3971988 :
AM/FM receiver using spectral parameter estimators
11 CLAIMS
What is claimed is:
 1. A receiver for producing signals corresponding to the modulating signals of applied frequency modulated and amplitude modulated radio frequency signals comprising:
 radio frequency amplification means comprising:
 an input connected to said antenna;
 means for generating a signal at said output terminal corresponding to a signal present at said input amplified by a predefined factor; and
 a demodulation circuit comprising:
 an output connected to said demodulation circuit output; and
 means for selectively connecting one of said first, second, and third inputs of said switch means to said switch means output; and
 demodulation means for generating: at said switch means first input a signal corresponding to the instantaneous amplitude of an input signal applied to said receiver antenna utilizing: a first circuit for generating a first signal corresponding to the instantaneous power of said applied signal, a circuit for generating a signal corresponding to the square root of said first signal, and a first integrator circuit for integrating said square root signal, said integrated square root signal being applied to said switch means first input; at said switch means second input a signal corresponding to the instantaneous frequency of an input signal applied to said receiver antenna utilizing: said first circuit and a second circuit for generating signals corresponding respectively to the instantaneous power and instantaneous power frequency product of said applied signal, a divider circuit for providing a signal corresponding to the ratio of said instantaneous power frequency product signal to said instantaneous power signal, and a second integrator circuit for integrating said ratio signal, said integrated ratio signal being applied to said switch means second input; and at said switch means third input a signall corresponding to an estimate of the power mean frequency of said applied signal utilizing: said first and second circuits for generating said instantaneous power and said instantaneous power frequency product signals, said first and second integrator circuits for integrating said instantaneous power and said instantaneous power frequency product signals and a divider circuit for providing said estimate of said power mean frequency signal corresponding to the ratio of said integrated power frequency product signal to said integrated instantaneous power signal, said estimate of said power means frequency signal being applied to said switch means third input.
 2. A receiver for producing signals corresponding to the modulating signals of applied frequency modulated radio frequency signals comprising:
 radio frequency amplification means comprising:
 an input connected to said antenna;
 means for generating a signal at said last mentioned output terminal corresponding to a signaal present at said input amplified by a predefined factor; and
 a demodulation circuit comprising:
 and means for generating at said demodulation circuit output a signal corresponding to an estimate of the power mean frequency of said applied signal utilizing: a circuit for generating a signal corresponding to the instantaneous power of said applied signal and a circuit for generating a signal corresponding to the instantaneous power frequency product of said applied signal, first and second integrator circuits for integrating said instantaneous power and said instantaneous power frequency product signals and a diviider circuit for providing said estimate of said power mean frequency signal corresponding to the ratio of said integrated power frequency product signal to said integrated instantaneous power signal.
 3. A receiver for producing signals corresponding to the modulating signals of applied frequency modulated radio frequency signals comprising:
 radio frequency amplification means comprising:
 an input connected to said antenna;
 means for generating a signal at said last mentioned output terminal corresponding to a signal present at said input amplified by a predefined factor; and
 a demodulation circuit comprising:
 and means for generating at said demodulation circuit output a signal corresponding to the instantaneous frequency of an input signal applied to said receiver antenna utilizing: first and second circuits for generating signals corresponding respectively to the instantaneous power and instantaneous power frequency product of said applied signal, a divider circuit for providing a signal corresponding to the ratio of said instantaneous power frequency product signal to said instantaneous power signal, and an integrator circuit for integrating said ratio signal.
 4. A receiver for producing signals corresponding to the modulating signals of applied amplitude modulated radio frequency signals comprising:
 radio frequency amplification means comprising:
 an input connected to said antenna;
 means for generating a signal at said last mentioned output terminal corresponding to a signal present at said input amplified by a predefined factor; and
 a demodulation circuit comprising:
 and means for generating at said demodulation circuit output a signal corresponding to the instantaneous power of an input signal applied to said receiver antenna utilizing: a circuit for generating a first signal corresponding to the instantaneous power of said applied signal, a circuit for generating a signal corresponding to the square root of said first signal, and an integrator circuit for integrating said square root signal.
