Out-of-plane integration of multilayer strip-resonators and its application

A novel out-of-plane integration of multilayer strip-resonators is proposed. This kind of structure retains the merit of traditional in-plane integrated ones – simple and compact-sized, meanwhile, achieves the same amount of coupling with smaller horizontal space between resonators. Further miniaturisation of the previous bandpass filters (BPFs) can be realised by re-designing them based on the proposed structure. This Letter gives an example of an S-band BPF. A 52.4% size reduction is achieved by out-of-plane integration of resonators, while maintaining a comparable performance to the previous in-plane integrated design.