FM demodulator for a low IF receiver
First Claim
1. An apparatus for receiving an input signal and outputting a recovered modulated signal, the apparatus comprising:
- a. a superhet receiver for receiving the input signal and for outputting an in-phase signal and one or more phase shifted signals;
b. a plurality of monostables for receiving the in-phase signal and one or more phase shifted signals, each monostable producing an output pulse;
c. a summing circuit coupled to each of the monostable output pulses for combining the monostable output pulses into a composite waveform and outputting the composite waveform; and
d. a filtering circuit for receiving the composite waveform, recovering a modulated signal and outputting the modulated signal.
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Accused Products
Abstract
A superhet receiver with quadrature IF and improved demodulator is configured to recover a modulated signal from a low IF in a radio receiver. A superhet receiver receives a FM radio-frequency signal, converts the input RF signal to an in-phase IF signal and an IF signal in phase quadrature to the in-phase signal, and outputs the IF signals. A plurality of monostables receive the IF signals and each monostable generates a corresponding output pulse. By combining the monostable output pulses, a complex waveform is generated. The complex waveform includes the demodulated signal and a carrier signal at a significantly higher IF. The complex waveform is filtered to recover the desired modulated signal.
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Citations
43 Claims
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1. An apparatus for receiving an input signal and outputting a recovered modulated signal, the apparatus comprising:
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a. a superhet receiver for receiving the input signal and for outputting an in-phase signal and one or more phase shifted signals; b. a plurality of monostables for receiving the in-phase signal and one or more phase shifted signals, each monostable producing an output pulse; c. a summing circuit coupled to each of the monostable output pulses for combining the monostable output pulses into a composite waveform and outputting the composite waveform; and d. a filtering circuit for receiving the composite waveform, recovering a modulated signal and outputting the modulated signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of demodulating an FM signal using a superhet receiver and a demodulator, the method comprising the steps of:
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a. applying an input signal to a superhet receiver for generating an in-phase signal and one or more phase shifted signals; b. providing the in-phase signal and the one or more phase shifted signals to a plurality of monostables for generating a plurality of generated output pulses; c. summing the plurality of generated output pulses from each of the plurality of monostables in a summing circuit for forming a composite waveform; and d. filtering the composite waveform from the summing circuit in a filtering circuit for outputting a modulated signal therefrom. - View Dependent Claims (14, 15, 16)
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17. An apparatus for receiving an input signal and outputting a recovered modulated signal, the apparatus comprising:
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a. means for applying an input signal to a superhet receiver for generating an in-phase signal and one or more phase shifted signals; b. means for providing the in-phase signal and the one or more phase shifted signals to a plurality of monostables for generating a plurality of generated output pulses; c. means for summing the plurality of generated output pulses from each of the plurality of monostables in a summing circuit for forming a composite waveform; d. means for filtering the composite waveform from the summing circuit in a filtering circuit for outputting a modulated signal therefrom. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for receiving an input signal and outputting a recovered modulated signal, the apparatus comprising:
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a. a superhet receiver for receiving the input signal and for outputting an in-phase signal and one or more phase shifted signals; b. a plurality of monostables for receiving the superhet receiver output signals, the monostables configured into pairs whereby the number of monostable pairs is equal to the number of output signals from the superhet receiver, and each monostable producing an output pulse; c. a summing circuit coupled to each of the monostable output pulses for combining the monostable output pulses into a composite waveform and outputting the composite waveform; and d. a filtering circuit for receiving the composite waveform, recovering a modulated signal and outputting the modulated signal. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. An apparatus for receiving an input signal and outputting a recovered modulated signal, the apparatus comprising:
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a. a superhet receiver for receiving an input signal and for outputting an in-phase signal and a signal in phase-quadrature to the in-phase signal; b. a plurality of monostables for receiving the in-phase signal and the signal in phase-quadrature, the monostables configured into pairs wherein a first monostable pair receives the in-phase signal and a second monostable pair receives the signal in phase-quadrature, and further wherein each monostable produces an output pulse; c. a summing circuit coupled to each of the monostable output pulses for combining the monostable output pulses into a composite waveform and outputting the composite waveform; and d. a filtering circuit for receiving the composite waveform, recovering a modulated signal and outputting the modulated signal. - View Dependent Claims (40, 41, 42)
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43. A method of demodulating an FM signal using a superhet receiver and a demodulator, the method comprising the steps of:
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a. applying an input signal to the superhet receiver for generating an in-phase signal and a signal in phase-quadrature to the in-phase signal; b. providing the in-phase signal and the signal in phase-quadrature to a plurality of monostables, the monostables configured into pairs wherein a first monostable pair receives the in-phase signal and a second monostable pair receives the signal in phase-quadrature, and further wherein each monostable produces an output pulse; c. summing the plurality of generated output pulses from each of the plurality of monostables in a summing circuit for forming a composite waveform; and d. filtering the composite waveform from the summing circuit in a filtering circuit for outputting a modulated signal therefrom.
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Specification