Abstract: A digital demodulation circuit amplifies a received signal of an intermediate frequency with a variable gain control amplifier so as to convert it into a baseband signal, which is separated into a common-mode component and an orthogonal component. A first gain control voltage is generated based on the common-mode component and the orthogonal component. Additionally, a temperature correction value is generated by smoothing a pulse-width modulation signal, having a pulse width corresponding to ambient temperature, and by adding a predetermined gain and an offset thereto. A second gain control voltage is generated by adding the temperature correction value to the first gain control voltage. The variable gain control amplifier amplifies a received signal with the second gain control voltage. Thus, it is possible to achieve a temperature compensation function and an automatic gain control function in the digital demodulation circuit with a simple circuit configuration.

Abstract: A first signal having a first polarization direction and a second signal having a second polarization direction crossing the first polarization direction are received. A phase of the second signal is controlled using a phase control signal. An interference compensation signal is generated by weighted combination on a time-series of a signal whose phase has been controlled. Weighting coefficients used for the weighted combination are set so that the interference compensation signal becomes a cross-polarization interference component of the first signal. A phase difference between the first signal and the second signal is estimated using the weighting coefficients. The phase control signal is generated using the estimated phase difference so that a phase of the first signal and the phase of the second signal become identical. The first signal is compensated for cross-polarization interference caused by the second signal using the interference compensation signal and the first signal.

Abstract: A digital demodulation circuit amplifies a received signal of an intermediate frequency with a variable gain control amplifier so as to convert it into a baseband signal, which is separated into a common-mode component and an orthogonal component. A first gain control voltage is generated based on the common-mode component and the orthogonal component. Additionally, a temperature correction value is generated by smoothing a pulse-width modulation signal, having a pulse width corresponding to ambient temperature, and by adding a predetermined gain and an offset thereto. A second gain control voltage is generated by adding the temperature correction value to the first gain control voltage. The variable gain control amplifier amplifies a received signal with the second gain control voltage. Thus, it is possible to achieve a temperature compensation function and an automatic gain control function in the digital demodulation circuit with a simple circuit configuration.

Abstract: Even when transmitters of both polarizations in an opposing station apparatus output different signals, cross-polarization interference is compensated for.

Abstract: A multilevel QAM demodulator includes a phase difference calculation unit calculating a phase difference signal based on the common phase signal and orthogonal signal after the phase rotation compensation, a phase shift amount calculation unit calculating a phase shift amount indicating a degree of a phase shift based on the common phase signal and orthogonal signal after the phase rotation compensation and phase noise compensation, and a correction unit correcting the phase difference signal based on the phase shift amount. A phase rotation is performed for the phase noise compensation based on the phase difference signal corrected by the correction unit.

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: A multilevel QAM demodulator includes a phase difference calculation unit calculating a phase difference signal based on the common phase signal and orthogonal signal after the phase rotation compensation, a phase shift amount calculation unit calculating a phase shift amount indicating a degree of a phase shift based on the common phase signal and orthogonal signal after the phase rotation compensation and phase noise compensation, and a correction unit correcting the phase difference signal based on the phase shift amount. A phase rotation is performed for the phase noise compensation based on the phase difference signal corrected by the correction unit.