Detectors for Quantitative MMW Spectrometry

The detector is the most important part of a MMW spectrometer. The photon energy at MMW frequencies is similar to kT (Equation 1.15) and so the noise naturally occurring in the semiconductor diode detectors is significant at these frequencies. The sources are spectrally bright and their close-in sideband noise 

Because the modulation frequency is so low, it is never necessary to carry out a full sideband analysis to interpret the results. Instead one may treat the low-frequency demodulated signal as arising from the Fourier components of the slowly varying response of the system to a tracked MMW source.  

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