| 摘要 |
<p>A variable frequency filter in which a variation in cut-off characteristics is suppressed when the frequency is varied. The filter comprises two parallel resonance circuits, a coupling inductor coupling them, and a multipath circuit. The parallel resonance circuit comprises, connected in parallel, a resonance inductor and a series circuit of a variable capacitance element and a resonance capacitor. The multipath circuit comprises a coupling capacitor, and a variable capacitance element inserted between the coupling capacitor and each parallel resonance circuit. Since a variation in cut-off characteristics is reversed between the parallel resonance circuit and the multipath circuit when the frequency is varied, variations in cut-off characteristics are canceled when frequencies are varied simultaneously at the two and thereby variations in cut-off characteristics can be reduced when frequencies are varied.</p> |
