Abstract: An adaptive coefficient signal generator for use in an adaptive signal equalizer with fractionally-spaced feedback. The signals representing the feedback tap coefficients are generated in conjunction with a timing interpolation parameter such that the fractionally-spaced feedback circuitry dynamically emulates symbol-spaced feedback circuitry.

Abstract: A real/complex dual combination channel equalizer is provided, which is capable of minimizing the complexity of a channel equalizer while maintaining the performance of a real and complex mode. The real/complex dual combination channel equalizer includes a combination of elements for inputting real data and imaginary data to a channel select unit, outputting data selected by the channel select unit, yielding real filter output data and imaginary filter output data by multiplying tap coefficients to the outputted data and performing operations, selecting data among the yielded data, outputting a final data of the real filter by subtracting the value outputted from a real decision orientation filter unit from the selected data, outputting real/complex decision data and an error by the outputted data, and renewing the tap coefficient by the data outputted from the channel select unit and the error.

Abstract: A method of assigning values to parameters for IQ mismatch cancellation. The method includes providing values to a processing path of a communication device, passing the provided values through an IQ modulator, at least one non-linear element and an IQ demodulator, to produce distorted values, and estimating at least one parameter for cancellation of IQ mismatch effects of the communication device responsive to the provided values and to the distorted values.

Abstract: A system for balancing a signal having I and Q components includes means for cross correlating the I and Q components to produce a cross correlation product; means for adjusting the gain of each I and Q signal component in accordance with said cross correlation product; and means for adding one component with the adjustable gain of the other component to produce a phase-balanced signal.

Abstract: A power line communication MODEM includes a MODEM main body portion and a power supply portion for converting an A.C. power source to a D.C. power source and supplying the D.C. power source to the main body portion through a cable. An attachment plug for inputting the A.C. power source and a plug socket connected to the attachment plug are provided to the power supply portion, and a power source is supplied from this plug socket to an information processing unit such as a personal computer.

Abstract: The present invention provides for a software configurable wireless modem that can be configured using software downloaded by a host computer. The user can select a preferred mode of operation, or mode selection can be done automatically based upon whether one or more predetermined criterion, such as a location of the modem, are met.

Abstract: A received signal strength indicator operating at low intermediate of zero intermediate frequency is provided. The received signal strength indicator forms absolute values from an in-phase signal component and a quadrature signal component of a low or zero intermediate frequency signal that represents a received radio frequency signal. The absolute values are added. Logarithmic signal processing is performed either before absolute signal forming or after adding. Finally, low pass filtering is performed.

Abstract: A method and apparatus that identifies the degree of correlation between a demodulated in-phase (I) and quadrature (Q) signal that represents phase imbalance between the in-phase (I) and quadrature (Q) signal and corrects the imbalance.

Abstract: A timing phase acquisition method and device for burst modems includes an receiver designed to initialize an equalizer filter by matching clock of the equalizer filter of the receiver with the phase of the received signal.

Abstract: A method and apparatus for estimating a transmitted symbol from a received sample as a function of Signal-to-Interference and Noise Ratio (SINR) of the received sample. The received sample is quantized and mapped to a region of a grid overlaid on the transmitted symbol constellation. The region may correspond to a symbol estimate value or may be processed further to obtain a symbol estimate value. The regions in one embodiment are rectangular. The symbol estimate values may be stored in a memory storage unit.

Abstract: A passband equalizer that performs blind equalization upon a complex signal, e.g., a vestigial sideband (VSB) signal, without using a training sequence. The passband equalizer contains a decision directed equalizer (DFE) that operates upon separate in phase (I) and quadrature phase (Q) signals using a filter for the I signal and a filter for the Q signal without using filters for cross components of the I and Q signals. As such, the DFE contains approximately half of the multipliers and adders that are used in prior art DFEs.

