Abstract: A non-linear distortion signal contained in output signal components from a high-frequency power amplifier is detected, while a non-linear distortion signal is generated from a high-frequency signal to be amplified. Correlation between this non-linear distortion signal and the detected non-linear distortion signal is determined, and a control variable is calculated based on the signal thus obtained. The obtained control variable is multiplied by the generated non-linear distortion signal to generate a distortion compensation signal, which is added to the signal to be amplified. This provides a distortion compensation device capable of automatically maintaining optimum distortion compensation characteristics and rapidly achieving desirable distortion compensation.

Abstract: The invention aims to converge predistortion coefficients efficiently in a predistorter adapted to compensate for distortion generated in an amplifier. Level detection means detects the level of a signal input to an amplifier. Signal acquisition means acquire a signal output from the amplifier as a feedback signal. Correspondence acquisition means updates a predistortion coefficient expressed using a set of orthogonal polynomials so that a distortion component contained in the acquired feedback signal is reduced and acquires a correspondence between the level of the signal input to the amplifier and a control coefficient for predistortion (contents of a distortion compensation table). Predistortion executing means applies distortion for predistortion with respect to the signal input to the amplifier in accordance with the control coefficient for predistortion that corresponds to the detected level based on the acquired correspondence.

Abstract: A non-linear distortion signal contained in output signal components from a high-frequency power amplifier is detected, while a non-linear distortion signal is generated from a high-frequency signal to be amplified. Correlation between this non-linear distortion signal and the detected non-linear distortion signal is determined, and a control variable is calculated based on the signal thus obtained. The obtained control variable is multiplied by the generated non-linear distortion signal to generate a distortion compensation signal, which is added to the signal to be amplified. This provides a distortion compensation device capable of automatically maintaining optimum distortion compensation characteristics and rapidly achieving desirable distortion compensation.

Abstract: In accordance with the present application, it is possible to determine whether or not it is appropriate to apply SDMA by estimating the fading speed of mobile stations. A wireless communication apparatus of the present application includes: a fading speed estimation portion (30) which detects phase variations of weighting coefficients of an adaptable array antenna and estimates the fading speed of the mobile stations based on the phase variations of the weighting coefficients; and a communication control portion (12) which conducts control operations so as to assign channels for SDMA based on the estimated results.

Abstract: The invention aims to converge predistortion coefficients efficiently in a predistorter adapted to compensate for distortion generated in an amplifier. Level detection means (11) detects the level of a signal input to an amplifier (4). Signal acquisition means (5-7) acquire a signal output from the amplifier as a feedback signal. Correspondence acquisition means (14) updates a predistortion coefficient expressed using a set of orthogonal polynomials so that a distortion component contained in the acquired feedback signal is reduced and acquires a correspondence between the level of the signal input to the amplifier and a control coefficient for predistortion (contents of a distortion compensation table (12)). Predistortion executing means (13) applies distortion for predistortion with respect to the signal input to the amplifier in accordance with the control coefficient for predistortion that corresponds to the detected level based on the acquired correspondence.

Abstract: A transmitter, that effectively suppresses a peak level of transmit signals, equipped with a peak reduction signal generating means that generates a peak reduction signal. A level of the peak reduction signal is based on a transmit signal level threshold for determining a peak of the transmit signal, and is based on a transmit signal peak level. Further, a phase of the peak reduction signal is based on the phase of the transmit signal. The transmitter is also equipped with a peak reduction signal processing means that subjects the peak reduction signal to band restriction and orthogonal modulation, and is equipped with a transmit signal level suppressing means that subtracts the peak reduction signal subjected to band restriction and orthogonal modulation from the transmit signal.

Abstract: A memory effect distortion component compensating unit compensates for a distortion component caused by a memory effect of an amplifier by using a time difference of results from raising an input signal to even power.

Abstract: A memory effect distortion component compensating unit compensates for a distortion component caused by the memory effect of the amplifier by using a time difference of results from raising an input signal to even power.

Abstract: A transmitter that effectively suppresses the peak level of transmit signals is equipped with peak reduction signal generating means that generates a peak reduction signal having a level based on a transmit signal level threshold for determining a peak of the transmit signal and on a transmit signal peak level and having a phase based on the phase of the transmit signal, peak reduction signal processing means that subjects the peak reduction signal to band restriction and orthogonal modulation, and transmit signal level suppressing means that subtracts the peak reduction signal subjected to band restriction and orthogonal modulation from the transmit signal.

Abstract: A nonlinear distortion compensating power amplifier is provided with a gain adjustment circuit and performs gain adjustment control so that the overall gain of the entire system including a power amplifier is always maintained at a constant value. While this gain adjustment is being performed, a control circuit determines an optimum distortion amount pattern corresponding to instantaneous values of an input signal supplied to a distortion signal generation circuit to enable this circuit to generate a distortion signal such that the power of unnecessary out-of-band signal components in an output signal from the power amplifier is minimized.

