Abstract: A digital equalizer has a digital filter. The digital filter is supplied with a digital input signal which corresponds to a multiplex signal composed of a plurality of signal components that are different in amplitude or phase and have the same frequency, and effects a computational digital filtering process on the supplied digital input signal. The digital filter is connected to a feedback circuit. The feedback circuit compares an output signal from the digital filter with a predetermined reference value signal. The feedback circuit has a multiplier which multiplies the output signal from the digital filter by a coefficient signal corresponding to an error of the output signal with respect to the predetermined reference value signal. Based on an output signal from the multiplier, the feedback circuit controls the amplitude of the output signal from the digital filter so as to be constant.

Abstract: An adaptive convergent decision feedback equalizer apparatus and method is disclosed for reducing intersymbol interference (ISI) in a data communication system. ISI is cancelled by generating and subtracting an estimation of the interference from a received signal. the estimation is generated by a N-tap transversal filter in which individual delayed received signals stored in the taps are multiplied by the respective adaptable tap coefficient and summed to form a digital representation of the ISI present. The present invention takes two steps to reduce the probability of coefficient adaptation from diverging. First, the DFE performs a coefficient modification only when the delayed received signal is a particular filter tap is a maximum or minimum level of the selected line code. A second step to eliminate divergence addresses the start up coefficient determination and errors in ISI estimation as the filter coefficients grow in size.

Abstract: A receiver for use in the port or portable units in a TDM/TDMA digital radio communications system is disclosed which incorporates an equalizer (107) to compensate for channel distortion due to multipath delay spread. Each received burst of information is oversampled at a multiple of the symbol rate and stored in a buffer memory (105). A joint estimator (106) processes the stored burst by operating on a known training sequence of bits within the burst to determine burst timing (where the burst actually begins) and the symbol timing (the optimum sample per oversampled symbol to be used for detection purposes). The estimator also determines whether the stored burst should be processed in a time-forward or time-reversed order.

Abstract: An automatic equalization apparatus useful for supplying an output signal of a transversal filter simultaneously to two juxtaposed comparators, one of the two comparators performing signal identification, the other of the two comparators detecting an equalization error with the reference level changed, and extracting data from resultant two kinds of data trains by taking at least (N-1)/2+1 bits as the unit, N being the number of taps of the transversal filter, performing correlation computation, and setting tap coefficients of the transversal filter on the basis of the resultant accumulated value.

Abstract: Adaptive decision feedback equalizer apparatus for processing information stored on disk or tape media or the like including a data input buffer (34), a gain acquisition circuit (42), a timing acquisition circuit (40) operative to generate timing error signals for controlling the sampling phase of the read signals input to the input buffer, a synchronizing circuit (44) for generating sync detect signals and polarity signals, an FIR filter (36) for generating linear filter output signals, register means (39), feedforward update logic (38) for adjusting the equalizer coefficient signals to develop undated coefficient signals, a dual ported RAM (50) for storing a plurality of the equalizer coefficient signals, feedback logic (48) responsive to the linear filter output signals, equalizer coefficient signals obtained from the RAM, and train data signals, and operative to compute the equalizer error signals and equalizer output signals, feedback update logic (52) for adjusting the values of the coefficient signals

Abstract: A multiple section cable equalizer with a signal level detector produces a clipping control signal for amplifiers in each equalizer section, so that a variable level input signal is restored to an equalized output signal that is free of distortion and attendant bit errors. A fixed reference clipping stage after the last equalizing stage produces a signal clipped to a final output level. A feedback path restores DC and low frequencies lost due to AC coupling. A test output stage permits monitoring of the operation of the equalizer stages. The signal level detector contains (in series), a differential amplifier with low pass filtering, a balanced modulator detector, a voltage amplifier, a comparator and peak detector, a transconductance amplifier and a plurality of current mirrors operatively connected to determine a difference current from the output of the transconductance amplifier and convert this to a clipping control signal voltage level.

Abstract: A frequency response equalizer, particularly for wideband networks, whose purpose is to reduce the influence of parasitic capacitances on the frequency behavior, includes the series arrangement of a first coil, a capacitor, a resistor and a second coil, in parallel with a series resistor, in which series arrangement the coils constitute a bifilarly wound transformer. The transformer includes two main inductances and two leakage sub-inductances, in series with the resistor and the capacitor, being arranged in parallel with the series resistor as an active series resonant circuit.

