On-chip calibration of channel-to-channel phase variation for beamforming integrated circuits

Abstract

Apparatuses and methods are provided for calibrating transmit and receive channels of an array antenna using a calibration stimulus and a measurement path referenced to a common local oscillator (L0) signal. A transmit calibration signal generated using the L0 signal is applied to one or more transmit channels. A coupler samples a transmit-channel signal after traversal of a phase shifter, and mixer circuitry downconverts the sampled signal by mixing with the L0 signal to produce a calibration measurement signal. An upconverted test signal generated using the L0 signal is injected via a coupler into one or more receive channels such that the signal traverses a phase shifter, and mixer circuitry downconverts a receive-channel signal by mixing with the L0 signal to produce a receive calibration measurement signal. By stepping a phase shifter through a plurality of settings, an offset value for the phase shift is generated based on the measurement.

Description

KI I-011-PCT PATENTOn-Chip Calibration of Channel-t o-Channel Phase Variation for Beamforming Integrated CircuitsCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U. S. C.§119 from U. S. Provisional Application Number 63 / 748, 062 entitled " PHASE INVARIANT VARIABLE GAIN AMPLIFIER FOR BEAMFORMING APPLICATIONS, " filed on January 22, 2025, the subject matter of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosed embodiments relate generally to transceivers, and, more particularly, to calibration of channel-to-channel phase variation for beamforming applications.BACKGROUND

[0003] Wireless communication systems increasingly rely on beamforming integrated circuits (BFICs) to enable electronic beam steering for phased array antennas. These systems utilize arrays of antenna elements, each driven by a dedicated channel containing electronic phase shifters and variable gain ampl i fiers (VGAs ), to synthesize transmit (TX) and receive (RX) beams with specific direct ional and power characterist ics. By electronically adjusting the phase and amplitude of the signal at each element, the combined wavefront can be shaped and steered to a desired angle without mechanical movement.

[0004] Precision in beamforming requires tight synchronization between the channels of the phased array.KI I-011-PCT PATENTHowever, practical implementations of BFICs often suffer from systematic phase mismatches between different channels. There is systematic phase mismatch between different channels, whether the different channels are on the same or different chips. These variations can arise from semiconductor process variations, thermal gradients, layout asymmetries, and differences between separate integrated circuit chips used to construct larger arrays. Such phase errors degrade the quality of the formed beam, leading to reduced gain, distorted beam patterns, and poor side-lobe suppression. The calibration of a phased array often requires over-the-air measurements which can be time consuming and costly.

[0005] There is a need to develop mechanisms to minimize the impact of these variations in order to reduce phased array module fabrication costs and reduce calibration complexity.SUMMARY

[0006] Method and apparatus are provided for calibrating phase settings of beamforming transmit and receive channels associated with an array antenna. In one novel aspect, calibration circuitry upconverts a calibration stimulus and then applies the calibration signal to one or more transmit channels, or to one or more receive channels, after traversing the respective phase shifters, mixer circuitry downconverts the signal by mixing it with the LO signal to produce a calibration measurement signal for measurement. In some implementations, the transmit calibration signal is generated by upconverting a baseband (BB) orintermediate-frequency ( IF ) stimulus (e. g., a tone) using the LO signal In various embodiments, calibration isKI I-011-PCT PATENTperformed using a calibration stimulus and a measurement path that are both referenced to a common local oscillator (LO) signal, such as an LO signal received at an LO input port from an external source. The need for over-the-air measurements is eliminated.

[0007] In other embodiments, calibration includes varying a phase shifter over a plurality of phase settings and evaluating amplitude information of the calibration measurement signal versus phase setting to determine a phase offset, including identifying a zero crossing of a sinusoidal relationship between measured amplitude and phase setting. The resulting phase offsets may be stored in memory (e. g., in a look-up table ) for subseguent phase correction during beamforming operation. Calibration may be performed for multiple channels and antenna elements, including seguentially selecting channels or sets of channels to determine corresponding phase offsets. In some embodiments, down conversion is implemented as single-stage or dual-stage conversion, including an intermediate frequency stage and a subsequent baseband stage.