Abstract: A nonlinear distortion compensating power amplifier is provided with a gain adjustment circuit and performs gain adjustment control so that the overall gain of the entire system including a power amplifier is always maintained at a constant value. While this gain adjustment is being performed, a control circuit determines an optimum distortion amount pattern corresponding to instantaneous values of an input signal supplied to a distortion signal generation circuit to enable this circuit to generate a distortion signal such that the power of unnecessary out-of-band signal components in an output signal from the power amplifier is minimized.

Abstract: An FM radio receiver, particularly for mobile receivers, reduces the effects of multipath distortion. It selects either an adaptive process (constant modulus algorithm or CMA) or a antenna diversity process depending on the circumstances of the instantaneous reception. The receiver reduces both the decline of the level of received signals with the diversity process and waveform distortion with the CMA process.

Abstract: A multi-level band-restricted waveform generator in which a modulation wave prior to band restriction (M-level signal sequence) is broken into elementary waveforms and a plurality (N-nary) of prestored waveform components corresponding to the elementary waveforms after predetermined band restrictions are read out of a read-only memory for generating waveform components and added to generate a desired multi-level band-restricted waveform.

Abstract: In order to attain a frequency spectrum efficiency by narrowing channel interval without inducing interference from adjacent channels, a signal level of a mobile unit which requests channel access is detected at a land site. The signal level thus detected is used to assign a channel to the incoming mobile unit such that the assigned channel is adjacent to a channel whose signal level is closest to the signal level of the assigned channel. Further, in order to meet magnitude changes of received signals, the magnitudes are checked so as to reassign currently allocated channels.

Abstract: In an antenna-selection diversity transmission and reception equipment which is in digital communication with a transmission and reception equipment having a single antenna, and performs transmission and reception with time division by using the same radio frequencies, the antenna-selection diversity transmission and reception equipment comprises a plurality of antennae, a receiving part having a receiving unit, comparing unit and selecting unit which are adapted for a receiving-antenna selection diversity, and a transmitting part having a memory unit for storing antenna information that was selected by the receiving part. An antenna for transmission is selected from the plurality of antennae at the time of transmission in accordance with the information of the memory unit.

Abstract: For use in a common service area of a plurality of radio base stations, each being preassigned with a radio channel and for transmitting a channel status signal indicative of whether the radio channel is idle or busy, a terminal station (14) comprises a monitoring circuit (37) for cyclically monitoring the channel status signals of the respective base stations to produce an internal signal when the radio channel is found idle for one of the base stations that has a highest priority for the terminal status. Responsive to the internal signal, a control circuit (29) inhibits the cyclic monitoring for other base station or stations. The priority is decided by a measuring circuit (27) for measuring field intensities of the respective channel status signals. When the base stations are three in number, operation of the monitoring circuit is inhibited for the channel status signal of a lowest-priority base station when both radio channels of two other base stations are idle.

Abstract: In order to achieve the spectrum economy and reduce the power consumption of a transmitter and reduce the error rate at a receiver and simplify receiver circuitry, at least one bit stream to be transmitted is quadrature modulated in a manner that the signal points do not define a trace on a complex amplitude plane which passes through the origin of the plane coordinates or in the vicinity thereof. The received signal is hard limited and frequency-discriminated to determine the instantaneous angular velocity of the received signal and is integrated to detect the phase variation between two consecutive received signals, and thereafter is decided with respect to the phase variation according to the decision threshold levels 0 and .+-..pi. radians.

Abstract: A receiver suitable for use at very high frequency bands in which an antenna output is filtered, amplified and then mixed with a local oscillator in a frequency convertor to provide an intermediate frequency. The intermediate frequency is provided to a quadrature detector which directly converts the intermediate frequency into two baseband signals whose phases differ by 90.degree.. The baseband signals are independently amplified and demodulated in a common demodulator which provides a single output signal.

Abstract: A frequency demodulator for a frequency shift keyed (FSK) signal which is modulated by two-level digital signals. The demodulator includes a logic circuit and a quadrature detector having a local oscillator frequency which is substantially equal to the center frequency of the received signal to produce a baseband signal in a quadrature phase relationship. The two-level digital signal is recovered as an output of the logic circuits depending upon whether the received FSK signal frequency is higher or lower than the local oscillator frequency. The demodulator solves the problems centered about a need for analog circuits which are undesirable, from an integrated circuit implementation standpoint. The demodulator avoids spike noise which deteriorates the error rate performance which is commonly found in the prior art (e.g. U.S. Pat. No. 4,521,892).

Abstract: In order to effectively avoid cochannel interferences in a multi-station communications system utilizing a plurality of channels in common, the order of transmission channels to be used is determined utilizing a transmission priority assigned to each channel. The subject matter is characterized in that (a) the transmission priority of a selected channel is raised if the selected channel is not used at another station, and (b) is lowered if the selected channel is used at another station. This means that the past use records of the transmission channels are accumulated so that a good channel can be selected with high probability. In other words, a transmission channel with high priority is still ready to be used even if it was not selected in the preceding selection.