WO2022099222A1

WO2022099222A1 - Multi-antenna calibration techniques

Info

Publication number: WO2022099222A1
Application number: PCT/US2021/059395
Authority: WO
Inventors: Aiguo Yan; Yi-Hsiu Wang
Original assignee: Zeku, Inc.
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-05-12

Abstract

Novel tools and techniques are provided multi-antenna calibration for transmit beamforming. A system includes an auxiliary wireless device comprising an auxiliary transceiver, and a primary wireless device coupled to the auxiliary wireless device, the primary wireless device including two or more transceivers. The primary wireless device may be configured to calibrate relative delay and phase differences between transmit chains of the two or more transceivers. The primary wireless device may further be configured to calibrate relative delay and phase differences between receive chains of the two or more transceivers.

Description

MULTI-ANTENNA CALIBRATION TECHNIQUES

COPYRIGHT STATEMENT

[0001] A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

FIELD

[0002] The present disclosure relates, in general, to methods, systems, and apparatuses for antenna calibration.

BACKGROUND

[0003] Conventional, transmit beamforming (TxBF) allows an access point to concentrate a wireless signal at the location of a client device. The 802.11 family of standards (including 802.11n/ac/ax) defines some methods of beamforming. This generally includes implicit and explicit TxBF techniques. Implicit TxBF typically requires fixed relative phases in the transmit (Tx) chains, and fixed relative phases in the receive (Rx) chains. The fixed relative phases are generally obtained by calibrations.

[0004] Schemes for over-the-air (OTA) calibration for antennas have increasingly been adopted. Typically, for OTA calibration, Tx chains and Rx chains are required to have zero relative time delay (on the magnitude of the sampling period). Moreover, for Wi-Fi applications, a zero intermediate frequency (IF) architectures are normally used for both Rx and Tx chains.

[0005] Methods, systems, and apparatuses for improved multi-antenna calibration techniques are provided.

SUMMARY

[0006] Novel tools and techniques for multi-antenna calibration are provided.

[0007] A method may include generating, at a primary device, a transmit test signal configured to calibrate transmit operation of the primary device, generating, at an auxiliary device, a receive test signal configured to calibrate receive operation of the primary device, and transmitting, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The method may further include obtaining, at the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals, calibrating a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrating a phase difference between two or more transmit chains of the primary device. The method may further include transmitting, via the auxiliary device, the receive test signal to the two or more transceivers, obtaining, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrating the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrating the phase difference between two or more receive chains of the primary device.

[0008] An apparatus may include a processor, and a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to perform various functions. The set of instructions may be executed by the processor to generate, at a primary device, a transmit test signal configured to calibrate transmit operation, and transmit, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The set of instructions may further include instructions executable by the processor to calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrate a phase difference between two or more transmit chains of the primary device. The set of instructions may further be executable by the processor to obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrate the phase difference between two or more receive chains of the primary device.

[0009] A system may include an auxiliary wireless device comprising an auxiliary transceiver, and a primary wireless device coupled to the auxiliary wireless device. The primary wireless device may further include two or more transceivers, a processor, and a non- transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to generate, at the primary device, a transmit test signal configured to calibrate transmit operation of the primary device, generate, at the auxiliary device, a receive test signal configured to calibrate receive operation of the primary device, and transmit, via the two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The instructions may further be executed by the processor to obtain, via the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals, calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrate a phase difference between two or more transmit chains of the primary device. The set of instructions may further be executed by the processor to transmit, via the auxiliary device, the receive test signal to the two or more transceivers, obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrate the phase difference between two or more receive chains of the primary device.

[0010] These illustrative embodiments are mentioned not to limit or define the disclosure, but to provide examples to aid understanding thereof. Additional embodiments are discussed in the Detailed Description, and further description is provided therein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A further understanding of the nature and advantages of particular embodiments may be realized by reference to the remaining portions of the specification and the drawings, in which like reference numerals are used to refer to similar components. In some instances, a sub-label is associated with a reference numeral to denote one of multiple similar components. When reference is made to a reference numeral without specification to an existing sub-label, it is intended to refer to all such multiple similar components.

[0012] Fig. 1A is a schematic diagram of a prior art arrangement for implicit TxBF, in accordance with various embodiments;

[0013] Fig. IB is a schematic diagram of a prior art arrangement for OTA calibration for implicit TxBF, in accordance with various embodiments;

[0014] Fig. 2 is a schematic diagram of a system for multi-antenna calibration for implicit TxBF in a connected arrangement, in accordance with various embodiments;

[0015] Fig. 3 is a schematic diagram of a system for OTA multi-antenna calibration for implicit TxBF without connected instrumentation, in accordance with various embodiments;

[0016] Fig. 4 is a schematic block diagram of a system implementing multi-antenna calibration for implicit TxBF, in accordance with various embodiments;

[0017] Fig. 5 is a flow diagram of a method for multi-antenna calibration for implicit TxBF, in accordance with various embodiments;

[0018] Fig. 6 is a schematic block diagram of a computer system for multi-antenna calibration for implicit TxBF, in accordance with various embodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0019] Various embodiments provide tools and techniques for multi-antenna calibration. In some embodiments, a method may include generating, at a primary device, a transmit test signal configured to calibrate transmit operation of the primary device, generating, at an auxiliary device, a receive test signal configured to calibrate receive operation of the primary device, and transmitting, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The method may further include obtaining, at the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals, calibrating a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrating a phase difference between two or more transmit chains of the primary device. The method may further include transmitting, via the auxiliary device, the receive test signal to the two or more transceivers, obtaining, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrating the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrating the phase difference between two or more receive chains of the primary device.

[0020] In some examples, calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers may be performed concurrently, and calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers may similarly be performed concurrently.

[0021] In further examples, calibrating the relative delay between two or more transmit chains of the primary device may include calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver. Calibrating the relative delay between the first transmit chain and second transmit chain may further include obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver, determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal, and adjusting the second transmit test signal by the delay difference. In some examples, calibrating the relative delay between two or more transmit chains may further include identifying a first delay difference between the first delay and the second delay when the first transceiver is connected to the auxiliary device via a first cable, and the second transceiver is connected to the auxiliary device via a second cable, and identifying a second delay difference between the first delay and the second delay when the first transceiver is connected to the auxiliary device via the second cable, and the second transceiver is connected to the auxiliary device via the first cable. Adjusting the second transmit test signal by the delay difference may further includes adjusting the second transmit test signal by an average delay difference, wherein the average delay difference is an average of the first delay difference and second delay difference. [0022] In yet further examples, calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver. Calibrating the relative delay between the first receive chain and second receive chain may further include measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver, measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver, and determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain. Thus, the timing (e.g., delay) of the second receive test signal may be adjusted by the delay difference.

