The present invention provides a DC offset compensating circuit 800 for FM IF orthogonal modulator zero in AMPS cellular mobile telephone system. The frequency offset is introduced in order to remove the DC component from the modulation-specific management audio tone and Manchester code in the modulated signal. A local oscillator 608, the frequency is mixed down to an intermediate frequency signal to zero some example operating at 5 kHz about a different frequency. DC offset is generated by the control loop to remove a fixed DC component caused by leakage from the local oscillator 608. After a given time, the control loop may be frozen, the frequency offset of the local oscillator 608 may be removed.
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