Method and apparatus for FMCW based radar operations

Abstract

Disclosed techniques provide mechanisms for a radar module to learn linearization values for use in performing frequency sweeping during Frequency Modulated Continuous Wave (FMCW) based radar sensing, where the linearization values compensate for nonlinearities in the circuitry used to perform frequency sweeping during radar operation. Operation of an example radar module according to the disclosed techniques includes performing a calibration procedure to learn the linearization values and using the learned linearization values to perform frequency sweeping during FMCW based radar sensing. The radar module includes a primary frequency control circuit used to perform frequency sweeping during radar sensing and includes a potentially slower but highly linear secondary control circuit that serves as a calibration reference for the primary control circuit. Advantageously, the calibration procedure also includes monitoring for interference within the radar frequency range and performing discontinuous radar reception and, optionally, discontinuous radar transmission at interfered frequencies.

Description

[0001] METHOD AND APPARATUS FOR FMCW BASED RADAR OPERATIONS

[0002] TECHNICAL FIELD

[0003] A method and apparatus embody radar operation techniques for Frequency Modulated Continuous Wave (FMCW) based radar sensing.

[0004] BACKGROUND

[0005] Frequency Modulated Continuous Wave (FMCW) radar is a type of radar system that measures distance, velocity, and other characteristics of surrounding objects by sending out a continuous wave signal and measuring the frequency shift of the returned signal.

[0006] In more detail, an FMCW based radar system generates a continuous wave radio signal that is “chirped.” Chirping refers to sweeping the transmitted radar signal over a defined frequency range in each one among a succession of windows of time, with each window comprising one “FMCW chirp.” Chirping results in a sawtooth or triangular pattern of frequency versus time for the radar signal and the return signal reflected back to the radar module, with the return signal shifted in time relative to the radar signal in proportion to the distance of the object reflecting the return signal back to the radar module. The shift in time corresponds to a shift in frequency between the return signal and the radar signal, the shift in frequency being proportional to the shift in time and to the rate of the frequency sweep. The frequency shift thus contains information about the distance to the reflecting object. Comparing the carrier phase shift between the return signal and the radar signal also provides information that can be used to detect small movements.

[0007] Various challenges arise with respect to imbuing consumer devices, such as smart phones or other wireless communication devices, with radar-sensing capabilities. Issues include achieving good performance at reasonable economic cost and acceptable power consumption.

[0008] Radar resolution depends on the radar signal bandwidth, making attractive the use of ultrawideband (UWB) radio transmitters and receivers, such as found in an increasing number of smart phones and other products. In terms of absolute frequency, “UWB” generally refers to signal bandwidths of at least 500 MHz, with the radio spectrum from 3.1 GHz to 10.6 GHz being of particular interest for UWB operations. See 802.15.4z-2020 for example details relating to UWB physical layers and associated ranging techniques, as promulgated by the Institute of Electrical and Electronics Engineers (IEEE).

[0009] SUMMARY

[0010] Disclosed techniques provide mechanisms for a radar module to learn linearization values for use in performing frequency sweeping during Frequency Modulated Continuous Wave (FMCW) based radar sensing, where the linearization values compensate for nonlinearities in the circuitry used to perform frequency sweeping during radar operation. Operation of an example radar module according to the disclosed techniques includes the radar module performing a calibration procedure to learn the linearization values and using the learned linearization values to perform frequency sweeping during FMCW based radar sensing. Advantageously, the calibration procedure also includes monitoring for interference within the radar frequency range and performing discontinuous radar reception and, optionally, discontinuous radar transmission at interfered frequencies.

[0011] An example embodiment of the disclosed techniques comprises a method of operating a radar module configured for FMCW based radar sensing, the method includes performing a calibration procedure. The calibration procedure includes detecting one or more interfering signals within a defined frequency range used for the FMCW based radar sensing and determining a plurality of linearization values for linearizing a frequency sweep of the radar module over the defined frequency range. The method further includes performing the FMCW based radar sensing by performing a succession of FMCW chirps, each FMCW chirp based on performing the frequency sweep according to the plurality of linearization values. FMCW based radar sensing further includes the radar module suspending return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

[0012] Another example embodiment includes a radar module configured for FMCW based radar sensing. The radar module includes a transmitter configured to transmit a radar signal, a receiver configured to receive reflections of the radar signal as a return signal, and processing and control circuitry operatively associated with the transmitter and receiver. The processing and control circuitry is configured to perform a calibration procedure. The calibration procedure includes detecting one or more interfering signals within a defined frequency range used for the FMCW based radar sensing and determining a plurality of linearization values for linearizing a frequency sweep of the radar module over the defined frequency range. Further, the processing and control circuitry is configured to perform the FMCW based radar sensing by performing a succession of FMCW chirps, each FMCW chirp based on performing the frequency sweep according to the plurality of linearization values, and suspending return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

[0013] Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure l is a diagram of an example pattern of frequency versus time for a radar signal and a corresponding return signal, in the context of Frequency Modulated Continuous Wave (FMCW) chirps that are characteristic of FMCW based radar sensing.

[0015] Figure 2 is a diagram of linearization values determined according to an example embodiment of a radar-module calibration procedure, for linearizing the frequency sweep performed in FMCW chirps.

[0016] Figure 3 is a diagram of additional linearization values determined with respect to one or more detected interfering signals, according to an example embodiment.

[0017] Figure 4 is a block diagram of a radar module configured to determine and use linearization values for frequency sweeping during FMCW based radar sensing, according to an example embodiment.

[0018] Figures 5 and 6 are block diagrams of calibration circuit details for the radar module of Figure 4, according to example embodiments.

[0019] Figure 7 is a diagram of example linearization values, also referred to as calibration values, for a radar module that cooperatively employs a dual Digital-to- Analog Converter (DAC) arrangement to perform frequency sweeping for FMCW based radar sensing, according to an example embodiment.

[0020] Figure 8 is a logic flow diagram of a method operation by a radar module, according to an example embodiment.

[0021] Figure 9 is a logic flow diagram of example details for carrying out the method depicted in Figure 8.

[0022] Figures 10 and 1 la / 1 lb are diagrams depicting example return signal reception in the presence of skipped frequencies within a defined frequency range used for FMCW based radar sensing, according to an example embodiment.

[0023] Figure 12 is a block diagram of an apparatus incorporating a radar module, according to an example embodiment.

[0024] Figures 13 and 14 are block diagrams of a radar module, according to further example embodiments.

[0025] Figure 15 is a block diagram of a radar module according to another example embodiment.

[0026] Figure 16 is a logic flow diagram of a method of operation for the radar module depicted in Figure 15. DETAILED DESCRIPTION

[0027] Figure 1 illustrates a known approach to radar sensing, referred to as Frequency Modulated Continuous Wave (FMCW) based radar sensing. FMCW based radar sensing involves emitting a series of “FMCW chirps”, with each FMCW chirp based on sweeping the transmitted radar signal (TX) over a defined frequency range. In the diagram, each frequency sweep goes from frequency to frequency f2, with the span therebetween being the defined frequency range “R” used for FMCW based radar sensing.

