A Type-3 FMCW Radar Synthesizer with Wide Frequency Modulation Bandwidth

This work presents a 5-GHz frequency-modulated continuous wave signal generator (FMCW). The presented circuit aims to generate a wider frequency modulation bandwidth at low center frequency that grants significant advantage at saving power. Utilizing a fractional- N phase-locked loop (PLL)-based synthesizer with a 50-MHz reference frequency as the FMCW generator, the synthesizer modulates the carrier frequency across a range of 700 MHz. A Type-3 architecture with a switchable polarity is embedded to improve the linearity around the chirp turning-around points (TAPs) and switching-band points (SBPs). Switching Band Control (SBC) circuit and Multi-varactor LC Voltage Control Oscillator (MV-VCO) are proposed as an efficient method to increase the modulation range so that the FMCW signal generator can achieve 21.43-cm resolution in distance detecting. Fabricated in a TSMC 40-nm 1P10M CMOS technology, the proposed generator consumes 3.3 mW power and occupies 0.497mm² die area. The measured root-mean-square (rms) frequency error of the generated triangle chirp over 1.15ms period is 625kHz.