A 4-Element Passive-Beamforming CT- ΔΣ ADC for Spatial Selectivity in Automotive Radar

This work demonstrates the benefit of spatial selectivity that a 4-element passive-beamforming continuous-time DSADC can offer for the extreme dynamic range requirements in automotive radar. The beamforming-DSADC is implemented in 40nm CMOS by R2R-based vector modulators as feed-in coefficients in combination with low-power implementations of a 4th-order inverter-based loop-filter, 4-bit asynchronous SAR-based quantizer and 4-bit current-steering feedback DACs. This work obtains >30dB of interferer suppression when deep notches are formed to obtain an effective spatial blocker dynamic range of 73.1dB. With notch-smoothing, the versatility to reduce the peak-to-notch-depth to 8dB for channel equalization is demonstrated. The beamforming-DSADC consumes 7.3mW.