application estimation includes an estimation of removing the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

[0024] 4. The system according to Clause 1 further includes one or more decimation circuits configured to decimate at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

[0025] 5. The system according to Clause 4, wherein the one or more decimation circuits are configured to decimate at least one of the RX signal and the TX signal before the one or more frequency shift circuits perform frequency shifting of one or more of the RX signal and the TX signal to generate the frequency shift output.

[0026] 6. The system according to Clause 4 further includes interpolation circuitry configured to interpolate the estimate of the PIM signal component before applying the estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0027] 7. The system according to Clause 1, wherein if a frequency shift is performed on the RX signal to generate a frequency-shifted output, the one or more frequency-shifting circuits are further configured to perform a reverse frequency shift on the estimation of the PIM signal components before the estimation of the PIM signal components is applied to the RX signal to generate an RX signal with reduced PIM.

[0028] 8. The system according to Clause 1, wherein the second value is at least twice as small as the first value.

[0029] 9. The system according to Clause 1, wherein when frequency shifting is performed to produce a frequency-shifted output, the PIM signal component and the RX carrier signal component are not frequency-shifted relative to each other.

[0030] 10. The system according to Clause 1, wherein the estimation of the generated PIM signal component includes filter coefficients of a generation filter configured to be applied to an RX signal to reduce the PIM signal component in the RX signal.

[0031] 11. The system according to Clause 10, wherein the filter coefficients are generated iteratively.

[0032] 12. A system for reducing passive intermodulation (PIM), the system comprising:

[0033] One or more frequency shift circuits are configured as follows:

[0034] Receive the received signal (RX signal) including the RX carrier signal component.

[0035] Receive a transmit signal (TX signal) comprising at least first and second TX carrier signal components, wherein the frequency interval between the first and second TX carrier components is a first value, and

[0036] A frequency-shifted output is generated, the frequency-shifted output including RX carrier signal components, a first TX carrier signal component, and a second TX carrier signal component aligned in the spectrum, such that the frequency interval between the first and second TX carrier signal components and the frequency spacing between the RX carrier signal and the closest of the first and second TX carrier signal components are second values, wherein the second value is less than the first value; and

[0037] The PIM estimation circuit is configured to generate an estimate of the PIM signal component to be applied to the RX signal based on the frequency shift output, so as to generate an RX signal with reduced PIM.

[0038] 13. The system according to Clause 12 further includes a combiner circuit configured to apply an estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0039] 14. The system according to Clause 12, wherein the application estimation includes an estimation of removing the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

[0040] 15. The system according to Clause 12 further includes one or more decimation circuits configured to decimate at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

[0041] 16. The system according to Clause 15 further includes interpolation circuitry configured to interpolate the estimate of the PIM signal component before applying the estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0042] 17. The system according to Clause 12, wherein if a frequency shift is performed on the RX carrier signal component to generate a frequency-shifted output, the one or more frequency-shifting circuits are further configured to perform a reverse frequency shift on the estimate of the PIM signal component before the estimate of the PIM signal component is applied to the RX signal to generate an RX signal with a reduced PIM.

[0043] 18. The system according to Clause 12, wherein at least a portion of the estimation of PIM signal components based on the frequency shift output is configured to be performed at a clock rate less than twice the frequency interval between the first and second TX carrier signal components in the TX signal.

[0044] 19. A computer-implemented method for reducing passive intermodulation (PIM) in a received signal (RX signal) including an RX carrier signal component and a PIM signal component, the method comprising:

[0045] When the signal to be transmitted (TX signal) includes at least first and second TX carrier signal components, such that the frequency interval between the first and second TX carrier signal components is a first value, frequency shifting is performed on one or more signal component portions of the RX signal and the TX signal to generate a frequency-shifted output, the frequency-shifted output including aligned RX carrier signal components and the first and second TX carrier signal components, such that the frequency interval between the first and second TX carrier signal components, and the frequency interval between the RX signal component and the closest one of the first and second TX carrier signal components, are second values, wherein the second value is less than the first value; and

[0046] Based on the frequency shift output, an estimate of the PIM signal component to be applied to the RX signal is generated to generate an RX signal with reduced PIM.

[0047] 20. The method according to Clause 19, wherein the applied estimation includes an estimation of removing the PIM signal component from the RX signal. Detailed Implementation

[0048] Overview

[0049] The systems, methods, and apparatuses disclosed herein each have several innovative aspects, none of which alone is responsible for all the desired properties disclosed herein. Details of one or more implementations of the subjects described in this specification are set forth in the following description and figures.

[0050] To illustrate the purpose of using frequency shift to reduce PIM as proposed herein, it may be helpful to first understand the phenomena that may be at play in communication systems. The following basic information can be considered as the basis for a proper interpretation of this disclosure. Such information is provided for illustrative purposes only and should therefore not be construed in any way as limiting the broad scope of this disclosure and its potential applications.

[0051] Passive intermodulation (PIM) is a consequence of passive components with nonlinear characteristics in the signal chain. Passive intermodulation occurs when two or more RF signals accidentally mix as they pass through passive components with nonlinear properties. In the cellular industry, two or more transmit (TX) carrier signals can mix together, and the resulting intermodulation product (often called a "PIM signal component") can fall into the receiver's frequency band, reducing receiver sensitivity, degrading receive (RX) signal performance, or even completely blocking communication. The resulting interference can affect the cell causing the PIM and other nearby receivers. For example, in LTE band 2, the downlink frequency range is specified from 1930 MHz to 1990 MHz, while the uplink range is from 1850 MHz to 1910 MHz. If two TX carrier signals with frequencies of 1940 MHz and 1980 MHz are transmitted from a base station system with PIM, their intermodulation can result in a 1900 MHz PIM signal component that will fall into the receiver's frequency band and affect the receiver. Furthermore, their intermodulation can generate a 2020MHz PIM signal component, which can affect other systems.

[0052] As the spectrum becomes increasingly congested, and frequency allocation and antenna-sharing schemes become more prevalent, the likelihood of intermodulation interference (PIM) between different carrier signals increases accordingly. Traditional methods of avoiding PIM using frequency planning are now virtually impossible. Coupled with these challenges, the adoption of new digital modulation schemes means increased peak power in communication systems, exacerbating the severity of passive intermodulation problems and making them no longer negligible. This problem is particularly acute for base stations, where several network systems typically share the same infrastructure, and closely spaced carrier signals can share a single antenna, allowing different transmitted signals to be transmitted through the same nonlinear passive device.

[0053] Because the nonlinearity of passive components varies with temperature, humidity, mechanical stability, and device aging, passive intermodulation (PIM) is inherently a time-dependent phenomenon. Therefore, PIM reduction typically involves using an adaptive model of how PIM affects the RX signal. This model defines the coefficients of the filter to be applied to the RX signal in the digital domain to attempt to reduce and / or eliminate RX signal distortion caused by PIM. In this way, the PIM reduction circuitry attempts to compensate for the various passive components that cause undesirable nonlinear modifications to the TX signal by applying appropriate modifications to the RX signal. This model is adaptive, meaning it is formed iteratively by repeatedly running an algorithm that gradually adjusts the filter coefficients based on a comparison between the signal to be transmitted and the signals already received. Running the algorithm used to estimate the PIM filter coefficients increases power consumption and introduces additional design complexity to the final product.

