Multiple-input multiple-output (MIMO) transceiver and operation method thereof

Abstract

The invention discloses a multiple-input multiple-output (MIMO) transceiver and a method of operation thereof. The MIMO transceiver may include a first communication chain configured to wirelessly transmit a signal at a first frequency. The first communication chain may include a predistorter circuit configured to accept parameters to predistort the signal prior to transmission. The first communication chain may include a PA configured to amplify the signal of the first communication chain prior to transmission. The MIMO transceiver may include a second communication chain, which may be configured to wirelessly receive the signal at the first frequency. The second communication chain may include a converter circuit configured to convert the signal to a baseband frequency. The second communication chain may include a buffer configured to buffer the signal at the baseband frequency. The MIMO transceiver may include a DPD circuit configured to calibrate the parameter based on the buffered signal to compensate for nonlinearity of amplification of the PA.

Description

[0001] This application is a divisional application of the invention patent application with application date of December 4, 2020, application number 202011408919.6, and invention name “Multiple-input multiple-output MIMO transceiver and its operation method”. Technical Field

[0002] Specific implementations discussed in this disclosure relate to multiple-input multiple-output (MIMO) transceivers and methods of operating the same, and more particularly to wireless coupling for digital predistortion calibration. Background Art

[0003] Unless otherwise indicated in this disclosure, materials described in this disclosure are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

[0004] A wireless network (e.g., a wireless local area network (WLAN)) may include a multiple-input multiple-output (MIMO) transceiver for communicatively coupling computing devices connected to the wireless network to each other and / or providing access to the Internet. The MIMO transceiver may include multiple communication chains for wirelessly receiving signals from a computing device and wirelessly transmitting signals to a computing device. The communication chain may include a power amplifier (PA) that amplifies the corresponding signal before transmission. The PA may provide non-linear amplification of the signal, which may cause signal distortion and errors when the signal is received by the computing device. The non-linearity of the amplification provided by the PA may be compensated by pre-distorting the signal before the PA performs amplification.

[0005] The subject matter claimed in this disclosure is not limited to implementations that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is merely provided to illustrate one example technology area in which some implementations described in this disclosure may be practiced. Summary of the invention

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0007] One or more specific implementations of the present disclosure may include a MIMO transceiver. The MIMO transceiver may be configured for digital predistortion (DPD) calibration. The MIMO transceiver may include a first communication chain. The first communication chain may be configured to wirelessly transmit a signal at a first frequency. The first communication chain may include a predistorter circuit. The predistorter circuit may be configured to receive predistortion parameters to predistort the signal before transmission. The first communication chain may also include a PA. The PA may be configured to amplify the signal of the first communication chain before transmission. The MIMO transceiver may also include a second communication chain. The second communication may be configured to wirelessly receive a signal at a first frequency. The second communication chain may also include a converter circuit. The converter circuit may be configured to convert the signal to a baseband frequency. In addition, the second communication chain may include a buffer. The buffer may be configured to buffer the signal at the baseband frequency. In addition, the MIMO transceiver may include a DPD circuit. The DPD circuit may be configured to calibrate the predistortion parameters. The predistortion parameters may be calibrated based on the buffered signal to compensate for the nonlinearity of the amplification provided by the PA of the first communication chain.

[0008] One or more specific implementations of the present disclosure may include a method of operating a MIMO transceiver. The MIMO transceiver may be configured for DPD calibration. The method may include wirelessly transmitting a signal at a first frequency. The signal may be wirelessly transmitted from a first communication chain of the MIMO transceiver. The first communication chain may include a predistorter circuit configured to receive predistortion parameters to predistort the signal before transmission. The first communication chain may also include a PA configured to amplify the signal of the first communication chain before transmission. The method may also include wirelessly receiving a signal at a first frequency. The signal may be received at a second communication chain of the MIMO transceiver. In addition, the method may include converting the signal to a baseband frequency by the second communication chain. In addition, the method may include buffering the signal at the baseband frequency by the second communication chain. The method may include calibrating the predistortion parameters. The predistortion parameters may be calibrated based on the buffered signal to compensate for the nonlinearity of the amplification provided by the PA of the first communication chain.

[0009] Additional features and advantages of the present invention will be set forth in the following description and will be partially apparent from the description or may be learned through practice of the present invention. The features and advantages of the present invention may be realized and obtained using the instruments and combinations specifically pointed out in the appended claims. These and other features of the present invention will become more apparent from the following description and the appended claims or may be learned through practice of the present invention as described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to further illustrate the above and other advantages and features of the present invention, a more specific description of the present invention will be presented by reference to the specific implementations of the present invention shown in the accompanying drawings. It should be understood that these drawings only depict exemplary implementations of the present invention and therefore should not be considered as limiting the scope of the present invention. The present invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0011] Figure 1 An exemplary environment in which a wireless access point (WAP) having a MIMO transceiver may be implemented is shown;

[0012] Figure 2 It shows that it can be Figure 1 An exemplary MIMO transceiver implemented in an environment of;

[0013] Figure 3 It shows that it can be Figure 2 DPD circuits and exemplary communication chains implemented in MIMO transceivers;

[0014] Figure 4 An exemplary environment including a WAP and a wireless station (STA) is shown; and

[0015] Figure 5 A flow chart illustrating an exemplary method of operating a MIMO transceiver;

[0016] All of this is in accordance with at least one specific implementation described in this disclosure. DETAILED DESCRIPTION

[0017] A wireless network (e.g., a wireless local area network (WLAN)) may include multiple wireless nodes or devices that wirelessly communicate with each other. In an exemplary implementation, a node may include a WAP, a repeater, one or more STAs, and / or other wireless nodes. Each WAP, STA, and / or other wireless node may include a MIMO transceiver to send and / or receive wireless communications. Each MIMO transceiver may include multiple communication chains to allow simultaneous wireless communications between the MIMO transceiver and other wireless devices.

[0018] Each communication chain may include a receiving portion configured to wirelessly receive and process signals from other wireless devices. In addition, each communication chain may include a transmitting portion configured to process and amplify signals before transmission. In addition, the transmitting portion may include non-ideal components that cause distortion of the signal transmitted by the corresponding communication chain. For example, the transmitting portion may include a PA that provides a non-linear amplification of the power level of the signal before transmission. The non-linearity of the amplification provided by the PA may cause signal distortion. The distortion may reduce the signal quality and reduce the data rate of the corresponding signal.

[0019] The nonlinearity of the amplification provided by the PA can be compensated by performing DPD calibration and DPD application on one or more of the communication chains. The DPD calibration can include calibrating predistortion parameters based on the nonlinearity of the amplification provided by the PA. In addition, the DPD application can include predistorting the signal based on the predistortion parameters (e.g., the signal can be predistorted before being amplified by the PA). In some implementations, the signal can be predistorted in the opposite direction of the nonlinear amplification provided by the PA to bring the power level of the signal closer to the expected power level after amplification.

[0020] In some implementations, a MIMO transceiver may include a DPD circuit configured to observe the amplification of the PA. In these implementations, the DPD circuit may calibrate the predistortion parameters based on the observed amplification of the PA. Some DPD techniques may include one or more dedicated DPD calibration chains for observing the amplification of the PA. For example, some DPD techniques may include a dedicated DPD calibration chain for each communication chain in the MIMO transceiver. In these DPD techniques, for example, a MIMO transceiver including eight communication chains may also include eight dedicated DPD calibration chains. Some DPD techniques include a DPD calibration chain that shares part of a receive chain and requires additional circuitry.

[0021] In some DPD techniques, the DPD calibration chain may include a coupler (e.g., a radio frequency (RF) coupler) coupled to the output of the corresponding PA and / or a variable attenuator coupled to the output of the corresponding coupler. In addition, some dedicated DPD calibration chains may include a downconverter, a variable gain circuit, a filter, and / or an observation receiver circuit configured to receive the output of the corresponding PA and measure the corresponding amplification. Some shared DPD calibration chains may include a multiplexer (MUX), for example, to selectively couple to the output of the coupler instead of the output of the antenna in the corresponding receiving chain. In addition, in some DPD techniques, all communication chains of a MIMO transceiver may be in a transmission mode or a reception mode at the same time. These DPD techniques may not allow a portion of the communication chain to be in a transmission mode while allowing another portion of the communication chain to be in a reception mode.

