Design and Realization of a Dual-Mode Circular Waveguide Filter for Digital Audio Broadcasting (DAB) Applications

DAB applications demand the realization of band-pass filters with very stringent characteristics. In this paper this requirements have been fulfilled by designing and realizing a four-pole elliptic transfer function by means of a Dual-Mode Circular Waveguide Filter (DMCWF). This design has been performed by adopting a conventional synthesis strategy. The most critical aspect of this structure, that is its difficult tunability, has been overcome by experimentally adjusting the filter dimensions following a CAD procedure extensively described in the paper.