Abstract: A technique is described for simultaneously and synchronously transmitting digital data and a clock signal in a digital integrated circuit, circuit board, or system. The technique is based on the phase shift keying (PSK) modulation of an RF high frequency carrier which is distributed on low impedance interconnection transmission lines. The PSK modulation contains the digital data while the carrier itself constitutes the clock signal, and the clock signal and digital data are transmitted in a synchronous manner. The carrier frequency may be near fT, the maximum operation frequency of the transistors. Since the digital data and clock signal are simultaneously transmitted on the same interconnection, the digital data never becomes skewed with respect to the clock signal, or vice versa.

Abstract: A received continuous phase modulation (CPM) signal (which is formed with a set of pulse shaping functions) is approximated as a phase shift keying (PSK) modulated signal (which is formed with just the dominant pulse shaping function having the largest energy). Channel estimation and data detection are performed in accordance with the CPM-to-PSK approximation. A signal power estimate and a noise power estimate are obtained for the received CPM signal and have errors due to the CPM-to-PSK approximation. The difference ? between the energy of the dominant pulse shaping function and the energy of the remaining pulse shaping functions is determined. An approximation error is estimated based on the signal power estimate and the difference ?. A C/I estimate for the received CPM signal is computed based on the signal power estimate, the noise power estimate, and the approximation error estimate.

Abstract: All practical communication channels impose some type of corruption on received data through inter-symbol interference (ISI). ISI corruption is particularly acute in high-order constellation transmission. Although ISI effects of high-order constellation transmission are very large on average, some symbols may be received that suffer relatively low levels of ISI. These symbols are “reliable symbols” and can be used to provide blind estimation of the ISI coefficients. Once the ISI effects of a channel are known, all captured signals may be corrected.

Abstract: A fast equalization technique is disclosed for systems using high-order constellations where symbols have been corrupted by data correlated noise (ISI). The technique permits ISI estimation to begin immediately upon receipt of captured samples. Training symbols are not required for the operation of the equalization technique. ISI estimation is weighted in accordance to a reliability factor of each captured sample.

Abstract: A system for and method of modulating and demodulating a communication signal using differential quadrature phase shift keying (DQPSK) can include, upon receiving an inbound communication signal, demodulating the inbound communication signal by obtaining Pi/4 differential quadrature phase shift keying (DQPSK) symbols, translating the Pi/4 DQPSK symbols into quadrature phase shift keying (QPSK) symbols, and mapping the QPSK symbols to a pair of bits. Upon initiating an outbound communication signal, the system and method can include modulating the outbound communication signal by obtaining communication bits indicative of the outbound communication signal, translating the communication bits to three communication bits, and mapping the translated bits to DQPSK symbols.

Abstract: The invention proposes the separate processing of the phase and amplitude of multi-amplitude digital modulation techniques, such as a QAM. The phases are differentially modulated and the amplitudes coherently processed. Also proposed is a method to correct the amplitude distortion of the symbols on each subcarrier, either from the QAM signal itself or from any PSK signal, if available. The invention shows that differential modulation/demodulation of multi-amplitude signals with no equidistant phases such as QAM is possible. Complex equalizer means to perform a channel estimation is no more needed as for coherent systems. Further, no pilot sucarriers are needed, thus the bandwidth efficiency is much higher. Furthermore, the frequency snychronization of differential demodulated signals is less complex. An implementation proposal of the new modulation/demodulation technique is described.

Abstract: A coding section 101 performs error detection coding of data for each predetermined error detection unit, and an M-ary modulation section 102 arranges data belonging to a plurality of error detection units in one transmission unit, and transmits that data. A first decoding section 114 decodes a received signal, and performs error detection on the decoding result for each error detection unit. A second demodulation section 115 modifies the likelihood of each bit based on the result of error detection in the first decoding section 114. By this means, it is possible to improve the error correction capability of a signal that has undergone M-ary modulation using high-precision likelihoods, and to improve transmission quality.

