Abstract: Based on changing reception conditions, a wireless receiver adapts its demodulation method during active communications. Phase errors detected in the received signal indicate current reception conditions, and, optionally, received signal strength serves as an additional indicator. The receiver supports operation with fully coherent, fully non-coherent, and partially coherent demodulation. The receiver determines a demodulation quality indicator based on the phase error signal. The value of the demodulation quality indicator increases with increasing phase error. When the demodulation quality indicator is below a first defined threshold, the receiver operates with fully coherent demodulation. When the demodulation quality indicator is above a second defined threshold, the receiver operates with fully non-coherent demodulation. For demodulation quality indicator values between the first and second defined thresholds, the receiver operates with partially coherent demodulation.

Abstract: An equalizer providing a filtered signal to a data decision unit calculates an amplitude error signal by comparing the filtered signal with the data signal output from the data decision unit, and calculates a squared envelope error signal from the filtered signal. These two error signals are separately weighted according to the absolute value of the amplitude error, the weight of the amplitude error signal decreasing and the weight of the squared envelope error signal increasing as the absolute value of the amplitude error increases. The weighted amplitude error signal and weighted squared envelope error signal are added to obtain an error signal used in updating filter coefficients in the equalizer. Rapid convergence of the filter coefficients is obtained, with small residual error.

Abstract: An image reject mixer arrangement 1 comprises a transconductor 2, first and second mixer cores 3 and 4, first and second phase shifters 5 and 6 and a summer or combiner 7. The mixer arrangement 1 receives a single-ended RF voltage signal on a terminal 8, a differential local oscillator signal on I-LO terminals indicated at 9 and a 90° phase shifted differential local oscillator signal on Q-LO terminals 10, and provides differential IF output signals on output terminals 11. From the output of the transconductor 2 to the output of the combiner 7, the image reject mixer arrangement 1 carries signals in what can be described as a “current mode”, i.e. it is the current, not the voltage, which conveys the desired signal. In this current mode, it is advantageous to provide each active circuit block with a high output impedance and a low input impedance wherever possible.

Abstract: In some embodiments of the present invention, a transmitter includes a switching amplifier and a sigma-delta N-PSK modulator. The sigma-delta N-PSK modulator includes a non-uniform polar quantizer.

Abstract: A system for communicating signals between a transmitter and a receiver using digital modulation techniques is provided. This invention is particularly adapted to meet the requirements of power line communication. In one preferred embodiment of this invention the modulation technique is differential binary phase shift key modulation. This system provides a low cost, simple delay and multiply process for the modulation and demodulation of data. This system lends itself to an ASIC implementation, thereby further reducing the cost of the system while improving the reliability of the system in a noisy environment.

Abstract: A receiver includes an I-Q demodulator (135) responsive to the I and Q components carried on a first frequency signal line (132). [The demodulator comprises a] A demodulator frequency generator (275) [for generating] generates a demodulating signal to extract the carried I and Q components. A phase adjustment circuit (105) [, responsive to the I and Q components that are maintained at a predetermined relationship,] makes the demodulating signal substantially in phase with the first frequency signal. A transition detector (445) generates a state transition signal in response to a change of state of at least one of the I and Q signals. A peak detector (460) generates a peak detected signal in response to occurrence of a peak amplitude of at least one of the I and Q signals. A clock generator (470) adjusts the phase of a symbol clock signal used to decode the I and Q components in response to the state transition signal and peak detected signal.

Abstract: The modulator includes an oscillator generating signals, each having a different phase, and a selector receiving digital data. When the digital data received by the selector changes logic state, the selector supplies a first and second plurality of signals generated by the oscillator to first and second non-linear amplifiers, respectively. An adder then adds the output of each amplifier to generate a radio frequency output.

Abstract: Angle-modulated signals are transmitted in a communications system, in which coding information has been inserted into the transmitted data at regular intervals. The coding information is phase-modulated together with the transmitted data. This coding is used for pulse shaping, so that the receiver can recover the digital transmitted data with less implementation complexity and without carrier phase control by using appropriate signal processing.

