In-device characterization of antenna coupling

Abstract

A wireless communication device is provided with in-device capabilities for characterizing a coupling between a pair of antennas. The wireless communication device determines the coupling by operating gain measurements and by calibration gain measurements obtained through the test port.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to U.S. Patent Application Nos. 17 / 950,075 and 17 / 950,093, filed on September 21, 2022, the disclosures of which are incorporated herein by reference in their entirety as if fully set forth below and for all applicable purposes. Technical Field

[0003] The present disclosure relates generally to wireless communications and, more particularly, to wireless devices configured for in-device characterization of antenna coupling.

[0004] background

[0005] In order to achieve higher data rates in modern wireless communication systems such as fifth generation (5G) systems, cellular handsets have evolved to employ antenna arrays. Using antenna arrays has several advantages over using a single antenna. For example, when the received signal strength decreases, the signal-to-noise ratio becomes a limiting factor in the achievable data rate. But the use of multiple receive antennas enables multiple-input multiple-output (MIMO) and beamforming techniques to increase the received signal strength and therefore enhance the achievable data rate. Similarly, the use of multiple transmit antennas allows the transmitter to beamform and / or beamsteer the transmitted signal to achieve higher data rates.

[0006] As the number of transmit antennas and receive antennas in user equipment (UE) increases, the coupling between antennas may also become stronger. For example, the transmit antenna can be coupled to the receive antenna so that the transmit power is then dissipated in the low noise amplifier coupled to the receive antenna. Therefore, the coupling results in a loss of total radiated power (TRP). But each transmit and receive antenna in the UE can have a unique orientation and position within the UE, which results in different coupling levels between any two antennas. In addition, antenna coupling can change depending on how the user handles the UE. In addition, beam steering of the transmit antenna and / or receive antenna can change the coupling. Another problem related to antenna coupling is self-interference, which causes the transmit signal to affect the receiver sensitivity or couple into other transmit paths to cause mutual power amplifier distortion. Therefore, the coupling between antennas in the UE is problematic. Summary of the invention

[0007] The following summary discusses some aspects of the present disclosure to provide a basic understanding of the technology discussed. This summary is not an exhaustive overview of all the expected features of the present disclosure, and is neither intended to identify the key or important elements of all aspects of the present disclosure, nor to delineate the scope of any or all aspects of the present disclosure. The sole purpose of this summary is to present some concepts of one or more aspects of the present disclosure in a summarized form as a prelude to more specific embodiments presented later.

[0008] According to one aspect of the present disclosure, there is provided an apparatus for wireless communication, the apparatus comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; a first antenna tuner, the first antenna tuner being coupled to the first antenna; a second antenna tuner, the second antenna tuner being coupled to the second antenna; a transmitter; a receiver; an antenna switch array, the antenna switch array having a first configuration, in which the transmitter is coupled through the antenna switch array to drive the first antenna through the first antenna tuner, and in which the second antenna tuner is coupled to a receiver node; a first switch, the first switch being coupled between the receiver node and a receive path in the receiver; and a second switch, the second switch being coupled between the receiver node and a matching load.

[0009] According to another aspect of the present disclosure, a user equipment (UE) for wireless communication is provided, the UE comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; a transmitter, the transmitter comprising a transmit path; a receiver, the receiver comprising a receive path; a transmit line; and a plurality of switches, the plurality of switches being configurable to enter a first configuration, in which the transmit path is coupled to the receive path via the transmit line, and in which the first antenna and the second antenna are isolated from the transmit path and the receive path, and the plurality of switches being configurable to enter a second configuration, in which the transmit path and the receive path are coupled to respective antennas of the first antenna and the second antenna, and in which the transmit line is isolated from the transmit path and the receive path.

[0010] According to another aspect of the present disclosure, there is provided an apparatus for wireless communication, the apparatus comprising: a plurality of antennas, including a first antenna and a second antenna; a transmitter, the transmitter comprising a transmit path; a receiver, the receiver comprising a receive path; an antenna switch array, the antenna switch array being configurable to enter a first configuration, in which the transmit path is coupled through the antenna switch array to drive the first antenna, and in which the receiver is coupled through the antenna switch array to receive from the second antenna; and a controller, the controller being configured to measure an operating gain between the transmit path and the receive path when the antenna switch array is in the first configuration, the controller being further configured to estimate a coupling gain between the first antenna and the second antenna based on the operating gain, a calibrated transmit gain of the transmit path, and a calibrated receive gain of the receive path.

[0011] According to another aspect of the present disclosure, a method for wireless communication is provided, the method comprising: sending a first signal to a first antenna of a user equipment through a transmitter chain; changing the load of a second antenna of the user equipment by each of a first plurality of load values ​​during the transmission of the first signal; measuring a reflection coefficient of the transmitter chain for each of the first plurality of load values ​​to provide a first plurality of measured reflection coefficients during the transmission of the first signal; and calculating a first coupling factor between the first antenna and the second antenna based on the first plurality of measured reflection coefficients and the first plurality of load values.

[0012] After studying the description of the specific exemplary implementation of the present disclosure below in conjunction with the accompanying drawings, other aspects, features and implementations of the present disclosure will be apparent to those of ordinary skill in the art. Although the features of the present disclosure may be discussed below with respect to certain implementations and the accompanying drawings, all implementations of the present disclosure may include one or more of the advantageous features discussed herein. In other words, although one or more implementations are discussed as having certain advantageous features, one or more of such features may also be used according to the various implementations of the present disclosure discussed herein. In a similar manner, although exemplary implementations may be discussed below as device, system or method implementations, it should be understood that such exemplary implementations may be implemented in various devices, systems and methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to further illustrate various specific implementations and explain various principles and advantages according to the present disclosure. In the accompanying drawings, the same figure numbers refer to the same or functionally similar elements throughout the individual views, and the accompanying drawings are incorporated into the specification together with the following specific embodiments and form a part of the specification.

[0014] Figure 1An example of a system for wireless communications that supports in-device antenna coupling characterization in accordance with aspects of the present disclosure is illustrated.

[0015] Figure 2 An example subframe structure including a sounding reference signal for in-device antenna coupling characterization in accordance with aspects of the present disclosure is illustrated.

[0016] Figure 3A is a diagram of user equipment supporting antenna tuner based in-device antenna coupling characterization in accordance with aspects of the present disclosure.

[0017] Figure 3B yes Figure 3A Flow chart of a method of operating a user equipment.

[0018] Figure 4A is a diagram of a user equipment supporting calibration path based in-device antenna coupling characterization in accordance with aspects of the present disclosure.

[0019] Figure 4B yes Figure 4A Flow chart of a method of operating a user equipment.

[0020] Figure 5A is a diagram of a user equipment supporting calibrated gain based in-device antenna coupling characterization in accordance with aspects of the present disclosure.

[0021] Figure 5B yes Figure 5A Flow chart of a method of operating a user equipment.

[0022] Fig. 6A is a diagram of a user equipment using a feedback receive path to support calibration gain based in-device antenna coupling characterization in accordance with aspects of the present disclosure.

[0023] Figure 6B yes Fig. 6A Flow chart of a method of operating a user equipment. DETAILED DESCRIPTION

[0024] The following detailed description is intended as a description of various configurations and is not intended to represent the only configuration in which the concepts described herein may be practiced. In order to provide a comprehensive understanding of the various concepts, the specific embodiments include specific details. However, it is apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, in order to avoid obscuring such concepts, known structures and components are shown in block diagram form.

[0025] A wireless communication device (e.g., user equipment (UE)) is provided with a built-in or in-device antenna coupling characterization. Generally speaking, in order to characterize the antenna coupling in an antenna array, the UE can be modified so that a transmit line (e.g., a coaxial cable) is soldered to each antenna port. A vector network analyzer (VNA) can then be coupled to the coaxial cable to characterize the antenna coupling across the array. The problem with this measurement is that soldering the coaxial cable can be cumbersome and invasive. In addition, it can be difficult to avoid antenna-to-cable coupling that contaminates the desired antenna-to-antenna coupling measurement. The in-device characterization disclosed herein avoids the need for such complexity and inaccuracy. Several specific implementations that provide in-device antenna coupling characterization will now be introduced and are also discussed further herein.

[0026] In the first specific implementation of the in-device characterization also represented herein as antenna tuner-based, a transmitter transmits a signal through a first antenna in an antenna array, and an antenna tuner coupled to a second antenna in the array is sequentially set to different loads. At each load, a directional coupler in a transmission path between a power amplifier in the transmitter and the first antenna samples a forward signal and a reflected signal. The forward signal is a signal intended to be transmitted by the first antenna when the signal propagates on the transmission path from the power amplifier to the first antenna. The reflected signal is a portion of the forward signal that is reflected from the first antenna and propagates from the first antenna to the power amplifier via the transmission path. The signal detector detects samples of the forward signal and the reflected signal at each load value of the tuner of the second antenna, so that the controller can form a ratio of the detected reflected signal sample to the detected forward signal sample. The controller therefore determines a reflection coefficient (a ratio of the detected reflected signal sample to the detected forward signal sample) for each of the load values ​​of the tuner of the second antenna.

[0027] The port of the first antenna and the port of the second antenna can be considered to form a two-port network. There are four scattering parameters in such a two-port network. The first scattering parameter S 11 Indicates how much power is reflected from the first port. The second scattering parameter S 22 Indicates how much power is reflected from the second port. The third scattering parameter S 21 Indicates how much power is coupled from the first port to the second port, and the fourth scattering parameter S 12 Indicates how much power is coupled from the second port to the first port. Scattering parameter S 21 With S 12 are equal because the first and second antennas are passive structures. Therefore, there are three unknown scattering parameters that can be determined to fully characterize the two-port network: S 11 , S 22 and S 21Based on the three reflection coefficients and the three known loads, the controller can calculate the three scattering parameters. Advantageously, the antenna tuner that sets the loads for the second antenna is adjacent to the port of the second antenna and can have a relatively low insertion loss. The tuner of the second antenna can thus set a relatively extreme impedance (towards the unit circle when plotted on a Smith chart). The three loads of the tuner of the second antenna can thus be used to recover the relatively weak scattering parameter S 21 The antenna coupling is done by S 21 In the described scenario, the UE can then tune or detune its antenna as necessary.

