Title :
Triple modulation technique applicable to microwave spectrometers with cavity gas cell
Author :
Zhu, Z. ; Gibson, C. ; Samuel, A.H. ; Matthews, I.P.
Author_Institution :
Dept. of Epidemiology & Community Med., Univ. of Wales Coll. of Med., Cardiff, UK
fDate :
4/1/1993 12:00:00 AM
Abstract :
A triple modulation technique, applicable to microwave cavity spectrometers, is described, which enables Stark, Zeeman, double resonance or cavity modulation in the cavity gas cell to operate at a relatively low frequency, while satisfying the criterion that the microwave crystal detector should operate at a relatively high frequency. This technique is such that the microwave source is frequency double-modulated by means of a sweeping signal of frequency f 1 and a relatively high-frequency sinusoidal signal of frequency f2 applied to a tuning varactor, while an additional relatively low-frequency modulation such as Stark, Zeeman, double resonance or cavity modulation (frequency f3) is applied in the cavity gas cell. The low-frequency modulation signal ( f3), which contains the salient information of the analyte gas, is carried by the high-frequency signal f2 , the former being extracted and amplified by a series of filters, demodulators and tuned amplifiers
Keywords :
Stark effect; Zeeman effect; cavity resonators; microwave spectrometers; modulation; Stark modulation; Zeeman modulation; analyte gas; cavity gas cell; cavity modulation; double resonance modulation; high-frequency signal; low-frequency modulation; microwave crystal detector; microwave spectrometers; triple modulation technique; tuning varactor;
Journal_Title :
Microwaves, Antennas and Propagation, IEE Proceedings H