[0054] The inventors of this disclosure recognize that conventional PIM reduction algorithms leave room for improvement in terms of power consumption and design complexity due to the operation of algorithms used to estimate PIM filter coefficients. Specifically, when the interval between the carrier signal components of the TX signal is ΔFc (which can be defined, for example, as the center-to-center frequency of two adjacent carrier signals), the algorithm used to estimate the PIM filter coefficients must run at a sampling rate higher than 2*ΔFc to avoid aliasing. The inventors of this disclosure recognize that the running rate of the algorithm used to estimate the PIM filter coefficients can be reduced by performing a frequency shift of some signal components before running the algorithm. To this end, one aspect of this disclosure provides an example system (or apparatus) for reducing PIM interference in an RX signal. The RX signal includes an RX carrier signal component and may include a PIM signal component. The TX signal includes at least first and second TX carrier signal components with a certain frequency interval between them. The system is configured to generate a frequency-shifted output using RX and TX signals. The frequency-shifted output includes RX carrier signal components, a first TX carrier signal component, and a second TX carrier signal component positioned / aligned in the spectrum, such that the frequency interval between the first and second TX carrier signal components and the frequency interval between the RX carrier signal component and the closest of the first and second TX carrier signal components are smaller than the frequency interval between the first and second TX carrier signal components in the TX signal. This means that at least one of the first and second TX carrier signal components is frequency-shifted compared to the TX signal, which is why this PIM reduction method is referred to herein as "PIM reduction with frequency shift." For example, if the frequency interval between the first and second TX carrier signal components in the TX signal is ΔFc, then the frequency interval between these components in the frequency-shifted output, and the frequency interval between the RX carrier signal component and the closest of the first and second TX carrier signal components, is ΔF'c, which is smaller than ΔFc. The system can then use the frequency-shifted output to generate an estimate of the PIM signal components to be applied to the RX signal, resulting in an RX signal with reduced PIM components. The algorithm for estimating PIM filter coefficients must run at a rate only higher than 2*ΔF'c to avoid aliasing, but this rate can be lower than 2*ΔFc. Therefore, performing a frequency shift as described herein allows the minimum required rate for the algorithm to estimate PIM filter coefficients to be reduced from 2*ΔFc to 2*ΔF'c. Reducing the algorithm's rate can advantageously allow for reduced power consumption and / or design complexity.

[0055] As those skilled in the art will understand, aspects of this disclosure, particularly the aspect of PIM reduction with frequency shift described herein, can be implemented in various ways—for example, as a method, system, computer program product, or computer-readable storage medium. Therefore, aspects of this disclosure can take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, which are generally referred to herein as “circuit,” “module,” or “system.” The functionality described in this disclosure can be implemented as an algorithm executed by one or more hardware processing units of one or more computers, such as one or more computers. In various embodiments, different steps and portions of any method described herein can be executed by different processing units. Furthermore, aspects of this disclosure can take the form of a computer program product embodied in one or more computer-readable media, preferably non-transitory, embodying, for example, stored computer-readable program code. In various embodiments, such a computer program can, for example, be downloaded (updated) to existing devices and systems (e.g., to existing RF transmitters, receivers, and / or their controllers, etc.) or stored during the manufacture of these devices and systems.

[0056] The following detailed description presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in many different ways, for example, as defined and covered by the claims or selected examples. In the following description, reference is made to the accompanying drawings, wherein similar reference numerals may denote the same or functionally similar elements. It should be understood that the elements shown in the drawings are not necessarily drawn to scale. Furthermore, it will be understood that some embodiments may include more elements and / or a subset of the elements shown in the figures than are shown in the figures. In addition, some embodiments may combine any suitable combination of features from two or more figures.

[0057] Descriptions may use the phrases “in an embodiment” or “in an implementation,” each of which may refer to one or more of the same or different implementations. Unless otherwise specified, ordinal adjectives such as “first,” “second,” and “third” are used to describe a common object only to indicate different instances of similar objects referred to, and not to imply that the described object must be in a given sequence in time, space, hierarchy, or any other way. Furthermore, for the purposes of this disclosure, the phrase “A and / or B” or the symbol “A / B” means (A), (B), or (A and B), while the phrase “A, B, and / or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and / or C). As used herein, the symbol “A / B / C” means (A, B, and / or C). The term “between” when used with respect to a measurement range includes the end of the measurement range.

[0058] The illustrative embodiments are described using terminology commonly used by those skilled in the art to convey the essence of their work to others skilled in the art. For example, the term "connection" refers to a direct electrical connection between connected things without any intermediate devices / components, while the term "coupling" refers to a direct electrical connection between connected things, or an indirect connection (e.g., an indirect electrical connection) via one or more passive or active intermediate devices / components. In another example, the term "circuit" refers to one or more passive and / or active components arranged to cooperate with each other to provide a desired function. Sometimes, the term "circuit" may be omitted in this specification (e.g., a PIM reduction circuit may be simply referred to as "PIM reduction," etc.). If used, the terms "substantially," "approximately," "about," etc., may be used generically to refer to a specific value described herein or known in the art, within + / -20% of the target value, for example, within + / -10% of the target value.

[0059] Example wireless communication system

[0060] Figure 1 A wireless communication system 100 according to some embodiments of the present disclosure is illustrated, wherein PIM reduction using frequency shift can be implemented. The wireless communication system 100 may include a base station 110 and a plurality of mobile stations, examples of which are shown in... Figure 1 The diagram shows a first mobile station 120, a second mobile station 130, and a third mobile station 140. Base station 110 can be coupled to a back-end network (not shown) of the wireless communication system and can provide communication between mobile stations 120, 130, and 140 and the back-end network. In various embodiments, the wireless communication system 100 may include multiple base stations similar to base station 110, which may be arranged, for example, in a cell. For simplicity and illustrative purposes, Figure 1 Only one base station 110 is shown in the image.

[0061] In some embodiments, the wireless communication system 100 may support multiple standards and multiple frequency bands for communication. For example, the wireless communication system 100 may support LTE, Wideband Code Division Multiple Access (WCDMA), and Global System for Mobile Communications (GSM) standard communications. Each mobile station 120-140 may support any one or more of these standards. However, the use of these listed standards is merely exemplary, and different parts of the wireless communication system 100 may also support other standards. In addition to multiple standard capabilities, the wireless communication system 100 may also support multiple communication frequency bands. For example, the wireless communication system 100 may support the DCS / PCS band and GSM850 / GSM900 band of GSM, the N2 / N3 band of 5G New Radio (NR), or any other frequency band of these or other radio access technologies and standards.

[0062] Base station 110 can support wireless communication with mobile stations 120-140 using various standard technologies and across multiple frequency bands. Base station 110 can transmit signals to mobile stations 120, 130, and 140 in downlink signals and receive signals from mobile stations 120-140 in uplink signals. For example, base station 110 can receive LTE-compliant signals from the first mobile station 120, WCDMA signals from the second mobile station 130, and GSM signals from the third mobile station 140.

[0063] Cellular systems are deployed across numerous frequency bands defined by a combination of standardization organizations such as the 3rd Generation Partnership Project (3GPP) and government-funded agencies such as the Federal Communications Commission (FCC). Frequency allocations used in commercial cellular networks include both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) variants. In FDD systems, uplink and downlink use separate frequency bands simultaneously, while in TDD systems, uplink and downlink use the same frequency at different times. The challenges associated with PIM (Potential Instability) are particularly pronounced in FDD systems. In some embodiments, wireless communication system 100 may be an FDD system, wherein any system described herein configured to use frequency shifting to achieve PIM reduction may be deployed in base station 110. In some embodiments, any system described herein configured to use frequency shifting to achieve PIM reduction may be deployed in any of mobile stations 120, 130, and 140.

[0064] Traditional PIM reduces

[0065] As described above, embodiments of this disclosure relate to PIM reduction. For this purpose, the system shown in Figure 2 is typically used.

[0066] Figure 2 shows a schematic block diagram of a communication system (e.g., transceiver) 200 employing a conventional PIM reduction circuit 210. Figure 2 illustrates the communication system 200, which may include a transmitter circuit (or, simply, a “transmitter”) 220 and a receiver circuit (or simply, a “receiver”) 240 communicating with the PIM reduction circuit 210. The system may also include a duplexer 260 and an antenna 270.

[0067] As shown in Figure 2, transmitter 220 can be configured to receive TX signal 219 as input and provide TX signal 221 as output, while receiver 241 can be configured to receive RX signal 261 as input and provide RX signal 241 as output. The input TX signal 219 can be a digital sampling sequence (e.g., a vector). In some embodiments, the input TX signal 219 may include one or more active channels in the frequency domain, but for simplicity, an input TX signal with only one channel (i.e., a single frequency range within the band) is described. In some embodiments, the input TX signal 219 can be a baseband digital signal. The output TX signal 221 can be an analog signal. In some embodiments, the output TX signal 221 can be a TX signal up-converted to RF and amplified by a power amplifier (PA) of transmitter 220. The input RX signal 261 can also be an analog signal, such as an RX signal in RF, received by a low-noise amplifier (LNA) of receiver 240. The output RX signal 241 can be a digital sampling sequence (e.g., a vector). In some embodiments, the output RX signal 241 can be a baseband digital signal.

