Abstract: In a digital wireless communication device having an error correction function, the circuit quality is quickly detected with maintained accuracy. The circuit quality to such an extent that a bit error rate (BER) is slightly degraded (10?10 to 10?12) is quickly detected with maintained accuracy by monitoring the circuit quality based on a C/N error pulse into which C/N information scaling a carrier-to-noise power ratio (C/N) of a received signal has been converted.

Abstract: In a digital wireless communication device having an error correction function, the circuit quality is quickly detected with maintained accuracy. The circuit quality to such an extent that a bit error rate (BER) is slightly degraded (10?10 to 10?12) is quickly detected with maintained accuracy by monitoring the circuit quality based on a C/N error pulse into which C/N information scaling a carrier-to-noise power ratio (C/N) of a received signal has been converted.

Abstract: Ideal nonlinear distortion compensation is realized by removing an imperfection of amplitude delay characteristic and an affection of inherent deviation that an amplifier has. A linear distortion compensation factor calculating part (18) estimates, based on quadrature demodulated signals (I?ch, Q?ch), the linear distortion characteristic occurring mainly due to imperfection of analog circuits, such as a quadrature modulator (13) and a high-power amplifier (14), and calculates and outputs a linear distortion compensation factor for compensating the linear distortion. A linear distortion compensating part (12) performs a pre-distortion (addition of a reverse characteristic of the linear distortion characteristic) by multiplying the baseband signals (Ich, Qch) by the data of the linear distortion compensation factor.

Abstract: Ideal nonlinear distortion compensation is realized by removing an imperfection of amplitude delay characteristic and an affection of inherent deviation that an amplifier has. A linear distortion compensation factor calculating part (18) estimates, based on quadrature demodulated signals (I? ch, Q? ch), the linear distortion characteristic occurring mainly due to imperfection of analog circuits, such as a quadrature modulator (13) and a high-power amplifier (14), and calculates and outputs a linear distortion compensation factor for compensating the linear distortion. A linear distortion compensating part (12) performs a pre-distortion (addition of a reverse characteristic of the linear distortion characteristic) by multiplying the baseband signals (Ich, Qch) by the data of the linear distortion compensation factor.

Abstract: In a communication system having a base station (1) and terminal stations (5-1 to 5-M) in two-way communication, frequency converters (12-1 to 12-N) transmit transmitting signals. The terminal stations transmit channel selection signals to the base station. A level controller 15 discriminates, in response to the channel selection signals from the terminal stations, each of the channels that is selected by the terminal stations and produces and supplies a level control signal to the respective frequency converters. The selected frequency converter increases a level of the transmitting signal that corresponds to the channel which is selected by a terminal station.

Abstract: In a cellular radio communication system, a downlink signal is multicast from a cental station and multiple base stations receive the multicast downlink signal via transmission links and respectively transmit the downlink signal on radio waves of same frequencies so that a cluster of adjoining areas is illuminated with the radio waves. A mobile station having a tapped-delay line equalizer receives signals from the base stations via multipath fading channels and equalizes the received signals. Interference between the transmitted signals is avoided by adjusting the relative propagation delay times of the transmission links so that the signals received by the mobile station occur within the tapped-delay line length of the equalizer.

Abstract: An interference compensator for compensating interference waves with long delay times generated during digital microwave communications system-based relaying of waves at a single frequency. The compensator receives a demodulated digital signal, passes the signal through shift registers with different delay times, and then, through a forward equalizer, a first backward equalizer, a second backward equalizer and a center equalizer. All equalizers are transversal type equalizers, outputs from which are added as an output. In addition, the compensator is equipped with a delay time control circuit which monitors the tap coefficients of the forward equalizer, the backward equalizers and the center equalizer and controls the delay times of the shift registers so that the tap coefficients become greatest at the center delay circuits of the respective transversal type filters.

