Pulsed microwave Fourier transform spectrometer

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Abstract
A pulsed microwave Fourier transform spectrograph is described in detail. The increase in sensitivity and resolution obtained in the time domain relative to standard spectroscopy in the frequency domain is described theoretically and experimentally. Fast switching microwave diodes with a large dynamic range for the generation of high‐power microwave pulses are essential for the operation of the spectrograph. A 512‐point analog–digital converter and averager with a repetition rate of up to 30 kHz is used for signal‐to‐noise improvement. The observed emission signals in the time domain are Fourier transformed to the frequency domain on‐line by a small laboratory computer. The spectra obtained for 13CH2O and CD2O show a marked improvement in signal‐to‐noise ratio and resolution. A 50‐MHz bandwidth can be covered by a single pulse train.