Abstract: A method and apparatus are provided that performs timing acquisition for multiple radio terminals. According to one aspect of the present invention the invention includes receiving a sequence of symbols modulated onto a carrier frequency over a channel and demodulating the symbols using a clock frequency. The invention further includes determining a frequency offset of the received symbols with respect to the clock frequency and applying the determined frequency offset to adjust the clock frequency.

Abstract: A modulator phase shift keying modulator for performing data modulation by using the phase difference of each I/Q channel, comprising a data shifter for controlling delay of I/Q channel digital data at input terminals of the I/Q channels.

Abstract: The invention relates to a method for generating an I/Q signal for an I/Q modulator (10). Said signal is composed of two or more data streams, which have been edited according to identical or different digital modulation methods. In said method, a known modulation encoder is used to generate corresponding digital I/Q values from a first inputted digital data stream. Said I/Q values then undergo a digital-analogue conversion (8) that generates the corresponding analogue I/Q signals. The invention is characterised by an additional modulation generator that calculates digital I/Q values, or generates I/Q values from an additional inputted digital data stream. The digital I/Q values of the modulation encoder and the digital I/Q values of the modulation generator (10) are then added together, using digital adders (A3) located upstream of the digital-analogue converter (8).

Abstract: A power balanced photonic RF phase shifter includes: a microwave drive; a phase controller operably connected to the microwave drive; and a linearizing arm connected in parallel with the microwave drive, the linearizing arm operating under a bias voltage, Vlin, that is controlled such that power variations of the photonic RF phase shifter are mitigated. In a preferred embodiment, the bias voltage, Vlin, is controlled to keep an optical phase of the photonic RF phase shifter at a constant value. In a preferred embodiment, the microwave drive, the phase controller and the linearizing arm comprise (three) Mach-Zehnder modulators.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector detects the presence of particular data states that are expected to result in particular modulation states or transition locations. When a particular data state is detected the IQ correction code compares the detected scalar magnitude with others that have been detected. The IQ correction code then uses the comparison to generate adjustments for I and Q offsets, I/Q phase, and I/Q gain. In a rotation embodiment, the modulation system further includes a rotation signal generator for generating rotation angles and an IQ rotator for applying the rotation angles for rotating the I and Q digital data streams.

Abstract: A method for generating a frequency-modulated signal with high receivability quality, comprising the steps of: before sending an input modulating signal to a modulator, modifying the input modulating signal so as to compensate for distortions which will be introduced in the modulated signal receiving section.

Abstract: A system and method for producing a phase corrected M-QAM signal is described. In one embodiment, a phase-correcting M-QAM modulator comprises a feedback loop for dynamically adjusting the phase relationship between the two carrier signals as a function of the difference between the phase relationship of the two carrier signals and the phase relationship of the I and Q input signals. In another embodiment where a second carrier signal is derived from the first carrier signal by means of a phase shifting circuit, the amount of phase shift applied to the first carrier signal is a function of the difference between the phase relationship of the two component signals comprising the output QAM signal and the phase relationship between the input I and Q signals.

Abstract: An autocalibrating modulating array transmitter 10 and autocalibration method 30. The autocalibrating modulating array transmitter is used to gain-balance and phase-balance parallel amplifier stages 11 for coherent combining. The novelty of the autocalibration technique involves periodic substitution of calibration symbols into a valid data stream, the use of only the error magnitude (as opposed to magnitude and phase), and a random selection of either gain or phase adjustments to avoid limit cycles.

Abstract: A method for self-calibrating a vector modulator is disclosed, including the step of pre-distortion coefficients in dependence upon an in-phase signal, a quadrature signal, and an output envelope of an RF signal, and further comprising the steps of transforming a value representative of an output envelope represented in a nonlinear domain into a value representative of the output envelope represented in a linear domain, determining a parameter vector x as a solution of a linear equation within the linear domain, and determining the pre-distortion coefficients from the parameter vector x.

Abstract: An improved constellation pruning and partial Gray coding method for generating constellations that are transmitted by a transmitter. The approximate symbol error rate (SER) for each possible subconstellation is first determined. Then, each of the subconstellations are scaled in terms of power so that each subconstellation has the same symbol error rate. Then, the subconstellation that requires the least amount of power to generate is selected as the pruned constellation for use by the transmitter. After the pruned constellation is determined, it is then coded a single time, and this coded pruned constellation is used by the transmitter.

