FM demodulator using injection locked oscillator having tuning feedback and linearizing feedback
First Claim
1. A demodulator circuit, comprising:
- an injection locked oscillator having a first input coupled for receiving an input signal, and an output;
a phase detector circuit having first and second inputs respectively coupled to the first input and output of the injection locked oscillator, and an output for providing an output signal;
a linearizing feedback circuit having an input coupled to the output of the phase detector circuit and an output which serves as an output of the demodulator circuit;
a tuning feedback circuit having an input coupled to the output of the linearizing feedback and an output; and
a summing circuit having first and second inputs and an output, the first input coupled to the output of the tuning feedback circuit, the second input coupled to the output of the linearizing feedback circuit and the output coupled to a second input of the injection locked oscillator.
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Abstract
A demodulator circuit (100) and method for producing a demodulated signal VOUT from an input signal VIN. A frequency detection circuit (101) produces a quadrature signal VQUAD which is compared to the input signal VIN to produce a detected output signal. The phase and frequency of the quadrature signal VQUAD are responsive to a control signal ICONTROL. The demodulator circuit (100) has an output terminal (114) which provides the demodulated signal VOUT. Nonlinearity in the demodulated output signal VOUT in relation to a modulating signal is reduced by a linearizing feedback circuit (102). Automatic tuning is provided by a tuning feedback circuit (103). The output signals produced at the respective output terminals (114) and (113) of the linearizing feedback circuit (102) and tuning feedback circuit (103) are summed to produce the control current ICONTROL.
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Citations
11 Claims
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1. A demodulator circuit, comprising:
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an injection locked oscillator having a first input coupled for receiving an input signal, and an output; a phase detector circuit having first and second inputs respectively coupled to the first input and output of the injection locked oscillator, and an output for providing an output signal; a linearizing feedback circuit having an input coupled to the output of the phase detector circuit and an output which serves as an output of the demodulator circuit; a tuning feedback circuit having an input coupled to the output of the linearizing feedback and an output; and a summing circuit having first and second inputs and an output, the first input coupled to the output of the tuning feedback circuit, the second input coupled to the output of the linearizing feedback circuit and the output coupled to a second input of the injection locked oscillator. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An integrated FM demodulator circuit having an input and an output, the input responsive to an input signal and the output providing an output signal, comprising:
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an injection locked oscillator having first and second inputs and an output, the first input responsive to the input signal, the second input responsive to a control signal and the output providing a quadrature signal; a phase detector circuit having first and second inputs and an output, the first input serving as the input of the integrated FM demodulator circuit, the second input responsive to the quadrature signal and the output providing a detection signal; an amplifier drcuit having an input and an output, the input responsive to the detection signal and the output serving as the output of the integrated FM demodulator circuit; a tuning circuit having an input and an output, the input responsive to the detection signal and the output providing a tuning correction signal; and a summing circuit having first and second inputs and an output, the first input responsive to the output signal of the integrated FM demodulator circuit, the second input responsive to the tuning correction signal and the output providing the control signal. - View Dependent Claims (8, 9, 10, 11)
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Specification