Phase locked loop with improved lock-in
AssigneeMotorola, Inc.
InventorFrancis H. Hilbert
Life of this patent
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Abstract
The circuit determines whether an incoming frequency is within the normal "lock-in" range of a phase locked loop VCO or not, and whether it is higher or lower than the VCO frequency. If not within normal range, the beats are rectified and gated to provide a DC control voltage of the proper value and polarity for locking the oscillator on the incoming frequency. Rectification may be half or full wave as needed, and the circuit may include filter bandwidth control as well. This circuit is suitable for signals of any waveform, quadrature signals, and AM stereophonic signals.
Claims12
A phase locked loop comprising:
- input means;
- first, in-phase detector means coupled to the input means;
- second, quadrature detector means coupled to the input means;
- filter means coupled to the second detector means output;
- oscillator means coupled to be controlled by the filter means output, for providing two output signals in quadrature to the first and second detector means respectively;
- logic means coupled to the outputs of the first and second detector means for detecting beats between said output signals, for detecting the relative phase of said signals, and for providing a control signal in response to said detection;
- and
- gating means coupled to control the connection between the second detector means and the filter means in response to the control signal from the logic means.
A receiver for receiving AM stereophonic signals and comprising:
- input means;
- first, in-phase detector means coupled to the input means;
- second, quadrature detector means coupled to the input means;
- oscillator means coupled to provide two output signals in quadrature to the first and second detector means respectively;
- filter means coupled to the second detector means output and coupled to the oscillator means input;
- logic means coupled to the output of the first and second detector means for detecting beats between the output signals thereof, for detecting the relative phase of said output signals, and for providing a control signal in response to such detection;
- gating means coupled to control the connection between the second detector means and the filter means in response to the control signal from the logic means;
- correcting means coupled to correct the input signals of the first and second detector means;
- and
- means coupled to the correcting means and to the detector means for deriving the original stereo signals.
Dependencies are inferred from the claim text.