Abstract: An oscillation circuit uses a SAW oscillator and is able to control the oscillation frequency easily and correct the temperature characteristic of the oscillator so that an oscillation signal with high temperature stability can be generated. A clock signal CLK having a prescribed frequency difference from the ideal oscillation frequency is generated by the SAW oscillator 10. Register 30 is driven by a frequency-divided clock signal obtained by dividing the frequency of the clock signal at a predetermined frequency division rate. In-phase signal SI and quadrature signal SQ generated corresponding to the data Da that is incremented by a prescribed addition value F every period of the frequency-divided clock signal are output, and the clock signal is IQ-modulated on the basis of these signals. The frequency error of clock signal CLK can be corrected, and an output signal Sout having near ideal oscillation frequency can be obtained.

Abstract: Precision inphase/quadrature up-down converter structures generally neither requiring trimming at the time of fabrication nor calibration during use. The converters use four mixers arranged to down convert to provide Q, I, {overscore (I)}and Q baseband signals (or up convert Q, I, {overscore (I)} and Q baseband signals), the combination of which signals has a very substantially reduced unwanted image frequency content. The use of an increased number of mixers in effect shifts the primary errors from absolute gain and phase errors, to gain and phase error mismatches between elements in replicated circuits, which mismatches can be held to a minimum in circuits replicated in a single integrated circuit.

Abstract: A dual-mode radiotelephone capable of operation in analog or digital modes. According to exemplary embodiments, a digital signal processor receives a speech signal to be transmitted in the digital or analog mode and generates In-phase (I) and Quadrature (Q) modulating signals. The I and Q signals are supplied to a quadrature modulator for generating a digitally modulated signal and are supplied to an analog modulator for generating an analog modulated signal.

Abstract: A device for modulating a carrier signal comprises a mapper generating a baud rate data signal at a first data value frequency. A complex mixer and an upsampling device are used to increase the data value frequency and spectrum shift the data signal. A finite impulse response filter operating on the data signal to generate filtered first signal with characteristics that provide for reduced side band noise when the filtered signal is mixed to generate a quadrature amplitude modulated carrier.

Abstract: A narrow bandwidth signal, such as a narrowband FM signal, is modulated in a modulator that modulates a wide bandwidth signal, such as a CDMA signal, by oversampling the narrow bandwidth signal and applying the oversampled narrow bandwidth signal to the modulator. By oversampling the narrow bandwidth signal, the same fixed low pass filter can be used for both the wide bandwidth signal and the oversampled narrow bandwidth signal. Accordingly, different low pass filters or switched low pass filters are not needed. The DC offset that is introduced by the digital-to-analog converter and/or the low pass filter of the modulator is compensated, preferably in the digital domain, to thereby reduce DC offset within acceptable limits for the modulation that is being used. More preferably, compensation is provided by subtracting from the sampled signal, a digital value representing the DC offset in the filtered analog signal that is introduced by the digital-to-analog converter and/or the low pass filter.

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: 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 double up-conversion modulator includes a first conversion stage (1) formed of two modulation units (101, 102), receiving at one input quadriphased baseband signals, controlled by four quadriphased carrier signals at a first intermediate frequency (IF1), and delivering at one output opposite up-converted signals (IF1C, IF1C_b) at said first intermediate frequency. The modulator further includes a second up-conversion stage (2) receiving at one input said up-converted signals at said first intermediate frequency, controlled by two other in phase opposition carrier signals at a second intermediate frequency (IF2), and delivering at one output a high frequency signal (HF_M), said high frequency (HF) corresponding to the sum of said first and second intermediate frequencies (IF1+IF2).

Abstract: Disclosed is a digital modulation apparatus which comprises a quadrature amplitude modulation unit for modulating first and second baseband digital signals orthogonal to each other by means of digital cosine/sine information obtained based on information regarding a carrier frequency which is n multiple of a local frequency and a phase rotation unit provided in the input side of the quadrature amplitude modulation unit for performing phase rotation for the first and second baseband digital signals by using a difference frequency equivalent to a difference between the local frequency and a a baseband frequency. A frequency is converted into a transmitted frequency without using an analog circuit for conversion into a second frequency, a limit value of this transmitted frequency is increased, and a circuit is fully digitized to simplify and miniaturize a circuit configuration. As a result, the turning of the circuit into LSI can be facilitated, and high accuracy and high cost effectiveness can be promoted.

