Abstract: A communication device (60) for simultaneously transmitting independent information (82) on multiple channels comprises a modulator (66) and at least two matched filters (68-70). Each matched filter has a unique predetermined characteristic that is a time-reversed, complex conjugate of a complex waveform shape (72) produced by the modulator (66) in response to a channel encoder previously supplying known codeword vectors (75) to the modulator (66). Therefore, a composite signal envelope (82) produced for transmission by the communication device (60) of FIG. 4 has a reduced peak-to-mean envelope power ratio (PMEPR), since relatively large excursions in complex waveform shapes subsequently generated by the modulator (66) are unmatched by the unique filter characteristics while relatively small excursion are matched and therefore enhanced.

Abstract: The system and method of the present invention facilitates the selection of a portion of an operating bandwidth and frequency of a digital microwave radio. The components include a transceiver mounted to a mounting plate having waveguide ports. The input and output of the receiver and transmitter portions of the transceiver module occur through the two waveguide ports of the plate. A diplexer inserted within the slot of an interface is externally mounted in relation to the mounting plate and to transceiver unit. The microwave energy from the transceiver module is coupled through the mounting plate, diplexer, interface and antenna. Because of the external mounting arrangement of the diplexer, interface, selecting an operating portion of the available bandwidth may occur after complete manufacture of the digital microwave radio.

Abstract: A communication system (10) implemented to be specifically matched to the time and spatially dependent statistics of a transmission channel (36). The communication system (10) is used for broadcasting over the channel (36) to users in a coverage region (18). The communication system (10) includes a transmitter (12) having an error correction encoder (30) and a weighted interleaver (32). The error correction encoder (30) includes a first input to receive data bits and a first output. The error correction encoder (30) expands each data bit received at said input by an encoder rate. The weighted interleaver (32) includes a second input to receive the expanded data bits and a second output. The weighted interleaver (32) has a non-uniform delay distribution between a minimum delay and a maximum delay to interleave the expanded data bits by the non-uniform delay distribution.

Abstract: Methods and apparatus for detecting and correcting phase and amplitude imbalances existing between I (in-phase) and Q (quadrature phase) signal components of a complex signal, e.g., QAM or OPSK signal, that is being demodulated are described. The phase and amplitude imbalance and correction circuitry of the present invention are implemented as decision directed control loops which can be used in conjunction with an overall decision directed gain control loop. Amplitude imbalance is corrected by adjusting the gain of one of the I and Q signal components. Phase imbalance is corrected by adding a portion of one of the I and Q signal components to the other one of the I and Q signal components. Overall amplitude control is achieved by adjusting the gain of both the I and Q signal components by the same amount.

Abstract: SIR measurement for measuring S/N ratio, which is the ratio of a desired signal power to noise power, or S/I ratio, which is the ratio of desired signal power to interference signal power, uses a signal-point position altering unit for taking absolute values of an I component (in-phase component) and Q component (quadrature component) of a received signal to convert the received signal to a signal in the first quadrant of an I-Q orthogonal coordinate system, and for squaring the average value of the converted signal to obtain first average power (desired power) S, a received-power arithmetic unit for calculating the average value of the square of the received signal to obtain second average power, and for subtracting the desired power S from the received power to obtain noise power or interference power I, and a SIR arithmetic unit for calculating S/N ratio or S/I ratio from the desired signal power S and noise power or interference signal power I, and for outputting the ratio calculated.

Abstract: Radio equipment for communicating digital data includes a clock modulation part for angular-modulation of a clock signal by a given modulation signal; and a data processing part processing the digital data based on the clock signal angular-modulated in the clock modulation part and producing angular-modulated digital data. In the radio equipment, levels of harmonics generated from the clock signal and the digital data are reducible.

Abstract: Amplitude and phase errors between branches I and Q of a transceiver utilizing phase quadrature modulation are corrected by preventing propagation of a nominal-frequency signal from a digital part through a loop part and a reception branch to an RSSI indicator by changing the frequency response of a component on the path of the signal. The same indicator that normally measures the payload signal, here measures only undesired signal components. After this, such amplitude and/or phase correction signals are determined with which the measuring result obtained from the indicator reaches the minimum. The resultant correction signals are stored in the memory, and the frequency response of the system is then restored to normal.

Abstract: A mobile telephone receiver, utilized in a cellular communications system, is provided with a group of IF bandpass filters which are arranged in parallel and which respectively have different passbands with each other. The IF filter group allows an incoming IF signal to be filtered out using one of the IF bandpass filters. A signal contamination determiner is operatively coupled to the IF filter group and detemines a degree of signal contamination by examining a signal which has passed through the IF. bandpass filter selected for filtering the incoming IF signal. The selector changes the selection of the IF bandpass filters according to the degree of signal contamination.

Abstract: Apparatus for transmitting and receiving digital information over mobile communication channels. The apparatus includes a pilot symbol insertion device for periodically inserting data dependent pilot symbols into frames of digital data for subsequent channel estimation, a continuous phase modulator for modulating and transmitting over a mobile communication channel the frames of digital data and means for receiving and filtering the transmitted data. A channel estimator estimates the channel amplitude and phase distortion from the received pilot signal at different time instants. Means are provided for demodulating the received signal and for decoding the demodulated signal to recover the estimated transmitted data.

Abstract: A method and apparatus for improved mobile radio telecommunications employs the transmission of a pilot reference signal within the coherence band of the modulated carrier wave. The receiver in this system uses instantaneous phase estimation techniques of the pilot and carrier received waveforms to provide immunity from phase distortion introduced by the channel.