Abstract: A method and apparatus that differentially encodes and decodes data symbols in dual domains is taught. Data packets are encoded, transmitted, and decoded during a plurality of symbol intervals on a plurality of sub-carriers. Encoding and decoding are accomplished across both the time and frequency domains such that the minimum number of carrier states are employed as reference only states that do not encode a symbol of data in and of themselves. A rule of adjacency is followed, both across time and frequency, so that decorrelation is minimized. Any modulation scheme that is applicable to differential encoding and decoding can be utilized. Communication systems that couple via radio waves, through metallic conductors, or over fiber optic paths can be employed.

Abstract: The present invention discloses an improved method of timing synchronization with transmitted data packets in a receiver on a communication channel using differential phase shift keying (DPSK) modulation—especially an RF wireless communication channel. The invention reduces the complexity of the circuits, especially the multipliers, required for digital signal processing. The invention also increases performance compared to previously known methods.

Abstract: A method of increasing the speed of a transmitter by storing in look-up tables, modulation, spread, over-sampled and filtered samples of modulated data bits having an I and Q. The bits I and Q are differentially modulated, and the tables are indexed based on the differential modulation.

Abstract: A technique is described for simultaneously and synchronously transmitting digital data and a clock signal in a digital integrated circuit, circuit board, or system. The technique is based on the phase shift keying (PSK) modulation of an RF high frequency carrier which is distributed on low impedance interconnection transmission lines. The PSK modulation contains the digital data while the carrier itself constitutes the clock signal, and the clock signal and digital data are transmitted in a synchronous manner. The carrier frequency may be near fT, the maximum operation frequency of the transistors. Since the digital data and clock signal are simulaneously transmitted on the same interconnection, the digital data never becomes skewed with respect to the clock signal, or vice versa.

Abstract: A tangent angle computation device and associated DQPSK decoder. The computation device uses an eight-bit divider and a four-quadrant technique for finding a quantized angular value from an incoming signal. The quantized angular value is subsequently used to decode the incoming signal.

Abstract: Demodulating a DPSK encoded data signal. The received signal has a symbol tracking value determined in a synchronization circuit. Doppler error in the signal is estimated. The signal, the symbol tracking value, and the estimated Doppler error are applied to a demodulator within which the signal is multiplied by a signal at a frequency which is the negative of the estimated Doppler error to remove that Doppler error. The resulting signal is filtered and decimated and normalized to generate the arctangent of the in-phase and quadrature components of the baseband signal. This arctangent signal is stripped of phase angle modulation and applied through loops to remove derivatives of the input phase signal. The arctangent and the resulting angles are mapped in a nearest neighbor map circuit, and the difference between successive angles is applied to a gray code to binary mapping circuit which detects the encoded data.

Abstract: A binary phase shift key demodulator (64) demodulates a signal conveying bits. A vector computation component (88) computes an I, Q vector associated with a reference bit and computes an I, Q vector associated with a subsequent bit. A vector comparison component (92) interprets the subsequent bit as a first binary value if the vector associated with the subsequent bit is within a first range of vector angles from the vector associated with the reference bit, and interprets the subsequent bit as a second binary value if the vector associated with the subsequent bit is outside of a second range of vector angles from the vector associated with the reference bit.

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: A simplified method for frequency offset estimation in a TDMA cellular PCS environment using &pgr;/4-shifted DQPSK comprises the steps of multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to produce a comparison vector having an angle equal to the phase angle between the received complex-valued symbol and the succeeding symbol, rotating the comparison vector so that the angle thereof is between 0° and 90°, and estimating the frequency offset by determining a constant deviation of the phase angle from an ideal phase angle value of 45° by calculating an average phase angle for a plurality of successive comparison vectors or correlating the rotated comparision vector against a bank of unit vectors to determine a maximum correlation.

Abstract: An encoding/decoding apparatus and method for an orientation interpolator node are provided. The encoding/decoding apparatus for an orientation interpolator node, which provides rotational information of an object in a 3-dimensional space, is formed of “key information” which indicates a time when a rotational movement occurs and “key value information” which indicates a rotational posture corresponding to the time. A predictive coding apparatus is used in the encoding process for compressing the information of the key and key value information. Therefore, in encoding an input orientation interpolator node in an information compression method of a predictive encoding method, the efficiency of encoding is improved and an reverse rotation due to an encoding error from lossy coding can be corrected.