Abstract: A decision-feedback type equalizer comprising a forward equalizer for receiving digital pre-equalization signals and error signals as input signals, for reducing intersymbol interference caused by the lead echo of the pre-equalization signals, and for outputting forward equalization signals; a backward equalizer for reducing intersymbol interference caused by the delay echo of input signals, and for producing output in the form of backward equalization signals; an adder for adding forward equalization signals and backward equalization signals, and for outputting equalization signals; a decision device for comparing the equalization signals with reference values, and for outputting decision signals; a subtracter for subtracting the equalization signals and decision signals, and for producing and outputting error signals which are differences; an alarm emitter for detecting, from the signal states of the error signals, whether an abnormal state exists, and for emitting an alarm when an abnormal state is detecte

Abstract: A digital radio communication system includes a first demodulator, a second demodulator, a non-break switch, and a switching controller. The first demodulator receives a signal from a first antenna and outputs demodulated data and a line quality degradation signal. The second demodulator receives a signal from a second antenna and outputs demodulated data and a line quality degradation signal. The non-break switch receives the demodulated data output from the first and second demodulators and selects and outputs one of the demodulated data. The switching controller receives line quality degradation signals output from the first and second demodulators to output a switching control signal to the non-break switch on the basis of the received line quality degradation signals. The first and second demodulators output the line quality degradation signals before the demodulated data are set in an interrupt state when abrupt frequency selective fading occurs.

Abstract: On receiving a symbol sequence carried by a first-polarization and a second-polarization signal of two orthogonally polarized signals and in order to cancel a cross polarization interference (XPI) component which leaks from the second-polarization signal into the first-polarization signal, a first decision feedback XPI canceller (43) is supplied with a before processed signal derived from the second-polarization signal and with a decided signal which is produced by a decision circuit (22) and which represents the symbol sequence carried by the second-polarization signal with an intersymbol interference component and another XPI component cancelled from the before processed signal. Another decision feedback XPI canceller (44) is similarly operable.

Abstract: In a decision-feedback equalizer for use in combination with a demodulator (13) to equalize a demodulated signal into an equalized signal through a transversal filter (15), the transversal filter filters the demodulated signal into a filtered signal in accordance with a plurality of controllable tap gains. The filtered signal is processed into the equalized signal on the basis of the binary level of the filtered signal. The controllable tap gains are produced dependent on the demodulated and the equalized signal and a plurality of parameters. A delivering circuit (38) delivers limiting values as the parameters to the transversal filter when the demodulator is put in a synchronization state. The delivering circuit delivers additional values as the parameters to the transversal filter when the demodulator is put out of the synchronization state.

Abstract: In a decision-feedback equalizer for use in combination with a demodulator (13) to equalize a demodulated signal into an equalized signal through first and second transversal filters (15, 16), the demodulated signal and an input signal are filtered by the first and the second transversal filters into the first and the second filtered signals in accordance with a plurality of main controllable tap gains and a plurality of subsidiary controllable tap gains, respectively. The input signal supplied to the second transversal filter is controlled or selected by a supplying circuit (42). Specifically, the supplying circuit (42) produces as the input signal a first local signal obtained from the demodulated signal when the demodulator is put in a synchronization state. The supplying circuit produces as the input signal a second local signal obtained from the equalized signal when the demodulator is put out of the synchronization state.

Abstract: In an adaptive equalizer (40) connected to a demodulator (14) to equalize a demodulated signal into an equalized signal in accordance with main and first through N-th controllable tap gains, where N represents a positive integer which is not less than one, the main and the first through the N-th controllable tap gains are produced dependent upon the demodulated and the equalized signals and are controlled by main and first through N-th parameters, respectively. A supplying circuit (42) supplies main and first through N-th values as the main and the first through the N-th parameters to the adaptive equalizer when the demodulator is put in a synchronization state. The supplying circuit supplies main and first through N-th additional values as the main and the first through the N-th parameters to the adaptive equalizer when the demodulator is put out of the synchronization state.