[0028] In a second specific implementation also represented herein as a characterization within a calibration path device, the UE may cycle through a gain detection mode and a reflection coefficient mode to calculate the scattering parameters of the pair of antennas. In both modes, the corresponding tuners for the first antenna and the second antenna are tuned to achieve good power transfer, such as established by open circuit, short circuit and load (OSL) calibration. As in the first specific implementation, the port to the first antenna is coupled to the corresponding antenna tuner. Similarly, the port to the second antenna is coupled to the corresponding antenna tuner. The transmit path and receive path of the UE are coupled to the corresponding selected antennas in the first antenna and the second antenna through the antenna switch array. In the first configuration of the antenna switch array represented herein as a straight-through configuration, the transmit path is coupled to the first antenna, and the receive path is coupled to the second antenna. In the second configuration of the antenna switch array represented herein as a cross configuration, the transmit path is coupled to the second antenna, and the receive path is coupled to the first antenna.

[0029] The UE includes a calibration path or a transmission line that can be selected by a corresponding calibration path switch during a gain detection mode so that the transmission path is isolated from the first antenna and coupled to the calibration path instead. The second antenna is then isolated from the receiving path of a low noise amplifier (LNA) in a receiver that would otherwise couple the second antenna to the UE. During the gain detection mode, the antenna switch array is in a pass-through configuration. During the first gain detection in the gain detection mode, the calibration path is coupled between the transmission path and the receiving path, while the first antenna is isolated from the second antenna. The UE can therefore determine a calibration gain as defined by the ratio of a baseband receive signal recovered from an RF signal received via the receiving path to a baseband transmit signal converted into an RF signal during the calibration mode, and the baseband transmit signal is then propagated along the transmission path to the first antenna. When the calibration path is not selected from the ratio of the baseband receive signal to the baseband transmit signal, the UE can similarly determine the coupling gain.

[0030] During the reflection coefficient mode, the directional coupler in the transmit path functions similarly to that discussed with respect to the specific implementation based on the antenna tuner, so that the reflection coefficient can be measured. The calibration path is not used during the reflection coefficient mode. The calibration path is therefore isolated from the transmit path and the receive path. In the first reflection coefficient measurement, the antenna switch array is in a straight-through configuration. In the second reflection coefficient measurement, the antenna switch array is in a cross configuration. Based on the two gain measurements of the gain detection mode and the two reflection coefficient measurements of the reflection coefficient mode, the UE can determine the scattering parameters, including S21. The determination of the resulting scattering parameters is very advantageous because it de-embeds the effect of the antenna tuner. In this regard, the calibration path is upstream of the antenna tuner so that when the calibration path is selected, the antenna tuner is isolated from the gain measurement. With respect to this isolation, it is advantageous if the calibration path coupled to the transmit and receive paths occurs between the antenna switch array and the antenna tuner, making the de-embedding more accurate. However, in an alternative specific implementation, the calibration path may be upstream of the antenna switch array.

[0031] In a third specific implementation, also denoted herein as in-device characterization based on gain calibration, a transmit chain and a receive chain (or a feedback receive chain) are calibrated using test equipment at a test connector, such as just upstream of an antenna tuner at an antenna port. The transmit calibration gain measurement measures the calibrated transmit gain between a baseband transmit signal and a resulting signal at the transmit test port. The receive calibration gain measurement measures the calibrated receive gain between a baseband receive signal at a receiver and a receive test port. During normal operation of the UE following these calibration measurements, the UE converts a transmit baseband signal into an RF signal, transmits the RF signal via a first antenna, receives a coupled RF signal via a second antenna, and converts the coupled RF signal into a baseband receive signal, so that an operating gain as defined by a ratio of a baseband receive signal to a baseband transmit signal can be determined. Based on the operating gain, the calibrated receive gain, and the calibrated transmit gain, the UE can estimate the coupling between the first antenna and the second antenna.

[0032] To provide a deeper understanding of the advantageous properties of the intra-device antenna coupling characterization disclosed herein, aspects of the disclosure are first described with respect to an example wireless communication system. Figure 1An example wireless communication system 100 that supports in-device antenna coupling characterization is illustrated. The wireless communication system 100 includes a base station 105, a UE 115, and a core network 130. In some examples, the wireless communication system 100 may be a long term evolution (LTE) network, an advanced LTE (LTE-A) network, an LTE-A Pro network, or a new radio (NR) network. In some cases, the wireless communication system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission-critical) communications, low-latency communications, or communications with low-cost and low-complexity devices. The techniques described herein may be applicable to positioning in 5G NR and future releases, and / or may be applicable to detection of users of UE 115.

[0033] The base station 105 may communicate wirelessly with the UE 115 via one or more base station antennas. The base station 105 described herein may include or may be referred to by those skilled in the art as a base station transceiver, a wireless base station, an access point, a wireless transceiver, a node B, an evolved node B (eNB), a next generation node B or a giga node B (any of which may be referred to as a gNB), a home node B, a home evolved node B, or some other appropriate terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macro cell base stations or small cell base stations). The UE 115 described herein is capable of communicating with various types of base stations 105 and network equipment (including macro eNBs, small cell eNBs, gNBs, relay base stations, etc.), and / or is capable of communicating directly with each other.

[0034] Each base station 105 may be associated with a geographic coverage area 110, supporting communications with various UEs 115 in the particular geographic coverage area 110. Each base station 105 may provide communication coverage for the respective geographic coverage area 110 via a communication link 125, and the communication link 125 between the base station 105 and the UE 115 may utilize one or more carriers. The communication link 125 shown in the wireless communication system 100 may include an uplink transmission from the UE 115 to the base station 105, or a downlink transmission from the base station 105 to the UE 115. Downlink transmissions may also be referred to as forward link transmissions, and uplink transmissions may also be referred to as reverse link transmissions.

[0035] One or more of UE 115 supports in-device antenna characterization, as will be further explained herein. Each UE 115 may be dispersed throughout the wireless communication system 100, and each UE 115 may be stationary or mobile. UE 115 may also be referred to as a mobile device, a wireless communication device, a remote device, a handheld device, or a subscriber device, or some other appropriate term, wherein "device" may also be referred to as a unit, a station, a terminal, or a client. UE 115 may also be a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communication (MTC) device, etc., which may be implemented in various items such as electrical appliances, vehicles, meters, etc.

[0036] Some UEs 115 (such as MTC or IoT devices) may be low-cost or low-complexity devices and may provide automated communications between machines (e.g., via machine-to-machine (M2M) communications). M2M communications or MTC may refer to data communications technology that allows devices to communicate with each other or with a base station 105 without human intervention. In some examples, M2M communications or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay the information to a central server or application that may utilize the information or present the information to a person interacting with the program or application. Some UEs 115 may be designed to collect information or implement automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

[0037] The base stations 105 may communicate with the core network 130 and with each other. For example, the base stations 105 may interface with the core network 130 via a backhaul link 132 (e.g., via S1, N2, N3, or other interface). The base stations 105 may communicate with each other directly (e.g., directly between the base stations 105) or indirectly (e.g., via the core network 130) over a backhaul link 134 (e.g., via X2, Xn, or other interface).

[0038] The wireless communication system 100 may operate using one or more frequency bands, such as in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). The 300 MHz to 3 GHz region is referred to as the ultra-high frequency (UHF) region or decimeter band because the wavelengths are in the range of about one decimeter to one meter long. UHF waves may be blocked or redirected by buildings and environmental features. However, these waves may penetrate various structures sufficiently so that macro cells provide services to UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 km) than transmission using smaller frequencies and longer wavelengths in the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

[0039] The wireless communication system 100 may also operate in the Super High Frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as centimeter bands. The SHF region includes frequency bands that may be opportunistically used by devices that may be able to tolerate interference from other users, such as the 5 GHz Industrial, Scientific, and Medical (ISM) band.

[0040] The wireless communication system 100 may also operate in the extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz or higher), which is also referred to as the millimeter wave band (which may also include some frequencies in the 20 GHz range in some systems). In some examples, the wireless communication system 100 may support millimeter wave (mmW) communications between the UE 115 and the base station 105, and the EHF antennas of the corresponding devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate the use of antenna arrays within the UE 115. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions.

[0041] Each UE 115 is equipped with multiple antennas, which can be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication or beamforming. For example, the wireless communication system 100 can use a transmission scheme between a transmitter device (e.g., a base station 105 in a downlink) and a receiver device (e.g., a UE 115 in a downlink), wherein the transmitter device is equipped with multiple antennas and the receiver device is equipped with one or more antennas. MIMO communication can use multipath signal propagation to increase spectral efficiency by sending or receiving multiple signals via different spatial layers, which can be referred to as spatial multiplexing. The multiple signals can be sent, for example, by the transmitter device via different antennas or different combinations of antennas. Similarly, the multiple signals can be received by the receiver device via different antennas or different combinations of antennas. Each of the multiple signals can be referred to as a separate spatial stream and can carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers can be associated with different antenna ports for channel measurement and reporting. MIMO technology includes single-user MIMO (SU-MIMO), in which multiple spatial layers are transmitted to the same receiving device, and multi-user MIMO (MU-MIMO), in which multiple spatial layers are transmitted to multiple devices.