Abstract: In a high-power transmitter, an input complex signal is multiplied in a complex multiplier by control signals. The output complex signal from the multiplier is converted to a high frequency signal and amplified by a power amplifier for transmission. The amplitude of the input complex signal is detected to access a memory where amplitude and phase correction values are stored. During a read mode of the memory, a set of amplitude and phase correction values is specified by the detected amplitude and supplied to the complex amplifier as the control signals. During a write mode of the memory, a set of amplitude and phase correction values is specified by a delayed version of the detected amplitude and rewritten with a set of new amplitude and phase correction values. The amplified high frequency signal is down-converted to a low frequency complex signal.

Abstract: A method and apparatus for producing amplified signals for communications having reduced adjacent channel energy involving generating a first signal having an undesired amount of adjacent channel energy, generating a second signal corresponding to the undesired amount of adjacent channel energy, and subtracting the second signal from the first signal to remove the undesired amount of adjacent channel energy. Several embodiments are disclosed.

Abstract: In a DC offset circuit for a Cartesian loop, a DSP supplies step by step a slope voltage from a minimum DC output voltage, up to a maximum DC output voltage, to input sections of operational amplifiers for modulation. This arises each time transmission is started in a state where a signal Q' and a signal I', each based on only a carrier wave, are outputted from a quadrature demodulator. When comparators detect that output from operational amplifiers is 0 V, the DSP decides a value of the slope voltage then as a DC offset voltage value. Operation is started centering on this DC offset voltage value.

Abstract: A carrier phase estimation apparatus include a base band converter and a phase estimator. A received IF signal is converted to an in-phase component In and an quadrature component Qn of a digital base band signal in the base band converter. In the phase estimator, a non-linear circuit executes a non-linear operation of the components In and Qn to output non-linearly converted in-phase component In' and quadrature component Qn' of the digital base band signal and the components In' and Qn' are input to a pair of filters. In each filter, the components In' or Qn' are stored into shift registers at a predetermined timing and the signals stored in the shift registers are multiplied by respective weighting factors C.sub.k in respective multipliers. The multiplied values are summed by an adder and the obtained sum is divided by a stage number N of the shift register in a divider to obtain filtering signals Xn and Yn.

Abstract: The amount of memory needed for a ROM-based .pi./4 DQPSK filter is reduced by using a mapper in an IQ modulator (inverse mapper in a demodulator) that incorporates a 90.degree. phase shift for every other symbol. During the intervening symbols no additional phase shift is incorporated by the mapper. This produces a coarse precession of 90.degree. for every other symbol. The 90.degree. of coarse precession may be produced by using alternate DQPSK mappers for alternate symbols. Both mappers share a common repertoire, so no new modulation state symbols are required. During the alternate 0.degree. symbols the filter inserts a 45.degree. phase shift, but does not insert such a 45.degree. phase shift during those intervening times when the mapper (or inverse mapper) is inserting a 90.degree. phase shift. This produces a fine precession. The result is to produce a uniform precession of 45.degree. between each modulation state symbol.

Abstract: The method is of the type featuring a parallel transmission, over a predetermined number of transmission frequencies at a low bit rate, of useful information signals modulated at a predetermined phase shift keying. A parallel transmission on all the frequencies of the frames of useful signals and of frames of reference signals is performed, a frame of reference signals being inserted between two neighboring useful frames, and each reference signals being alternated with a useful signal in each frame of the reference signals. Such a method finds particular application to the digital transmission of speech.

Abstract: An improved digital data modulator is provided for a digital transmitter. The digital data modulator comprises of a pair of digital data synthesizers which are controlled in a manner which produces complex conjugate modulated data signals of the input signals. Summing means are provided to sum the outputs of the digital data synthesizers in a manner which removes the imaginary components and simultaneously reduces the side load power without employing conventional filters.

Abstract: The present invention discloses a wireless LAN, a peer-to-peer wireless LAN, a wireless transceiver and a method of transmitting data, all of which are capable of operating at frequencies in excess of 10 GHz and in multipath transmission environments. This is achieved by a combination of techniques which enable adequate performance in the presence of multipath transmission paths where the reciprocal of the information bit rate of the transmission is short relative to the time delay differences between significant ones of the multipath transmission paths. In the LANs the mobile transceivers are each connected to, and powered by, a corresponding portable electronic device with computational ability.

Abstract: A maximum likelihood sequence estimation capable of reducing an amount of real time calculations involved and improving a high speed follow up characteristic. N-dimensional vectors corresponding to all possible transmission sequence candidates of a prescribed length, which are pre-calculated according to a prescribed definition, are stored in a memory. Then, an estimated received signal for each one of the branches at the present sampling time is obtained by calculating an inner product of one of the N-dimensional vectors stored in the memory corresponding to each transmission sequence candidate resulting from each one of the branches reaching to each state at the present sampling time with the N-dimensional received signal vector for the present sampling time obtained from at least N received signals for at least N previous sampling times. The maximum likelihood sequence can be estimated as a survivor path for each state at the present sampling time according to this estimated received signal as usual.

Abstract: A carrier leakage suppression circuit is disclosed which adaptively suppresses carrier leakage in a signal processing device which modulates a carrier signal with an in-phase baseband signal and a quadrature baseband signal to generate a radio frequency (RF) output signal. The carrier leakage suppression circuit operates by imparting a first signature to the in-phase baseband signal and a second signature to the quadrature baseband signal prior to modulation of the carrier signal. In-phase and quadrature carrier leakage components in the RF output signal are isolated and measured by respectively correlating the RF output signal with the first and second signatures. An in-phase offset and a quadrature offset are generated as a function of the measurement of the in-phase and quadrature carrier leakage components. The in-phase baseband signal is combined with the in-phase offset and the quadrature baseband signal is combined with the quadrature offset to thereby suppress carrier leakage.