phase lock loop design using 74hc4046

[f1kr1]

phase lock loop design.

im designing a phase locked loop as a FM demodulator using 74hc4046.
Can anyone explain to me what expected output at the output of phase detector and VCO. The output signal that I get from VCO is exacly the same as the input signal.
but oscilloscope show nothing at the output of the phase detector.
can anyone tell what might be the problem.

 

[ismailhussain22]

Re: phase lock loop design.

The output of the phase detector will be D.C (voltage or current).. which is propotional to the phase error between the input and output.. this controls the frequency of VCO.. After sometime the freq of VCO will be equal to the Freq of input signal and hence both are similar and if Phase is equal then phase detector output is zero..