A 65nm CMOS low power impulse radar for respiratory feature extraction

This paper presents a wireless sensor system for monitoring human respiratory activities. The sensor is composed of a fully-integrated CMOS impulse radar chip and a DSP platform that is used for human respiratory feature extraction. The proposed and implemented radar chip was fabricated using in the TSMC 65nm CMOS technology. It can achieve the 1.5mm scanning resolution over the 15m scanning range with total 21mW power consumption. Moreover, the timing circuitry supporting range gated sensing and the pulse generator are all digital standard cell-based design which is very favorable to the technology scaling. The real-time DSP platform captures the wireless data via the CMOS radar chip and processes that through a human respiratory feature extraction algorithm. The entire system can fully operate to validate the performance of the wireless sensor system. Furthermore, the clinical trial was carried on and the system was proved helpful in rapid screen for respiratory diseases.

I. Introduction

Currently, intelligent wireless health care is becoming increasingly relevant. It significantly improves the quality of healthcare and provide human with a comfortable and pervasive care. Human respiration is basic parameter used to identify status of human body and can be used as indicators of major respiratory diseases. Once accident and emergency events can be forecasted immediately by health-care systems, it allows longer response time for medical treatment. One difficulty of the forecasting system lies in devices monitoring human respiration. Contactless wireless sensor serves this purpose. The continuous-wave Doppler radars are widely adopted in wireless sensor applications. Previous experimental research has successfully developed wireless heartbeat-sensing. However, it is difficult for continuous-wave radars to distinguish human respiration from more than one person. Another type of radar, impulse radar, was developed to sense both the position and vibration of targets [1]–[2]. Because of the superiority of short-duration pulses, the impulse radar helps in determining depth information and telling apart scattered waves reflected by various objects. However, the power consumption does not offer a competitive advantage over other radars, and the wide bandwidth feature requires the receiver to have high linearity to endure interference from non-targeted sources. Therefore, a passive front-end architecture with low power and high linearity is implemented in this paper. The timing circuitry and transmitter circuitry are implemented based on digital standard-cell design flow, which benefits from technology scaling. The proposed timing circuitry is superior to previous designs [1]–[2], attaining timing resolution of 10 ps at 10MHz repetition frequency.