Abstract: A method and apparatus for improved interference rejection, where the rejection is being accomplished by an IIR filter at the transmitter with complementary characteristics to an FIR filter of the receiver, such as a Tomlinson-Harashima transmit-precoder. The improvement is accomplished by providing the ability to preset the transmit and receive filters to the same state, thereby allowing for subsequent receptions to be deterministic. This method and apparatus is particularly useful for correcting for time-varying interference through the use of repeatable, deterministic, training sequences.

Abstract: An apparatus for performance improvement of a digital wireless receiver comprises a processing circuit for processing a plurality of received signals and providing a processed signal, wherein a plurality of weights is applied to the plurality of received signals producing a plurality of weighted received signals. The plurality of weighted received signals are combined to provide the processed signal. A weight generation circuit generates the plurality of weights wherein weights are based on a ratio of a desired signal, a noise signal and an interference signal.

Abstract: A method of digital telecommunication via an electrical cable is provided, whereby the symbols of a data stream to be transmitted are supplied as a transmission signal to a transmission path, after undergoing a digital-to-analog conversion. The transmission signal is received and sampled at the end of the transmission path on a receiving side. To further process the received signal on the receiving side, a Viterbi decoder operating on the basis of a trellis diagram is used. The Viterbi decoder uses a number of feedback filters to determine branch or path metrics in the trellis diagram, where this number is a function of the number of states in the trellis diagram. To determine the branch metrics in the trellis diagram, separate first feedback filters (8) are only used up to a specifiable number of symbol intervals in the trellis diagram, or up to a specifiable length of feedback filters for all states in the trellis diagram.

Abstract: A set of parameters (W) is calculated for an equalizer which equalizes a transmission line impulse response (LIR) in such a way that the equalized impulse response (EIR) approximates a target impulse response (TIR) with predetermined length (L). An error function (E) is minimized via eigenvalue-eigenvector calculation of a channel dependent matrix (O). This channel dependent matrix (O) is built up from a signal (X), a distorted signal (Y), and length (L) and delay (D) of the target impulse response (TIR). The error function (E) comprises a first contribution which represents the difference between the equalized impulse response (EIR) and the target impulse response (TIR) and a second contribution which represents the energy (E.sub.DC) that is transmitted in unused frequency bands. The eigenvector corresponding to the minimum eigenvalue of the channel dependent matrix (O) represents the set of equalizer parameters (W).

Abstract: A system for resynchronizing the timing and carrier phases of a modem receiver signal to enable the receiver to quickly reacquire the timing phase and the carrier phase, and thereby restart the demodulation process. The system provides accurate estimates of the timing and carrier phases, as well as a gain correction factor to provide for proper alignment for decoding. The discrete Fourier transform of the received signal is multiplied by the complex conjugate of the discrete Fourier transform of the transmitted signal to produce estimates of the desired phases. Gain control and carrier phase control are performed to determine corresponding error signals to adapt the resultant estimated timing and carrier phases, and gain correction.

Abstract: In a multi-carrier system, the pilot carrier which is transmitted between two stations for synchronisation purposes, is re-allocated to a new frequency whenever it is disturbed by noise or a single frequency disturber in the vicinity thereof. A less noisy frequency is selected by means of a specific criterion to be fulfilled, for instance based on signal to noise ratio measurements performed for all carriers in the multi-carrier system.

Abstract: Radio transmissions are spectrally contained to reduce adjacent channel interference by a method and apparatus for I,Q filtering of signals before quadrature modulation in digital cellular radio transmission systems such as communications systems following the GSM TDMA, IS-54 or IS-95 standards. The filtering is accomplished by multiple stage registers connected at their complementary outputs to identical resistor networks. The outputs of the resistor networks are summed to represent a smoothly transitioning analog representation of the digital voice or data transmission. The analog representation may be additionally low pass filtered to remove higher frequency components before quadrature modulation. Because rapid transmissions in the transmittal signal are avoided, adjacent channel interference is reduced.

Abstract: Transmission mode selection is enabled, so communication reliability, transmission speed, and equipment utilization efficiency are all high. A first transmission system whereby spectrum spreading is accomplished with a spread code 1 and data is transmitted, and a second transmission system whereby data is transmitted with a spread code 2, are provided. In high-reliability transmission mode, identical data from a data buffer is transmitted through both the first and second transmission systems to achieve space diversity. In high-speed mode, data divided by a data division circuit is transmitted simultaneously through the first and second transmission systems, making possible efficient data transfer. Control information insertion circuits append transmission mode data to the transmitted data.

Abstract: A digital data receiver comprising a first frequency converter for converting a high frequency digital orthogonal modulation signal into a first intermediate frequency signal based on a first local oscillation signal, a second frequency converter for converting the first intermediate frequency signal into a second intermediate frequency signal based on a second local oscillation signal, and a demodulator for performing a orthogonal demodulation to the second intermediate frequency signal based on a third local oscillation signal, wherein the first local oscillation signal is generated by a variable oscillator for a PLL frequency synthesizer, the second local oscillation signal is generated by a high frequency oscillator in which its oscillation frequency is controlled based on the frequency control signal generated by the modulator to perform the orthogonal demodulation processing, and the third local oscillation signal is generated by a fixed oscillator in which its oscillation frequency is fixed.

