Abstract: A signal compensation circuit compensates for direct-current offset of an input signal by amplifying the input signal with an amplifier having a variable direct-current offset. A low-speed negative feedback loop charges and discharges a capacitor in an integrating circuit according to the direct-current component of the amplified signal. A high-speed negative feedback loop charges and discharges the same capacitor at a faster rate when the amplified signal goes outside an allowable amplitude range. The capacitor potential is used to control the direct-current offset of the amplifier. The allowable amplitude range is adjusted according to the amplitude of the amplified signal. High-speed compensation can thus be combined with a tolerance for runs of identical code levels in the input signal.

Abstract: A SOVA decoding method determines, for each information symbol time and each state of a decoding trellis, a vector of probabilities for each possible symbol value in accordance with transition path probabilities for reaching the state with respective information symbol values and probability vectors for the states at the previous information symbol time from which the state can be reached, and also determines a total probability for each state. A soft output is provided by summing probabilities for corresponding symbol values all states of the trellis at an information symbol time relating to the start of the vectors, corresponding to a desired survivor path length. The vectors can comprise probability ratios instead of probabilities to reduce storage especially for binary signal decoding, and logarithmic probabilities or ratios can be used to simplify computation.

Abstract: A digital filter or a receiver including a digital filter having at least two multiple stage shift registers. A plurality of multipliers corresponding in number to the number of stages in the at least two multiple stage shift registers receive as a first input an output from a corresponding stage of the at least two multiple stage shift registers. A tap weight shifter is coupled to a tap weight source to receive tap weights. The tap weight shifter is coupled to provide a second input to each multiplier. Each multiplier produces an output that is the product of inputs thereto. An adder sums the multiplier outputs to provide a sum output. The tap weight shifter then circularly shifts the tap weights and another multiply-add operation occurs. Several shift/multiply/add cycles may occur before data is again shifted into the at least two multiple stage shift registers, and another multiply-add operation occurs.

Abstract: A RAKE receiver with demodulating fingers is presented having the capability to assign a specific sample stream, from among a plurality of received sample streams, to any of the demodulating fingers. The demodulating finger includes a MUX to receive the plurality of sample streams. Commands from a controller to the MUX of a demodulating finger select a specific sample stream to be demodulated by that demodulating finger. Since each demodulating finger receives all the sample streams, and any sample stream can be selected, the receiver has the flexibility of optimally varying the assignment of demodulating fingers to sample streams. A method for selecting a sample stream for demodulation, from among a plurality of sample streams, is also provided.

Abstract: A system and method for improving the performance of digital filters. The data bandwidth and spectral control are improved by adaptively selecting ramp-up and ramp-down symbols based on the actual filtered data. Thus, the energy in the truncated tail of the filter is minimized for a given filter design. The invention is of particular utility in systems that filters intermittent data streams, thus requiring the filter to energize and deenergize repeatedly.

Abstract: A receiver for improving the performance of conventional Discrete Multitone Modulation (DMT) based Asymmetric Digital Subscriber Line (ADSL) modems, in the presence of noise and/or interference. A demodulator having an FFT followed by a single-tap-per-bin frequency-domain equalizer is augmented by an additional data-path utilizing windowing or pulse shaping. Windowing is done independently for each symbol over the orthogonality interval and efficiently in the time domain or frequency domain. A decision feedback equalizer at the output of the windowed data-path cancels inter-bin-interference created by windowing.

Abstract: One example of symbol or bit error probability estimation in a communication system using soft decision information determines soft decision metric(s) for each symbol that is received over a communication channel and employs the soft decision metric(s) to obtain an estimate of symbol or bit error probability.

Abstract: A method and apparatus are provided that generate, transmit, or receive a training sequence in a communications system, where the training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation formal. In one embodiment, the invention includes selecting an original training sequence from a set of possible original training sequences having at least one desired property, forming a modified training sequence by modifying the original training sequence based on a corresponding modifying sequence, such that the modified training sequence exhibits the desired property of the original training sequence when used in a peak to average power constrained modulation format that would otherwise impair the desired property of the original training sequence.

Abstract: A communication system including an amplifier, a receiver, an analog to digital converter (ADC) and an insertion phase variation compensation module. The amplifier receives a communication signal. If the amplifier is enabled, the amplifier amplifies the communication signal and outputs the amplified communication signal to the receiver. If the amplifier is disabled, the amplifier passes the communication signal to the receiver without amplifying it. The receiver outputs an analog complex signal to the ADC. The ADC outputs a digital complex signal to the insertion phase variation compensation module which counteracts the effects of a phase offset intermittently introduced into the communication signal when the amplifier is enabled or disabled.

Abstract: Disclosed is a distortion compensating apparatus for correcting the size of a distortion compensation coefficient in such a manner that a transmit signal that has undergone distortion compensation will not exceed the dynamic range of a DA converter. Specifically, before a distortion compensation coefficient hn+1(p) that has been calculated by a calculation unit is stored in a coefficient memory, an assumption is made that distortion compensation will be performed using the distortion compensation coefficient hn+1(p). Then it is determined beforehand whether a signal x(t)*hn+1(p) that will be obtained by this distortion compensation will exceed the limit of a DA converter. If the limit will be exceeded, the size of the distortion compensation coefficient is reduced by a correction unit, the corrected distortion compensation coefficient is stored in the memory and the transmit signal is corrected using the stored distortion compensation coefficient.