Abstract: A finite impulse response filter including a first circuit for providing plural delayed signals in response to an input signal. A second circuit is included for multiplying respective ones of the delayed signals by a corresponding coefficient and providing a respective intermediate signal in response thereto. A third circuit selectively changes the sign of respective ones of a first set of the intermediate output signals to provide a set of component in-phase signals. A fourth circuit selectively changes the sign of respective ones of a second set of the intermediate output signals to provide a set of component quadrature signals. The component in-phase signals are combined to provide an in-phase output signal and the component quadrature signals are combined to provide a quadrature output signal. In the illustrative implementation, the coefficients are generated in accordance with an industry standard via a storage device such as a register bank.

Abstract: An object is to obtain an adaptive equalizer device and an adaptive equalizer controlling method which provide an ideal output signal certainly and in a shorter time. The adaptive equalizer device includes an adaptive equalizer (4a) receiving a signal indicating a symbol, for filtering the signal indicating the symbol to adaptively remove intersymbol interference by selectively using one of a plurality of preset algorithms, and a rotation detecting circuit (19) receiving an output signal (y(n)) from the adaptive equalizer, for detecting rotation of the symbol of the output signal (y(n)), wherein the adaptive equalizer (4a) selects one of the plurality of algorithms in accordance with detected result flags (&agr;, &bgr;) from the rotation detecting circuit (19).

Abstract: Methods and apparatus for use in a communication channel receiver for generating a sampling phase error signal for adjustment of a sampling clock signal associated with the receiver are provided. In an illustrative embodiment, a method includes generating a signal representative of a weighted linear combination of a predetermined number of samples of a received input signal. The combination is a function of the samples and tap-weights of a finite impulse response filter associated with the receiver. Next, the illustrative method includes generating an error signal representative of the difference between an equalized sequence of samples of the received input signal and a decoded sequence of samples of the received input signal. Still further, the illustrative method includes multiplying the weighted linear combination signal with the error signal to generate a phase error signal. The phase error signal is then used to generate a phase correction signal for subsequent application to the sampling clock signal.

Abstract: Quadrature sampling architecture and method are disclosed for analog-to-digital converters that provide improved digital output signals over prior quadrature mixing implementations. Sampling circuitry according to the present invention samples an input signal with a first and second sampling signals to produce real and imaginary sampled output signals. The first sampling signal, which is associated with the real sampled output signal, is delayed by one-fourth cycle with respect to the second sampling signal, which is associated with the imaginary sampled output signal. This one-fourth cycle sampling signal difference allows for simplified construction of the sampling circuitry. In addition, filter circuitry according to the present invention processes the real and imaginary digital data output signals so that the imaginary digital data output signal is advanced by one-fourth cycle with respect to the real digital data output signal.

Abstract: A dual path equalizer for processing blocks of data includes first and second pre-processors, first and second finite filters, first and second post-processors, and an adder. The first pre-processor applies coefficients b1 to a received signal, the first finite filter applies coefficients a1 to an output of the first pre-processor in order to substantially eliminate a ghost from the received signal, and the first post-processor applies coefficients c1 to an output of the first finite filter. The second pre-processor applies coefficients b2 to the received signal, the second finite filter applies coefficients a2 to an output of the second pre-processor in order to substantially eliminate a ghost from the received signal, and the second post-processor applies coefficients c2 to an output of the second finite filter.

Abstract: The present invention provides a method whereby an adaptive equaliser is applied to the terminal (mobile) receivers in a cellular radio CDMA system whose purpose is to minimise the mutual interference between users sharing the same radio channel. The application relevant to third generation cellular systems which consist of UTRA (or WBCDMA) in Europe and CDMA2000 in the USA (or future merged standards variants of these systems), and has a special application to the time domain duplex (TDD) mode of these systems. An algorithm is provided whereby the equaliser is adapted to conform to some recognised optimality criterion which is known to lead to a minimum mutual interference situation. One method is the constrained minimum output finite impulse response (FIR) digital filter power condition, but the technique is not limited to this criterion. The method reduces the computation load of a digital filter by selecting a sparse subset of delay line taps which are actively weighted and used as a filter.

Abstract: A method is provided for automatically optimizing parameter selection in a communication system having one or more channels for transmitting and receiving signals comprising the steps of: receiving a signal from a channel; characterizing impairments in the channel while gathering statistics using the received signal; analyzing the impairments to obtain recommendations for parameter modifications for improved performance; and modifying the parameters based on the recommendations. Other systems and methods are disclosed.

