Abstract: A signal receiving system for spread spectrum communication including receiving a signal produced by multiplying a data to be transmitted by a predetermined spread code sequence through spread spectrum modulation and performing spread spectrum demodulation by multiplying the received signal by an attenuation spread code sequence prepared by predetermined attenuation or amplification to each chip of the spread code sequence used on that modulation.

Abstract: A method and device for processing a signal are described, wherein an estimate of a multipath-induced contribution to a demodulated navigation signal is calculated and subtracted from said demodulated navigation signal to obtain an estimated line of sight contribution to said demodulated navigation signal, and a propagation time .tau..sub.0 is calculated from the thus calculated line of sight contribution to said demodulated navigation signal, such that a very accurate propagation time .tau..sub.0 of said navigation signal can be calculated.

Abstract: A process for transmitting digital signals, in which the digital data are coded differentially in symbols of a symbol period T.sub.s (2.1, 2.2), the symbols transmitted with the Q component being delayed by T.sub.s /2, relative to those of the I component, to achieve a time-staggering. A cross interference of the I and Q components, occurring on the receiver end and caused by the differential coding nd the time staggering, is resolved with a trellis decoder (10), for example. As a result, a differential offset QPSK process achieved on this basis combines the advantages of DQPSK and OQPSK procedures.

Abstract: A radio communication apparatus comprises a first/second modulator for modulating a first/second signal according to a first/second frequency, a first demodulator for detecting the received first modulation signal and regenerating the carrier, a clock regenerator for regenerating a clock from the detection output from the first demodulator, an amplitude sampler for sampling the amplitude of the received first modulation signal according to the regenerated clock, a second demodulator for controlling the frequency of the received second modulation signal and executing demodulation for the signal, and a gain controller for executing gain control for the output from the second demodulator according to the output from the amplitude sampler.

Abstract: A technique for modulating and demodulating continuous phase modulation (CPM) spread spectrum signals and variations thereof. A transmitter encodes M data bits using a selected spread spectrum code, divides the spread spectrum code into a plurality of chip codes (such as even chips and odd chips), independently modulates the even and odd chips with orthogonal carrier signals using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and divides it into a real signal and an imaginary signal. The real signal is connected to a real CPM correlator which demodulates its input into a real I signal and a real Q signal, separately correlates the real I signal with the odd chips of a chip code and the real Q signal with the even chips of the chip code, and combines the correlation signals into a real correlation signal.

Abstract: An OFDM synchronization demodulation circuit includes a receiving circuit for receiving an orthogonal frequency division multiplexing (OFDM) modulation signal. An orthogonal detection circuit orthogonally detects the OFDM modulation signal from the receiving circuit using a detected carrier. A demodulation circuit orthogonally demodulates the detected OFDM multiplex modulation signal from the orthogonal detection circuit by sampling the OFDM multiplex detection signal using a detected clock. A constellation analyzing circuit analyzes the constellation of demodulated symbols of predetermined carriers in the demodulated OFDM multiplex signal signal. A carrier frequency deviation detection circuit detects a frequency deviation of the detected carrier based on a rotation of the constellation of the demodulated symbol detected by the constellation analyzing circuit.

Abstract: In a communication system that utilizes DMT technology to couple a primary site (102) to a plurality of secondary sites (104-108), the primary site (102) and each of the secondary sites (104-108) includes a DMT transmitter. Such a DMT transmitter includes a discrete multi-tone encoder that receives an ordered data stream and produces an encoded data stream based on bit loading information, and a data formatter operably coupled to the discrete multi-tone encoder, wherein the data formatter receives transmit data entries and produces the ordered data stream based on carrier channel allocation information.

Abstract: In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with simple and direct physical meaning in terms of loop noise bandwidth, root-specific decay rate, and root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (B.sub.L T .fwdarw.0) and in a discrete-update formulation with arbitrary B.sub.L T. Deficiencies of the continuous-update approximation in large-B.sub.L T applications are avoided in the new discrete-update formulation.

Abstract: This invention relates to an apparatus for retiming digital data transmitted at a high speed even though the phase of a binary data bit is not related to the phase of the static offset of a retiming clock pulse, the apparatus comprising: local clock pulse generation means 11 for generating and outputting local clock pulse FT; delayed clock pulse parallel generation means 12 for outputting, in parallel, n delayed clock pulses delayed sequentially by one cycle of local clock pulse FT; input data transition detection means 13 for outputting pulse DT each time the rising and falling carrier waves intersect in input data D; sequential logic parallel phase detection means 14 for providing clock pulse selection data by outputting sequential logic phases of the upper location of the pulse generated during input data transition and transition location of n delayed clock pulses; retiming clock pulse selection means 15 for outputting a retiming clock pulse according to the clock pulse selection data of the input delayed

Abstract: A bidirectional data transceiver circuit is described which automatically transfers data from a first bidirectional data port to a second bidirectional data port when new data is detected. The transceiver has a collision arbitration circuit which prevents the device from driving data onto a data port that is being driven externally. An additional embodiment is described wherein the transition detection circuitry of the transceiver is used to provide a input transition detection flag for an integrated circuit having standby or low power modes. An integrated circuit providing an array of the transceivers of the invention is described. A transceiver which automatically detects a transition in data and provides output drive for data busses is described. Other devices, systems and methods are also described.

