A highly programmable 60-dB gain analog baseband circuit with DC-offset cancellation for short-range FMCW radar applications

This paper presents a fully integrated analog baseband circuit with high reconfigurability intended for use in short-range frequency-modulated continuous-wave (FMCW) radar sensors. The fully differential baseband circuitry achieves maximum overall gain of 60 dB which is adjustable with a 3-dB step. Second-order high-pass filter and fifth-order low-pass filter are incorporated in chain and possess tunable cutoff frequencies in the range 0.1–1 MHz and 0.25–1.3 MHz, respectively. They are adjustable with high accuracy, yielding simultaneously the rejection of undesired signals and neglecting the effects from process, voltage, and temperature variations. In order to enhance baseband circuit utilization and flexibility for radar’s targets with various proximities and velocities, two operating modes are proposed for low noise and high linearity. Simulated at maximum gain setting, it achieves an in-band third-order input intercept point of -17 dBm and an input-referred noise of 6.5 or 14.7 nV/√(Hz) depending on operating mode. Furthermore, DC offset cancellation circuit is incorporated in baseband chain. Implemented in a commercially available 130-nm SiGe BiCMOS process technology, as part of the large FMCW transceiver chip, it occupies the area of 0.36 mm^2 and consumes 30 or 33 mW in low-noise or high-linearity modes, respectively.