[0028] For any one or more reasons, linearity of the frequency sweep may be difficult to achieve. For example, there may be a desire to use simple circuitry for carrying out the frequency sweeping. Further, the oscillator used for generating the frequency-swept signal may have non-linear tuning characteristics. Additionally, or alternatively, the required sweep rate may be such that implementation is difficult with conventional sweeping arrangements, such as Phase Locked Loops (PLLs).

[0029] According to techniques disclosed herein, a radar module configured to perform FMCW based radar sensing performs a calibration procedure for linearization of its frequency sweeping. Example advantages of the technique include but are not limited to allowing the use of relatively inexpensive and practical sweeping-control circuits that yield linear frequency sweeps even at very high sweep rates and even over UWB frequency ranges. Such frequency ranges may be well beyond the instantaneous receive bandwidth of the receiver included in the radar module.

[0030] As suggested in Figure 2, the calibration procedure determines a plurality of linearization values 10 used by the radar module during FMCW based radar sensing for linearization of the frequency sweep performed in each FMCW chirp. In one or more example embodiments, the plurality of linearization values 10 corresponds with a set of frequency positions 12 along the linear slope of the ideal frequency sweep. The set of frequency positions 12 may include a default or predetermined subset of frequency positions 12, such as equidistant positions spanning the defined frequency range going from frequency to frequency f2.

[0031] Figure 3 illustrates, however, that the set of frequency positions 12 may include one or more frequency positions 12 that are determined dynamically during the calibration procedure. For example, the calibration procedure may include detecting whether there are interfering signals within the defined frequency range. Figure 3 illustrates two interfering signals 14 by way of example, denoted as 14a and 14b for distinction. Here, the interfering signals 14 are detected within the defined frequency range, with the radar module determining additional frequency positions 12 as needed, to ensure that there are one or more frequency positions 12 “proximate” to each detected interfering signal 14. “Proximate” may have a default meaning, such as within a defined maximum frequency distance of any respective interfering signal 14. The defined maximum frequency distance may be based on, for example, a defined maximum bandwidth expected for interfering signals 14 and the bandwidth of the receiver. The number of additional frequency positions 12 determined depends on the number of interfering signals 14 detected within the defined frequency range and whether any of the default frequency positions 12 are proximate to any of the interfering signals 14. Of course, detection of interfering signals 14 may be limited to some maximum number, and that number may be based on first detected ones or strongest detected ones among all interferers present within the defined frequency range.

[0032] A particular detail shown in Figure 3 is having a proximate frequency position 12 on either side of an interfering signal 14. A pair of proximate frequency positions 12a and 12b are defined on either side of the interfering signal 14a and these may be considered as bounding or bracketing positions defining a frequency gap therebetween that provides for exclusion of the interfered frequencies from radar processing. One or both of the frequency positions 12a and 12b may be added positions, depending upon where the interfering signal 14a falls with respect to the default frequency positions. The same holds with respect to the pair of frequency positions 12c and 12d that bracket the interfering signal 14b.

[0033] Figure 4 illustrates an example radar module 20 that is configured for FMCW based radar sensing. The radar module 20 includes a transmitter 22 configured for transmission of a radar signal 24 from a transmit antenna 26. An optional switch SI included in one or more embodiments allows for selective disabling of the transmitter 22 from the transmit antenna 26. For example, in one or more embodiments, the radar module 20 disables the radar transmitter 22 during FMCW chirps at frequencies corresponding to detected interfering signals 14. Such disabling prevents the radar module 20 from interfering with the device(s) or system(s) associated with the interfering signal(s) 14. While disabling in the diagram is based on selective switch-based disconnection, alternative bases for disabling the receiver 28 and / or transmitter 22 may be used. Further, the approach used for disabling the receiver 28 may be the same or different than the approach used for disabling the transmitter 22.

[0034] A receiver 28 of the radar module 20 receives a return signal 30 via a receive antenna 32, where the return signal 30 is a reflection of the radar signal 24. Reception may be suspended on a selective basis, such as by disabling the receiver 28 at frequencies corresponding to detected interferers. In one example of selective disabling, a switch S2 allows for selective disconnection of the receiver 28 from the receive antenna 32. Refer back to Figure 1, for depiction of the relationship between the radar signal 24 and the return signal 30. In a low power embodiment of the radar module 20, such as might be used for operation in a UWB frequency range, there is no need for high radio frequency isolation between receiver and transmitter, meaning that the respective antennas do not need a large physical separation or other measures to improve isolation, and no RF cancellation path is necessary from the transmitter 22 to the receiver 28. However, the overall technique disclosed herein applies directly also to solutions based on a single antenna used for both radar signal transmission and return signal reception, in which case an RF isolation device, such as a circulator, is used to connect the receiver and transmitter to the antenna.

[0035] The receiver 28 outputs a received return signal 34, which may be a frequency down- converted, filtered, and amplified version of the antenna-received return signal 30. Processing and control circuitry 36 of the radar module 20 processes the received return signal 34 and outputs corresponding radar sensing results 38. The processing and control circuitry 36 in one or more embodiments includes an analog-to-digital converter (ADC) 37, for digitizing the received return signal 34 and corresponding processing in the digital domain. Radar sensing results 38 comprise, for example, a radar “image” indicating detected objects, or associated data, such as object distances, velocities, etc.

[0036] The processing and control circuitry 36 comprises fixed circuitry or programmatically configured circuitry or a mix of both. Example implementations include a microcontroller unit (MCU) that is configured to control the overall radar module 20 for FMCW based radar sensing, and to process the received return signal 34 to obtain the radar sensing results 38. Alternatively, one or more additional processors, such as a Digital Signal Processor (DSP) an Application Specific Integrated Circuit (ASIC) or a Field Programmable Gate Array (FPGA), provides at least some of the return-signal processing.

[0037] A particular feature of the processing and control circuitry 36 is its inclusion of, or association with, a calibration circuit 40. The calibration circuit 40 is used during performance of a calibration procedure that yields calibration data 42, for linearization of the frequency sweeping performed by the radar module 20 during FMCW based radar sensing. The calibration data 42 in one or more embodiments includes a plurality of linearization values 10 corresponding to a set of frequency positions 12 on a linear slope representing the ideal frequency sweep. The plurality of linearization values 10 may be referred to as calibration values. In the example implementation shown in Figure 4, the linearization values 10 comprise DAC commands 44 for a Digital-to- Analog Converter (DAC) 46 used to control the frequency sweeping during FMCW based radar sensing.