[0042] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that may be used at a sender device or a receiver device (e.g., a base station 105 or a UE 115) to shape or direct an antenna beam (e.g., a transmit beam or a receive beam) along a spatial path between the sender device and the receiver device. Beamforming may be achieved by combining signals communicated via antenna elements of an antenna array so that signals propagating at some orientations relative to the antenna array experience constructive interference, while other signals experience destructive interference. Adjustments to signals communicated via antenna elements may include the sender device or the receiver device applying one or more amplitude and phase offsets to signals carried via each antenna element associated with the device. Adjustments associated with each antenna element may be defined by a set of beamforming weights associated with an orientation (e.g., relative to the antenna array of the sender device or the receiver device, or relative to some other orientation).

[0043] The communication between the UE 115 and the base station 105 can be divided into subframes (SFs) in the time domain. Figure 2 , illustrates an example SF 200 that allocates multiplexed sounding reference signals (SRS). In one embodiment, the subframe structure 200 operates within a short time frame of approximately 500 microseconds, but it can also be shorter or longer than that. The short time frame allows the base station 105 to essentially "freeze" the channel state for the duration of the subframe to minimize the effects of channel decorrelation.

[0044] The in-device antenna coupling characterization described herein is not limited to any particular type of transmit signal. The following discussion of using SRS as a transmit signal for use during in-device antenna coupling characterization is therefore merely exemplary. However, since SRS in 5G systems are sequenced by each TX and RX antenna, it is convenient to use SRS as a transmit signal during in-device antenna coupling characterization. If in-device antenna coupling characterization calculations are performed during SRS transmission, no additional delay needs to be added for in-device antenna coupling characterization compared to conventional SRS operation.

[0045] For the sake of illustration, Figure 2 200; as will be appreciated, the structure of the SF 200 may be extended to any number of subframes as needed or desired. Each SF 200 includes a plurality of time slots 206, each time slot 206 including a plurality of orthogonal frequency division multiplexing (OFDM) symbols. Each time slot 206 in the SF 200 may be divided into an uplink portion 202 and a downlink portion 204 separated by a transition portion U / D. As part of the uplink portion 202, the UE 115 may send various types of signals to the base station 105. These may include, for example, SRS, uplink data, and optionally a request for information (e.g., in an uplink burst). A transition portion U / D is provided between the uplink portion 202 and the downlink portion 204. During the downlink portion 204, the base station 105 sends various types of signals to the UE 115, including, for example, a user equipment reference signal (UERS) and downlink data (e.g., in a downlink burst). In some embodiments, the base station 105 can use the SRS in the UL portion 202 to derive information that facilitates the downlink between the UE 115 and the base station 105. For example, the base station 105 can train its antenna based on the SRS to beamform downlink data sent back to the UE 115 so that, for example, interference with other UEs within range of the base station 105 is reduced.

[0046] Within a time slot 206, the SRS may span one, two, or four consecutive OFDM symbols within the last six OFDM symbols of the time slot 206. Each antenna may transmit its own SRS so that the sounding reference signal is multiplexed across the antennas of the UE, each antenna having its own SRS in the corresponding time slot 206. Each slot 206 may include a first cyclic prefix (CP) appended to the OFDM symbol of the multiplexed SRS. Each slot 206 may also include a second CP appended to a guard period before the next slot begins. The guard period ensures that the UE 115 has enough time to perform SRS antenna switching. Figure 2The timing of SRS antenna switching and the characterization of in-device antenna coupling are also illustrated. At the beginning of slot 206, the SRS switching antenna switch is configured to couple the transmitter path to the selected antenna in preparation for sending the multiplexed SRS. When the selected antenna begins to send the multiplexed SRS, the in-device antenna coupling characterization is also performed ("ON"). In some specific implementations, the duration of the in-device antenna coupling characterization of a pair of coupled antennas is shorter than the transmission of the multiplexed SRS by the transmitting antenna, so that the calculation is completed before the start of the second CP attached to the protection period ("OFF"). The in-device antenna coupling characterization of another pair of coupled antennas (or the same pair) begins with the transmission of subsequent multiplexed SRS. For example, the first SRS transmission on the OFDM symbol in the first slot 206 can be used to determine the coupling between the first pair of antennas, the second SRS transmission in the second slot 206 can be used to determine the coupling between the second pair of antennas, and so on. In some examples, the first pair of antennas and the second pair of antennas can share a common antenna.

[0047] Figure 2 The four slots 206 shown in are for illustrative purposes and not for limitation. The number of SRS transmissions for in-device antenna coupling characterization may be greater or less than four SRS transmissions in sequence depending on the number of antennas that need to be detuned in UE 115. In addition, the multiplexed SRS transmission sequence and the corresponding in-device antenna coupling characterization may be repeated over time depending on the desired in-device antenna coupling characterization update or refresh. Repeated SRS transmissions also allow UE 115 to collect optimal detuning settings for the same antenna multiple times at different repetition slots 206, and average these values ​​to provide improved detuning. In slot 206, the multiplexed SRS may be the same for each antenna. Alternatively, the multiplexed SRS may be unique for each antenna, so that the base station 105 can identify which antenna is sending the corresponding received SRS. In-device antenna coupling characterization may be performed in sequential time slots as shown, or may be performed discontinuously or only in certain selected time slots (e.g., based on determining that updating one or more parameters between a certain antenna pair would be beneficial). Some example UE architectures for in-device antenna coupling characterization will now be discussed in more detail.

[0048] Example UE architecture for in-device antenna coupling characterization based on antenna tuners

[0049] As previously discussed, antenna tuner-based in-device characterization of coupling between a first antenna and a second antenna involves sending a signal via the first antenna while sequentially setting an antenna tuner coupled to a second antenna in the array to different impedances or loads. Figure 3AAn example UE 300 with antenna coupling based antenna tuner in-device characterization is shown in FIG. The transceiver 302 includes a transmitter 330 and a receiver 332 and a data processor 310 (which may be implemented as a modem in some configurations). The transmitter 330 includes a transmit path or chain starting at a digital-to-analog converter (DAC) 334 for converting a baseband digital transmit (TX) signal 336 into a baseband analog output signal. One or more up-conversion mixers 338 in the transmit chain mix the baseband analog output signal with an RF carrier generated from a local oscillator (LO) generator 340 to convert the baseband analog output signal into a modulated RF signal. The power amplifier 328 in the transmit chain amplifies the modulated RF signal and sends the amplified modulated RF signal to the antenna switch array 320.

[0050] As previously discussed, the antenna switch array 320 can be configured to enter a straight-through configuration or to enter a crossover configuration. In the straight-through configuration, the transmit chain passes through the antenna switch array 320 to the antenna tuner 306a for the first antenna 304a. In the crossover configuration, the transmit chain passes through the antenna switch array to the antenna tuner 306b for the second antenna 304b. Additional antennas (not illustrated) can be selectively coupled to the transmit chain (and / or receive chain, discussed below) by the antenna switch array 320. The antenna switch array 320 can be included in a single circuit (e.g., an IC), or its components can be distributed over several circuits or on a board or substrate.

[0051] In the pass-through configuration, the receive chain couples the received RF signal from the second antenna 304b to the receiver node 341 via the antenna tuner 306b and via the antenna switch array 320. Switch SW1 is coupled between the receiver node 341 and the receiver 332. In addition, switch SW2 is coupled between the receiver node 341 and the matching load 362 (e.g., 50Ω). In some examples, switches SW1 and SW2 are included in an antenna switch module (ASM). During in-device characterization based on the antenna tuner, switch SW1 may be opened and switch SW2 closed to couple the receive path to the matching load 362. During normal operation when in-device characterization is not active, switch SW1 is closed and switch SW2 is opened to couple the received RF signal to the filter 352 (e.g., a bandpass filter) in the receiver 332. The low noise amplifier (LNA) 322 in the receive chain amplifies the filtered received RF signal from the filter 352. One or more downconverter mixers 354 in the receive chain mix the amplified RF signal from the LNA 322 with an RF carrier generated by the LO generator 356 to convert the amplified RF signal to a baseband analog signal. The receive chain ends at an analog-to-digital converter (ADC) 358 that converts the baseband analog signal to a baseband receive (Rx) digital signal 360.

[0052] The antenna tuners 306a and 306b may each be formed by an impedance tuner 307 and / or an antenna aperture tuner 308. The following discussion will assume that the antenna tuner-based in-device characterization is performed using the antenna switch array 320 in a straight-through configuration, but it should be understood that a crossover configuration may also be used. The transmitter 330 may then drive the RF signal into the first antenna 304a while its antenna tuner 306a is tuned to achieve good power transfer (e.g., a voltage standing wave ratio (VSWR) of 2 or less). The controller 318 in the data processor 310 controls the antenna switch array 320, the antenna tuners 306a and 306b, and the switches SW1 and SW2 during the antenna tuner-based in-device characterization.

[0053] To measure the reflection coefficient when characterizing activity within an antenna tuner-based device, the UE 300 includes a directional coupler 364 coupled to a portion of the transmit path power amplifier 328 and the antenna switch array 320. The directional coupler 364 samples the forward signal (RF signal for transmission) propagating from the power amplifier 328 to the antenna 304a, and also samples the reflected signal reflected from the antenna 304a back to the power amplifier 328. The signal detector 374 detects the forward signal and the reflected signal so that the controller 318 can determine the ratio of the reflected signal to the forward signal to form an input reflection coefficient 376. The reflection coefficient can also be expressed as Γ IN In one implementation, the directional coupler 364 may sample both the amplitude and phase of the forward signal and the reflected signal so that Γ IN is a complex number. In other specific implementations, the directional coupler 364 may only sample the magnitude of the forward signal and the reflected signal, so that Γ IN is a real number. A smaller input reflection coefficient translates into a better match for the transmit antenna. For example, Γ IN =0 means no reflected power.

