Abstract: A quadrature vestigial-sideband (QVSB) method and system with correlated noise removal are embodied in a QVSB receiver with a correlated-noise estimator-subtractor configured to obtain I/Q channel correlated noise estimates for receive-filtered I/Q signals in the QVSB receiver, and to subtract the I/Q channel correlated noise estimates from the receive-filtered I/Q signals to whiten noises entering a quadrature-crosstalk, maximum-likelihood-sequence-estimator (QC-MLSE) of the QVSB receiver.

Abstract: A quadrature vestigial sideband (QVSB) communication system provide bandwidth efficient data transmission using cross coupled data signaling during both transmit and receive having controlled intersymbol interference. The QVSB modem includes cross coupled arm transmit and receive data filtering on both of the I&Q channels providing a bandwidth efficient QVSB spectra. A quadrature crosstalk maximum likelihood sequence estimator implements a Viterbi decoding algorithm for providing estimated data sequence outputs. The receiver is a coherently aided demodulator synchronized by a synchronization loop providing time and phase references using the estimated data sequence outputs.

Abstract: A quadrature vestigial sideband (QVSB) communication system provide bandwidth efficient data transmission using cross coupled data signaling during both transmit and receive having controlled intersymbol interference. The QVSB modem includes cross coupled arm transmit and receive data filtering on both of the I&Q channels providing a bandwidth efficient QVSB spectra. A quadrature crosstalk maximum likelihood sequence estimator implements a Viterbi decoding algorithm for providing estimated data sequence outputs. The receiver is a coherently aided demodulator synchronized by a synchronization loop providing time and phase references using the estimated data sequence outputs.

Abstract: A quadrature vestigial-sideband (QVSB) method and system with correlated noise removal are embodied in a QVSB receiver with a correlated-noise estimator-subtractor configured to obtain I/Q channel correlated noise estimates for receive-filtered I/Q signals in the QVSB receiver, and to subtract the I/Q channel correlated noise estimates from the receive-filtered I/Q signals to whiten noises entering a quadrature-crosstalk, maximum-likelihood-sequence-estimator (QC-MLSE) of the QVSB receiver.

Abstract: Predetection noise bandwidth reduction is effected by a pre-averager capable of digitally averaging the samples of an input data signal over two or more symbols, the averaging interval being defined by the input sampling rate divided by the output sampling rate. As the averaged sample is clocked to a suitable detector at a much slower rate than the input signal sampling rate the noise bandwidth at the input to the detector is reduced, the input to the detector having an improved signal to noise ratio as a result of the averaging process, and the rate at which such subsequent processing must operate is correspondingly reduced. The pre-averager forms a data filter having an output sampling rate of one sample per symbol of received data. More specifically, selected ones of a plurality of samples accumulated over two or more symbol intervals are output in response to clock signals at a rate of one sample per symbol interval.

Abstract: Predetection noise bandwidth reduction is effected by a pre-averager capable of digitally averaging the samples of an input data signal over a single symbol, the averaging interval being defined by the input sampling rate divided by the output sampling rate. As the averaged sample is clocked to a suitable detector at a much slower rate than the input signal sampling rate the noise bandwidth at the input to the detector is reduced, the input to the detector having an improved signal to noise ratio as a result of the averaging process, and the rate at which such subsequent processing must operate is correspondingly reduced. The pre-averager may form a data filter when the output sampling rate is reduced to one sample per symbol of received data.

Abstract: A coherent phase and frequency recovery method capable of rapidly recovering the phase and frequency of bursts of received signals from plural sources. The received signal is applied to a first input of a mixer, the output of which is amplified and applied to two feedback paths, one for frequency and the other for phase. The frequency path contains a loop filter driving a voltage-controlled oscillator, and the phase path a loop filter and amplifier. Initial estimates of the phase and frequency of the present burst are derived and injected into the respective feedback paths. The output of the phase path is applied to correct the phase of the output of the frequency path, which is then applied to a second input of the mixer.

Abstract: A symbol timing recovery circuit with a clock synchronization loop for variable rate data signals utilizes a frequency synthesizer for setting the frequency of the recovered clock signal. The received data signal, representing the modulating waveform of a transmitted modulated wareform, is estimated by passage through a data filter and sampling comparator sampled by the recovered clock. The received data signal is also delayed and multiplied by the time derivative of the estimated data signal to produce an error signal representing the difference between the incoming data rate and the output of a narrow pull range voltage controlled oscillator, VCO. The error signal is input to the VCO to correct the VCO output. A programmable frequency synthesizer provides timing signals having a range of the symbol rate divided by n.

Abstract: Concurrent carrier and clock synchronization are derived from an input signal in interdependent loops without the use of phase look loop (PLL) circuitry in order to improve operation at higher bit rates. An acquisition detection signal is generated only in response to predetermined minimum errors in both the received signal amplitude and the recovered carrier phase.

Abstract: The present invention is directed to circuitry for achieving concurrent synchronization of carrier phase and clock timing in double-sideband, suppressed carrier transmissions systems. A phase-lock loop (PLL) is used in the respective carrier and clock recovery networks. The carrier recovery loop is similar to the conventional "Costas Loop". The PLLs are cross coupled in an interdependent recovery structure to enable a more effective clock and carrier regeneration.