Abstract: A demodulation apparatus of the present invention comprises: an A/D converter for sampling and quantizing a baseband signal; a transversal filter having time-shifted tap coefficients; a decision unit for decoding the signal which has undergone the transversal filter; and a decision point estimation unit for instructing the transversal filter to select the tap coefficient to be selected based on information from the decision unit. Thus, the demodulation apparatus can operate at the same frequency as a sampling frequency of the A/D converter and can perform decision with accuracy equivalent to an arbitrary oversampling number.

Abstract: In a receiving device, a mixer combines a frequency which is different from a carrier frequency by (2n+½)&ohgr;0 and a reception signal, provided that n is an integer, &ohgr;0=2Π/T, and T is a transmission rate of a base band signal, a filter takes out a base band signal of a center frequency of (2n+½)&ohgr;0 and removes a DC component, so as to sample the signal and put it through A/D conversion, a multiplier combines the signal and a polarity signal, so as to obtain an in-phase component p(nT) of the reception signal at time nT and an orthogonal component q[(n+½)T] of the reception signal at time (n+½)T. A branch metric is calculated and maximum likelihood sequence estimation is executed on the basis of those components and a replica signals pR(nT) and qR[(n+½)T], so as to estimate a signal sequence.

Abstract: A desired signal having a wide frequency band and including sequential symbols representing digital values is discriminated from a narrow band interfering signal having a carrier frequency in the wide band by initially applying both signals to a filter so both signals are passed to an output of the filter. In response to the filter output, estimates of the values of received symbols of the desired signal are derived and compared to the filter output to derive an error representing signal. A characteristic of the filter is controlled in response to the error representing signal so the filter is adjusted to reject the interfering signal and pass the desired signal.

Abstract: The invention provides an automatic delay equalizer and an automatic delay equalization method which can detect a delay characteristic (delay distortion) of an input signal and automatically compensate for the delay characteristic. The equalizer includes an inclination delay equalization section for compensating for the delay characteristic of the input signal in accordance with an inclination delay characteristic, and a control section for discriminating a direction of variation of a value of a first one of a pair of digital demodulated signals of the input signal, detecting error information from a second one of the digital demodulated signals which is orthogonal to the first signal and outputting a control signal for the inclination delay equalization section based on a correlation between the error information and the direction of variation of the value of the first signal.

Abstract: A method for correcting the phase and amplitude imbalance of a quadrature modulated RF signal requires that errors be induced in both amplitude, &rgr;, and in phase &phgr; in at least three different combinations in order to determine the appropriate correction value for amplitude and phase offsets &Dgr; and &thgr;e. According to a first embodiment the same &rgr; and &phgr; offsets applied in three different combinations to determine the necessary &Dgr; and &thgr;e corrections. According to a second embodiment, a fourth measurement is made in order to determine an unknown control scale factor for balance adjustments.

Abstract: The problem is solved by converting each radio frequency of a plurality of communications systems to tested signals as digital signals via single A/D conversion means; inputting the one A/D-converted tested signal to Fourier transform means 16 for frequency spectrum analysis; converting the other A/D-converted tested signal and a local frequency LO2 via a tested signal converter 13; filtering the converted tested signals S13 to convert them to tested signals S14 containing necessary signal components; and decimating the filtered tested signals S14 and performing frequency spectrum analysis on the decimated tested signals S15 via the Fourier transform means 16.

Abstract: A method of demodulation and equalization is used to process an amplitude modulated compatible digital broadcasting signal including an amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal in a first frequency spectrum, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary carrier signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary carrier signals and lying outside of the first frequency spectrum.