[0022] Due to the inclusion of a DPD calibration chain, these DPD techniques may result in a larger circuit footprint for the MIMO transceiver. For example, each of the coupler, variable attenuator, downconverter, variable gain circuit, filter, observation receiver in a dedicated DPD chain and / or each of the coupler, variable attenuator, and MUX in a shared DPD chain may increase the circuit footprint of the communication chain. In addition, due to the cost of the components in the DPD calibration chain, these DPD techniques may increase the cost of producing the MIMO transceiver. For example, each of the coupler, variable attenuator, downconverter, variable gain circuit, filter, observation receiver, and / or MUX increases the cost of producing the MIMO transceiver.

[0023] Some implementations described in the present disclosure may allow DPD calibration and / or DPD application to be performed for a communication chain of a MIMO transceiver without requiring a dedicated DPD calibration chain. In addition, implementations described in the present disclosure may allow communication chains to be coupled to each other using wireless (OTA) coupling. For example, implementations described in the present disclosure may allow a first communication chain to be in a transmit mode while allowing a second communication chain to be in a receive mode. The first communication chain and the second communication chain may be wirelessly coupled to each other, for example, via antennas in the first communication chain and the second communication chain.

[0024] In some implementations, the first communication chain may wirelessly transmit a signal at a first frequency after being amplified by a corresponding PA. In addition, the second communication chain may wirelessly receive a signal at the first frequency. The second communication chain may convert the signal from the first frequency to a baseband frequency. In addition, the second communication chain may buffer the signal at the baseband frequency. The DPD circuit may calibrate a pre-distortion parameter based on the signal buffered by the second communication chain. The pre-distortion parameter may be calibrated based on the nonlinearity of the amplification provided by the PA.

[0025] Some implementations described in the present disclosure may reduce the circuit footprint of a MIMO transceiver because the communication chain itself may be used to observe the amplification of the PA without, for example, the couplers, variable attenuators, downconverters, variable gain circuits, filters, observation receivers, and / or MUXs used in each of the dedicated or shared DPD circuits as described above. In addition, some implementations described in the present disclosure may reduce the cost of producing a MIMO transceiver because the couplers, variable attenuators, downconverters, variable gain circuits, filters, observation receivers, and / or MUXs in the DPD calibration chain may not be included in the MIMO transceiver. In addition, some implementations described in the present disclosure may improve the calibration of predistortion parameters and the performance of the receive chain in a conventional receive mode by eliminating the insertion loss of the MUX and / or other components in the DPD calibration chain.

[0026] These and other specific implementations of the present disclosure will be explained with reference to the accompanying drawings. It will be understood that the accompanying drawings are diagrammatic and schematic representations of these exemplary specific implementations and are not limiting, nor are they necessarily drawn to scale. In the drawings, features with the same number indicate the same structure and function, unless otherwise described.

[0027] Figure 1 An exemplary environment 100 is shown in accordance with at least one implementation disclosed in the present disclosure, in which a WAP 101 having a MIMO transceiver 102 may be implemented. The environment 100 (e.g., an operating environment) may also include a first computing device 105a and a second computing device 105b (collectively referred to as "computing devices 105" in the present disclosure), each of which may include a STA or be implemented as a STA.

[0028] WAP 101 and computing device 105 can create a wireless network. In some implementations, WAP 101 can provide computing device 105 with access to the Internet. Exemplary computing devices 105 can include personal computers, printers, televisions, digital video disc (DVD) players, security cameras, smart phones, tablet computers, smart devices, or any other suitable computing devices configured for wireless communication. Thus, each of computing devices 105 can include a MIMO transceiver similar to MIMO transceiver 102. In some implementations, the MIMO transceiver of computing device 105 can implement DPD calibration and DPD applications as described herein.

[0029] The MIMO transceiver 102 of the WAP 101 may include multiple communication chains ( Figure 1 102) to allow simultaneous communication between the MIMO transceiver 102 and two computing devices 105. For example, the first computing device 105a can transmit signals to the first communication link of the MIMO transceiver 102 and receive signals from the first communication link of the MIMO transceiver 102. For another example, the second computing device 105b can transmit signals to the second communication link of the MIMO transceiver 102 and receive signals from the second communication link of the MIMO transceiver 102. The MIMO transceiver 102 may include four, eight, twelve, or any other suitable number of communication links. The communication links of the MIMO transceiver 102 are referred to below with respect to Figure 2 and Figure 3 Discuss in more detail.

[0030] Each communication link may include a transmission portion. The transmission portion may perform functions associated with transmitting a signal to the computing device 105. The transmission portion may include non-ideal components that cause signal distortion. For example, each of the transmission portions may include a PA that provides non-linear amplification of the power level of the corresponding signal. The non-linearity of the amplification provided by the PA may cause signal distortion. The distortion of the signal may reduce the signal quality and reduce the data rate of the corresponding signal.

[0031] The MIMO transceiver 102 may be configured to perform DPD calibration using OTA coupling of the communication link. The MIMO transceiver 102 may perform DPD calibration and DPD application to compensate for nonlinearity of amplification provided by the PA. The DPD calibration may include calibrating predistortion parameters based on the nonlinearity of amplification provided by the PA. In addition, the DPD application may include predistorting the signal based on the predistortion parameters (e.g., the signal may be distorted before being amplified by the PA).

[0032] Figure 2 It shows that at least one specific implementation disclosed in the present disclosure can be Figure 1 An example MIMO transceiver 217 implemented in the environment 100 of FIG. The wireless transceiver 217 may correspond to Figure 1 For example, the MIMO transceiver 217 can be configured to perform DPD calibration using OTA coupling of the communication link 210. In addition, the MIMO transceiver 217 can be configured to perform a DPD application for the communication link 210.

[0033] The MIMO transceiver 217 may include a DPD circuit 220 and two or more communication chains 210. In the illustrated implementation, the MIMO transceiver 217 includes a first communication chain 210a, a second communication chain 210b, a third communication chain 210c, and an Nth communication chain 210n (collectively referred to as "communication chains 210" in this disclosure). Figure 2 As indicated by the ellipsis in and the Nth communication chain 210n, the MIMO transceiver 217 may include any appropriate number of communication chains 210. The communication chains 210 may be individually configured to be in a transmission mode or a reception mode. For example, during DPD calibration, the first communication chain 210a and the third communication chain 210c may be in a transmission mode, while the second communication chain 210b may be in a reception mode. For another example, during DPD calibration, the first communication chain 210a may be in a reception mode, and the second communication chain 210b and the third communication chain 210c may be in a transmission mode. Alternatively, during DPD calibration, a single communication chain in the communication chain 210 may be in a transmission mode, while a single communication chain in the communication chain 210 may be in a reception mode, with the remaining communication chains 210 being turned off.

[0034] The first communication chain 210a may include a first PA 214a. The second communication chain 210b may include a second PA 214b. The third communication chain 210c may include a third PA 214c. The first PA 214a, the second PA 214b, and the third PA 214c may provide non-linear amplification of signals to be transmitted by the corresponding communication chain 210. To compensate for the non-linear amplification, a DPD calibration and a DPD application may be performed on one or more of the communication chains 210.

[0035] In some implementations, DPD calibration can be performed before, during, or after operation of MIMO transceiver 217. For example, DPD calibration can be performed during installation of MIMO transceiver 217 in environment 100. As another example, DPD calibration can be performed after a certain time interval has passed since the last time DPD calibration was performed.

[0036] In some implementations, after the time interval has elapsed, the talk duration detector circuit 224 may determine whether communication is occurring between one or more of the communication chains 210 and the computing device 105. For example, in some implementations, the talk duration detector circuit 224 may determine whether a transmit portion of the communication chain 210 is transmitting and / or whether a receive portion of the communication chain 210 is receiving. In some implementations, if communication is occurring, the MIMO transceiver 217 may wait for the communication to end before performing a DPD calibration. Alternatively, in some implementations, before the MIMO transceiver 217 performs a DPD calibration, the talk duration detector circuit 224 may determine whether the communication is below a communication threshold. For example, the talk duration detector circuit 224 may determine whether the received signal strength from the computing device 105 on one or more receive portions of the communication chain 210 is below a threshold such that a signal received by the receive portion will not interfere with a signal wirelessly transmitted by the transmit portion of the communication chain 210. The threshold may be determined by subtracting the interference requirement signal programmed on the DPD circuit 220 from the expected received signal strength of the signal wirelessly transmitted (e.g., via wireless coupling) between the transmit portion and the receive portion of the communication chain. As another example, DPD calibration may be performed only during a specified time period (e.g., between 10 p.m. and 7 a.m.) or triggered by certain events (e.g., a temperature change greater than a threshold temperature change since the last DPD calibration, a MIMO transmission frequency update, etc.).

