Analog Baseband for a 76-81 GHz FMCW Automotive Radar Receiver

This paper presents an analog baseband block for a packaged 76-81 GHz transceiver chip implemented in 40 nm pure-CMOS for both long and short ranges frequency modulated continuous wave (FMCW) automotive radar. The transceiver consist of four-channels receiver and the analog baseband in each channel comprises of 4th order active-RC based Butterworth low-pass filter cascaded with fixed and programmable gain amplifiers (PGA) to achieve the required maximum gain and gain variation. The filter implements tunability in the bandwidth between 10M and 15 MHz and provides a fixed gain of 10 dB. The resistor divider based PGA provides 26 dB configurable gain using digital control bits with 2 dB step-size. The receiver baseband chain has a pass-band flatness with in-band ripple less than 1-dB, and a maximum gain of 50 dB. The DC offset cancellation (DCOC) implemented provides tunability in the high-pass low-frequency cut-off for effective power leakage rejection from the transmitter to the receiver chain. The in-band output P1dB of > 14 dBm and an out-of-band OP1dB of > 7 dBm with a noise-figure of < 18 dB ensures good linearity and SNR in line with current industrial standard.