Abstract: A center tap of a transversal filter, which forms part of a forward equalizer, is shifted by at least one symbol interval. An error signal is generated using a decision output and tap outputs of the forward and backward equalizers. An impulse response estimation circuit is provided to receive the decision output of the predetermined tap signals of the forward equalizer. The forward equalizer is controlled in accordance with the channel response to effectively achieve adaptive equalization.

Abstract: A technique for generating the tap-weight coefficients for a signal dispersion cancelling filter utilizes circuitry which is responsive to received signal samples and generates a time-ordered sequence of derived signal samples. The tap-weight coefficient circuitry includes filters which operate in response to this sequence. One such filter is responsive to the derived signal samples in a first portion of the sequence after the time-order of the derived signal samples therein is reversed and another filter is responsive to the derived signal samples in a second predetermined portion of the sequence. This technique is applicable to a variety of communications systems including television and is particularly suitable for integrated circuit implementation.

Abstract: A frequency equalizer is provided for suitably correcting a frequency characteristic of a signal transmitted through a signal transmitting system such as a coaxial cable and the like. The frequency equalizer has a plurality of serially connected fundamental circuits in each of which an input signal is processed by a series circuit of a multiplying circuit and an amplifier having its own frequency characteristic to generate a first signal, the input signal is separately processed by an amplifier having a flat frequency characteristic to generate a second signal and the first and second signals are added or subtracted to derive an output signal. Therefore, a desired frequency characteristic can be corrected with ease only by setting the frequency characteristics of the plurality of fundamental circuits to proper frequency characteristics. Also, the circuit arrangement is formed of a building block system and therefore can be fabricated as an integrated circuit (IC).

Abstract: A method and apparatus are provided for adaptive equalization of distorted pulse signals with different pulse train speeds, particularly for bipolar signals. The edge time deviations of a signal derived from the pulses output from a variable equalization network are determined relative to a reference signal, and the results are used to selectively enable or disable individual circuit elements of the network in order to minimize the deviations. The circuit elements are controlled by a clocked binary counter, the counting direction of which is changed depending on the determined edge deviation change. The degree of equalization thusly achieved may be predetermined by presetting the count reading of the counter.

Abstract: An improved method for detecting that a facility delay has changed is provided. According to the invention, a facility having a delay that may change is coupled to a transmitter and a receiver. The transmitter is coupled to a first clock that transmits a first signal based on its current reading (the first clock signal) from time to time to the receiver via the facility. The receiver is coupled to a second clock that generates a second signal based on its current reading (the second clock signal) responsive to receiving the first clock signal. In operation, the first clock signal is fed downstream (via the facility having the delay), thereby triggering the second clock signal. The two clock signals are then detected and the difference in the two clock readings computed, thereby forming .DELTA..sub.n. The process is then repeated for successive first and second clock signals, thereby forming .DELTA..sub.n+1. The absolute value of .DELTA..sub.n -.DELTA..sub.

Abstract: A method of an apparatus for decision feedback equalization, capable of dealing with time reversal for the transmission characteristic arising in a course of equalization. Without a considerable increase of the number of taps used and the resulting reduction of the response speed. In this apparatus, a number of feedforward taps for providing a forward part and a number of feedback taps for providing a feedback part are controlled according to whether the transmission signal is to be read in a normal time direction or in a reversed time direction; the forward part and the feedback part are added; and the digital transmission signal is reconstructed according to a result of the addition.

Abstract: Coefficient drift, in fractionally-spaced equalizers, is constrained by combining a received data signal with a cyclostationary signal of the same symbol rate as the received data signal.

Abstract: An equalizer arrangement is used in a digital signal receiving system for the equalization of digital signals received in analog form and transmitted through an analog/digital converter, which have been distorted by a precursor and postcursor effects of previously transmitted or subsequent digital signals. The equalizer arrangement has a precursor equalizer followed by a postcursor equalizer connected with it.

Abstract: "An adaptive equalizer comprising a computer unit which receives a known signals sequence to estimate transmission channel characteristics and effect compensatory control of tap coefficients by use of a first algorithm that has fast convergence property, and a tap coefficient computing unit for making compensation for relatively slow changes in a random data input after the compensation for the transmission channel characteristics, which either employs an algorithm that involves a relatively low computational complexity or intermittently executes computation.

