Direct conversion Doppler radar vital sign detection system using power management technique

Abstract

Furthermore, the tunable operation frequency range of the proposed impulse generator is experimentally studied. This impulse generator can work well at any input frequency around 1-15 MHz. Figure 4 displays the experimental results of the final output impulses at operation frequencies of 1, 5, 10, and 15 MHz. It can be recognized that the lower frequency, the slightly higher amplitude. This is attributed to the recovery time of the RC-circuit of the collector resistance and the output coupling capacitor. When frequency is higher the period is shorter so that the output coupling capacitor has shorter time for recovery. Consequently, the output amplitude is lower. Therefore, by adjusting the values of the collector resistance and the output coupling capacitor, we can broaden the working frequency range. In addition, the fabricated impulse generator was checked by HP 8593E RF spectrum analyzer with generated high-order harmonic up to 10 GHz.With such output UWB short impulses, the impulse generator can be used for many practical applications in electronics and optics. By utilizing the fast leading edge characteristic of the generated short impulses for driving actively mode-locked fiber lasers, we may anticipate a possible generation of shorter optical pulses than reported in [6]. This issue is currently under investigation and will be reported elsewhere. CONCLUSIONIn this article, we have described a method for generating UWB picosecond impulses with fast fall-time based on the fast switchon characteristic of a broadband bipolar transistor and the edge compression characteristic of a NLTL comb generator. The experimental results showed that the generated short impulses had a pulse-width of about 725 ps, a fall-time of 180 ps, and a peak power of 1 W at 50 X. ABSTRACT: This article is the first to present a low power consumption direct conversion Doppler radar vital sign detection system using a power management technique to detect biomedical signals. The optimal pulse bias with simultaneous switching noise considered was designed to decrease power consumption of the sensor. A noncontact vital sign detection measurement using the optimal pulse bias was performed on a human subject. Based on experimental results, the presented simple and low power system can accurately detect human cardiopulmonary activity, including respiration and heartbeat. Calculated physiological signal amplitudes based on a spectral analysis validates the detection result from presented work. When compared with the sensor using a power amplifier, the proposed sensor can achieve low power dissipation for biomedical monitoring and green energy applications.