Abstract: A phase tracker receives a signal component xn and forms a phase- and gain-corrected signal zn. In particular, the phase tracker performs a Hilbert transform of xn to produce a quadrature phase component yn to form the constellation defined by (xn, yn). Consequently, phase rotation and gain adjustment are combined into a linear transform of the constellation defined by (xn, yn). The linear transform zn=&agr;xn+&bgr;yn employs two coefficients &agr; and &bgr;. The coefficients &agr; and &bgr; of the linear transform are derived so as to provide an optimal solution according to minimum mean square error. Approximations to the coefficients &agr; and &bgr; of the linear transform may be iteratively determined with a stochastic gradient method. Advantages of employing the phase- and gain-corrected signal zn as an I-phase detection result of a demodulator include 1) the phase rotation and gain adjustment are combined into one operation, and 2) the a sine/cosine lookup table is not employed.

Abstract: GSM baseband receiver arrangement using digital signal processing is disclosed. The baseband receiver arrangement comprises two channel for inphase (Iin) and quadrature (Qin) components of the received signal. The DC offset of each channel is separately estimated by accumulating samples from the outputs of the second filter stages M1 and M2 and dividing the result by 64. The result is then negated and applied to the digital DC offset controls I1 and I2. This two stage process ensures that the majority DC offset is removed prior to variable gain, and the residual DC offset is removed before digital frequency shifting. Applying DC offset correction before the digital frequency shifting ensures that DC is annulled for any subsequent shift.

Abstract: A new radio frequency transceiver architecture comprises a combination of direct digital synthesis and digital control functions to control dual switched capacitor filters in order to perform radio frequency conversion directly to and from baseband.

Abstract: A waveform equalization coefficient generator for generating equalization coefficients for taps of digital filters for equalizing signal waveforms is disclosed which is smaller in circuit size and consumes less electric power in comparison with conventional waveform equalization coefficient generators. In a data selection means in a complex arithmetic unit, a first data selection unit selects between real part data and imaginary part data of an equalization coefficient, a second data selection unit selects between real part data and imaginary part data of a received signal, and a third data selection unit selects between EI (error data in the I-axis direction) and EQ (error data in the Q-axis direction). A sum-of-products means is provided which has one multiplier and one adder.

Abstract: A method of demodulation and equalization is used to process an amplitude modulated compatible digital broadcasting signal including an amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal in a first frequency spectrum, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary carrier signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary carrier signals and lying outside of the first frequency spectrum.

Abstract: A communication system for communicating a modified geometric harmonic modulated (GHM) signal on a power line is described. The system includes a transmitter for transmitting a GHM signal having a plurality of carriers, a highest frequency carrier being about 630 Hz, and a receiver for receiving the transmitted GHM signal.

Abstract: An adaptive equalizer for use in blind equalization systems to compensate for transmission channel distortion and noise in a digital communication system uses multiple quantization levels for implementation of the Constant Modulus Algorithm (CMA). Different quantization levels are used in different regions of the CMA error function for both passband and baseband equalizers. In one embodiment, a quantizer with a step rise having logarithmic scale is used to digitize the CMA error function. In particular, a quantizer with a step rise in which each level of the quantizer step rise is a power of 2 is used to digitize the CMA error function. In another embodiment, a quantizer with a step rise in which each level of the quantizer step rise is the sum of two or more logarithmic scales is used to digitize the CMA error function.

Abstract: The present invention balances the amplitude and phase of a received QPSK signal that may have been corrupted during transmission. The system determines the amplitude of the I and Q symbols of a received signal, compares them, and applies a correction to one or both channels to correct for amplitude imbalance. For phase imbalance, the system calculates the cross-correlation of the I and Q symbols which should average to zero. A correction factor is derived from the cross-correlation and applied to both channels, returning the phase cross-correlation to zero. The output from the system is a signal corrected in both amplitude and phase.

Abstract: A transmitter (500) transmits an original digital code in a transmitted signal component of a transmitted signal to a receiver (600) through a communication channel. The receiver (600) receives a received signal having a first received signal component and a second received signal component where the transmitted signal component results in the second received signal component. The receiver (600) determines a phase between the received signal and the corresponding transmitted signal by detecting a resulting digital code in the first received signal component. A resulting digital code appears in the first received signal component when the received signal is out of phase with the transmitted signal.