Abstract: A device for use in processing a device input signal carrying a digital symbol sequence, a reception filter filters the device input signal and produces a filter output signal having a high order curvature distortion. The high order curvature distortion results in a predetermined frequency band from adjacent interference on the predetermined frequency band by other frequency bands adjacant to the predetermined frequency band. Responsive to the filter output signal, an adaptive amplitude equalizing unit equalizes the high order curvature distortion and produces as a first equalized signal. When the device input signal decreases, the adaptive amplitude equalizing unit overestimates the high order curvature distortion to produce intersymbol interference because of appropriately suppressing the other freqency bands by the reception filter.

Abstract: An equalizer characteristic of an amplitude equalizer for use in a modulating and demodulating device (MODEM) can be set with considerable ease. One of a plurality of equalization characteristics assigned to an amplitude equalizer is set by generating and feeding to a transmission line a plurality of reference signals at the same level but with respectively-different frequencies. Each of such respective reference signals are received from the transmission line, separated, and measured as to its reception level. Level errors are then determined between each measured reception level and an estimated reception level previously determined in association with a respective one of the equalization characteristics. A selection and setting is then made of one of the equalization characteristics that is associated with one of the estimated receptions levels having the smallest level error.

Abstract: A transversal equalizer is realized by employing variable gain and delay in the amplification branches of a traveling wave amplifier. Specifically, by adjusting the gain and delay in each branch, the traveling wave type transversal equalizer may be adjusted to having a complementary frequency response in order to compensate for linear channel gain and phase ripples. This approach permits the transversal equalizer to be designed without the use of resistive splitter and combiner networks and, therefore, without the use of high gain amplifiers. Without such amplifiers, splitters and combiners, the smaller physical size, which is afforded thereby, allows the transversal equalizer to be easily assembled as a hybrid integrated circuit.

Abstract: A bipolar return-to-zero signal received from a communication channel (302) is sampled (402) to provide signal information that is processed (FIG. 5) to determine signal variation information. In accordance with this signal variation information, at least one operational parameter of an equalization system (400) is varied.

Abstract: A signal equalizing arrangement comprises a decision feedback equalizer formed by a feedforward filter section (16) connected to a feedback filter section (18) which includes a decision stage (20). If the performance of the equalizing arrangement as determined by the signal to noise ratio versus the bit error rate is found to be below the calculated optimum performance of the decision feedback equalizer, then an improved performance may be obtained by operating the equalizer in a time reverse mode. In order to operate the equalizer in a time reverse mode, a first last-in, first-out store (60) is connected in the signal path to the feedforward filter section (16) and a second last-in, first-out store (62) is connected to the output of the decision stage (20).

Abstract: An equalizer circuit suitable for selectively equalizing a transmission media operating at one of a number of different data rates has a number of equalizers, one for each data rate, connected in parallel to the media and a selectively operable means for disabling all but one of the equalizers.

Abstract: An adaptive equalizer for compensating input signal frequency and phase distortion introduced in the input signal transmission media is provided. The adaptive equalizer includes frequency selection means for generating an output signal of a selected frequency in response to the input signal and a feedback signal. A comparator slices the equalizer output at predetermined levels. A controller receives the comparator output and provides a controller output representative of the voltage level of the comparator output. A digital filter receives the controller output and generates a corresponding binary signal as the feedback signal to the frequency selection means.

Abstract: A device for protecting delay-line modulators of this type by detecting turn-off of the discharge thyristor by a comparator so as to prevent closing of the charge thyristor as long as the discharge thyristor is in the conducting state. This has the effect of preventing short-circuiting of the feed source.

Abstract: A digital pulse receiver is disclosed in which the transmitted signal is recovered from the received signal by using a decision feedback equalizer to estimate and then remove the intersymbol interference. A second decision feedback equalizer is used to estimate the timing of the sampling pulse. An optimum timing phase is derived by driving the sampling clock with a phase adjustment signal optimizing the amplitude of the sampling pulse relative to the next preceding pre-cursor pulse. The signal recovery decision feedback equalizer and the timing recovery decision feedback equalizer share the same tapped delay line to provide a fully digital pulse receiver operating at the baud rate to provide an optimum sampling phase.

Abstract: A preprocessing unit is inserted between a baseband converter and an equalizer/detector for performing a signal processing which corresponds to a phase rotation of the CPM-signal in the baseband represented by in phase and quadrature components. The phase rotation progresses in discrete steps of 90.degree. per bit interval of the binary data signal contained in the CPM-signal. The introduction of the preprocessing unit renders it possible to use a comparatively simple conventional equalizer/detector for binary pulse amplitude modulated signals (PAM-signals) for equalizing and detecting binary CPM-signals received in distorted form. When the equalizer/detector is adaptive, a further preprocessing unit is inserted between a channel estimator and adjusting inputs of the equalizer/detector.