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 system for and method of modulating and demodulating a communication signal using differential quadrature phase shift keying (DQPSK) can include, upon receiving an inbound communication signal, demodulating the inbound communication signal by obtaining Pi/4 differential quadrature phase shift keying (DQPSK) symbols, translating the Pi/4 DQPSK symbols into quadrature phase shift keying (QPSK) symbols, and mapping the QPSK symbols to a pair of bits. Upon initiating an outbound communication signal, the system and method can include modulating the outbound communication signal by obtaining communication bits indicative of the outbound communication signal, translating the communication bits to three communication bits, and mapping the translated bits to DQPSK symbols.

Abstract: Methods and systems are provided which generate hard and soft values from signal samples of a differentially encoded signal by estimating channel coefficients associated with the received signal and determining metrics for each possible symbol pair which indicate the probability of a possible coherent symbol pair being encoded in the signal samples using the estimated channel coefficients and the signal samples. Soft values associated with differential bits or differential symbols encoded in the samples of the signal are then generated based on the determined metrics.

Abstract: Methods and systems for iterative demodulation of a message are provided. A first copy of the message is received to provide a first set of symbols associated with the message. A second copy of the message is received to provide a second set of symbols. The first copy is associated with a first interleaving pattern and the second copy is associated with a second interleaving pattern different from the first interleaving pattern. The first set of symbols and the second set of symbols are iteratively demodulated using extrinsic information associated with the first set of symbols for demodulation of the second set of symbols and extrinsic information associated with the second set of symbols for demodulation of the first set of symbols to provide a set of symbol estimates for the message. Transmit methods and systems for selective interleaving to generate the copies of the message in a retransmission based communication system are also provided.

Abstract: In accordance with the present invention, a duplex radio communication system comprises an Interrogator which generates a radio signal to at least one remote Tag. The remote Tag receives the radio signal. The Tag then generates a subcarrier signal, and using Quadrature Phase Shift Keying (QPSK), modulates an information signal onto the subcarrier. A Backscatter Modulator, using this modulated subcarrier, modulates the reflection of the radio signal, the reflected signal being a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal to obtain the information signal. In one embodiment, demodulation utilizes a homodyne detector. In another embodiment, the Interrogator modulates an information signal onto the radio signal, transmits that modulated radio signal to the Tag, and the Tag demodulates that modulated radio signal to recover the information signal.

Abstract: The present invention makes it possible to transmit data while reducing the influence of fading caused on a transmission path. When communication data is transmitted by using a plurality of subcarriers arranged with a predetermined bandwidth, a data block consisting of a plurality of subcarriers arranged in rows in a time axis direction is used as a data unit. By implementing both a differential modulation process based on each phase difference in the frequency axis direction between a plurality of subcarriers and a differential modulation process based on each phase difference in the time axis direction between a plurality of subcarriers, a transmission signal with symbol data superposed on each phase difference between a plurality of subcarriers is generated and output.

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 system and method for demodulating slots having a mixed slot formation including differential and coherently encoded slots is disclosed. The method includes pre-phase encoding data and a predetermined sequence in a slot at a transmitter such that the encoded data and the predetermined sequence have equal reference phases from a reference symbol of a previous slot having a reference phase. Another method includes pre-phase encoding the predetermined sequence with a phase determined from a reference symbol from the previous slot at the transmitter. Yet another method includes differentially phase encoding the predetermined sequence according to IS-136A standards using a reference phase of π 4 . In another method pre-phase encoding data includes phase shifting data using one of a group of different phase angles, each of the different phase angles an integer multiple of π 2 .

Abstract: A system is disclosed for providing communication across a wireless network. The system includes a transmitter transmitting a modulated signal across a radio channel, wherein the transmitter includes first input means for receiving a primary data signal to be transmitted, second input means for receiving a secondary data signal to be transmitted, a combiner associated with the first and second input means for combining the primary and secondary data signals, and a modulator receiving the combined primary and secondary data signals from the combiner and sequentially developing a modulated signal including a string of phase values with each phase value containing information relative to both the primary and secondary data signals. The system also includes a receiver for receiving the modulated signal, wherein the receiver includes means for separating the received modulated signal into primary and secondary phase values representative of the primary and secondary data signals.