Abstract: A wireless device and system employs a two-dimensional (2-D) Trellis code that can be applied to Quadrature Phase Shift Keying (QPSK) and higher order Quadrature Amplitude Modulation (QAM) constellations. The Trellis codes employed have optimal Euclidean distance properties for QPSK constellations, and have very good Euclidean distance properties for higher-order QAM constellations. The Trellis codes are suited for transmission systems that adopt multi-mode QPSK and QAM constellations with different data rates since the same Trellis code can be applied to all modulation formats and the same decoder can be used at the receiver for all modulation formats. Modulation formats include QPSK, 8-QAM, 16-QAM, 32-QAM, and 64-QAM and may be extended to even higher order modulations formats.

Abstract: A method of utilizing a bidirectional amplifier in a cable hybrid fiber and coax (HFC) and a cable modem utilizing an upstream signal. The invention provides an upstream pilot signal from the cable modem and automatically controls the gain of the signal so that the headend receives a constant level upstream pilot signal from each terminal. A cable modem for bidirectional services in the HFC network has a saw filter, a mixer & AGC, a LPF, a tuner, a gain controller, a downstream demodulator, an upstream modulator, a media access controller (MAC), a CPU, a programmable attenuator, a pilot signal generator and a switch connecting the tuner and the pilot signal generator under the control of the CPU.

Abstract: Method and apparatus for determining the correct set of samples to retain in applying a decimation process. The present method provides an automatic approach to determine the timing phase of the desired samples to decimate the oversampled input signal (data sequence), thereby producing the underlying data signal.

Abstract: A digital communication system and method is provided for increasing bit-rates while maintaining the reliability of transmitted digital information and avoiding increased power demands. The communication system includes a transmitter that modulates one or more bits onto a carrier signal to generate and transmit a first transmission signal during the first part of a pulse time TB, receives an additional bit, and based on the value of the additional bit, either transmits the first transmission signal again during the second part of the pulse time TB or transmits a second transmission signal during the second part of the pulse time TB.

Abstract: A receiver includes an I-Q demodulator (135) responsive the I and Q components carried on a first frequency signal line (132). The demodulator comprises a demodulator frequency generator (275) for generating a demodulating signal to extract the carried I and Q components. A phase adjustment circuit (105), responsive to the I and Q components that are maintained at a predetermined relationship, makes the demodulating signal substantially in phase with the first frequency signal. A transition detector (445) generates a state transition signal in response to a change of state of at least one of the I and Q signals. A peak detector (460) generates a peak detected signal in response to occurrence of a peak amplitude of at least one of the I and Q signals. A clock generator (470) adjusts the phase of a symbol clock signal used to decode the I and Q components in response to the state transition signal and peak detected-signal.

Abstract: Signals, systems and methods for transmitting and receiving layered modulation for digital signals are presented. A layered signal for transmitting data, comprises a first signal layer including a first carrier and first signal symbols for a first digital signal transmission and a second signal layer including a second carrier and second signal symbols for a second signal, transmission disposed on the first signal layer, wherein the layered signal has the first carrier demodulated and first layer decoded to produce the first signal symbols for a first layer transport, the first signal symbols are remodulated and subtracted from the layered signal to produce the second signal layer, and the second signal layer has the second carrier demodulated and decoded to produce the second signal symbols for a second layer transport.

Abstract: To keep the power consumption in the modulator-demodulator of a mobile radio as low as possible, the modulator-demodulator has a voltage-controlled oscillator. Downstream of which a divider chain having a plurality of series-connected dividers each with an even-numbered division factor is connected. Each of the dividers produces a carrier signal and a carrier signal that is orthogonal with respect thereto. A quadrature modulator for the received signal is connected to a divider of the divider chain that produces the carrier signal at the required carrier frequency. In addition, a first vector modulator is provided whose mixers are connected to the dividers of the divider chain that produce the carrier signals at the required carrier frequencies. Connected downstream of the first vector modulator is a further divider with an even-numbered division factor, and connected downstream of this is a second vector modulator for producing a transmitted signal.

