Compact Diplexers With Folded Circular SIW Cavity Filters

Journal
IEEE transactions on microwave theory and techniques  
Volume
69
Issue
1
Start Page
111
End Page
118
Citation
IEEE Transactions on Microwave Theory and Techniques 69 (1): 111-118 (2021-01)
Publisher DOI
10.1109/TMTT.2020.3039545
Scopus ID
2-s2.0-85097938692
This work presents diplexers realized with folded circular substrate integrated waveguide (FCSIW) cavity filters. The properties of such cavities are analyzed, and empirical equations for calculating the resonant frequencies are given. The analysis relies on an even-/odd-mode decomposition. A 10-GHz filter is designed based on this approach. In the second step, its size is reduced, still maintaining the passband behavior. An asymmetric taper is used to connect two such filters to realize a diplexer. Two diplexers with center frequencies of 10/15 and 12/13.5 GHz are presented. The diplexers are several times more compact than comparable devices reported in the literature. The components are manufactured, and the functionality is demonstrated by simulation and measurements.