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[TI white paper: Webinar: mmWave Radar for Automotive and Industrial applications

](https://training.ti.com/epd-pro-rap-mmwaveradar-adh-tr-webinar-eu)

September 2019

Key ideas

  • Corner radars are SRR, for blind spot detection, lane change assist, etc
  • SRR usually occupy 77-81 GHz, while LRR occupy 76-77 GHz
  • Newer application: automated parking, in-cabin monitoring
  • chirp: linear FMCW
  • RF bandwidth vs IF bandwidth: RF bandwidth can be of few GHz, and IF bandwidth can be of few MHz.
  • Mixer multiplies Tx and Rx signal to get IF.
  • Roundtrip delay: td = 2R/c, beat frequency is B/Tc * td, chirp rate (frequency slope) and roundtrip delay.
  • Doppler: doppler changes both the frequency and phase of the IF signal. However it is more sensitive to phase shift, and thus we focus on phase shift in FMCW radar.
  • Range-Doppler map: usually the detection of objects are done on this image.
  • Typical process flow: ADC --> preprocessing (DC removal, interf-mitigation) --> 1st FFT on range --> 2nd FFT on Doppler --> Detection (OS-CFAR, CA-CFAR) --> 3rd FFT Angle estimation --> raw point cloud --> clustering, tracking --> radar tracklets/pins
  • Key design parameters:
    • Range resolution: dR = c/2B, range accuracy is small fraction of range resolution, and related to SNR
    • max velocity: v_max = lambda/4Tc. Tc is chirp duration. (intuitively, we want the sampling rate to be fast enough, among chirps)
    • velocity resolution: dv = lambda/2NTc (active duration of frame). velocity accuracy typically a fraction of the frame,
    • angle resultion: dtheta = 2/K, at theta=0 and assuming d=lambda/2

Notes

  • dbm: relative power to 1mWatt.
  • speed in m/s, such as 1 m/s is actually 2 mph. (x2.2 to be exact)
  • advanced techniques is needed to extend max velocity
  • longer window leads to better FFT results. radar DSP is all about recovering more information with limited side lobes with limited observation window.