Abstract: The invention relates to a method for implementing a transmission connection. In accordance with the method, symbols (DATA_IN) are formed from the bit stream to be transmitted, carriers are generated on several different frequency bands, and the bit stream is transmitted with the aid of the carriers by dividing the formed symbols between the carriers in such a way that each carrier is modulated with some of the bits in the bit stream. To enable implementation of modulation and demodulation in such multicarrier systems with as simple and efficient equipment as possible, the modulated carriers are first generated on the transmitter side each separately on predetermined first frequencies, whereafter at least some of the carriers are supplied to a halfband filter bank (64) transferring at least some of the carriers supplied to it to their final frequency bands in the frequency domain and combining said carriers to its output. Halfband filter bank is also used in the receiver.

Abstract: A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

Abstract: Methods, apparatuses and systems are provided for identifying at least one multipath transmission delay within a reverse path data signal, determining at least one forward path pre-equalization parameter based on the transmission delay, and modifying a forward path data signal based on the forward path pre-equalization parameter. A reverse link transmission is used to help characterize the multipath delays that may exist between communicating devices. The reverse path data signal can include a training sequence or other like known/substantially-known data that can be analyzed to detect transmission delays, especially delays that extend beyond established guard intervals. Such pre-equalization techniques can be advantageously combined, for example, with antenna arrangements that support transmission diversity, spatial division transmission, and/or other like techniques.

Abstract: A method of estimating the carrier frequency of a phase-modulated signal involves a) extracting the pulse train from the signal, b) making an initial estimate of the carrier frequency, c) estimating the error in the initial estimate, d) using this error to generate a more accurate estimate of the carrier frequency, and repeating steps c) and d) until a sufficiently accurate estimate of the carrier frequency is obtained. Step c can involve extracting the phase information in the signal, mixing the signal down to 0 Hz by removing the initial estimate of the carrier frequency to give complex IQ data, calculating the phase of the signal as a function of time, calculating the mean phase, wrapping the data into a phase range equal to the size of the phase jump, and calculating the error in the initial estimate of the carrier frequency from the gradient of this graph.

Abstract: A wireless transceiver includes a Radio Frequency (RF) transceiver, a baseband transmitter section, and a baseband receiver section. The baseband receiver section receives a baseband signal from the RF transceiver, extracts data therefrom, and provides the data to a host system. The baseband receiver section includes a programmable gain amplifier, an Analog-to-Digital Converter (ADC), a symbol timing compensation section, an RF carrier compensation section, a decision feedback equalizer section, and a preamble processor. The symbol timing compensation section modifies the samples of the baseband signal to compensate for symbol timing variations between a symbol clock of the wireless device and a symbol clock of a transmitting wireless device. The RF carrier compensation section modifies the samples of the baseband signal to compensate for RF carrier variations between an RF carrier of the wireless device and an RF carrier of the transmitting wireless device.

Abstract: A local area network is based on a ring of twisted pair cable links (UTP), each carrying at least 1.4 Mbps gross data rate. Each station on the network includes an encoder and a following station includes a decoder for PSK (phase shift keying) modulated serial data. The encoder uses an analog sine wave oscillator and inverter for generating antiphase analog sine wave signals at a carrier frequency and a switching circuit for selecting between the carrier signals according to the data signal to be transmitted. The decoder may use a simple integrator and comparator arrangement. The encoder and decoder may be provided in the form of an adapter circuit, such that a network based on optical fibre can be replaced by a network based on twisted pair cable using the same digital circuits. Generation of the PSK waveform by analog circuitry rather than digital synthesis reduces radio frequency emissions to a level suitable for use in an automotive audio/video communications network.

Abstract: A digital communication system and method is provided for increasing bit-rates while maintaining the reliability of transmitted digital information and avoiding increased power demands. The communication system includes a transmitter that modulates one or more bits onto a carrier signal to generate and transmit a first transmission signal during the first part of a pulse time TB, receives an additional bit, and based on the value of the additional bit, either transmits the first transmission signal again during the second part of the pulse time TB or transmits a second transmission signal during the second part of the pulse time TB.

Abstract: A communication system for transmitting encoded signals over a communication channel is disclosed. The system includes a transmitter, which has a source that is configured to output a plurality of input signals. The transmitter also includes an encoder that is configured to generate a plurality of output signals in response to the plurality of the input signals to output a code word according to the plurality of output signals, wherein the code word has a predetermined algebraic construction for space-frequency coding based upon the communication channel being characterized as a frequency selective block fading channel. Further, the transmitter includes a modulator that is configured to modulate the code word for transmission over the communication channel, and a plurality of transmit antennas that configured to transmit the modulated code word over the communication channel.

