| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter circuit with an improved frequency characteristic in a damping ratio and a group delay amount. SOLUTION: An amplitude phase comparator 110 performs comparison between an input comparison signal and an output comparison signal which are respectively extracted from an input signal and an output signal by directional couplers 102 and 108, and outputs a phase difference signal 113 and an amplitude ratio signal 114 which are voltage signals respectively in proportion to the phase difference and the amplitude ratio of the output signal with respect to the input signal. The both signals are negatively fed-back to variable phase equipment 103 and a variable attenuator 104 to be controlled by voltage. The variable phase equipment 103 and the variable attenuator 104 adjust the phase and the amplitude of the input signal, so as to allow the phase difference and the amplitude ratio between the input signal and the output signal to be respectively kept in a prescribed value. Thus, analogicus property in a signal waveform is enhanced between the input and output signals, and a distortion is reduced in the output signal. Then uniformity is enhanced in the damping ratio and the group delay amount in the whole passage band of the wave filter circuit 100. COPYRIGHT: (C)2003,JPO
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