Design of a Bandpass Transversal Filter Employing a Novel Hybrid Waveguide-Printed Structure

This paper introduces a novel hybrid structure to implement a bandpass transversal filter based on the combination of two well known technologies. The structure combines for the first time the waveguide and the microstrip technologies for the design of transversal filters with maximum selectivity. By combining these technologies, very compact structures are obtained to implement the so called modified doublet. One of the resonators of the doublet is formed with the TM₁₁₁ mode of a waveguide cavity, while the second resonator is implemented using a standard printed line microstrip resonator. It is shown that all the parameters of the N + 2 coupling matrix can be controlled by means of the dimensions of the proposed structure. Results validate the novel structure, and show how a second order filtering function of a specific coupling matrix can be easily synthesized.