TRANSMISSION CIRCUIT AND COMMUNICATION DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a transmission circuit operating with high linearity and with low noise. SOLUTION: An AM variable fc filter 102 uses an AM cutoff frequency to remove a high frequency component from an amplitude signal. An amplifier 105 supplies a power amplifier 107 with a voltage which is a result of amplifying the amplitude signal output from the AM variable fc filter 102. A PM variable fc filter 103 uses a PM cutoff frequency to remove a high frequency component from a phase signal. A phase modulator 104 phase-modulates the phase signal output from the PM variable fc filter 103 to output a high-frequency phase-modulated signal. The power amplifier 107 amplifies the high-frequency phase-modulated signal by using the voltage supplied from the amplifier 105, and outputs a resultant signal as a transmission signal. The AM variable fc filter 102 and the PM variable fc filter 103 respectively control the AM cutoff frequency and the PM cutoff frequency such that the AM cutoff frequency and the PM cutoff frequency each have an opposite characteristic to that of an output power of the transmission signal. COPYRIGHT: (C)2009,JPO&INPIT