[0038] The DAC commands 44 comprise a set of DAC commands that are streamed to the DAC 46 by the processing and control circuitry 36 at a defined rate for each FMCW frequency chirp. The set of DAC commands causes the DAC 46 to output a first voltage-mode control signal 48 that drives a Voltage Controlled Oscillator (VCO) 50 that sets the operating frequency of the radar transmitter 22 and the radar receiver 28. The first voltage-mode control signal 48 may also be referred to as a first oscillator control voltage.

[0039] Thus, the DAC commands 44 can be understood as controlling the VCO 50 during FMCW based radar sensing, such that the frequency signal 52 output by the VCO 50 sweeps the defined frequency range during each FMCW chirp. Here, the output frequency signal 52 determines the operating frequency of the transmitter 22 and receiver 28. The operating frequency may be referred to herein as the “TX / RX frequency” of the radar module 20 and performing a frequency sweep in each FMCW chirp comprising sweeping the TX / RX frequency of the radar module 20.

[0040] Use of DAC -based frequency sweeping offers an advantageous approach to achieving very high chirp rates, e.g., 300 MHz / s or higher. High chirp rates are needed when generating FMCW chirps over a wide relative frequency range, such as in the 3.1 GHz to 10.6 GHz range.

[0041] In one or more embodiments, the DAC commands 44 may comprise first commands corresponding to the frequency positions 12 and second commands interpolated or extrapolated from the first commands, for smooth, linear sweeping of the TX / RX frequency of the radar module 20 over the defined frequency range in each FMCW chirp.

[0042] Calibration of the DAC 46 can be understood as compensating for integral nonlinearity of the DAC 46, as well as non-linearity of the frequency tuning characteristics of the VCO 50. Integral nonlinearity is the deviation between actual and ideal output values from the DAC for a given input value — i.e., a given DAC command. Each DAC command is a digital word, with the value of the digital word mapping to a corresponding output voltage level from the DAC.

[0043] The depicted PLL 54, the switch S3, the calibration circuit 40, and corresponding control by the processing and control circuitry 36 provide for performance of a calibration procedure in one or more embodiments. The calibration procedure determines the DAC commands 44, which, again, are one example of the linearization values 10 mentioned earlier.

[0044] By performing the calibration procedure in this embodiment, the radar module 20 learns the DAC commands 44 needed for the DAC 46 to drive the VCO 50 such that the frequency sweeps performed in FMCW chirps are linear.

[0045] The letter “C” is positioned by one output of the switch S3 to show the position of the switch S3 during the calibration procedure, while the letter “R” denotes the position of the switch S3 during FMCW based radar sensing. The processing and control circuitry 36 provides control of the switch S3. With the switch S3 set to the “C” position, a second voltage-mode control signal 56 as output by the PLL 54 drives the VCO 50. That is, the calibration procedure is based on driving the VCO 50 with the PLL 54 rather than driving it with the first voltage-mode control signal 48 output by the DAC 46. During calibration, these respective drive voltages 48 and 56 also feed into the calibration circuit 40. Calibration with this arrangement involves the processing and control circuitry 36 controlling the PLL 54 via a PLL control signal 58 so that the PLL 54 drives the VCO 50 to each frequency position 12 in the set of frequency positions. At each frequency position, the calibration circuit 40 allows the processing and control circuitry 36 to identify the DAC command that causes the voltage of the first voltage-mode control signal 48 to match the voltage of the second voltage-mode control signal 56. Here, “match” means that the two voltages are equal within the applicable tolerances. Such tolerances include the resolution of the DAC 46, and further tolerances associated with voltage sensing, PLL control, etc.

[0046] Use of the PLL 54 in this context offers a number of advantages, including inherent frequency linearity and the ability to drive the VCO 50 to known frequencies with high accuracy. However, the PLL 54 may not be well suited or even feasible for use during FMCW based radar sensing, given the high sweep rates that may be needed. For example, if the defined frequency range used for FMCW based radar sensing is an Ultrawideband (UWB) frequency range, the rate of changed needed for the voltage applied to the VCO 50 may exceed the operational limits of the PLL 54. Here, the phrase “UWB frequency range” means a frequency range of 500 MHz or greater.

[0047] With the radar module 20 of Figure 4 serving an example reference, one or more embodiments herein comprise a method of operating a radar module configured for FMCW based radar sensing. The method includes controlling a transmit / receive (TX / RX) frequency of the radar module during FMCW based radar sensing using a first frequency control signal output by a first control circuit providing a frequency sweep rate needed for FMCW chirping. With respect to Figure 4, the DAC 46 is an example of the first control circuit, and the first voltagemode control signal 48 is an example of the first frequency control signal. In this context, the first control circuit causes the TX / RX frequency to sweep over a defined frequency range during each one among a succession of FMCW chirps at a constant rate, responsive to a stream of control values, e.g., DAC commands, input to the first control circuit.

[0048] The method further includes determining the stream of control values during an offline calibration procedure that comprises controlling the TX / RX frequency of the radar module using a second frequency control signal output by a second control circuit that provides a linear control response for the TX / RX frequency. In Figure 4, the PLL 54 operating under frequency adjustment control of the processing and control circuitry 36 is an example second control circuit. The calibration procedure comprising using the second control circuit to move the TX / RX frequency to a plurality of frequency positions within the defined frequency range, with a dwell time at each frequency position, for determining the stream of control values such that the first frequency control signal matches the second frequency control signal — the PLL output — at the plurality of plurality of frequency positions.

[0049] A related embodiment comprises method of operating a radar module 20 configured for FMCW based radar sensing, with the method including performing FMCW based radar sensing by driving a VCO 50 of the radar module 20 with a first voltage-mode control signal 48 that is output by a DAC 46 receiving a stream of digital command values — DAC commands 44 — that sweeps the output frequency signal 52 over defined frequency range in each of a succession of FMCW chirps. As a precursor to performing the FMCW based radar sensing, the method includes performing a calibration procedure that comprises disabling a transmitter 22 of the radar module, to prevent transmission of a radar signal 24 during the calibration procedure. In one example, the transmitter 22 is disabled based on disconnecting it from a transmit antenna 26 of the radar module 20 via a controllable switch.

[0050] Performing the calibration procedure includes calibrating the DAC 46 for linear frequency sweeping of the VCO 50 over the defined frequency range, based on driving the VCO 50 with a second voltage-mode control signal 56 rather than the first voltage-mode control signal 48. The second voltage-mode control signal 56 is generated by a PLL 54, with the method including controlling the PLL 54 to hold each of one or more calibration frequencies — respective ones among the set of frequency positions 12 — within the defined frequency range, for determination of a corresponding calibration value — respective linearization values 10 — that cause the first voltage-mode control signal 48 to equal the second voltage-mode control signal 56. Here, “equal” means within applicable tolerances. The method further includes saving the one or more calibration values for generating the stream of digital command values that sweep the VCO 50 over the defined frequency range during performance of the FMCW based radar sensing. See, e.g., the calibration data 42 shown in Figure 4, which may be saved as part of the calibration procedure.