[0023] In some examples, calibrating the phase difference between two or more transmit chains of the primary device may include calibrating the phase difference between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver. Thus, calibrating the phase difference between the first transmit chain and second transmit chain may further include obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver, and determining, via the auxiliary device, a phase difference between a first phase of a first complex gain of the first transmit test signal and a second phase of a second complex gain of the second transmit test signal. Thus, a phase of the second transmit test signal may be adjusted by the phase difference. In yet further examples, phase difference calibration may further include identifying a first phase difference between the first phase and the second phase when the first transceiver is connected to the auxiliary device via a first cable, and the second transceiver is connected to the auxiliary device via a second cable, and identifying a second phase difference between the first phase and the second phase when the first transceiver is connected to the auxiliary device via the second cable, and the second transceiver is connected to the auxiliary device via the first cable. Adjustment of the phase of the second transmit test signal by the phase difference may further include adjusting the second transmit test signal by an average phase difference, wherein the average phase difference is an average of the first phase difference and second phase difference. [0024] In yet further examples, calibrating the phase difference between two or more receive chains of the primary device includes calibrating the phase difference between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver. Thus, calibrating the phase difference between the first receive chain and second receive chain may further include measuring, via the primary device, a first phase of a first complex gain of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver, measuring, via the primary device, a second phase of a second complex gain of the second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver, and determining, via the primary device, a phase difference between the first phase of the first receive chain and the second phase of the second receive chain. The phase of the second receive test signal may then be adjusted by the phase difference.

[0025] In some embodiments, an apparatus for multi-antenna calibration is provided. The apparatus may include a processor, and a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to perform various functions. The set of instructions may be executed by the processor to generate, at a primary device, a transmit test signal configured to calibrate transmit operation, and transmit, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The set of instructions may further include instructions executable by the processor to calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrate a phase difference between two or more transmit chains of the primary device. The set of instructions may further be executable by the processor to obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrate the phase difference between two or more receive chains of the primary device. [0026] In some examples, calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers may be performed concurrently. In further examples, the set of instructions is may be executable by the processor to generate, at an auxiliary device, a receive test signal configured to calibrate receive operation of the primary device, obtaining, at the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals, and transmit, via the auxiliary device, the receive test signal to the two or more transceivers. In some examples, calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers may be performed concurrently. In some examples, the auxiliary device may be a transceiver of the two or more transceivers. Alternatively, the auxiliary device may be a signal generator. [0027] In further examples, calibrating the relative delay between two or more transmit chains of the primary device includes calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver. Calibrating the relative delay between the first transmit chain and second transmit chain may further include obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver, determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal, and adjusting the second transmit test signal by the delay difference.

[0028] In further examples, calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver. Calibrating the relative delay between the first receive chain and second receive chain may further include measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver, measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver, determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain, and adjusting timing of the second receive test signal by the delay difference.

[0029] In in further embodiments, a system for multi-antenna calibration is provided. The system may include an auxiliary wireless device comprising an auxiliary transceiver, and a primary wireless device coupled to the auxiliary wireless device. The primary wireless device may further include two or more transceivers, a processor, and a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to generate, at the primary device, a transmit test signal configured to calibrate transmit operation of the primary device, generate, at the auxiliary device, a receive test signal configured to calibrate receive operation of the primary device, and transmit, via the two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers. The instructions may further be executed by the processor to obtain, via the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals, calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers, and calibrate a phase difference between two or more transmit chains of the primary device. The set of instructions may further be executed by the processor to transmit, via the auxiliary device, the receive test signal to the two or more transceivers, obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers, calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers, and calibrate the phase difference between two or more receive chains of the primary device.

[0030] In some examples, calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers may be performed concurrently, and wherein calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers may be performed concurrently.

[0031] In some examples, calibrating the relative delay between two or more transmit chains of the primary device includes calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver. Calibrating the relative delay between the first transmit chain and second transmit chain may further include obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver, determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal, and adjusting the second transmit test signal by the delay difference.

[0032] In further examples, calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver. Calibrating the relative delay between the first receive chain and second receive chain may further include measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver, measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver, and determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain. The timing of the second receive test signal may be adjusted by the delay difference.

[0033] In the following description, for the purposes of explanation, numerous details are set forth to provide a thorough understanding of the described embodiments. It will be apparent to one skilled in the art, however, that other embodiments may be practiced without some of these details. In other instances, structures and devices are shown in block diagram form. Several embodiments are described herein, and while various features are ascribed to different embodiments, it should be appreciated that the features described with respect to one embodiment may be incorporated with other embodiments as well. By the same token, however, no single feature or features of any described embodiment should be considered essential to every embodiment of the invention, as other embodiments of the invention may omit such features. [0034] Unless otherwise indicated, all numbers used herein to express quantities, dimensions, and so forth used should be understood as being modified in all instances by the term "about." In this application, the use of the singular includes the plural unless specifically stated otherwise, and use of the terms "and" and "or" means "and/or" unless otherwise indicated. Moreover, the use of the term "including," as well as other forms, such as "includes" and "included," should be considered non-exclusive. Also, terms such as "element" or "component" encompass both elements and components comprising one unit and elements and components that comprise more than one unit, unless specifically stated otherwise. [0035] The various embodiments include, without limitation, methods, systems, apparatuses, and/or software products. Merely by way of example, a method might comprise one or more procedures, any or all of which may be executed by a computer system. Correspondingly, an embodiment might provide a computer system configured with instructions to perform one or more procedures in accordance with methods provided by various other embodiments. Similarly, a computer program might comprise a set of instructions that are executable by a computer system (and/or a processor therein) to perform such operations. In many cases, such software programs are encoded on physical, tangible, and/or non-transitory computer readable media (such as, to name but a few examples, optical media, magnetic media, and/or the like).

[0036] Various embodiments described herein, embodying software products and computer-performed methods, represent tangible, concrete improvements to existing technological areas, including, without limitation, antenna calibration. In some aspects, implementations of various embodiments improve antenna calibration for implicit TxBF. Conventional antenna calibration for implicit TxBF does not allow for calibration of the relative time delay between respective Tx and Rx chains. In some examples, the improved calibration scheme set forth below allows for the explicit calibration of the relative time delay between respective Tx and Rx chains. Moreover, in conventional OTA calibration, the Tx calibration signal (also referred to as a test signal) must be transmitted at high power, often leading to saturation of the Rx chain operating at high gain. In some examples, the improved OTA calibration scheme may avoid cases of both high Tx power and high Rx gain. Some technologies, such as Bluetooth, utilize different local oscillator (LO) frequencies for Tx and Rx chains, respectively. In these instances, conventional OTA calibration schemes can only approximate, instead of reproduce, normal Tx/Rx operating parameters. Moreover, it is difficult to provide on-demand and/or periodic OTA calibrations of consumer devices once they are in the hands of a consumer. [0037] To the extent any abstract concepts are present in the various embodiments, those concepts can be implemented as described herein by devices, software, systems, and methods that involve novel functionality (e.g., steps or operations), such as using an algorithm to quantization modes in a memory device and/or memory subsystem.