Abstract: According to the present invention a method and a receiver for high-frequency signals is provided. The receiver comprises a power divider (4) to divide a modulated RF input signal in at least two branches. At least one delay line (5, 6) provides for a delay of the branches relatively to each other by a predetermined delay constant. A calculation circuit (7, 8) calculates at least three power levels based on combinations (12, 13, 14) of the two branches of the input signal relatively delayed (5, 6) to each other. A processing means (10) calculates the phase and the amplitude of a complex signal representing the relation between the two branches of the input signal relatively delayed to each other, on the basis of the said at least three power levels (8). The invention therefore provides for a direct 6-port receiver based on non-coherent detection. The concept of the invention is inherently cheap and features high integration ability and low-cost processes.

Abstract: Dibits (i.e., pairs of bits) in an input data stream are converted into a modulation signal (e.g., a &pgr;/4-DQPSK modulation signal) using a technique that relies on pre-computed filter output values to reduce the processing required to generate each sample in the modulation signal. The pre-computed filter output values are stored in one or more look-up tables, which are accessed in real time during signal conversion to retrieve values as needed. In one implementation, the dibits, which are represented by complex values in a complex symbol space, are converted into two streams of state variables: one stream for the even symbols and one stream for the odd symbols. In addition, a third stream of state variables identifies whether each of the corresponding symbols is an even symbol or an odd symbol. The three streams of state variables are used to generate address pointers that are used to access the pre-computed filter output values from the look-up tables.

Abstract: A system and a method for transmitting coded information bits using multitone techniques on a frame-by-frame basis. For transmission, coded information bits are mapped into differential phase signals and absolute phase signals are generated based on differential phase signals. N complex symbols are then generated and inverse discrete Fourier transformed into N complex, time-domain samples, which are augmented with a cyclic prefix and suffix. The augmented N complex, time-domain samples are then separated into two real samples and converted into first and second baseband signals. The first and second baseband signals are impressed into quadrature carrier components to form in-phase and quadrature signal components which are combined into an RF signal prior to transmission. For reception, a received RF signal is non-coherently quadrature demodulated into first and second quadrature baseband signals.

Abstract: A method for increasing data rates within a modulated signal is disclosed. Initially, a first and second bit streams are interleaved together to form an interleaved output bit stream. The interleaved output bit stream is modulated in a manner such that upon demodulation of the interleaved output bit stream according to an FSK modulation scheme only the first bit stream is recovered, and upon demodulation of the interleaved output bit stream according to a second modulation scheme, both the first and second bit streams are recovered.

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: Various modem designs are described, along with systems that use the modem designs for communicating data between a large number of remote locations and one or more central locations preferably over CATV. One aspect features a modem having a transmitter which uses a state machine and digital waveform signals stored in a memory to create a modulated signal. Another aspect features a modem having a receiver which uses a digital correlator including an SRAM for detecting a bipolar phase shift keyed signal. Still another aspect features a modem comprising an oscillator circuit having a feedback loop, wherein the feedback loop utilizes a downlink signal, and a protection circuit which prevents a malfunction in the modem from causing system-wide shutdown.

Abstract: A method and apparatus for demodulating includes differential-detecting an input signal into which a unique word is inserted, correlating an output of the differential-detection and a data table obtained by differential-detecting the unique word, detecting a time when an electric power of a correlation output which exceeds a threshold value becomes the local maximum, reading the input signal stored in a buffer from the leading end of the unique word, estimating a frequency error of the input signal based on a phase of the correlation output, obtaining a signal by removing the frequency error from the read signal and inverse-modulating a unique word portion in the signal in which the frequency error has been removed, according to a data of a unique word table, and then reproducing a carrier signal.

