Pyroelectric Thermometer as a mm-Wave Detector

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  • Author: Jiri Polivka
I was curious whether the common PIR detectors used in alarm systems and low-cost IR thermometers might also be sensitive at mm-wave frequencies. Having a low-power sweep oscillator for 75-110 GHz on hand, I tested an alarm detector sensor, and yes, I observed a response of several mV, similar to my hand moving before the detector, when a 90-100 GHz signal with ~10 dBm was brought to the detector. However, the problem with alarm-type sensors is that they are quite sensitive to heat from surrounding objects, and the output voltage is low and unstable.