Technique of broadband measurements of frequency conversion efficiency foreach harmonique in frequency multipliers up to terahertz range

The paper describes technique of quantitative analysis of a millimeter-and submillimeter-wave range multipliers performance in particular the measurem ent of the frequency conversion efficiency. The output power on each harmon ic produced by the multiplier can be measured separately without any change s in the setup even in the case of simultaneous emission of all harmonics i ncluding the fundamental in a frequency range up to 1 THz and well above. The measuring technique primarily developed for high resolution microwave s pectroscopy is based on absorption of radiation in spectral lines of rarefi ed sample gas and photo - acoustic method of the absorption detection. Sens itivity independence of the detection method on frequency and well known sp ectral parameters of the lines provide the technique with broadbandness, hi gh spectral resolution and power measurement reliability. Principal limits of measurable radiation power may vary from nanoWatts up to hundreds of Wat ts. The technique permits real time operation convenient, e.g., for multipl ier tuning. Practical examples include measurements of harmonic generation efficiency of multipliers of 78-118 GHz fundamental frequency range, and po wer measurement up to 6-th harmonic of 230 GHz fundamental radiation of pha se locked Backward Wave Oscillator (BWO).