[0008] In further embodiments, a combined apparatus is selectively operable in a transmit calibration mode or a receive calibration mode under control of mode control circuitry. In transmit calibration mode, one calibration path provides a transmit calibration signal and another calibration path downconverts sampled transmit-channel signals to provide transmit-side calibration measurements. In receive calibration mode, a calibration path provides an injected test signal to the receive channels and another calibration path downconverts receive-channel calibration signals to provide receive-side calibration measurements. Depending on implementation, calibration circuitry may beKI I-011-PCT PATENTshared or partially shared across transmit and receive calibration operations while maintaining LO-ref erenced coherence.

[0009] Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 illustrates an exemplary diagram of an apparatus configured with a single-stage down-conversion to calibrate the TX path.

[0011] Fig. 2 illustrates an exemplary diagram of an apparatus configured with a two-stage down-conversion to calibrate the TX path.

[0012] Fig. 3 illustrates an exemplary diagram of an apparatus configured with a single-stage down-conversion or an optional two-stage-down-conversion to calibrate the RX path.

[0013] FIG. 4A illustrates an exemplary block diagram of dual-stage down-conversion mixer arrangement usable in a TX calibration measurement path.

[0014] FIG. 4B illustrates an exemplary block diagram of dual-stage down-conversion mixer arrangement usable in a RX calibration measurement path.

[0015] FIG. 5 illustrates an exemplary diagram illustrating a TX phase calibration method for calibrating channel-to-channel phase variation in a beamforming integrated circuit.

[0016] FIG. 6 illustrates an exemplary diagram illustrating an RX phase calibration method for calibrating channel-to-channel phase variation in a beamforming integrated circuit.KI I-011-PCT PATENT

[0017] . Fig. 7 illustrates an exemplary flowchart for the TX path calibration.

[0018] Fig. 8 illustrates an exemplary flowchart for the RX path calibration.DETAILED DESCRIPTION

[0019] Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0020] Beamforming integrated circuits (BFICs ) are used to provide electronic phase shifting for electronic steered phased arrays. These blocks rely on electronic phase shifters and variable gain amplifiers to synthesize different beams with different shapes, angles and power. However, one issue with BFICs is that there is systematic phase mismatch between different channels, whether the different channels are on the same or different chips.Therefore, there is a need for phase calibration amongst different channels for both the transmit (Tx) and receiving (Rx) paths.

[0021] Fig. 1 illustrates an exemplary diagram of an apparatus configured with a single-stage down-conversion to calibrate the TX path. The apparatus includes two TRX front-ends TRX 110 and TRX 130 each coupled totransmit / receive switch (T / R SW) 127 and T / R SW 147, respectively. While in this embodiment, a T / R SW is used as the duplexer, other embodiments may use other components in place of the T / R SW as a duplexer such as a diplexer or CMOS circulator. T / R SW 127 and T / R SW 147 are coupled to antenna ports 151a and 151b, respectively. Each TRX frontend includes a transmit channel and a receive channel. For example, TRX 110 includes a transmit channel 101 and aKI I-011-PCT PATENTreceive channel 102. In the receive channel 101, amplifier stages 111 and variable gain amplifier (VGA) 116 and a phase shifter 115 are arranged along the signal path. In transmit channel 102, amplifier stages 121, 122, and VGA 126 and a phase shifter 125 are arranged along the TX path. Similarly, TRX 130 includes an RX path and TX path coupled to T / R SW 147. A RX path including amplifier stage 131, phase shifter 135, and VGA stage 136, and a TX path including amplifier stages 141, 142, and VGA 146, and phase shifter 145.

[0022] The apparatus further includes calibration / feedback circuitry 106. Circuit 106 may correspond to a feedback receive / transmit (FBTRX) -type block. Within block 106, selectable gain paths include amplifiers 161 and 162 ( illustrated with switchable selection), amplifier 182, and a mixer 168 provides frequency conversion to produce a measurable calibration signal at test port 108. Amplifier 162 for the RX path is disabled. A gain element 182 is coupled between buffer 181 and the mixer input path to provide amplification of a routed / sample signal prior to mixing. An external local oscillator (LO) signal is received at LO INPUT 103, buf fered / amplif ied by LO buffer 181, and distributed through LO branch buffers 183 and 185 to excitation mixers and / or other circuitry requiring the LO reference.