[0037] An example of DPD calibration and DPD application will now be discussed, which involves a first communication chain 210a in a transmission mode and a second communication chain 210b in a reception mode. The first communication chain 210a may include one or more of a first predistorter circuit 212a, a first PA 214a, a first communication module 216a, a first buffer 213a, and / or a first converter circuit 215a. Similarly, the second communication chain 210b may include one or more of a second predistorter circuit 212b, a second PA 214b, a second buffer 213b, a second converter circuit 215b, and / or a second communication module 216b. Each communication module in the communication module 216 may include a transmission portion and a reception portion. For example, the first communication module 216a may include a first transmission portion 219a and a first reception portion 221a. As another example, the second communication module 216b may include a second transmission portion 219b and a second reception portion 221b. The first predistorter circuit 212a may accept first predistortion parameters to predistort the signal before transmission by the first communication module 216a. Additionally, the first PA 214a may amplify the signal before transmission by the first communication module 216a.

[0038] The first communication chain 210a can generate a first signal at a first frequency. In some implementations, the first frequency can include a frequency within an RF band. The first PA 214a can amplify the power level of the first signal from an initial power level to an amplified power level. The first communication module 216a can receive the first signal at the first frequency and the amplified power level. In addition, the first transmission portion 219a of the first communication module 216a can wirelessly transmit the first signal at the first frequency and the amplified power level.

[0039] The second receiving portion 221b of the second communication module 216b can wirelessly receive the first signal at the first frequency and the amplified power level. Figure 2 As shown, in some embodiments, the first transmitting portion 219a and the second receiving portion 221b may be wirelessly coupled via OTA coupling. Figure 2 The box labeled "OTA coupling" in FIG. 1 is shown for exemplary purposes, and more generally, the first transmission portion 219a can be wirelessly coupled to any or all of the second reception portion 221b, the third communication module 216c, and the Nth communication module 216n. In addition, the second reception portion 221b can be wirelessly coupled to any or all of the first transmission portion 219a, the third communication module 216c, and the Nth communication module 216n. In some specific implementations, the second communication module 216b may include an external variable low noise amplifier (LNA) ( Figure 2). In these and other specific implementations, the external variable LNA of the second communication module 216b can receive the first signal at the first frequency and the amplified power level. In addition, the external variable LNA of the second communication module 216b can amplify the first signal at the first frequency to the first intermediate power level.

[0040] In some implementations, the second converter circuit 215b can receive the first signal at the first frequency and the first intermediate power level from the second communication module 216b. In other implementations, the second converter circuit 215b can receive the first signal at the first frequency and the amplified power level from the second communication module 216b.

[0041] In some implementations, the second converter circuit 215b may include an internal variable LNA ( Figure 2 215b). In these and other specific implementations, the internal variable LNA of the second converter circuit 215b may receive the first signal at the first frequency and the first intermediate power level. In addition, the internal variable LNA of the second converter circuit 215b may amplify the first signal at the first frequency to the second intermediate power level. The amplification of the first signal by the external variable LNA of the second communication module 216b and the internal variable LNA of the second converter circuit 215b may be provided to compensate for insertion losses introduced by components in the second converter circuit 215b and / or the second buffer 213b (e.g., the receiving portion of the second communication link 210b may be configured as a linear receiver, as discussed elsewhere in this disclosure).

[0042] The second converter circuit 215b may down-convert the first signal to a baseband frequency. In some implementations, the second buffer 213b may receive and buffer the first signal at the baseband frequency and the second intermediate power level. In other implementations, the second buffer 213b may receive and buffer the first signal at the baseband frequency and the amplified power level. In some implementations, insertion losses introduced by the components in the second converter circuit 215b and / or the second buffer 213b used to down-convert the first signal to the baseband frequency may cause the power level of the first signal to be changed to the amplified power level at the output of the second buffer 213b.

[0043] The DPD circuit 220 may include a chain isolator circuit 222 and an inverter circuit 226. The chain isolator circuit 222 may receive the first signal at the baseband frequency and the amplified power level from the second buffer 213b (e.g., receive the buffered signal at the first frequency). The chain isolator circuit 222 may also receive the first signal at the baseband frequency and the initial power level. The chain isolator circuit 222 may provide the first signal at the baseband frequency and the initial power level to the inverter circuit 226. In addition, the chain isolator circuit 222 may provide the first signal at the baseband frequency and the amplified power level to the inverter circuit 226.

[0044] The inverter circuit 226 can calibrate the first predistortion parameter based on the first signal received from the second buffer 213b. The first predistortion parameter can be calibrated to compensate for the amplified nonlinearity of the first signal provided by the first PA 214a. For example, in some implementations, the first predistortion parameter can be calibrated as the additive inverse of the amplified nonlinearity provided by the first PA 214a.

[0045] In some implementations, the inverter circuit 226 can determine the difference between the first signal at the baseband frequency and the amplified power level and the expected signal at the baseband frequency and the expected power level. The inverter circuit 226 can calibrate the first predistortion parameter based on the difference between the amplified power level and the expected signal.

[0046] In some implementations, the inverter circuit 226 may determine an average power level and an initial power level of samples of the first signal at the baseband frequency (e.g., the first signal before being amplified by the first PA 214a). In addition, the inverter circuit 226 may normalize the average power level of samples of the first signal before being amplified by the first PA 214a to the power level of the signal transmitted by one or more of the communication links 210. The expected power level may be the normalized average power level of the first signal before being amplified by the first PA 214a. The inverter circuit 226 may compare the amplified power level of the first signal at the baseband frequency with the expected power level. The inverter circuit 226 may calibrate the first predistortion parameter based on the difference between the amplified power level and the expected power level.

[0047] In some implementations, the inverter circuit 226 can compare the first signal at the baseband frequency and the amplified power level (e.g., the power level of the first signal after amplification by the first PA 214a) with the first signal at the baseband frequency and the initial power level (e.g., the power level of the first signal before amplification by the first PA 214a). A difference between the amplified power level and the initial power level can be determined (e.g., a difference between the power levels of the first signal before and after amplification by the first PA 214a can be determined). The difference between the amplified power level and the initial power level can be compared to an amplification level expected to be provided by the first PA 214a. The inverter circuit 226 can calibrate the first predistortion parameters based on the difference between the amplified power level and the initial power level compared to the amplification level expected to be provided by the first PA 214a.

[0048] The inverter circuit 226 may provide the first predistortion parameter to the first predistorter circuit 212a. The first predistorter circuit 212a may predistort a subsequent signal transmitted by the first communication module 216a based on the first predistortion parameter. For example, the first predistorter circuit 212a may predistort the subsequent signal to be equal to the additive inverse of the amplified nonlinearity provided by the first PA 214a. The predistortion of the subsequent signal may cause the subsequent signal to be more linear when received by the computing device 105.

[0049] An example of DPD calibration and DPD application will now be discussed, which involves the third communication chain 210a in the transmission mode and the second communication chain 210b in the reception mode. The third communication chain 210c may include one or more of a third predistorter circuit 212c, a third PA 214c, a third communication module 216c, a third buffer 213c, and / or a third converter circuit 215c. The third predistorter circuit 212c may accept a third predistortion parameter to predistort the signal before being transmitted by the third communication module 216c. In addition, the third PA 214c may amplify the signal before being transmitted by the third communication module 216c.

[0050] In some implementations, the DPD circuit 220 may further include a chain selector circuit 218. The chain selector circuit 218 may selectively control which communication chain 210 generates a corresponding signal for performing DPD calibration. In these and other implementations, the chain selector circuit 218 may provide a transmission signal to the communication chain 210 in response to the calibration of the first predistortion parameter. The transmission signal may indicate that the first communication chain 210a will stop generating the first signal. Additionally or alternatively, the transmission signal may indicate that the first communication chain 210a will stop wireless transmission of the first signal. In addition, the transmission signal may indicate that the third communication chain 210c will begin generating a third signal at the first frequency.