Abstract: A waveform equalization method whereby a transversal filter having 5 or more tapes is included, and a difference signal output, which is obtained when an isolated impulse response waveform of a digital modulated signal is inputted to the above described filter and the output of the filter is inputted to an adder, is allowed to have intersymbol interference at .+-.T/2 with respect to the central axis time and has zero outputs at .+-.nT/2 (where n.gtoreq.2 and n is an integer).

Abstract: The theoretical coding gain associated with an error correction technique can be realized in a digital communications system employing this error correction by providing the equalization in the transmitter instead of the receiver. In a first embodiment, an automatic equalizer in the receiver of a digital communications system is adjusted using a training sequence. The equalizer coefficients for optimum adjustment are then transmitted back to the transmitter and supplied to an equalizer therein. After the training period is over, this transmitter equalizer, now having optimum coefficients, is activated and the receiver equalizer is disabled. In a second embodiment, the use of a training sequence can be eliminated and the receiver equalizer can be adjusted in response to actual data using "blind" equalization. The generated coefficients, as in the first embodiment, are then transmitted back to the transmitter.

Abstract: A non-intrusive channel-impairment analyzer is provided for measuring at least one quasi-static impairment characteristic of a band-limited data communications channel. The analyzer comprises a data receiver section and a measurement section. The data receiver section is arranged to receive data modulated onto quadrature phases of a carrier signal in two quadrature forward processing paths. The receiver section includes a data recovery circuit for effecting a decision as to the identity of the original data on the basis of the outputs from said processing paths, and decision-directed compensation means disposed in said paths and arranged to compensate for channel-impairment effects on the received signal. The measurement section is responsive to signals generated in the receiver section during the receipt of random data, to derive a measurement of at least one said channel impairment, such as phase or amplitude jitter.

Abstract: A decision feedback equalizer includes a transversal feedforward digital filter section (16) and a recursive feedback digital filter section (18) including a decision stage (20). In order to optimize the performance of the equalizer, the reference tap position is preferably aligned with a storage location of the feedforward filter section (16) containing the first sample of a current symbol and any contemporaneous samples of preceding symbols, the second and subsequent samples of the current symbol being contained in other storage locations of the feedforward filter section (16). In the case of data being in bursts a better performance may be obtained by time reversing the data applied to the feedforward filter section (16).

Abstract: A high speed, variable gain video preamplifier circuit disposed on a single IC which can accommodate multiple video input channels supplied by cables of varying length. A multiplexer 34 uses information about the cable length supplied to input pads to selectively connect the outputs of several series connected compensating amplifiers 42(a-b), 44 and 46 to the variable gain amplifier 36. The preamplifier circuit is characterized by a comparative wide common mode input range, as well as being capable of accepting two input channels and providing efficient cable compensation.

Abstract: In a receiver comprising a filter section for filtering a transmitted digital signal into a filtered digital signal and an equalizer section for equalizing the filtered digital signal into an equalized digital signal as a reproduced digital signal in response to controllable tap gains supplied from a control arrangement, the equalizer section comprises a first arrangement for filtering the filtered digital signal in response to predetermined ones of the controllable tap gains to produce an intermediate digital signal and a second arrangement for equalizing the intermediate digital signal into the equalized digital signal in response to remaining ones of the controllable tap gains except for the predetermined controllable tap gains to produce the reproduced digital signal.

Abstract: An improved auto-equalizer technique is disclosed for use in two-way communications systems having terminals which are connected by a communications link having distortion characteristics which are substantially identical for signals traveling in either direction. The technique includes a master modem which is always first to transmit in the system, and one or more remote modems. Each remote modem includes an adaptive filter in the receiver section of the modem which adaptively sets its filter characteristics to be the inverse of the line distortion characteristics. Each remote modem also includes a slave filter in the transmitter section which is also set have filter characteristics which are substantially the same as that of the adaptive filter. The slave filter acts to pre-distort the signals transmitted from the remote modem so that they arrive at the master modem substantially undistorted.

