The Application of Negative Feedback to Frequency-Modulation Systems

摘要: Negative feedback can be applied to a frequency-modulation receiver of superheterodyne type by causing portion the output voltage frequency-modulate local oscillator in such phase as reduce signal. As consequence this arrangement effective frequency modulation intermediate wave is diminished factor. This reduction accompanied decrease noise and distortion. Restoration original signal level increasing degree at transmitter brings about corresponding increase signal-to-noise ratio provided disturbance not too great, while distortion ratios are improved same extent. These effects treated analytically for case where sufficiently low permit simplifying assumptions made. The results general agreement with observations made on an experimental laboratory system. Comparing system using amplitude limitation, absence identical two systems. During increases amount depending upon shift intermediate-frequency band width. By keeping small, during relatively unimportant. In cases high, phenomena have been observed which very similar those encountered when limitation used.