Millimeter- and Submillimeter-Wave Spectrometers Based on the Direct Digital Synthesizers

Abstract

Two new fast scan spectrometers based on direct digital synthesizer frequency synthesis are presented. The spectrometers provide fast, to 100 GHz/hr, acquisition of molecular spectra keeping high-precision measurements of transition frequencies: for an isolated line, the error does not exceed ±0.002 MHz (provided that signal-tonoise ratio is more than 50). Source frequency modulation is also provided by means of direct digital synthesizers that allows to assure high stability and definiteness of parameters of frequency-modulated signal and minimize lineshape distortion of the spectral lines.