Abstract: A modulator for modulating carrier wave signals with an in-phase component signal and a quadrature component signal includes a fixed frequency signal generating means for generating two fixed-frequency signals differing 90 degrees in phase, a variable frequency signal generating means for generating a signal whose frequency can be varied according to a modulated signal to be produced, an in-phase component carrier wave signal generating means for mixing one fixed-frequency signal and the variable-frequency signal to generate a carrier wave signal for an in-phase component, a quadrature component carrier wave signal generating means for mixing the other fixed-frequency signal and the variable-frequency signal to generate a carrier wave signal for a quadrature component, an in-phase component modulating means for modulating the in-phase component carrier wave signal with the in-phase component signal, and a quadrature component modulating means for modulating the quadrature component carrier wave with the quadr

Abstract: Disclosed is a digital communication system for mobile communication, which has: a transmitter for mixing and outputting outputs from two independent and equivalently synchronized transmitting circuits in a &pgr;/4 shift QPSK modulation system; and a receiver for receiving a mixed wave transmitted from the transmitting circuits and demodulating the received signal by using information as to its phase and amplitude.

Abstract: A point-to-point microwave radio link that operates in a Frequency Division Duplex (FDD) mode using direct digital modulation with a Continuous Phase Shift Keyed (PSK) scheme. The transmit signal is generated by a circuit that uses a Voltage-Control Oscillator (VCO) operating in a microwave radio band to obtain the modulated signal. The VCO output is fed to a phase modulator to obtain the modulated signal. The output of the VCO is then frequency multiplied by the predetermined factor to produce the modulated microwave output signal at the desired band.

Abstract: A method and apparatus for carrierless amplitude and phase CAP encoding of data in a manner avoiding the use of pulse shaping filters for in-phase and quadrature impulse signals. Specifically, in-phase and quadrature vector arithmetic structures (VAS) to adapt respective in-phase and quadrature impulse components to produce appropriate shaped in-phase and quadrature components.

Abstract: A frequency converter comprising a variable gain amplifier which amplifies the local oscillation signal according to a gain control signal and outputs an amplified local signal, an even harmonic mixer which is supplied with an input signal and an amplified local oscillation signal and outputs an output signal whose frequency is a sum of a first frequency of the input signal and a second frequency of two or more even numbered times a frequency of the amplified local oscillation signal, an amplitude detector which is supplied with the amplified local oscillation signal and outputs a direct current signal having an amplitude corresponding to an amplitude of the amplified local oscillation signal, and a comparator which compares the direct current signal of the amplitude detector with the reference direct current signal to generate an output signal as the gain control signal.

Abstract: A multi-protocol modulator capable of supporting two or more different modes of operation, each mode of operation corresponding to a different type of modulation, comprises an m-level phase shift keying (m-PSK) modulator which receives a serial input data stream and maps data contained therein into a constellation including m equidistant phases in accordance with a predetermined mapping scheme. The m-PSK modulator is shared by at least two different modulation protocols by allowing the mapping scheme to be selectively changed depending upon the modulation protocol used. The multi-protocol modulator further includes a phase rotator operatively coupled to the output of the m-PSK modulator. The phase rotator selectively rotates the phase of the m-PSK signal by a predetermined phase rotation value. The phase rotator is shared by the two or more modulation protocols by allowing the phase rotation value to be selectively modified depending upon the modulation protocol used.

Abstract: Left and right stereo audio information is reproduced from a compatible quadrature amplitude modulation (C-QUAM) broadcast using two separate modes of detection. In the first mode, a true C-QUAM detection is performed when the signal being received has a high level of stereo difference information. In the second mode, a synchronous detection approximation is used which avoids generating an envelope signal or calculating a cosine correction factor as in true C-QUAM decoding. The second mode is used when over-modulation is present in the received signal.