[0023] A calibration stimulus at baseband or intermediate frequency is provided via BB / IF PORT 104. In the illustrated embodiment, BB / IF condit ioning / driver amplifier 184, selected by a switch network as shown, provides the BB / IF calibration stimulus to mixer 171. Mixer 171, when enabled receives the LO reference via buffer 183 and generates upconverted calibration signals that areKI I-011-PCT PATENTamplified along selectable gain amplifier 188 before being coupled into splitter / combiner 158. For the TX calibration illustrated, amplifiers 185, 186 and 187, and mixer 172 may be disabled.

[0024] In one TX calibration embodiment, a BB / IF calibration stimulus (often a tone, or a BB signal or an IF signal ) is applied at BB / IF INPUT 104 and upconverted by one of mixer 171 using the LO from LO INPUT 103, producing a transmit calibration signal that is amplified (e. g., by 188 ) and routed via splitter / combiner 158 into one or more selected transmit channels (e. g., channel 102 using phase shifter 125, and or TX channel of TRX 130 using phase shifter 145 ). The resulting RF signal at the antenna-side interface is sampled through a coupling circuit (e. g., 150a at antenna port 151a, or 150b at antenna port 151b) and routed back toward the calibration / feedback circuitry 106, optionally amplified by 161, and downconverted by mixer 168 using the same LO reference, optionally amplified by amplifier 182 to produce a calibration measurement signal at test port 108. In some embodiments, during calibration the phase shifter in the selected transmit channel is configured to step through multiple phase settings. In some embodiments, the calibration measurement signal is processed to obtain amplitude information, for example, the calibration measurement signal can be mixed with the calibration stimulus signal applied to BB / IF port 104 to obtain amplitude information at the test port. A phase offset is determined (e. g., via identifying a zero crossing in the sinusoidal relationship between measured amplitude and phase setting), with offsets optionally stored in a memory for later beamforming correction.KI I-011-PCT PATENT

[0025] In one embodiment, configuring the apparatus for TX calibration is done by applying a calibration enable signal and TX calibration enable signal to the calibration circuitry to enable all the TX calibration elements while leaving the RX calibration elements disabled.

[0026] Fig. 2 illustrates an exemplary diagram of an apparatus configured with a two-stage down-conversion to calibrate the TX path. The apparatus includes TRX frontends TRX 210 and TRX 230 each coupled to T / R SW 227 and T / R SW 247, respectively. While in this embodiment, a T / R SW is used as the duplexer, other embodiments may use other components in place of the T / R SW as a duplexer such as a diplexer or CMOS circulator. T / R SW 227 and T / R SW 247 are coupled to antenna ports 251a and 251b. TRX 210 includes a receive channel 201 and a transmit channel 202 each coupled to T / R SW 227. Receive path 201 having amplifier stage 211, phase shifter 215, and variable gain amplifier stage 216, and a transmit channel 202 including amplifier stages 221, 222, phase shifter 225, and VGA stage 226. Similarly, TRX 230 includes a receive path and a transmit path coupled to T / R SW 247. A receive path including amplifier stage 231, phase shifter 235, VGA stage 236, and a transmit path including amplifier stages 241, 242, phase shifter 245, and VGA stage 246.

[0027] Signals from the TRX paths are coupled through a splitter / combiner 258. Calibration / feedback circuitry 206 includes selectable amplifiers 261 and 262, an amplifier 282, and a dual-stage mixer chain including pre-stage mixer 268 and post-stage mixer 269, which provides a calibration output at test port 208. The post-stage mixer 269 is coupled to a LOTF port 209 to support the second-stage conversion in this embodiment. An LO signal from anKI I-011-PCT PATENTexternal source is provided at LO INPUT 203, buffered by LO buffer 281, and distributed along LO branch 283 to excite mixer 271, and to the dual-stage down conversion chain (e. g., the LO input of pre-stage mixer 268 ). LO branch 285 and mixer 272 may be disabled. A calibration stimulus at baseband or intermediate frequency is provided at BB / IF PORT 204 and conditioned through BB / IF driver amplifier 284 to excite mixer 271. Amplifier 286 may be disabled. Outputs of the excitation mixers are amplified via selectable gain amplifier 288 and coupled into the splitter / combiner network 258 for delivery to a selected transmit channel. Amplifier 287 may be disabled.

