In a system that demodulates a frequency modulated signal using a
quadrature detector circuit, an apparatus that tunes the output signal to
compensate for any offset in the signal includes an offset adjustment
circuit and a control circuit. The offset adjustment circuit is operably
coupled to the control circuit which may consist of a DAC and a digital
logic such as a computer CPU. The control circuit determines a correction
signal in response to a sequence of sampled of the system output, and
supplies the correction signal to the offset adjustment circuit. The
offset adjustment circuit provides an offset correction signal in response
to the correction signal, and combines the offset correction signal with
the output of the quadrature detector to provide an offset adjusted signal
at an output node.