[0038] Fig. 1A is a schematic diagram is a schematic diagram of a prior art system 100A for implicit TxBF. The system 100A includes a primary device 105, first antenna 110, second antenna 115, secondary device 120, and device antenna 125. In various embodiments, the primary device 105 (e.g., beamformer) may be a wireless device configured to provide a shaped wireless signal (e.g., a beamformed signal) to the secondary device 120 (e.g., beamformee). Thus, the primary device 105 may be a wireless access point (AP), including routers, modems, and other gateway device, a cellular base station, or other wireless node. Thus, the primary device 105 may be any device under test (DUT). The primary device 105 thus includes two or more antennas. In the example illustrated, the primary device 105 is shown with first antenna 110 and second antenna 115. The first and second antennas 110 and 115 may be part of an antenna array of the primary device 105, and work in tandem to provide beamforming functionality (e.g., beam shaping) of a wireless signal transmitted to the secondary device 120.

[0039] The secondary device 120 may, thus, be a client device of the primary device 105. The secondary device 120 may include various user devices, such as a mobile device, mobile phone, tablet computer, laptop computer, desktop computer, a wearable smart device, or other suitable device with wireless communication capability. The secondary device 120 includes a single antenna, and in the example provided in Fig. 1A is the device antenna 125. [0040] Typically, beamforming is used to provide a higher fidelity signal, from the primary device 105 to the secondary device 120 (downstream). Implicit TxBF is a process that is "totally" under the control of the primary device 105, and no channel sounding is needed. During receiving time, the primary device 105 can estimate the air-propagation channels, which are normally modeled as complex numbers in the equivalent baseband (BB) models (e.g. unmodulated signal). During the transmission time, Tx signals of the primary device 105, such as signal emitted from the first antenna 110 and second antenna 115, are rotated in such a way that they will be constructively combined at the Rx antenna (e.g., the device antenna 125) of the secondary device 120.

The Tx signal can be characterized mathematically. The Tx signal, received at the device antenna 125 of the secondary device 120, is characterized by the following equation: (Eq. 1)

Where is the received signal at the secondary device 120, is the sent signal from

the first antenna 110,

is the channel characterization between the first antenna 110 and the device antenna 125, is the sent signal from the second antenna 115, is the

channel characterization between the second antenna 115 and the device antenna 125, and is additive noise.

[0041] With Tx beamforming, which needs knowledge of air-propagation channels, on the primary device side, the transmitted signal(s) can be characterized as: (Eq. 2) (Eq. 3) (Eq. 4)

[0042] The above equations implicitly assume that all Tx I Rx chains are matched. However, this is not the case in real-world conditions. Thus, calibrations are made to determine and compensate for phase mismatches.

For phase mismatches, at Rx time at the primary device 105, the phase difference between 2 channels (hl, h2) may be estimated as follows (with some common terms omitted). (Eq. 4)

Where h₁ and h₂ are complex numbers describing the BB equivalent air propagation channels, is the phase of the eq

uivalent BB air propagation channel described by

and is the

magnitude of the equivalent BB air propagation channel

is the phase of the equivalent BB air propagation channel described by h₂ and is the magnitude of the equivalent BB air propagation channel h₂, RX1 refers to the signal received by the first antenna, and RX2 refers to the signal received by the second antenna.

[0043] At Tx time, the received signals at the secondary device 120 must have the same phase. Thus, a phase calibration, is determined as follows. (Eq. 5)

(Eq. 6)

Where TX1 refers to signal transmitted from the first antenna 110, and TX2 refers to the signal transmitted from the second antenna 115.

[0044] Thus, where is a difference between the Rx phase

difference and Tx phase difference between two transceiver, and and

are obtained

from calibration and channel estimation, respectively. The following table sets forth the various parameters described above, and further described below.

Table 1: Phase anc Time Delay for OTA Calibration

[0045] Fig. IB is a schematic diagram of a system 100B is a schematic diagram of a prior art arrangement for OTA implicit TxBF. The system 100B includes primary device 105, first antenna 110, and second antenna 125. In the OTA arrangement, calibrations for TxBF are performed exclusively at the primary device.

[0046] The BB Tx Signal Models from the primary devices can be characterized by the following equations: (Eq. 8)

(Eq. 9)

Where s_p1(t) is signal transmitted by the first antenna 110,

is gain (e.g., a complex gain) at the transmit chain of the first antenna 110, is the unamplified signal in the

transmit chain of the first antenna 110 adjusted for a time delay introduced by the transmit chain of the first antenna 110, is signal transmitted by the second antenna 115, is

gain (e.g., complex gain) at the transmit chain of the second antenna 115, and is

the unamplified signal in the transmit chain of the second antenna 115 adjusted for the time delay introduced by the transmit chain of the second antenna 115. The BB Rx Signal Models at the primary devices can be characterized by the following equations. (Eq. 10) (Eq. 11)

[0047] Where r_pl(t) is the received signal by the receive chain of the first antenna 110, is gain (e.g., complex gain) of the receive chain of the first antenna 110, s_a(t — is the received signal from a secondary device 120 (or in the case of OTA calibration, a calibration signal from the other antenna) adjusted for a time delay introduced by the receive chain of the first antenna, r_p2 (t) is the received signal by the receive chain of the second antenna 115, is gain, (e.g., complex gain) of the receive chain of the second antenna 115,

and

is the unamplified signal in the receive chain of the second antenna 115 adjusted for a time delay of the receive chain of the second antenna 115.

[0048] The default assumption is that both phases and time delays are sensitive to process, temperature, frequency, and gain (RF/analog). Dependence on process I frequency I gain can be mitigated by calibration of each chip (and/or product) for each frequency, and each gain combination. Calibration may further be made at multiple temperature points during factory calibration, but this approach increases costs of production. Moreover, periodic calibration when the product is already in hands of an end user presents difficulty and risk.

[0049] Compared to symbol duration of a signal generated by the primary device 105, the delay caused by RF circuitry in the respective Tx chains of the first and second antenna 110, 115 is very small, and therefore can be modeled as a phase rotation. In contrast, the delay introduced by baseband circuitry could be significant. In some examples, by correlating the Rx waveform from Rx memory (e.g., data signal derived from the combined BB signal) with the Tx waveform (e.g., data signal before analog conversion) in the Tx memory, the delay may be determined. However, the delay in the BB circuitry does not inform the phase rotations introduced by the RF circuitry.