[0028] A transmit calibration signal is generated by upconverting the BB / IF calibration stimulus input at 204 using the LO at 203 in an excitation mixer (e. g., 271 ) and routing the upconverted calibration signal via splitter / combiner 258 into a selected transmit channel (e. g., transmit channel 202 with phase shifter 225, and / or the transmit path of TRX 230 including phase shifter 245, and VGA 245, and amplifiers 241and 242 ). The resulting RF output is sampled through a coupling circuit (e. g., 250a and / or 250b) and routed toward calibration / feedback circuitry 206. The sampled signal is optionally amplified through a selected gain path via 261 (with 262 for the RX path being disabled), then downconverted by pre-stage mixer 268 using the LO signal optionally amplified by 282 to produce an intermediate-frequency ( IF ) calibration signal. The IF calibration signal is further downconverted by poststage mixer 269 using an LOZFsignal at LOZFport 209, producing a baseband calibration measurement signal at test port 208. The phase shifter in the selected transmit channel may be swept / stepped and the amplitude of theKI I-011-PCT PATENTmeasurement output may be observed for determining and storing an offset value for subsequent phase correction. In some embodiments, the calibration measurement signal at test port 208 is processed to obtain amplitude information, for example, the calibration measurement signal can be mixed with the calibration stimulus signal applied to BB / IF port 204 to obtain amplitude information at the test port

[0029] In one embodiment, configuring the apparatus for TX calibration is done by applying a calibration enable signal and TX calibration enable signal to enable all the TX calibration elements while leaving the RX calibration elements disabled.

[0030] Fig. 3 illustrates an exemplary diagram of an apparatus configured with a single-stage down-conversion or an optional two-stage-down-conversion to calibrate the RX path. The apparatus includes TRX front-ends TRX 310 and TRX 330 each coupled to T / R SW 327 and T / R SW 347, respectively. While in this embodiment, a T / R SW is used as the duplexer, other embodiments may use other components in place of the T / R SW as a duplexer such as a diplexer or CMOS circulator. T / R SW 327 and T / R SW 347 are coupled to antenna ports 351a and 351b. TRX 310 includes a receive channel 301 and a transmit channel 302 coupled to antenna port 351a through T / R SW 327. Receive channel 301 includes amplifier stage 311, phase shifter 315, and VGA stage 316, and a transmit channel 302 including amplifier stages 321 and 322, phase shifter 325, and VGA stage 326 (wherein the transmit channel is disabled in the RX mode ). TRX 330 includes a receive channel including amplifier stage 331, phase shifter 335, and VGA stage 336, and a transmit channel (disabled) including amplifier stages 341 and 342, phase shifter 345, and VGA stage 346KI I -011 -PCT PATENT

[0031] A splitter / combiner 358 couples to the TRX s ignal paths and to the cal ibrat ion in ject ion / measurement paths. Cal ibrat ion circuitry 30 6 includes selectable gain paths 361 and 362, a mixer 368, and an ampl i fier 382 coupled between the combining network 358 and the mixer path. Test port 308 is coupled to the mixer 368 for providing a cal ibrat ion st imulus at that node.

[0032] An LO s ignal from an external source i s provided at LO INPUT 303, buf fered by LO buf fer 381, and di stributed along LO branches 385 and 386 to support frequency convers ion operat ions. A BB / IF interface i s provided at BB / IF PORT 304, with driver ampli f ier 38 6 ( selected by a switch network for the RX mode as shown ). Ampl i f ier 384 may be di sabled.