[0068] The communication system 200 may be an FDD transceiver, in which case the antenna 270 may be configured to simultaneously receive and transmit wireless RF signals in separate, i.e., non-overlapping and non-contiguous frequency bands, for example, frequency bands spaced apart by, for example, a few MHz. In various embodiments, the antenna 270 may be a single broadband antenna (i.e., a single antenna that can be configured to receive / transmit a broadband signal, which may include multiple RX / TX signal components in different frequency bands) or multiple band-dedicated antennas (i.e., multiple antennas, each configured to receive and transmit signals in a specific frequency band). In some embodiments, the output of the antenna 270 may be coupled to one of the inputs of a multi-band duplexer 260. The duplexer 260 is an electromagnetic component configured to filter multiple signals to allow bidirectional communication on a single path between the duplexer 260 and the antenna 270. For this purpose, the duplexer 260 may be configured to provide an RX signal to the receiver 240 and receive a TX signal from the transmitter 220 (e.g., the output of the transmitter 220 may be coupled to another input of the duplexer 260).

[0069] The duplexer 260 may be one of the passive devices contributing to PIM interference in the RX signal received by the receiver 240. The PIM reduction circuit 210 can be used to reduce PIM interference. As shown in FIG2, the PIM reduction circuit 210 may include a PIM estimation circuit 212 and a combiner 202. The PIM estimation circuit 212 can be implemented using an adaptive model to reduce or eliminate at least some PIM interference in the RX signal 241 when applied to the RX signal (e.g., the RX signal 241 output by the receiver 240). To this end, the PIM estimation circuit 212 may be configured to receive the RX signal 243 (e.g., the RX signal 243 may be the same as the RX signal 241, or it may be a signal indicating the RX signal 241) and the TX signal 217 (e.g., the TX signal 217 may be the same as the TX signal 219, or it may be a signal indicating the TX signal 219). The TX signal 217 can indicate at least two TX carrier signal components, as shown in the spectrum diagram of Figure 3 (i.e., the x-axis of all spectrum diagrams described herein refers to frequency f) 302, as the first TX carrier component TX1 and the second TX carrier component TX2. As described in 302, the first and second carrier signal components TX1 and TX2 can have a frequency interval ΔFc in the TX signal. The frequency interval ΔFc can be the frequency range between TX1 and TX2 when these signals are up-converted to RF and wirelessly transmitted by antenna 270, but the TX signal 217 will indicate this interval because it will indicate the first and second carrier signal components TX1 and TX2. The PIM estimation circuit 212 can then be configured to align the TX carrier signal component obtained from the TX signal 217 with the signal component obtained from the RX signal 243 (i.e., having an RX carrier signal component RX1 and a PIM signal component PIM1, as shown in spectrum diagram 304 of FIG3). As shown in diagrams 302 and 304 of FIG3, if the frequency spacing of the first and second TX carrier signal components in the TX signal is ΔFc (i.e., diagram 302), they can be aligned with the RX carrier signal component RX1 such that the frequency spacing between RX1 and the closest one of TX1 and TX2 (in frequency) (TX1 in the example shown in FIG3) is also ΔFc. The PIM signal component PIM1 is generally centered on RX1, so the frequency spacing between PIM1 and the closest one of TX1 and TX2 is also ΔFc. Therefore, for the conventional PIM estimation circuit 212, TX1 - PIM1 = TX2 - TX1 = ΔFc.Then, the PIM estimation circuit 212 (e.g., the coefficient generator portion of the PIM estimation circuit 212) can use the signal components RX1, TX1, and TX2 aligned as shown in the spectrum diagram 304 to generate / update the PIM model coefficients of the filter. When applied to the RX signal (e.g., the RX signal 241 output by receiver 240), it can reduce or eliminate at least some PIM interference in the RX signal 221. Since the frequency spacing between the signal components RX1, TX1, and TX2 in the spectrum diagram 304 is ΔFc, the algorithm for estimating the PIM model coefficients (i.e., the coefficient generator portion of the PIM estimation circuit 212) must operate at a sampling rate of at least 2*ΔFc. Then, the PIM estimation circuit 212 (e.g., the actuator portion of the PIM estimation circuit 212) can use the PIM model coefficients to generate an estimate of the PIM signal component PIM1, the estimate shown in the spectrum diagram 306 of FIG. 3 as the estimated PIMMe. The actuator portion of the PIM estimation circuit 212 must also operate at a sampling rate of at least 2*ΔFc. Then, combiner 202 can apply the estimated PIMe to RX signal 241 to generate a PIM-reduced RX signal 203, an example of which is shown in the spectrum diagram 308 of Figure 3. For example, combiner 202 can subtract the estimated PIMe from RX signal 241. Example communication system using frequency shift to reduce PIM.

[0070] As described above, in conventional PIM reduction systems and methods, both the PIM model coefficient generator and the PIM actuator must operate at a clock rate of at least 2*ΔFc. The inventors of this disclosure recognize that this rate can be reduced by utilizing frequency shifting to achieve PIM reduction, which can advantageously lead to reduced power consumption and a more efficient / simpler design. Figure 4 A schematic block diagram of an example communication system 400 (e.g., a transceiver) employing a PIM reduction circuit 410 with frequency shifting, according to some embodiments of the present disclosure, is shown.

[0071] Figure 4 The communication system 400 shown may include some of the components shown in FIG. 2, namely, transmitter 220, receiver 240, duplexer 260, and antenna 270. The description of these components provided in FIG. 2 applies to... Figure 4The communication system 400 is described herein, therefore, for the sake of brevity, these descriptions will not be repeated here. It should be noted that in some embodiments, the communication system 400 may not include the duplexer 260, but may have one connection between the transmitter 220 and the antenna 270, and another connection between the antenna 270 and the receiver 240. When the duplexer 260 is included in the communication system 400, the duplexer can be one of the passive devices that cause PIM interference. However, in general, the various embodiments of PIM reduction with frequency shift presented herein are suitable for reducing PIM interference caused by any nonlinear passive electronic components or devices other than the duplexer (i.e., passive devices / assemblies that may exhibit nonlinear behavior).

[0072] like Figure 4 As shown, the communication system 400 may include a PIM reduction circuit 410. Circuit 410 may include a PIM estimation circuit 412 (which may be similar to PIM estimation circuit 212) and a combiner 202. The PIM estimation circuit 412 may be implemented by any suitable circuit. For example, in some embodiments, the PIM estimation circuit 412 may be implemented by combinational logic circuitry.

[0073] Compared to the conventional communication system shown in Figure 2, the PIM reduction circuit 410 may further include one or more frequency shift circuits 414, 416, and 418 to achieve PIM reduction with frequency shifting. The frequency shift circuits 414, 416, and 418 in... Figure 4 The circuits shown are separate and are only used to describe different frequency shift operations applied to different signals. In various embodiments of the PIM reduction circuit 410, frequency shift circuits 414, 416, and 418 can be implemented as one or more frequency shift circuits 402. Figure 4 (As shown, it is enclosed within the dotted-dash outline). The operation of the PIM reduction circuit 410 can be referenced... Figure 5 and Figure 6 The illustration is used for description.

[0074] Figure 5 A flowchart of a method 500 for achieving PIM reduction using frequency shifting, according to some embodiments of the present disclosure, is provided. Figure 6 A schematic frequency domain representation of the steps for performing PIM reduction using PIM reduction circuitry 410 is shown. At least a portion of method 500 can be implemented by elements of a communication system according to any embodiment of this disclosure, for example, by referring to... Figure 4 And / or the communication system described in 7, and / or through one or more data processing systems, such as Figure 8 The data processing system 800 is shown. Although system components have been described with reference to the system shown in this figure, any system configured to perform the operations of method 500 in any order is within the scope of this disclosure.