Abstract: The present invention is directed to a detector for a high-density magnetic recording channel and other partial response channels. The present invention presents a method for decoding a high rate product code and a decoder which uses this method, comprising receiving a high rate product code; using a row detector to find a most likely codeword and a most likely error sequence for each row; and using a column processor to correct any remaining errors based on column parity bits and the most likely error sequence of each row. In a first aspect of the present invention, the row detector is implemented through a 2-VA detector. In a second aspect of the present invention, the row detector is implemented through a conventional VA detector and a hank of matched filters.

Abstract: An equalizer for use in a communication receiver includes an infinite impulse response (IIR) feedback filter operated in acquisition and tracking feedback modes on a sample by sample basis to form a hybrid Decision Feedback Equalizer (DFE) architecture. In acquisition mode, soft decision samples from the filtered received signal are input to the IIR filter. In the tracking mode, hard decision samples from a slicer are input to the IIR filter. Acquisition and tracking operating modes are selected in accordance with a set of decision rules on a sample by sample basis based on the quality of the current hard decision. If the current hard decision is low quality, then the soft decision sample (acquisition mode) is used. If the current hard decision is high quality, then the hard decision sample (tracking mode) is used. In such manner, the DFE is operated in a hybrid mode, i.e., using both soft and hard decisions on a sample by sample basis.

Abstract: A demodulator and a demodulating method for a mobile phone are provided. In particular, the present invention can simultaneously perform operation of improving the demodulation error rate caused by such as noise and external feedback loop operation being correction after detected, and can reduce the current consumption by restraining the increase of the process time at the simultaneous operation with an external correction circuit after detected, and can improve the CN ratio (ratio between carrier power and noise power).

Abstract: A multicast radio data communication system comprising a master and a plurality of slave stations uses a retransmission protocol. Data is transmitted by the master station and received by the slave stations. Slave stations having the weakest radio link are designated primary stations, and all other slaves are designated secondary stations. Any slave station may transmit a negative acknowledgement but only the primary stations may transmit a positive acknowledgement. Positive acknowledgements are transmitted in separate time slots, but negative acknowledgements transmitted by the secondary stations overlap the positive acknowledgements transmitted by primary stations. These negative acknowledgements corrupt reception of the positive acknowledgement by the master station, thereby ensuring that the data is retransmitted.

Abstract: The method and device attenuate an interferer of substantially known spectrum in a communication signal which has been transmitted through a transmission channel and processed through a signal-processing receiver chain. In these method and device, the substantially known spectrum is used to generate, independently of the communication signal, at least one image representative of a replica of the interferer after processing through the signal-processing receiver chain. The generated image is subtracted from the processed communication signal to produce a subtraction signal, and quality-indicative parameters of the processed communication signal and the subtraction signal(s) are calculated. Finally, the quality-indicative parameters are used to select one of the processed communication signal and subtraction signal(s) for further processing through the receiver. When a plurality of images are generated, these images have different features, for instance different amplitudes or phases.

Abstract: A digital telemetry system having improved data rate and robustness. The telemetry system has a data transmission cable having a first end and a second end, and is capable of transmitting data between the first and second end on at least two propagation modes. A data source connected at the first end has data transmission circuitry to generate data signals on these propagation modes. A receiver connected to the second end of the wireline cable has a first receive circuitry to receive signals on a first of the at least two propagation modes and a second receive circuitry to receive signals on a second of the at least two propagation modes. An adaptive far-end cross-talk cancellation circuitry connected to the first receive circuitry and to the second receive circuitry cancels out far-end cross-talk between the at least two propagation modes.

Abstract: A receiver for a code division multiple access system includes a pilot symbol producing section, a frequency offset estimating section and a local signal generating section. The pilot symbol producing section produces pilot symbols of complex vector expression from a received radio frequency (RF) signal based on a first local frequency signal and a second local frequency signal. The first local frequency signal has a frequency obtained by shifting a frequency of a carrier signal by an IF frequency and the second local frequency signal has a frequency equal to the IF frequency. The pilot symbols have been subjected to inverse modulation to remove a modulation component. The frequency offset estimating section carries out in-phase adding operations to the pilot symbols of the complex vector expression over a predetermined interval in accordance with a predetermined pattern.

Abstract: In a telecommunications transmission system using a DTM system as a multicarrier system and having at least two VDSL systems, each including a pair of modems, the at least two VDSL systems belonging to a single binder group common to both VDSL systems, a method in the DMT system for keeping DMT frames aligned to the same frame timing includes estimating the time mis-alignment and power of cross-talk DMT signals added to a received DMT signal when the estimate is used by the modem to synchronize its own frame timing to a main cross-talkers frame timing, using auto-correlation on the received signal and a delayed copy of the received signal, and detecting correlation maxima that determine the frame boundaries of different DMT components of the received signal.

Abstract: A method and apparatus for compensating for a distortion component of a device such as a power amplifier can be achieved without requiring a demodulator. A voltage controlling a gain of the amplitude of the input signal based on the amplitude control signal generated in the amplitude control signal generation step.

Abstract: All-digital FSK demodulation can be accomplished by producing in response to a received IF signal digital information (22) indicative of a frequency of the IF signal. A symbol represented by the IF signal can then be determined (28, 44) in response to the digital information.