Abstract: A blind multipath equalizer for a digital communication channel is disclosed. The equalizer includes a sparse digital filter, responsive to a source of a received signal including a digital data signal, and including a plurality of taps, each responsive to a tap coefficient and time displacement, which produces a multipath corrected digital output signal. A filter controller is responsive to the received signal for detecting a multipath signal by calculating the autocorrelation of the received signal, detecting a multipath signal based on the autocorrelation and supplying a tap coefficient and time displacement to one of the plurality of taps to cancel the detected multipath signal.

Abstract: An equalizer (100) is suitable for removing the delay distortion from a switched digital signal received from a telephone channel, where the delay distortion is caused by a bridge-tap connected to the telephone channel. The equalizer includes a feedback delay circuit (200) which is arranged to delay the output signal (150) by an amount of time based on the square of the predominant frequency of the output signal. The resulting delayed feedback signal (130) is then combined with the input signal, thereby compensating for the delay distortion. The equalizer also includes an amplifier (103) which may be adjusted to compensate for the attenuation distortion caused by the bridge-tap.

Abstract: A cable equalizer (10) receives signals transmitted over a coaxial cable (12) at a multi-path simulator (14). The multi-path simulator (14) includes a splitter (16) that places the signal along a first path (26) and a second path (28), wherein the signal on the first path (26) is 180.degree. out of phase with the signal along the second path (28). The signal along the first path (26) propagates to a combiner circuit (18). The signal along the second path (28) propagates through a delay circuit (20) having a delay value of .tau. that determines the notch spacing of the equalized signal. The signal along second path 28 propagates from delay circuit 20 to a variable attenuator circuit (22) that determines the notch depth for the equalized signal. The combiner (18) receives the signal along the first path (26) and the second path (28) and generates an equalized signal at the output of the multi-path simulator (14).

Abstract: An adaptive equalizer includes a digital linear filter having adjustable weighting factors and which is connected to a summator and a control unit so as to form two filter loops, one direct and the other recursive, the filter being shared in both loops. The control unit provides a weighting factor which establishes a selected relative proportioning of the data signals which traverse each loop, so that the equalizer is proportioned as to the degree to which it provides direct filtering and the degree to which it provides recursive filtering. Recursive filtering is employed to the maximum extent consistent with operating stability, the relative proportion of direct filtering being increased as necessary in order to maintain stability during equalization of any particular received data signal.

Abstract: A decision feedback equalizer is suitable for use with a bipolar return-to-zero receiver. The equalizer determines an output Y(n) (160) based on a compensated received value X(n) (104) and a correction factor, D(n) (141 ). After receiving X(n), the equalizer retrieves a stored value D(n) corresponding to the k prior output values Y(n-1), . . . , Y(n-k) from a memory device (140). The equalizer then forms an equalized received value X'(n) (107) based on combining X(n) with D(n). The equalizer then determines the output value Y(n) based on comparing X'(n) with a positive threshold, V1 and a negative threshold, V2. When Y(n) is determined to be zero, the equalizer adjusts the stored correction value D(n) by a predetermined value, .DELTA., based on whether X'(n) is positive or negative.

Abstract: In an adaptive equalizing apparatus using quantized feedback, when the tap coefficients of a FIR filter are suddenly decreased due to a large noise input, or when the input signal level is suddenly lowered, the level of the input signal to the quantized feedback circuit becomes low, and the quantized feedback circuit malfunctions. Since the result of the quantized feedback circuit is utilized in the adaptive equalizing apparatus, the adaptive equalizing apparatus malfunctions, and cannot be restored to the normal operating state. To prevent the malfunction of the adaptive equalizing apparatus, as the first measure, limiters are inserted in the input lines of the tap coefficients of the FIR filter, the level of the signal entering the quantized feedback circuit is limited so as not to be lower than a specific value, thereby preventing the quantized feedback circuit from malfunctioning.

Abstract: A ferroelectric phase shifter for shifting the phase of a radio frequency F) signal. The phase shifter includes a conductor line, a ground plane and a ferroelectric element between the conductor line and the ground plane to form a microstrip circuit through which the RF signal propagates. The ferroelectric element has a dielectric constant that can be varied as a function of a DC voltage applied to the ferroelectric element wherein the speed of the RF signal propagating through the ferroelectric element is a function of the dielectric constant. The phase shifter further includes a DC voltage source connected across the conductor line and the ground plane. The DC voltage source applies a variable DC voltage to the ferroelectric element in response to a control signal thereby to vary the dielectric constant of the ferroelectric element.