[0075] like Figure 5 As shown, method 500 can begin at step 502, wherein PIM reduction circuit 410 receives an RX signal including (e.g., indicating) an RX carrier signal component RX1, and receives a TX signal including (e.g., indicating) first and second TX carrier signal components TX1 and TX2. For example, the RX signal received by PIM reduction circuit 410 can be RX signal 243 as described above, while the TX signal received by PIM reduction circuit 410 can be TX signal 217 as described above. The frequency interval between the first and second TX carrier signal components TX1 and TX2 in the TX signal can be ΔFc, such as... Figure 6 The spectrum diagram shown is 602, and the TX signal 217 and RX signal 243 provided to the PIM reduction circuit can be signals with a relatively high sampling rate (at least 2*ΔFc).

[0076] Then, method 500 can proceed to step 504, wherein one or more frequency shifting circuits 402 can frequency shift one or more signal components of the RX signal 243 and the TX signal 217 to generate an output that may be referred to as a “frequency shifted output”, the frequency shifted output including aligned PIM signal components of the RX signal and first and second TX carrier signal components of the TX signal, such that the frequency interval between the first and second TX carrier signal components of the TX signal, and the frequency interval between the PIM signal component of the RX signal and the closest one of the first and second TX carrier signal components of the TX signal (i.e., TX1 in the example described herein), is ΔF'c, where ΔF'c is less than ΔFc. Figure 6 The spectrum diagram 604 illustrates how components RX1, TX1, and TX2 are aligned with the frequency interval ΔFc, similar to how they are aligned in the conventional PIM reduction system described above. In contrast to such a system, the PIM reduction circuit 410 is configured to generate a frequency-shifted output comprising components RX1, TX1, and TX2 aligned with the frequency interval ΔF'c, where ΔF'c is less than ΔFc, as shown below. Figure 6 The spectrum diagram 606 is shown. For this purpose, at least one TX1 and TX2 are offset relative to another frequency so as to reduce the frequency interval between TX1 and TX2 from ΔFc to ΔF'c. In addition, both TX1 and TX2 are aligned relative to RX1 such that the frequency interval between RX1 and one of TX1 and TX2 that are closer to RX1 in frequency is also ΔF'c. Figure 4 The frequency shift circuit 414 shown can be considered as a circuit configured to implement such a frequency shift of at least one of TX1 and TX2. Figure 4The frequency shift circuit 416 shown can be considered as a circuit configured to achieve a frequency shift of RX1 (and therefore the PIM signal component PIM1 of the RX signal 217) if RX1 is frequency shifted to align with TX1 and TX2, such that TX1-PIM1 = TX2-TX1 = ΔF'c. On the other hand, if TX1 and TX2 are frequency shifted to align TX1 and TX2 with RX1, then the frequency shift circuit 414 can be a circuit configured to achieve such a frequency shift. Figure 6 The spectrum diagram 606 shown illustrates an example of the frequency-shifted output generated in step 504. It should be noted that, although... Figure 6 The spectrum diagram shown illustrates the frequency intervals ΔFc and ΔF'c as a center-to-center range (i.e., a given frequency interval between two signals of a specific bandwidth is measured as the frequency range between the center frequencies of the two bandwidths). In other embodiments, the frequency intervals ΔFc and ΔF' can be defined in any other way, such as center-to-edge, edge-to-edge, etc.

[0077] Using the frequency offset from step 504, how much smaller ΔF'c is compared to ΔFc depends on the deployment scenario. For example, consider an initial spacing of 60MHz between TX1 and TX2 (i.e., ΔFc = 60MHz), where the spacing is measured in a center-to-center frequency range, and each has a bandwidth of 5MHz. In such an example, the frequency spacing between TX1 and TX2 can be reduced to 10MHz (i.e., ΔF'c = 10MHz), and the measurement is again in a center-to-center range, which would be 6 times smaller than the original 60MHz spacing.

[0078] Typically, the minimum interval ΔF'c min According to the signal bandwidth (BW) S ) and PIM bandwidth (BW PIM The calculation is as follows:

[0079]

[0080] Furthermore, if we assume that PIM is third-order distortion (and that the contribution of higher-order PIM is essentially negligible), then BW PIM Compared to BW S It is 3 times larger, and equation (1) can be rewritten as follows:

[0081]

[0082] Therefore, for the example above, where BW S =5MHz, ΔF'c min =10MHz.

[0083] Then, method 500 can proceed to step 506, which includes PIM estimation circuit 412 generating an estimate of the PIM signal component based on the frequency shift output 606 generated in step 504. In some embodiments, step 506 may include, firstly, PIM estimation circuit 412 (e.g., the coefficient generator portion of PIM estimation circuit 412) using signal components RX1, TX1, and TX2 aligned as shown in the spectrum diagram 606 to generate / update the PIM model coefficients of the filter, which, when applied to the RX signal (e.g., the RX signal 241 output by receiver 240), can reduce or eliminate at least some PIM interference in the RX signal. Step 506 may also include PIM estimation circuit 412 (e.g., the actuator portion of PIM estimation module 412) using the PIM model coefficients to generate an estimate of the PIM signal component PIM1. Figure 6 The spectrum shown in Figure 608 is the estimate of PIMe.

[0084] Typically, step 506 may include any known technique for generating estimates of the PIM signal components based on signal components RX1, TX1, and TX2, the difference being that these components are now aligned with a smaller interval ΔF'c in the frequency-shifted output 606 generated in step 504. This smaller interval allows the algorithms used to generate / update the PIM model coefficients and / or the actuators used to generate the PIM estimate PIMe to operate at a lower rate, since the rate may now be only equal to or greater than 2*ΔF'c, which may be less than the 2*ΔFc that must be used in the conventional PIM reduction system described above. Furthermore, since the frequency interval in the frequency-shifted output 606 generated in step 504 is now smaller than ΔFc, the sampling rate of the RX and TX signals can be reduced accordingly. Therefore, in some embodiments, the PIM reduction circuit 410 may also include one or more decimation circuits configured to decimate (i.e., reduce the sampling rate or downsample) at least one of the RX signal 243 and TX signal 217 before the PIM estimation circuit 410 generates estimates of the PIM signal components in step 506. As mentioned above, operating on the decimated signal and / or using circuitry that can run at a lower clock rate can advantageously allow for reduced power consumption and simplified circuit design.

[0085] For example, in some embodiments, frequency shifting circuit 414 may be configured to perform decimation and frequency shifting of TX signal 217 to generate decimated and frequency-shifted TX signal 415. Similarly, frequency shifting circuit 416 may be configured to perform decimation and frequency shifting of RX signal 243 to generate decimated and frequency-shifted RX signal 417. PIM estimation circuit 412 may then use the decimated version of the TX signal (i.e., the decimated and frequency-shifted signal 415) and / or the decimated version of the RX signal (i.e., the decimated and frequency-shifted signal 417) to generate an estimated PIMe in step 506. In some embodiments, PIM reduction circuit 410 may be configured to first perform a decimation operation and then perform the frequency shifting described herein. In other embodiments, PIM reduction circuit 410 may be configured to first perform the frequency shifting described herein and then perform a decimation operation. Furthermore, in various embodiments, the PIM reduction circuit 410 can be configured to achieve any of the following: 1) the TX signal 217 is decimated, but the RX signal 243 is not decimated; 2) the RX signal 243 is decimated, but the TX signal 217 is not decimated; and 3) both the TX signal 217 and the RX signal 243 are decimated. Any of these embodiments can be combined with any of the embodiments described above, in which one of the components RX1, TX1, and TX2 is frequency-shifted by one or more frequency-shifting circuits 402.

[0086] Method 500 may further include step 508, wherein PIM reduction circuitry 410 may apply the estimated PIMe generated in step 506 to RX signal 241 to reduce or eliminate at least some PIM interference in RX signal 241. In some embodiments, step 508 may include combiner 202 to apply the estimated PIMe to RX signal 241 to generate PIM-reduced RX signal 403 (e.g., Figure 4 As shown), an example is as follows: Figure 6 The spectrum diagram is shown in Figure 610. For example, step 508 may include a combiner 202 to subtract the estimated PIMe from the RX signal 241.

