Capture Effect of FM (Frequency Modulation) Demodulators

摘要

The reception of FM carriers is characterized by a capture effect whereby the message of the dominant carrier is recovered when two or more FM carriers are present. This research uses a computer to form a type of average of the instantaneous frequency of the receiver input. The results establish that averaging (smoothing or lowpass filtering) of the instantaneous frequency reveals the capture effect. The effect on capture of bandwidth and amplitude ratio for the case of two carriers is revealed. The results show that capture can occur when two carriers are separated by as little as 0.17dB in amplitude. Thesis. (rh)