[0054] The directional coupler 364 can receive a forward RF signal at a first port P1, provide an output RF signal at a second port P2, and provide a sample of the forward signal at a third port P3. The directional coupler 364 can also provide a sample of the reflected RF signal at a fourth port P4. The signal detector 374 can be a square-law power detector, a phase and magnitude signal detector, or another suitable type of signal detector. In some specific implementations, the detector 374 forms a feedback receiving path that down-converts the sampled signal from the directional coupler 364 and digitizes it to the baseband. In this way, the detector 374 can receive RF signals at different ports of the directional coupler 364, and can measure the voltage, current, power and / or other characteristics of the RF signal. The detector 374 can be coupled to the third port and the fourth port through the switch 366. The detector 374 can measure the forward signal propagated to the antenna switch array 320 or the reflected signal from the antenna switch array 320 based on the state of the switch 366. The switch 366 can be a "2" pole "2" throw (DPDT) switch. In one state, switch 366 connects the antenna side of coupler 364 to a terminating impedance (e.g., a 50Ω load) and connects the amplifier side of directional coupler 364 to detector 374. In another state, switch 366 connects the antenna side of directional coupler 364 to detector 374 and connects the amplifier side of directional coupler 364 to the terminating impedance.

[0055] By using one directional coupler 364 in conjunction with a switch 366, a single directional coupler may be used instead of two directional couplers to perform signal measurements on the transmit line as described herein, although other configurations may also be implemented. In the example shown, the switch 366 changes the connection on the directional coupler 364 to allow measurements in either direction, i.e., measurements of signals from the PA 328 and measurements of signals reflected back from the transmit antenna in the antenna, such as during transmission of an SRS or other suitable signal.

[0056] During transmission from the first antenna 304a, when the switch 366 is set to the first state, the directional coupler 364 generates a voltage V representing the forward signal. f When the switch 366 is set to the second state, the directional coupler 364 generates a voltage V indicating the reflected signal. r More specifically, when the switch 366 is configured such that the fourth port P4 of the directional coupler 364 is coupled to the terminating impedance and the third port P3 of the directional coupler 364 is fed into the detector 374, the voltage V indicating the forward signal is measured. f Since power is a function of voltage and current, the voltage V fConversely, when the switch 366 is configured such that the fourth port P4 of the directional coupler 364 is connected to the detector 374 and the third port P3 of the directional coupler 364 is coupled to the terminating impedance, a voltage V indicating the reflected signal is measured. r Voltage V r Proportional to reverse power.

[0057] In determining the voltage V f and voltage V r Afterwards, the ratio V can be determined r / V f As described in this article, a single directional coupler can be used to generate a voltage V r and V f Voltage V r and V f Proportional to the forward power and reflected power respectively. Ratio V r / V f The input reflection coefficient Γ is defined as in the following formula (1): IN :

[0058] Γ IN＝ V r / V f Formula (1)

[0059] Input reflection coefficient Γ IN It can be used to determine other quality factors that describe the RF channel, such as the voltage standing wave ratio (VSWR). The VSWR is given by the following formula (2):

[0060] VSWR=(1+ |Γ IN │) / (1- │Γ IN │) Formula (2)

[0061] In some implementations, the detector 374 can detect the f and V r The input reflection coefficient Γ is calculated by measuring IN and / or other quality factors (eg, VSWR), and reports the calculated results to the data processor 310 under the control of the controller 318. Alternatively, the controller 318 may calculate the input reflection coefficient Γ IN In some implementations, the detector 374 includes a circuit for detecting V r and V f The analog-to-digital converter (ADC) measures the digitized voltage and provides its digitized value. r and V f The digitized value of can be sent to the data processor 310. The circuit within the data processor 310 can store the information so that the input reflection coefficient Γ can be calculated.IN and / or other quality factors.

[0062] Γ IN Smaller values ​​of indicate fewer reflections and better matching between the antenna and the radio (or the antenna and the transmission line). From the above formula (1), it can be determined that the lowest possible value of the input reflection coefficient is 0. When the input reflection coefficient is 0, no reflection occurs, that is, the antenna and the radio or the antenna and the transmission medium are perfectly matched. When Γ IN When it is 0, no power is reflected. As the reflection at the interface increases, Γ IN The antenna tuner 306a can be tuned accordingly by the controller 318 to reduce the input reflection coefficient. IN Both the magnitude and phase components of can improve the tuning process.

[0063] However, Γ IN Minimization may not directly translate into maximizing the total radiated power from antenna 304a, since the transmitted power may be coupled to other antennas and dissipated in circuits such as LNA 322 rather than radiated into free space. Therefore, in order to better detune the coupled antenna, the input reflection coefficient Γ is obtained separately. IN The antenna tuner-based in-device characterization disclosed herein advantageously determines scattering parameters between a transmit antenna and a coupled receive antenna so that detuning of the coupled receive antenna can be improved.

[0064] The operation of the data processor 311 based on the input reflection coefficient Γ will now be discussed in more detail. IN Calculating Scattering Parameters. To calculate the scattering parameters, controller 316 sets antenna tuner 306b for antenna 304b to a first impedance value and performs a first measurement of the input reflection coefficient when antenna switch array 320 is in a through configuration and switch SW2 is on and switch SW1 is off. With the switches remaining in the same configuration, antenna tuner 306b is set to a second impedance value and a second measurement of the input reflection coefficient is performed. Finally, antenna tuner 306b is set to a third impedance value and a third measurement of the input reflection coefficient is performed with the switches remaining in the same configuration. Based on these three measurements, data processor 310 calculates scattering parameter S 11 , S 22 , S 21 and S 12 These measurements may be performed sequentially using a separate reference signal. Alternatively, if the reference signal transmission duration is sufficient, all measurements may be performed during a single reference signal transmission. With respect to this calculation, the impedance of the antenna tuner 306 b determines the load reflection coefficient Γ L, which is a function of the impedance of the antenna tuner 306b and the characteristic impedance. The impedance of the antenna tuner 306b can therefore be converted into a load reflection coefficient by the data processor 310. Then, the calculation of the scattering parameters can be based on the input reflection coefficient Γ IN and the load reflection coefficient Γ L The relationship between is given by the following formula (3):

[0065]

[0066] S parameter 11 , S 22 Sum product S 12 *S 21 Describe the two-port channel between TX antenna 304a and RX antenna 304a. To simplify the notation, input the reflection coefficient Γ IN It can also be expressed as M (shorthand for the measurement of the input reflection coefficient), and the load reflection coefficient Γ L is denoted as L. Therefore, formula (3) yields the following formula (4):

[0067] M=S 11 +MLS 22 +L(S 12 S 21 -S 11 S 22 ) Formula (4)

[0068] The controller 318 can thus calculate a first input reflection coefficient measurement M1, where the antenna tuner 306b is configured to provide a first loaded reflection coefficient L1. Similarly, a second measurement value M2 is measured using a second loaded reflection coefficient L2. Finally, a third measurement value M3 is measured using a third loaded reflection coefficient L3. Based on the values ​​M1, M2, M3, L1, L2, and L3, the controller 318 can solve the corresponding three versions of equation (4) to determine the three unknown quantities S 11 , S 22 and S 12 *S 21 Then we can get the value from (S 12 *S 21 ) determines the scattering coefficient S 21 (or S 12 ).

[0069] These three versions of formula (4) can be written in matrix form as shown in formula (5) below:

[0070]

[0071] Where Δ=S 13 S 21 -S 11S 22 .

[0072] Therefore, the controller 318 may calculate the two-port S-parameters using a method of solving three linear equations with three unknowns. Once the two-port S-parameters are calculated, the two-port channel represented by the two-port S-parameters is characterized.

[0073] When the controller 318 obtains the values ​​of M1, M2 and M3 corresponding to the loads L1, L2 and L3, it can solve formula (5) to obtain the scattering parameters describing the two-port channel from the transmitting antenna 304a to the receiving antenna 304b. Since the two-port channel is characterized, the controller 318 can further calculate the optimal load of the antenna 304b to be most effectively detuned. In addition to tuning the antenna 304b, as an alternative to the iterative control of the antenna tuners 306a and 306b with relatively large hysteresis, the tuner states of the antenna tuners 306a and 306b can be adjusted to avoid instability. In addition, the characterization of the scattering parameters can be used by the controller 318 for dynamic control of filters such as the filter 352 and for dynamic control of the bias of the power amplifier 328 and the low noise amplifier 322. At the end of the characterization mode before the operating mode, the detuning controller 318 can set the antenna tuner 306b to the optimal load or to the value in the tunable range that is closest to the optimal load. The coupling between antennas 304a and 304b is thus advantageously minimized or reduced such that the total radiated power from UE 300 is increased or maximized when antenna 304a transmits during the operating mode.

[0074] The antenna tuner based in-device characterization can be repeated with the antenna switch array 320 in a crossover configuration so that it is antenna 304b that transmits and antenna 304b that receives. Antenna tuner 306b will be set for good power transfer (e.g., VSWR of 2 or less) while antenna tuner 306a cycles through three different load settings while the corresponding input reflection coefficients are determined by controller 318. Controller 318 can then use the scattering parameter S of antenna switch array 320 in a straight-through configuration. 21 The calculation and use of S of the antenna switch array 320 in the cross configuration 21 Calculation average.

