A Ku-band CMOS FMCW radar transceiver with ring oscillator based waveform generation for snowpack remote sensing

This paper presents a Ku-band (14-16 GHz) CMOS frequency modulated continuous-wave (FMCW) radar transceiver developed to measure snow depth for water management purposes and to aid in retrieval of snow water equivalent (SWE). An on-chip direct digital frequency synthesizer (DDFS) and digital-to-analog converter (DAC) digitally generates the chirping waveform which then drives a ring oscillator based Ku-Band phase-locked loop (PLL) to provide the final Ku-band FMCW signal. Employing a ring oscillator as oppose to a tuned inductor based oscillator (LC-VCO) allows the radar to achieve wider chirp bandwidth resulting in a higher axial resolution (7.5cm) which is needed to accurately quantify the snowpack profile. The demonstrated radar chip is fabricated in a 65nm CMOS process, and it consumes 250mW of power under 1.1V supply, making its payload requirements suitable for observations from a small UAV.