Abstract: A method for providing improved carrier based data operated squelch (CDOS) includes routines for recovering the carrier signal and for analyzing the received signal. The received signal is sampled at each transition point of the carrier signal as well as the halfway points between the transition points. In addition, extra samples are taken between these samples. Using the samples, a carrier locked loop routine recovers the carrier signal. A CDOS routine analyzes the extra samples to determine the presence of data. If two successive samples are different, this means that a transition has occurred. The CDOS routine analyzes these transitions to determine whether the input signal is encoded with data. If the CDOS routine determines that the input signal is encoded with data, a CDOS counter is incremented. As the input continues to look like data, the value by which the CDOS counter is incremented is increased. When the CDOS counter reaches a certain threshold, the CDOS mutes the output circuit.

Abstract: A radio frequency (rf) receiver adapted to receive a number of different digitally modulated rf input signals such as quadrature amplitude modulated (QAM) and vestigial side band (VSB) rf input signals includes circuitry for down converting the rf input signals to an intermediate frequency (IF) range having a center frequency fc2 and a bandwidth of Bhz and converter circuitry for sampling the IF signals and then producing corresponding baseband signals. In a preferred embodiment, the intermediate frequency signals are applied to a sample and hold circuit which is sampled at a frequency fs and whose output is coupled via a low pass filter to an analog-to-digital converter whose output is then applied to a Hilbert filter for demodulating the sampled signals and producing baseband signals. In-phase (I) and quadrature (Q) signals are produced whose phase and amplitude are not a function of different components and their tolerance of different conduction paths, as in the prior art.

Abstract: A synchronization method and apparatus for synchronizing a receiver, such as a radiotelephone operable in a cellular communication system with a transmitter. Synchronization signals are transmitted as parts of a control signal to the receiver. Such synchronization signals are of high margins and also permit synchronization of the radiotelephone responsive to a reduced number of calculations. The time for such synchronization is reduced by use of nonlinear transformation metrics, such as logarithmic metrics, which reduce the impact of a noise or error component within the control signal.

Abstract: In a field bus system for performing communication between at least one field device and at least one higher-rank apparatus which are connected on a field bus transmission line constituted by a pair of transmission lines, an intrinsically safe barrier disposed between a hazardous area and a safe area on the transmission line in order to limit energy to be used in the hazardous area, the intrinsically safe barrier comprising impedance converting circuits provided in the barrier for reducing impedance in a frequency band of communication data.

Abstract: A digital frequency demodulator includes a first counter and a second counter measuring the instantaneous and mean values of the period of a frequency modulated signal. A comparator compares the values measured and creates a binary signal of the same frequency as the modulation signal. The measurement of the instantaneous value of the frequency modulated signal is effected by counting the number of reference clock pulses during a period of the modulated signal, and the measurement of the mean value is effected by counting the number of pulses of a clock signal of frequency N times lower than the reference clock during N periods of the modulated signal.

Abstract: The invention is related to a method and circuit arrangement for processing a received signal in a variable symbol rate system, such as a digital television system. In the method and arrangement according to the system, a received signal is sampled at a fixed sampling frequency (f.sub.f) that is higher than the symbol frequency of any one of the received signals. The resulting sample sequence is converted to another sample sequence the sampling frequency of which equals the symbol frequency (f.sub.i) of the received signal or its integer multiple. Then the samples are filtered (8) and signal value decisions are made (9) for the filtered samples. Conversion of the sampling frequency is advantageously performed using a so-called modified Farrow-type fractional delay filter (6) which is controlled using a control signal proportional to the delay of each sample.

Abstract: A transmission and receiving system, includes a transmit interface unit, a transmit signal processing unit, a transmit signal converting unit and a microwave transmitting unit all a first location. The system further includes a microwave receiving unit, a receive signal converting unit and a second signal processing unit. The system can transmit information such as an audio/video signal of broadcast quality or file information via satellite from anywhere in the world to anywhere in the world (except the polar caps) in real time.

Abstract: A digital resampling system is provided for converting a first digital signal to a second digital signal, where both signals represent the same analog signal but sampled at two different clock rates which are not phase-locked together. A filter is clocked by the first clock and outputs filtered samples at the first clock rate, optionally omitting samples which will not be used. A phase indicator determines the relative phase position of the first and second clocks and indicates an integer phase value and a fractional phase value which together indicate where a tick of the second clock falls among the ticks of the first clock. The integer phase value identifies a clock cycle of the first clock in which a tick of the second clock occurs, and the fractional phase value represents a fraction identifying a position of the tick of the second clock within the clock cycle of the first clock. A sample selector selects M filtered samples from those provided by the non-decimating filter based on the integer phase value.

Abstract: A quadrature overlapping modulation method for modulating and shaping a baseband data sequence which has a data bit rate of 1/T. The method separates a baseband data sequence into an even bit data sequence to a first channel and an odd bit data sequence to a second channel, delaying by .tau.=T time the even bit data sequence and the odd bit data sequence relative to each other. After that, both the even bit data sequence and the odd bit data sequence are shaped in a waveform shaping filter. A carrier signal is generated and it modulates both the even bit data sequence and the odd bit data sequence. The data sequences are shaped with a combination of a triangular function and a trigonometric function or with a convolution function of two trigonometric functions before carrier modulation.

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: The present invention relates to a method of aligning and blending input digital samples, comprised of delaying the input samples by a clock pulse, to provide delayed data samples, subtracting a smaller fractional part from a larger fractional part of either an input sample number and a requested sample number to provide a sample difference number first factor, subtracting the sample difference number from 1 to provide a second factor, multiplying either of the input samples or the delayed samples by the first factor to provide a first result, multiplying the other of the input samples or the delayed samples by the second factor to provide a second result, and adding the results to provide output samples.