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EP-4740032-A1 - METHOD AND APPARATUS FOR FMCW BASED RADAR OPERATIONS

EP4740032A1EP 4740032 A1EP4740032 A1EP 4740032A1EP-4740032-A1

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.

Inventors

  • Sjöland, Henrik
  • LJUNG, RICKARD
  • REIAL, ANDRES
  • BROSTRÖM, Henric
  • ZOU, Gang

Assignees

  • Telefonaktiebolaget LM Ericsson (publ)

Dates

Publication Date
20260513
Application Date
20230706

Claims (20)

  1. 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. 2. The method according to claim 1, wherein the defined frequency range is an Ultrawideband (UWB) frequency range.
  3. 3. The method according to claim 1 or 2, wherein suspending return signal reception comprises disabling a receiver of the radar module.
  4. 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. 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. 6. The method according to claim 5, wherein suspending radar signal transmission comprises disabling a transmitter of the radar module.
  7. 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 a voltage-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. 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. 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. 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. 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. 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. 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. 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. 15. The radar module according to claim 14, wherein the defined frequency range is an Ultrawideband (UWB) frequency range.
  16. 16. The radar module according to claim 14 or 15, wherein suspending return signal reception comprises disabling a receiver of the radar module.
  17. 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. 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. 19. The radar module according to claim 18, wherein suspending radar signal transmission comprises disabling a transmitter of the radar module.
  20. 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.

Description

METHOD AND APPARATUS FOR FMCW BASED RADAR OPERATIONS TECHNICAL FIELD A method and apparatus embody radar operation techniques for Frequency Modulated Continuous Wave (FMCW) based radar sensing. BACKGROUND 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. 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. 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. 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). SUMMARY 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. 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. 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,