Abstract: This automatic equalizer comprises an automatic gain control circuit (2, 4) tending to keep the peak amplitude of the equalized signal constant, together with a variable equalization network (1) provided with a control input enabling the slope of its gain transfer characteristic to be modified without altering the value of its gain at the half Baud frequency, and a servo-control system for controlling the shaping of the frequency spectrum by controlling said variable equalization network, said servo-control system including a circuit (6) for detecting the mean phase error of zero crossings in the skirts of pulses appearing in the received and equalized digital transmission signal compared with the middles of Baud intervals.

Abstract: An adaptive time-discrete filter having an impulse response h(i) with i=0,1,2, . . . for forming a cancelling signal from synchronous data symbols (for example to cancel echoes or lagging intersymbol interference) comprises a transversal filter section (12) having adjustable coefficients C.sub.i with i=0,1,2, . . . , N-1 for realizing the first N values h(i) of the impulse response as well as a recursive filter section (12') for realizing the values h(i) with i=N,N+1, . . . . The recursive filter section (12') receives the input signal delayed over N-1 discrete time intervals from the adaptive filter as an input signal x(n) and forms an output signal y(n) according to the relationship:y(n)=C.sub.B [C.sub.A .times.(n-1)+y(n-1)]where C.sub.A is equal to the last adjustable coefficient C.sub.N-1 of the transversal filter section (12) and C.sub.B is a predetermined fixed coefficient.

Abstract: Apparatus and method for amplitude equalization of a signal channel such as a telephone line that does not require adjustments at the customer's premises. The equalization circuit receives a plurality of alignment signals at predetermined frequencies from the signal channel, and measures the amplitude of each alignment signal. The amplitudes are used to determine analog and digital filter transfer function coefficients. Thereafter, input signals on the signal channel are filtered such that the combined amplitude response of the signal channel and filter is substantially flat over a designated frequency range.

Abstract: In a modem receiver having a fixed sample rate relative to incoming symbols and a tapped delay adaptive equalizer with fractional tap spacing, coefficients used in the equalization computations are rotated relative to a reference tap in order to compensate for relative drift between incoming signals, representing real (i.e. non-training) data, and the clock controlling sampling. By itself, such rotation would tend to distort received data by shifting the sampling phase away from the center of the received symbols. Logic means included herewith operates to prevent such distortion, so that the integrity of the data output of the receiver is unaffected by the rotation. In the disclosed embodiment, such logic means operates to shift the phase of the "sum of products" computation (product of data and tap coefficients) relative to the flow of data into the fractionally spaced delay network.

Abstract: A digital wireless subscriber telephone unit for wireless connection with a base station. The subscriber unit has a baseband processor which is coupled to storage device for the baseband functions. The baseband processor is direct access coupled to a modem processor whereby the two processors may communicate with each other. The modem processor generally acts as the master in the system, although lock-out circuit may be used in certain circumstances. The signal from the modem processor is converted to an analog signal, which is subjected to deglitching, and the deglitched signal is then upconverted and filtered to form an IF signal which is thereafter amplified. The amplified IF signal is combined with a signal generated by a synthesizer to provide an RF signal. On the basis of certain signals received from the base station, the baseband processor produces initiating signals which determine whether the subscriber unit will be in the transmit mode or the receive mode.

Abstract: An amplitude equalizer which adds the outputs of two circuit means having opposite characteristics, whereby a flat delay-frequency characteristic and powerful frequency-amplitude characteristic are obtained. Further, a variable amplitude equalizer including two of the same connected in parallel and a variable attenuator inserted in one of the parallel paths. Still further, an automatic amplitude equalizer wherein the variable attenuator is feedback controlled by an equalization residual. The amplitude equalizer includes a minimum phase circuit and non-minimum phase circuit connected in series.

Abstract: Apparatus for suppressing intersymbol interference and improving the signal-to-noise ratio in a digital line amplifier includes a filter with a fixed transfer function that couples equalized digital signals to a first differential input of a difference amplifier and substantially filters out high frequency random noise present in the signals to achieve signal-to-noise enhancement with consequent degradation of the signals by intersymbol interference. Subsequently, an output from the amplifier is sampled by a quantizer that produces a bit stream output of portions of the enhanced signals, excluding the intersymbol interference.