Abstract: Training sequences designed for N-VSB systems within the embodiment of an N-squared QAM receiver facilitate designing 8-VSB receivers using methodologies of 64-QAM receiver design. A receiver designed using such methodologies converts the received modulation into a signal which can be accepted by circuitry for decoding 64 level quadrature-amplitude modulation (64-QAM) signals. This process provides a better signal to noise ratio reception than the conventional I-channel only decoding circuitry of most 8-VSB receivers. This process also employs training and equalizing algorithms developed for 64-QAM receivers which are superior to equivalent algorithms for 8-VSB receivers. The invention can be generalized to N-VSB conversion into M-QAM where M=N2. Adaptive equalization algorithms for 8-VSB transmissions implemented within the context of the 64 QAM receiver are superior to present single-channel VSP processing receivers.

Abstract: The successive symbols of a digital stream are converted into phase increments which are accumulated. A modulating phase is obtained by filtering the accumulated phase. A complex signal is produced whose argument represents the modulating phase. Two quadrature radio waveforms are respectively modulated on the basis of that complex signal, and a radio signal resulting from a combination of the two modulated waveforms is transmitted. The complex signal may be filtered digitally. Its real and imaginary components are converted into analog form, and are subjected to anti-aliasing analog filtering and then mixed with the two radio waveforms. Appropriate sizing of the digital filters provides efficient modulation with small envelope variations, causing little adjacent channel interference and a low error rate.

Abstract: A non-linear distortion compensation circuit and method automatically sets to an optimal value a phase shift of a variable phase shifter and an attenuation of an attenuator according to a transmission frequency, in a non-linear distortion extractor for extracting a non-linear distortion component generated during non-linear high-power amplification. A variable phase shifter shifts adjusts a phase of a signal determined by quadrature modulating the baseband signal. A high-power amplifier non-linearly high-power amplifies the quadrature-modulated signal. An attenuator attenuates the amplified signal by a gain equal to that of the high-power amplifier. A subtracter extracts non-linear distortion generated during the non-linear high-power amplification by subtracting the phase-shifted quadrature-modulated signal from an output of the attenuator. A control circuit automatically adjusts a phase shiftof the variable phase shifter and an attenuation of the attenuator according to a transmission frequency.

Abstract: Binary and Quadrature Feher's (F)-Modulation/Transmitter-Receiver (Transceiver) with reduced envelope fluctuations and peak radiation, increased efficiency delivered by baseband, intermediate frequency (IF) connected RF (radio frequency), Infrared (IR) and other devices. A subclass of these systems has a constant envelope. Power advantages, robust BER performance and linearly or nonlinearly amplified narrow spectrum without the pitfalls of conventional BPSK, DBPSK QPSK and pi/4 QPSK is attained. Feher's FBPSK improved efficiency transmitter is compatible with conventional BPSK receivers. FBPSK modems are based on using quadrature structure where Q channel data is inserted in quadrature with I channel data for certain applications. The Q channel data is “offset” from the changed data by an amount selectable between zero (0) and a specified time. Further improvement in the spectrum is attained using correlation between I and Q channels. FBPSK modem is shown to meet the IEEE 802.

Abstract: A low-noise quadrature phase I-Q modulator having a pair of Gilbert cell input stages driven by a feed voltage line and receiving in input respective square wave command signals coming from a local oscillator. The modulator comprises a transistor block with transistors connected to each cell and destined to carry out a voltage-current conversion of a signal in radio frequency received from the block itself; such block further including a single degeneration resistance.

Abstract: A 2N-QAM macrocell for generating constellations with 2N symbols, where N is the number of bits in the digital data word [D0:DN−1] applied to the macrocell. Since the digital data word is applied directly to the macrocell, the need for a digital mapping chip is thus eliminated thus reducing the complexity and power consumption of the circuit. An important aspect of the invention is that the 2N-QAM macrocell is amenable to being fabricated as a single microwave monolithic integrated circuit (MMIC) or integrated circuit (IC). As such, a QAM circuit can be formed from two MMICs; the 2N-QAM macrocell and a quadrature hybrid phase shifting device formed on separate MMIC to form a 2N-QAM circuit or one MMIC containing both the 0/90 degree phase shifter and the 2N-QAM circuit. The phase shifting device is used to provide the in-phase and quadrature phase components of the local oscillator signal.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes digital filters for converting I and Q data bit streams into filtered multilevel I and Q digital data streams, digital-to-analog converters for converting the digital data streams from digital to analog form, and an IQ modulator for converting the analog I and Q data streams into a modulated output signal having a representative IQ diagram having modulation states and transition locations between the modulation states. The digital filters include forward shifting memories having several samples of the data bit streams for each data bit time. The system also includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector monitors the data states in the memory and detects the presence of particular data states that are expected to result in particular modulation states or transition locations.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes digital filters for converting I and Q data bit streams into filtered multilevel I and Q digital data streams, digital-to-analog converters, and an IQ modulator for converting the analog I and Q data streams into a modulated output signal having a representative IQ diagram having modulation states and transition locations between the modulation states. The system also includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector monitors the data states in memories of the digital filters and detects the presence of particular data states that are expected to result in particular modulation states or transition locations. The amplitude detector monitors the modulated output signal and provides representative detected magnitudes.

