Accession Number:

AD0425666

Title:

THE DETECTION OF SMALL MODULATIONS,

Descriptive Note:

Corporate Author:

GEORGIA INST OF TECH ATLANTA ENGINEERING EXPERIMENT STATION

Report Date:

1963-11-13

Pagination or Media Count:

47.0

Abstract:

The behavior of sideband signals and noise in the demodulation of a double-sideband modulated carrier is discussed and related to conventional mixing processes. The characteristics of diode demdulator conversion loss and excess noise are consicered as a function of carrier power level and modulation frequency. Experimental data were taken on thermionic diodes, semiconductor pointcontact diodes and semiconductor junction diodes at a carrier frequency of 146 mc between power levels of 0.1 and 600 mw and for modulation frequencies between 100 cps and 10,000 cps. The results show that demodulators are available for use in the UHF region with minimum detectable modulation index in the range of -170 to -180 db in 1-cps bandwidth in the lw audio modulation spectrum. Recommendations are made of ways to construct demodulators to handle higher carrier power to better these figures. It is demonstrated that a r-f generator can be constructed with amplitude noise sideband level equal to the minimum detectable noise of the best available detector. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE