A dual-mode signal generator using PLL for X-band radar sensor applications

This paper presents a dual-mode signal generator using a fractional-N phase locked loop (PLL) and frequency-sweep modulator (FSM) for X-band Doppler and frequency modulated continuous wave (FMCW) radar sensor applications. The key function of the proposed structure is a frequency sweep modulator (FSM), which changes the PLL division ratio to sweep output frequency according to the input control code. Thus, the proposed signal generator is easy to accommodate both Doppler and FMCW modes, simultaneously. The proposed dual-mode signal generator is realized using a 1P8M 0.13 μm CMOS process. The chip size is 1.45 mm2 excluding all the pads, and consumes 114 mW from a 1.2-V supply voltage. The output frequency range of the proposed PLL is from 9.7 to 12.4 GHz which covers X-band radar sensor application band. The output power of the proposed structure is uniformly transmitted within the allocated frequency range in FMCW mode. The phase noise is -78 dBc/Hz at 10-kHz offset at the frequency of 10.525 GHz, and -126.78 dBc/Hz at 25-MHz offset frequency.