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Designing The Closed Loop Self-excited/Detection Circuit And Performance Testing For Resonant Infrared Detectors

Posted on:2015-09-09Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiFull Text:PDF
GTID:2298330431989227Subject:Detection Technology and Automation
Abstract/Summary:PDF Full Text Request
The output signal of micro-resonant infrared detectors is frequency signaland has strong anti-interference ability. This kind of infrared detectors can measureinfrared radiation at room temperature, thus causing attention and researches of someworkers. It is necessary to develop closed loop self-excited/detection circuit toimprove the apparent quality factor of resonantor, the accuracy and speed ofmeasurement because that the output signal of resonantor is weak, having seriouscrosstalk interference and low signal to noise ratio. Thus the circuit can track theresonant frequency change to achieve real-time dynamic measurement of infraredradiation. It is an important content in the micro-resonant infrared detecting field.Then, the closed loop self-excited/detection circuit of the resonantor with themicro-bridge structure based on precise frequency selective characteristics of PLL(phase-locked loop) was developed by repeatedly modified work. The circuitcomprised a low-noise amplifier, fourth order Butterworth liner band-pass filters, a-180o~180o phase shifter, a sine wave-square wave transducer, a frequency divider,the PLL which can track the changing frequency without phase difference, anamplitude adjustment and so on. The designed and optimized Butterworth band-passfilter with maximum flat and approximate linear feature in band-pass, improved thestability of the closed loop circuit. The designed shifter with the shift phase rangefrom-180o~180o expanded the scope of phase shift. Through the reasonablecomponent parameters selection of one order loop filters in the PLL module,frequency tracking without phase difference was achieved.The output frequency signal of closed-loop self-excited/detection circuit wastransmitted to the interface in computer programming with Labview through theFPGA frequency acquisition system. The order of the relative frequency error was10-6, meeting the requirements in the aspects of frequency accuracy.Finally, through the infrared light source driving circuit modulating the cycleand duty cycle of JSIR350-22-R infrared thin film infrared radiation, the infrareddetection performance testing on the detector was realized. And the responsivity of uncooled infrared detector based on micro-bridge resonantor can reach-12.02ppm/uW.
Keywords/Search Tags:infrared detector, Closed Loop Self-excited System, linear filter, PhaseLock Loop
PDF Full Text Request
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