Carrier recovery in vestigial sideband data receivers
阅读：386发布：2021-11-29
专利汇可以提供Carrier recovery in vestigial sideband data receivers专利检索，专利查询，专利分析的服务。并且A coherent demodulating carrier-wave recovery arrangement for a digital data communication system using vestigial-sideband amplitude-modulation techniques responds to a quadrature component only of a transmitted carrier wave. The transmitted quadrature carrier component eliminates the normal requirement for suppression of in-phase signal energy in the vicinity of zero frequency (direct current) or transmission of out-of-band pilot tones. Separate phase-locked loops control demodulating carrier frequency and phase to compensate for the transmission impairments of frequency offset and phase jitter occurring in distorting transmission channels.，下面是Carrier recovery in vestigial sideband data receivers专利的具体信息内容。
1. A synchronous demodulating carrier-wave recovery system for a vestigiaL-sideband, amplitude-modulated data signal which includes a discrete carrier component and which is received over a transmission channel subject to the impairments of frequency offset and phase jitter comprising an adjustable local oscillator, a quadrature demodulator responsive to said received signal and to the output of said local oscillator, a control loop having a narrow bandwidth comparable to that of said frequency offset extending between said quadrature demodulator and said oscillator to control said oscillator, a transmission path for the output of said quadrature demodulator having a passband comparable to that of said phase jitter for isolating a phase-jitter component therein, means for multiplying said phase-jitter component by the output of said local oscillator to form a partial in-phase demodulating signal, means for combining said partial in-phase demodulating signal with a quadrature rotated output of said local oscillator to form a complete in-phase demodulating signal having both frequency-offset and phase-jitter components, and an in-phase demodulator responsive jointly to said received signal and to said complete in-phase demodulating signal to form a data output substantially free of frequency-offset and phase-jitter impairments.
2. The synchronous carrier recovery system defined in claim 1 in which said transmission path for said phase-jitter component further comprises a bandpass filter whose bandwidth is comparable to that of said phase-jitter component and an attenuator in series with said last-mentioned filter for compensating for the transmission level of said discrete carrier component.
3. The synchronous carrier recovery system of claim 1 in which an integrator operates on the output of said in-phase demodulator to derive therefrom an output corresponding in magnitude to the transmission level of the carrier-frequency component in said received signal and a subtractor jointly responsive to the outputs of said in-phase demodulator and said integrator removes the direct-current component from the output of said in-phase demodulator.
4. In combination with a vestigial-sideband, amplitude-modulated transmission system for data signals which includes a discrete carrier component shaped to exclude quadrature direct-current energy, said transmission system having a tendency to impart distorting frequency-offset and phase-jitter components to received signals, a synchronous demodulating carrier recovery arrangement comprising an in-phase demodulator; a quadrature demodulator; means for applying received data signals to said in-phase and quadrature demodulators; a local carrier-wave source; a first control loop jointly controlled by said quadrature demodulator and said carrier-wave source to lock the frequency of said carrier-wave source to the discrete carrier component in received data signals, said first control loop having a narrow passband including direct current comparable to the passband of said frequency-offset component; a second control loop jointly responsive to said quadrature demodulator and said carrier-wave source for tracking the phase-jitter component of said received signal, said second control loop having a passband not including direct current comparable to the passband of said phase-jitter component; means included in said second control loop for multiplying together the output of said carrier-wave source with said phase-jitter component thereby producing a demodulating carrier-wave with a superposed phase-jitter component; further means included in said second control loop for attenuating said phase-jitter component therein in accordance with the amplitude of the discrete carrier component in said received signal and for applying said attenuated phase-jitter component to said multiplying means; means for shifting the phase of the output of said carrier-wave source by 90 electrical degrees to provide an in-phase demodulating carrier-wave; means responsive to the output of said multiplying means for adding said superposed phase-jitter component to the in-phase demodulating carrier wave from said phase-shifting means; means for applying the output of said adding means to said in-phase demodulator; means for integrating the output of said in-phase demodulator to obtain the direct-current component of the demodulated received signal; means for substituting the direct-current component obtained from said integrating means from the demodulated received signal from said in-phase demodulator; and further means for applying the direct-current output from said integrating means to said attenuating means to control the effective level of attenuation thereat.
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