UCLA

CMOS radar is a promising technique enabling applications like ground penetrating, weather observing, and even autonomous driving with its high integration level and cost effectiveness in mass production. Under an analog type waveform, performance of conventional linear frequency-modulated continuous-wave (FMCW) radar is heavily degraded by AM (envelop fluctuation) and FM (chirp non-linearity) distortions. In this dissertation, digital-intensive CMOS radar with digital modulated and coded waveform is proposed instead of using an analog chirp. Additionally, spread spectrum technique is adopted to expand radar signal across a wide bandwidth and therefore achieve good radar range resolution. Two digital-intensive radar systems and the fabricated CMOS implementations will be shown to demonstrate the proposed approaches.

First, an 89-93 GHz frequency hopping spread spectrum (FHSS) based FHCW radar with 4-GHz bandwidth / 3.75-cm range resolution is developed and implemented for automotive application to tolerate multi-user interference. To effectively mitigate the radar interference under an multi-user scenario, frequency hopping technique with one-coincidence codes is used to achieve multiplexing in the code domain. The unique orthogonal property of these one-coincidence codes prevent different users from occupying the same frequency channel at the same time. A cost-effective TX/RX module with the 28-nm CMOS chip and a Rogers patch antenna is developed for over-the-air verification, whose results demonstrate the multi-user capability of this FHCW radar.

Second, a 0.1-4.0 GHz direct sequence spread spectrum (DS/SS) based all-digital radar SoC is proposed and fabricated in 28-nm CMOS for ground-penetrating application. A time-domain digital correlation-based time-of-flight measurement is employed for radar ranging instead of a chirp or pulse. The SoC offers complete programmability over frequency and bandwidth due to the nature of inductor-less design, which allows the ground-penetrating radar (GPR) to be adopted to various sub-surface conditions. In-field GPR test with actual rover prototype validates the capability of the DS/SS radar. The 28-nm prototype radar SoC achieves a fine resolution of 3.75 cm and consumes 46.2 mW, which makes it suitable for low power applications.