11 CLAIMS

• 1. In a system including a source of composite signal having a reference component and an information modulated component, a demodulator for recovering the modulated information, comprising:
• phase detector means having reference input means and oscillator input means for generating at an output a control signal having a value dependent on the phase difference between signals at said input means;
• coupling means connected to said source for coupling said reference component to said reference input means of said phase detector;
• controlled oscillator means for generating an oscillatory signal having a frequency a multiple of the frequency of said reference component, the value of the control signal output of said phase detector means controlling the phase of said oscillatory signal;
• divider means for frequency dividing said oscillatory signal to produce a divided signal and an insertion signal;
• loop means connected to said divider means for coupling said divided signal to the oscillator input means of said phase detector means to produce a phase locked loop including said phase detector means, said controlled oscillator means, and said divider means; and
• detector means having inputs coupled to said source and said divider means for demodulation of said information modulated component by use of said
• 2. The demodulator of claim 1 wherein said information modulated component comprises a suppressed carrier signal and said reference component comprises a pilot signal having a pilot frequency a fraction of the frequency of said suppressed carrier, said divider means comprises a plurality of divider stages with said divided signal being produced by the last divider stage and said insertion signal being produced by a divider
• 3. The demodulator of claim 2 wherein said pilot frequency is one-half the frequency of said suppressed carrier, said controlled oscillator means generating said oscillatory signal at a frequency which is a power of two multiple of the frequency of said suppressed carrier, said divider stages each consisting of a divide-by-two means with said insertion signal being
• 4. The demodulator of claim 3 wherein said controlled oscillator means generates the oscillatory signal at twice the frequency of said suppressed carrier, said divider means comprises two binary divide-by-two means with said insertion signal being produced at one-half the frequency of the oscillatory signal by the first binary means and said divided signal being produced at one-fourth the frequency of the oscillatory signal by said
• 5. The demodulator of claim 2 wherein said controlled oscillator means generates an asymmetrical waveform forming said oscillatory signal, and said insertion signal comprises a symmetrical waveform for synchronous demodulation of said suppressed carrier modulated signal in said detector
• 6. The demodulator of claim 1 wherein said coupling means includes a high pass filter for passing frequencies corresponding to the frequency of the reference component, said high pass filter being formed of passive
• 7. The demodulator of claim 6 wherein said high pass filter comprises an RC network including capacitor means in series between said source and said one reference input means of said phase detector, and resistive means for
• 8. The demodulator of claim 1 including monitor means coupled to said source for detecting the presence of said reference component in the
• 9. The demodulator of claim 8 wherein said monitor means includes a second phase detector means for generating at an output a signal indicating the presence of said reference component when a pair of inputs have one input coupled to said composite signal and the other input coupled to a local reference component in phase with the reference component of said composite signal, EXCLUSIVE OR means having an output coupled to said other input and a pair of inputs, and gate input means coupling said pair
• 10. The demodulator of claim 9 wherein said divider means comprises a plurality of frequency divider stages in cascade, said gate input means coupling said pair of inputs to different divider stages to cause said EXCLUSIVE OR means to produce said local reference component with a 90° phase shift without ambiguity from a signal produced by the
• 11. The demodulator of claim 9 wherein said monitor means includes low pass filter means coupled to said output of said second phase detector means to produce a DC signal proportional to the magnitude level of the reference component.