[0050] The phase difference between the Tx signal TX1 (transmitted from a first antenna 110) and Rx signal RX2 (received by a second antenna 115) is be given by: (Eq. 12)

Where is a phase shift of an air channel between the first and second antennas 110, 115. [0051] The phase difference between TX2 (transmitted by second antenna 115) and RX1 (received by first antenna 110) is be given by: (Eq. 13)

Thus, is given by: (Eq. 14)

[0052] In OTA calibration, everything for normal implicit TXBF is performed during calibration. However, OTA calibration is susceptible to signal saturation, with high Tx power and high Rx gain. Moreover, signal leakage must be controlled isolation of the Rx/Tx paths. Thus, a new approach to implicit TxBF calibration is set forth below.

[0053] Fig. 2 is a schematic diagram of a system 200 for multi-antenna calibration for implicit TxBF in a connected arrangement. The system 200 includes primary device 205, first antenna 210, second antenna 215, splitter and combiner 220, and test instrument 225. It should be noted that the various components of the system 200 are schematically illustrated in Fig. 2, and that modifications to the arrangement of the system 200 may be possible in accordance with the various embodiments.

[0054] In various embodiments, the splitter and combiner 220 may be configured to split and combine an analog signal (also called a divider). Thus, the splitter and combiner 220 may include a radio frequency (RF) signal splitter and combiner configured to split and combine signals from the primary device 205 and test instrument 225. That is, in splitter operation, a signal received at an input end (e.g., a single port side) is split into multiple outputs (e.g., a multiple port side), and in combiner operation, multiple signals received at an input end (e.g., the multiple port side) are combined to form a single signal at the output end (e.g., the single port side). The test instrument may, in some examples, include, without limitation, a signal generator, oscilloscope, and/or other test equipment suitable for generating test signals for transmission, and analyzing received signals.

[0055] In some embodiments, the splitter and combiner 220 may be coupled, at the multiple port side, to the outputs Al, A2 of the primary device 205. In some examples, the splitter and combiner 220 may be coupled to the first antenna 210 and second antenna 215. In the example shown, the output (Al) of the first antenna 210 may be coupled to a first port (Bl) of the splitter and combiner 220, and the output (A2) of the second antenna 215 may be coupled to a second port (B2) of the splitter and combiner 220. In some embodiments, the splitter and combiner 220 may be coupled to the first and second antennas 210, 215 at a point between the respective antenna and the last RF amplifier in the respective transmit chains of the antennas. Therefore, the transmit signal may be obtained by the splitter and combiner 220 at a point before the signal reaches the first and second antennas 210, 215, and after the signals to the first and second antennas 210, 215 have passed through the respective transmit chains (e.g., after the signals have been amplified). This point is referred to as the output of the antenna (referred to as Al and A2, respectively). In further embodiments, the output Al of the first antenna 210 may further be coupled to the second port B2 of the splitter and combiner 220, and output A2 of the second antenna 215 may further be coupled first port Bl. The single port side of the splitter and combiner 220 may be coupled to the test instrument 225. When calibrating using a test instruments, calibration does not include phase variations introduced by the antennas in the calibration loop. Thus, phase variations due to antennas may be kept within an acceptable range.

[0056] Accordingly, signals from the outputs Al, A2 of the primary device 205 of the first and second antennas 210, 215 received by the splitter and combiner 220 may be combined to produce a combined BB signal, which may be provided to the test instrument 225. In the other direction, signals from the test instrument 225 may be received by the splitter and combiner 220 to produce a split output at the first port Bl and second port B2, to be provided to outputs Al, A2 of the primary device 205.

[0057] In various embodiments, by using the system 200, allows for calibration of timing differences (also referred to as relative delay calibration) between the Tx and Rx chains of the respective antennas, in addition to phase differences. To calibrate Tx timing differences, the primary device 205 may be configured to transmit two orthogonal signals, s₁(t) and s₂(t). The combined signal received at the test instrument may be given by: (Eq. 15)

[0058] Thus, the correlation can be easily used to find a difference between the two delays (also referred interchangeably as delay difference and/or timing difference), where

[0059] In further embodiments, delays introduced by the connecting cables, and splitter and combiner 220 may further be calibrated to mitigate timing error introduced by the cables and/or the splitter and combiner 220. For example, in some embodiments, calibration for delays introduced by cables and/or the splitter and combiner 220 may include connecting Bl to Al, and B2 to A2. A first timing difference, A_1; across the respective signal paths may be measured at the test instrument 225, and thus given by: (Eq. 16)

[0060] Subsequently, Bl may be connected to A2, and B2 connected to Al. Again, a second timing difference, across the signal paths may be measured, and is given by:

(Eq. 17)

[0061] Thus,

may be solved as follows:

2 (Eq. 18)

[0062] To calibrate timing differences in the receive chain, the test instrument may generate a test signal, s(t). The test signal as received at the primary device 205 (at Al and A2) are provided, respectively, by: (Eq. 19)

and (Eq. 20)

[0063] As described above with respect to Tx relative delay, may be determined

based on the measured received test signals

where

[0064] As described above with respect to the Tx timing difference calibration procedure, the cable swapping process, in which Bl is coupled to Al and B2 to A2 to determine a first timing difference, and subsequently Bl is coupled to A2, and B2 to Al to determine a second timing difference, and giving the following relationships:

(Eq. 21)

(Eq. 22)

[0065] In further embodiments, system 200 may further be configured to calibrate the phase differences (e.g., introduced by the RF chains excluding the first and second antennas 210, 215). Once timing differences have been calibrated as outlined above, in Tx operation, a signal received at the test instrument may be given by:

[0066] In Rx operation, a test signal, generated by the testing instrument 225, and received by the primary device 205 (e.g., at Al, A2) may be given by:

[0067] Correlation methods may thus be used to determine the complex gains, grxi>

and specifically the respective phases of the complex gains.

[0068] As in the calibration for timing differences, if cables introduce different phases, a similar cable swapping process may be used to mitigate the impact of different phases from cables. In a further embodiment, the reciprocity of the cable connections may be used to calibrate for phase differences introduced by the cables. For example, in some embodiments, phase differences introduced by the cables may be determined as follows:

[0070] Alternatively, the phase differences may further be determined when cables are switched

and an average used, as in the example of relative delay

calibration.

[0071] In some embodiments, timing and phase calibrations maybe combined to be performed concurrently over a single sequence of signals between the primary device 205 and test instrument 225.

[0072] Periodic calibration, however, is difficult in the test instrumentation arrangement of system 200, as a primary device 205 may not be accessible after an initial calibration has been performed and/or the primary device 205 has been deployed I released to a user. Conventional OTA calibration is possible, but unreliable given unpredictable environmental conditions of a device, such as interference, negatively affecting calibration results. Thus, long term stability of the phase/timing different may be maintained through RF/analog design. Alternatively, an OTA calibration scheme as set forth below, with respect to FIG. 3, may be utilized.