[0087] Typically, step 508 may include applying the estimated PIMe generated in step 506 using any known technique to reduce PIM interference in the RX signal 241. In an embodiment where signal component RX1 is frequency-shifted in step 504, the PIM reduction circuit 410 may then be configured to perform a frequency shift of the component PIMe to reverse that shift before performing step 508. In an embodiment where the RX signal 243 is decimated, the PIM reduction circuit 410 may then be configured to perform interpolation (i.e., increase the sampling rate or upsampling) on ​​the signal containing the estimated PIMe to reverse that decimation before performing step 508. In this way, the modeled (i.e., estimated) PIM signal component PIMe can be aligned with the PIM interference in the actual RX signal 241 in time and frequency, such that the estimated PIM signal component PIMe can be used in step 508 to reduce passive intermodulation interference in the RX signal 221.

[0088] After step 508, method 500 can then continue to the next iteration, now using the updated model coefficients, such as... Figure 5 As indicated by the arrows from 508 to 502, steps 502-508 can be iterated again for new RX and TX signals. This is likely the case when the PIM model is an adaptive model, meaning it is formed by gradually adjusting the filter coefficients during iteration based on a comparison between the signal to be transmitted and the signals already received.

[0089] Figure 7 A schematic block diagram of a communication system (e.g., an RF transceiver) 700 employing the PIM reduction circuit 410 as described above, according to some embodiments of the present disclosure, is shown, and example details of the transmitter 220 and receiver 240 are further shown. Figure 7 The communication system 700 shown is Figure 4 An example implementation of the communication system 400 shown is provided, wherein the same reference numerals as those above denote the same or similar elements / parts. Therefore, it is assumed that the description provided for one of these figures is applicable and need not be repeated for the other, and only the differences are described.

[0090] like Figure 7As shown, in some embodiments, transmitter 220 may include a digital filter 722, a digital-to-analog converter (DAC) 724, an analog filter 726, a mixer 728, a power amplifier (PA) 730, and a local oscillator (LO) 732. In such a transmitter, the TX signal 219 can be filtered in the digital domain by the digital filter 724 to generate a filtered input, i.e., a digital signal. The output of the digital filter 722 can then be converted to an analog signal by the DAC 724. The analog signal generated by the DAC 724 can then be filtered by the analog filter 726. The output of the analog filter 726 can then be up-converted to RF by the mixer 728, which can receive signals from the LO 732 to convert the filtered analog signal from the analog filter 726 from baseband to RF. In some embodiments, the PA 730, which may be a PA array, can be configured to amplify the RF signal generated by transmitter 220 (e.g., the RF generated by mixer 728) and provide the amplified RF signal as the TX output signal 221 (which may be a vector). The amplified RF signal 221 can be provided to the antenna 270 for wireless transmission.

[0091] Figure 7 The example illustrates a TX signal 217 based on the TX signal 219 provided to the digital filter 722. However, in other embodiments of this disclosure, the TX signal 217 provided to the PIM reduction circuit 410 can be any other signal in the TX path including the transmitter 220, provided that when these signal components are up-converted to RF and wirelessly transmitted by the antenna 270, such a signal indicates the bandwidth of the various TX carrier signal components (e.g., the first and second TX carrier components TX1 and TX2) and the frequency spacing ΔFc between them. For example, in other embodiments, the TX signal 217 can be a signal based on the output of the digital filter 722, or a signal based on the output of the mixer 728 (which is converted back to the digital domain since the PIM reduction circuit 410 operates on digital signals), and so on.

[0092] Apart from Figure 7 Other embodiments of transmitter 220, besides those shown, are also possible and are within the scope of this disclosure. For example, in another implementation (not shown in this figure), the output of digital filter 722 can be directly converted into an RF signal by DAC 724. In this implementation, the RF signal provided by DAC 724 can then be filtered by analog filter 726. Since DAC 724 will directly synthesize the RF signal in this implementation, in such an embodiment, Figure 7 The mixer 728 and local oscillator 732 shown can be omitted from the transmitter circuit 220.

[0093] like Figure 7As further shown, in some embodiments, receiver 240 may include a digital filter 742, an analog-to-digital converter (ADC) 744, an analog filter 746, a mixer 748, an LNA 750, and an LO 752. LNA 750 can receive the RX signal 261 as input. For this purpose, the input of LNA 750 can be coupled to the output port of antenna 270 (possibly via duplexer 260). Antenna 270 can receive RF signals in different frequency bands, and LNA 250 can amplify the received RF signals. Although... Figure 7 Not specifically shown, but the LNA 750 can be coupled to a harmonic or bandpass filter to filter the received RF signal 761, which has been amplified by the LNA 750 and output as the RX signal 751 by the LNA 750. The mixer 748 can down-convert the RX signal 751 to baseband, receiving a signal from the LO 752 (which may be the same as or different from the LO 732) to convert the RX signal 751 from RF to baseband. The output of the mixer 748 can then be filtered by an analog filter 746. The ADC 744 can then convert the output of the analog filter 746 into a digital signal. The digital signal generated by the ADC 724 can then be filtered in the digital domain by a digital filter 742 to generate a filtered down-converted signal 241, which can be a sequence of digital values ​​indicating the RF signal received by the antenna 270 and can also be modeled as a vector.

[0094] Figure 7 The example illustrates an RX signal 243 based on an RX signal 241 provided from digital filter 742. However, in other embodiments of this disclosure, the RX signal 243 provided to PIM reduction circuitry 410 can be any other signal in the RX path including receiver 240, provided that such a signal indicates the bandwidth and center frequency of various RX carrier signal components (e.g., RX carrier component RX1) when these signal components are in RF and wirelessly received by antenna 270. For example, in other embodiments, TX signal 243 can be a signal based on the input of digital filter 742, or signal 751 provided to mixer 748 (converted back to the digital domain since PIM reduction circuitry 410 operates on digital signals), etc.

[0095] Apart from Figure 7 Other embodiments of receiver 240, besides those shown, are also possible and are within the scope of this disclosure. For example, in another implementation (not shown in this figure), ADC 744 can directly convert the RX signal 751 into a baseband signal. In this implementation, the down-converted signal provided by ADC 744 can then be filtered by digital filter 742. Since ADC 744 will directly synthesize the baseband signal in this implementation, in such an embodiment, Figure 7The mixer 748 and LO 752 shown can be omitted from the receiver circuit 240.

[0096] The communication system 700 described above can also have other variations. For example, although up-conversion and down-conversion are described with respect to baseband frequency, intermediate frequency (IF) can be used instead in other embodiments of the communication system 700. IF can be used in a superheterodyne radio receiver, where the received RF signal is converted to IF before the final detection of information in the received signal is completed. Conversion to IF can be useful for several reasons. For example, when using multi-stage filters, they can all be set to fixed frequencies, making them easier to build and tune. In some embodiments, the mixer of the RF transmitter 220 or receiver 240 may include several such IF conversion stages. In another example, although a single-path mixer is shown in each of the TX path (i.e., the signal path of the signal processed by transmitter 220) and RX path (i.e., the signal path of the signal processed by receiver 240) of the communication system 700, in some embodiments, the TX path mixer 728 and the RX path mixer 748 may be implemented as quadrature up-converters and down-converters, respectively, in which case each of them will include a first mixer and a second mixer. For example, for RX path mixer 748, a first RX path mixer can be configured to perform downconversion by mixing the RX signal 751 and the in-phase component of the local oscillator signal provided by local oscillator 752 to generate an in-phase (I) downconverted RX signal. A second RX path mixer can be configured to perform downconversion by mixing the RX signal 751 and the quadrature component (a component that deviates 90 degrees in phase from the in-phase component of the local oscillator signal provided by local oscillator 752) to generate a quadrature (Q) downconverted RX signal. The output of the first RX path mixer can be provided to the I signal path, and the mixer output of the second RX path can be provided to the Q signal path, which can be substantially 90 degrees out of phase with the I signal path.