[0051] The third communication chain 210c may generate a third signal at the first frequency. The third PA 214c may amplify the power level of the third signal at the first frequency to an amplified power level. The third communication module 216c may receive the third signal at the amplified power level from the first PA 214a. In addition, the third communication module 216c may wirelessly transmit the third signal at the first frequency and the amplified power level.

[0052] The second communication module 216b can wirelessly receive the third signal at the first frequency and the amplified power level. In some implementations, the external variable LNA of the second communication module 216b can receive the third signal at the first frequency and the amplified power level. In addition, the external variable LNA of the second communication module 216b can amplify the third signal at the first frequency to a first intermediate power level.

[0053] The second converter circuit 215b can receive the third signal at the first frequency and the first intermediate power level from the second communication module 216b. In some implementations, the internal variable LNA of the second converter circuit 215b can receive the third signal at the first frequency and the first intermediate power level. In addition, the internal variable LNA of the second converter circuit 215b can amplify the third signal at the first frequency to the second intermediate power level.

[0054] The second converter circuit 215b can down-convert the third signal to a baseband frequency. The second buffer 213b can receive and buffer the third signal at the baseband frequency and the second intermediate power level. In some implementations, insertion losses introduced by the components in the second converter circuit 215b and / or the second buffer 213b for down-converting the third signal to a baseband frequency can cause the power level of the third signal to become an amplified power level at the output of the second buffer 213b.

[0055] The chain isolator circuit 222 may receive the third signal at the baseband frequency and the amplified power level from the second buffer 213 b. The chain isolator circuit 222 may also receive the third signal at the baseband frequency and the initial power level (e.g., before being amplified by the third PA 214 c). The chain isolator circuit 222 may provide the third signal at the baseband frequency and the initial power level to the inverter circuit 226. In addition, the chain isolator circuit 222 may provide the third signal at the baseband frequency and the amplified power level to the inverter circuit 226.

[0056] The inverter circuit 226 may calibrate the third predistortion parameters to compensate for nonlinearity of amplification of the third signal provided by the third PA 214c. The inverter circuit 226 may calibrate the third predistortion parameters in the same or similar manner as discussed above with respect to the first predistortion parameters. In addition, the third predistorter circuit 212c may predistort subsequent signals transmitted by the third communication module 216c based on the third predistortion parameters in the same or similar manner as the first predistorter circuit 212a predistorts subsequent signals to be transmitted by the first communication module 216a based on the first predistortion parameters.

[0057] An example of DPD calibration and DPD application will now be discussed, which involves the second communication chain 210b in the transmission mode and the first communication chain 210a in the reception mode. In response to the calibration of the first pre-distortion parameter and / or the third pre-distortion parameter, the chain selector circuit 218 may provide a transmission signal to the communication chain 210. The transmission signal may indicate that the third communication chain 210c will stop generating the third signal and the second communication chain 210b will start generating the second signal. In addition, the transmission signal may indicate that the second communication chain 210b will be in the transmission mode and the first communication chain 210a will be in the reception mode. The following discussion uses the first communication chain 210a to perform DPD calibration of the second communication chain 210b; more generally, any other communication chain 210 other than the second communication chain 210b can be used for DPD calibration of the second communication chain 210b.

[0058] The second predistorter circuit 212b may accept second predistortion parameters to predistort the signal before transmission by the second communication module 216b. Additionally, the second PA 214b may amplify the signal before transmission by the second communication module 216b.

[0059] The second communication chain 210b may generate a second signal at a first frequency. The second PA 214b may amplify the power level of the second signal to an amplified power level. The second communication module 216b may receive the second signal at the first frequency and the amplified power level. In addition, the second communication module 216b may wirelessly transmit the second signal at the first frequency and the amplified power level.

[0060] The first communication module 216a can wirelessly receive the second signal at the first frequency and amplified power level. In some implementations, the first communication module 216a can include another external variable LNA ( Figure 2 ). In these and other specific implementations, the external variable LNA of the first communication module 216a can receive the second signal at the first frequency and the amplified power level. In addition, the external variable LNA of the first communication module 216a can amplify the second signal at the first frequency to the first intermediate power level.

[0061] The first converter circuit 215a can receive a second signal at a first frequency and a first intermediate power level from the first communication module 216a. In some implementations, the first converter circuit 215a can include another internal variable LNA ( Figure 2 215a). In these and other specific implementations, the internal variable LNA of the first converter circuit 215a may receive the second signal at the first frequency and the first intermediate power level. In addition, the internal variable LNA of the first converter circuit 215a may amplify the second signal at the first frequency to the second intermediate power level. The amplification of the second signal by the external variable LNA of the first communication module 216a and / or the internal variable LNA of the first converter circuit 215a may be provided to compensate for insertion losses introduced by components in the first converter circuit 215a and / or the first buffer 213a (e.g., the receiving portion of the first communication link 210a may be configured as a linear receiver, as discussed elsewhere in this disclosure).

[0062] The first converter circuit 215a can down-convert the second signal to a baseband frequency and a second intermediate power level. The first buffer 213a can receive and buffer the second signal at the baseband frequency and the second intermediate power level. In some implementations, insertion losses introduced by the first converter circuit 215a and components in the first buffer 213a for down-converting the second signal to a baseband frequency can cause the power level of the second signal to become an amplified power level at the output of the first buffer 213a.

[0063] The chain isolator circuit 222 may receive the second signal at the baseband frequency and the amplified power level from the first buffer 213a. The chain isolator circuit 222 may also receive the second signal at the baseband frequency and the original power level (e.g., before being amplified by the second PA 214b). The chain isolator circuit 222 may provide the second signal at the baseband frequency and the original power level to the inverter circuit 226. In addition, the chain isolator circuit 222 may provide the second signal at the baseband frequency and the amplified power level to the inverter circuit 226.

[0064] The inverter circuit 226 may calibrate the second predistortion parameters to compensate for the nonlinearity of the amplification of the second signal provided by the second PA 214 b. The inverter circuit 226 may calibrate the second predistortion parameters in the same or similar manner as discussed above with respect to the first predistortion parameters. In addition, the second predistorter circuit 212 b may predistort the subsequent signal based on the second predistortion parameters in the same or similar manner as the first predistorter circuit 212 a may predistort the subsequent signal based on the first predistortion signal.

[0065] In some implementations, in response to calibration of one or more of the predistortion parameters, the MIMO transceiver 217 can verify the DPD calibration and the execution of the DPD application for the corresponding communication link 210. In these and other implementations, one or more link parameters for the corresponding communication link 210 can be determined. The link parameters after the DPD calibration and the DPD application are performed can be compared to the corresponding link parameters before the DPD calibration and the DPD application are performed. The link parameters can include an error vector magnitude (EVM), a modulation coding scheme (MCS), an output power level on the corresponding PA 214, or any other suitable link parameters.

[0066] In some implementations, the chain isolator circuit 222 may receive a combined signal. The combined signal may include a first signal, a second signal, a third signal, or any other signal at a first frequency for performing DPD calibration. The chain isolator circuit 222 may isolate different signals included in the combined signal. Isolation of different signals included in the combined signal according to some embodiments is discussed in U.S. Patent Application No. 15 / 826,632, entitled “MIMO WIFI Transceiver with Rolling Gain Offset Pre-Distortion Calibration” filed on July 15, 2019, which is incorporated by reference into the present disclosure.

[0067] In some implementations, the combined signal can be used to simultaneously perform DPD calibration for two or more communication chains 210. In other implementations, the combined signal can be used to perform DPD calibration for subsequent communication chains without stopping transmission of signals for the communication chains 210 that previously performed DPD calibration. For example, if DPD calibration was previously being performed for the first communication chain 210a and DPD calibration is to be performed for the second communication chain 210b, the chain isolator circuit 222 can allow the first communication chain 210a to continue transmitting the first signal while the second communication chain 210b transmits the second signal.

[0068] To isolate the different signals, the chain isolator circuit 222 may monitor the different signals at the initial power level. In addition, the chain isolator circuit 222 may scale the various signals from the initial power level and subtract the scaled signals from the combined signal, except for the scaled signal corresponding to the communication chain 210 for which the DPD calibration is performed (e.g., a subtracted signal may be generated). The chain isolator circuit 222 may provide the subtracted signal to the inverter circuit 226. The inverter circuit 226 may use the subtracted signal to calibrate the corresponding predistortion parameters in the same or similar manner as discussed above with respect to calibrating the first predistortion parameters using the first signal.