[0075] Now about Figure 3BThe flowchart of describes an example of an antenna tuner-based in-device characterization of antenna coupling. The method begins with an action 311 of sending a signal to a first antenna of a user equipment through a transmitter chain. Sending a signal such as an SRS through a transmission chain of a UE 300 having an antenna switch array 320 in a straight-through configuration or a crossover configuration is an example of action 311. The method also includes an action 312 of changing the load of a second antenna of the user equipment by each of a plurality of load values ​​during the transmission of the signal. If action 311 occurs in a straight-through configuration, an example of action 312 is setting the antenna tuner 306b to one of three different load values. If action 311 occurs in a crossover configuration, an example of action 312 is setting the antenna tuner 306a to three different load values. The method also includes an action 313 of measuring a reflection coefficient of the transmitter chain for each of a plurality of load values ​​to provide a plurality of measured reflection coefficients during the transmission of the signal. The measurement of the reflection coefficient at the directional coupler 364 is an example of action 313. Finally, the method includes an act 314 of calculating a coupling factor between the first antenna and the second antenna based on the plurality of measured reflection coefficients and the plurality of load values. Solving equation (5) for a through configuration or a crossover configuration by the controller 318 is an example of act 314. While the use of three known loads is described with respect to certain examples above in order to calculate a certain set of scattering parameters, a greater (e.g., when in a configuration with more than two ports and / or more than three unknown scattering parameters) or lesser (e.g., when certain parameters are already known or characterized by another method or process) number of known loads may be implemented and / or utilized.

[0076] The accuracy and precision of scattering parameter characterization using antenna tuner-based techniques are affected by the impedance and losses of components such as antenna tuners 306a and 306b. But directly measuring antenna scattering parameters requires soldering test cables to the ports of antennas 304a and 304b, as discussed previously. The use of tuner open, short, and load calibrations allows the UE to de-embed the effects of intervening components such as antenna tuners in an in-device characterization based on a calibration path when the forward and reflected signals are sampled at the directional coupler. Therefore, the in-device characterization based on a calibration path provides the accuracy of the test cable approach without the invasive and expensive method of soldering the test cables and then separating them. An example UE architecture for in-device characterization based on a calibration path will now be discussed.

[0077] Example UE architecture for in-device antenna coupling characterization based on calibration path

[0078] exist Figure 4A4 shows an example UE 400 with in-device characterization based on a calibration path. The transceiver 302, antennas 304a and 304b, and antenna tuners 306a and 306b are as discussed for the UE 300. The data processor 410 generates a baseband digital transmit (Tx) signal 336 for the transmit chain in the transceiver 302, as discussed for the data processor 310. Similarly, the data processor 410 receives a baseband digital receive (Rx) signal 360 from the receive chain in the transceiver 302.

[0079] In order to de-embed the effect of the antenna tuners 306a and 306b on the scattering parameter characterization, a selectable calibration path (e.g., a transmission line) 409 can be selectively coupled between the transmit port and the receive port of the antenna switch array 320. The calibration path 409 has a characteristic impedance (e.g., 50Ω) that matches the desired characteristic impedance of the transmit path and the receive path in the transceiver 302. A pair of RF switches SW3 and SW4 can be configured to select the calibration path 409. The switches SW3 and SW4 can be "1" pole "2" throw (1P2T) switches. The calibration path 409 can include any suitable transmission line, such as a microstrip line or a stripline. The switch SW3 is located between the first port TC1 of the antenna switch array 320 and the antenna tuner 306a, and the switch SW4 is located between the second port TC2 of the antenna switch array 320 and the antenna tuner 306b. Each of the switches SW3 and SW4 can be implemented using transistors (e.g., NFETs or PFETs) such as to form a transmission gate or other suitable specific implementations. In some implementations, switches SW3 and SW4 may be part of an RF test connector with built-in disconnect / make contacts. In a straight-through configuration of the antenna switch array 320, port TC1 is a transmit port and port TC2 is a receive port. In a crossover configuration, port TC1 is a receive port and port TC2 is a transmit port.

[0080] The calibration path-based characterization performed by the UE 400 includes a gain measurement mode and a reflection coefficient measurement mode. In both modes, the switch SW1 is closed and the switch SW2 is open. In the gain measurement mode, the controller 418, such as implemented by the data processor 410, performs a gain measurement 478 by the ratio of the received baseband digital signal to the transmitted baseband digital signal. The gain is measured twice: a first gain measurement using the calibration path 409 coupled to the ports TC1 and TC2 (the antennas 304a and 304b are therefore isolated) and a second gain measurement using the calibration path 409 isolated from the ports TC1 and TC2. This first gain is denoted herein as gain G v_CAL During the second gain measurement, antenna tuners 306a and 306b are tuned to achieve good power transfer (relatively low VSWR). The second gain is referred to herein as gain Gv_CANT In the second gain measurement, antenna switch array 320 may be in a straight-through configuration or a crossover configuration. The following discussion will assume that the straight-through configuration is used during the gain measurement without loss of generality. In the straight-through configuration during the second gain measurement, port TC1 is coupled to antenna 304a through switch SW3 and antenna tuner 306a, while port TC2 is coupled to antenna 304b through switch SW4 and antenna tuner 306b.

[0081] In the reflection coefficient mode measurement, the controller 418 controls the switches SW3 and SW4 to isolate the calibration path 409 from the ports TC1 and TC2. Then, the antennas 304a and 304b are coupled to the corresponding ports in the ports TC1 and TC2 through the corresponding switches SW3 and SW4. Then, similar to the discussion for the UE 300, the controller 418 measures the input reflection coefficient 376 sampled by the directional coupler 364, the switch 366 and the signal detector 374. The controller 418 controls the antenna switch array 320 so that the first reflection coefficient is measured when the antenna switch array 320 is in the through configuration, and so that the second reflection coefficient is measured when the antenna switch array 320 is in the cross configuration. In the cross configuration, the port TC1 is coupled to the antenna 304b through the antenna tuner 306b, and the port TC2 is coupled to the antenna 304a through the antenna tuner 306a.

[0082] By combining the gain measurement from the gain measurement mode with the reflection coefficient measurement from the reflection coefficient measurement mode, the controller 418 can calculate S describing the coupling between the antennas 304a and 304b. 21_CANT The scattering parameter is given by the following formula (6):

[0083]

[0084] Where S 21_CAL is a scattering parameter describing the coupling between the two input / output ports and the calibration path 409; represents the de-embedding of the antenna tuner 306a, where S 22_IT1 and S 21_IT1 is the scattering parameter of the antenna tuner 306a, such as obtained from an open-circuit-short load characterization, Γ IN_CANT_1 is obtained by measuring Γ using the antenna switch array 320 in a through configuration; represents the de-embedding of the antenna tuner 306b, where S 22_IT2 and S 21_IT2 is the scattering parameter of the antenna tuner 306b (eg, from an open-short-load characteristic), and S 22_CANT is obtained by measuring Γ using the antenna switch array 320 in a cross configuration.

[0085] It should be understood that the calibration path need not be coupled between ports TC1 and TC2, but may be coupled between the transmit and receive paths of transceiver 302 upstream of antenna switch array 320 (i.e., on the data processor 410 side of antenna switch array 320). Note, however, that increased accuracy may be obtained by placing calibration path 409 closer to antenna tuners 306a and 306b rather than further upstream in transceiver 302.

[0086] Now about Figure 4B 4 is a flowchart of an example of a calibration path-based characterization of scattering parameters performed by a UE 400. The method includes an act 430 of measuring a first gain between a transmit path and a receive path in a user equipment when the transmit path drives a first antenna of the user equipment with a first reference signal (e.g., SRS) and the receive path receives from a second antenna of the user equipment. The gain G v_CANT The determination of is an example of act 430. The method also includes act 435 of measuring a second gain between the transmit path and the receive path when the transmit path is coupled to the receive path through a transmit line and when the first antenna and the second antenna are isolated from the transmit path and the receive path. v_CAL The determination of is an example of act 435. In addition, the method includes an act 440 of measuring a reflection coefficient of the transmit path when the transmit path drives the first antenna with the second signal and the receive path receives from the second antenna. The determination of the input reflection coefficient of the antenna switch array 320 in a straight-through configuration or a crossover configuration is an example of act 440. Finally, the method includes an act 445 of calculating the coupling between the first antenna and the second antenna based on the first gain, the second gain, and the reflection coefficient. The controller 418 uses formula (6) to calculate S 21_CANT The calculation of is an example of action 445 .

[0087] Including the calibration path 409 is advantageous in increasing the fidelity of the antenna coupling characterization, but may add additional components (temporarily or permanently) to the UE architecture. A calibration path between the transmit and receive chains is not required in the calibration gain based in-device characterization. An example UE architecture for the calibration gain based technique will now be discussed.

[0088] Example UE architecture for calibrated gain-based in-device antenna coupling characterization

[0089] exist Figure 5A5 shows an example UE 500 with calibration gain based in-device characterization of antenna coupling. The transceiver 502 includes a transmitter 531 including a transmit chain including a DAC 334, one or more mixers 338, a local oscillator 340, and a power amplifier 328 arranged as discussed for the transmitter 330 of the UE 300. Similarly, the transceiver 502 includes a receiver 532 including a receive chain including an ADC 358, one or more mixers 354, a local oscillator 356, and an LNA 322 arranged as discussed for the receiver 332 of the UE 300. The UE 500 also includes a data processor 510 including a controller 518 for controlling the calibration gain based in-device characterization of antenna coupling.

[0090] The transmit chain extends through power amplifier 328 to antenna array switch 320 with the through configuration and cross configuration discussed with respect to UE 300 and 400. In the through configuration, the transmit chain is coupled from power amplifier 328 via antenna switch array 320 and via bandpass filter 519 to drive antenna tuner 306a and antenna 304a. In the through configuration, the receive chain is coupled from antenna 304b via antenna tuner 306b, bandpass filter 521, antenna switch array 320 to drive LNA 322. Bandpass filter 519 is coupled to antenna tuner 306a through test port 505. Similarly, bandpass filter 521 is coupled to antenna tuner 306b through test port 509.