[0097] Furthermore, it should be noted that, although in Figure 4 The diagram of the communication system shown and Figure 7 In the illustrated system, a distinction is made between one or more frequency shift circuits 402 and PIM estimation circuits 412. This distinction can be purely functional / logical, differentiating only from functions that can be performed by a PIM estimation loop similar to conventional PIM estimation circuit 212 and functions specifically related to the frequency shift of the PIM reduction techniques described herein. In various embodiments, the functionality of any one of the one or more frequency shift circuits 402, or the functionality of any decimation or interpolation circuitry, can be included or considered as part of the PIM estimation circuit 412, or the functionality of any of these circuits can be distributed across a larger number of separate circuits.

[0098] Example Data Processing System

[0099] Figure 8 A schematic block diagram of an example data processing system 800 according to some embodiments of the present disclosure is provided, which can be configured to achieve at least a portion of PIM reduction with frequency shift according to method 500. For example, the data processing system 800 can be used to implement as referenced. Figure 4 and Figure 7 At least a portion of the described communication system, particularly to implement at least a portion of the PIM reduction circuit 410 described herein.

[0100] like Figure 8 As shown, the data processing system 800 may include at least one processor 802, such as a hardware processor 802, coupled to a memory element 804 via a system bus 806. In this way, the data processing system can store program code in the memory element 804. Furthermore, the processor 802 can execute program code accessed from the memory element 804 via the system bus 806. In one aspect, the data processing system may be implemented as a computer suitable for storing and / or executing program code. However, it should be understood that the data processing system 800 may be implemented in the form of any system including a processor and memory capable of performing the functions described in this disclosure.

[0101] In some embodiments, processor 802 may execute software or algorithms to perform the activities discussed herein, particularly those related to frequency shift PIM reduction, such as that according to method 500, and various techniques implemented by the PIM reduction circuit 410 described herein. Processor 802 may include any combination of hardware, software, or firmware providing programmable logic, including, as non-limiting examples, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), programmable logic arrays (PLAs), integrated circuits (ICs), application-specific integrated circuits (ASICs), or virtual machine processors. Processor 802 may be communicatively coupled to memory element 804, for example in a direct memory access (DMA) configuration, such that processor 802 can read from or write to memory element 808.

[0102] Typically, memory element 804 may include any suitable volatile or non-volatile memory technology, including dual data rate (DDR) random access memory (RAM), synchronous RAM (SRAM), dynamic RAM (DRAM), flash memory, read-only memory (ROM), optical media, virtual memory regions, magnetic tape or tape storage, or any other suitable technology. Unless otherwise specified, any memory element discussed herein should be construed as included in the broad sense of “memory.” Information measured, processed, tracked, or sent to or from any component of the data processing system 800 may be provided in any database, register, control list, cache, or storage structure, all of which may be referenced at any suitable time. Any such storage options may be included in the broad sense of “memory” as used herein. Similarly, any potential processing elements, modules, and machines described herein should be understood as included in the broad sense of “processor.” Each element shown in this figure, for example… Figure 4 and Figure 7 Any circuits / components shown may also include appropriate interfaces for receiving, sending and / or otherwise transmitting data or information in a network environment, so that they can communicate with, for example, another of these elements, a data processing system 800.

[0103] In some exemplary implementations, the mechanisms for achieving PIM reduction with frequency shift in a communication system, as outlined herein, can be implemented by logic encoded in one or more tangible media, which may include non-transitory media, such as embedded logic provided in an ASIC, DSP instructions, or software (which may include object code and source code) to be executed by a processor or other similar machine. In some of these examples, memory elements, such as... Figure 8 The memory element 804 shown can store data or information used for the operations described herein. This includes memory elements capable of storing software, logic, code, or processor instructions that are executed to perform the activities described herein. A processor can execute any type of instructions associated with data or information to implement the operations detailed herein. In one example, the processor (e.g., Figure 8 The processor 802 shown herein can transform an element or item (e.g., data) from one state or thing to another. In another example, the activities outlined herein can be implemented with fixed logic or programmable logic (e.g., software / computer instructions executed by a processor), and the elements identified herein can be some type of programmable processor, programmable digital logic (e.g., FPGA, DSP, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), or ASIC that includes digital logic, software, code, electronic instructions, or any suitable combination thereof.

[0104] Memory element 804 may include one or more physical memory devices, such as local memory 808 and one or more mass storage devices 810. Local memory may refer to RAM or other non-persistent memory devices that are typically used during the actual execution of the program code. Mass storage devices may be implemented as hard disk drives or other persistent data storage devices. Processing system 800 may also include one or more cache memories (not shown) that provide temporary storage for at least some program code in order to reduce the number of times program code must be retrieved from mass storage device 810 during execution.

[0105] like Figure 8 As shown, memory element 804 can store application program 818. In various embodiments, application program 818 can be stored in local memory 808, one or more mass storage devices 810, or separately from local memory and mass storage devices. It should be understood that data processing system 800 can also execute an operating system (…). Figure 8 (Not shown in the image), which can facilitate the execution of application 818. Application 818, implemented in the form of executable program code, can be executed by data processing system 800, for example, by processor 802. In response to executing the application, data processing system 800 can be configured to perform one or more operational or method steps described herein.

[0106] Optionally, the input / output (I / O) devices depicted as input device 812 and output device 814 can be coupled to the data processing system. Examples of input devices may include, but are not limited to, pointing devices such as keyboards and mice. Examples of output devices may include, but are not limited to, monitors or displays, speakers, etc. In some embodiments, output device 814 can be any type of screen display, such as a plasma display, liquid crystal display (LCD), organic light-emitting diode (OLED) display, electroluminescent (EL) display, or any other indicator, such as a dial, barometer, or light-emitting diode (LED). In some embodiments, the system may include a driver (not shown) for output device 814. Input and / or output devices 812, 814 can be coupled to the data processing system directly or via an intermediate I / O controller.

[0107] In one embodiment, the input device and the output device can be implemented as a combined input / output device (in... Figure 8 (Seen in the diagram with dashed lines surrounding input device 812 and output device 814). An example of such a combined device is a touch-sensitive display, sometimes also called a "touchscreen display" or simply a "touchscreen". In such an embodiment, input to the device can be provided by moving a physical object (such as a user's stylus or finger) on or near the touchscreen display.

[0108] Optionally, network adapter 816 may also be coupled to the data processing system to enable it to couple to other systems, computer systems, remote network devices, and / or remote storage devices via an intervening private or public network. The network adapter may include a data receiver for receiving data transmitted to the data processing system 800 by said systems, devices, and / or networks, and a data transmitter for transmitting data from the data processing system 800 to said systems and / or devices. Modems, cable modems, and Ethernet cards are examples of different types of network adapters that can be used with the data processing system 800.

[0109] Select Example

[0110] The following paragraphs provide various examples of the embodiments disclosed herein.

[0111] Example 1 provides a system for reducing or eliminating PIM in an RX signal, which includes an RX carrier signal component and a PIM signal component. The system includes: one or more frequency shifting circuits configured to, when a TX signal includes at least first and second TX carrier signal components, such that when the first and second carrier signal components are transmitted by an antenna, the frequency spacing between the first and second TX carrier components is a first value (ΔFc); and to perform frequency shifting on one or more signal components of the RX signal and the TX signal to generate a frequency-shifted output, the frequency-shifted output including aligned PIM signal components of the RX signal and the first and second TX carrier signal components of the TX signal, such that the frequency spacing between the first and second TX carrier signal components, and the frequency spacing between the PIM signal component of the RX signal and the closest one of the first and second TX carrier signal components of the TX signal, is a second value (ΔF'c), wherein the second value is less than the first value. The system further includes: a PIM estimation circuit configured to generate an estimate of the PIM signal component to be applied to the RX signal based on the frequency-shifted output to generate an RX signal with reduced PIM.

[0112] Example 2 provides a system according to Example 1, further comprising a combiner circuit (e.g., an adder) configured to apply an estimate of the PIM signal components to the RX signal to generate an RX signal with reduced PIM.

