| Summary: | 碩士 === 國立中正大學 === 電機工程所 === 97 === A remote wireless vital signal detection system along with a static and dynamic clutter cancellation technique is investigated and designed in this thesis. By utilizing Doppler theory, the system transmits a continuous wave (CW) signal to a tested subject. The signal is phase modulated by the chest vibration caused by respirations and heartbeats and reflected back to the system. Finally, the desired cardiopulmonary signal is demodulated and obtained by the system. However, the system sensitivity will be deteriorated by environmental clutter and the self leakage of the transmitted signal due to the imperfection of isolation of the circuitries. Hence, the detection range is limited. Moreover, the tested environment is usually in a chaotic state and the surrounding clutter is often time-varying. Therefore, the key to achieve the long-range detection is to effectively cancel out the unwanted static as well as dynamic surrounding clutter.
In this thesis, a novel static and dynamic clutter cancellation algorithm is proposed to extend the detection range. First of all, the MONTE CARLO simulation is utilized to analyze and specify the sub-circuits. A LabVIEW control program is developed to precisely control attenuator and phase shifter to cancel out the unwanted clutter. After the technique is applied into the system, the system isolation can be enhanced up to -90 dB. Measured results reveal that rates of respiration and heartbeat can be successfully detected from a 7 m distance with -5 dBm output power for static environment. Also, clear real-time waveforms can be observed under detection range is less than 4 m, hence the real-time display capability can be obtained. Furthermore, the system has restorable capability which can quickly update and cancel out the time-varying clutter within 35 ms when a motion subject is present in the environment.
Hopefully, this technique could play an important role in many remote biomedical applications, such as home care and earthquake rescue, etc..
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