[0091] In some implementations, test ports 505 and 509 are probe pads on a printed circuit board or antenna module including antenna tuners 306a and 306b. During the manufacture of UE 500, an external tester is coupled to test port 505 via a test probe. With antenna switch array 320 in a pass-through configuration, the external tester applies a matching load (e.g., 50Ω) at test port 505 and measures the transmit chain gain. For example, data processor 510 may be configured as a test mode in which the amplitude of the baseband TX signal is known. Alternatively, data processor 510 may report this signal amplitude to an external tester so that the external tester can determine the transmit chain gain. In some cases, port 505 is a probe pad at a PCB board. The external tester may be a power meter or a voltmeter. The external tester measures the difference between baseband Tx signal 536 and the signal detected by the external tester at test port 505, which is represented herein as G. TxCAL Calibrated send gain.

[0092] The external tester can also measure the G between the signal provided to the test port 509 and the baseband Rx signal 560, which is shown herein as RxCALThe data processor 510 may report the amplitude of the baseband Rx signal 560 to an external tester so that the external tester may determine the calibrated receive gain. These calibrated gain measurements may then be stored in the memory 580 of the data processor 510. During the calibrated gain measurements, the antennas 304a and 304b and the antenna tuners 306a and 306b are disconnected from the transmit and receive paths. Ports 505 and 509 may therefore be RF test connectors that have built-in disconnect / make contacts in some implementations.

[0093] During subsequent operation of the UE 500 after manufacture, the controller 518 may perform a ratio G of the baseband Rx signal 560 to the baseband Tx signal 536. v [dB] to estimate the antenna coupling between antennas 304a and 304b. Alternatively, gain measurement 578 may also be performed during the manufacture of UE 500. Controller 518 may then estimate antenna coupling, such as by the following formula (7):

[0094] C TxRx [dB] = G v [dB] - G TxCAL [dB] - G RxCAL [dB] Formula (7)

[0095] Among them G v [dB] is obtained during operation of the UE 500 and retrieved from the memory 580 of the processor 510. TxCAL and G RxCAL This calibration gain-based characterization provides an estimate of the magnitude of antenna coupling (without phase information). Note that this estimate varies as a function of the tuner state of antenna tuners 406a and 406b.

[0096] Now about Figure 5B 500. The method includes an act 515 of retrieving a calibrated transmit gain of a transmit chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated transmit gain is measured by an external tester. The gain G as measured at the test port 505 is retrieved from the memory 580. TxCAL is an example of action 515. The method further comprises an action 520 of retrieving a calibrated receive gain of a receive chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated receive gain is measured by an external tester. The gain G as measured at the test port 509 is retrieved in the memory 580. RxCALis an example of act 520. In addition, the method includes act 525 of measuring an operating gain between the transmit chain and the receive chain when the transmit path drives a first antenna of the user equipment (e.g., with a reference signal such as an SRS) and when the receive path receives through a second antenna of the user equipment. The gain G at the controller 518 v The measurement of is an example of action 525. Finally, the method includes an action 530 of estimating the coupling between the first antenna and the second antenna based on the operating gain, the transmit gain, and the receive gain. The controller 518 determines the coupling gain C using equation (7). TxRx is an example of action 530 .

[0097] It should be noted that when characterizing the working gain G v [dB] Use of the receive chain during this period may interfere with time-critical communications. To avoid such use of the receive chain, a feedback receive chain can be used. Fig. 6A 6 shows an example UE 600 with calibration gain based in-device characterization of antenna coupling including a feedback receive chain 605. The transceiver 602 includes a transmitter 531 with a transmit chain including a DAC 334, one or more mixers 338, a local oscillator 340, and a power amplifier 328 arranged as discussed for the UE 500. Similarly, the transceiver 602 includes a receiver 532 including a receive chain including an ADC 358, one or more mixers 354, a local oscillator 356, and an LNA 322 arranged as discussed for the UE 500. The UE 600 also includes a data processor 610 including a controller 618 for controlling the calibration gain based in-device characterization of antenna coupling.

[0098] The transmit chain extends through power amplifier 328 to antenna array switch 320 with the through configuration and cross configuration discussed for UE 500. In the through configuration, the transmit chain is coupled from power amplifier 328 via antenna switch array 320 and via bandpass filter 519 to drive antenna tuner 306a and antenna 304a. In the through configuration, the receive chain is coupled from antenna 304b via antenna tuner 306b, bandpass filter 521 and antenna switch array 320 to drive LNA 322. Bandpass filter 519 is coupled to antenna tuner 306a through test port 505. Similarly, bandpass filter 521 is coupled to antenna tuner 306b through test port 509.

[0099] The feedback receive path 605 can be used during normal operation of the UE 600 to measure the gain of the power amplifier 328 so that the transmitted signal can have a desired power level. The feedback receive path 605 includes the signal detector 374 discussed with respect to the UE 300. In some specific implementations, the signal detector 374 can be a square law detector. In other specific implementations, the signal detector 374 can include a down-conversion stage, such as a mixer also discussed with respect to the UE 300. The signal detector 374 is coupled to the directional coupler 364 via the switch SW and via the switch 366 so that the controller 618 can perform a gain measurement 678 of the power amplifier 328 during normal operation of the UE 600.

[0100] During a test calibration mode at the manufacturing of the UE 600, the switch SW is configured such that the receive feedback path 605 instead samples the receive signal from the receive path, such as by a sampling circuit (e.g., directional coupler 665). The antennas 304a and 304b are disconnected from the transmit path and the receive path during the test calibration phase. With respect to the test calibration mode, in some specific implementations of the UE 600, the test ports 505 and 509 are probe pads on a printed circuit board or antenna module including the antenna tuners 306a and 306b. The test calibration mode occurs during the manufacturing of the UE 600 and involves the use of an external tester coupled to the test port 505 or the test port 509. With the antenna switch array 320 in a through configuration, the external tester applies a matching load (e.g., 50Ω) at the test port 505 and measures the transmit chain gain. The external tester can be a power meter or a voltmeter. The external tester measures the gain, denoted herein as G TxCAL The calibrated transmit gain G defines the gain between the baseband Tx signal 565 and the signal detected by the external tester at the test port 505. TxCAL It can then be stored in the memory 580. To measure the RxCAL The external tester is coupled to the test port 509, and the switch SW couples the feedback receive chain 605 to the directional coupler 665. In this way, the external tester can measure the calibrated receive gain G RxCAL , which is defined as the gain between the test signal applied to the test port 509 and the detected baseband signal from the feedback receive path 605. The calibrated receive gain G RxCAL Stored in memory 580.

[0101] To measure antenna coupling during normal operation of the UE 600, the controller 618 may measure the operating gain G between the baseband Tx signal 536 and the detected baseband signal from the feedback receive path 605. v[dB], where the switch SW is configured to couple the directional coupler 665 to the feedback receive path 605. v [dB], G TxCAL and G RxCAL Knowing this, the controller 618 may then proceed to determine the antenna coupling C as discussed with respect to equation (7) TxRx [dB]. In contrast to UE 500, UE 600 can continue to receive on its receive path in normal operation because the sensing circuitry, such as directional coupler 665, senses only a portion of the receive signal. The remaining portion of the receive signal can be amplified by LNA 322, down-converted in mixer 354, and digitized in ADC 358 to form baseband Rx signal 560. Therefore, when controller 618 measures gain G v [dB], the baseband Rx signal 560 can be received simultaneously in the UE 600.

[0102] Now about Figure 6B The flowchart of UE 600 describes an example of a calibration gain based characterization method using a feedback receive path. The method includes an act 615 of retrieving a calibrated transmit gain of a transmit chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated transmit gain is measured by an external tester. The gain calibration transmit gain G measured at the test port 505 in the UE 600 is retrieved in the memory 580. TxCAL is an example of action 615. The method further comprises an action 620 of retrieving a calibrated receive gain of a feedback receive chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated receive gain is measured by an external tester. The calibrated receive gain G as measured at the test port 509 in the UE 600 is retrieved in the memory 580. RxCAL is an example of act 620. In addition, the method includes act 625 of measuring an operating gain between the transmit chain and the feedback receive chain when the transmit path drives (e.g., using a reference signal, such as an SRS) a first antenna of the user equipment and the feedback receive path samples a receive signal from the user equipment, wherein the receive path receives the receive signal through a second antenna of the user equipment. The gain G at the controller 618 is v The measurement of is an example of action 625. Finally, the method includes an action 630 of estimating the coupling between the first antenna and the second antenna based on the operating gain, the transmit gain, and the receive gain. The controller 618 determines the coupling gain C using equation (7). TxRx is an example of action 630.

[0103] The present disclosure will now be summarized in the following example clauses.

[0104] Clause 1. An apparatus for wireless communication, the apparatus comprising:

[0105] a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna;

[0106] a first antenna tuner coupled to the first antenna;

[0107] a second antenna tuner coupled to the second antenna;

[0108] Transmitter;

[0109] Receiver;

[0110] an antenna switch array having a first configuration in which the transmitter is coupled through the antenna switch array to drive the first antenna through the first antenna tuner, and in which the second antenna tuner is coupled to a receiver node;

[0111] a first switch coupled between the receiver node and a receive path in the receiver; and

[0112] A second switch is coupled between the receiver node and a matched load.

