High Resolution CMOS IR-UWB Radar for Non-Contact Human Vital Signs Detection

This paper presents an impulse radio ultra-wideband radar transceiver chip for monitoring human vital signs, featuring a spectrum adjustable transmitter and equivalent time sampling based receiver. The radar receiver samples the echo signal at 20.48 GS/s, which corresponds to a 7.4 mm range resolution using high-speed track and hold sampler. The received pulses are added up to increase the SNR of the receiver. With the proposed pseudo 16-bit DAC, an embedded DC-offset cancellation circuit can improve the dynamic range of the receiver according to the gain of integrator. Respiration and heartbeat of humans were detected by the proposed UWB radar transceiver, while consuming 55.2 mW from 1.2 V power supply. The radar transceiver chip was implemented in a 130 nm CMOS technology occupying chip area of 5.04 mm².

I. Introduction

Since 2002, the Federal Communications Commission (FCC) in the U.S. allowed the microwave frequency range of 3.1 G ~ 10.6 GHz for civilian usage [1]. Since then, numerous applications has been developed using impulse radio ultra-wideband (IR-UWB), such as security sensor, through-wall detection, surveillance, and even microwave imaging due to its advantages of high resolution, high penetration ability and low power consumption [2]–[4]. Especially, it is one of the best candidates for bio-medical sensing that IR-UWB technology can be extensively utilized as a human vital signs detection radar. In a sampling-based UWB radar receiver, real-time direct sampling method needs a high-speed (tens of GS/s) analog-to-digital converter (ADC) to meet the Nyquist criterion, since a typical pulse has duration of nanoseconds period. However, in order to track and detect slow moving target such as human vital signs, the equivalent time sampling (ETS) technique can be utilized without a power-hungry and complex ADC [2], [3].