本論文提出利用主動式開口環形共振腔（Active Split-Ring Resonators, Active SRR）應用於檢測人體微弱的生命訊號，包括脈搏訊號和手指指尖訊號。感測電路的部分主要分為被動共振腔(Passive Resonator Sensor)及主動回授回授網路(Active Feeddback Loop Circuit)，主動電路以正回授架構整合開口環形共振腔來設計此主動式微波共振器。此架構將原始被動電路之共振腔結合主動元件來產生其振盪效果，在整體系統之前端當作感測生理訊號的裝置。在系統的設計上，可利用系統之非線性特性的互調現象來提高量測的靈敏度，並且在電路的後端加上微分器電路來使高階諧振頻率隨著進一步依其階數而再放大，來改善偶數諧振頻率，透過更高倍量的頻率偏移來使量測的生理訊號更為靈敏。
雖然指尖訊號通常非常微弱，利用所提出的互調現象技術可將靈敏度提高1004.97％的放大倍率。利用SRR Sensor之耦合路徑來量測脈搏與指尖內的生理訊號，透過脈搏對頻率造成的偏移，高階互調頻率成分 (Intermodulation products)增強了微弱訊號源的頻率偏移量。手腕脈搏訊號量測之頻率偏移大約為3.62 MHz增加到36.38 MHz。在此實驗中可成功的量測到第20階的諧振頻率。另外，此技術量測指尖訊號與傳統的方法不同，利用微波感測的技術可透過訊號增強的效果將指尖訊號擷取出來，在頻域上與實際參考訊號相比可達到小於1.68％誤差的高精準度。

This paper presents a novel active split ring resonator (SRR) for detecting the wrist and fingertip pulse signals. The active planar resonator functions as a sensor, as well as a positive feedback element of the oscillator. In this paper, the differentiator cleverly employed to improve the harmonics of the even order IM products and the high order frequency component is used to enhance the deviation of frequency into a time-domain waveform signal in vital sign detection. Though fingertip signal is extremely tiny in general, the proposed intermodulation multiplication technology can improve the sensitivity by 1004.97％. The frequency shift of sensing can be multiplied to highly sensitive by measuring the high level even order intermodulation (IM) components. The pulse signal can be measured from the frequency deviations of SRR by interfering the coupling path on the surface of the sensor. In this work, the highest component can be achieved to 20th IM. The frequency shift of measuring the wrist pulse signal is increased from 3.62 MHz to 36.38 MHz, approximately. Different from previous method, the fingertip signal is first measured by a microwave sensor and can achieve high accuracy of less than 1.68% error.

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