[0033] F IG. 3 further i llustrates alternat ive down convers ion paths for Rx calibrat ion measurement s, a mixer 372 a for a s ingle-stage mixer circuitry or opt ional ly a two-stage mixer circuitry including a pre-mixer 372 a and a post-mixer 372b. Mixer 372 a i s opt ionally used with an addit ional mixer 372b to implement a second downconvers ion-stage us ing an LOIF s ignal provided at LOIF port 30 9. Ampli f ier stages 388 ( di sabled) and 387 provide selectable gain in the paths coupled between the conversion circuitry and the combiner / spl itter 358.

[0034] A receiving test cal ibrat ion st imulus (typical ly a BB / IF tone, although other st imuli may be used) may be applied at test port 308 and upconverted us ing the LO re ference at LO INPUT 303, opt ional ly ampl i fied by 382, ( e. g., by mixer 368 ), producing an upconverted test s ignal that i s routed via selectable gain ampli f iers ( e. g., 362 ) to a selected coupl ing circuit (e. g., 350 a and / or 350b ) for in j ect ion into a selected receive channel (e. g., receiveKI I -011 -PCT PATENTchannel 301 us ing phase shi fter 315, and / or receive channel o f TRX 330 via phase shi fter 335 and ampl i f ier 331 and VGA 336. The in j ected s ignal traverses the receive phase shi fter ( e. g., 315 or 335 ) and forms a receive-channel cal ibrat ion s ignal that i s returned via the combiner / spl itter 358 toward the down convers ion / measurement path.

[0035] In one embodiment, the receive-channel cal ibrat ion s ignal i s downconverted to BB / IF us ing a s ingle-stage mixer ( e. g., 372a ) re ferenced to the LO at 303 and provided to the BB / IF port 304 through the associated driver path ( e. g., 385 and 38 6 ). In another embodiment, the receivechannel cal ibration signal i s downconverted us ing a two-stage path including mixer 372 a (LO-ref erenced) and opt ional mixer 372b (LOIF-re f erenced via LOIFport 30 9 ) to provide a baseband calibration measurement signal at the BB / IF port 304 through the as sociated driver ampli f iers ( e. g., 385 and 38 6 ).

[0036] The receive phase shi fter (e. g., 315 ) is configured to step / sweep through a set o f phase sett ings. In some embodiment s, the cal ibrat ion measurement s ignal is proces sed to obtain ampl itude information, for example, the cal ibrat ion measurement s ignal can be mixed with the cal ibrat ion st imulus signal applied to test port 308 to obtain ampl itude informat ion at the BB / IF port. Ampl itude informat ion o f the downconverted output i s observed at the BB / IF port, and an o f fset value is computed ( e. g., from the s inusoidal ampl itude-versus-phase behavior ) and stored in memory for subsequent receive-s ide phase correct ion.

[0037] In one embodiment, configuring the apparatus for RX cal ibrat ion i s done by applying a cal ibrat ion enable s ignal and RX calibrat ion enable signal to enable al l the RXKI I-011-PCT PATENTcalibration elements while leaving the TX calibration elements disabled.

[0038] FIG. 4A illustrates an exemplary block diagram of dual-stage down-conversion mixer arrangement usable in a TX calibration measurement path. In this embodiment, there are two mixers, mixer 468a and mixer 469a, working together to act as mixer 168 illustrated in FIG. 1. The pre-mixer 468a downconverts the transmit test signal by mixing it with the LO signal 403a from the external source. In one embodiment, the LO signal is a tone. The post-mixer 469a further downconverts the transmit test signal by mixing it with an LOIFsignal 409a, which is an IF signal. In one embodiment, the IF signal is a tone.

[0039] FIG. 4B illustrates an exemplary block diagram of dual-stage down-conversion mixer arrangement usable in a RX calibration measurement path. In this embodiment, there are two mixers working together to downconvert the signal. The pre-mixer 468b downconverts the receiving test signal by mixing it with the LO signal 404b, and this output is applied to the post-mixer 469b. The post-mixer 469b further downconverts the receiving test signal by mixing the output from the pre-mixer with an LOIFsignal 409b, which is an IF signal.