[0073] In various embodiments, the calibration procedure above may be extended to more than two antennas. For an N-number of antennas, where N is an integer, during Rx operation, N-number of measurements may be made:

where is the phase of equivalent BB air-propagation channel (described by a

complex number h_N) between the N-th antenna and an aux transceiver antenna (e.g., of the test instrument 225 or third antenna 330 as will be described below with respect to Fig. 3). [0074] During Tx, signals on all other antennas may be rotated, with the signal at the first antenna 210 acting as a reference (e.g., = 0), such that the received signal at an

auxiliary device’s antenna (e.g., test instrument 225) are constructively combined. Thus, the following measurements may be made: where

is the phase of equivalent BB air-propagation channel (described by a complex number h_w) between the N-th antenna and an aux transceiver.

[0075] From the above, the calibration may be derived as: (Eq. 30) (Eq. 31) (Eq- 32)

Where may be measured during Rx operation, and is determined from calibrations,

for i = 1, 2, . . . , N. For AOA, the phase and timing differences among Rx chains should be determined, and for AOD, the phase and timing differences among Tx chains should be determined, as described above. The time delay for each respective Tx and Rx chains may also be determined for calibration.

[0076] In further embodiments, the calibration procedures above may be extended to calibration of both zero-intermediate frequency (ZIF) (e.g., direct-conversion) and/or non- zero IF (e.g., low IF or LIF) architectures. In time division duplexing (TDD) systems, such as Bluetooth, a direct up-converter is used for Tx, whereas a low-IF down-converter is used for Rx. For Tx I Rx at the same RF frequency channel, Tx I Rx utilizes a common LO, but at different LO frequencies.

[0077] Both connected calibration with a test instrument, as in system 200, and OTA calibration (as set forth in greater detail below with respect to FIG. 3) may be performed on such architectures. The gains g have dependence on both LO frequency (ω_LO), and carrier frequency (alternatively , and gain is denoted as

[0078] When LO frequency is equal to carrier frequency, the waveform stored in memory (e.g., the test signal) is x(t) = s(t). The transmitted RF signal may be given as: (Eq. 33)

[0079] The combined BB signal, after the low-IF down-converter, may be given as: (Eq. 34)

[0080] The signal in Rx memory (e.g., data signal from the combined BB signal) is given by: (Eq. 35)

[0081] This yields the following correlation:

[0082] With: (Eq. 37)

And (Eq. 37)

[0083] In further embodiments, when different carrier frequencies (RF frequencies) are used, the LO frequency is equal to LO = . The waveform in Tx memory may be given as: (Eq. 38)

[0084] The transmitted RF signal may be given as:

(Eq. 39)

[0085] The received BB signal after down-converter may be given as: - (Eq. 40)

[0086] And the signal in the Rx memory given as: (Eq. 41)

[0087] This yields the following correlation:

[0088] With: (Eq. 43)

And (Eq. 44)

[0089] In normal operation, - - -

may be used. Therefore, the following condition —

may be enforced.

[0090] Fig. 3 is a schematic diagram of a system 300 for OTA multi-antenna calibration for implicit TxBF without connected instrumentation. The system 300 includes a first transceiver 305, second transceiver 315, and third transceiver 325. The first transceiver 305 may include first antenna 310, the second transceiver 315 may include second antenna 320, and third transceiver 325 may include third antenna 330. It should be noted that the various components of the system 300 are schematically illustrated in Fig. 3, and that modifications to the arrangement of the system 300 may be possible in accordance with the various embodiments.

[0091] In various embodiments, the system 300 may be implemented in a single chipset with the three or more transceivers 305, 315, 325, or as one or more chipsets with one or more respective transceivers. It is to be understood that system 300 is not limited to three transceivers, and is only depicted with three transceivers for purposes of explanation. In other embodiments, the system 300 may include an N-number of additional transceivers.

[0092] As previously described, periodic calibration for TxBF can mitigate varying parameters, such as time and temperature, but is prone to interference from the environment. The following OTA calibration scheme provides a way to implement OTA calibration for TxBF.

[0093] In various embodiments, the first transceiver 305 and second transceiver 315 may operate normally as transceivers of a primary device, such as primary device 105, 205. The third transceiver 325, however, may be used as an auxiliary transceiver for on-board TxBF calibration. Thus, the auxiliary transceiver may be analogous to the test instrument and combiner/splitter of FIG. 2 above, but in an OTA arrangement. With the aux transceiver and precisely placed antenna (e.g., third antenna 330), the connected test instrument-based calibration of FIG. 2 may be adapted for periodic OTA calibration.

[0094] At the scale of the sampling time for purposes of the relative delay calibration between Tx and Rx chains (e.g., calibration for timing differences) may eb considered insensitive to the signal path differences between air-channell and air-channel2. For implicit TxBF calibration with two antennas (first antenna 310, second antenna 320), the difference between air-channell (h_al) and air-channel2 (h_a2) may be ignored. Based on the above assumption, the following may be established: (Eq. 45)

(Eq. 46)

[0095] Thus, for implicit TxBF, the following may be established: (Eq. 47)

[0096] For AO A, AOD, and radar applications, in which more accurate and

may be needed, the above relationship may be established, for example, through

RF/analog design to make

[0097] For cases of more than 2 antennas, and ,may be determined

for i = 1, 2, . . . , N, where: (Eq. 48) (Eq. 50) (Eq. 51)

[0098] As previously described, calibration may be performed with multiple Tx or Rx channels simultaneously, enabling a significant reduction in calibration time. In addition, simultaneously calibrating for Tx or Rx chains is much closer to normal operation of the device.

[0099] Thus, according to various embodiments, in Rx operation, the auxiliary transceiver (third transceiver 325) may be configured to transmit a test signal, via the third antenna 330, to the normal transceivers, for example, the first transceiver 305 and second transceiver 315. The signals may be obtained via the first antenna 310 and second antenna 320, respectively. In Tx operation, the auxiliary transceiver 325 may be configured to receive respective orthogonal test signals from the normal transceivers 305, 315. Thus, timing and phase differences may be calibrated (e.g., relative delay calibration, phase calibration) as set forth above with respect to Eqs. 15-29. In further embodiments, calibration with OTA arrangement of system 300 may further be extended to multiple antennas and LIF architectures as described above.

