US3609555A
Expired / Lapsed
US
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Digital fm receiver
Assignee: International Business Machines Corp
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Filing: 1967-07-19
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Granted: 1971-09-28
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Expires: 1987-07-19
Abstract
Abstract A digital FM receiver for receiving information in the form of analog signals on a frequency-modulated carrier at its input and providing said information in digital form at its output. The input signal consisting of a subcarrier modulated by the analog information (baseband) is converted into digital form in an analog to digital converter and is then demodulated in a digital demodulator, providing at its output the baseband information in digital form. The invention herein described was made in the course of or under a contract with the United States Air Force.
Inventors
- 👤 Richard Van Blerkom
- 👤 Don G Freeman
- 👤 Richard C Crutchfield
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 05:53
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
91 words
An apparatus for demodulating a frequency-modulated analog input signal, said signal including a subcarrier that is frequency modulated by an analog baseband signal, comprising: a converter for sampling said analog input signal at a known rate, said converter providing one digital number at its output for each sample, said digital number representing the analog amplitude of the input signal at the sample time; and digital-demodulating means responsive to the digital numbers for demodulating the analog baseband information from the subcarrier to provide a digital output representative of the baseband modulation frequency.
Claim 2
Independent Claim
91 words
An apparatus for demodulating a frequency-modulated analog input signal, said signal including a subcarrier that is frequency modulated by an analog baseband signal, comprising: a converter for sampling said analog input signal at a known rate, said converter providing one digital number at its output for each sample, said digital number representing the analog amplitude of the input signal at the sample time; and digital-demodulating means responsive to the digital numbers for demodulating the analog baseband information from the subcarrier to provide a digital output representative of the baseband modulation frequency.
Claim 3
Dependent Claim
114 words
An apparatus as in claim 1 wherein the digital-demodulating means comprises: a differentiating circuit responsive to the digital numbers for providing a digital derivative of the digital numbers; a dividing circuit responsive to the digital numbers and to the digital derivative of the digital numbers for dividing the digital derivative of the digital numbers by the digital numbers; and a root circuit responsive to the output of the dividing circuit for providing a digital root of the output of the dividing circuit, the degree of said root being equal to the order of the derivative provided by the differentiating circuit, whereby the output of the root circuit is the baseband information in digital form.
Claim 4
Independent Claim
74 words
An apparatus for demodulating a frequency modulated analog signal comprising: a source of frequency-modulated analog signals, said signals having a subcarrier wave modulated by analog baseband information; converter means for obtaining digital numbers representative of the analog amplitude of the frequency-modulated signal; an demodulating means for receiving the digital numbers and for demodulating the analog baseband information from the subcarrier to provide an output which is a digital representation of the baseband modulation frequency.
Claim 5
Independent Claim
74 words
An apparatus for demodulating a frequency modulated analog signal comprising: a source of frequency-modulated analog signals, said signals having a subcarrier wave modulated by analog baseband information; converter means for obtaining digital numbers representative of the analog amplitude of the frequency-modulated signal; an demodulating means for receiving the digital numbers and for demodulating the analog baseband information from the subcarrier to provide an output which is a digital representation of the baseband modulation frequency.
Claim 6
Independent Claim
106 words
An apparatus for demodulating a frequency modulated analog signal comprising: means for receiving an analog signal, said signal comprising a carrier wave modulated by a subcarrier wave, the subcarrier wave being frequency-modulated by analog baseband information; mixer means, responsive to the analog signal, for demodulating the modulated subcarrier wave from the carrier wave; converter means responsive to the output of said mixer means for providing digital numbers representative of the amplitude of the modulated subcarrier wave; and demodulating means for receiving the digital numbers and for demodulating the analog baseband information from the subcarrier wave to provide a digital output representative of the baseband modulation frequency.
Claim 7
Independent Claim
106 words
An apparatus for demodulating a frequency modulated analog signal comprising: means for receiving an analog signal, said signal comprising a carrier wave modulated by a subcarrier wave, the subcarrier wave being frequency-modulated by analog baseband information; mixer means, responsive to the analog signal, for demodulating the modulated subcarrier wave from the carrier wave; converter means responsive to the output of said mixer means for providing digital numbers representative of the amplitude of the modulated subcarrier wave; and demodulating means for receiving the digital numbers and for demodulating the analog baseband information from the subcarrier wave to provide a digital output representative of the baseband modulation frequency.
Claim 8
Independent Claim
167 words
An apparatus for demodulating a frequency modulated analog input signal, said signal including a subcarrier that is frequently modulated by an analog baseband signal, comprising: a converter for sampling said analog input signal at a known rate, said converter providing one digital number at its output for each sample, said digital number representating the analog amplitude of the input signal at the sample time; a differential circuit responsive to the digital numbers for providiNg a digital derivative of the digital numbers; a dividing circuit responsive to the digital numbers and to the digital derivative of the digital numbers for dividing the digital derivative of the digital numbers by the digital numbers, and; a root circuit responsive to the output of the dividing circuit for providing a digital root of the output of the dividing circuit, the degree of said root being equal to the order of the derivative provided by the differentiating circuit, whereby the output of the root circuit is the baseband information in digital form.
Claim 9
Independent Claim
167 words
An apparatus for demodulating a frequency modulated analog input signal, said signal including a subcarrier that is frequently modulated by an analog baseband signal, comprising: a converter for sampling said analog input signal at a known rate, said converter providing one digital number at its output for each sample, said digital number representating the analog amplitude of the input signal at the sample time; a differential circuit responsive to the digital numbers for providiNg a digital derivative of the digital numbers; a dividing circuit responsive to the digital numbers and to the digital derivative of the digital numbers for dividing the digital derivative of the digital numbers by the digital numbers, and; a root circuit responsive to the output of the dividing circuit for providing a digital root of the output of the dividing circuit, the degree of said root being equal to the order of the derivative provided by the differentiating circuit, whereby the output of the root circuit is the baseband information in digital form.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |