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US4562404A
Expired / Lapsed
US
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FM Demodulator with selective phase shift circuits
Assignee: Murata Manufacturing Co Ltd
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Filing: 1984-07-18
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Granted: 1985-12-31
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Expires: 2004-07-18
Abstract
Abstract The disclosure is directed to an improved FM demodulating circuit which is simple in circuit construction, with a small number of parts required, and so arranged that in a quadrature detecting circuit, a plurality of piezoelectric resonators, for example, ceramic discriminators employed for a phase shift circuit are changed over by switching circuits for common use of parts other than the ceramic discriminators for the demodulation of the FM intermediate frequency signals.
Inventors
- 👤 Tomoaki Futakuchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 09:33
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/06; H03D3/16
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
138 words
In a quadrature detecting circuit which is so arranged that an FM intermediate frequency signal produced from an FM intermediate frequency amplifying circuit, and a signal obtained by subjecting the FM intermediate frequency signal to phase shifting through a phase shift circuit are respectively input to a multiplier so as to obtain an FM demodulating signal by a phase difference between these two signals, an FM demodulating circuit comprising DC blocking capacitors respectively inserted between said phase shift circuit and said FM intermediate frequency amplifying circuit, and between said phase shift circuit and said multiplier, said phase shift circuit including a plurality of piezoelectric resonators to be respectively tuned to different FM intermediate frequencies, and change-over circuits made of switching diodes and respectively connected between input and output sides of said piezoelectric resonators and said DC blocking capacitors.
Claim 2
Dependent Claim
138 words
In a quadrature detecting circuit which is so arranged that an FM intermediate frequency signal produced from an FM intermediate frequency amplifying circuit, and a signal obtained by subjecting the FM intermediate frequency signal to phase shifting through a phase shift circuit are respectively input to a multiplier so as to obtain an FM demodulating signal by a phase difference between these two signals, an FM demodulating circuit comprising DC blocking capacitors respectively inserted between said phase shift circuit and said FM intermediate frequency amplifying circuit, and between said phase shift circuit and said multiplier, said phase shift circuit including a plurality of piezoelectric resonators to be respectively tuned to different FM intermediate frequencies, and change-over circuits made of switching diodes and respectively connected between input and output sides of said piezoelectric resonators and said DC blocking capacitors.
Claim 3
Dependent Claim
31 words
An FM demodulating circuit as claimed in claim 1, wherein the plurality of piezoelectric resonators are a first piezoelectric resonator for 5.5 MHz and a second piezoelectric resonator for 6.5 MHz.
Claim 4
Dependent Claim
27 words
An FM demodulating circuit as claimed in claim 1, wherein said phase shift circuit further includes changeover switches associated with said switching diodes for the change-over circuits.
Claim 5
Dependent Claim
32 words
An FM demodulating circuit as claimed in claim 1, wherein said phase shift circuit further includes semiconductor elements arranged to apply different voltages to said respective switching diodes for the change-over circuits.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-12-30 | 1989-07-01 | 1989-12-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-30 | 1993-07-01 | 1993-12-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-30 | 1997-07-01 | 1997-12-31 | $7700.00 | Window Closed / Lapsed |