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Synthesis of a nonlinear filter for fm demodulation
Author(s) -
Mullick S. K.
Publication year - 1973
Publication title -
international journal of circuit theory and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.364
H-Index - 52
eISSN - 1097-007X
pISSN - 0098-9886
DOI - 10.1002/cta.4490010202
Subject(s) - demodulation , control theory (sociology) , frequency modulation , amplitude modulation , phase locked loop , analog transmission , instantaneous phase , amplitude , bandwidth (computing) , low pass filter , modulation (music) , signal (programming language) , phase detector , nonlinear system , phase (matter) , filter (signal processing) , electronic engineering , acoustics , computer science , physics , analog signal , engineering , optics , digital signal processing , telecommunications , electrical engineering , channel (broadcasting) , voltage , artificial intelligence , control (management) , quantum mechanics , programming language , computer vision
The well‐known techniques of the so‐called high sensitivity FM demodulation namely the frequency feedback (FMFB) and the phase locked loop (PLL) systems can be considered as variations of FM detection system using tracking filters. The fact that FM signals can be demodulated by such systems shows that the energy of the FM wave is concentrated in a narrow band around the instantaneous frequency. The purpose of this paper is to show that such a system configuration for FM detection arises naturally from the phase‐plane study of the forced behaviour of a quasi‐linear second‐order differential equation to narrow band signals bearing amplitude and/or phase modulation. A nonlinear filter is synthesized which is designed to offer wide bandwidth to phase modulation vis‐a‐vis amplitude modulation. The filtering scheme is simulated on the digital computer and the desired behaviour verified by observing the response to a step change in phase and amplitude of the input sinusoidal signal.