Abstract: The present invention is intended to converge tap coefficients of an equalizer at high speed with high accuracy by a small number of calculations. An automatic equalizing filter of the invention comprises a synchronizing data detecting circuit for detecting a synchronizing portion from a data sequence of a reception signal, an equalizer, a tap coefficient determining for determining tap coefficients (C.sub.0, C.sub.1, C.sub.2, . . . , C.sub.n) of the equalizer and an impulse response estimating for estimating an impulse response on the basis of a cross-correlation function provided between the synchronizing portion and a previously-designated synchronizing pattern, thereby setting initial values of the tap coefficients (C.sub.0, C.sub.1, C.sub.2, . . . , C.sub.n) of the equalizer on the basis of the impulse response estimated from this impulse response estimating.

Abstract: A facsimile apparatus determines whether a frame to be transmitted is an image block or an error retransmission frame, and transmits a short training sequence or a long training sequence based on the results of the determination. The long training sequence is sent if a TCF signal is transmitted and the short training sequence is sent if the image block is transmitted. If the facsimile apparatus is on the receiving side, a training sequence in accordance with the frame from the transmitting side is received. After a carrier signal is detected, the apparatus then makes a transition to a mode for receiving the TCF signal or image block.

Abstract: A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). The hybrid DFE structure is designed so that one form of tap values dominates over the other. This allows only the dominate tap values to be used by the transmitter during precoding and reduces the transmitter complexity. In particular, a hybrid DFE is designed so that the I(z) coefficient values dominate over the N(z) coefficient values, where the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively. A respective Tomlinson precoding scheme in the transmitter uses only the I(z) values. Since only the I(z) values are used in the precoder of the transmitter, the NP-DFE of the receiver is kept active during the communications phase.

Abstract: In a quaded cable, coupling between circuits (side circuit 1, side circuit 2, and phantom circuit) is compensated for at the receiving end of a transmission system. By transmitting known signals from the transmission end separately on each circuit, coupling between circuits is initially estimated by measuring the signals received at the opposite end on each of the circuits. Following startup, during data transmission the received data signals are modified in accordance with this initially determined coupling between circuits to produce estimated transmitted data signals. During data transmission the coupling between circuits is reestimated by storing (303) N data signals received on each circuit and the corresponding N estimated transmitted data signals on each circuit. The coupling between circuits is determined as a function of the covariance of these N received signals on each circuit and the covariance of these N estimated transmitted data signals on each circuit.

Abstract: An adaptive equalizing system equalizes an unequalized signal and performs carrier recovery for use in a digital communication receiver. An equalizing coefficient is initialized by a constant modulus algorithm (CMA) and the initialized equalizing coefficient is more finely updated by a stop-and-go algorithm (SGA). When the convergency by the CMA reaches a predetermined threshold value, carrier recovery is performed, while when an average value of the phase error during performing the carrier recovery is less than another predetermined threshold value, the equalizing algorithm is converted into the SGA. Thus, the adaptive equalizing apparatus can equalize the received signal more simply and reliably.

Abstract: An adaptive equalizer includes a multiplier for multiplying, by corrective data, an output signal from a filter unit for compensating for a signal distortion to which input digital data are subjected, a decision unit for estimating and outputting symbols of output data from the multiplier, a subtractor for subtracting an output signal of the decision unit from the output data from the multiplier, multipliers for inversely correcting the output signals from the decision unit and the subtractor which are corrected by the multiplier, a coefficient updating unit for updating the coefficients of the filter unit based on an output signal from the multiplier which inversely corrects the output signal from the subtractor, and a frequency offset estimating unit for estimating corrective data based on a frequency offset on the basis of the output signal from the multiplier which inversely corrects the output signal from the subtractor, and using the estimated corrective data as corrective data for the multiplier which

Abstract: An autobaud detection mechanism, installed as part of the communication control software of a serial communication device's microcontroller, enables the device to automatically determine the baud rate employed by a remote digital data communications device. Starting with a default baud rate, corresponding to the highest available baud rate, the mechanism steps through successively lower baud rates in the course of a search for the baud rate at which the remote device is transmitting. When an incoming call is received, respective bits of the received data are examined for the presence of transmission errors. If a transmission error is detected, the baud rate is stepped to the next lowest baud rate. If no error is detected, the received data bits are compared with a reference character. If the two compared data bit patterns match, the controller locks the baud rate at that baud setting for the remainder of the call. When the call is terminated, the baud rate reverts to its default setting.