[0069] In some implementations, in addition to wirelessly transmitting signals for performing DPD calibration, the communication link 210 can also transmit signals representing data to be provided to the computing device 105. For example, the first PA 214a can amplify the signal representing the data, and the first communication module 216a can wirelessly transmit the signal representing the data to the computing device 105.

[0070] The receiving portion of the communication link 210 may be a linear receiver. The specific components of the receiving portion are described below with respect to Figure 3 214. The receiving section configured as a linear receiver can allow various signals to propagate through components within the receiving section without introducing insertion loss. The receiving section configured as a linear receiver can ensure that the various signals received by the DPD circuit 220 are at the same or similar power levels as the power levels of the various signals after being amplified by the corresponding PA 214. In addition, the receiving section configured as a linear receiver can avoid distortion of the various signals in the receiving section and can ensure that any difference in power levels detected by the DPD circuit 220 is caused by the corresponding PA 214.

[0071] In some implementations, the best communication chain in the communication chains 210 can be selected for performing DPD calibration based on one or more corresponding link parameters. For example, in some implementations, the best communication chain 210 can be selected based on EVM, MCS, output power level on the corresponding PA 214, or any other suitable link parameter. In some implementations, DPD calibration for the best communication chain can be performed, and predistortion parameters calibrated for the best communication chain can be used for DPD application for each communication chain in the communication chains 210. For example, the first predistortion parameters can be provided to the second predistorter circuit 212b and the third predistorter circuit 212c to predistort the second signal and the third signal, respectively.

[0072] Figure 2 An implementation of a MIMO transceiver 217 having more than two communication chains 210 is shown. In another implementation, the MIMO transceiver 217 may include exactly two communication chains 210. In such an implementation, the chain isolator circuit 222 may be omitted from the DPD circuit 220. Alternatively or additionally, the chain isolator circuit 222 may be omitted from the DPD circuit 220, wherein the MIMO transceiver 217 includes more than two communication chains 210, and wherein the MIMO transceiver 217 operates the communication chains 210 as transmit chains one at a time, along with one communication chain 210 operating as a receive chain during DPD calibration.

[0073] Figure 3 It shows that at least one specific implementation disclosed in the present disclosure can be Figure 2DPD circuit 220 and exemplary communication chains 335a-b implemented in MIMO transceiver 217 of FIG. The first communication chain 335a and the second communication chain 335b (collectively referred to as "communication chain 335" in this disclosure) may correspond to Figure 2 Communication link 210. Figure 3 The first communication chain 335a is shown as having both a transmit chain and a receive chain. Although the second communication chain 335b is Figure 3 is shown with only a receive chain, but it may also include a transmit chain.

[0074] The communication link 335 may include baseband circuits 329a-b, converter circuits 331a-b, and communication modules 333a-b. The baseband circuits 329a-b and the communication modules 333a-b may correspond to Figure 2 The converter circuit 215 and the communication module 216 of the embodiment of the present invention are shown in Figure 2. The communication chain 335 can be configured in a receive mode or a transmit mode. In addition, the communication chain 335 can transmit a calibration signal for performing DPD calibration or a signal representing data to be received by the computing device 105. In addition, the communication chain 335 can be configured to receive a signal representing data from the computing device 105 and / or receive a calibration signal output by other communication chains on the same MIMO transceiver as the communication chain 335.

[0075] An example of generating and processing calibration signals by the communication chain 335 for performing DPD calibration and DPD application will now be discussed. In this example, DPD calibration of the first communication chain 335a is performed via OTA coupling to the second communication chain 335b. The same process may be applied, mutatis mutandis, to perform DPD calibration of the second communication chain 335b (or other communication chain 335) via OTA coupling to the first communication chain 335a (or other communication chain 335).

[0076] The transmission calibration buffer 330 of the first communication chain 335a may receive and buffer an internal calibration signal (e.g., a first signal, a second signal, or a third signal) at a baseband frequency. The transmission MUX 328 of the first communication chain 335a may selectively provide an internal calibration signal at a baseband frequency or a signal representing data at a baseband frequency. Specifically, the transmission MUX 328 may select the output of the transmission calibration buffer 330 or the predistorter circuit 212 of the first communication chain 335a to output for further processing. During the execution of the DPD calibration, the transmission MUX 328 may provide the internal calibration signal at a baseband frequency to a digital-to-analog converter (DAC) 332 of the first communication chain 335a. The DAC 332 may convert the internal calibration signal at a baseband frequency from a digital signal to an analog signal (e.g., may generate an internal analog calibration signal). In some specific implementations, the DAC 332 may generate a first component and a second component of the internal calibration signal. For example, the DAC 332 may include two internal DACs, each of which generates a different one of the first component and the second component of the internal calibration signal. In these and other implementations, the first component and the second component of the internal calibration signal can be the real and imaginary parts of the internal analog calibration signal.

[0077] A first transmission filter 334a and a second transmission filter 334b ​​(collectively referred to in the present disclosure as "transmission filters 334") of the first communication link 335a can receive a first component and a second component of the internal calibration signal from the DAC 332, respectively. The transmission filter 334 can be configured to filter out portions of the first component and the second component of the internal calibration signal. For example, in some implementations, the transmission filter 334 can be configured to filter noise from the first component and the second component of the internal calibration signal. In some implementations, the transmission filter 334 can include a bandpass filter, a lowpass filter, a highpass filter, or any other suitable filter.

[0078] The first transmission variable amplifier 336a and the second transmission variable amplifier 336b (collectively referred to as "transmission variable amplifiers 336" in the present disclosure) of the first communication link 335a may receive the first component and the second component of the internal calibration signal from the transmission filter 334 at the initial power level, respectively. The transmission variable amplifier 336 may be configured to provide a variable gain to the first component and the second component of the internal calibration signal. The transmission variable amplifier 336 may amplify the first component and the second component of the internal calibration signal to a first power level.

[0079] The first transmission mixer 338a and the second transmission mixer 338b of the first communication chain 335a (collectively referred to as "transmission mixer 338" in this disclosure) can receive the first component and the second component of the internal calibration signal at a first power level, respectively. In some specific implementations, the transmission mixer 338 can also receive a shifted signal at a shifted frequency. The shifted frequency can be equal to the frequency difference between the baseband frequency and the first frequency. The transmission mixer 338 can use the shifted signal to up-convert the frequencies of the first component and the second component of the internal calibration signal from the baseband frequency to the first frequency. For example, the first transmission mixer 338a can up-convert the first component of the internal calibration signal to the first frequency. For another example, the second transmission mixer 338b can up-convert the second component of the internal calibration signal to the first frequency. In some embodiments, the first component and the second component of the internal calibration signal can be up-converted by the orthogonal components of the RF voltage controlled oscillator (VCO).

[0080] The adder 340 of the first communication chain 335a may receive a first component and a second component of an internal calibration signal at a first frequency and a first power level. The adder 340 may combine the first component and the second component of the internal calibration signal into an internal analog calibration signal at a first frequency and a first power level. For example, the adder 340 may mix the first component and the second component of the internal calibration signal into a single RF waveform. The PA 214 of the first communication chain 335a may receive and amplify the internal analog calibration signal at the first frequency. For example, the PA 214 may amplify the internal analog calibration signal at the first frequency to a second power level (e.g., the internal calibration signal at the first frequency may be amplified to an operating power level of the PA 214). The PA 214 may provide nonlinear amplification, for which predistortion parameters may be calibrated to compensate.

[0081] The switches 344a-b of the communication chain 335 can be selectively switched between a transmission position and a reception position. In the transmission position, the communication chain 335 can be in a transmission mode, for example, the communication module 333a can be coupled through the switch 344a to wirelessly transmit a signal received from the transmission chain of the first communication chain 335a. In the reception position, the communication chain 335 can be in a reception mode, for example, the communication module 333a can wirelessly receive a signal that can be coupled to the reception chain of the first communication chain 335a through the switch 344a.