Abstract: A method for phase encoding DPSK and N-PSK which maintains phase continuity and which does not require any reference symbols when using N-PSK. A sequence of known DPSK phases are encoded with respect to an initial phase. The N-PSK phases are then all offset by this same initial phase. The known DPSK phases can be used at a receiver to determine a sum consisting of the initial phase and any further phase shift introduced by the channel, and this sum is used to decode the unknown N-PSK phases. The method is more generally applicable to any case where a switch between a phase encoding method which requires an absolute phase reference and a phase encoding method which does not have an absolute phase reference is to be implemented on a single carrier or channel.

Abstract: A BPSK encoder is provided with a first circuit which processes a carrier signal and a binary signal to be encoded, and produces an output binary signal having synchronous phase shifts representing a change in the value of the signal to be encoded. Also, the first circuit is provided with a sampling signal from a second circuit. The second circuit includes a delay circuit to deliver a shifted carrier signal that is smaller than the half-period of the carrier signal, and a logic gate for the logic combination of the carrier signal and the shifted carrier signal. The logic gate also delivers a binary sampling signal having at least two leading or trailing edges at each period of the carrier signal.

Abstract: A stream of complex numbers is converted into polar form, including an amplitude-representative part and a phase-representative part. The amplitude-representative part of each of the converted complex numbers is represented as a plurality of digits of decreasing numerical significance. The phase-representative part of each of the converted complex numbers is phase-modulated at the radio carrier frequency to produce a phase-modulated drive signal. The phase-modulated drive signal is amplified in a plurality of power amplifiers. A respective one of the power amplifiers provides a maximum output power level at a respective amplifier output that is related to a respective one of the decreasing numerical significance. The output amplitude of a respective one of the plurality of power amplifiers is controlled by applying a respective one of the plurality of digits of decreasing numerical significance to a respective one of the plurality of power amplifiers.

Abstract: A method and apparatus for generating digitally modulated signals in which a serial data stream of digital signals to be modulated (70) is provided, the serial data stream being converted into real and imaginary components (74) which are then converted into a complex polar signal (80) representing the serial data stream. A carrier of appropriate frequency is generated by an infinite impulse response filter (84,86) and the polar signal is mixed with the output of the infinite impulse response filter to provide a representation of the complex polar signal modulated at the frequency generated by the infinite impulse response filter (88). Subsequently the imaginary component of the resulting representation is stripped from the signal (90) and the real component of the resulting representation is applied to a digital to analog converter (92) to produce an analog version of the serial data stream.

Abstract: The signal transmission equipment is comprised such that a signal point does not cross the origin of the constellation by selecting signals to be input to the QPSK modulator, and the positions of the signal points in the constellation.

Abstract: The present invention relates to a method and a device for the I/Q demodulation of modulated RF signals. The I/Q demodulator (60) has a first input for the RF signal (61) to be demodulated and a second input for a RF signal (62) originating from a local oscillator (20). The demodulator (60) combines the two RF signals (61,62) to generate three output signals supplied to three power detectors. In a combination unit (70) the three power signals of the power detectors are merged in two signal branches wherein after passing an A/D converting (72) and digital processing unit (73) one signal is the I component and the other one is the Q component of the received modulated RF signal (61).

Abstract: A method and apparatus are provided for use in a transceiver of a wireless system that enable analog mode operations to be performed using in-phase (I) and quadrature (Q) values. The apparatus comprises a processor that performs FM modulation to generate I, Q pairs when operating in the analog mode. When transmitting in the analog mode, the processor encodes a digital representation of the signal to be transmitted into I, Q pairs and outputs the I, Q pairs to a digital-to-analog converter (DAC) comprised by the apparatus. The DAC converts the digital I, Q pairs into analog signals and outputs the analog signals to a cosine wave generator, which generates an in-phase cosine wave and an out-of-phase cosine wave having amplitudes that are proportional to the I and Q values, respectively. The cosine waves are summed for transmission over air. When receiving in the analog mode, a digital down converter converts the received signal into digital I and Q values.