Abstract: The transmitter (DTR) and the receiver (DRC) of a system for transmitting data signals at a given symbol rate 1/T comprise discrete-time smearing filters (SM and DSM) for combatting the effect of additive pulse-like disturbances (p'(t)) in the transmission channel (TCH). In many cases these disturbances (p'(t)) turn out to have a pronounced bandwidth-limited nature. By utilizing this feature the implementation of the smearing filters (SM and DSM) is simplfied and/or their performance level is improved in that the non-zero values of their impulse responses s(i) and d(j) only occur at the points of grids of the indices i and j recurring with a period of L, where L is an integer greater than 1 and where L is determined substantially by the ratio L.sub.0 of the symbol rate 1/T to twice the highest significant frequency f.sub.m of these disturbances (p'(t)).

Abstract: An adaptive blind equalization method and device uses self-decisions both in the convergence phase and the steady-state phase, making it possible to obtain a good and smooth adaptation in the convergence phase and a low error probability for the decided symbols in the steady state phase. By using the self-decided error and a reference error, a binary consent function is constructed which tells when it is allowed to proceed with the adaptation and when the adaptation should not be used. The binary consent function compares the self-decided error sign with the reference error sign and is based on the discovery that in certain areas of the symbol constellation plane, when the signs of the previous errors are equal, there is a high probability that the self-decided error signs and true error signs (unknown) will also be equal.

Abstract: An automatic amplifying and equalizing circuit for bipolar data signals has first and second voltage controlled amplifiers controlled by the output of a peak detector. The first amplifier provides even amplification of frequency spectrum components of the data signals while the second amplifier provides amplification of only higher frequency spectrum components of the data signals to compensate for losses of differing length transmission lines. Switches in filtering and frequency dependent circuits provide for operation at several data rates.

Abstract: A line equalizer for eliminating a precursor interference component and postcursor interference components from a pulse signal inputted from a transmission line. A precursor equalizer takes a sum of a signal derived from the input pulse signal retarded by a fundamental period and a signal derived from the input pulse signal multiplied by a coefficient a. A decision circuit decides the threshold level of an output pulse signal from the precursor equalizer to output a predetermined signal. A controller controls the coefficient a of the precursor equalizer on the basis of the signal from the decision circuit, etc.

Abstract: The n symbols of a codeword of length n are transmitted on n separate channels or frequencies simultaneously. A receiver includes n equalizers that are adapted to receive information from respective ones of the n channels. The outputs of the n equalizers are applied to n inputs of an error correcting decoder which produces the original version of the transmitted codeword. The n equalizers include n feedforward and n feedback transversal filters whose taps are updated by n tap update processors in accordance with a Kalman algorithm, or the like, once each codeword time. The feedforward registers contain successively received signal samples of each of the n channels while the n decision feedback registers contain successively corrected symbols generated at each of the n decoder outputs.

Abstract: Plural n-symbol codewords are helically interleaved and transmitted in a stream. A receiver views the transmitted stream through n time windows, each time window having a length accommodating the longest anticipated decorrelation time of the channel. Individual equalizers process the data in individual windows. The n windows simultaneously furnish the n symbols of each codeword to an error correction decoder. The n equalizers respond to feedback in which the output of the decoder is substituted in place of undecoded symbols from the n windows whenever available.

Abstract: A data communication equipment equalizer which minimizes the total training time delay (RTS-CTS) is disclosed. The total RTS-CTS delay of the provided equalizer consists of a delay due to a minimal training sequence required for the equalizer coefficients to converge given a low distortion channel, plus whatever delay is necessary for the equalizer coefficients to converge given the particular channel.

Abstract: The present invention relates to a radio transmission system. The system includes a transversal type automatic equalizer which controls tap weight based on bit error rate (BER) from a pseudo error pulse. In the equalizer, the threshold value (BER1) which defines the mode change for tap weighting control from normal to reset is different from the threshold value (BER2) from reset to normal. Therefore, the mode change is carried out by a simple circuit properly and stably.

Abstract: An adaptive frequency range equalizer for digital radio relay systems which require adaptive frequency range equalizers which have coefficients that are adjustable. That are different possibilities for setting the coefficients of the transversal filter in such equalizers in a manner such that the transmission function of the transversal filter is either of the minimum phase type (mp), or the linear phase type (lp) or the non-minimum phase type (mnp). The invention discloses a method and apparatus for obtaining either of the three transmission functions for the transversal filter.

Abstract: Operation of a decision feedback equalizer is enhanced by measuring the intersymbol interference precursor effect on each symbol decision output and utilizing that measurement information to update equalizer, transversal filter, tap multiplier coefficients in a direction to reduce the precursor and postcursor effects. In one embodiment, the updated coefficient information is further utilized to adjust equalizer input signal sampling phase toward a time of maximum data signal eye opening.