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: An improved adaptive three tap transversal equalizer for partial-response signaling. The invention reduces the complexity of the hardware, as well as reducing the sensitivity of the equalizer to gain and timing errors. The present invention employs an algorithm based on sample values around zero. The resulting decrease in average magnitude of the error results in decreased sensitivity to gain errors. The algorithm of the present invention improves cancellation of sample timing errors. In the present invention, the coefficient of an adaptive cosine equalizer is updated by integration of a stochastic gradient. To calculate the gradient, the product of the quantized output from the previous sample and the output from the present sample is summed together with the product of the output from the previous sample and the quantized output from the present sample. In addition, the equalizer output is masked such that values quantizing to non-zero values are discarded in the update algorithm.

Abstract: Adaptive analog equalizer permitting 16 Mbit/s token ring (TR) transmission over unshielded twisted-pair (UTP) cables. The equalizer (29) is located at the wiring concentrator (25), and consists of a variable and a fixed filter section. The existing TR receiver (49) and transmitter (53) remain unchanged. To compensate for distortion introduced by the cable section (19b) preceding the equalizer, the level of the signal (B) at the equalizer output (35) is used as a control criterion. The additional distortion contributed by the cable section (21a) following the equalizer is accounted for by measuring the level of the signal (D) received from the transmitter (53) of the next TR station. By these two measurements, the equalizer is adjusted such that the cable-length dependent distortion is eliminated at the next receiver (49).

Abstract: An automatic equalizer has a circuit for sensing cable effects that generates a control signal for a variable equalizer. A digital signal from a transmission channel is input to the variable equalizer to produce an equalized digital signal as a function of the control signal. The equalized digital signal is input to the sensing circuit which detects over-shoot or under-shoot of transitions in the equalized digital signal and adjusts the control signal accordingly to produce a balance in the transitions.

Abstract: A system and a method for dispersion compensation in fiber optic high speed systems, the dispersion compensation being carried out in the transmitter. The system comprises a modulating device for modulating an information-carrying electric signal, an equalizing device for equalizing the signal modulated in the modulation device, and an electro-optic translating device for translating the signal equalized in the equalizing device into an optical signal substantially without loss of information and with substantially maintained phase and amplitude properties.

Abstract: In an equalizer including a plurality of delay elements, a plurality of weighting elements and an adder, the impulse response of a signal transmission channel is estimated to selectively switch over a plurality of selector switches associated with the inputs and outputs of the respective delay elements, thereby selectively changing the combination of the delay elements and the weighting elements transmitting an input signal from the channel to the adder and also changing the combination of the adder and a delay element feeding back the output of the discriminator to the adder. Thus, the number of required taps of the equalizer can be reduced, so that the power consumption and size of the equalizer can be reduced.

Abstract: A correction system for transmission lines includes a structure adapted to automatically correct the attenuation of the DC component of any signal traveling on the line and a device adapted to correct the attenuation of the various frequency components of said signal, wherein the structure for correcting the attenuation of frequency components includes an automatic correction circuit.

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 electronic microwave calibration device provides an electronic load connected to each of two ports of a vector network analyzer. The load comprises a plurality of PIN diodes interconnected by transmission line. Each of the diodes are biased to generate different loads or conditions at each of the two ports. A control computer controls the biasing of diodes according to a predetermined procedure and compares impedance values measured at each of the two ports by the network analyzer to known values stored by the control computer. The control computer thereby derives calibration coefficients that are stored in the network analyzer and used by the network analyzer in performing further measurements.

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: An automatic equalizer is used in a radio transmission path for improving convergent characteristics of a control loop in an automatic equalizing mode when the amplitude ratio of reflected and direct waves is greater than 1. The automatic equalizer has an adaptive matched filter, a decision feedback equalizer, and a reset control circuit for outputting first and second reset signals, respectively, to the adaptive matched filter and the decision feedback equalizer when an asynchronous condition is detected. After the first and second reset signals are generated, thereby resetting the adaptive matched filter and the decision feedback equalizer simultaneously, the first reset signal is eliminated before the second reset signal is eliminated. The decision feedback equalizer is thus brought into the automatic equalizing mode after the adaptive matched filter has entered the automatic equalizing mode and symmetrized impulse responses.