Abstract: An input signal is encoded using a multicarrier code that provides a PEP reduction of 3k [dB] and a minimum distance dmin={square root}{square root over (2k)} d, by restricting the code so as to have one or more 2k+1-carrier kernels in which |&Dgr;&thgr;(2k)−&Dgr;&thgr;*(2k)|≡&pgr; (for any k) holds for the phase difference &Dgr;&thgr;(2k) between a set of 2k−1 carriers and another set of 2k−1 carriers and the phase difference &Dgr;&thgr;*(2k) between a set of 2k−1 carriers and another set of 2k−1 carriers, where k is an integer not smaller than 1. By setting k to 1, and by further providing the condition |&Dgr;&thgr;(2k)−&Dgr;&thgr;*(2k)|=&pgr;/2 between two kinds of 4-carrier kernels one equal in number to the other, a PEP reduction of 3.7 dB and dmin={square root}{square root over (2)} d can be achieved.

Abstract: A method and apparatus for high rate CDMA wireless communication is described. A set of individually gain adjusted subscriber channels are formed via the use of a set of orthogonal subchannel codes having a small number of PN spreading chips per orthogonal waveform period. Data to be transmitted via one of the transmit channels is low code rate error correction encoded and sequence repeated before being modulated with one of the subchannel codes, gain adjusted, and summed with data modulated using the other subchannel codes. The resulting summed data is modulated using a user long code and a pseudorandom spreading code (PN code) and upconverted for transmission. The use of the short orthogonal codes provides interference suppression while still allowing extensive error correction coding and repetition for time diversity to overcome the Raleigh fading commonly experienced in terrestrial wireless systems.

Abstract: A message, e.g., a control message, a short message, a voice message or a data message, is transmitted on at least one of a first communications channel having a first redundancy level or a second communications channel having a second, higher redundancy level. A radio communications signal is received on one of the first communications channel and the second communications channel. The received radio communications signal is demodulated to recover the message using a first demodulation scheme if the radio communications signal is received on the first communications channel and using a second demodulation scheme if the radio communications signal is received on the second communications channel. According to an aspect of the invention, the received radio communications signal is coherently demodulated if the radio communications signal is received over the first communications channel and non-coherently demodulated if the radio communications signal is received over the second communications channel.

Abstract: A phase shift circuit includes a first phase shifter, second phase shifter, and adder. The first phase shifter receives an input signal and obtains first and second intermediate phase shift signals having different phases. The second phase shifter obtains first and second outputs by shifting phases of the first and second intermediate phase shift signals. The adder generates a phase shift output signal by adding the first and second outputs from the second phase shifter. A phase shifting device, oscillation circuit, and image rejection mixer are also disclosed.

Abstract: An adaptive modulation scheme for two streams of information that have different characteristics; preferably voice and data. The voice and data are transmitted on two quadrature channels, the I and Q channels. The amount of power in the channels is adaptively varied. The voice is given all the power it needs for reliable communication over a binary phase shift keying system. The data can have higher data rates, using an M-ary amplitude modulation scheme. The data uses whatever variable amount of power is left after transmitting the voice. The data rate is changed by changing the constellation size, so that a higher bit rate is transmitted, but requiring higher power.

Abstract: A system including coding and decoding circuits provides for resolution of the phase ambiguities in pragmatic trellis-coded PSK modulation transmissions. An error correcting coder, such as a convolutional encoder, precedes the modulator for reducing the effect of noise in inducing phase errors. A corresponding decoder appears at the reception end of the communication system. A differential encoder and decoder automatically remove the possible phase ambiguities, and operate in conjunction with the error correcting encoder and decoder. Each of the ambiguity-removal differential encoder and the decoder act as an operator upon its input signal. In order that both the error correcting encoder and the ambiguity encoder immediately precede the modulator, the ambiguity removal circuitry is placed between the error correcting encoder, and is constructed as a combination of differential encoder and inverse differential encoder.

Abstract: A system for generating a short-range wireless data communication link through an over-the-air channel on a predetermined radio frequency (RF) carrier. The system integrates conventional RF techniques into a low-power and low-cost system for establishing short-range wireless data communication. The system generates short-range wireless data communication links between a transmitting unit (500) that transmits an operating signal carrying data, and a receiver unit (1000) that receives the operating signal without a synthesizer or a heterodyne scheme.