[0100] Fig. 4 is a schematic block diagram of a system 400 implementing multiantenna calibration for implicit TxBF. The system 400 includes primary device 405, which further includes one or more transceivers (e.g., 1 through N-number of transceivers) having respective Tx chains and Rx chains. The Tx chain of the first transceiver may include TxRF circuitry 410a, Tx analog circuitry 415a, digital to analog converter (DAC) 420a, and Tx memory 425 a. The Rx chain of the first transceiver may include RxRF circuitry 430a, Rx analog circuitry 435a, analog to digital converter (ADC) 440a, and Rx memory 445a. The Tx and Rx chains may be coupled to a respective first antenna 450a. An N-th transceiver of the primary device 405 may include an N-th Tx chain and N-th Rx chain. The N-th Tx chain may include TxRF circuitry 410n, Tx analog circuitry 415n, DAC 420n, and Tx memory 425n. The N-th Rx chain may include RxRF circuitry 430n, Rx analog circuitry 435n, ADC 440n, and Rx memory 445n. The N-th Tx and Rx chains may be coupled to a respective N-th antenna 450n. Each of the N-number of transceivers may further be coupled to a signal processor or other processing logic (not shown). Common elements, such as an EO, are further omitted for simplification of the diagram. It should be noted that the various components of the system 400 are schematically illustrated in Fig. 4, and that modifications to the arrangement of the system 400 may be possible in accordance with the various embodiments. [0101] In various examples, as set forth above, respective baseband circuitry for a respective Tx I Rx chain may include one or more of the Tx analog circuitry 415a-415n and DAC 420a-420n for a Tx chain, and Rx analog circuitry 435a-435n and ADC 440a-440n for the Rx chain. Reference to RF circuitry in the above examples may refer to respective TxRF circuitry 410a-410n and RxRF circuitry 430a-430n. RF circuitry may include circuitry required for modulation of the baseband signal from analog circuitry 415a-415n, 435a-435n, and may include, without limitation, an LO, amplifier section, mixers, and other elements. [0102] Fig. 5 is a flow diagram of a method for multi-antenna calibration for implicit TxBF, in accordance with various embodiments. The method 500 begins, at block 505, by generating a test signal for Tx and Rx operation. For Tx operation, the test signals may be stored in Tx memory of the primary device. For Rx operation, the test signal may be stored in Tx memory of an auxiliary device. The auxiliary device may include, for example, an auxiliary transceiver of a primary device in an OTA calibration arrangement, or a test instrument in a connected arrangement for calibration. In some examples, the test signal may be a special waveform. For example, in Tx operation, the test signal may include a signal, such as a code division multiple access (CDMA) signal, with good auto/cross-correlation properties.

[0103] At block 510, a respective transmit test signal is transmitted, in Tx operation, to the auxiliary device, by each of the two or more transceivers of the primary device. In various embodiments, the auxiliary device may be configured to receive a combined test signal, which combines each of the respective transmit test signals. Thus, in some embodiments, the test signal from each of the two or more transceivers may be rotated in such a way that they will be constructively combined at the auxiliary device.

[0104] The method 500 continues, at block 515, by calibrating for relative delay between the respective transmit chains of the primary device. In various embodiments, relative delay may be determined based on a correlation between the transmit test signals may be used to find the delays of each respective chain. For example, the transmit test signals may include two orthogonal signals. Thus, the transmit test signal, as received at the auxiliary device, should be given by Eq. 15, as set forth above. Relative delays between the respective transmit chains may then be determined. In further embodiments, timing errors and delays introduced by connecting cables and/or intervening equipment may be mitigated as set forth in Eqs. 16- 18.

[0105] The method further includes, at block 520, calibrating for phase differences between the respective transmit chains. As previously described, phase difference calibration may be performed concurrently with the relative delay calibration. In some embodiments, once timing delay has been calibrated, a phase calibration may be determined based on phase differences in the delay calibrated transmit test signals. This may, in turn, be determined based on a measured phase difference between transmitted test signals as derived from the combined transmit test signal, and further an estimated phase difference from a channel estimation between the auxiliary device and each respective transceiver of the primary device. This is set forth in further detail with respect to Eqs. 24-29.

[0106] At block 525, the method 500 continues by transmitting a receive test signal via the auxiliary device to the two or more transceivers. In various embodiments, the auxiliary device may generate a receive test signal to be transmitted for calibration of Rx operation of the primary device. The received test signals at each of the two or more transceivers may then be used for calibration. In one example, the received test signals are set forth above with respect to Eqs. 19-20.

[0107] Thus, the method 500 further include, at block 530, calibrating relative delay between receive chains. In various embodiments, a first received test signal at the first transceiver and second received test signal at the second transceiver may be used to determine the relative delay. In some embodiments, the relative delay may be determined based on the measured first received test signal and second received test signal.

[0108] At block 535, the method 500 may further include calibrating phase differences between the receive chains. In Rx operation, a correlation may be used to determine respective phases of the complex gains of the respective received test signals to determine a phase difference between the received test signals.

[0109] As previously described, relative delay calibration and phase calibration may be expanded to include calibration for more than two antennas, and calibration in LIF architectures.

[0110] The process of calibration of implicit TxBF may be performed by computer system. Fig. 6 is a schematic block diagram of a computer system 600 for multi-antenna calibration for implicit TxBF, in accordance with various embodiments. Fig. 6 provides a schematic illustration of one embodiment of a computer system 600, such as the systems 200, 300, 400 or subsystems thereof, such as the primary device, test instrument, transceivers, signal processors, and the like, which may perform the methods provided by various other embodiments, as described herein. It should be noted that Fig. 6 only provides a generalized illustration of various components, of which one or more of each may be utilized as appropriate. Fig. 6, therefore, broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner.

[0111] The computer system 600 includes multiple hardware elements that may be electrically coupled via a bus 605 (or may otherwise be in communication, as appropriate). The hardware elements may include one or more processors 610, including, without limitation, one or more general-purpose processors and/or one or more special-purpose processors (such as microprocessors, digital signal processing chips, graphics acceleration processors, and microcontrollers); one or more input devices 615, which include, without limitation, a mouse, a keyboard, one or more sensors, and/or the like; and one or more output devices 620, which can include, without limitation, a display device, and/or the like.

[0112] The computer system 600 may further include (and/or be in communication with) one or more storage devices 625, which can comprise, without limitation, local and/or network accessible storage, and/or can include, without limitation, a disk drive, a drive array, an optical storage device, solid-state storage device such as a random-access memory ("RAM") and/or a read-only memory ("ROM"), which can be programmable, flash- updateable, and/or the like. Such storage devices may be configured to implement any appropriate data stores, including, without limitation, various file systems, database structures, and/or the like.

[0113] The computer system 600 might also include a communications subsystem 630, which may include, without limitation, a modem, a network card (wireless or wired), an IR communication device, a wireless communication device and/or chipset (such as a Bluetooth™ device, an 802.11 device, a WiFi device, a WiMax device, a WWAN device, a Z-Wave device, a ZigBee device, cellular communication facilities, etc.), and/or a LP wireless device. The communications subsystem 630 may permit data to be exchanged with a network (such as the network described below, to name one example), with other computer or hardware systems, between data centers or different cloud platforms, and/or with any other devices described herein. In many embodiments, the computer system 600 further comprises a working memory 635, which can include a RAM or ROM device, as described above.

