Tunable compact microwave multiplexers based on substrate integrated waveguide
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Microwave multiplexers and diplexers are widely used in communication systems. This thesis presents a compact low-profile hybrid-coupled filter module (HCFM) implemented using substrate integrated waveguide (SIW). Compared to conventional rectangular waveguide HCFM, the new design achieves 60% reduction in size. The feasibility of electronic tuning of the HCFM is also investigated using full wave electromagnetic (EM) simulations. The compact SIW HCFM is further validated using measurement results. Good agreement between simulation and measurement results is achieved. In addition, a new method is proposed for implementing tunable diplexers. The tunable diplexer is formed by cascading a bandpass filter with the HCFM, thereby simplifying the tuning complexity of diplexers. Particularly, the bandwidths and center frequencies of the diplexer can be modified by simply tuning the center frequencies of the bandpass filters and/or the HCFM. Tunability of the diplexer is investigated considering different scenarios. Moreover, the concept is validated through measurement results.