Abstract: An adaptive filter or equalizer for digital data communication includes, a first cascade circuit connected to operate as a digital finite impulse response (FIR) filter, the first cascade circuit having a first plurality of input taps for application of filter weighting signals thereto, a single input for samples of input data, and an output for filtered data. A second cascade circuit, which has the inverse canonical form, has a second plurality of input taps for receiving signal samples of input data, a single input for receiving error signals, and an output for yielding a succession of weighting signals. A sequencing circuit applies data signals to successive cascade stages of the second cascade circuit in a time sequence which is the reverse of that of the weight signals applied to the plurality of input taps of the first cascade circuit, such that the second cascade circuit functions as a weighting signal generator for the first cascade circuit.

Abstract: A synchronous data interface circuit which is reduced in scale and low in power consumption is provided. A bit clock amplitude detector measures the amplitude of a bit clock signal transmitted thereto through a signal line and outputs to a set of equalizers a signal representing a ratio corresponding to the measured amplitude. The equalizers also respectively receive an NRZ data signal, a frame signal and a bit clock signal on lines of the same length and made of the same material. The equalizers thus individually set equalizing amounts and compensate for amplitude distortion of the individual signals. In this instance, each equalizing amount is set in accordance with the signal received from the bit clock amplitude detector. Discriminators receive signals after this amplitude compensation and reproduce the original signals as output.

Abstract: In an interference canceller, a feedforward filter receives an input signal to produce an equalized feedforward output signal in which CW interference is cancelled and a feedback filter receives the output of a decision circuit to produce an equalized feedback output signal. The equalized feedforward and feedback output signals are combined together to cancel intersymbol interference before being applied to the decision circuit. First tap-gain control circuits derive first tap-gain signals from a decision error and signals at the first delay-line taps and respectively apply these signals to the first tap-gain multipliers. Second tap-gain control circuits derive second tap-gain signals from the decision error and signals at the second delay-line taps and respectively apply these signals to the second tap-gain multipliers. A complex correlation is detected between signals at opposite ends of the first tapped delay line and compared with a threshold.

Abstract: A clock signal distribution network in a microprocessor of a computer system for distributing a global clock signal to a plurality of units of the microprocessor includes a clock generator for generating a first clock signal with an input delay. A phase locked loop circuit generates a controllable delay to the first clock signal to become the global clock signal. A clock driver drives the global clock signal to the plurality of units. An electrical connector includes a plurality of connection lines for coupling the global clock signal to the plurality of units. A length equalizer equalizes the signal transfer delay of each of the plurality of connection lines such that the global clock signal reaches each of the plurality of units via each of the plurality of connection lines at the same time. Each of the plurality of units includes an area buffer for standardizing its input load to the clock driver. A dummy buffer introduces the input delay of the clock generator to the global clock signal.

Abstract: According to the present invention, a large compensation effect can be obtained in a small operation volume regardless of which one of a distortion due to a frequency selective fading and a distortion due to an interference of adjacent waves is ruling. In the present invention, a principal wave signal and signals of channels adjacent to both sides of said principal wave are taken out, and power of these signals is compared to select either one of the fractional interval equalizer and the linear decision feedback equalizer.

Abstract: A data receiving apparatus capable of correctly obtaining decoded data of a received signal even if the center frequency of the received signal has a frequency shift and the state of transmission line changes with time. The coefficient of an equalizer is calculated basing upon an error signal obtained from the received signal and a shift of the center frequency obtained from the error signal. The coefficient is renewed each time a new received signal is supplied.

Abstract: To compensate for nonlinear signal distortions in analog optical communication transmission systems, caused by laser chirps and the chromatic dispersion of the optical fiber, an equalizer in the form of an LC component is known, whose capacitance is formed by a variable capacitance diode. However, the known equalizer functions only when the capacitance has the proper polarity, which cannot be predicted because of possible polarity inversion during signal transmission. According to the invention, the variable capacitance diode (C.sub.a) has another variable capacitance diode (C.sub.b), with the opposite polarity, connected in parallel, and is equally biased in the high-resistance direction. By adjusting the bias voltage of both capacitances, it can be achieved that one of the two variable capacitance diodes takes over the equalization function, and the other is practically inoperative.