Abstract: An adaptive CAP filter includes a clock-controlled A/D converter for converting an input signal, a digital level-control circuit, an adaptive controlled reception filtering system with two parallel filters and a downstream decision maker for outputting reconstructed signal coordinates. The digital level-control circuit and the adaptive reception filtering system are decoupled by virtue of the fact that either an adjustment of the digital level-control circuit or a coefficient adjustment of the adaptive reception filtering system is active. A method for controlling a cap receiver is also provided.

Abstract: In a quadrature amplitude modulation signal demodulation circuit including first and second delay circuits for receiving an I-axis component and an Q-axis component of a baseband signal, a tap coefficient calculating circuit for calculating first tap coefficients in accordance with the delayed I-axis component and second tap coefficients in accordance with the delayed Q-axis component, an interference detection circuit for detecting a center of an interference signal included in the baseband signal, a control circuit for controlling delay time periods of the first and second delay circuits in accordance with an output signal of the interference detection circuit, first and second equalizers for equalizers the I-axis component and the Q-axis component in accordance with the first and second tap coefficients, and an adder for adding the output signals the first and second transversal equalizers, the interference detection circuit is constructed by a plurality of absolute value adders, each for adding an absolut

Abstract: A method for monitoring at least one telephony communication n-bit channel, wherein one of the bits is a parity bit, includes sampling the parity bit of the n-bit channel. A probable bit error rate is derived from the sampling of the parity bit. The probable bit error rate can be compared to a pre-determined bit error rate value to determine if the at least one telephony communication n-bit channel is corrupted. If the at least one telephony communication n-bit channel is corrupted, the at least one telephony communication n-bit channel is re-allocated to an uncorrupted and unallocated telephony communication n-bit channel. Further, at least one unallocated telephony communication channel can be periodically monitored and error data accumulated to indicate the quality thereof.

Abstract: Channel propagation characteristics in a wireless communication system, wherein plural communication links or channels are defined between multiple transmit antenna elements and multiple receive antenna elements, are determined by selecting a matrix of training signals for transmission from the transmit antenna elements, and providing information concerning the selected training signal matrix to a system receiver. The training signals are transmitted from the transmit antenna elements to the receive antenna elements in a determined sequence during a defined training signal time interval, and signals corresponding to the training signals are received via the receive antenna elements. Components of a propagation characteristic matrix for use in discriminating signals transmitted at times other than the training signal time interval, are determined at the receiver as a function of signals received during the training signal time interval and the information concerning the matrix of training signals.

Abstract: A method of demodulation and equalization is used to process an amplitude modulated compatible digital broadcasting signal including an amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal in a first frequency spectrum, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary carrier signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary carrier signals and lying outside of the first frequency spectrum.

Abstract: A method is provided for equalizing an amplitude modulated compatible digital broadcasting signal which includes an amplitude modulated radio frequency signal having a first frequency spectrum, the amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary signals and lying outside of the first frequency spectrum.

Abstract: Phase errors and gain errors are reduced in a receiver to increase the dynamic range of the receiver. An input signal is shifted to an intermediate frequency (IF) and divided into a first channel and a second channel. The first and second channels are multiplied by a complex intermediate frequency signal having a frequency equal to the negative of the IF and by the complex conjugate of the intermediate frequency signal to produce a complex normal signal and a complex conjugate signal. A gain correction factor and a phase correction factor are adjusted based on a correlation signal produced by multiplying the complex normal signal by the complex correlation signal.

Abstract: This disclosure relates to a communication system including a modulator and a demodulator. The modulator produces a modulated signal including a carrier and data signals representing data bits. The data signals include at least two in-phase modulating pulses which have different shapes and which are interfering in time and frequency; the data signals further include at least two quadrature modulating pulses which have different shapes and which are interfering in time and frequency. The modulator includes a filter for producing each shape of pulse, and combining circuits for combining the pulses with each other and with a carrier. The demodulator (or receiver) receives the combined signal and separates the pulses from the carrier. The demodulator further includes filters for separating the pulses, and a circuit for processing the pulses to reproduce the data bits. The processing circuit preferably includes one or more maximum likelihood sequence estimation equalizers.