[0114] The computer system 600 also may comprise software elements, shown as being currently located within the working memory 635, including an operating system 640, device drivers, executable libraries, and/or other code, such as one or more application programs 645, which may comprise computer programs provided by various embodiments, and/or may be designed to implement methods, and/or configure systems, provided by other embodiments, as described herein. Merely by way of example, one or more procedures described with respect to the method(s) discussed above might be implemented as code and/or instructions executable by a computer (and/or a processor within a computer); in an aspect, then, such code and/or instructions can be used to configure and/or adapt a general purpose computer (or other device) to perform one or more operations in accordance with the described methods.

[0115] A set of these instructions and/or code might be encoded and/or stored on a non-transitory computer readable storage medium, such as the storage device(s) 625 described above. In some cases, the storage medium might be incorporated within a computer system, such as the system 600. In other embodiments, the storage medium might be separate from a computer system (i.e., a removable medium, such as a compact disc, etc.), and/or provided in an installation package, such that the storage medium can be used to program, configure, and/or adapt a general purpose computer with the instructions/code stored thereon. These instructions might take the form of executable code, which is executable by the computer system 600 and/or might take the form of source and/or installable code, which, upon compilation and/or installation on the computer system 600 (e.g., using any of a variety of generally available compilers, installation programs, compression/decompression utilities, etc.) then takes the form of executable code.

[0116] It will be apparent to those skilled in the art that substantial variations may be made in accordance with specific requirements. For example, customized hardware (such as programmable logic controllers, single board computers, FPGAs, ASICs, and SoCs) might also be used, and/or particular elements might be implemented in hardware, software (including portable software, such as applets, etc.), or both. Further, connection to other computing devices such as network input/output devices may be employed.

[0117] As mentioned above, in one aspect, some embodiments may employ a computer or hardware system (such as the computer system 600) to perform methods in accordance with various embodiments of the invention. According to a set of embodiments, some or all of the procedures of such methods are performed by the computer system 600 in response to processor 610 executing one or more sequences of one or more instructions (which might be incorporated into the operating system 640 and/or other code, such as an application program 645) contained in the working memory 635. Such instructions may be read into the working memory 635 from another computer readable medium, such as one or more of the storage device(s) 625. Merely by way of example, execution of the sequences of instructions contained in the working memory 635 might cause the processor(s) 610 to perform one or more procedures of the methods described herein. [0118] The terms "machine readable medium" and "computer readable medium," as used herein, refer to any medium that participates in providing data that causes a machine to operate in a specific fashion. In an embodiment implemented using the computer system 600, various computer readable media might be involved in providing instructions/code to processor(s) 610 for execution and/or might be used to store and/or carry such instructions/code (e.g., as signals). In many implementations, a computer readable medium is a non-transitory, physical, and/or tangible storage medium. In some embodiments, a computer readable medium may take many forms, including, but not limited to, non-volatile media, volatile media, or the like. Non-volatile media includes, for example, optical and/or magnetic disks, such as the storage device(s) 625. Volatile media includes, without limitation, dynamic memory, such as the working memory 635. In some alternative embodiments, a computer readable medium may take the form of transmission media, which includes, without limitation, coaxial cables, copper wire and fiber optics, including the wires that comprise the bus 605, as well as the various components of the communication subsystem 630 (and/or the media by which the communications subsystem 630 provides communication with other devices). In an alternative set of embodiments, transmission media can also take the form of waves (including, without limitation, radio, acoustic, and/or light waves, such as those generated during radio-wave and infra-red data communications).

[0119] Common forms of physical and/or tangible computer readable media include, for example, a floppy disk, a flexible disk, a hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read instructions and/or code.

[0120] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to the processor(s) 610 for execution. Merely by way of example, the instructions may initially be carried on a magnetic disk and/or optical disc of a remote computer. A remote computer might load the instructions into its dynamic memory and send the instructions as signals over a transmission medium to be received and/or executed by the computer system 600. These signals, which might be in the form of electromagnetic signals, acoustic signals, optical signals, and/or the like, are all examples of carrier waves on which instructions can be encoded, in accordance with various embodiments of the invention. [0121] The communications subsystem 630 (and/or components thereof) generally receives the signals, and the bus 605 then might carry the signals (and/or the data, instructions, etc. carried by the signals) to the working memory 635, from which the processor(s) 610 retrieves and executes the instructions. The instructions received by the working memory 635 may optionally be stored on a storage device 625 either before or after execution by the processor(s) 610.

[0122] While some features and aspects have been described with respect to the embodiments, one skilled in the art will recognize that numerous modifications are possible. For example, the methods and processes described herein may be implemented using hardware components, software components, and/or any combination thereof. Further, while various methods and processes described herein may be described with respect to particular structural and/or functional components for ease of description, methods provided by various embodiments are not limited to any particular structural and/or functional architecture but instead can be implemented on any suitable hardware, firmware and/or software configuration. Similarly, while some functionality is ascribed to one or more system components, unless the context dictates otherwise, this functionality can be distributed among various other system components in accordance with the several embodiments.

[0123] Moreover, while the procedures of the methods and processes described herein are described in a particular order for ease of description, unless the context dictates otherwise, various procedures may be reordered, added, and/or omitted in accordance with various embodiments. Moreover, the procedures described with respect to one method or process may be incorporated within other described methods or processes; likewise, system components described according to a particular structural architecture and/or with respect to one system may be organized in alternative structural architectures and/or incorporated within other described systems. Hence, while various embodiments are described with or without some features for ease of description and to illustrate aspects of those embodiments, the various components and/or features described herein with respect to a particular embodiment can be substituted, added and/or subtracted from among other described embodiments, unless the context dictates otherwise. Consequently, although several embodiments are described above, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising: generating, at a primary device, a transmit test signal configured to calibrate transmit operation of the primary device; generating, at an auxiliary device, a receive test signal configured to calibrate receive operation of the primary device; transmitting, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers; obtaining, at the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals; calibrating a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers; calibrating a phase difference between two or more transmit chains of the primary device; transmitting, via the auxiliary device, the receive test signal to the two or more transceivers; obtaining, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers; calibrating the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers; and calibrating the phase difference between two or more receive chains of the primary device.

2. The method of claim 1, wherein calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers is performed concurrently, and wherein calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers is performed concurrently.

3. The method of claim 1, wherein calibrating the relative delay between two or more transmit chains of the primary device includes calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver, wherein calibrating the relative delay between the first transmit chain and second transmit chain further comprises: obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver; determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal; and adjusting the second transmit test signal by the delay difference.

