| 摘要 |
<P>PROBLEM TO BE SOLVED: To suitably control a power amplifier with respect to the variation of output power, in a digital modulator of a multiplex modulation system. <P>SOLUTION: A signal multiplexer 1 multiplexes digital signals inputted from outside or outputs an I- and Q-signals by mapping. A digital filter 2 limits a band for the I- and Q-signals. A D/A converter 3 converts the band-limited I- and Q-signals to analog signals. An orthogonal modulator 4 orthogonally modulates the analog signals to IF signals, and a frequency converter 5 converts the IF signals to RF signals. A power amplifier 6 amplifies the RF signals, to output them as transmission power to the outside. A vector calculator 7 calculates vector values from the I- and Q-signals inputted to a digital filter, and an FET bias controller 8 adjusts the bias condition of a power FET in the power amplifier according to the vector values to reduce the power consumption of the power FET. <P>COPYRIGHT: (C)2004,JPO |