[0051] During FMCW based radar sensing, the frequency signal 52 output by the VCO 50 sweeps linearly over the defined frequency range, for each FMCW chirp. However, during the calibration procedure, the frequency signal 52 moves over and within the defined frequency range at a relatively slow sweeping or adjustment rate, with pauses — dwells — at the frequency positions 12. Here, “slow” is with reference to the sweep rate used during FMCW based radar sensing. The respective frequency positions 12 may be referred to as calibration frequencies, and these dwells provide time for the radar module to determine respective linearization values 10 corresponding to the calibration frequencies. Further, determining the one or more calibration frequencies may include using a receiver of the radar module to monitor for interfering signals 14 within the defined frequency range. Correspondingly, the method may include, for each of at least one detected interfering signal 14, choosing as corresponding calibration frequencies a first frequency that is below the detected interfering signal 14 and a second frequency that is above the detected interfering signal 14, the first and second frequencies defining an avoidance frequency range therebetween. This avoidance frequency range may be skipped during FMCW chirping, meaning that return signal reception is not performed with respect to the avoidance frequency range. Skipping in at least one embodiment further includes skipping radar signal transmission in the avoidance frequency range.

[0052] With respect to a detected cluster of two or more interfering signals, the method in one or more embodiments includes choosing the corresponding calibration frequencies as a first frequency below the detected cluster and a second frequency above the detected cluster, such that the avoidance frequency range spans the detected cluster. The interfering signals 14 may be narrowband interferers detected within an UWB frequency range used for FMCW based radar sensing.

[0053] Figure 5 illustrates example details for the radar module 20, with the transmitter 22 and receiver 28 omitted in the interest of focusing on feedback and control elements associated with performance of the calibration procedure according to one or more embodiments.

[0054] The PLL 54 includes a phase detector 60 that receives as inputs a reference frequency signal and a frequency feedback signal 62 derived from the output frequency signal 52 of the VCO 50. Namely, a programmable divider 64 outputs the frequency feedback 62, with the frequency relationship between the output frequency signal 52 and the feedback frequency signal 62 determined by the divider ratio imposed by the divider 64. Consequently, the signal processing and control circuitry 36 moves the output frequency signal 52 to any desired frequency within the defined range of adjustability by controlling the divider ratio of the divider 64. For example, the signal processing and control circuitry 36 may be provisioned with a mapping or function relating divider ratios to output frequencies, such that it can position the output frequency at any desired frequency position within the defined frequency range, within the applicable tolerance limits. Both integer-N and fractional-N operation of the PLL 54 is possible, so the calibration frequencies are not necessarily limited to integer multiples of the reference frequency, although that may be sufficient in some use cases. The phase detector 60 outputs a phase difference signal to a charge pump 66 of the PLL 54, with the output of the charge pump 66 passing through a low pass filter (LPF) 68, to form the second voltage-mode control signal 56. During the calibration procedure, the VCO 50 is driven by the second voltage-mode control signal 56, while the DAC 46 is driven by a successive approximation register (SAR) 70 that in turn is driven by a comparator 72. This input to the DAC 46 differs from that used during FMCW based radar sensing, during which the signal processing and control circuitry 36 drives the DAC 46 with a stream of DAC commands 44 that cause the output frequency signal 52 to linearly ramp over the defined frequency range during each FMCW chirp.

[0055] That is, during the calibration procedure, the output signal 74 from comparator 72 drives the SAR 70 until its output — a digital command for the DAC 46 — results in the first voltagemode control signal 48 matching the second voltage-mode control signal 56. The signal processing and control circuitry 36 captures this matching DAC command and saves it for use during FMCW based radar sensing. For example, the signal processing and control circuitry 36 controls the divider 64 to move the output frequency signal 52 to each one among a set of defined frequency positions 12 that lie on the idealized sweeping slope and, for each such frequency position 12, records the corresponding DAC command that causes the first voltagemode control signal 48 to match the second voltage-mode control signal 56. Again, “matching” means equaling within the limits of the applicable tolerances. The letter “C” shows the switch setting that is active for switches S3 and S4 during calibration, while the letter “R” shows the switch setting that is active during FMCW based radar sensing.

[0056] Performing the foregoing matching operations at each frequency position 12 yields a first set of DAC commands corresponding to the frequency positions, and the signal processing and control circuitry 36 in one or more embodiments interpolates or extrapolates additional DAC commands from the first set of DAC commands, to obtain a set of DAC commands 44 that causes the output frequency signal 52 to ramp linearly over the defined frequency range, with that set of DAC commands 44 “replayed” for each FMCW frequency chirp during FMCW based radar sensing.

[0057] Figure 6 illustrates substantially the same arrangement but where the DAC 46 comprises two DACS, including a first DAC 46a and a second DAC 46b. A summing circuit 76 outputs a voltage signal that is the sum of the output voltages (or currents) of the first and second DACs 46a and 46b, with an LPF 78 filtering that summed voltage signal to provide the first voltagemode control signal 48. The LPF 78 smooths steps arising from updating the DACs 46a and 46b in discrete time, and generally accounts for glitches or small discontinuities that may be associated with cooperatively controlling the two DACs 46a and 46b to produce the first voltage- mode control signal 48. In this two-DAC embodiment, the signal processing and control circuitry 36 captures linearization values 10 — i.e., matching DAC commands in this context — for each DAC 46a and 46b. Of course, it shall be understood that the DAC(s) in one or more embodiments may output current-mode signals. For example, DACs 46a and 46b may be current-mode output devices, which allows for easy summing of their respective currents. The summed current may be converted to a voltage-mode signal.

[0058] In at least one embodiment, the first DAC 46a has an output signal range corresponding to the overall defined frequency range, whereas the second DAC 46b has a smaller output signal range. These DAC output signals may be voltage-mode or current-mode as a matter of implementation choice. Regardless, with respect to example differences in output signal range, the second DAC 46b has an output signal range corresponding to a maximum defined distance between frequency positions 12 used during the calibration procedure. Such an arrangement allows the signal processing and control circuitry 36 to use the first DAC 46a to move to any given frequency position 12 within the defined frequency range, while using the second DAC 46 to progress to a next higher or lower frequency position 12 adjacent to the given frequency position 12. Further, the second DAC 46b may have a higher resolution than the first DAC 46b, with the first DAC 46a providing “coarse” frequency step control of the VCO 50 and with the second DAC 46b providing fine frequency step control.

[0059] Thus, in one or more embodiments, the first voltage-mode control signal 48 is formed as a sum of first and second voltages respectively output by first and second DACs 46a and 46b, and wherein the calibration procedure comprises, for each calibration frequency — each frequency position 12 — determining a first command value for the first DAC 46a that sets the first voltage equal to the second voltage-mode control signal 56 corresponding to the calibration frequency, and further determining a second command value for the second DAC 46b that results in the sum of the first and second voltages equaling the second voltage-mode control signal 56 corresponding to the next higher or next lower calibration frequency.

