Mitel Semiconductor Limited

Brendan P Fenney

Nicholas Mihailovits

David I Boddy

Trevor P Beatson

A frequency tracking arrangement in which a frequency tracking circuit utilizes a continuously variable analogue first order all-pass filter circuit as a controllable phase-shift element in a closed-loop system which produces a control signal to control the phase shift circuit to introduce a 90.degree. phase shift of a received reference frequency signal when the circuit is tracking that reference frequency. The control signal may then be utilized to slave the cut-off frequency of a filter and/or the delay time introduced by a delay line.

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Prestwich, United Kingdom

Brendan P Fenney