[0082] Continuing with the exemplary DPD calibration process, the switch 344a may receive an internal analog calibration signal at a first frequency and a second power level from the PA 214. Additionally, the switch 344a may provide the internal analog calibration signal at the first frequency and the second power level to the antenna 346a of the first communication chain 335a in the transmit position. The antenna 346a may wirelessly transmit the internal analog calibration signal at the first frequency and the second power level to one or more other communication chains 210, such as the second communication chain 335b.

[0083] The internal calibration signal wirelessly transmitted by antenna 346a of first communication link 335a is received by antenna 346b as an external calibration signal at a first frequency and a second power level.

[0084] The switch 344b of the second communication chain 335b may receive the external calibration signal from the antenna 346b. In addition, the switch 344b in the receiving position may provide the external calibration signal at the first frequency and the second power level to the external amplifier 348b of the second communication chain 335b (e.g., as described above with respect to Figure 2 The external amplifier 348b may amplify the external calibration signal. For example, the external amplifier 348a may amplify the external calibration signal at the first frequency to a third power level. In some implementations, the external amplifier 348b may be omitted.

[0085] The internal amplifier 350b of the second communication chain 335b may receive an external calibration signal at a first frequency and a third power level. In addition, the internal amplifier 350b may amplify the external calibration signal at the first frequency to a fourth power level. The subtractor 352b of the second communication chain 335b may receive the external calibration signal at the first frequency and the fourth power level from the internal amplifier 350b. The subtractor 352b may separate the external calibration signal into a third component and a fourth component at the first frequency and the fourth power level. In some implementations, the third component and the fourth component may be the real part and the imaginary part of the external calibration signal.

[0086] The first receive mixer 354c of the second communication chain 335b and the second receive mixer 354d of the second communication chain 335b can receive the third component and the fourth component of the external calibration signal at the first frequency and the fourth power level. In some implementations, the receive mixers 354c-d can also receive the shifted signal at the shifted frequency. The receive mixers 354c-d can use the shifted signal to down-convert the frequency components of the third component and the fourth component of the external calibration signal from the first frequency to the baseband frequency.

[0087] The first receive variable amplifier 356c and the second receive variable amplifier 356d of the second communication chain 335b may receive the third component and the fourth component (e.g., the real part and the imaginary part of the external calibration signal) of the external calibration signal at the baseband frequency and the fourth power level, respectively. The receive variable amplifiers 356c-d may amplify the third component and the fourth component of the external calibration signal to a fifth power level.

[0088] In some implementations, the third power level, the fourth power level, and the fifth power level can be determined based on the insertion loss of other components in the receiving portion of the second communication link 335b. Amplifying the third and fourth components of the external calibration signal (e.g., the real and imaginary parts of the external calibration signal) to the third power level, the fourth power level, and the fifth power level to compensate for the insertion loss of the components in the receiving portion can cause the receiving portion to be configured as a linear receiver.

[0089] The first receive filter 358c and the second receive filter 358d of the second communication chain 335b may receive the third component and the fourth component of the external calibration signal, respectively (e.g., the real component and the imaginary component of the external calibration signal). In addition, the receive filters 358c-d may filter out portions of the third component and the fourth component of the external calibration signal. In some specific implementations, the receive filters 358c-d may include a bandpass filter, a low-pass filter, a high-pass filter, or any other appropriate filter. In some specific implementations, the receive filters 358c-d may be configured to filter out noise from the third and fourth components of the external calibration signal. The analog-to-digital converter (ADC) 360b of the second communication chain 335b may receive the third component and the fourth component of the external calibration signal at the baseband frequency and the fifth power level from the receive filters 358c-d. ADC 360b may combine and convert the third component and the fourth component of the calibration signal into a digital signal at the baseband frequency and the fifth power level (e.g., a digital calibration signal may be generated).

[0090] The receive MUX 362b of the second communication chain 335b may selectively provide a digital calibration signal at a baseband frequency or a signal representing data at a baseband frequency to a receive calibration buffer 364b of the second communication chain 335b or a receive processing circuit 366b of the second communication chain 335b, respectively. During the performance of the DPD calibration, the receive MUX 362b may provide the digital calibration signal to the receive calibration buffer 364b. The receive calibration buffer 364b may buffer the digital calibration signal. In addition, the receive calibration buffer 364b may provide the digital calibration signal (e.g., a buffered calibration signal) to the chain isolator circuit 222 of the DPD circuit 220. The chain isolator circuit 222 and / or the inverter circuit 226 of the DPD circuit 220 may calibrate the pre-distortion parameters of the first communication chain 335a based on the buffered calibration signal received from the second communication chain 335b, as described above with respect to Figure 2 discussed.

[0091] The inverter circuit 226 may then provide the predistortion parameters to the predistorter circuit 212 of the first communication chain 335a. The predistorter circuit 212 may predistort the subsequent signal based on the predistortion parameters. For example, the predistorter circuit 212 may predistort the signal representing the data received from the transmission output circuit 327 of the first communication chain 335a. The baseband circuit 329a, the converter circuit 331a, and the communication module 333a of the first communication chain 335a may process the signal representing the data in the same or similar manner as the calibration signal. The receive processing circuits 366a, 336b may receive the signal representing the data from the receive MUXs 362a, 362b, respectively, for additional processing.

[0092] The first communication chain 335a may include one or more of an external amplifier 348a, an internal amplifier 350a, a subtractor 352a, a first mixer 354a, a second mixer 354b, a first receive variable gain amplifier 356a, a second receive variable gain amplifier 356b, a first receive filter 358a, a second receive filter 358b, an ADC 360a, a receive multiplexer 362, a receive calibration buffer 364a, and a receive processing circuit 366a. Each of these components in the first communication chain 335a may operate in the same or similar manner as the corresponding components in the second communication chain 335b.

[0093] although Figure 3 327, a predistorter circuit 212, a transmit MUX (similar to transmit MUX 328), a DAC (similar to DAC 332), a first transmit filter and a second transmit filter (similar to transmit filters 336a-b), a first and a second transmit variable gain amplifier (similar to transmit variable gain amplifiers 336a-b), a first and a second transmit mixer (similar to transmit mixers 338a-b), an adder (similar to adder 340), and one or more of PA 214, each of which components in the second communication chain 335b may operate in the same or similar manner as the corresponding components in the first communication chain 335a.

[0094] For illustrative purposes, the Figure 3 More generally, the first communication link 335a may be wirelessly coupled to any suitable communication link 210, 335 within the MIMO transceiver 217.

[0095] Figure 4An exemplary environment 400 including a WAP 401 and STAs 403a, 403b according to at least one implementation disclosed in the present disclosure is shown. Each of the WAP 401 and the STAs 403a, 403b includes a first MIMO transceiver 407a, a second MIMO transceiver 407b, or a third MIMO transceiver 407c (collectively referred to herein as MIMO transceivers 407). Each of the MIMO transceivers 407 may correspond to Figure 1 and Figure 2 MIMO transceivers 102 and 217.

[0096] The first MIMO transceiver 407a may include a clear to send (CTS) circuit 409. Figure 4 4. Although not shown in the figure, either or both of the second MIMO transceiver 407b and the third MIMO transceiver 407c may include similar CTS circuits. The CTS circuit 409 may transmit a CTS-to-self signal. The CTS-to-self signal may preserve the first MIMO transceiver 407a using the communication link 210 ( Figure 4 In some implementations, the CTS-to-self signal may indicate a duration for which the second MIMO transceiver 407b and / or the third MIMO transceiver 407c did not wirelessly transmit a signal at least at the first frequency. Reserving the duration for the first MIMO transceiver 407a to perform DPD calibration may avoid uplink interference caused by signals transmitted by the second MIMO transceiver 407b or the third MIMO transceiver 407c.

[0097] Figure 5 A flow chart of an exemplary method 500 of operating a MIMO transceiver according to at least one implementation disclosed in the present disclosure is shown. In some implementations, the method of operating a MIMO transceiver can allow for DPD calibration of a communication link to be performed using OTA coupling between communication links. The method 500 can be performed by any suitable system, apparatus, or device for DPD calibration of a communication link within a MIMO transceiver. For example, Figure 1 , Figure 2 and Figure 4 The DPD calibration of the MIMO transceivers 102, 217, and 407 with respect to the communication link 210 may perform or direct the performance of one or more of the operations associated with the method 500. Although illustrated by separate blocks, the steps and operations associated with one or more of the blocks of the method 500 may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the particular implementation.

