In order to carry out high-precision control of distortion compensation, a received signal is split into two signals. One of the resulting signals ("the first signal") is provided to a distortion generator with similar characteristics to the distortion produced at the signal transmitting side, and the phase and amplitude of the other of the resulting signals ("the second signal") are controlled. By adding these two signals, the desired signal is suppressed and only the distortion component is extracted. This process is controlled by correlation detection of the desired signal. Next, the distortion component contained in the second signal is removed by controlling the phase and amplitude of this extracted distortion component and adding the result to the second signal. This process is controlled by detecting the correlation between the extracted distortion component and the error component contained in the signal after the addition. This enables compensation for distortion produced at the transmitting side to be performed at the receiving side, so that the size of transmitting equipment can be reduced.
A receiving circuit of a mobile communication terminal which can prevent the deterioration of receiving sensitivity caused by an intermodulation product signal. The receiving circuit includes a front-end receiver, a controller, and a feed forward linearizer having an intermodulation product generator, a phase shifter and a variable attenuator. The feed forward linearizer generates an internodulation product signal in a feed forward path having the same magnitude as an intermodulation product signal in a main path, generated from the front-end receiver, but with a 180.degree. phase difference. As a result, the intermodulation product signals are eliminated via vectorial addition of the signals in the main and feed forward paths.
Radio base stations subject each code-division multiplex signal to frequency conversion so as to vary each frequency thereof according to the radio base stations and then converts the signal to an optical signal before transmitting the same to a switching station. The switching station multiplexes the optical signals, subjects a signal obtained after multiplexing to optical-electrical conversion, and extracts the code-division multiplex signal from the respective electrical signal obtained after the conversion. Consequently, each signal to be demodulated by demodulating sections includes nothing but the code-division multiplex signal outputted from the radio base stations. Therefore, a code-division multiplex signal outputted from a desired base station is not disturbed by code-division multiplex signals outputted from the other stations as a noise as will be in a conventional system.
A method and apparatus for attenuating a transmit signal spectrum in a receiver bandwidth. The apparatus relates to an adaptive, digital, coherent, spectral canceller. The method comprises digitizing both a corrupted receiver signal and a reference transmit signal and then digitally implementing an adaptive coherent spectral canceller module to suppress a residue transmit spectral signal power within the receiver bandwidth.
To obtain a uniform improving effect of secondary distortion over a wide frequency band with a very simple configuration and less power consumption in the distortion compensation circuit, that improves the secondary distortion circuit of an optical transmitter and a high-frequency amplifier used for a transmission line processing a high-frequency signal over a wide frequency band, such as a cable television(CATV). A fundamental passing path for passing a fundamental wave is configured by connecting an attenuation component 102 for attenuating a signal, comprising a combination of resistors in series with a delay line 103, and a distortion adding path to add distortion is configured by connecting a 1st attenuation component 104 for attenuating a signal comprising a resistor, a 1st diode 105 and a 2nd diode 106 for generating distortion in series and connecting a 2nd delay element 107 and a 2nd attenuation element 108 for setting a signal level and comprising a resistor is series between a connecting point Q of the 1st diode 105 and the 2nd diode 106 and an output terminal 109.
At the output of a line driver (1) connected to a long transmission line, signals received on the transmission line are only a fraction of signals transmitted by the line driver on the transmission line. To minimize the transmitted signal with its distortion and noise in the receive path of the line driver, an additional driver (4) having the same voltages and currents in the signal path, is added. The additional driver (4) drives an additional load (Z2). The signal transmitted to the transmission line together with its superimposed received signal, is subtracted from the signal from the additional driver (4), which is not superimposed on any received signal. The resulting signal is reduced from transmitted signal, transmitted distortion and transmitted noise. To minimize die size and power consumption, the additional driver (4) is scaled, but the distortion remains unchanged compared to the "normal" line driver.
