Controllable Attenuation Poles in the Coupled λ/4 Transmission-Line Filter

We propose here a new type of the coupled λ/4 transmission-line bandpass filter. This filter has sharp attenuation poles in both sides of its passband, which is easily produced by attaching metal fins on the input and output ports. The new features of this filter have been derived theoretically by the finite-element method and verified by experiments that we took.