An Electro-Optical Synthesizer to Generate Random Chirp Rates for Secure FMCW LiDAR Applications

This paper presents an electro-optical (EO) Synthesizer to generate frequency-modulated continuous wave (FMCW) signals with randomly changing chirp rates per frame using an on-chip SRAM-based physically unclonable function (PUF) block in 180nm RF CMOS. This approach is essential to secure FMCW light detection and ranging (LiDAR) against spoofing attacks. The architecture builds on an electro-optical phase-locked loop (EO PLL) integrated with a divide-by-2/3 fractional divider driven by an on-chip random key generator using PUF via a 2
^nd
-order delta-sigma modulator (DSM). The synthesizer provides four various programmable chirp rates ranging from 8.5GHz/ms to 12GHz/ms with a chirp period of 600µs. The EO Synthesizer improves the SFDR of the coherent receiver by ∼10dB compared to the open-loop modulation of the laser for FMCW ranging. The proposed method achieves 8x faster transition time compared with SSB-based EO PLLs. The proposed EO Synthesizer can be used for other applications in RF-photonics as well.