Integrated Waveguide Filter Amplifier Using the Coupling Matrix Technique

This letter presents an integrated waveguide filter amplifier using all resonator-based filtering and matching structure. An N + 4 active coupling matrix is proposed for the first time to describe the coupling topology. High-Q waveguide resonators are featured in the design, achieving simultaneous filtering and matching at both the input and output ports. Easy integration of the transistor with waveguide resonators is demonstrated through filter synthesis, where a hybrid waveguide/microstrip structure is implemented for the structural and impedance transition. In this letter, an X-band device is constructed as a demonstrator, but the technique is also applicable to higher frequencies where waveguide is widely utilized for its low loss.