Abstract: A transmitter and a receiver of a spread spectrum communication system for compensating carrier frequency offsets between the transmitter and the receiver. The transmitter includes: a first multiplier for multiplying a pseudo noise signal and input data intended for transmission; a differential encoder for differentially encoding a signal outputted from the first multiplier; a modulator for modulating a signal outputted from the differential encoder; a second multiplier for multiplying the signal modulated by the modulator and a transmitting carrier and for outputting a spread spectrum signal; and an antenna for propagating the spread spectrum signal in the air.

Abstract: In a radio communication system (100), enhanced communication capability is provided while maintaining standard channel modulation compatibility. At a transmitter (110, 200, 600), a first information signal is generated from data according to a predefined standard modulation scheme (212, 613). A second information signal is generated from data that provides supplemental information to the standard modulated data (213, 616). For transmission, the first and second information signals are combined into a composite signal (214, 619) that represents the first information signal when interpreted according to the predefined standard modulation scheme.

Abstract: A digital communication system having a transmitter and a receiver. The receiver transmits a radio-frequency (RF) signal that is continuous phase modulated by digital data. The receiver having a converter, a differential detector, and a sequential decoder. The receiver receives the RF signal. The RF signal is converted into a baseband signal by the converter. The baseband signal is received by the differential detector wherein the continuous phase modulation of the baseband signal is detected. The detected signal is received and the digital data is decoded by the sequential decoder. The sequential decoder has a Viterbi decoder to compensate for intersymbol interference caused by the differential detector. The Viterbi decoder performs reduced Viterbi decoding utilizing a feedback loop (FB) for reducing computing inaccuracies due to the reduction of the number of trellis states.

Abstract: The invention relates to the organization of phase references in a data transfer system based upon the multiplexing of orthogonal frequency components, when transmissions in the system are composed of relatively short symbol sequences. In accordance with the invention, in the first symbol (OS1) of the sequence differential phase-shift keying between elementary signals is carried out, based upon a phase reference (Ref) transmitted in one or several subfrequency bands (fc) and upon a phase shift chain propagated one subfrequency thereof at a time. In each subfrequency band in the subsequent symbols of the sequence phase-shift modulation refers to the elementary signal of the preceding symbol of the same subfrequency band. The invention may be applied with benefit to digital cellular network systems which employ the OFDM method.

Abstract: For decoding a diphase-coded signal the signal level is sampled with a sample signal of frequency equal to that of the bit clock pulse and each sample value is logically linked to the preceding sample value in accordance with an XOR function. This is preferably done by means of a microcontroller using interrupt routines for the sampling. The method is particularly advantageously applicable to transponder systems, for example contactless identification systems, the coding signal being modulated by the transponder onto a carrier signal; both the bit clock pulse and the sample signal of equal frequency thereto can be obtained by frequency division of the carrier signal.

Abstract: A modulation and demodulation method for communication between a transmitting side and a receiving side includes a step of at the transmitting side, producing a modulating signal, an amplitude ratio of a current instantaneous amplitude of the modulating signal and an instantaneous amplitude at n symbols previously in time (n is a natural number) of the modulating signal being set to correspond to a code to be transmitted, a step of at the transmitting side, modulating a carrier with a radio frequency or an intermediate frequency by the modulating signal to provide and transmit a modulated signal, a step of at the receiving side, receiving the transmitted modulated signal to provide a received signal, and a step of at the receiving side, deciding the transmitted code from an amplitude ratio of an instantaneous amplitude of a signal point in a signal space and an instantaneous amplitude of the signal point in the signal space n symbols previously in time with respect to the received signal.

Abstract: A reduced complexity maximum likelihood multiple symbol differential detector which utilizes a maximum likelihood sequence estimation of the transmitted phase and does so by expanding the observation window to observe the received symbol over N signal intervals and making a simultaneous decision on N-1 symbols. The phase of the received signal is calculated up front and thus the detector requires only real subtractions and real additions as opposed to complex multiplications and additions. Furthermore, the detector does not sacrifice performance over conventional prior art detectors.