Abstract: The present invention provides a modulation format adjusting optical transponder for receiving an incident optical signal of a first modulation format and outputting an optical signal having a different modulation format. The transponder includes an optical-to-electrical conversion element configured to receive an information-bearing optical signal having a first modulation format and output an electrical signal corresponding to information from the incident optical signal. The transponder includes a laser for outputting an optical carrier signal at a selected wavelength and a modulator communicating with the optical-to-electrical conversion element and with the laser. The modulator places the information from the incident optical signal onto the optical signal output by the laser, creating a modulated optical output signal having a second modulation format different from the first modulation format.

Abstract: A signal generator for producing a plurality of signals having the same frequency but a constant phase difference includes first and second cavity oscillators coupled to each other via an appropriate wall and coupling apertures. A first output signal is extracted from the first oscillator at a first predefined location on the oscillator's outer wall, which location defines a first angle relative to the wall aperture which couples the first oscillator to the second. A second output signal is extracted from a predefined location on the outer wall of the second oscillator, which location defines a second angle relative to the aperture in the first oscillator. Because the two oscillators are coupled to each other, they will produce an output signal having substantially the same frequency. The phase difference between the two output signals is defined by the difference between the first and second angles.

Abstract: A radio communication device using a quadrature modulation-demodulation circuit which enables DC offset error fluctuation to be corrected more accurately regardless of the condition of temperature variation or power source voltage fluctuation. A quadrature demodulation circuit inputs therein a QPSK signal to output a base band signal perpendicularly intersecting to the QPSK signal. A base band signal generation circuit inputs therein a transmission data to convert into two analog base band signals perpendicularly intersecting with each other. A quadrature modulation circuit inputs therein the analog base band signal and modulated frequency signal to output the QPSK signal. A switching circuit selects either one of the analog base band signal and the QPSK signal. An A/D conversion circuit quantizes an output signal of the switching circuit. An offset error detecting means detects DC offset error.

Abstract: An improved method and system for generating quadrature phase shift keying signals for use in data transmission is provided. A pair of oscillators are slaved to the transmit frequency and produce two quadrature signal components with the same frequency but 90 degrees out of phase. The two signal components are carried to separate bi-phase switches by mirrored waveguides. Each bi-phase switch has a reflective waveguide coupler which directs the received signal into a waveguide terminated by a hard short and has a controllable shorting plane spaced approximately one-quarter wavelength from the termination point. The shorting planes are controlled by the output data signals and each introduces a 180 degree phase shift in the respective signal component when activated. The reflective couplers direct the selectively phase shifted signal components to an in-phase combiner, where they are combined to produce the quadrature phase shift keyed output signal.

Abstract: The data storing method includes the steps of: (a) receiving a data encoded signal; (b) sampling the received data encoded signal at a first sampling rate; (c) counting the number of consecutive samples at a first logic level; (d) storing the number of samples counted in step (c) in a first portion of a memory template; (e) counting the number of consecutive samples at a second logic level; (f) comparing the number of samples counted in step (e) to a threshold value; (g) changing the sampling rate at which the received data encoded signal is sampled and counting the number of consecutive samples at the second logic level if the number of samples counted in step (e) exceeds the threshold value; and (h) storing in the memory template, the number of samples counted in step (e) if the threshold was not exceeded, or the number of samples counted in step (g) if the threshold value was exceeded. The apparatus includes a processor programmed to perform the above steps.

Abstract: Methods, apparatus and system for transmitting signals in QPSK, QAM and other similar modulation formats as single sideband (SSB) signals. An exemplary SSB-QPSK transmitter receives an in-phase data signal and a quadrature-phase data signal. The in-phase data signal and a Hilbert transform of the quadrature-phase data signal are modulated onto a cosine carrier signal, the quadrature-phase data signal and a Hilbert transform of the in-phase data signal are modulated onto a sine carrier signal, and the modulated sine and cosine carrier signals are combined to provide a modulated SSB-QPSK signal. The in-phase and quadrature-phase data signals are time-aligned signals which are interpolated prior to modulation so as to include zero values at alternating instants of time. Their corresponding Hilbert transforms therefore also exhibit alternating zero values.

