Linear phase demodulator including a phase locked loop with auxiliary feedback loop
First Claim
1. Apparatus for demodulating a phase modulated wave comprising a phase locked loop responsive to the phase modulated wave, said loop including:
- a voltage controlled oscillator, a phase detector responsive to the oscillator and the phase modulated wave for deriving an A.C. data output signal having a magnitude indicative of the phase of the phase modulated wave and a phase indicative of the phase of the modulated wave and for deriving an error signal indicative of the phase deviation between an input carrier wave component of the phase modulated wave and the voltage controlled oscillator, and a loop filter responsive to the error signal for deriving a control signal for the oscillator, means for controlling the oscillator phase in proportion to an integral of the error signal; and
a feedback loop responsive to the data output signal for increasing the power of the carrier frequency component in the phase locked loop.
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Abstract
A phase modulated wave that may have no carrier power is demodulated by a phase locked loop including a phase detector for deriving an A.C. data output signal having a magnitude and a phase indicative of the phase of the modulated wave. A feedback loop responsive to the data output signal restores power to the carrier frequency component to the loop. In one embodiment, the feedback loop includes a phase modulator responsive to the phase modulated wave and the data output signal. In a second embodiment, carrier frequency power is restored by differentiating the data output signal and supplying the differentiated signal to an input of a voltage controlled oscillator included in the phase locked loop. Preferably, the phase modulator is linear and includes a series inductance-capacitance network, wherein the capacitor is a voltage controlled varactor. To compensate for nonlinearities in the varactor reactance vs. voltage characteristic, the series circuit is shunted by a properly selected inductance.
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Citations
11 Claims
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1. Apparatus for demodulating a phase modulated wave comprising a phase locked loop responsive to the phase modulated wave, said loop including:
- a voltage controlled oscillator, a phase detector responsive to the oscillator and the phase modulated wave for deriving an A.C. data output signal having a magnitude indicative of the phase of the phase modulated wave and a phase indicative of the phase of the modulated wave and for deriving an error signal indicative of the phase deviation between an input carrier wave component of the phase modulated wave and the voltage controlled oscillator, and a loop filter responsive to the error signal for deriving a control signal for the oscillator, means for controlling the oscillator phase in proportion to an integral of the error signal; and
a feedback loop responsive to the data output signal for increasing the power of the carrier frequency component in the phase locked loop. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- a voltage controlled oscillator, a phase detector responsive to the oscillator and the phase modulated wave for deriving an A.C. data output signal having a magnitude indicative of the phase of the phase modulated wave and a phase indicative of the phase of the modulated wave and for deriving an error signal indicative of the phase deviation between an input carrier wave component of the phase modulated wave and the voltage controlled oscillator, and a loop filter responsive to the error signal for deriving a control signal for the oscillator, means for controlling the oscillator phase in proportion to an integral of the error signal; and
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9. A circuit for linearly phase modulating an r.f. input in response to a modulation input signal comprising a parallel substantially all reactive network including:
- a variable reactance of a first type connected in series circuit with a first reactance of a second type opposite from the first type, the value of the variable reactance being controlled by the modulation input signal amplitude such that the reactance value is a non-linear function of the modulation input signal amplitude while the series circuit is approximately at resonance, a second reactance of the second type shunting the series circuit, said first and second reactances having values such that the series circuit has a reactance of the first type that is approximately in parallel resonance with the second reactance to provide compensation for the non-linear relationship between the value of the variable reactance and the modulation input signal; and
means for coupling energy from the r.f. input to the parallel circuit and for coupling reflected r.f. energy from the parallel circuit to a load without coupling any substantial r.f. energy back to the r.f. input. - View Dependent Claims (10, 11)
- a variable reactance of a first type connected in series circuit with a first reactance of a second type opposite from the first type, the value of the variable reactance being controlled by the modulation input signal amplitude such that the reactance value is a non-linear function of the modulation input signal amplitude while the series circuit is approximately at resonance, a second reactance of the second type shunting the series circuit, said first and second reactances having values such that the series circuit has a reactance of the first type that is approximately in parallel resonance with the second reactance to provide compensation for the non-linear relationship between the value of the variable reactance and the modulation input signal; and
Specification