[0060] Figure 7 illustrates an example of the two-DAC approach by showing calibration points for the first and second DACs 46a and 46b — DAC1 and DAC2 in the illustration. Linear sweeping of the output frequency signal 52 may be based on setting DAC1 to a first value that corresponds to a frequency point falling on the ideal sweep slope and then holding that value while incrementing DAC2 until the summed output of DAC 1 and DAC2 is proximate to a next frequency point on the ideal sweep slope. At that next point, the second DAC may be reset to zero or to some small, calibrated value and the first DAC updated so that the combined DAC output corresponds to that next point, with the processing then repeating for each next point. During FMCW based radar sensing, then, the signal processing and control circuitry 36 coordinates two streams of DAC commands 44a and 44b, to move the output frequency signal 52 linearly over the defined frequency range in each FMCW chirp. For example, sweeping the VCO 50 over the defined frequency range while performing the FMCW radar sensing comprises, with respect to each calibration frequency, zeroing the second DAC 4b and setting the first DAC 46a to the corresponding first command value, and then ramping the second DAC 46b towards the second command value. And, as noted, in one or more such embodiments, the output voltage range of the first DAC 46a corresponds with the defined frequency range, and an output voltage range of the second DAC 46b corresponds with a defined maximum distance between successive calibration frequencies within the defined frequency range. The two-DAC solution has particular advantages in certain scenarios, such as when the defined frequency range is a UWB frequency range.

[0061] Figure 8 illustrates a method 800 of operation by an example radar module 20, where the method 800 includes performing (Block 802) a calibration procedure, such as described above, and then performing (Block 804) FMCW based radar sensing using the calibration results. At periodic or triggered instances, the method 800 includes the radar module 20 determining whether to recalibrate. If so (YES from Block 806), the radar module 20 repeats the calibration procedure (Block 802) to obtain updated calibration results and then begins FMCW based radar sensing using the updated calibration results (Block 804). In at least one embodiment, the radar module 20 is configured to recalibrate on a periodic basis and, additionally or alternatively, the radar module 20 recalibrates responsive to one or more conditions being satisfied.

[0062] For example, the radar module 20 may be integrated into a mobile apparatus and may recalibrate based on the speed and / or distance traveled by the mobile apparatus. Additionally, or alternatively, the radar module 20 may intersperse its FMCW based radar sensing with listening periods during which it monitors for interfering signals 14 within the defined frequency band used for FMCW based radar sensing and triggers the calibration procedure responsive to determining that detected interference deviates from that detected with respect to its most recent performance of the calibration procedure.

[0063] Figure 9 illustrates a method 900 of operation by a radar module 20. The method 900 can be understood as an implementation of the method 800 with example details. The method 900 presents an example calibration procedure that includes: detecting (Block 902) one or more interfering signals 14 within a defined frequency range used for the FMCW based radar sensing; and determining (Block 904) a plurality of linearization values 10 for linearizing a frequency sweep of the radar module 20 over the defined frequency range. Further, the method 900 includes carrying out FMCW based radar sensing by: performing (Block 906) a succession of FMCW chirps, each FMCW chirp based on performing the frequency sweep according to the plurality of linearization values 10; and suspending (Block 908) return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals 14.

[0064] The defined frequency range is UWB frequency range in one or more embodiments.

[0065] Suspending return signal reception comprises disabling a receiver 28 of the radar module 20. Disabling is based on, for example, using a switch to disconnect a receiver 28 of the radar module 20 from a receive antenna 32 of the radar module 20. Further, in one or more embodiments, each suspension in return signal reception results in a gap in radar data collected during each FMCW chirp, and the method 900 includes processing the radar data to compensate for the one or more gaps. For example, the processing and control circuitry 36 performs a data interpolation operation to fill in the gap(s).

[0066] Figures 10 and 1 la / 1 lb illustrate an example approach to compensating the radar data for a gap. The receiver 28 and / or the processing and control circuitry 36 includes an ADC used to digitize the received return signal 34, such as shown in Figure 4. Figure 10 illustrates ADC samples collected during a given FMCW chirp — chirp “n” — during FMCW based radar sensing. The ADC samples are collected on either side of a frequency gap. The portion of the frequency sweep on the lower-frequency side of the gap may be referred to as a first sub-chirp n, with the remaining portion of the frequency sweep referred to as a sub-chirp n+1. The processing and control circuitry 36 performs signal processing on these ADC samples, e.g., a Fast Fourier Transform (FFT), with the FFT processing accounting for the frequency gap. Note that Figure 10 serves as a discussion example; there may be more than one gap within the frequency range of interest and, consequently, more than two sub-chirps.

[0067] Figures I la and 1 lb illustrate an example gap in terms of ADC samples, between the last sample taken in sub-chirp n and the first sample taken in sub-chirp n+1. Particularly, Figure I la illustrates an uninterrupted — gapless — chirp for reference and shows given ADC samples, with not necessarily all ADC samples shown. The time interval At between successive ADC samples may be defined by the sampling frequency Fsof the ADC. Figure 1 lb illustrates an example chirp with one frequency gap, e.g., corresponding to a detected interferer. To the extent that there are multiple interfering signals 14 accounted for in the frequency sweep, there will be a gap corresponding to each one. Each such gap may be bounded by respective calibration frequencies, e.g., frequency points fcnand fcn+1in the depicted example

[0068] In addition to suspensions of return signal reception in frequency gaps corresponding to detected interfering signals 14, one or more embodiments of the method 900 include suspending radar signal transmission during each FMCW chirp, at frequencies corresponding to the one or more interfering signals 14. In at least one such embodiment, suspending radar signal transmission comprises disabling a transmitter 22 of the radar module 20. In one or more embodiments, disabling the transmitter 22 means controlling a switch that selectively disconnects the transmitter 22 from a transmit antenna 26 of the radar module 20.

[0069] Performing the frequency sweep in each FMCW chirp comprises, according to at least one embodiment of the method 900, controlling the TX / RX frequency of the radar module 20 via a voltage-mode control signal 48 generated by a DAC 46. Here, the linearization values 10 determined during the calibration procedure comprise DAC commands 44 that compensate for nonlinearities of the DAC 46 and VCO 50.

[0070] In at least one embodiment of the method 900, performing the calibration procedure comprises controlling the TX / RX frequency of the radar module 20 to dwell at each one among a set of frequency positions 12 on a linear slope spanning the defined frequency range, for determination of one or more corresponding linearization values 10. The set of frequency positions 12 includes, for example, predefined frequency positions spaced along the linear slope and one or more dynamically determined frequency positions, each dynamically determined frequency position proximate to a respective one among the one or more interfering signals 14.