Abstract: To achieve economy of a transmission path with good quality of transmission and low expenditure compared to previous codes such as 4PSK-64PSK, the invention provides higher-value pulse duration encoding, such that there is provided only an alternating current of a frequency and phase position, with code elements of different pulse durations which are encoded by a different number of periods or half-periods. The following duration pulse is marked by an amplitude change.

Abstract: A method and a system for detecting a user signal in a CDMA network. (Coded) user message bits are grouped into successive groups. A differential phase is generated for each message bit group by mapping each message bit group on to a predetermined PSK constellation. An absolute phase is generated for each message bit group based on the differential phase for the current message bit group and the absolute phase for the preceding message bit group. The absolute phase signal is phase keyed to an RF carrier to form an RF signal. The RF signal is spread using two code sequences and the spread RF signal is transmitted. At the receiver, the RF signal is received and non-coherently demodulated. The demodulated RF signal is despread using the code sequences. Successive blocks of the demodulated, despread RF signal are phase compared for extracting the differential phase signal carrying the (coded) user message. Lastly, the user message is recovered.

Abstract: The present invention relates to a transmission device and a transmission method which can efficiently perform transmission of audio signals with infrared ray and suppress the complication of data processing in modulation and demodulation processes to the minimum level. Audio signals reproduced by a digital audio instrument are transmitted to and recorded into a digital audio recorder through an audio signal transmission device by infrared ray. In the digital audio recorder, the recorded audio signals are immediately reproduced, transmitted and output to a digital audio instrument through an audio transmission device with infrared ray. In the transmitters, a transmission channel clock having the frequency of 5/4-times the data clock thereof from the audio signals, and modulated signals obtained by modulating the audio signals are output at the timing of the transmission channel clock.

Abstract: The combined complementary encoder and modulation system for an OFDM transmitter system combines complementary coding and modulation and exploits the similarity of their mathematical structure to reduce implementation complexity. In doing so, the improved OFDM transmitter system uses complementary codes to reduce the power-to-average power (PAP) ratio of the transmitted signal. Additionally, the combined complementary encoder and modulation system can be modified to provide scaleablity, which allows a transmitter to operate in various transmission environments. More precisely, scaleability refers to the transmitter's capability to adapt the bit rate of the data, so as to satisfy varying signal bandwidth, delay spreads, tolerance and signal-to-noise ratio requirements.

Abstract: A method of detecting a phase associated with a sinusoidal signal over a period associated with the sinusoidal signal, the method comprising the steps of: sampling the sinusoidal signal at a prescribed sampling frequency every period thereby generating a plurality of sampling values; converting the plurality of sampling values to a plurality of digital values; respectively evaluating said plurality of digital values within a first period and a latter period associated with the period of the sinusoidal signal, the evaluation of each period generating respective resulting digital values; and determining the phase associated with the sinusoidal signal according to the resulting digital values of the first period and the latter period.

Abstract: Apparatus for generating the family of PSK (phase shift keyed) modulations, which include BPSK (binary PSK), QPSK (quaternary PSK), MSK (minimum shift keying) and the like. The carrier is generated with the desired digital information already phase-modulated onto it by directly introducing a phase shift or delay onto the error path of a phase-locked loop. causing the phase-locked loop to create the phase modulation. The [proposed scheme differs from common practice approaches, which are usually implemented by linear synthesis (an AM technique); rather, it] invention employs direct nonlinear synthesis (an FM technique). The invention [yields good phase precision with arbitrary spectral shaping under the constraint of constant envelope signaling. It] permits the connection of the output of a simple, inexpensive VCO (voltage controlled oscillator) directly to a system's antenna without the need for intervening circuit elements such as phase splitters, mixers, and the like which is applicable to [.

Abstract: A digital signal processor is provided which is compatible with a large variety of modulation processes (e.g., BPSK, QPSK,.pi./4 QPSK, M-ary FSK and M-ary PSK). The processor has a transmit section which can convert input data streams into baseband I and Q signals and a receive section which can recover data streams from input baseband I and Q signals. The transmit section includes a direct I/Q modulator and a common phase modulator and the receive section includes an M-FSK to M-PSK converter and a common phase demodulator. The processor is particularly suited for realization as an application-specific integrated circuit (ASIC) which can be integrated in multiband, multimode transceivers.