| 摘要 |
PURPOSE:To obtain more excellent frequency spectrum by coupling a resonator coupled with an input circuit also with a circuit of a grounding terminal. CONSTITUTION:A grounding circuit 7 is coupled electromagnetically with a resonator 5 through a coupling hole 52 at a position at a length l3 from a grounding terminal of a field effect transistor (FET) 1 and opened at a length l4 in the preceding direction. In selecting the electric length l3 as nearly 90 deg. at the resonance frequency f5 of the resonator and as l3=l4, the frequency locus of the impedance Zx(f) viewing the grounding circuit 7 including the resonator from the grounding terminal of the FET 1 is shown in the Smith chart at f=f5 or its vicinity. That is, a point (b) is almost unchanged to a change in a minute frequency from the frequency f5 and constant. On the other hand, a point (c) is susceptible to the effect of the sharp frequency selectivity of the resonator 5 connected to the tip of the circuit even to a minute change in a frequency from the frequency f5 and changed largely and then restores to the point (a). Thus, the input reflection coefficient GAMMAA has a sharp frequency selectivity.
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