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Multi-Mode Radar Reference Design

2021-03-31

Calterah’s automotive multi-mode mmWave radar reference design, empowered the Alps family of 77-GHz auto-grade and fully-integrated mmWave radar SoC chips, is system-level design that integrates the function of forward-looking radar and corner radar and offers 3 operation modes of LRR, MRR and SRR. This reference design enables real-time detection of objects in front of and beside the vehicle and provides their information with regard to range, relative velocity and azimuth, thus meeting the requirements of features like ACC (adaptive cruise control), AEB (automatic emergency braking), FCW (forward collision warning) and BSD (blind spot detection).

Specifications

Calterah’s automotive multi-mode mmWave radar solution has the following features:

  • Multiple operation modes, supporting long-range, medium-range, and short-range detection
  • 4 transmitters and 4 receivers (4T4R)
  • LRR Mode: 1T4R
  • MRR Mode: 3T4R
  • SRR Mode: 3T4R
  • Combination of LRR, MRR, and SRR Modes to achieve comprehensive detection with the maximum detection range of 191 meters in LRR Mode and broadest FOV of [-80°, 80°] in SRR Mode
  • Data fusion
  • Fusion of MRR and LRR, with a refreshing cycle of 100 ms
  • Fusion of MRR and SRR, with a refreshing cycle of 100 ms
  • Beam rotated by 45° in LRR Mode
  • Multi-mode tracking

How It Works

The solution integrates two corner radar modules in the front and two in the back of the vehicle. It produces three kinds of beamforming corresponding to the three operation modes. In LRR Mode, by rotating the wave beam by 45°, the radar can detect long-range objects in the 12 o’clock and 6 o’clock directions. The three modes work by turns in the sequence shown below.

Working Sequence of the Three Modes

Processing

This figure shows the processing flow of the multi-mode radar.

Processing Flow

The blue part represents the processings of RF and Baseband while the yellow part indicates those of the MCU for tracking.

  • Three modes work by turns
  • Fusion of MRR and LRR raw data with a refresh rate of 20 Hz
  • Fusion of MRR and SRR raw data with a refresh rate of 20 Hz
  • Maximum objects per frame: 256
  • T_f: 50 ms
  • T_sb: 25 ms
  • T_b0: 20 ms
  • T_b1: 18 ms
  • T_b2: 20 ms
  • T_b3: 17 ms
  • T_m: 2 ms
  • T_a: 2 ms
  • T_t: 20 ms
  • T_o: 19 ms
  1. The RF part transmits and receives signals in MRR Mode, and then the received signals go through 2D-FFT, CFAR, Velocity Anti-Ambiguity and DoA processings in the Baseband to generate the raw data.
  2. The MRR raw data is then stored into the MCU while LRR Mode is on for the RF and Baseband to generate LRR raw data.
  3. In the MCU, LRR raw data is fused with MRR raw data and processed for tracking.
  4. Likewise, MRR raw data and SRR raw data are generated, fused, and processed for tracking.
  5. The above steps iterate.

Tracking

The multi-mode radar solution provides adaptive tracking schemes to support cyclical tracking through fusion of data in different formats (2D, 3D), which improves robustness. It supports both signal-level and decision-making-level fusion for tracking and is suitable for detecting objects both in front of and behind a vehicle.