[0071] In one or more embodiments of the radar module 20, a VCO 50 defines the TX / RX frequency of the radar module 20. In at least one such embodiment, controlling the TX / RX frequency of the radar module 20 to dwell at each one among the set of frequency positions 12 comprises driving the VCO 50 with a PLL 54 and controlling the PLL 54 to move the TX / RX frequency to each frequency position 12. Further, in at least one such embodiment, a DAC 46 rather than the PLL 54 drives the VCO 50 during the FMCW based radar sensing, and the plurality of linearization values 10 is a set of DAC commands 44 that yield a linear frequency sweep in each FMCW chirp. Determination of the DAC commands 44, for example, is based on, for each frequency position 12 within the set of frequency positions 12, determining the DAC command that results in a drive voltage output from the DAC 46 matching a drive voltage output by the PLL 54.

[0072] As shown in the examples of Figures 5 and 6, the DAC 46 in one or more embodiments comprises a pair of DACs 46, including a first DAC 46a having a first output signal range and a second DAC 46b having a smaller, second output signal range. Then, as suggested in Figure 7, performing the frequency sweep in each FMCW chirp comprises controlling the first and second DACs 46a and 46b such that a combination of respective output signals from the first and second DACs causes the VCO 50 to sweep linearly over the defined frequency range.

[0073] In a particular example, the second DAC 46b has a higher resolution than the first DAC 46a and any particular frequency along the ideal linear slope of the frequency sweep is represented by a pair of DAC commands, one for the first DAC 46a and one for the second DAC 46b. Consider the example set of frequency positions 12 introduced in Figure 2. Positioning the TX / RX frequency of the radar module 20 at any given frequency position 12 entails inputting a particular combination of DAC commands to the first and second DACs 46a and 46b and these can be regarded as a corresponding set of “starting values” representing that given frequency position 12. Advancing to the next frequency position 12 may exploit the higher resolution of the second DAC 46b, based on holding the starting value loaded into the first DAC 46a while successively updating the value loaded into the second DAC 46b. These successive updates occur at a rate corresponding with the required sweeping rate and they leave the TX / RX frequency just below the next frequency position 12 and moving to that next frequency position is based on loading a new set of starting values into the first and second DACs 46a and 46b and repeating the successive updating of the second DAC 46b.

[0074] In a related embodiment, a radar module 20 is configured for FMCW based radar sensing and comprises: a transmitter 22 configured to transmit a radar signal 24; a receiver 28 configured to receive reflections of the radar signal 24 as a return signal 30; and processing and control circuitry 36 operatively associated with the transmitter 22 and receiver 28. The processing and control circuitry 36 is configured to perform a calibration procedure comprising detecting one or more interfering signals 14 within a defined frequency range used for the FMCW based radar sensing and determining a plurality of linearization values 10 for linearizing a frequency sweep of the radar module 20 over the defined frequency range. Further, the processing and control circuitry 36 is configured to perform the FMCW based radar sensing by performing a succession of FMCW chirps. Each FMCW chirp is based on performing the frequency sweep according to the plurality of linearization values 10, and suspending return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals 14.

[0075] Broadly, the processing and control circuitry 36 is configured to control the radar module 20 to perform any one or more operations included in the methods 800 and 900, including any or all of the variations and extensions described herein.

[0076] Figure 12 illustrates an example apparatus 100 that incorporates a radar module 20 as described herein. The apparatus 100 comprises, for example, a wireless communications device, such as a smartphone, tablet, laptop, etc. In other examples, the apparatus 100 comprises or is integrated into an automobile or other type of vehicle, with the radar module 20 used for detecting surrounding objects.

[0077] The example apparatus 100 includes a power supply 102, processing circuitry 104, storage 106, and communications circuitry 108, along with a radar module 20 as described herein. Although the diagram suggests separate implementations of the communications circuitry 108 and the radar module 20, one or more embodiments of the apparatus 100 include circuitry or assemblies shared between the radar module 20 and the communications circuitry 108. For example, antennas may be shared and at least some circuitry may be shared. Similarly, the processing circuitry 104 may include at least a portion of the processing and control circuitry 36 described earlier.

[0078] Figure 13 illustrates an example implementation of the processing and control circuitry 36. A microprocessor or DSP or other digital processor 120 is specially adapted to carry out the operations ascribed to the processing and control circuitry 36, based on executing computer program instructions held in an associated memory 122. The digital processor 120 during its operation determines a plurality of linearization values 10 as described herein and holds them in the memory 122 for use in linearizing the frequency sweeping performed by the radar module 20 during FMCW based radar sensing.

[0079] Figure 14 illustrates another embodiment of the radar module 20, based on functional modules. Here, a functional module comprises a particular set of operations associated with carrying out a particular function. Functional modules may be implemented via a microprocessor executing computer program functions arranged to carry out the particular functions, with or without virtualization. In the illustrated embodiment, the radar module 20 includes a radar sensing module 130 configured to perform FMCW based radar sensing as described herein and includes a calibrating module 132 configured to perform the calibration procedure described herein.

[0080] Figure 15 illustrates yet another embodiment of a radar module 20 according to the techniques disclosed herein and can be understood as a generalized example. Transmitter / receiver details are omitted from the diagram for focus on the use of primary and secondary frequency control circuits 140 and 142, respectively. During radar operation, the TX / RX frequency of the radar module 20 is controlled via the primary frequency control circuit 140, i.e., the primary frequency control circuit 140 controls an oscillator 144 for frequency sweeping in the FMCW chirps. The oscillator 144 outputs a frequency signal 146 that defines the radar signal frequency of the radar module 20.

[0081] Advantageously, however, during the calibration procedure, the secondary frequency control circuit 142 controls the oscillator 144 via control of a switch 148 by the processing and control circuitry 36. In this arrangement, the secondary frequency control circuit 142 serves as a calibration reference for the primary frequency control circuit 140.

[0082] The secondary frequency control circuit 142 may be slower than the primary frequency control circuit 140 in terms of its control bandwidth or it may be otherwise unsuited for achieving the high sweep rate needed for frequency sweeping during FMCW chirps. However, the secondary frequency control circuit 142 may be highly linear or otherwise highly accurate by virtue of being operated in a closed loop arrangement with respect to a reference frequency. Put simply, the secondary frequency control circuit 142 allows the processing and control circuitry 36 to drive the oscillator 144 to known frequency positions with good accuracy.

[0083] Each such frequency position corresponds to a particular value of the frequency control signal 150 output by the secondary frequency control circuit 142. For each such frequency position, the processing and control circuitry 36 learns what value of control input to the primary frequency control circuit 140 causes the frequency control signal 152 output by the primary frequency control circuit 140 to match frequency control signal 150. “Matching” means equaling within the applicable control and sensing tolerances.

[0084] Consequently, for each frequency position, the calibration procedure involves the processing and control circuitry 36 to determine the control input value that causes the primary frequency control circuit 140 to output the same control signal as being output by the secondary frequency control circuit 142.

