| 摘要 |
PURPOSE:To easily adjust the attenuation pole by using a sub-propagation line returning a signal from an optional resonator of a band-pass filter comprising plural resonators and a main coupling circuit to other resonator through a sub-coupling circuit via a lumped constant filter. CONSTITUTION:A band-pass filter BPF consists of the plural resonators 1 and the main coupling circuit 2, the phase of a signal extracted by the sub-coupling circuit 3 from one end point A of an optional resonator 1 is rotated by the phase characteristic of the lumped constant filter 6 and returned to one end point B of the other resonator of the BPF by the other sub-coupling circuit 5. Then the change in the phase of signal propagated through the lumped constant filter 6 is selected to be phiS=phiM+ or -180 deg., where phiM is a phase change of the main propagation by the BPF from the point A to the point B. That is, the lumped constant filter 6 is used as the phase shift function element of the sub-propagation path. Then a high frequency (polar) filter with ease of adjustment is obtained.
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