4. The method of claim 3, further comprising: identifying a first delay difference between the first delay and the second delay when the first transceiver is connected to the auxiliary device via a first cable, and the second transceiver is connected to the auxiliary device via a second cable; identifying a second delay difference between the first delay and the second delay when the first transceiver is connected to the auxiliary device via the second cable, and the second transceiver is connected to the auxiliary device via the first cable; and wherein adjusting the second transmit test signal by the delay difference further includes adjusting the second transmit test signal by an average delay difference, wherein the average delay difference is an average of the first delay difference and second delay difference.

5. The method of claim 1, wherein calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver, wherein calibrating the relative delay between the first receive chain and second receive chain further comprises: measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver; measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver; determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain; and adjusting timing of the second receive test signal by the delay difference.

6. The method of claim 1, wherein calibrating the phase difference between two or more transmit chains of the primary device includes calibrating the phase difference between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver, wherein calibrating the phase difference between the first transmit chain and second transmit chain further comprises: obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver; determining, via the auxiliary device, a phase difference between a first phase of a first complex gain of the first transmit test signal and a second phase of a second complex gain of the second transmit test signal; and adjusting a phase of the second transmit test signal by the phase difference.

7. The method of claim 6, further comprising: identifying a first phase difference between the first phase and the second phase when the first transceiver is connected to the auxiliary device via a first cable, and the second transceiver is connected to the auxiliary device via a second cable; identifying a second phase difference between the first phase and the second phase when the first transceiver is connected to the auxiliary device via the second cable, and the second transceiver is connected to the auxiliary device via the first cable; and wherein adjusting the phase of the second transmit test signal by the phase difference further includes adjusting the second transmit test signal by an average phase difference, wherein the average phase difference is an average of the first phase difference and second phase difference.

8. The method of claim 1, wherein calibrating the phase difference between two or more receive chains of the primary device includes calibrating the phase difference between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver, wherein calibrating the phase difference between the first receive chain and second receive chain further comprises: measuring, via the primary device, a first phase of a first complex gain of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver; measuring, via the primary device, a second phase of a second complex gain of the second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver; determining, via the primary device, a phase difference between the first phase of the first receive chain and the second phase of the second receive chain; and adjusting the phase of the second receive test signal by the phase difference.

9. An apparatus, comprising: a processor; and a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to: generate, at a primary device, a transmit test signal configured to calibrate transmit operation; transmit, via two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers; calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers; calibrate a phase difference between two or more transmit chains of the primary device; obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers; calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers; and calibrate the phase difference between two or more receive chains of the primary device.

10. The apparatus of claim 9, wherein calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers is performed concurrently.

11. The apparatus of claim 9, wherein the set of instructions is further executable by the processor to: generate, at an auxiliary device, a receive test signal configured to calibrate receive operation of the primary device; obtain, at the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals; and transmit, via the auxiliary device, the receive test signal to the two or more transceivers;

12. The apparatus of claim 11, wherein calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers is performed concurrently.

13. The apparatus of claim 11, wherein the auxiliary device is a transceiver of the two or more transceivers.

14. The apparatus of claim 9, wherein the auxiliary device is a signal generator.

15. The apparatus of claim 9, wherein calibrating the relative delay between two or more transmit chains of the primary device includes calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver, wherein calibrating the relative delay between the first transmit chain and second transmit chain further comprises: obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver; determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal; and adjusting the second transmit test signal by the delay difference.

16. The apparatus of claim 9, wherein calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver, wherein calibrating the relative delay between the first receive chain and second receive chain further comprises: measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver; measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver; determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain; and adjusting timing of the second receive test signal by the delay difference. A system for multi-antenna calibration, the system comprising: an auxiliary wireless device comprising an auxiliary transceiver; a primary wireless device coupled to the auxiliary wireless device, the primary wireless device comprising: two or more transceivers; a processor; and a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium having encoded thereon a set of instructions executable by the processor to: generate, at the primary device, a transmit test signal configured to calibrate transmit operation of the primary device; generate, at the auxiliary device, a receive test signal configured to calibrate receive operation of the primary device; transmit, via the two or more transceivers, the transmit test signal to the auxiliary device, wherein the transmit test signal, as transmitted by each transceiver of the two or more transceivers, is a respective transmit test signal of the respective transceiver of the two or more transceivers; obtain, via the auxiliary device, a combined transmit test signal from each of the two or more transceivers, the combined transmit test signal comprising each of the respective transmit test signals; calibrate a relative delay between two or more transmit chains of the primary device, each of the two or more transmit chains associated with a respective transceiver of the two or more transceivers; calibrate a phase difference between two or more transmit chains of the primary device; transmit, via the auxiliary device, the receive test signal to the two or more transceivers; obtain, via the two or more transceivers, the receive test signal from the auxiliary device, wherein the receive test signal, as received by each transceiver of the two or more transceivers, is a respective receive test signal of the respective transceiver of the two or more transceivers; calibrate the relative delay between two or more receive chains of the primary device, each of the two or more receive chains associated with a respective transceiver of the two or more transceivers; and calibrate the phase difference between two or more receive chains of the primary device.

18. The system of claim 17, wherein calibrating the relative delay and phase difference between the two or more transmit chains of the two or more transceivers is performed concurrently, and wherein calibrating the relative delay and phase difference between the two or more receive chains of the two or more transceivers is performed concurrently.

19. The system of claim 17, wherein calibrating the relative delay between two or more transmit chains of the primary device includes calibrating the relative delay between a first transmit chain associated with a first transceiver and a second transmit chain associated with a second transceiver, wherein calibrating the relative delay between the first transmit chain and second transmit chain further comprises: obtaining, via the auxiliary device, a first transmit test signal and second transmit test signal from the combined transmit test signal, based on a correlation between the first transmit test signal and second transmit test signal, wherein the first transmit test signal is the transmit test signal transmitted by the first transceiver and the second transmit test signal is the transmit test signal transmitted by the second transceiver; determining, via the auxiliary device, a delay difference between a first delay of the first transmit chain and a second delay of the second transmit chain based on a correlation between the first transmit test signal and second transmit test signal; and adjusting the second transmit test signal by the delay difference.

20. The system of claim 17, wherein calibrating the relative delay between two or more receive chains of the primary device includes calibrating the relative delay between a first receive chain associated with a first transceiver and a second receive chain associated with a second transceiver, wherein calibrating the relative delay between the first receive chain and second receive chain further comprises: measuring, via the primary device, a first delay of the first receive chain from a first receive test signal, wherein the first receive test signal is the receive test signal received by the first transceiver; measuring, via the primary device, a second delay of a second receive chain from a second receive test signal, wherein the second receive test signal is the receive test signal received by the second transceiver; determining, via the primary device, a delay difference between the first delay of the first receive chain and the second delay of the second receive chain; and adjusting timing of the second receive test signal by the delay difference.