PURPOSE: To adjust a local signal so as to minimize its leakage by controlling a DC bias automatically with a controller at calibration. ;CONSTITUTION: Two signals inputted via a serial parallel converter 1, digital filters 2a, 2b and switches 19a, 19b are added to two outputs from a DC bias circuit 18 at adders 20a, 20b respectively and the result is given to D/A converters 3a, 3b, from which analog signals are obtained. Furthermore, an orthogonal modulation signal extracted by a branching filter 13 is given to a band pass filter 14, in which the signal is subject to band limit and a signal detected by a power detector 15 is converted into a digital signal at an A/D converter 16, a controller 17 generates a DC bias control signal by the digital signal and a switch control signal is generated therefrom. Then each control signal controls respectively the DC bias circuit 18 and the switches 19a, 19b. That is, the output of the DC bias circuit 18 is adjusted by minimizing the leakage of a local signal.;COPYRIGHT: (C)1993,JPO&Japio
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