Abstract: A digitally compensated direct-conversion receiver includes devices for generating digital samples of a base-band in-phase signal and a base-band quadrature signal and for detecting the presence of a second-order product signal produced by an amplitude-modulated interfering signal. Also, the apparatus comprises a device for digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples. In one method of digitally compensating samples of an information signal quadrature-modulating a carrier signal, estimated samples of a second-order product from a switched carrier signal are formed by averaging the digital samples during two time periods and by determining a time of ramps in the in-phase and quadrature signals that occur between the time periods due to the interfering signal. The digital samples may be differentiated and the results smoothed in determining the time of the ramps.

Abstract: A radio receiver for demodulating and equalizing digital information is disclosed. The receiver receives radio signals and processes the signals to produce data samples which are then stored. Reference values that model what the receiver should receive for various transmitted symbol sequence hypotheses are also stored. The receiver equalizes the received data using the stored reference values to produce symbol detection information, and updates the reference values based on the symbol detection information.

Abstract: A soft-decision modulation system (10) has a transmitter (11) and a receiver (21). The transmitter encodes (68), modulates (72) and transmits (74-78) a data stream. The receiver receives the modulated data stream and recovers symbols (86) representing the transmitted data stream. Data decoding (92) is performed with a trellis decoder with a soft-decision metric using a selected set of coefficients (90). The performance of the decoding step is evaluated (104). The coefficients are adjusted (108) until performance is acceptable. When performance is satisfactory the coefficients are installed (112) in the modulation system.

Abstract: Before transmission of moving image data, the period of a frame of the moving image data is counted using a clock signal used for the transmission to produce a frame count. The moving image data is then transmitted along with the frame count so that it can correctly be timed in frames at receiver.

Abstract: A start-up method for a data modem having an echo cancelling loop between the send port and receive port, the loop including a transversal filter having adjustable coefficients, adjustable phase-shifter and a subtractor for subtracting send port data symbols which have been filtered and phase shifted from data symbols received at the receive port. During start-up, in response to a series of data symbols supplied at the send port, a microprocessor iteratively adjusts the filter coefficients and the phase shift to cancel any echo at the output of the subtractor. In order to reduce the convergence time, the start-up method includes estimating the power of the echo over a time period corresponding to a predetermined number of data symbols at the send port, quantizing the estimated power, and adjusting the filter coefficients and the phase shift on the basis of the quantized echo power level.

Abstract: A method of controlling a digital carrier recovery apparatus designed to be integrated in a demodulation stage of a receiver for receiving a digital signal. The demodulation stage includes a carrier recovery detection apparatus. The carrier recovery detection apparatus includes a loop filter including a summing circuit followed by a bistable circuit operating in time with the symbol time, and a switching device disposed between the summing circuit and the bistable circuit. The switching device is driven to alternately apply to the bistable circuit a control word, whose variation between two successive applications to the bistable circuit is less than the acquisition band of the carrier recovery apparatus, and the output signal of the summing circuit. By alternately applying the control word and the output signal, the acquisition band is displaced relative to the tracking range of the carrier recovery apparatus.

Abstract: This invention is a multilevel trellis coding method which employs a single binary convolutional code and is called a single-stage and multilevel trellis coding. This invention can be generalized by combining several single-stage multilevel codings together to form a multilevel trellis coding for which the number of stages is less than the number of coding levels. New trellis coded modulation systems and binary trellis coding systems which are designed by the aforementioned trellis coding method are better than the currently known coding systems if the communication channels are additive white Gaussian noise (AWGN) channels.

Abstract: The present invention provides a novel Geometric Harmonic Modulation (GHM) system. The GHM system operates in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase offset in the transmit unit and passed through a channel to a receive unit. The set of phase offsets is used as the spreading code in the transmit unit, and also acts as an `address` of receive units to transmit to. The receive unit monitors preamble signals to determine the phase offsets. When it recognizes a set of phase offsets, or `address`, which pertains to itself, the receive unit stores the phase offsets and uses these phase offsets to despread and decode the appended message. After the preamble mode is finished, the GHM modulator enters the traffic mode and requests the message to be transmitted from the message source. A traffic carrier waveform is created by multiplying tones, each having its specific phase offset.

Abstract: The present invention provides a novel frequency Interlaced Geometric Harmonic Modulation (IGHM) system. The IGHM system operates in two modes, a preamble mode and a traffic mode. During the preamble mode, n+1 frequencies are each offset by a predetermined phase in a transmit unit and passed through a channel to a receive unit. The set of phases is used as the spreading code in the transmit unit, and also acts as an `address` of desired receive units. The receive unit monitors preamble signals to determine the phases. When it recognizes a set of phases, or `address`, which pertains to itself, the receive unit stores the phases and uses these phases to despread and decode the appended message. After the preamble mode is finished, the IGHM modulator enters the traffic mode and requests the message to be transmitted from the message source.

Abstract: The present invention provides a system for determining, and correcting for, channel-induced distortion in transmitted wideband carrier signals. During a synchronization, or sounding mode, known as the preamble mode, a wideband signal consisting of a number of tones, which may be those of geometric harmonic modulation (GHM), each having a phase of zero are transmitted to a receive unit. At the receive unit, the phases for each tone are extracted. Since each tone is at a different frequency, a snapshot of the change in phase over a number of frequencies can be determined. These phase changes are employed in determining the generalized phase distortion over frequency equation which is used to remove the phase distortion induced by the channel before decoding of the signal. The device then operates in its traffic mode thereby transmitting information to a receive unit which uses the phase distortion information to remove phase distortion induced by the channel and then decode a message signal.