 5. A spectral parameter estimator for use as a demodulator comprising:
 a spectral parameter estimator input terminal for receiving an input signal;
 a spectral parameter estimator output terminal;
 a reference signal generator comprising:
 means for generating signals at said first and second outputs corresponding to the Sine and Cosine, respectively, of a reference signal frequency times a time factor;
 a first mixer comprising:
 a first input connected to said input terminal;
 a second input connected to said first output of said reference signal generator;
 means for generating an output signal corresponding to the Sine of the difference between said input signal frequency and said reference signal frequency plus the Sine of the sum of said input signal frequency and said reference signal frequency;
 a first low pass filter comprising:
 an input connected to said output of said first mixer;
 means for generating on said output a signal corresponding to the Sine of said input signal frequency minus said reference signal frequency;
 a second mixer comprising:
 a first input connected to said input terminal;
 a second input connected to said second output of said reference signal generator;
 means for generating an output signal corresponding to the Cosine of the difference between said input signal frequency and said reference signal frequency plus the Cosine of the sum of said input signal frequency and said reference signal frequency;
 a second low pass filter comprising:
 an input connected to said output of said second mixer;
 means for generating on said output a signal corresponding to the Cosine of said input signal frequency minus said reference signal frequency;
 a first differentiator circuit comprising:
 an input connected to said output of said first low pass filter circuit;
 means for generating an output signal corresponding to the derivative of the signal applied to said input of said first differentiator circuit;
 a second differentiator circuit comprising:
 an input connected to said output of said second low pass filter circuit;
 means for generating an output signal corresponding to the derivative of the signal applied to said input of said second differentiator circuit;
 a power circuit comprising:
 first and second inputs connected respectively to said first low pass filter circuit and said second low pass filter circuit;
 means for generating an output signal corresponding to the power of an input signal applied to said spectral parameter estimator input terminal;
 a signal translating circuit comprising:
 inputs connected to said outputs of said first and second low pass filter circuits, said first and second differentiator circuits, and said power circuit;
 an output connected to said spectral parameter estimator output terminal; and
 means for generating a signal at said output corresponding to the demodulated audio component of an input signal applied to said spectral parameter estimator input as represented by said inputs to said signl translating circuit.
 6. A spectral parameter estimator according to claim 5 wherein said signal translating circuit further comprises:
 a power frequency product circuit comprising:
 inputs connected to said outputs of said first and second low pass filter circuits and said first and second differentiator circuits;
 means for generating an output signal corresponding to the product of the power of said input signal and the difference between said input signal frequency and said reference signal frequency;
 a first integrator comprising:
 an input connected to said output of said power frequency product circuit;
 means for generating an output signal corresponding to the average power frequency product of said input signal and said reference signal over a predetermined period of time;
 a second integrator circuit comprising:
 an input connected to said output of said power circuit;
 means for generating an output signal corresponding to the average power of said input signal;
 a divider circuit comprising:
 a dividend input connected to said output of said first integrator;
 a divisor input connected to said output of said second integrator;
 an output connected to said output terminal; and
 means for generating an output signal corresponding to the power mean frequency of said input signal.
 7. A spectral parameter estimator according to claim 5 wherein said signal translating circuit further comprises:
 a power frequency product circuit comprising:
 inputs connected to said outputs of said first and second low pass filter circuits and said first and second differentiator circuits;
 means for generating an output signal corresponding to the product of the power of said input signal and the difference between said input signal frequency and said reference signal frequency;
 a divider circuit comprising:
 a dividend input connected to said output of said power frequency product circuit;
 a divisor input connected to said output of said power circuit;
 means for generating an output signal corresponding to the instantaneous frequency of said input signal;
 an integrator circuit comprising:
 an input connected to said output of said divider circuit;
 an output connected to said output terminal; and
 means for generating an output signal corresponding to the average instantaneous frequency over a predetermined period of time.
 8. A spectral parameter estimator according to claim 5 wherein said signal translating circuit further comprises:
 a square root circuit comprising:
 an input connected to said output of said power circuit;
 means for generating an output signal corresponding to the mathematical square root of the nmber represented by said input signal;
 an integrator circuit comprising:
 an input connected to said output of said square root circuit;
 an output connected to said output terminal; and
 means for generating an output signal corresponding to the average amplitude of said input signal over a predetermined period of time.
 9. A spectral parameter estimator according to claim 5 further comprising:
 a splitter circuit connected between said input terminal and said first mixer circuit and said second mixer circuit comprising:
 an input connected to said input terminal;
 means for generating at said first and said second outputs signals corresponding to signals present on said splitter circuit input.
 10. A spectral parameter estimator according to claim 6 further comprising:
 a first phase compensation circuit connected between said first low pass filter output and said power circuit comprising:
 an input connected to said output of said first low pass filter;
 an output connected to an input of said power circuit; and
 means for generating a signal at said first phase compensation circuit output corresponding to the signal present at said first phase compensation circuit input phase shifted whereby said output of said first differentiator and said output of said first phase compensation circuit have a substantially constant phase relationship over a certain range of frequencies; and
 a second phase compensation circuit connected between said second low pass filter output and said power circuit comprising:
 an input connected to said output of said second low pass filter;
 an output connected to an input of said power circuit; and
 means for generating a signal at said second phase compensation circuit output corresponding to the signal present at said second phase compensation circuit input phase shifted whereby said output of said second differentiator and said output of said second phase compensation circuit input phase shifted whereby said output of said second differentiator and said output of said second phase compensation circuit have a substantially constant phase relationship over a certain range of frequencies.
 11. A spectral parameter estimator according to claim 5 wherein said signal translating circuit further comprises:
 an integrator circuit comprising:
 an input connected to said output of said power circuit;
 means for generating an output signal corresponding to the time average of a signal present at said integrator input;
 a square root circuit comprising:
 an input connected to said output of said integrator circuit;
 means for generating an output signal corresponding to the mathematical square root of the number represented by the signal present at said square root circuit input;
 a low pass filter circuit comprising:
 an input connected to said output of said square root circuit;
 an output connected to said output terminal; and
 means for generating an output signal corresponding to certain low frequency components of the signal present on said low pass filter input.
