| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-frequency power amplifier for obtaining a high efficiency over a wide range of output level and of achieving sufficient efficiency improvement even for an input level other than an adjustment point by injecting secondary harmonic with always optimum phase and amplitude in accordance with the input level of a fundamental wave because a conventional F class amplifier has such a problem that the effect of efficiency improvement by reflecting a high-order harmonic becomes less significant when the output level is low. Ž<P>SOLUTION: The power amplifier includes a harmonic generator 32 that generates a secondary harmonic in an input stage of an amplifier 3 including a harmonic reflecting circuit 16, a variable phase shifter 33 that adjusts the phase of the secondary harmonic generated, and a variable attenuator 34 that adjusts the amplitude of the secondary harmonic, wherein the secondary harmonic is injected into the fundamental wave signal and then the fundamental wave signal is input to the amplifier and at the same time, a detector that detects the input level of the fundamental wave input and a control circuit 10 that controls of a vector adjuster of the harmonic generator 32 in accordance with the input level detected are further included. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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