[0098] Method 500 may include block 502, where a signal at a first frequency may be wirelessly transmitted. In some implementations, the signal at the first frequency may be wirelessly transmitted from a first communication link of a MIMO transceiver. For example, the signal at the first frequency may be transmitted from a first communication link of a MIMO transceiver. Figure 2 The first communication module 216a of the first communication chain 210a wirelessly transmits. In these and other specific implementations, the first communication chain may include a predistorter circuit that receives a predistortion parameter to predistort the signal before transmission. For example, Figure 2 The first predistorter circuit 212a may receive a first predistortion parameter to predistort the signal before transmission. In addition, the first communication link may include a PA that amplifies the signal of the first communication link before transmission. For example, Figure 2 The first PA 214a may amplify the signal before transmission by the first communication module 216a.

[0099] At block 504, a signal at a first frequency may be wirelessly received. In some implementations, a signal at a first frequency may be wirelessly received at a second communication link of a MIMO transceiver. For example, the signal may be received via Figure 2 The signal may be wirelessly received by the second communication module 216b. At block 506, the signal may be converted to baseband frequency. In some implementations, the signal may be received wirelessly by the second communication module 216b. Figure 2 The second converter circuit 215b converts the signal at the baseband frequency to the baseband frequency. At block 508, the signal at the baseband frequency may be buffered. For example, Figure 2 The second buffer 213b buffers the signal at the baseband frequency.

[0100] At block 510, predistortion parameters may be calibrated. In some implementations, the predistortion parameters may be calibrated based on the buffered signal. In these and other implementations, the predistortion parameters may be calibrated to compensate for nonlinearity of amplification provided by the PA of the first communication chain. For example, the first predistortion parameters may be Figure 2 The DPD circuit 220 is calibrated to compensate for the non-linearity of the amplification provided by the first PA 214a.

[0101] Method 500 may be modified, added to, or omitted without departing from the scope of the present disclosure. For example, the operations of method 500 may be implemented in a different order. Additionally or alternatively, two or more operations of method 500 may be performed simultaneously. Furthermore, the operations and actions outlined in method 500 are provided only as examples, and some operations and actions may be optional, combined into fewer operations and actions, or expanded into additional operations and actions without departing from the essence of the disclosed specific implementation. Furthermore, in some specific implementations, method 500 may be performed iteratively, wherein one or more operations may be performed for multiple communication chains in a MIMO transceiver.

[0102] An exemplary MIMO transceiver configured for DPD calibration includes a first communication chain, a second communication chain, and a DPD circuit. The first communication chain is configured to wirelessly transmit a signal at a first frequency. The first communication chain includes a predistorter circuit and a PA, the predistorter circuit is configured to receive a predistortion parameter to predistort the signal before transmission, and the PA is configured to amplify the signal of the first communication chain before transmission. The second communication chain is configured to wirelessly receive a signal at a first frequency and includes a converter circuit and a buffer. The converter circuit is configured to convert the signal to a baseband frequency. The buffer is configured to buffer the signal at the baseband frequency. The DPD circuit is configured to calibrate the predistortion parameter based on the buffered signal to compensate for the nonlinearity of the amplification provided by the PA of the first communication chain.

[0103] In the MIMO transceiver, the second communication chain may further include an ADC configured to convert a signal at a baseband frequency into a digital signal. The second communication chain may further be configured to wirelessly transmit a signal at the first frequency. The first communication chain may further include a DAC configured to convert a signal at a baseband frequency into an analog signal.

[0104] An exemplary method for operating a MIMO transceiver configured for DPD calibration includes wirelessly transmitting a signal at a first frequency from a first communication chain of the MIMO transceiver. The first communication chain includes a predistorter circuit and a PA, the predistorter circuit is configured to accept predistortion parameters to predistort the signal before transmission, and the PA is configured to amplify the signal of the first communication chain before transmission. The method includes wirelessly receiving the signal at the first frequency at a second communication chain of the MIMO transceiver. The method includes converting the signal to a baseband frequency by the second communication chain. The method includes buffering the signal at the baseband frequency by the second communication chain. The method includes calibrating the predistortion parameters based on the buffered signal to compensate for the nonlinearity of the amplification provided by the PA of the first communication chain.

[0105] The method may also include transmitting a CTS-to-Self signal to other MIMO transceivers within the operating environment of the MIMO transceiver.The CTS-to-Self signal may reserve a duration for the MIMO transceiver to perform DPD calibration using the first communication chain and the second communication chain.

[0106] The signal in the method may include a first signal, the predistorter circuit may include a first predistorter circuit, the PA may include a first PA, and the predistortion parameter may include a first predistortion parameter. In response to calibrating the first predistortion parameter, the method may also include: stopping wirelessly transmitting the first signal from a first communication chain of the MIMO transceiver; starting wirelessly transmitting a second signal at a first frequency from a second communication chain of the MIMO transceiver, the second communication chain including a second predistorter circuit and a second PA, the second predistorter circuit being configured to accept a second predistortion parameter to predistort the signal before transmission, and the second PA being configured to amplify the signal of the second communication chain before transmission; wirelessly receiving the second signal at the first frequency at the first communication chain of the MIMO transceiver; converting the second signal to a baseband frequency through the first communication chain; buffering the second signal at the baseband frequency through the first communication chain; and calibrating the second predistortion parameter based on the buffered second signal to compensate for nonlinearity of amplification provided by the second PA of the second communication chain.

[0107] The signal in the method may include a first signal, the predistortion parameter may include a first predistortion parameter, the predistorter circuit may include a first predistorter circuit, and the PA may include a first PA. The method may also include: wirelessly transmitting a second signal at a first frequency from a third communication chain of the MIMO transceiver, the third communication chain including a second predistorter circuit and a second PA, the second predistorter circuit being configured to accept a second predistortion parameter to predistort the signal before transmission, and the second PA being configured to amplify the signal of the third communication chain before transmission; receiving a combined signal including the first signal and the second signal at the first frequency at the second communication chain of the MIMO transceiver; isolating the first signal and the second signal from the combined signal; and calibrating the second predistortion parameter based on the second signal to compensate for nonlinearity of amplification provided by the second PA of the third communication chain.

[0108] The method may also include: buffering the signal at the baseband frequency to be transmitted by the first communication chain through the first communication chain; converting the signal to be transmitted by the first communication chain to the first frequency through the first communication chain; predistorting the signal at the first frequency to be transmitted by the first communication chain based on a predistortion parameter; and wirelessly transmitting the signal at the first frequency from the first communication chain of the MIMO transceiver.

[0109] The signal in the method may include a first signal, and in response to the calibration of the predistortion parameters, the method may also include: stopping wirelessly transmitting the first signal from the first communication chain of the MIMO transceiver; and starting wirelessly transmitting the second signal from the third communication chain of the MIMO transceiver. The predistortion parameters of the method may include a first predistortion parameter, the PA may include a first PA, the predistorter circuit may include a first predistorter circuit, and the third communication chain may include a second predistorter circuit and a second PA, the second predistorter circuit is configured to accept the second predistortion parameter to predistort the signal before transmission, and the second PA is configured to amplify the signal of the third communication chain before transmission. The method may also include: wirelessly receiving a second signal at a first frequency at the second communication chain of the MIMO transceiver; converting the second signal to a baseband frequency through the second communication chain; buffering the second signal at the baseband frequency through the second communication chain; and calibrating the second predistortion parameter based on the buffered second signal to compensate for the nonlinearity of the amplification provided by the second PA of the third communication chain.

[0110] The method may also include converting the signal at the baseband frequency to a digital signal.

[0111] The specific implementation described in the present disclosure can be realized using a computer-readable medium, which is used to carry or have a computer-executable instruction or data structure stored thereon. Such computer-readable media can be any available medium that can be accessed by a general or special-purpose computer. By way of example and not limitation, such computer-readable media may include a non-transient computer-readable storage medium, including a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage devices, a magnetic disk storage device or other magnetic storage devices, a flash memory device (e.g., a solid-state memory device), or any other storage medium that can be used to carry or store a desired program code in the form of a computer-executable instruction or data structure and can be accessed by a general or special-purpose computer. The above combination may also be included in the scope of a computer-readable medium.