Abstract: A method for increasing signal acquisition in global positioning system receivers is described. An algorithm for a banked filter of the invention provides low attenuation between frequency bins in which all of the frequency bins produce useful results and no multiplications are required to implement the algorithm. A shortened sampling interval is provided and a banked filter process is implemented. The multiple outputs of the banked filter are detected and summed in post detection filters.

Abstract: A demodulator with a cross polarization interference canceling function for canceling interference of cross polarization in the main polarization includes a demodulating unit for demodulating a baseband signal of the main polarization, a phase control unit which controls the phase of an interference signal, which is a baseband signal of cross polarization, based upon an error in the demodulated signal, and an interference cancellation unit which cancels an interference signal component from the demodulated signal of the main polarization.

Abstract: An imbalance estimator for quadrature modulators comprising two mixers to which are applied two carrier signals and to each of which is applied a modulating signal, output signals of said mixers being applied to a combiner to constitute a modulated signal, detects the instantaneous power of the modulated signal. The detected instantaneous power is multiplied by the modulating signals, and the resulting signals are rectified. The rectified signals are rectified to supply signals indicative of the imbalance of the modulator.

Abstract: A finite impulse response (FIR) filter for wave-shaping digital quadrature amplitude modulation (QAM) symbols is disclosed, in which multipliers are replaced with multiplexers, the replaced multiplexers are utilized to receive the symbols directly from a symbol encoder without zero (0) interpolations, and the critical path is reduced by shifting the position of a delay device. The filter includes a first FIR means for delaying the externally inputted symbol data, and for utilizing the delayed symbol data as selection signals to sum up the selected multiplication product (selected from among products obtained by multiplying the symbol values by a pre-set filter tab coefficient) and the selected value selected by a first multiplexing means. A second FIR means delays again the delayed symbol data of the first FIR means, and utilizes the delayed symbol data as selection signals to sum up the selected multiplication product and the output value of the first FIR means.

Abstract: A radio receiving apparatus regenerates a clock synchronized to a symbol clock contained in a quadrature demodulated signal obtained by demodulating a multilevel quadrature modulated signal, converts the analog quadrature demodulated signal, at the timing at which the regenerated clock occurs, to digital data and outputs the digital data via a transversal equalizer. The apparatus includes a slope discriminator for outputting the slope of an in-phase signal constituting the quadrature demodulated signal. A FIR filter constructing the equalizer outputs, as an error signal between input and output signals of the equalizer, an output signal of the FIR filter which prevails when a center tap coefficient of the filter is regarded as being zero.

Abstract: A transversal filter equalizer comprising a programmable transmitter baseband equalizer for use in high rate digital transmitters. The programmable transmitter baseband equalizer processes digital data using a 1/2-symbol spaced transversal filter to produce I and Q baseband signals. The 1/2-symbol spaced transversal filter comprises I and Q n-bit wide shift register stages having alternate pairs of I and Q shift register stages driven by opposite phases of an input data clock, multiplying digital-to-analog converters driven by two direct tap weights and two cross tap weights, and I and Q combiners for generating I and Q baseband signals. The I and Q baseband signals are fed to a quadrature modulator that produces the desired constellation.

Abstract: A system and method for use in cancelling phase jitter in a Phase Locked Loop (PLL) circuit. A phase jitter canceller receives a phase error signal having phase jitter centered around a center frequency. A frequency and phase control circuit determines the phase of a particular component of phase jitter and an amplitude control circuit determines the amplitude of the particular component of phase jitter in the signal. The output of the phase jitter canceller provides an estimate of the particular component of phase jitter. A parallel arrangement of phase jitter cancellers is also provided for use in cancelling several components of phase jitter.

Abstract: The invention provides a method and system for correcting imbalance in in-phase and quadrature components of a modulated received signal. The method includes assuming a signal imbalance to exist in the received signal, the signal imbalance having an amplitude imbalance and a phase imbalance, generating an amplitude imbalance correction factor and a phase imbalance correction factor to lessen the signal imbalance, and re-evaluating the amplitude and phase imbalance correction factors over a set of readings of the in-phase and quadrature components until the signal imbalance is minimized.