Abstract: A data transmission system in which an on/off keyed (OOK) AM/DPSK modulated data signal with an on/off ratio exceeding about 80 dB which has been modulated on a carrier is received at a compact, easily fabricated and battery powered data receiver which operates without automatic gain control and which includes a double loop antenna (diameter of about two inches) with a trimmer capacitor center tapped to the antenna for providing a conjugate impedance match between the antenna and a low noise amplifier. In the receiver, a square-law detection AM demodulator for demodulating the amplified signal is in a bipolar silicon IC, and a DPSK data detector for decoding the demodulated signal is in a separate digital CMOS IC.

Abstract: The invention relates to an 8-PSK differential coder for trellis-coded modulation and to a corresponding pragmatic decoder, enabling 90.degree., 180.degree., and 270.degree. phase ambiguities to be lifted. The invention applies in particular to transmitting images at high rate by radio link.

Abstract: A method and apparatus for phase encoding and decoding a CPM spread spectrum signal. A transmitter divides a data stream into a data symbol portion and an associated phase information portion. The data symbol portion is used to select one of a plurality of spread spectrum codes for transmission from a symbol table. The phase information portion is used to differentially phase encode the data symbol prior to transmission. The transmitter divides the phase encoded spread spectrum codes into a plurality of data streams (such as I and Q data streams), independently modulates the I and Q data streams using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and simultaneously attempts to correlate for a plurality of chip sequences (such as I and Q chip sequences), and derives a real correlation signal and an imaginary correlation signal.

Abstract: A system for the wireless transmission of multiple information signals utilizing digital time division circuits between a base station and a plurality of subscriber stations. The subscriber stations may be fixed or movable. The number of time division circuits is determined by the transmission quality of the signals. The base station is interconnected with an external information network, which may be analog and/or digital. The information signals are selected from the group consisting of voice, data, facsimile, video, computer and instrumentation signals. The modulation level of the signals and the power applied to the system are adjusted in accordance with signal error detection in the system. The system is provided with spatial diversity by using a plurality of antennas selectively spaced from each other to provide relatively high signal reception despite signal fading. The base station operates over a plurality of RF channel pairs.

Abstract: A binary phase shift keyed (BPSK) modulator (200) used for digital phase modulation is shown. Phase shift is achieved by electrically switching an RF input signal (201) through either a direct signal path (203) or through a half wave transmission signal path (205) to shift its phase by 180 degrees. Both the data signal (211) and its complement (213) are used to turn on one of PIN diodes (207, 209) while simultaneously turning off the other diode with reverse bias. This technique allows for obtaining maximum diode isolation. The BPSK modulator (200) has the advantages of very low insertion loss, dc coupling for low frequency modulation components and high performance with minimum parts.

Abstract: An integrated circuit chip set is provided for use in a radio communication system in which a modulated digital input signal is processed for transmission and a modulated signal received from an antenna is processed to provide an output signal, wherein the modulation of the signals is either QPSK or FSK and the signal transmission and reception is by either TDD or FDD.

Abstract: A digital radio communication system employs an encoder for creating a set of encoded bits for each set of input bits. A mapper in the transmitter employs a modulation scheme which is constrained in the maximum phase angle difference between subsequently transmitted symbols. A constellation having a number of redundant symbols within the constrained maximum phase angle is chosen. An iterative search is performed to assign each of these symbols to a set of encoded bits such that the resultant coded scheme provides optimal bit error rate (BER) performance for the channel type. Configuring the encoder and mapper in this manner reduces the transmitted power envelope variation of the transmitted signal, thereby reducing the linearity requirements on a transmitter amplifier. Since transmitted power envelope variation is reduced, battery life of a mobile unit is extended.

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 low cost spread spectrum modulator for BPSK, or Binary Phase Shift Keying capable of outputting the high modulation rate and suppressed carrier output needed in spread spectrum systems. The present invention provides high quality BPSK modulation without the double balance mixers as required in the prior art, thereby dispensing with the necessity of complex transistor/potonciometer or diode/transformer arrangements. The present invention provides BPSK modulation utilizing only one transformer, which can be adjusted for carrier suppression and two transistors. FET's, or digital logic gates or the like, allowing the present system to be driven from low power CMOS logic levels, yet producing eight db of gain. The present invention may also be utilized as a frequency multiplier, with the utilization of the appropriately high frequency transistor, FET, digital logic gate, or the like.