[0112] Computer executable instructions may include, for example, instructions and data that cause a general purpose computer, a special purpose computer, or a special purpose processing device (e.g., one or more processors) to perform certain functions or groups of functions. Although the subject matter is described in language specific to structural features and / or method actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Instead, the specific features and actions described above are disclosed as exemplary forms of implementing the claims.

[0113] Unless the specific arrangements described herein are mutually exclusive, the various implementations described herein may be combined in whole or in part to enhance system functionality and / or produce complementary functions. Likewise, various aspects of a specific implementation may be implemented by independent arrangements. Therefore, the above description has been given by way of example only and may be modified in detail within the scope of the present invention.

[0114] As used in this disclosure, terms used in this disclosure, especially in the appended claims (e.g., the bodies of the appended claims), are generally intended to be “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “including but not limited to,” etc.).

[0115] Additionally, if a specific number of introduced claim statements is intended, such intent will be expressly stated in the claim, and in the absence of such statement, no such intent is present. For example, to aid understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim statements. However, the use of such phrases should not be construed as implying that the introduction of a claim statement by the indefinite article "a" or "an" will limit any particular claim containing such introduced claim statement to a specific implementation containing only one such statement. The same applies to the use of express articles used to introduce claim statements, even when the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "a kind" (e.g., "a" and / or "an" should be interpreted as meaning "at least one" or "one or more").

[0116] Furthermore, even if a specific number of an introduced claim expression is explicitly stated, one skilled in the art will recognize that such expression should be interpreted as meaning at least the stated number (e.g., a direct statement of "two expressions" without other modifiers means at least two expressions, or two or more expressions). Furthermore, where a convention similar to "at least one of A, B, and C, etc." or "one or more of A, B, and C, etc." is used, generally speaking, such constructions are intended to include A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together, etc.

[0117] In addition, any disjunctive word or phrase presenting two or more alternative terms, whether in the specification, claims or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both of the terms. For example, the phrase "A or B" should be understood to include the possibility of "A" or "B" or "A and B".

[0118] All examples and conditional language cited in this disclosure are intended for teaching purposes to help readers understand the disclosure and the concepts contributed by the inventors to advance the art, and should be understood as not being limited to such specifically cited examples and conditions. Although specific implementations of the disclosure have been described in detail, various changes, substitutions, and modifications may be made thereto without departing from the spirit and scope of the disclosure.

Claims

1. A multiple-input multiple-output MIMO transceiver configured for digital predistortion DPD calibration, the MIMO transceiver comprising: a first communication chain, the first communication chain being configured to wirelessly transmit a signal at a first frequency, the first communication chain comprising a predistorter circuit and a power amplifier PA, the predistorter circuit being configured to receive predistortion parameters to predistort the signal prior to transmission, the PA being configured to amplify the signal of the first communication chain prior to transmission; a second communication chain configured to wirelessly receive a signal at the first frequency, the second communication chain comprising: a converter circuit configured to convert the signal to a baseband frequency; and a buffer configured to buffer the signal at the baseband frequency; and A DPD circuit is configured to calibrate the predistortion parameters based on the buffered signal to compensate for non-linearity of amplification provided by the PA of the first communication chain.

2. The multiple-input multiple-output MIMO transceiver according to claim 1, wherein: The MIMO transceiver also includes a clear-to-send circuit configured to transmit a CTS-to-Self signal to other MIMO transceivers within an operating environment of the MIMO transceiver, the CTS-to-Self signal being reserved for a duration for the MIMO transceiver to perform DPD calibration using the first communication chain and the second communication chain.

3. The multiple-input multiple-output (MIMO) transceiver according to claim 1, wherein: The signal comprises a first signal, the converter circuit comprises a first converter circuit, the predistorter circuit comprises a first predistorter circuit, the PA comprises a first PA, the predistortion parameters comprise first predistortion parameters, and the buffer comprises a first buffer, and in response to calibration of the first predistortion parameters, the first communication chain is further configured to stop wirelessly transmitting the first signal, and the second communication chain is further configured to start wirelessly transmitting a second signal at the first frequency, and: The second communication chain comprises: a second predistorter circuit configured to accept second predistortion parameters to predistort the signal prior to transmission; and a second PA configured to amplify the signal of the second communication link prior to transmission; and The first communication chain is configured to wirelessly receive the second signal at the first frequency, the first communication chain comprising: a second converter circuit configured to convert the second signal to the baseband frequency; and A second buffer is configured to buffer the second signal at the baseband frequency, and the DPD circuit is further configured to calibrate the second predistortion parameters based on the buffered second signal to compensate for nonlinearity of amplification provided by the second PA of the second communication chain.

4. The multiple-input multiple-output (MIMO) transceiver according to claim 1, wherein: The signal comprises a first signal, the predistorter circuit comprises a first predistorter circuit, the PA comprises a first PA, and the MIMO transceiver further comprises a third communication chain, the third communication chain is configured to wirelessly transmit a second signal at the first frequency, the third communication chain comprises a second predistorter circuit and a second PA, the second predistorter circuit is configured to accept a second predistortion parameter to predistort the signal prior to transmission, and the second PA is configured to amplify the signal of the third communication chain prior to transmission, and the second communication chain is further configured to receive a combined signal comprising the first signal and the second signal at the first frequency, and the DPD circuit is further configured to: isolating the first signal and the second signal from the combined signal; and The second predistortion parameters are calibrated based on the second signal to compensate for non-linearity of amplification provided by the second PA of the third communication chain.

5. The multiple-input multiple-output MIMO transceiver according to claim 1, wherein: The signal includes a first signal, the MIMO transceiver further includes a third communication chain configured to wirelessly transmit a second signal at the first frequency, and in response to calibration of the predistortion parameters: The first communication link is configured to cease wirelessly transmitting the first signal; as well as The third communication link is configured to begin wirelessly transmitting the second signal.

6. The multiple-input multiple-output MIMO transceiver according to claim 5, wherein: The predistorter circuit includes a first predistorter circuit, the PA includes a first PA, the predistortion parameters include first predistortion parameters, and the third communication chain includes a second predistorter circuit and a second PA, the second predistorter circuit is configured to accept the second predistortion parameters to predistort the signal before transmission, and the second PA is configured to amplify the signal of the third communication chain before transmission, wherein: The second communication chain is further configured to wirelessly receive the second signal at the first frequency; The converter circuit is further configured to convert the second signal to the baseband frequency; The buffer is further configured to buffer the second signal at the baseband frequency; and The DPD circuit is further configured to calibrate the second predistortion parameters based on the buffered second signal to compensate for nonlinearity of amplification provided by the second PA of the third communication chain.

7. The multiple-input multiple-output (MIMO) transceiver according to claim 1, wherein: The buffer is a first buffer, and the converter circuit is a first converter circuit, and the first communication chain includes: a second buffer configured to buffer signals at the baseband frequency to be transmitted by the first communication link; and a second converter circuit configured to convert a signal to be transmitted by the first communication link to the first frequency, the predistorter circuit configured to predistort the signal at the first frequency based on the predistortion parameters, the first communication link configured to wirelessly transmit the signal at the first frequency.

8. The multiple-input multiple-output (MIMO) transceiver according to claim 1, wherein: The predistorter circuit uses the predistortion parameters to compensate for the nonlinearity of the amplification provided by the PA of the first communication chain by predistorting a signal transmitted by the first communication chain to be equal to an additive inverse of the nonlinearity of the amplification provided by the PA of the first communication chain.

9. The multiple-input multiple-output (MIMO) transceiver according to claim 1, wherein: The second communication chain is configured as a linear receive chain to avoid distortion of signals in the second communication chain.

10. A method of operating a multiple-input multiple-output (MIMO) transceiver, the MIMO transceiver being configured for digital predistortion (DPD) calibration, the method comprising: wirelessly transmitting a signal at a first frequency from a first communication chain of the MIMO transceiver, the first communication chain comprising a predistorter circuit configured to receive predistortion parameters to predistort the signal prior to transmission and a power amplifier PA configured to amplify the signal of the first communication chain prior to transmission; wirelessly receiving a signal at the first frequency at a second communication link of the MIMO transceiver; converting the signal to baseband frequency via the second communication link; buffering signals at the baseband frequency via the second communication chain; as well as The predistortion parameters are calibrated based on the buffered signal to compensate for non-linearity of amplification provided by the PA of the first communication chain.

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