As the phase changes, the DC voltage level moves up and down and re-creates the
audio signal.
A low pass filter is included to reduce the amplitude of any high-frequency ripple
and also blocks the DC offset. Consequently, the signal at the output closely
resembles the original input signal.
The characteristic as shown in Figure 105 is straight enough to cause very little
distortion to the final audio output.
Amplitude
Audio
Output
Signal
Frequency
Figure ก05 Quadrature Defector Characteristic
8.Sa A decrease in the output voltage of a Quadrature Detector is most likely
to be the result of:
the frequency modulated signal increasing in amplitude.
an increase in the frequency of the FM input signal.
a phase shift of less than 900 at the output of the phase shifting circuit.