Receiver for phase-shift modulated carrier signals
First Claim
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1. A receiver for recovering digital data modulated upon a carrier waveform in a digital communication system comprising:
- (a) first frequency generating means for producing a first local oscillator signal;
(b) second frequency generating means coupled to said first frequency generating means for producing a second local oscillator signal wherein said first and second local oscillator signals are in quadrature phase relationship with respect to each other;
(c) mixing means coupled to said first and second frequency generating means, respectively, for mixing the modulated carrier with each of said first and second local oscillator signals to form first and second recovered modulation signals, respectively;
(d) amplitude detecting means coupled to said mixing means for selecting the larger and smaller of said first and second recovered modulation signals to form a data signal and a servo signal, respectively;
(e) multiplier means coupled to said amplitude detecting means for multiplying said servo signal by said data signal to form a servo control signal;
(f) frequency varying means coupled to said first frequency generating means for varying the frequency of said first local oscillator signal in response to said servo control signal; and
(g) polarity restoration means coupled to said amplitude detecting means for receiving said data signal and for providing a recovered data signal having the same logic sense as the digital data modulated upon the carrier waveform.
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Abstract
A receiver for recovering digital data from a phase-shift modulated carrier in a data communications system, wherein the length of the message preamble is insufficient to permit synchronous detection, divides the received signal into two channels. The channels having the larger and smaller signals are selected as the data and the servo channel, respectively. The output of the servo channel is utilized to control the local oscillator frequency in order to provide for synchronous detection during at least a part of the message data.
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Citations
15 Claims
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1. A receiver for recovering digital data modulated upon a carrier waveform in a digital communication system comprising:
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(a) first frequency generating means for producing a first local oscillator signal; (b) second frequency generating means coupled to said first frequency generating means for producing a second local oscillator signal wherein said first and second local oscillator signals are in quadrature phase relationship with respect to each other; (c) mixing means coupled to said first and second frequency generating means, respectively, for mixing the modulated carrier with each of said first and second local oscillator signals to form first and second recovered modulation signals, respectively; (d) amplitude detecting means coupled to said mixing means for selecting the larger and smaller of said first and second recovered modulation signals to form a data signal and a servo signal, respectively; (e) multiplier means coupled to said amplitude detecting means for multiplying said servo signal by said data signal to form a servo control signal; (f) frequency varying means coupled to said first frequency generating means for varying the frequency of said first local oscillator signal in response to said servo control signal; and (g) polarity restoration means coupled to said amplitude detecting means for receiving said data signal and for providing a recovered data signal having the same logic sense as the digital data modulated upon the carrier waveform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification