LAUSR

A pulsed chirping phased-array transceiver (TRX) is demonstrated for X-band synthetic aperture radar (SAR) application. The phased-array TRX is implemented on a single CMOS chip with beamsteering/beamforming capabilities. The chip-scale radar TRX is composed of four transmitters (TXs) and four receivers (RXs) operating at 10-GHz center frequency with 1-GHz bandwidth (BW). To achieve the wideband beamsteering with a fine angle step, the two-stage delay control in the TX is proposed, where a delay-locked loop (DLL) -based multi-phase synthesizer (MPS) is used to control the coarse true-time delay of the baseband chirp, and the active phase shifters (PS) in radio frequency (RF) path are used for fine phase tuning. Fabricated in a 65-nm CMOS technology, the TRX consumes 228 mW for each channel at a 1.2-V supply, delivering ~10.2-dBm power with <1.3-dB ripple. The delay-line test shows that the dechirped signal achieves −13-dB peak-to-sidelobe ratio (PSLR) and the phase coherence error is within ±1.2° at a chirp rate of 1 MHz/ $\mu \text{s}$ . The prototype phased-array radar TRX chip is demonstrated with the antenna arrays consisting of Vivaldi antennas of 8-dBi gain, 6-GHz BW, and 6-cm pitch distance. Experiments indicate that beamsteering/beamforming up to ±60° with a step of ~1° is achieved. SAR imaging experiment is carried out based on both the two-stage beamsteering in the TXs and the digital beamforming in the RXs, proving the capability of the prototype phased-array radar TRX chip for the SAR imaging applications.