| 摘要 |
In a quadrature modulator which receives a pair of carrier signals having phases perpendicular to one another, and I and Q signals, and which outputs a modulating signal, a quadrature error based on a phase difference between the pair of carrier signals is detected. In a state that the signal levels of the I and Q signals are each made to be zero, a pair of dc voltages for causing that the modulating signal outputted from the quadrature modulator is made to be a predetermined reference level, are each added to the I and Q signals. In a state that pairs of dc voltages are each changed and sequentially added to the I and Q signals, plural combinations of pairs of dc voltages for causing that a signal level of the modulating signal is made to be the predetermined reference level, are retrieved, and the quadrature error is calculated from simultaneous equations in which respective values of the retrieved plural combinations of pairs of dc voltages, the signal level of the modulating signal, and a quadrature error of the carrier signals are variables.
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