Abstract: Methods and systems are provided for cable distribution networks, in which a headend may generate one or more downstream signals for communication in a distribution network associated with the headend. The generating of the one or more downstream signals may comprise combining data and/or video for one or more service groups, from signals corresponding to a plurality of services, with the combining being performed in digital domain. The distribution network comprises a cable distribution network, such as a hybrid fiber-coaxial (HFC) based network. The plurality of services comprises cable television (e.g., DOCSIS) services, VOD services, SDV services, OOB services, and/or broadcast television services. The headend may control feedback from the distribution network, and may control the combining performed therein based on the received control feedback. The control feedback may be received from, for example, fiber nodes and/or user equipment in the distribution network.

Abstract: A digital receiver for processing a signal received from a channel includes a digital demodulator and an equalizer coupled to the digital demodulator. The equalizer includes a feedforward filter and a decision feedback equalizer (DFE), wherein the feedforward filter includes a plurality of feedforward filter taps. Coefficients are associated with the plurality of feedforward filter taps and the values of all of the coefficients associated with the plurality of feedforward filter taps are dynamically determined.

Abstract: A method of controlling the operation of an equalizer (210, 216), wherein the equalizer is adapted to receive a transmitted signal (76, 78) comprising at least one predetermined sequence of symbols, includes the step of developing a set of samples from a received signal. At least one plurality of samples is identified, wherein the at least one plurality of samples corresponds to the at least one predetermined sequence of symbols. The equalizer is then operated in a selected one of three modes. A first mode is selected if the at least one plurality of samples is identified, wherein the first mode includes the step of developing a signal-to-noise ratio (SNR) (100). A second mode is selected if the at least one plurality of samples is identified and the SNR is greater than a first predetermined threshold. A third mode is selected if the at least one plurality of samples is identified and the SNR is greater than a second predetermined threshold.

Abstract: A method of controlling a feedforward filter of an equalizer includes the steps of generating a complex representation of an output of the feedforward filter and generating a representation of a decision from an output of the equalizer. The complex representation and the decision representation are correlated to obtain a phase error estimate. A phase correction value is generated based on the phase error estimate and used to adjust the phase of the output of the feedforward filter.

Abstract: An automatic gain control (AGC) circuit that includes an RF amplifier with first and second distinct active gain control regions, wherein a gain of the RF amplifier varies during operation in the active gain control regions

Abstract: A method of controlling the operation of an equalizer (210, 216), wherein the equalizer is adapted to receive a transmitted signal (76, 78) comprising at least one predetermined sequence of symbols, includes the step of developing a set of samples from a received signal. At least one plurality of samples is identified, wherein the at least one plurality of samples corresponds to the at least one predetermined sequence of symbols. The equalizer is then operated in a selected one of three modes. A first mode is selected if the at least one plurality of samples is identified, wherein the first mode includes the step of developing a signal-to-noise ratio (SNR) (100). A second mode is selected if the at least one plurality of samples is identified and the SNR is greater than a first predetermined threshold. A third mode is selected if the at least one plurality of samples is identified and the SNR is greater than a second predetermined threshold.

Abstract: A digital receiver for processing a signal received from a channel includes a digital demodulator and an equalizer coupled to the digital demodulator. The equalizer includes a feedforward filter and a decision feedback equalizer (DFE), wherein the feedforward filter includes a plurality of feedforward filter taps. Coefficients are associated with the plurality of feedforward filter taps and the values of all of the coefficients associated with the plurality of feedforward filter taps are dynamically determined.

Abstract: A method of controlling a feedforward filter of an equalizer includes the steps of generating a complex representation of an output of the feedforward filter and generating a representation of a decision from an output of the equalizer. The complex representation and the decision representation are correlated to obtain a phase error estimate. A phase correction value is generated based on the phase error estimate and used to adjust the phase of the output of the feedforward filter.

Abstract: A system and method for calibrating power level during initial ranging of a network client device, such as cable modem facilitates communications between a network client device and a network device such as a cable modem termination system. The method includes dividing the dynamic range of the cable modem transmitter into a plurality of regions and attempting initial ranging in each of the different regions. If a response is not received from the network device, the method including adjusting the power level and reattempting the initial ranging in the different regions. Once a range response message is received from the network device the process of initial ranging is complete.

Abstract: A receiver for receiving a cable and terrestrial digital signals of differing VSB modes where the data levels of the various signals have a desired relationship that enables simple data level slicing and error determination. Some of the signals have sync levels that do not conform to the desired relationship and the receiver includes a comb filter for reducing interference when receiving an 8VSB terrestrial signal. The mode of the received signal is determined and a correction factor is applied to the syncs of the signals as needed to reestablish the desired relationship. Operation of the comb filter results in additional levels and a disruption of the desired relationship. For such cases, the comb filtered data levels are modified to make them a subset of the VSB 16 data levels. The modifications are accomplished in feedback paths of the phase tracker after the circuit equalizer and do not affect the data levels passed to the next stage.