[0113] Clause 2. The apparatus of clause 1, further comprising:

[0114] a controller configured to adjust the second antenna tuner with a plurality of load values ​​to determine a first coupling factor between the first antenna and the second antenna when the antenna switch array is in the first configuration, the first switch is open, and the second switch is closed; and

[0115] A directional coupler is coupled to a transmit path of the transmitter and is configured to sample a forward signal directed toward the antenna switch array through the transmit path and further configured to detect a reverse signal directed from the antenna switch array through the transmit path.

[0116] Clause 3. An apparatus according to clause 2, wherein the controller is further configured to determine the first coupling factor in response to a ratio of the reverse signal to the forward signal at a first load value among the plurality of load values ​​when the antenna switch array is in the first configuration.

[0117] Clause 4. The apparatus of clause 3, wherein the plurality of load values ​​comprises three load values.

[0118] Clause 5. The apparatus of any of Clauses 2 to 4, wherein the controller is further configured to adjust the first antenna tuner to a load value that matches an impedance of the first antenna tuner to an impedance of the transmitter.

[0119] Clause 6. The apparatus of clause 1, wherein the apparatus comprises user equipment.

[0120] Clause 7. An apparatus according to Clause 3, wherein the antenna switch array is capable of being configured to enter a second configuration in which the transmitter is coupled through the antenna switch array to drive the second antenna through the second antenna tuner, and in the second configuration, the receiver is coupled through the antenna switch array to receive from the first antenna through the first antenna tuner.

[0121] Clause 8. The apparatus of clause 7, wherein the controller is further configured to adjust the first antenna tuner by a plurality of load values ​​to determine a second coupling factor between the first antenna and the second antenna when the antenna switch array is in the second configuration.

[0122] Clause 9. The apparatus of clause 8, wherein the controller is configured to average the first coupling factor and the second coupling factor.

[0123] Clause 10. An apparatus for wireless communication, the apparatus comprising:

[0124] a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna;

[0125] a transmitter, the transmitter comprising a transmission path;

[0126] a receiver, the receiver comprising a receive path;

[0127] send line; and

[0128] A plurality of switches, the plurality of switches being configurable to enter a first configuration in which the transmit path is coupled to the receive path through the transmit line and in which the first antenna and the second antenna are isolated from the transmit path and the receive path, and the plurality of switches being configurable to enter a second configuration in which the transmit path and the receive path are coupled to respective ones of the first antenna and the second antenna and in which the transmit line is isolated from the transmit path and the receive path.

[0129] Clause 11. The apparatus of clause 10, further comprising:

[0130] A controller is configured to measure a calibration gain between the transmit path and the receive path when the plurality of switches are in the first configuration and to measure an operating gain between the transmit path and the receive path when the plurality of switches are in the second configuration.

[0131] Clause 12. The apparatus of clause 11, further comprising:

[0132] A directional coupler is coupled to the transmission path and is configured to sample a forward signal directed through the transmission path toward the plurality of switches and further configured to detect a reverse signal directed from the plurality of switches through the transmission path.

[0133] Clause 13. The apparatus of clause 12, wherein the controller is further configured to calculate a coupling factor between the first antenna and the second antenna based on a ratio of the reverse signal to the forward signal, the calibration gain, and the operating gain.

[0134] Clause 14. The apparatus of clause 12, further comprising:

[0135] An antenna switch array having a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receive path is coupled through the antenna switch array to receive from the second antenna, and having a second configuration in which the transmit path is coupled through the antenna switch array to drive the second antenna and in which the receive path is coupled through the antenna switch array to receive from the first antenna.

[0136] Clause 15. The apparatus of clause 10, further comprising:

[0137] a first antenna tuner coupled to the first antenna; and

[0138] A second antenna tuner is coupled to the second antenna.

[0139] Clause 16. An apparatus for wireless communication, the apparatus comprising:

[0140] a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna;

[0141] a transmitter, the transmitter comprising a transmission path;

[0142] a receiver, the receiver comprising a receive path;

[0143] an antenna switch array configurable into a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receiver is coupled through the antenna switch array to receive from the second antenna; and

[0144] A controller is configured to measure an operating gain between the transmit path and the receive path when the antenna switch array is in the first configuration, and the controller is further configured to estimate a coupling gain between the first antenna and the second antenna based on the operating gain, a calibrated transmit gain of the transmit path, and a calibrated receive gain of the receive path.

[0145] Clause 17. The apparatus of clause 16, further comprising:

[0146] a first test port coupled between the transmit path and the first antenna for measuring the calibrated transmit gain; and

[0147] A second test port is coupled between the receiving path and the second antenna for measuring the calibrated receiving gain.

[0148] Clause 18. An apparatus according to clause 16, wherein the antenna switch array is further configurable to enter a second configuration in which the transmit path is coupled through the antenna switch array to drive the second antenna, and in the second configuration, the receiver is coupled through the antenna switch array to receive from the first antenna.

[0149] Clause 19. A method comprising:

[0150] transmitting, via the transmitter chain, a first signal to a first antenna of the user equipment;

[0151] varying a load of a second antenna of the user equipment by each of a first plurality of load values ​​during the transmission of the first signal;

[0152] measuring a reflection coefficient of the transmitter chain for each of the first plurality of load values ​​to provide a first plurality of measured reflection coefficients during the transmission of the first signal; and

[0153] A first coupling factor between the first antenna and the second antenna is calculated based on the first plurality of measured reflection coefficients and the first plurality of loading values.

[0154] Clause 20. The method according to clause 19, further comprising:

[0155] transmitting a second signal to the second antenna via the transmitter chain;

[0156] varying a load of the first antenna by each of a second plurality of load values ​​during the transmission of the second signal;

[0157] measuring a reflection coefficient of the transmitter chain for each of the second plurality of load values ​​to provide a second plurality of measured reflection coefficients during the transmission of the second signal; and

[0158] A second coupling factor between the first antenna and the second antenna is calculated based on the second plurality of measured reflection coefficients and the second plurality of loading values.

[0159] Clause 21. The method of clause 20, further comprising: averaging the first coupling factor and the second coupling factor.

[0160] In some cases, in order to avoid blurring the concepts of the described examples, well-known structures and devices are shown in block diagram form. The description herein is provided to enable those skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for wireless communication, the device comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; a first antenna tuner coupled to the first antenna; a second antenna tuner coupled to the second antenna; Transmitter; Receiver; an antenna switch array having a first configuration in which the transmitter is coupled through the antenna switch array to drive the first antenna through the first antenna tuner, and in which the second antenna tuner is coupled to a receiver node; a first switch coupled between the receiver node and a receive path in the receiver; and A second switch is coupled between the receiver node and a matched load.

2. The device according to claim 1, further comprising: a controller configured to adjust the second antenna tuner with a plurality of load values ​​to determine a first coupling factor between the first antenna and the second antenna when the antenna switch array is in the first configuration, the first switch is open, and the second switch is closed; and A directional coupler is coupled to a transmit path of the transmitter and is configured to sample a forward signal directed toward the antenna switch array through the transmit path and further configured to detect a reverse signal directed from the antenna switch array through the transmit path.

3. The apparatus of claim 2, wherein the controller is further configured to determine the first coupling factor in response to a ratio of the reverse signal to the forward signal at a first load value among the plurality of load values ​​when the antenna switch array is in the first configuration. The apparatus of claim 3 , wherein the plurality of load values ​​comprises three load values. 5 . The apparatus of claim 2 , wherein the controller is further configured to adjust the first antenna tuner to a load value that matches an impedance of the first antenna tuner to an impedance of the transmitter. The apparatus of claim 1 , wherein the apparatus comprises user equipment.

7. The apparatus of claim 3, wherein the antenna switch array is configurable to enter a second configuration in which the transmitter is coupled through the antenna switch array to drive the second antenna through the second antenna tuner, and in the second configuration, the receiver is coupled through the antenna switch array to receive from the first antenna through the first antenna tuner.

8. The apparatus of claim 7, wherein the controller is further configured to adjust the first antenna tuner by a plurality of load values ​​to determine a second coupling factor between the first antenna and the second antenna when the antenna switch array is in the second configuration. 9 . The apparatus of claim 8 , wherein the controller is configured to average the first coupling factor and the second coupling factor.

10. An apparatus for wireless communication, the apparatus comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; A transmitter, the transmitter comprising a transmission path; a receiver, the receiver comprising a receive path; Send line; and A plurality of switches, the plurality of switches being configurable to enter a first configuration in which the transmit path is coupled to the receive path through the transmit line and in which the first antenna and the second antenna are isolated from the transmit path and the receive path, and the plurality of switches being configurable to enter a second configuration in which the transmit path and the receive path are coupled to respective ones of the first antenna and the second antenna and in which the transmit line is isolated from the transmit path and the receive path.

11. The device according to claim 10, further comprising: A controller is configured to measure a calibration gain between the transmit path and the receive path when the plurality of switches are in the first configuration and to measure an operating gain between the transmit path and the receive path when the plurality of switches are in the second configuration.

12. The device according to claim 11, further comprising: A directional coupler is coupled to the transmission path and is configured to sample a forward signal directed through the transmission path toward the plurality of switches and further configured to detect a reverse signal directed from the plurality of switches through the transmission path. 13 . The apparatus of claim 12 , wherein the controller is further configured to calculate a coupling factor between the first antenna and the second antenna based on a ratio of the reverse signal to the forward signal, the calibration gain, and the operating gain.

14. The apparatus according to claim 12, further comprising: An antenna switch array having a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receive path is coupled through the antenna switch array to receive from the second antenna, and having a second configuration in which the transmit path is coupled through the antenna switch array to drive the second antenna and in which the receive path is coupled through the antenna switch array to receive from the first antenna.

15. The apparatus according to claim 10, further comprising: a first antenna tuner coupled to the first antenna; and A second antenna tuner is coupled to the second antenna.

