A Digital Ultra-Fast Acquisition Linear Frequency Modulated PLL for mm-Wave FMCW Radars

We propose a new digitally-intensive frequency synthesizer for a 60 GHz wireless sensing FMCW radar system and verify it though detailed circuit-level and system-level simulations. It consists of a 21 GHz digital PLL and a frequency tripler. The 20 GHz digital PLL features ultra-fast acquisition (less than 5 mu s) and low phase noise (-80 dBc/Hz at 100 kHz offset) by adopting dynamic and hitless loop bandwidth control. Linear frequency modulation (LFM) produces a triangle-shaped chirp signal with 3.2 GHz bandwidth in a 2 ms sweep. The maximum frequency deviation is only 0.014% of the chirp bandwidth. A multiplier following the 20 GHz PLL extends the LFM bandwidth to 9.6 GHz centered at 60 GHz, resulting in a range resolution better than 5 cm.