Abstract: A transmitter has a phase modulator and a phase locked loop that has a relatively high powered voltage controlled oscillator. The phase locked loop has a phase sensitive detector for comparing a phase comparison frequency derived from the voltage controlled oscillator output with a phase modulated intermediate frequency carrier derived from the phase modulator. The phase modulator has a reference frequency source, means for deriving four quadrature phase components of the reference frequency produced by the source and phase selection means controlled by complex modulation means for deriving the phase modulated intermediate frequency carrier by random interpolation between the four quadrature components.

Abstract: Clock signals and digital data signals at a variable frequency are introduced to the input of a FIFO and are passed from the FIFO at a second (or intermediate) frequency controlled by a numerically controlled oscillator. To regulate the frequency of the signals from the numerically controlled oscillator, the phases of the clock signals at the variable frequency are compared in a phase detector with the phases of the signals from the numerically controlled oscillator to generate an error signal. The error signals and the signals at a fixed sampling frequency higher than the intermediate frequency regulate the frequency of the signals from the numerically controlled oscillator and thus the frequency of the digital data signals from the FIFO. The digital data signals from the FIFO are converted to a pair of signals at the second frequency.

Abstract: A baseband signal modulator provides a phase and amplitude modulated carrier signal. First and second phase modulators each receive a common reference signal and derive therefrom a carrier signal frequency. The phase modulators each receive a respective pair of phase-encoded data signals so as to provide respective first and second phase-encoded carrier. The modulator outputs are summed to provide the phase and amplitude modulated carrier signal. Each phase modulator includes a respective phase locked loop incorporating an oscillator locked via the common reference signal to the carrier signal frequency, and a phase adder having a first input for receiving the carrier frequency signal and having second and third inputs for receiving the respective pair of data encoded signals.

Abstract: A variable-rate QAM (Quadrature Amplitude Modulation) transceiver of the present invention facilitates data interfacing between a number of bands having different transmission rates by using a number of transmitters and receivers in downstream and upstream, respectively, to provide a symmetric service in which data transmission rate in upstream is equal to that in downstream even under environment of serious channel attenuation of a signal for high frequency. That is, the variable-rate QAM transceiver of the present invention comprises a number of transmitter blocks for providing various transmission rates to the transmitters and a number of receiver blocks for providing various transmission rates to the receivers, for properly adjusting bandwidth allocation of the passband signal bandwidth of a number of transmitters and receivers to enable high speed symmetric data transmission.

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 semiconductor integrated circuit device includes an orthogonal modulator that maintains carrier leak characteristics regardless of attenuation of an output signal level. The orthogonal modulator includes a phase shifter circuit and generates a modulation signal. An auto gain controller amplifies the modulation signal to generate an amplified modulation signal. A gain adjusting circuit adjusts a gain of the phase shifter circuit in accordance with a control signal.

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: A digital signal processor generates in-phase, quadrature-phase and amplitude signals from a baseband signal. A modulator modulates the in-phase and quadrature-phase signals to produce a modulated signal. A phase locked loop is responsive to the modulated signal. The phase locked loop includes a controlled oscillator having a controlled oscillator input. An amplifier includes a signal input, amplitude control input and an output. The signal input is responsive to the controlled oscillator output and the amplitude control input is responsive to the amplitude signal. The phase locked loop that is responsive to the modulated signal includes a controlled oscillator output and a feedback loop between the controlled oscillator input and the controlled oscillator output. The feedback loop includes a mixer that is responsive to a local oscillator. The modulator may be placed in the phase locked loop.