Abstract: A technique and apparatus for developing AGC voltage in a receiver capable of receiving VSB signals that do not have the data symbol levels and the sync symbol levels related so as to produce the same average magnitude level. Successive portions of the signal are accumulated, stored and compared with the smaller of the samples to be used to develop the AGC voltage. By comparing the first and third of three successive samples, the effect of the larger than desired sync levels in the over-the-air VSB signals is completely eliminated.

Abstract: A VSB mode detection circuit with a comb filter solves the potential problem of lockout in a situation where an 8 VSB mode signal is being received, with the comb filter being effective, and a change in signal mode suddenly occurs. The arrangement inhibits the first two bytes of the three byte mode information, which two bytes are unspecified for all except the 8 VSB terrestrial mode, and replaces them with zero data. In another embodiment, the 12 symbol delay in the comb filter is bypassed with the complement of the input data for the third byte. When the 8 VSB terrestrial mode has been confidently determined to exist, the inhibition of the first and second bytes (and the inversion of the bypassed third byte) is removed in alternate fields to permit normal comb filter operation.

Abstract: A technique and apparatus for developing AGC voltage in a receiver capable of receiving VSB signals that do not have the average magnitudes of the data symbol levels and the sync symbol levels related so as to produce the same average level. One technique eliminates the sync symbols from determination of the AGC voltage. A preferred technique corrects for the different symbol levels of the sync by multiplexing in an offset at the proper time or multiplying the sync symbols by a compensating factor.

Abstract: A cable system includes a cable head end and a plurality of distribution sites having equipment for supplying subscriber station receivers with digital video cable signals from the cable head end. The digital video signal includes a robust data component that is receivable by distribution site receivers and cable subscriber station receivers under very poor carrier-to-noise conditions, that is, where the video signal itself is not usable. The cable head end has capabilities for interrogating distribution site receivers and subscriber station receivers which respond by transmitting designated information concerning differences between the received robust data component and the transmitted robust data component. At the subscriber station receivers, the robust data component is in the form of a training sequence of known characteristics that is compared with a received training sequence.

Abstract: An AFC filter for an FPLL comprises a filter formed of a network of resistors and capacitors exhibiting a predetermined phase response characteristic. The phase response characteristic is limited with increasing frequency to a value of about 90.degree. during a start-up interval.

Abstract: A bi-phase stable FPLL is locked by a DC pilot component in a recovered data signal. The signal is formatted in repetitive data segments including sync characters and a DC pilot. A sign bit, indicative of the polarity of the recovered data, is developed from the sync characters and is used to augment the DC pilot to stabilize the lock up of the FPLL to produce the desired polarity of recovered data.

Abstract: A television receiver includes a synchronous demodulator including a bi-phase stable PLL for controlling sampling of the received signal to produce data. A phase inverter reverses the phase of the data in response to a control signal. Data segment sync characters are recovered with a sync correlation filter that also yields a sign bit indicating polarity. If the sign bit is wrong for a predetermined number of data segment sync characters, a control signal is produced to operate the phase inverter.

Abstract: A dual mode AGC system for a television receiver in which data is in the form of symbols occurring at a fixed symbol rate. The symbols are sent in successive data segments, each having a sync character. Enablement of an AFC Defeat signal defines an initial interval during which the IF gain is maximum. When the AFC Defeat signal becomes inactive, the receiver is operated in a non-coherent mode in which the gain of the IF amplifier is reduced incrementally whenever the IF signal exceeds a clipping level for a period of eight successive symbol clocks. Upon a segment sync lock condition occurring, a normal coherent mode is entered in which the AGC responds to a signal characteristic, i.e. data segment sync. The rate of gain change available in the non-coherent mode-is much greater than that in the normal coherent mode.

Abstract: A circuit for error correcting a received complex data signal comprises a synchronous detector for recovering an in-phase data component from the received signal and a Hilbert transform filter for estimating the related quadrature component from the recovered in-phase data component, the recovered in-phase data component including a periodically recurring reference signal. A decision feedback loop is periodically operable in response to the reference signal for initially error correcting a selected characteristic of the received signal at a first relatively rapid rate and for subsequently error correcting the selected characteristic at a rate which is less than the first rate and which is dependent upon the estimated S/N ratio of the received signal. In one embodiment, phase errors are corrected at a rate which is also directly related to the value of the estimated quadrature component. In another embodiment, amplitude errors, e.g.

Abstract: A circuit for error correcting a received complex data signal comprises a synchronous detector for recovering an in-phase data component from the received signal and a Hilbert transform filter for estimating the related quadrature component from the recovered in-phase data component, the recovered in-phase data component including a periodically recurring reference signal. A decision feedback loop is periodically operable in response to the reference signal for initially error correcting a selected characteristic of the received signal at a first relatively rapid rate and for subsequently error correcting the selected characteristic at a rate which is less than the first rate and which is dependent upon the estimated S/N ratio of the received signal. In one embodiment, phase errors are corrected at a rate which is also directly related to the value of the estimated quadrature component. In another embodiment, amplitude errors, e.g.