A 2-4GHz Wideband Transmitter Front-End for FMCW Through-Wall Radar Applications

This paper presents a 2-4 GHz wideband trans-mitter (Tx) front-end for a S-band through-wall frequency-modulated continuous waves (FMCW) radar transceiver, im-plemented in 40nm CMOS technology. The Tx front-end comprises a power divider (PD), a power amplifier (PA), and a distributed passive matching network (DPMN). To split the signal generated by the voltage-controlled oscillator (VCO) into two amplitude-controlled paths, to Tx front-end and Rx, a power divider circuit based on an equivalent lumped element model is proposed, with optimization performed through EMX simulations. Due to priority of linearity, A Class-A biased gain controllable power amplifier is designed to achieve wide bandwidth while addressing non-linearity concerns, providing stable per-formance across the bandwidth, with a power-added efficiency (PAE) of 21.5%. The whole Tx front-end in a FMCW TWR chip delivers maximum 14dBm output with a drain efficiency of 7.8% (low power input from VCO buffer), occupying 0.704 mm2, The spectrum measurement results of the FMCW input signal and the actual target detection results of the TWR in multiple scenarios prove that the proposed Tx front-end has robust per-formance and stability, balancing linearity, area and band-width.