Strip-line filter, duplexer, filter device, communication device, and method of adjusting characteristic of strip-line filter

摘要

Resonator electrodes are provided on the upper face of a dielectric substrate. The ratios (W1/L1) and (W3/L3) of the electrode widths W1 and W3 to the electrode lengths L1 and L3 of the resonator electrodes of the first and last stages are set at substantially 1.05<W/L<1.95. Lead-out electrodes are connected to the resonator electrodes of the first and last stages on the opposite sides of the center axis which is a straight-line axis passing through the center positions of the resonator electrodes of the first and last stages. Thereby, an attenuation pole is generated on the lower band side of the pass-band.