| 摘要 |
PROBLEM TO BE SOLVED: To easily measure a noise component included in an output of an orthogonal modulator at a low cost and to suppress the noise component on the basis of a result of the measurement. SOLUTION: A noise of a carrier-field-through-component and a noise of an inverse side band component are in existence in a transmission signal that is processed for orthogonal modulation. A frequency conversion section 117 down-converts the transmission signal on the basis of a signal with a frequency corresponding to the frequency of the noise signal that is desirably measured, the down-converted signal passes through a band-pass filter 119 and a detection circuit 121 converts the output of the filter into an effective value of the signal corresponding to the noise component. Since the noise component is observed after being converted into a low frequency component, the measurement circuit is configured with a simple circuit and the measurement is also facilitated. The modulation correction circuit 130 controls an adjustment amount of the amplitude and the phase by a phase.amplitude adjustment sections 102, 103 and a bias voltage applied to a signal wave by DC bias variable circuits 104, 105.
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