A 260-mW Ku-Band FMCW Transceiver for Synthetic Aperture Radar Sensor With 1.48-GHz Bandwidth in 65-nm CMOS Technology

Abstract

Monolithic integration of synthetic aperture radar (SAR) transceiver with small size, lightweight, and low power consumption is suitable for uploading to a compact unmanned aerial vehicle (UAV) for SAR imaging. This paper presents a monolithic frequency-modulated continuous-wave (FMCW) SAR transceiver that works at Ku-band and centers at 15 GHz. Techniques to address the special requirements of UAV SAR are proposed. A digital-tunable mixed-signal-mode FMCW chirp synthesizer is designed to be power efficient, to provide a tunable chirp rate, and to enable digital minimization of the root-mean-square (RMS) frequency errors. A saturated driver-amplifier-power-amplifier chain and an input-load peak-staggering low-noise amplifier are implemented to nullify the ripple effects so that the degradations of imaging performances can be prevented. Moreover, a 12th order active-RC bandpass filter is used to suppress the intermediate frequency interferences of both ground reflections and antenna leakage. A binary-weighted programmable gain amplifier and a successive approximation analog-to-digital converter are also integrated into the chip. Fabricated using a 65-nm complementary metal-oxide-semiconductor technology, the prototype demonstrates 1.48-GHz chirp bandwidth and <186-kHz rms frequency errors in a programmable modulation period from 1.18 to 10 ms. The transmitter and receiver RF front end attains 1.1- and 0.51-dB ripples, respectively. The function of the FMCW SAR transceiver is validated through the delay line and near-field ranging tests. The SAR imaging experiment with a distance of around 110 m is successfully carried out using the chip prototype and a range migration algorithm. At 1.2-V supply, the transceiver chip consumes 259.4 mW.