Abstract: A receiver for digital radio communications has an equalizer which is powered off for reduced power consumption when received radio waves undergo relatively small intersymbol interference. When intersymbol interference is significantly large, the equalizer is powered on to remove the intersymbol interference for better signal reception. The receiver has a signal quality decision circuit which powers on the equalizer when the quality of the received signal is poor, and powers off the equalizer when the quality of the received signal is good. The receiver consumes a relatively small amount of electric power overall.

Abstract: In a receiver an apparatus and method substantially reduces time dispersion and multipath distortion in a received signal. An equalizer (109), including taps having gain coefficients, produces an equalized signal (110) responsive to the received signal (107) and an adaptive process signal (137), wherein the gain coefficients are adjusted responsive to the adaptive process signal (137). A first mixer (111) mixes the equalized signal (110) and a reference carrier signal (115) to produce a recovered modulated signal (119). A detector (112) detects an estimate signal (129) responsive to the recovered modulated signal (119). An error signal generator (139) generates an error signal (141) responsive to a difference between the recovered modulated signal (119) and the estimate signal (129). A second mixer (147) mixes the error signal (141) and the reference carrier signal (115) to produce the adaptive process signal (137).

Abstract: Timing recovery circuitry for recovering digital data generates a timing signal which is a function of the delay provided by an equalizer to one or more predetermined frequency components of its input signal. Advantageously, this approach is applicable to systems which utilize one or more baseband or passband equalizers. The disclosed embodiments of the present invention pertain to a dual-duplex system. In such a system, the digital data to be transmitted is divided into two different digital signals and each signal is coupled through an associated transmission channel. At the receiver, the received version of each transmitted signal is processed by an associated equalizer and the outputs therefrom are combined to recover the digital data. In the disclosed embodiments of the present invention, the necessary timing signal for such recovery is a function of the delay introduced by each equalizer to at least one predetermined frequency component of that equalizer's input signal.

Abstract: An adaptive feedforward equalizer (12) has switched (N-1) tap-gain coefficients and a fixed tap-gain coefficient for the reference delay-line tap to operate on an incoming IF or baseband signal according to a first error signal (.epsilon..sub.1) representative of the difference between the input and output of a decision circuit (15). All tap-gain coefficients are active in the absence of an interference from an undesired source to cancel precursor distortion. The (N-1) tap-gain coefficients are nullified when such an interference is detected to reduce its precursor-cancelling capability. A first feedback equalizer (17) operates on the output of the decision circuit according to the first error signal to cancel postcursor distortion. A second feedback equalizer (18) nonlinearly filters the output of the decision circuit according to a second error signal (.epsilon..sub.2) and generates an estimate of a desired component of the output of the feedforward equalizer.

Abstract: In an automatic cable attenuation compensation system comprising a fixed compensation part (FC-R/G/B) providing a stepwise adjustable attenuation compensation for substantially compensating cable attenuation, the stepwise adjustable attenuation compensation of the fixed compensation part being set after power-up, an adaptive compensation part (VC-R/G/B) is provided for a continuously active compensation for a further accurate compensation of the cable attenuation.

Abstract: Pulse width controlled adaptive equalizers are provided for telecommunication signals which are routed over coaxial cables. The adaptive equalizers operate on the premise that a coaxial cable degrades a telecommunications signal by widening the pulse of the signal and decreasing the amplitude. The longer the cable is, the wider the pulse gets. Thus, by detecting the width of the pulse against a desired width, and feeding back the difference to a variable filter which can correct the pulse width, a pulse width controlled adaptive equalizer can be provided.

Abstract: A radio receiver's digital matched filter (52') is intended to match a pulse-shaping filter (23) in the transmitter whose signals it receives. However, the clock signal on which the matched filter's timing is based is generated by a receiver clock (58') that is independent of the transmitter clock (56) and that is subjected to no timing adjustment to bring the two clock signals into synchronism. So as to ensure that the matched and pulse-shaping filters work together as a Nyquist filter, therefore, a timing-recovery circuit (60') senses the timing offset in the matched filter's output, and a coefficient generator (80) adjusts the matched filter's coefficients in such a manner that the filter itself imposes the delay needed for the required timing relationship between the filters.

Abstract: A clock signal distribution network in a microprocessor for distributing a global clock signal to a plurality of units of the microprocessor includes a clock generator for generating a first clock signal with an input delay. A phase locked loop circuit generates a controllable delay to the first clock signal to become the global clock signal. A clock driver drives the global clock signal to the plurality of units. An electrical connector includes a plurality of connection lines for coupling the global clock signal to the plurality of units. A length equalizer equalizes the signal transfer delay of each of the plurality of connection lines such that the global clock signal reaches each of the plurality of units via each of the plurality of connection lines at the same time. Each of the plurality of units includes an area buffer for standardizing its input load to the clock driver. A dummy buffer introduces the input delay of the clock generator to the global clock signal.