[0040] FIG. 5 illustrates an exemplary diagram illustrating a TX phase calibration method for calibrating channel-to-channel phase variation in a beamforming integrated circuit. At step 501, a signal is injected through input port, which can be a BB or IF input port (BB / IF port ). While the preferred method is to use a tone for the signal, a broadband signal (modulated signal ) may be used as well. At step 501a, it is noted that i is set to "1", and so the next steps will apply to channel i (channel #1 ). Prior toKI I-011-PCT PATENTbeing applied to channel i, the BB or IF signal is upconverted. The upconverted signal may be at the center of the band of interest, at the center of the supported frequency range, or swept / stepped. At step 502, the signal is sensed at the output of channel i PA using the corresponding coupler. At step 503, the signal is downconverted by first mixer, such as mixer 168, by mixing it with a LO signal from an external source. At step 504, the downconverted signal is measured at a test port, such as test port 108. More specifically, the amplitude of the signal is measured and recorded at the test port. At step 505, the phase shifter in channel i is swept, and for each setting, the test port measures the signal and its amplitude. In other words, the phase shifter is stepped through all of its settings, and a measurement is taken for each setting. Measurement at the test port will produce the sinusoidal waveform of the signal in order to identify the zero crossing point. The zero crossing point is used to calculate the offset value for the phase shifter of channel i, and this offset value is stored in memory for subsequent use. At step 506, there is a check to see if i equals N, with N being based on the number of channels to be calibrated. I f i equals N, then the Tx phase calibration is complete (507 ). If i does not equal N, then i is increased by one at step 506a, and steps 502 through 506 are repeated for the next channel i+1.

[0041] FIG. 6 illustrates an exemplary diagram illustrating an RX phase calibration method for calibrating channel-to-channel phase variation in a beamforming integrated circuit. At step 601, a signal is injected through test port 308. It is preferred that the signal be a tone at the BB or IF frequency, but a broadband signal may be used asKI I-011-PCT PATENTwell. The resulting upconverted RF signal can be swept across the RF bandwidth to calibrate for variations across the band, or it can be in the center of the band of interest, or the center of the supported frequency range. I f a BB signal is used, then the BB signal could emulate a signal that would be received by the array when in use. At step 601a, it is noted that i is set to #1, and so the next steps will apply to channel i (channel #1 ). At step 602, the signal is injected into channel i using the coupler. In one embodiment, the coupler is a directional coupler. At step 603, the signal is downconverted by mixing the signal with a LO signal from an external source that is received from an LO input port. At step 604, the downconverted signal is measured at BB / IF PORT. More specifically, the amplitude of the signal is measured and recorded at the BB / IF PORT. At step 605, the phase shifter in channel i is swept, and for each setting, the amplitude of the BB or IF signal is measured at the BB / IF port. In other words, the phase shifter is stepped through all of its settings, and a measurement is taken for each setting. When the measured amplitude of the resulting sinusoidal waveform goes through the zero crossing, the phase shifter setting is noted and an offset value for the phase shifter of channel i is calculated. This offset value is stored in a look-up table in memory for subsequent use. At step 606, there is a check to see if i equals N, with N being based on the number of channels to be calibrated. If i equals N, then the Rx phase calibration is complete ( 607 ). I f i does not equal N, then i is increased by one at step 606a, and steps 602 through 606 are repeated for the next channel i+1.

[0042] Fig. 7 illustrates an exemplary flowchart for the transmit path calibration. At step 701, the apparatusKI I-011-PCT PATENTreceives, at a local oscillator (LO) input port, an LO signal from an external source. At step 702, the apparatus generates a transmit calibration signal using the LO signal to upconvert an IF / BB calibration stimulus. At step 703, the apparatus provides the transmit calibration signal to a transmit channel. At step 704, the apparatus samples, at a coupler, a transmit calibration signal that has traversed through a transmit phase shifter in the transmit channel. At step 705, the apparatus downconverts, at a first mixer, a sampled transmit-channel signal received from the coupler to generate a calibration measurement signal by mixing the sampled transmit-channel signal with the LO signal. At step 706, the apparatus measures the calibration measurement signal to determine a calibration offset setting of the transmit phase shifter.