Abstract: A circuit configuration for a QAM transmitter contains a Cordic for converting the baseband signal to the radio frequency band. The complex output signal from the Cordic is converted to the carrier frequency by interpolation filters. Different signal paths can be selected for a lower and an upper frequency band for the carrier signal. The signal paths each use identical filter parts. Therefore, the circuit need be operated at only half the sampling rate of the output signal as far as a multiplexer on the output side.

Abstract: A distortion compensating apparatus for use in IQ modulation and demodulation techniques wherein a first distortion arrangement distorts the I-signal by adding to the I-signal a first weighted function of the I-signal and a first weighted function of the Q-signal and a second distortion arrangement distorts for Q-signal by adding to the Q-signal a second weighted function of the I-signal and a second weighted function of the Q-signal, such that the weighted functions of the I-signal are independent of the Q-signal and the weighted functions of the Q-signal are independent of the I-signal. This enable distortions to be compensated in both sidebands of the IQ modulated signal.

Abstract: A &pgr;/4 DQPSK modulator includes a rotated and offset &pgr;/4 encoder that provides encoded I, Q constellation indices values using positive integers. The positive integer I and Q values are input to a digital filter that provides filtered I, Q constellation indices values. These filtered values are then rotated and offset back to conventional &pgr;/4 DQPSK constellation values, modulated and transmitted. Since the rotated and offset &pgr;/4 encoder provides I, Q constellation indices as positive integers, the filters are implemented as multiplierless digital filters which significantly reduces the complexity of the filters. Specifically, the multiplierless digital filters can be implemented using shift registers and summers. In a preferred embodiment the filters are programmable. In addition, using positive integers to represent the rotated and offset &pgr;/4 signalling constellation indices allows the indices to be represented as a binary value with less bits in contrast to prior art systems.

Abstract: A signal generator includes an oscillator, a phase locked loop and a fractional divider. The oscillator is configured to provide an output signal. The phase locked loop is configured to receive the output signal and to provide a tuning signal to the oscillator. The phase locked loop has a phase detector configured to receive the output signal, to compare the output signal to a reference signal, and to provide the tuning signal to the oscillator based on the comparison. The fractional divider is outside of the phase locked loop and is configured to generate the reference signal.

Abstract: A digital communications system (10) employs a rotationally invariant phase point constellation (80, 80′, 80″) in a modulator (12) thereof and a corresponding carrier phase acquisition phase locked loop (56, 66, 74, 76, 78) in a demodulator (14) thereof. The phase point constellation (80) is rotationally invariant and the demodulator (14) is able to achieve carrier phase synchronization due at least in part to the inclusion of phase point voids (94) positioned in the phase point constellation (80, 80′, 80″). Pragmatic encoding is employed with differential encoding (28, 64) only on non-convolutionally encoded bits. The phase point constellation (80, 80′, 80″) provides identical codes for convolutionally encoded bits (30) of phase points (84) having equal magnitude that are rotated 90°, 180° and 270° degrees from one another. Specific constellations of 256, 64 and 16 points are disclosed.

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: A method 1100 and apparatus 1200 utilizing unbalanced modulation for providing users in a communication system with different amounts of effective communication energy according to their individual communication environments. A user's communication energy needs are determined based on conditions such as weather, signal-to-noise ratio, and cell location. Signals destined for a user are modulated according to the determined needs of the user. A signal destined for a user operating in a relatively friendly communication environment is modulated with less effective energy than a signal destined for a user operating in a relatively hostile communication environment.

Abstract: Power amplifier circuit incorporating a negative feedback circuit for a transmitter and phase control method therefor. An I-component test signal and an I-component baseband feedback signal are added for generating an I-component summing signal. A Q-component test signal and a Q-component baseband feedback signal are added for generating a Q-component summing signal. A carrier is orthogonally modulated with the I- and Q-component summing signals. A part of the modulated signal is orthogonally demodulated with the carrier, whereby I-component baseband feedback signal and Q-component baseband feedback signal are outputted. Phase of the carrier is changed in accordance with a phase control signal for holding the phase of the carrier at a time when the detected state of one of the i- and Q-component summing signals as selected meets predetermined condition.