16. An apparatus for wireless communication, the apparatus comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; A transmitter, the transmitter comprising a transmission path; a receiver, the receiver comprising a receive path; an antenna switch array configurable into a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receiver is coupled through the antenna switch array to receive from the second antenna; and A controller is configured to measure an operating gain between the transmit path and the receive path when the antenna switch array is in the first configuration, and the controller is further configured to estimate a coupling gain between the first antenna and the second antenna based on the operating gain, a calibrated transmit gain of the transmit path, and a calibrated receive gain of the receive path.

17. The apparatus according to claim 16, further comprising: a first test port coupled between the transmit path and the first antenna for measuring the calibrated transmit gain; and A second test port is coupled between the receiving path and the second antenna for measuring the calibrated receiving gain.

18. The apparatus of claim 16, wherein the antenna switch array is further configurable to enter a second configuration in which the transmit path is coupled through the antenna switch array to drive the second antenna, and in which the receiver is coupled through the antenna switch array to receive from the first antenna.

19. A method comprising: transmitting, via the transmitter chain, a first signal to a first antenna of the user equipment; varying a load of a second antenna of the user equipment by each of a first plurality of load values ​​during the transmission of the first signal; measuring a reflection coefficient of the transmitter chain for each of the first plurality of load values ​​to provide a first plurality of measured reflection coefficients during the transmission of the first signal; as well as A first coupling factor between the first antenna and the second antenna is calculated based on the first plurality of measured reflection coefficients and the first plurality of loading values.

20. The method according to claim 19, further comprising: transmitting a second signal to the second antenna via the transmitter chain; varying a load of the first antenna by each of a second plurality of load values ​​during the transmission of the second signal; measuring a reflection coefficient of the transmitter chain for each of the second plurality of load values ​​to provide a second plurality of measured reflection coefficients during the transmission of the second signal; as well as A second coupling factor between the first antenna and the second antenna is calculated based on the second plurality of measured reflection coefficients and the second plurality of loading values.

21. The method according to claim 20, further comprising: The first coupling factor and the second coupling factor are averaged.

22. A wireless communication device, comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; A transmitter, the transmitter comprising a transmission path; a receiver, the receiver comprising a receive path; an antenna switch array configurable into a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receive path is coupled through the antenna switch array to receive from the second antenna; and A controller is configured to measure an operating gain between the transmit path and the receive path when the antenna switch array is in the first configuration, and the controller is further configured to estimate a coupling gain between the first antenna and the second antenna based on the operating gain, a calibrated transmit gain of the transmit path, and a calibrated receive gain of the receive path.

23. The wireless communication device of claim 22, further comprising: a first test port coupled between the transmit path and the first antenna for measuring the calibrated transmit gain; and A second test port is coupled between the receiving path and the second antenna for measuring the calibrated receiving gain.

24. A wireless communication device according to claim 22, wherein the antenna switch array is also capable of being configured to enter a second configuration, in which the transmit path is coupled through the antenna switch array to drive the second antenna, and in the second configuration, the receive path is coupled through the antenna switch array to receive from the first antenna.

25. The wireless communication device of claim 23, wherein the transmit path comprises: 3 a digital-to-analog converter configured to convert a digital transmit baseband signal into an analog transmit baseband signal; a first mixer, the first mixer being configured to up-convert the transmit baseband signal into a radio frequency transmit signal; and A power amplifier is configured to amplify the radio frequency transmission signal.

26. The wireless communication device of claim 25, wherein an output terminal of the power amplifier is coupled to the antenna switch array.

27. The wireless communication device of claim 25, further comprising: A first antenna tuner is coupled to the first antenna, wherein the first test port is coupled between the antenna switch array and the first antenna tuner.

28. The wireless communication device of claim 27, wherein the receiving path 27 comprises: a low noise amplifier coupled to the antenna switch array; a second mixer configured to down-convert an output signal from the low noise amplifier into an analog receive signal; and An analog-to-digital converter is configured to digitize the analog received signal into a digital received baseband signal.

29. The wireless communication device of claim 28, further comprising: A second antenna tuner is coupled to the second antenna, wherein the second test port is coupled between the antenna switch array and the second antenna tuner.

30. The wireless communication device of claim 22, wherein the controller is further configured to estimate the coupling gain between the first antenna and the second antenna based on a difference between the operating gain and a sum of the calibrated transmit gain and the calibrated receive gain.

31. A method of determining coupling between a first antenna and a second antenna of a wireless communication device, the method comprising: retrieving a calibrated transmit gain for a transmit chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated transmit gain is measured by an external tester; retrieving a calibrated receive gain for a receive chain of the wireless communication device from the memory of the wireless communication device, wherein the calibrated receive gain is measured by the external tester; measuring an operating gain between the transmit chain and the receive chain when the transmit path drives the first antenna and the receive path receives through the second antenna; as well as Coupling between the first antenna and the second antenna is estimated based on the operating gain, the calibrated transmit gain, and the calibrated receive gain.

32. The method of claim 31 , wherein estimating the coupling comprises forming a difference between the operating gain and a sum of the calibrated transmit gain and the calibrated receive gain.

33. The method according to claim 31, further comprising: An impedance of at least one of the first antenna and the second antenna is tuned in response to the estimate of the coupling between the first antenna and the second antenna.

34. The method of claim 31, wherein the calibrated transmit gain is measured by the external tester via a first test port coupled to the transmit chain.

35. The method of claim 34, wherein the calibrated receive gain is measured by the external tester via a second test port coupled to the receive chain.

36. A wireless communication device, the wireless communication device comprising: a plurality of antennas, the plurality of antennas comprising a first antenna and a second antenna; A transceiver, the transceiver comprising a transmit path, a receive path, and a feedback receive path; an antenna switch array configurable into a first configuration in which the transmit path is coupled through the antenna switch array to drive the first antenna and in which the receive path is coupled through the antenna switch array to receive from the second antenna; and a controller configured to measure an operating gain between the transmit path and the feedback receive path when the antenna switch array is in the first configuration, the controller further configured to estimate a coupling gain between the first antenna and the second antenna based on the operating gain, a calibrated transmit gain of the transmit path, and a calibrated receive gain of the feedback receive path.

37. The wireless communication device of claim 36, further comprising: a first test port coupled between the transmit path and the first antenna for measuring the calibrated transmit gain; and A second test port is coupled between the feedback receiving path and the second antenna for measuring the calibration receiving gain.

38. A wireless communication device according to claim 36, wherein the antenna switch array is also capable of being configured to enter a second configuration, in which the transmit path is coupled through the antenna switch array to drive the second antenna, and in the second configuration, the receive path is coupled through the antenna switch array to receive from the first antenna.

39. The wireless communication device of claim 37, wherein the transmit path comprises: a digital-to-analog converter configured to convert a digital transmit baseband signal into an analog transmit baseband signal; a first mixer, the first mixer being configured to up-convert the transmit baseband signal into a radio frequency transmit signal; a power amplifier, the power amplifier being configured to amplify the radio frequency transmit signal; and A first directional coupler is configured to sample an output signal of the power amplifier.

40. The wireless communication device of claim 39, further comprising: a second directional coupler configured to sample a received signal from the receive path; and A feedback receive switch has a first configuration in which the feedback receive path is coupled to the first directional coupler and has a second configuration in which the feedback receive path is coupled to the second directional coupler.

41. The wireless communication device of claim 40, wherein the feedback receive path is configured to down-convert the signal from the feedback receive switch to an analog signal and digitize the analog signal to form a digital baseband signal.

42. The wireless communication device of claim 39, further comprising: A first antenna tuner is coupled to the first antenna, wherein the first test port is coupled between the antenna switch array and the first antenna tuner.

43. The wireless communication device of claim 42, wherein the receive path comprises: a low noise amplifier coupled to the antenna switch array; a second mixer configured to down-convert an output signal from the low noise amplifier into an analog receive signal; and An analog-to-digital converter is configured to digitize the analog received signal into a digital received baseband signal.

44. The wireless communication device of claim 43, further comprising: A second antenna tuner is coupled to the second antenna, wherein the second test port is coupled between the antenna switch array and the second antenna tuner.

45. The wireless communication device of claim 36, wherein the controller is further configured to estimate the coupling gain between the first antenna and the second antenna based on a difference between the operating gain and a sum of the calibrated transmit gain and the calibrated receive gain.

46. ​​A method of determining coupling between a first antenna and a second antenna of a wireless communication device, the method comprising: retrieving a calibrated transmit gain for a transmit chain of the wireless communication device from a memory of the wireless communication device, wherein the calibrated transmit gain is measured by an external tester; retrieving a calibrated receive gain of a feedback receive chain of the wireless communication device from the memory of the wireless communication device, wherein the calibrated receive gain is measured by the external tester; measuring an operating gain between the transmit chain and the feedback receive chain when the transmit path drives the first antenna and when the receive path of the wireless communication device receives through the second antenna; as well as Coupling between the first antenna and the second antenna is estimated based on the operating gain, the calibrated transmit gain, and the calibrated receive gain.

47. The method of claim 46, wherein estimating the coupling comprises forming a difference between the operating gain and a sum of the calibrated transmit gain and the calibrated receive gain.

48. The method of claim 46, further comprising: sampling a received signal from the receiving path to provide a sampled signal; as well as The sampled signal is coupled to the feedback receive path while measuring the operating gain.

49. The method of claim 48, wherein coupling the sampled signal to the feedback receive signal comprises coupling the receive path to the feedback receive path via a directional coupler.

50. The method of claim 46, further comprising: An impedance of at least one of the first antenna and the second antenna is tuned in response to the estimate of the coupling between the first antenna and the second antenna.

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