[0085] By defining these frequency positions on along a slope corresponding to the ideal linear frequency sweep, the processing and control circuitry 36 learns the set of control input values needed for the primary frequency control circuit 140 such that the output frequency signal 146 sweeps linearly during each FMCW chirp. Thus, FMCW chirping is based on the processing and control circuitry 36 replaying this set of control input values to the primary frequency control circuit 140 with the appropriate timing during each FMCW chirp window.

[0086] Further, the radar module depicted in Figure 15 may be further configured to monitor for interference during the calibration procedure and to skip return signal reception during radar operations for interfered frequencies. Skipping may further include skipping radar signal transmission for the interfered frequencies, to avoid causing interference associated with other devices or systems causing the detected interference. Avoiding transmission provides for coexistence with other radar devices and, in the context of cellular communications, allows for coexistence between radar operations by the radar module and communications operations by surrounding communications devices.

[0087] Figure 16 illustrates a method 1600 corresponding to the example details of Figure 15. The method 1600 includes disabling (Block 1602) the transmitter of a radar module for performance of a calibration procedure. Performing the calibration procedure comprises calibrating (Block 1604) a primary frequency control circuit of the radar module — i.e., the one used for frequency sweeping during FMCW based radar operations — with a secondary frequency control circuit. Such operations may include moving the operating frequency of the radar module to respective ones among a set of frequency positions along a linear slope representing an ideal frequency sweep and dwelling at each such frequency position at least long enough to allow frequency adjustment settling times and learning of the corresponding calibration value(s). Depending upon the implementation details of the primary frequency control circuit 140, more than one calibration value may be learned for each frequency position.

[0088] The method 1600 continues with the radar module performing radar sensing using the learned calibration values. That is, the radar module uses the learned calibration values directly or indirectly to control the primary frequency control circuit 140 during radar sensing, for linearized frequency sweeping.

[0089] Taking the foregoing example details into account, techniques disclosed herein provide for a wireless communication device or other apparatus 100 that is configured for harmonized operation with respect to radar sensing via an included radar module 20 and communications signaling in a cellular communications network. In one or more embodiments, FMCW based radar sensing avoids frequencies determined as having a high interference level, e.g., above a defined threshold, and use a signal stitching to enable an ultra-wideband radar utilizing a very wide frequency range even in strongly interfered environments.

[0090] The technique includes running the radar module in two phases, i.e., two modes of operation. A calibration phase allows the radar module to identify interference within the operating bandwidth, while radar sensing is performed during an operation phase. The transmitter of the radar module is inactive during calibration, with the radar module using its included receiver to monitor for potential interference at respective calibration frequencies, with frequencies detected as being interfered remembered. Then, during radar operation, the oscillator used for radar sensing is swept using calibrated control signals, and frequency regions where there is interference are skipped over and thus not received and, in at least one embodiment, not transmitted.

[0091] The result is signals received during a number of discontinuous sub-chirps within the successive FMCW chirps performed over defined frequency range. The sub-chirps corresponding to each frequency sweep can be combined by compensating for the missing sections due to the skipped frequencies. One option to accomplish that is to perform an FFT of the signal section to compensate, shift its time by rotating each frequency component proportional to the product of the time shift and its frequency, and then transform back to time domain with an IFFT. After such operations, the frequency components in the compensated signal section will fit together continuously with those in the previous section. Another option, to save some signal processing power, is to fit only the strongest frequency component, removing samples in the intersection between signal sections so the strongest signal becomes as close to periodic as possible. When all parts have been fitted together, FMCW processing can continue like in a conventional continuous sweeping radar. Thus, in one or more embodiments, an FMCW radar module with a fast frequency sweep (high chirp rate) and low output power is used to meet the spectral emission requirements of UWB operation. A PLL is used to calibrate the oscillator in frequency points — i.e., the aforementioned frequency positions 12 — evenly spread over the UWB range, to be able to generate a wide frequency sweep with high linearity. A DAC solution with two DACs and a low pass filter can be used to reduce the DAC linearity and sample rate requirements.

[0092] A highly linear receiver is provided for return signal reception, with the advantage of rejecting strong signals outside the receive channel bandwidth. Effectively, the receiver 28 may operate as a frequency translating feedback receiver by exhibiting impedance matching for frequencies that are close to the instantaneous frequency of the swept local oscillator — the VCO 50 — and otherwise exhibiting a low-ohmic input impedance that reflects interferers that are away from the instantaneous frequency.

[0093] By using the combination of FMCW and skipping frequencies, a receiver rejecting out of channel frequencies, and signal stitching, it is possible to operate a UWB radar over a very wide bandwidth despite the presence of strong interference. The combined calibration of the oscillator and characterization of the interference situation provides a cost and time efficient solution that is based on a radar module that performs FMCW based radar sensing over a defined frequency range, which may be an UWB range. In at least one embodiment: (1) the radar module skips frequencies associated with one or more detected interfering signals, (2) performs a multi-point frequency calibration of its RF oscillator using a PLL, while the transmitter is inactive and the receiver is active during calibration to monitor interference and decide which frequencies to skip, (3) performs stitching of the measurements of the different parts of each FMCW chirp, (4) rejects out of channel frequencies, such as using frequency translating feedback, and (5) uses two DACs to control frequency sweeping during FMCW chirping.

[0094] Using DAC 46a and DAC 46b from Figure 6 as an example reference for discussion, DAC 46a may be lower in resolution than DAC 46b and by itself may not be able to generate the first voltage-mode control signal 48 with sufficient resolution to set the VCO 50 precisely at a given calibration frequency — a given frequency position 12. However, assuming that the DAC 46b offers a higher resolution, it may be set to provide a relatively small but precise contribution to the first voltage-mode control signal 48. Thus, each calibration frequency point may be defined by a pair of DAC commands, one for DAC 46a and one for DAC 46b.

[0095] It may also be beneficial to have a second calibration value for the second DAC 46b, where the radar module 20 moves the TX / RX frequency of the radar module 20 during calibration to a next frequency position, while keeping — holding — the calibration value determined for the first DAC 46a for the previous frequency position. This approach allows the radar module 20 to characterize the command value for the second DAC 46b that generates the next frequency position 12. In turn, having these respective DAC values allows the radar module 20 to accurately determine the sweep between the two frequency positions.

[0096] For example, the processing and control circuitry 36 loads the DAC1 and DAC2 values for a first frequency position 12 — i.e., a given calibration frequency — and then sweeps the DAC2 value towards the value that would generate the next frequency position 12, while holding the DAC1 value unchanged. Without learning this second DAC2 value corresponding to the next frequency position 12, the radar module 20 would have to rely on different estimates for the DAC2 sweep final value, which may not be as accurate. Of course, there may be applications that do not require utmost accuracy and the broader technique admits variation in the calibration procedure.