Abstract: For use in combination with a demodulator (23) for demodulating a received signal susceptible to fading into a demodulated signal, an adaptive equalizer comprises a fading detecting circuit (51) for detecting the received signal to produce a detection signal representative of a magnitude of the fading. Into a processed signal and supplied with the detection signal, an equalizer multiplier (53) processes an equalized signal produced in an equalizer section (25, 26 and 27) which is for carrying out a predetermined equalization operation. In accordance with the processed signal, an automatic gain control circuit (52) modifies the demodulated signal into a modified signal on which the predetermined equalization operation is carried out.

Abstract: To compensate for nonlinear distortions in analog optical communication transmission systems, caused by laser chirps and the chromatic dispersion of the optical fiber, an equalizer in the form of an LC component is known, whose capacitance is formed by a variable capacitance diode. If this equalizer is to be adjusted for considerable signal distortions (long transmission path length), it must operate at great capacitance, which reduces its bandwidth. In order to be able to equalize large bandwidth signals (e.g. 600 MHz) containing considerable distortions, the invention indicates an LC chain circuit with LC components of the known type, as the equalizer. Further developments of this solution concern the appropriate polarizing of the variable capacitance diode and maintaining the frequency response constant, when adjusting the equalization.

Abstract: An adaptive equalization and regeneration system is provided for accurately reconstructing a received data pulse train which has been degraded with respect to amplitude and instantaneous frequency. The system comprises an equalizer which responds to a control signal to provide a variable gain function for the received signal and output an equalized signal, digital phase lock logic for receiving and extracting timing information from the equalized signal, a regenerator for matching the timing information with the equalized signal to reconstruct the received data in its originally transmitted form, and control circuitry for providing the control signal to the equalizer. The control signal adjusts the slope of the equalizer gain function so as to minimize amplitude and instantaneous frequency degradation at the equalizer output. The system includes a mechanism to detect and calculate total signal degradation at the equalizer output.

Abstract: An automatic equalizer for use with a recording and/or reproducing apparatus or with a communication transmission channel, wherein equalizer parameters are rendered variable and the degree of change of the error rate is extracted to set the parameters to optimum values based on the degree of change of the error rate. Output signal error rates are sequentially detected at a plurality of measurement points corresponding to preset plural characteristic parameters to find a minimum error rate measurement point. An initial parameter setting operation is performed for providing characteristic parameters for this measurement point to the equalizer as the initial parameter.

Abstract: An improved decision feedback equalizer for use with digital communications. The equalizer includes an error detector, a process controller, a parameter selector and a data buffer for temporarily storing a digital data signal received from a communication channel. The error detector determines whether the equalizer is accurately tracking changes in the communication channel's characteristics or is lost. When the error detector determines that the equalizer is lost, the process controller responsively generates control signals for initiating an optimal retraining/recovery method for the prevailing conditions. In some retraining/recovery methods, data is temporarily stored in the buffer. The stored data is later retrieved and processed once the equalizer is retrained. Retraining is performed using a retraining signal received via the communication channel or, if available, a portion of the data signal which is suitable for retraining, thereby permitting more rapid resumption of data reception.

Abstract: A high frequency receive equalizer for baseband data recovery is disclosed utilizing a frequency selective equalization filter to restore dispersed pulses into a recoverable form. The frequency selective equalization filter has a plurality of independently adjustable stages. Received pulses are passed through an equalization filter whose output is monitored by equalizer feedback control means. The feedback control means adjusts the amount of equalization applied until the amplitude of the equalized pulses reaches a predetermined level.

Abstract: A waveform equalizing filter unit includes a waveform equalizing filter with a plurality of taps each having a unitary delay element and a coefficient multiplier, a clock switching circuit for selecting a clock signal from at least two different frequencies, with the selected clock signal being fed to each of the unitary delay elements of the waveform equalizing filter, and a control circuit for selectively switching the tap coefficients of the coefficient multiplier in the waveform equalizing filter based upon which one of the different clock signals has been selected. A signal time adjuster is further included in a stage situated before the waveform equalizing filter that receives the input signal prior to being fed to the waveform equalizing filter to adjust the timing of the input signal in synchronism with the operation of selecting one of the different clock signal frequencies.

