AN FMCW TRANSMITTER FOR SYNTHETIC APERTURE RADAR IMAGING BASED ON SYNTHETIC BANDWIDTH TECHNIQUE

Abstract

A fully integrated wideband FMCW radar transmitter based on synthetic bandwidth technique has been proposed in the thesis. The wideband chirp is synthesized by mixing 500-MHz chirp from PLL with multiple high frequency carriers generated from sub-harmonic injection locking oscillator. The wideband PLL covering 1.8~2.3 GHz achieved low in-band phase noise of -115~120 dBc/Hz. The technique can be easily extended for wider chirp bandwidth by increasing the number of output carriers. The transmitter supports pulse repetition period ranging from 0.3 to 6.3 ms. It consumes 84 mW. A Fractional-N Sampling PLL was also proposed as an alternative narrowband chirp generation. It requires no phase interpolator, DTC or background calibration. This SPLL employs two linear-slope generators and a 3-bit current domain phase interpolating charge pump to digitize the phase error. With a 50 MHz crystal reference, the in-band phase noise is measured to be -110.7 dBc/Hz @200 kHz.