| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce output noise and suppress deterioration of reception sensitivity. Ž<P>SOLUTION: An amplitude controller 120 has: a DA converter 121 which converts amplitude data into a differential amplitude signal and outputs the signal; a level controller 122 that controls the level of the differential amplitude signal corresponding to transmission power information P; and an offset operator 123 which applies a DC voltage corresponding to the transmission power information P to the differential amplitude signal whose level has been controlled by the level controller 122. Compared with the case of using a DA converter, which has the same number of bits, does not perform conversion to differential amplitude signal, and performs only D/A conversion, the dynamic range of the DA converter 121 can be doubled, and by such amount, the gain of a differential single converter 124 at the latter stage of the DA converter 121 can be reduced. Thus, amplification of noise due to the differential single converter 124 is eliminated, and output noise of the amplitude controller 120 can be reduced. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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