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Convention Paper

Ultra-High Performance Amplitude and Frequency Modulation and Demodulation

Authors: Talbot, Daniel B.

AES Convention 67 · Paper 1670 · October 1980

Abstract

Low distortion and high signal to noise ratio modulation and demodulation for both the AM and FM cases is possible, but several issues need to be recognized, among them: Filter characteristics, modulator and demodulator static and dynamic linearity, and topologies for modulators and/or demodulators. Approaches will be outlined which have resulted in successful achievement of distortion levels under 0.1% for AM and under 0.02% for FM, with signal to noise ratios of 80 to 90 decibels for AM and 70 to 80 decibels for FM. Better signal to noise ratios may be obtained at the sacrifice of distortion level. Distortion in amplitude modulators and demodulators is shown to be increased by processing passband amplitude asymmetry, and in frequency modulators and demodulators, by nonlinear phase response, as well as by modulator and demodulator amplitude distortion. A DFT (discrete Fourier Transform) approach is shown which can analyze the low-frequency theoretical distortion, and an example is given using the FM quadrature detector.

Details

Published in
AES Convention 67
AES Convention
67
Paper number
1670
Publication date
October 6, 1980
Affiliation
LTX Corporation, Newton Highlands, MA (See document for exact affiliation information.)
Type
Convention Paper