A 6.5~7.5-GHz CMOS Wideband FMCW Radar Transmitter based on Synthetic Bandwidth Technique
A fully integrated wideband FMCW radar transmitter based on synthetic bandwidth technique has been implemented in 55-nm CMOS technology. By mixing 500-MHz chirp from low frequency PLL fast switching carriers generated from sub-harmonic injection locked oscillator (SHILO), the transmitter can generate 1-GHz chirp with good phase noise. In the design, a wideband fractional-N PLL with randomized phase interpolation is employed to generate the desired 500-MHz chirp while achieving low in-band phase noise of -115~120 dBc/Hz. The high frequency SHILO also attains similar low in-band phase noise thanks to the injection locking property while achieving fast switching time less than 14 ns. The technique can be easily extended for wider chirp bandwidth by increasing the number of output carriers from SHILO. The transmitter supports pulse repetition period ranging from 0.3 to 6.3 ms. It consumes 84 mW, while occupying a total active area of 2.24 mm2.