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A frequency‐locked adaptive filter
Author(s) -
Bruton L. T.,
Pederson R. T.
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.4490010109
Subject(s) - voltage controlled filter , all pass filter , low pass filter , high pass filter , control theory (sociology) , filter design , filter (signal processing) , active filter , butterworth filter , adaptive filter , band stop filter , root raised cosine filter , kernel adaptive filter , electronic filter topology , m derived filter , computer science , electronic engineering , engineering , voltage , control (management) , electrical engineering , artificial intelligence , computer vision
A frequency‐locked RC active ladder filter is described, which is frequency‐locked to a sinusoidal control tone. The tunable ladder filter is used as a frequency discriminator by using two of the filter branch voltages to generate a control voltage. The control voltage is then used to tune or frequency‐scale the ladder filter transfer function to lock the filter to the frequency of the control tone. A simple linear frequency‐signal control system is developed to describe the frequency‐locked performance of the adaptive filter. The frequency‐locked filter can be designed so that the sinusoidal control tone is rejected at the filter output, making it possible to adapt the filter transfer function during transmission of a message. A practical frequency‐locked filter is given in which a frequency‐locked third order elliptic lowpass filter is designed. The performance of the practical filter is analysed using a simple linear control system model.