[0113] Example 3 provides a system according to Example 1 or 2, wherein the applied estimation includes an estimate of removing (e.g., subtracting) the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

[0114] Example 4 provides a system according to any of the foregoing examples, further comprising one or more decimation circuits configured to decimate (i.e. reduce the sampling rate or downsample) at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

[0115] Example 5 provides a system according to Example 4, wherein the one or more decimation circuits are configured to decimate at least one of the RX signal and the TX signal before the one or more frequency shift circuits perform frequency shifting on one or more signal components of the RX signal and the TX signal to generate the frequency shift output.

[0116] Example 6 provides a system according to Example 4 or 5, further comprising interpolation circuitry configured to interpolate (i.e. increase the sampling rate or upsample) the estimate of the PIM signal component before applying the estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0117] Example 7 provides a system according to any of the foregoing examples, wherein if a frequency shift is performed on the RX signal to generate a frequency-shifted output, the one or more frequency-shifting circuits are further configured to perform a reverse frequency shift on the estimate of the PIM signal components before the estimate of the PIM signal components is applied to the RX signal to generate an RX signal with reduced PIM. In this way, the modeled (i.e., estimated) PIM signal components are aligned with the phase, amplitude, and frequency of PIM interference in the actual received signal, such that the estimated PIM signal components can be used to eliminate or reduce PIM interference in the RX signal.

[0118] Example 8 provides a system according to any of the preceding examples, wherein the second value is at least 2 times smaller than the first value, for example at least 4 times smaller or at least 6 times smaller.

[0119] Example 9 provides a system according to any of the foregoing examples, wherein when frequency shifting is performed to produce a frequency-shifted output, the PIM signal component and the RX carrier signal component are not frequency-shifted relative to each other (i.e., in the frequency-shifted output, the PIM signal component and the RX carrier signal component of the RX signal are not frequency-shifted relative to each other).

[0120] Example 10 provides a system according to any of the preceding examples, wherein the estimation of the generated PIM signal component includes filter coefficients of a generation filter configured to be applied to an RX signal to reduce the PIM signal component in the RX signal.

[0121] Example 11 provides a system according to Example 10, wherein the filter coefficients are generated iteratively.

[0122] Example 12 provides a system for reducing or eliminating PIM. The system includes: one or more frequency shifting circuits configured to receive an RX signal comprising an RX carrier signal component, receive a TX signal comprising at least first and second TX carrier signal components, wherein the frequency spacing between the first and second TX carrier components is a first value (ΔFc), and generate a frequency shift output comprising RX carrier signal components, a first TX carrier signal component, and a second TX carrier signal component aligned in the spectrum, such that the frequency spacing between the first and second TX carrier signal components and the frequency spacing between the RX carrier signal and the closest of the first and second TX carrier signal components is a second value (ΔF'c), wherein the second value is less than the first value. The system further includes: a PIM estimation circuit configured to generate an estimate of the PIM signal components to be applied to the RX signal based on the frequency shift output, to generate an RX signal with reduced PIM.

[0123] Example 13 provides a system according to Example 12, further comprising a combiner circuit (e.g., an adder) configured to apply an estimate of the PIM signal components to the RX signal to generate an RX signal with reduced PIM.

[0124] Example 14 provides a system according to Example 12 or 13, wherein the applied estimation includes an estimate of removing (e.g., subtracting) the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

[0125] Example 15 provides a system according to any one of Examples 12-14 above, further comprising one or more decimation circuits configured to decimate (i.e. reduce the sampling rate or downsample) at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

[0126] Example 16 provides a system according to Example 15, further comprising interpolation circuitry configured to interpolate (i.e., increase the sampling rate or upsample) the estimate of the PIM signal component before applying the estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

[0127] Example 17 provides a system according to any one of Examples 12-16 above, wherein if a frequency shift is performed on the RX carrier signal component to generate a frequency-shifted output, the one or more frequency-shifting circuits are further configured to perform a reverse frequency shift on the estimate of the PIM signal component before the estimate of the PIM signal component is applied to the RX signal to generate an RX signal with reduced PIM. In this way, the modeled (i.e., estimated) PIM signal component is aligned with the phase, amplitude, and frequency of PIM interference in the actual received signal, such that the estimated PIM signal component can be used to reduce or eliminate PIM interference in the RX signal.

[0128] Example 18 provides a system according to any of the foregoing examples, wherein at least a portion of the estimate of the PIM signal components generated based on the frequency shift output is configured to be executed at a clock rate less than twice the frequency interval between the first and second TX carrier signal components in the TX signal. For example, in some embodiments, the algorithm for estimating the PIM model coefficients may operate at a clock rate less than twice the frequency interval between the first and second TX carrier signal components in the TX signal. In another example, in some embodiments, an actuator configured to generate an estimate of the PIM signal components in the RX signal based on the PIM model coefficients may operate at a clock rate less than twice the frequency interval between the first and second TX carrier signal components in the TX signal.

[0129] Example 19 provides a system according to any of the preceding examples, wherein the system is an RF transceiver, such as an RF transceiver for a base station.

[0130] Example 20 provides a computer-implemented method for reducing or eliminating PIM interference in an RX signal. The RX signal includes an RX carrier signal component and a PIM signal component. The RX signal indicates a TX signal, wherein the TX signal includes at least first and second TX carrier signal components such that when the first and second carrier signal components are transmitted by an antenna, the frequency spacing between the first and second TX carrier components is a first value (ΔFc). The method includes frequency shifting one or more signal components of the RX signal and the TX signal to generate a frequency-shifted output, the frequency-shifted output including aligned PIM carrier signal components of the RX signal and the first and second TX carrier signal components of the TX signal, such that the frequency spacing between the first and second TX carrier signal components of the TX signal, and the frequency spacing between an RX carrier signal component of the RX signal and the closest one of the first and second TX carrier signal components of the TX signal, are a second value (ΔF'c), wherein the second value is less than the first value. The method further includes generating an estimate of the PIM signal components to be applied to the RX signal based on the frequency-shifted output to generate an RX signal with reduced PIM.

[0131] Example 21 provides a method according to Example 20, wherein the applied estimation includes an estimate of removing (e.g., subtracting) the PIM signal component from the RX signal.

[0132] Example 22 provides a method according to Example 20 or 21, wherein the method further includes a method for reducing PIM interference in the RX signal by means of a system according to any of the foregoing examples (e.g., according to any of Examples 1-19).

[0133] Example 23 provides a non-transitory computer-readable storage medium including instructions for execution, which, when executed by a processor, are operable to perform operations according to any of the foregoing examples (e.g., operations according to any of Examples 20-22), and / or to enable a system to reduce PIM interference in an RX signal according to any of the foregoing examples (e.g., operations according to any of Examples 1-19). Therefore, in some examples, the non-transitory computer-readable storage medium according to Example 23 may also include instructions operable to perform operations performed by any part of a system according to any of the foregoing examples.

[0134] Changes and Implementation

[0135] Although the above reference Figure 1 The exemplary embodiments shown in Figure 2 illustrate embodiments of this disclosure. Figure 4-8 As shown, those skilled in the art will recognize that the above teachings can be applied to a variety of other implementations.

[0136] In certain contexts, the features discussed herein may apply to automotive systems, safety-critical industrial applications, medical systems, scientific instruments, wireless and wired communications, radio, radar, industrial process control, audio and video equipment, current sensing, instruments (which can be highly accurate), and other digitally processed systems.

[0137] In the discussion of the above embodiments, system components, such as filters, converters, mixers, and / or other components, can be readily replaced, substituted, or otherwise modified to suit specific circuit requirements. Furthermore, it should be noted that using complementary electronics, hardware, software, etc., provides equally feasible options for implementing the teachings of this disclosure related to frequency shift PIM reduction in various communication systems.

[0138] The various systems proposed herein for achieving PIM reduction through frequency shifting may include electronic circuitry performing the functions described herein. In some cases, one or more parts of the system may be provided by a processor specifically configured to perform the functions described herein. For example, the processor may include one or more application-specific components, or may include programmable logic gates configured to perform the functions described herein. The circuitry may operate in the analog, digital, or mixed-signal domain. In some cases, the processor may be configured to perform the functions described herein by executing one or more instructions stored on a non-transitory computer-readable storage medium.