[0043] Fig. 8 illustrates an exemplary flowchart for the receive path calibration. At step 801, the apparatus receives, at a local oscillator (LO) input port, an LO signal from an external source. At step 802, the apparatus receives an upconverted test signal at a coupler, wherein the upconverted test signal is generated by mixing a calibration stimulus with the LO signal at a first mixer. At step 803, the apparatus adjusts, by a receive phase shifter of a receive channel, a phase of the upconverted test signal received from the coupler to output a receive calibration signal. At step 804, the apparatus downconverts, at a second mixer, the receive calibration signal to generate a calibration measurement signal by mixing the receive calibration signal with the LO signal. At step 805, the apparatus measures the calibration measurement signal to determine a calibration offset setting of the receive phase shifter.KI I-011-PCT PATENT

[0044] Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims

KI I-011-PCT PATENTCLAIMSWhat is claimed is:

1. An apparatus for beamforming integrated circuits (BFIC) channel calibration, comprising:a local oscillator (LO) input port that receives an LO signal from an external source;one or more first channels, each comprising a phase shifter to adjust a phase of a first calibration signal; one or more second channels, each comprising a phase shifter to adjust a phase of a second calibration signal; first calibration circuitry comprising: a first mixer circuitry comprising at least one mixer electrically coupled to the LO input port, configured to upconvert a first calibration stimulus using the LO signal and to provide the first calibration signal to one or more first channels for a first mode of operation, or configured to downconvert at least one second phase adjusted calibration signal received from one or more second channels using the LO signal, and to generate a second calibration measurement signal for a second mode of operation; andsecond calibration circuitry comprising: a second mixer circuitry comprising at least one mixer coupled to the LO input port, configured to downconvert at least one first phase adjusted calibration signal to generate a first calibration measurement signal by mixing the at least one first phase adjusted calibration signal with the LO signal in the first mode of operation, or configured to upconvert a second calibration stimulus to provide the second calibration signal to the one or more second channels for the second mode of operation,KI I-011-PCT PATENT2. The apparatus of claim 1, further comprising a first port coupled to the first calibration circuitry and a second port coupled to the second calibration circuitry.

3. The apparatus of claim 2, wherein the first port is a baseband / intermedia-frequency (BB / IF ) port and wherein the first calibration stimulus is a BB signal, an IF signal, or a tone signal received from the first port.

4. The apparatus of claim 2, wherein the second port is a test port, and wherein the second calibration stimulus is a BB signal, an IF signal, or a tone signal received from the second port.

5. The apparatus of claim 2, further comprising a memory configured to store a look-up table, and wherein for a first mode of operation, the second port is configured to receive the first calibration measurement signal and for a second mode of operation, the first port is configured to receive the second calibration measurement signal.

6. The apparatus of claim 5, wherein, for a selected channel of the one or more first channels or the one or more second channels, the corresponding phase shifter is configured to step through a plurality of phase settings, and wherein the test port is configured to provide the calibration measurement signal for:measuring an amplitude of the calibration measurement signal for each phase setting of the corresponding phase shifter,determining an offset value based on a zero crossing point of a sinusoidal waveform of the calibration measurement signal,KI I-011-PCT PATENTand wherein the memory is further configured to receive the offset value and store the offset value in the look-up table for subsequent phase shift adjustments7. The apparatus of claim 1, wherein for a first mode of operation, the second mixer circuitry is configured to be a dual-stage down-conversion circuit comprising a pre-stage mixer that downconverts the at least one first phase adjusted calibration signal to an IF calibration signal by mixing the at least one first phase adjusted calibration signal with the LO signal, and a post-stage mixer that downconverts the IF calibration signal to generate the first calibration measurement signal by mixing the IF calibration signal with a local oscillator intermediate-frequency (LOIF) signal.

8. The apparatus of claim 1, wherein for the second mode of operation, the first mixer circuitry is configured to be a dual-stage down-conversion circuit comprising a pre-stage mixer that downconverts the second calibration signal to an IF calibration signal by mixing the receive calibration signal with the LO signal, and a post-stage mixer that downconverts the IF calibration signal to generate the calibration measurement signal by mixing the IF calibration signal with a local oscillator intermediate-frequency (LOIF) signal.