Abstract: In radio phone systems with a digital cellular design currently used a training sequence of constant length, consisting of an guard part and a reference part, is included in a transmission burst between a base station and a mobile station. With the aid of a received training sequence, the receiver calculates the impulse response of the channel and is thereafter adapted into the channel. The quality of the connection can, according to the invention, be enhanced in that the training sequence is made adaptive, whereby the lengths of the guard part and the reference part may vary while the total length of the training sequence remains the same. According to another embodiment, also the total length of the training sequence is changed.

Abstract: A receiver capable of effecting frame synchronization control even at the time of initial acquisition and hand off in the presence of frequency selective fading.

Abstract: The present invention includes an optimized equalizer (22) used to equalize a signal (at 20) received from a distorting channel (18). First, auto and cross correlations of a predetermined training sequence and the received signal are generated (at 21c). The correlations are then used to generate a solution matrix (21d). An eigenvector associated with a maximum eigenvalue of a function of the correlations is formed (21e) using the solution matrix (21d) and then used to generate equalizer control signals (21f) or parameters defining taps of a filter implementing the equalizer (22).

Abstract: An adaptive equalizer detects characteristics of a transmission line in radio and cable communications and equalizes received signals by using the detected results. Equalization is for not only linear distortion but also nonlinear distortion in accordance with variation of characteristics of the transmission line. The adaptive equalizer includes a characteristic detection unit 11 for detecting real part and imaginary parts of a transfer function by using an output signal corresponding to an input signal of an object to be equalized to compensate for deterioration, for example a transmission line; and an equalizing unit 12 for equalizing an output signal of the object to be equalized 10 in accordance with an unknown input signal by using the detected result of the characteristic detection unit 11.

Abstract: An adaptive communications receiver for data-transmission which comprises a channel estimator and sequence estimator. The channel estimator consists of a recursive least squares algorithm which uses a known training signal or past decisions to provide a channel estimate. The sequence estimator consists of a new recursive algorithm which uses the channel estimate to estimate the information sequence transmitted over the channel. The receiver exploits the commonality between the sequence and channel estimator to provide an efficient implementation. The receiver can have varying degrees of non-linearity and is lower in complexity and more robust than linear or decision feedback equalizers in the presence of channel mismatch.

Abstract: A method and an apparatus for equalizing received transmission signals including at least a sync word and arbitrary data in a slot is disclosed. Data of a current slot are equalized in a reverse direction, using a sync word of a slot next to the current slot to be equalized. Data downstream of an error site under an extremely adverse condition may be equalized even if such error site exists in the slot being equalized.

Abstract: An automatic equalizer includes a transversal filter having delay elements with N+1 taps and N+1 multipliers for outputting an output signal Y.sub.n which is described by the following formula (A) depending on a modulated input signal X.sub.n which is received via a transmission path and a coefficient C.sub.i.sup.(n) of each of the multipliers which are arranged in a sequence such that an integer i increases from -(N/2) to (N/2) towards latter stages of the delay elements, ##EQU1## a gain controller for multiplying a gain coefficient g.sup.(n) to the output signal Y.sub.n of the transversal filter to produce an equalizer output, and a control circuit responsive to the equalizer output for variably setting the coefficient C.sub.i.sup.(n) of the transversal filter means described by the following formula (B) and the gain coefficient g.sup.(n) of the gain controller described by the following formula (C)C.sub.i.sup.(n+1) =C.sub.i.sup.(n) +.alpha.E.sub.n.sup.* X.sub.n-i-(N/2)(B)g.sup.(n) =g.sup.(n) +.tau.E.sub.n.

Abstract: Adaptive equalization system for allowing the equalization of a base-band line of a DCE, includes an adaptive filter for adjusting its coefficients in accordance with an adaptive algorithm. The equalizer includes controls to work during a preliminary period, in an adaptive or non-adaptive mode according to the convergence of the recursive algorithm process. The algorithm is triggered depending on whether the equalized signal belongs to one of several predefined intervals of convergence. After this preliminary period, when the mean square of the residual error is considered small enough to ensure the convergence of the adaptive process, the algorithm is computed on a continuous mode.

Abstract: Adaptive equalizers and processing methods wherein data required to implement an adaptation algorithm is sampled at a rate that is significantly lower than the symbol rate. The adaptation algorithm is processed at this reduced rate, in that updated tap coefficients, sample timing errors and symbol clock error signals are computed at this reduced rate. An advantage of the adaptive equalizer and processing method of the present invention is that the adaptation algorithm may be implemented in equipment that operates at a clock rate that is much less then the symbol rate. In particular, the adaptation algorithm may be computed using software that is resident in inexpensive general purpose digital processor, such as a personal computer, for example.