[0139] In one exemplary embodiment, any number of circuits of this figure may be implemented on a board of the relevant electronic device. The board may be a general-purpose circuit board that can accommodate various components of the internal electronic system of the electronic device and further provide connectors for other peripheral devices. More specifically, the board may provide electrical connections through which other components of the system can communicate electrically. Any suitable processor (including DSPs, microprocessors, supporting chipsets, etc.), computer-readable non-transitory storage elements, etc., may be appropriately coupled to the board based on specific configuration requirements, processing requirements, computer design, etc., and peripheral devices may be connected to the board as plug-in cards via cables or integrated into the board itself. In various embodiments, the functions described herein may be implemented in emulation form as software or firmware running within one or more configurable (e.g., programmable) elements arranged in a structure supporting these functions. The emulated software or firmware may be provided on a non-transitory computer-readable storage medium including instructions that allow a processor to perform these functions.

[0140] In another exemplary embodiment, the circuitry of this figure may be implemented as a standalone module (e.g., a device having associated components and circuitry configured to perform a particular application or function) or as a plug-in module in application-specific hardware of an electronic device. Note that specific embodiments of this disclosure may be readily included, in whole or in part, in a System-on-Chip (SOC) package. SOC stands for IC, which integrates components of a computer or other electronic system onto a single chip. It may include digital, analog, mixed-signal, and typically RF functions: all of which can be provided on a single chip substrate. Other embodiments may include a multi-chip module (MCM), in which multiple individual ICs reside within a single electronic package and are configured to interact closely with each other via the electronic package.

[0141] It must also be noted that all specifications, dimensions, and relationships outlined here (e.g., Figure 4 and Figure 7The number of components in the communication system shown is provided for illustrative and educational purposes only. This information can vary significantly without departing from the spirit of this disclosure or the scope of the appended claims. It should be understood that the system can be combined in any suitable manner. Along similar design alternatives, any of the circuits, components, modules, and elements shown in this figure can be combined in a variety of possible configurations, all of which are clearly within the broad scope of this specification. In the foregoing description, exemplary embodiments have been described with reference to specific processor and / or component arrangements. Various modifications and changes can be made to these embodiments without departing from the scope of the appended claims. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

[0142] It should also be noted that the frequency shift reduction (PIM) related functions presented herein only illustrate some possible functions that can be performed by or within a communication system. Where appropriate, some of these operations can be deleted or removed, or considerable modifications or changes can be made to these operations without departing from the scope of this disclosure. The embodiments described herein offer great flexibility, as any suitable arrangement, timing, configuration, and timing mechanism can be provided without departing from the teachings of this disclosure.

Claims

1. A system for processing a signal to be transmitted and a signal to be received, wherein the signal to be transmitted is a TX signal, the signal to be received is an RX signal, the TX signal having a first TX carrier signal component and a second TX carrier signal component, and the RX signal having an RX carrier signal component, the system comprising: One or more frequency shift circuits are configured to perform frequency shifting on one or more signal components of the RX signal and the TX signal when the difference between the center frequency of the first TX carrier signal component and the center frequency of the second TX carrier signal component is a first value, to generate a frequency-shifted output, the frequency-shifted output including: Based on the aligned RX carrier signal components, The first TX carrier signal component aligned with the first TX carrier signal component, and The second TX carrier signal component is aligned based on the second TX carrier signal component. Each of the differences between the center frequency of the aligned first TX carrier signal component and the center frequency of the aligned second TX carrier signal component, and the differences between the center frequency of the aligned RX carrier signal component and the center frequency of the aligned first TX carrier signal component, is less than the first value; and A passive intermodulation PIM estimation circuit is configured to generate an estimate of the PIM signal components to be applied to the RX signal to generate an RX signal with reduced PIM based on the frequency shift output.

2. The system of claim 1 further includes a combiner circuit configured to apply an estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

3. The system of claim 1, wherein the application estimation includes an estimation of removing the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

4. The system of claim 1 further includes one or more decimation circuits configured to decimate at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

5. The system of claim 4, wherein the one or more decimation circuits are configured to decimate at least one of the RX signal and the TX signal before the one or more frequency shift circuits perform frequency shifting to generate the frequency shift output.

6. The system of claim 4 further includes interpolation circuitry configured to interpolate the estimate of the PIM signal components before applying the estimate of the PIM signal components to the RX signal to generate an RX signal with reduced PIM.

7. The system according to any one of claims 1-6, wherein if a frequency shift to generate a frequency-shifted output is performed on the RX signal, the one or more frequency-shifting circuits are further configured to perform an inverse frequency shift on the estimation of the PIM signal components before the estimation of the PIM signal components is applied to the RX signal to generate an RX signal with reduced PIM.

8. The system according to any one of claims 1-6, wherein the difference between the center frequency of the aligned first TX carrier signal component and the center frequency of the aligned second TX carrier signal component is a second value, wherein the second value is at least twice as small as the first value.

9. The system of claim 8, wherein the difference between the center frequency of the aligned RX carrier signal component and the center frequency of the aligned first TX carrier signal component is a second value.

10. The system according to any one of claims 1-6, wherein the estimation of the PIM signal component comprises generating one or more filter coefficients of a filter configured to be applied to an RX signal to reduce the PIM signal component in the RX signal.

11. The system of claim 10, wherein the one or more filter coefficients are generated iteratively.

12. A system for reducing passive intermodulation pulse induction (PIM), the system comprising: One or more frequency shift circuits are configured as follows: The received signal is an RX signal and includes an RX carrier signal component. Receive a signal to be transmitted, said signal being a TX signal and including at least first and second TX carrier signal components, wherein the frequency interval between the first and second TX carrier components is a first value, and A frequency-shifted output is generated, comprising an RX carrier signal component, a first TX carrier signal component, and a second TX carrier signal component aligned in the spectrum, such that the frequency interval between the first and second TX carrier signal components and the frequency interval between the RX carrier signal component and the closest of the first and second TX carrier signal components are second values, wherein the second value is less than the first value; and The PIM estimation circuit is configured to generate an estimate of the PIM signal component to be applied to the RX signal to generate an RX signal with reduced PIM based on the frequency shift output.

13. The system of claim 12 further includes a combiner circuit configured to apply an estimate of the PIM signal component to the RX signal to generate an RX signal with reduced PIM.

14. The system of claim 12, wherein the application estimation includes an estimation of removing the PIM signal component from the RX signal to generate an RX signal with reduced PIM.

15. The system according to any one of claims 12-14, further comprising one or more decimation circuits configured to decimate at least one of the RX signal and the TX signal before the PIM estimation circuit generates an estimate of the PIM signal components.

16. The system of claim 15, further comprising interpolation circuitry configured to interpolate the estimate of the PIM signal components before applying the estimate of the PIM signal components to the RX signal to generate an RX signal with reduced PIM.

17. The system according to any one of claims 12-14, wherein if frequency shifting is performed on the RX carrier signal component to generate a frequency-shifted output, the one or more frequency shifting circuits are further configured to perform an inverse frequency shift on the estimation of the PIM signal component before the estimation of the PIM signal component is applied to the RX signal to generate an RX signal with reduced PIM.

18. The system according to any one of claims 12-14, wherein at least a portion of the estimation of the PIM signal components based on the frequency shift output is configured to be performed at a clock rate less than twice the frequency interval between the first and second TX carrier signal components in the TX signal.

19. A method for reducing passive intermodulation (PIM) in a received signal, the received signal being an RX signal and including an RX carrier signal component and a PIM signal component, the method comprising: When the signal to be transmitted as a TX signal includes at least first and second TX carrier signal components such that the frequency interval between the first and second TX carrier signal components is a first value, a frequency shift is performed on portions of one or more of the RX signal and the TX signal to generate a frequency-shifted output. The frequency-shifted output includes aligned RX carrier signal components and the first and second TX carrier signal components such that the frequency interval between the first and second TX carrier signal components, and the frequency interval between the RX signal component and the closest of the first and second TX carrier signal components, are a second value, wherein the second value is less than the first value. Based on the frequency shift output, an estimate of the PIM signal component to be applied to the RX signal is generated to generate an RX signal with reduced PIM.

20. The method of claim 19, wherein the applied estimation includes an estimation of removing the PIM signal component from the RX signal.

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