Detection of Asymmetric Sideband Signals in the Presence of Noise

The first part of this paper analyzes three methods of detection of signals contaminated by fluctuation noise: (1) Linear Envelope Detectors (2) Product Detectors (3) Exalted Carrier Detectors. A new ratio, the ``video-to-noise-error ratio'' is proposed for a more adequate quantitative evaluation of detector performance. Its use is justified by a large number of theoretical curves and experimental results. The theoretical and practical results show that an improvement in the output video-to-noise-error ratio is obtained by substitution of a product detector for an envelope detector. Improvements of 11 decibels have been measured. The second part of this paper analyzes the effects of impulse noise on the detection of asymmetric sideband signals. It is shown that product detectors eliminate the rectification of the noise envelope found in envelope detectors. This is of particular interest in asymmetric sideband systems where the noise output will be at relatively high frequencies. These can often be separated from lower frequency signals, making possible efficient impulse noise suppression.