A Spur Suppression Method in FMCW Radar by Reducing the Frequency Variation Periodicity with a PLL

This paper proposes a spur suppression method for a beat signal in a frequency-modulated continuous-wave (FMCW) radar system whose transmitted signals are generated by a PLL. To suppress spurs of the beat signal, frequencies of spurs are investigated with a stair-like frequency variation model. From the investigated model, we show that frequencies of spurs relate to a period of increment or decrement of phase-locked loop (PLL) output frequency. To reduce the periodicity of the frequency variation, we propose a method in which frequency control word (FCW) set period varies in each frequency chirp. We confirmed experimentally the reduction of spurious level by 13.6dB with the proposed method.