Abstract: An adaptive equalizer is provided with an equalizing assembly for equalizing an input signal having a transmission frame which includes a first training field and a second training field. The input signal is temporarily stored in a storage unit and simultaneously subjected to equalization by the equalizing assembly. An equalization error in the second training field is calculated and compared with a predetermined value. When the equalization error exceeds the predetermined value, the equalizing assembly is reset to do the equalizing operations over again from the head of the second training field, using the input signal stored temporarily in the storage unit.

Abstract: A variable superconducting delay line system and method having a high temperature superconducting trace and ground plane characterized by a variable inductance L per unit length and capacitance C per unit length, wherein the system and method permit users to select a delay time for an incoming signal propagating through a the transmission line. The system is adapted to keep the ratio of L/C constant, while independently changing L and C to achieve the desired delay time, which corresponds to the product of L times C.

Abstract: In a communications device, two coherent detection algorithms (102 and 103), one of which has a decision feedback equalizer (103), and a detector selection algorithm (104) are used to dynamically select a detector depending on whether delay spread distortion is present. First the correlation of the detector without the equalizer (102) is measured. If this correlation is greater than a predetermined threshold, the data from that detector (102) is used by the communications device. If the correlation is less than the threshold, the correlation of the detector with the equalizer (103) is measured. If this is less than the correlation of the detector without the equalizer (102), the data from the detector without the equalizer (102) is used, otherwise the data is taken from the equalizer (103).

Abstract: A transversal equalizer having a specified number of rear taps. The transversal equalizer includes a first transversal equalizer unit which receives input signals through a first input terminal, equalizes their waveforms, and outputs the equalized signals as cascaded signals and a second transversal equalizer unit which receives the cascade output signals and also receives input signals and outputs an equalized signal derived from the input signals.

Abstract: An equalizer (10) for removing parabolic phase distortion from an analog signal (3), utilizing a pair of series connected transversal filters. The parabolic phase distortion is cancelled by generating an inverse parabolic approximation using a sinusoidal phase control filter (18). The signal (3) is then passed through an amplitude control filter (21) to remove magnitude ripple components.

Abstract: A system of the transversal type automatic equalizer with a tap coefficient protection in which an inter-symbol interference is prevented. The system includes a summing unit for summing all of the tap powers detected by tap power detecting unit, and a determination unit for comparing the sum produced by the summing unit with a predetermined threshold value, and for producing the output determination of normal when the sum is not more than the threshold value and producing the output determination of abnormal tap coefficient growth when the sum is more than the threshold value.

Abstract: An adaptive equalizer comprising a computing unit which receives a known signal 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 which contains an interpolation of consecutive sets of tap coefficients between intermittent intervals.

Abstract: A digital wireless subscriber telephone unit for wireless communication with a base station. An IF is used within the subscriber unit and base station which is combined with a carrier signal generated by a synthesizer for RF transmission between stations. In intervals between actuation of the system, a training mode is used wherein a known training signal is compared with a known values to produce correction coefficients to compensate for undesirable variations in timing and/or frequency, these constants being stored for use in correcting actual received signals. During demodulation, the modulated digital signals are fed to the modem processor in the form of time multiplexed I and Q samples and are demultiplexed. The demultiplexed I and Q samples are fed to an equalizer and frequency correction circuit for minimization of errors for production of a frequency correction signal based upon the correction coefficients which is used to correct any errors in the timing and frequency of the system.

Abstract: An adaptive equalizer in a digital receiver filters differentially encoded data bursts containing known data preceded and followed by user data. A storage means saves and restores filter coefficients and other values so that the known data can be filtered repeatedly. As the known data are repeatedly filtered, a known-data generating means generates different differential encodings of the known data as desired data which are compared with the filtered values to obtain error values for use in updating the filter coefficients. A comparator means selects the encoding that produces the smallest cumulative error. The known data are then filtered once more, using the selected encoding as desired data, after which adaptive filtering of user data continues.

Abstract: The field of the invention is that of data processing modules placed in a receiver of a data transmission or emission network, and charged with the equalizing and time-pulse recovery of the received data, in order to furnish to the next elements of the chain of the receiver a clear signal with a clean and resynchronized clock phase.The objective is to provide a device extending the limits of restoring the service in the case of strong disturbances of the channel.