[0097] Corresponding example operations include a radar module performing a first frequency sweep over a first contiguous UWB frequency range with a transmitter circuit disabled for frequency control calibration and interference detection and performing a second frequency sweep over a second non-contiguous frequency range with the transmitter circuit connected, where the gaps in the second sweep correspond to frequency regions containing interference at a level above a threshold. The radar module in this example performs a radar function based on the received reflected signal from the second sweep, e.g., it performs object detection such as may be used in a smartphone app.

[0098] Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is / are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMSClaims:

1. A method of operating a radar module configured for Frequency Modulated Continuous Wave (FMCW) based radar sensing, the method comprising: performing a calibration procedure comprising: detecting one or more interfering signals within a defined frequency range used for the FMCW based radar sensing; and determining a plurality of linearization values for linearizing a frequency sweep of the radar module over the defined frequency range; and performing the FMCW based radar sensing by: performing a succession of FMCW chirps, each FMCW chirp based on performing the frequency sweep according to the plurality of linearization values; and suspending return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

2. The method according to claim 1, wherein the defined frequency range is an Ultrawideband (UWB) frequency range.

3. The method according to claim 1 or 2, wherein suspending return signal reception comprises disabling a receiver of the radar module.

4. The method according to any one of claims 1-3, wherein each suspension in return signal reception results in a gap in radar data collected during each FMCW chirp, and wherein the method includes processing the radar data to compensate for the one or more gaps.

5. The method according to any one of claims 1-4, further comprising suspending radar signal transmission during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

6. The method according to claim 5, wherein suspending radar signal transmission comprises disabling a transmitter of the radar module.

7. The method according to any one of claims 1-6, wherein performing the frequency sweep in each FMCW chirp comprises controlling the TX / RX frequency of the radar module via avoltage-mode control signal applied to a Voltage Controlled Oscillator (VCO) and generated by a Digital-to-Analog Converter (DAC), and wherein the linearization values comprise DAC commands that compensate for nonlinearities of the DAC and the VCO.

8. The method according to any one of claims 1-7, wherein performing the calibration procedure comprises controlling the TX / RX frequency of the radar module to dwell at each one among a set of frequency positions on a linear slope spanning the defined frequency range, for determination of a corresponding linearization value.

9. The method according to claim 8, wherein the set of frequency positions includes predefined frequency positions spaced along the linear slope and one or more dynamically determined frequency positions, each dynamically determined frequency position proximate to a respective one among the one or more interfering signals.

10. The method according to claim 8 or 9, wherein a Voltage Controlled Oscillator (VCO) defines the TX / RX frequency of the radar module, and wherein controlling the TX / RX frequency of the radar module to dwell at each one among the set of frequency positions comprises driving the VCO with a Phase Locked Loop (PLL) and controlling the PLL to move the TX / RX frequency to each frequency position.

11. The method according to claim 10, wherein a Digital-to-Analog Converter (DAC) drives the VCO during the FMCW based radar sensing, and wherein the plurality of linearization values is a set of DAC commands that yield a linear frequency sweep in each FMCW chirp.

12. The method according to claim 11, further comprising determining the DAC commands based on, for each frequency position within the set of frequency positions, determining the DAC command that results in a drive voltage output from the DAC matching a drive voltage output by the PLL.

13. The method according to claim 12, wherein the DAC comprises a pair of DACs, including a first DAC having a first output signal range and a second DAC having a smaller, second output signal range, and wherein performing the frequency sweep in each FMCW chirp comprises controlling the first and second DACs such that a combination of respective output signals from the first and second DACs causes the VCO to sweep linearly over the defined frequency range.

14. A radar module configured for Frequency Modulated Continuous Wave (FMCW) based radar sensing, the radar module comprising: a transmitter configured to transmit a radar signal; a receiver configured to receive reflections of the radar signal as a return signal; and control circuitry operatively associated with the transmitter and receiver and configured to: perform a calibration procedure comprising detecting one or more interfering signals within a defined frequency range used for the FMCW based radar sensing and determining a plurality of linearization values for linearizing a frequency sweep of the radar module over the defined frequency range; and perform the FMCW based radar sensing by performing a succession of FMCW chirps, each FMCW chirp based on performing the frequency sweep according to the plurality of linearization values, and suspending return signal reception during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

15. The radar module according to claim 14, wherein the defined frequency range is an Ultrawideband (UWB) frequency range.

16. The radar module according to claim 14 or 15, wherein suspending return signal reception comprises disabling a receiver of the radar module.

17. The radar module according to any one of claims 14-16, wherein each suspension in return signal reception results in a gap in radar data collected during each FMCW chirp, and wherein the method includes processing the radar data to compensate for the one or more gaps.

18. The radar module according to any one of claims 14-17, further comprising suspending radar signal transmission during each FMCW chirp, at frequencies corresponding to the one or more interfering signals.

19. The radar module according to claim 18, wherein suspending radar signal transmission comprises disabling a transmitter of the radar module.

20. The radar module according to any one of claims 14-19, wherein performing the frequency sweep in each FMCW chirp comprises controlling the TX / RX frequency of the radar module via a voltage-mode control signal that is applied to a Voltage Controlled Oscillator (VCO) and generated by a Digital-to-Analog Converter (DAC), and wherein the linearization values comprise DAC commands that compensate for nonlinearities of the DAC and the VCO.

21. The radar module according to any one of claims 14-20, wherein performing the calibration procedure comprises controlling the TX / RX frequency of the radar module to dwell at each one among a set of frequency positions on a linear slope spanning the defined frequency range, for determination of a corresponding linearization value.

22. The radar module according to claim 21, wherein the set of frequency positions includes predefined frequency positions spaced along the linear slope and one or more dynamically determined frequency positions, each dynamically determined frequency position proximate to a respective one among the one or more interfering signals.

23. The radar module according to claim 21 or 22, wherein a Voltage Controlled Oscillator (VCO) defines the TX / RX frequency of the radar module, and wherein controlling the TX / RX frequency of the radar module to dwell at each one among the set of frequency positions comprises driving the VCO with a Phase Locked Loop (PLL) and controlling the PLL to move the TX / RX frequency to each frequency position.

24. The radar module according to claim 23, wherein a Digital-to-Analog Converter (DAC) drives the VCO during the FMCW based radar sensing, and wherein the plurality of linearization values is a set of DAC commands that yield a linear frequency sweep in each FMCW chirp.

25. The radar module according to claim 24, further comprising determining the set of DAC commands based on, for each frequency position within the set of frequency positions, determining the DAC command that results in a drive voltage output from the DAC matching a drive voltage output by the PLL.

26. The radar module according to claim 25, wherein the DAC comprises a pair of DACs, including a first DAC having a first output signal range and a second DAC having a smaller, second output signal range, and wherein performing the frequency sweep in each FMCW chirp is based on controlling the first and second DACs such that a combination of respective outputsignals from the first and second DACs causes the VCO to sweep linearly over the defined frequency range.

27. A wireless communication device comprising the radar module of any of claims 14-26.

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