Method and apparatus for automatic fine tuning based on sync detection
The method according to the invention for adjusting the tuning of a receiver circuit for receiving modulated a high frequency signal within a frequency range, the high frequency signal comprising a sync signal, uses the steps of shifting a frequency of a local oscillator within the frequency range and looking for the sync signal, and storing the value of a first frequency, when a sync signal is recognized. Then, the frequency of the local oscillator is continuously shifted in the same frequency direction across the bandwidth of the modulated high frequency signal by controlling the presence of the sync signal. The frequency, at which the sync signal is lost, is stored as a second frequency. From the first and the second frequency in a further step an optimum tuning frequency, located between the first and second frequency, is calculated for the reception for the high frequency signal. The receiver circuit comprises in particular a sync signal detector coupled to an output of an intermediate frequency filter and a controller circuit coupled to the sync signal detector and a local oscillator for performing the method.
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Hong Chiew Mun
Li Chang