Patent EP0398254A2 successfully refreshed from Google Patents.
EP0398254A2
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EP
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FM demodulator
Assignee: Sanyo Electric Co Ltd
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Filing: 1990-05-15
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Granted: —
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Expires: 2010-05-15
Abstract
Abstract A FM signal is applied to a variable gain amplifier (5) of an FM demodulator. The gain of variable gain amplifier (5) is varied in response to a gain control signal. The output signal of variable gain amplifier (5) is applied to an FM demodulating circuit (7) constituting a PLL circuit via a BPF (6). The output signal of BPF (6) is also applied to a synchronous detector (12) via a 90° fixed phase shifter (11). The output signal of a VCO (10) included in the PLL circuit is applied to synchronous detector (12) as the reference signal. The synchronous detector (12) is responsive to the reference signal for synchronous detecting the output signal of 90° fixed phase shifter (11). The output signal of synchronous detector (12) is applied to variable gain amplifier (5) via a LPF (13) as the gain control signal. Thus, variable gain amplifier (5) is responsive to the output signal of synchronous detector (12) for making the amplitude of the FM audio signal included in the FM signal constant.
Inventors
- 👤 Katsunori Miura
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 22:46
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/24; H03D3/241; H03D3/244; H04; H04N; H04N9/00; H04N9/79; H04N9/80; H04N9/82; H04N9/83; H04N9/835; H04N9/8355
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
136 words
A FM demodulator for demodulating a predetermined band component of an FM signal comprising: variable gain amplifier means (5) receiving said FM signal for varying its gain in response to a predetermined control signal, filter means (6) for passing a predetermined band component of the output signal of said variable gain amplifier means (5), phase locked loop means including voltage controlled oscillator means (10) for FM demodulating the output signal of said filter means (6), and synchronous detection means (12) responsive to the output signal of said voltage controlled oscillator means (10) for synchronous detecting the output signal of said filter means (6) to supply the detected signal as said predetermined control signal to said variable gain amplifier means (5) so that the amplitude of said predetermined band component of said FM signal may be constant.
Claim 2
Dependent Claim
136 words
A FM demodulator for demodulating a predetermined band component of an FM signal comprising: variable gain amplifier means (5) receiving said FM signal for varying its gain in response to a predetermined control signal, filter means (6) for passing a predetermined band component of the output signal of said variable gain amplifier means (5), phase locked loop means including voltage controlled oscillator means (10) for FM demodulating the output signal of said filter means (6), and synchronous detection means (12) responsive to the output signal of said voltage controlled oscillator means (10) for synchronous detecting the output signal of said filter means (6) to supply the detected signal as said predetermined control signal to said variable gain amplifier means (5) so that the amplitude of said predetermined band component of said FM signal may be constant.
Claim 3
Dependent Claim
84 words
The FM demodulator according to claim 1, wherein said phase locked loop means (7) further comprises phase comparing means (8) for comparing the phase of the output signal of said filter means (6) with the phase of the output signal of said voltage controlled oscillator means (10) to output a signal having the voltage corresponding to the phase difference, said voltage controlled oscillator means (10) provides the signal with the corresponding frequency in response to the output signal of said phase comparing means (8).
Claim 4
Dependent Claim
54 words
The FM demodulator according to claim 2, wherein said phase locked loop means (7) further comprises a first low pass filter means (9) provided between said phase comparing means (8) and said voltage controlled oscillator means (10) for passing a predetermined low frequency component of the output signal of said phase comparing means (8).
Claim 5
Dependent Claim
47 words
The FM demodulator according to claim 5, further comprising: a second low pass filter means (13) provided between said synchronous detection means (12) and said variable gain amplifier means (5) for passing a predetermined low frequency component of the output signal of said synchronous detection means (12).
Claim 6
Dependent Claim
34 words
The FM demodulator according to claim 1, further comprising: phase shifting means (11) for phase shifting the output signal of said filter means (6) and providing the same to said synchronous detection means (12).
Claim 7
Dependent Claim
46 words
The FM demodulator according to claim 4, further comprising: muting means (15) for providing the output signal of said first low pass filter means (9) when the level of the output signal of said second low pass filter means (13) is higher than a predetermined level.
Claim 8
Dependent Claim
55 words
The FM demodulator according to claim 6, further comprising comparing means (16) for comparing the level of the output signal of said second low pass filter means (13) with a predetermined level to provide the compared result, and wherein said muting means (15) operates in response to the output signal of said comparing means (16).
Claim 9
Dependent Claim
17 words
The FM demodulator according to claim 1, wherein said filter means (6) comprises of an active filter.
Claim 10
Independent Claim
99 words
A method for demodulating a predetermined band component of an FM signal comprising the steps of: varying the amplitude of said FM signal in response to a predetermined control signal, passing a predetermined band component of said amplitude varied FM signal, FM demodulating said band component by the phase locked loop including voltage controlled oscillator means, and synchronous detecting said band component in response to the output signal of said voltage controlled oscillator means to supply the detected signal as said predetermined control signal so that the amplitude of said predetermined band of the FM signal may be constant.
Claim 11
Independent Claim
99 words
A method for demodulating a predetermined band component of an FM signal comprising the steps of: varying the amplitude of said FM signal in response to a predetermined control signal, passing a predetermined band component of said amplitude varied FM signal, FM demodulating said band component by the phase locked loop including voltage controlled oscillator means, and synchronous detecting said band component in response to the output signal of said voltage controlled oscillator means to supply the detected signal as said predetermined control signal so that the amplitude of said predetermined band of the FM signal may be constant.
References Cited (Backward Citations)
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