EP0208284A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Demodulator capable of avoiding abnormal demodulation
Assignee: NEC Corp
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Filing: 1986-07-07
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Granted: —
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Expires: 2006-07-07
Abstract
Abstract In a demodulator for use in demodulating a guadrature amplitude modulated signal into a first and a second digital signal by the use of a reproduction of a carrier wave, a pull-in phase is detected by a pull-in phase discriminator (66) after establishment of synchronization. The reproduction of the carrier wave is momentarily phase shifted in a phase modulator (65) with reference to the pull-in phase to be produced as a phase shifted carrier signal. The resultant pull-in phase is momentarily corrected to avoid abnormal demodulation. Detection of the pull-in phase is possible either by monitoring a demodulated analog signal and the first and the second digital signals or by monitoring only the first and the second digital signals. The phase modulator may be either a two-phase modulator or a nπ/2-phase one where n is a natural number between unity and three, both inclusive.
Inventors
- 👤 Yasuharu C/O Nec Corporation Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 19:52
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/32; H04L27/34; H04L27/38; H04L27/3818
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
150 words
A demodulator comprising demodulation means for demodulating a modulated signal subjected to quadrature amplitude modulation into a first and a second digital signal when said demodulator is put into a pull-in state and generating means responsive to said first and said second digital signals for generating a reproduction of a carrier wave with reference to said first and said second digital signals, wherein said demodulator further comprises: pull-in phase detecting means coupled to said demodulation means for detecting said pull-in state to produce a pull-in phase signal indicative of a pull-in phase; phase shift means coupled to said pull-in phase detecting means and said generating means for shifting a phase of said reproduction of the carrier wave in accordance with said pull-in phase signal to produce a phase shifted signal; and means for supplying said phase shifted signal to said demodulation means to make said demodulation means carry out demodulation.
Claim 2
Dependent Claim
150 words
A demodulator comprising demodulation means for demodulating a modulated signal subjected to quadrature amplitude modulation into a first and a second digital signal when said demodulator is put into a pull-in state and generating means responsive to said first and said second digital signals for generating a reproduction of a carrier wave with reference to said first and said second digital signals, wherein said demodulator further comprises: pull-in phase detecting means coupled to said demodulation means for detecting said pull-in state to produce a pull-in phase signal indicative of a pull-in phase; phase shift means coupled to said pull-in phase detecting means and said generating means for shifting a phase of said reproduction of the carrier wave in accordance with said pull-in phase signal to produce a phase shifted signal; and means for supplying said phase shifted signal to said demodulation means to make said demodulation means carry out demodulation.
Claim 3
Dependent Claim
122 words
A demodulator as claimed in Claim 1, said demodulation means comprising signal producing means responsive to said modulated signal for producing a first and a second analog demodulated signal and converting means coupled to said signal producing means for converting said first and said second analog demodulated signals into said first and said second digital signals, respectively, wherein said pull-in phase detecting means comprises: means coupled to said signal producing means and said-converting means for producing first and second timing signals synchronized with said first and said second digital signals, respectively; and discriminating means responsive to said first and said second timing signals for discriminating said pull-in state from said first and said second timing signals to produce said pull-in phase signal.
Claim 4
Dependent Claim
73 words
A demodulator as claimed in Claim 1 or 2, wherein said phase shift means comprises: phase correction signal producing means for producing a phase correction signal; and phase modulation means responsive to said reproduction of the carrier signal and said phase correction signal and coupled to said discriminating means for carrying out phase modulation of said reproduction of the carrier wave with reference to said pull-in phase signal and said phase correction signal.
Claim 5
Dependent Claim
57 words
A demodulator as claimed in Claim 3, wherein said phase modulation means comprises: gate means for gating said phase correction signal with reference to said pull-in phase signal to produce a gate output signal; and modulating means for phase modulating said reproduction of the carrier wave by said gate output signal to produce said phase shifted signal.
Claim 6
Dependent Claim
60 words
A demodulator as claimed in Claim 4, wherein said modulating means comprises: a two-phase modulator for phase modulating the reproduction of said carrier by said gate output signal to change the phase of said reproduction by τ/2 radians each time when said gate output signal is supplied to said two phase modulator and to thereby produce said phase shifted signal.
Claim 7
Dependent Claim
104 words
A demodulator as claimed in any of Claims 1 to 5, wherein said pull-in phase detecting means comprises: pull-in phase signal producing means for producing said pull-in phase signal in response to said first and said second digital signals; said phase shift means comprising: phase correction signal producing means for producing a phase correction signal; and phase modulation means coupled to said phase correction signal producing means and said pull-in phase signal producing means for carrying out phase modulation of said reproduction of the carrier wave with reference to said pull-in phase signal and said phase correction signal to produce said phase shifted signal.
Claim 8
Dependent Claim
57 words
A demodulator as claimed in Claim 6, wherein said phase modulation means comprises: gate means for gating said phase correction signal with reference to said pull-in phase signal to produce a gate output signal; and modulating means for phase modulating said reproduction of the carrier wave by said gate output signal to produce said phase shifted signal.
Claim 9
Dependent Claim
60 words
A modulator as claimed in Claim 7, wherein said modulating means comprises: a phase modulator for phase modulating said reproduction of the carrier wave by said gate output signal to change the phase of the reproduction by nπ/2 radians each time when said gate output signal is produced, where n is a natural number between unity and three, both inclusive.
References Cited (Backward Citations)
No citation records indexed.
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