9. The apparatus of claim 1, wherein at least one channel of the one or more first channels and the one or more second channels further comprises a first amplifier coupled between a phase shifter of a corresponding channel and the second calibration circuitry, wherein the first amplifierKI I-011-PCT PATENTis configured to amplify corresponding first or second calibration signal.

10. The apparatus of claim 1, wherein the second calibration circuitry further comprises a second amplifier coupled between the one or more first or second channels and the second mixer circuitry.

11. The apparatus of claim 1, further comprising a splitter / combiner configured to distribute the first calibration signal to a plurality of first channels of the one or more first channels for the first mode of operation.

12. The apparatus of claim 11, wherein the second mixer circuitry is configured to downconvert a plurality of first phase adjusted calibration signals from the plurality of first channels by mixing the plurality of first phase adjusted calibration signals with the LO signal to generate a plurality of calibration measurement signals.

13. The apparatus of claim 1, wherein the first mixer circuitry is configured to downconvert a plurality of second phase adjusted calibration signals from a plurality of selected second channels by mixing the plurality of second phase adjusted calibration signals with the LO signal.

14. The apparatus of claim 1, further comprising one or more couplers, each coupled between a pair of channels and the second calibration circuitry, wherein each pair of channels has a first channel of the one or more first channels and a second channel of the one or more second channels.KI I-011-PCT PATENT15. A method, comprising:receiving, at a local oscillator (LO) input port, an LO signal from an external source;generating a transmit calibration signal using the LO signal to upconvert a baseband / intermediate-frequency (BB / IF) calibration stimulus;providing the transmit calibration signal to a transmit channel;sampling, at a coupler, a transmit calibration signal that has traversed through a transmit phase shifter in the transmit channel;downconverting, at a first mixer, a sampled transmitchannel signal received from the coupler to generate a calibration measurement signal by mixing the sampled transmit-channel signal with the LO signal; and measuring the calibration measurement signal to determine a calibration offset setting of the transmit phase shifter.

16. The method of claim 15, wherein the downconverting is a dual-stage downconversion, comprising: downconverting the sampled transmit-channel signal to an IF calibration signal by mixing the sampled transmit-channel signal with the LO signal, and downconverting the IF calibration signal to generate the calibration measurement signal by mixing the IF calibration signal with a local oscillator intermediatefrequency ( LOIF) signal.

17. The method of claim 15, wherein the measuring the calibration measurement signal comprising:KI I-011-PCT PATENTmeasuring an amplitude of the calibration measurement signal for each phase setting of the corresponding transmit phase shifter, anddetermining the calibration offset setting based on a zero crossing point of a sinusoidal waveform of the calibration measurement signal.

18. A method, comprising:receiving, at a local oscillator (LO) input port, an LO signal from an external source;receiving an upconverted test signal at a coupler, wherein the upconverted test signal is generated by mixing a calibration stimulus with the LO signal;adjusting, by a receive phase shifter of a receive channel, a phase of the upconverted test signal received from the coupler to output a receive calibration signal; downconverting, at a second mixer, the receive calibration signal to generate a calibration measurement signal by mixing the receive calibration signal with the LO signal; andmeasuring the calibration measurement signal to determine a calibration offset setting of the receive phase shi ft er.

19. The method of claim 18, wherein the downconverting is a dual-stage downconversion, comprising: downconverting the receive calibration signal to an IF calibration signal by mixing the receive calibration signal with the LO signal, and downconverting the IF calibration signal to generate the calibration measurement signal by mixing the IF calibration signal with a local oscillator intermediate-frequency (LOIF) signal.KI I-011-PCT PATENT20. The method of claim 18, wherein the measuring the calibration measurement signal comprising:measuring an amplitude of the calibration measurement signal for each phase setting of the corresponding receive phase shifter, anddetermining the calibration offset setting based on a zero crossing point of a sinusoidal waveform of the calibration measurement signal.

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