Low-Profile and Low-Volume Split-Distributed Resonators and Filters

A new class of low-profile resonators, named split-distributed resonators is introduced in this paper. The newly proposed resonator family features high quality Q-factors and relies not only on the coupling among the constituent resonant elements, but the constituent elements themselves are also made in the distributed form. This, in comparison with the standard distributed resonator, caters for extremely low profiles, while allowing for a more uniform distribution of the electromagnetic fields inside the resonant cavity and hence higher unloaded quality factors. Furthermore, a uniform distribution of the electromagnetic fields facilitates a tremendous reduction of the resonator volume. As an experimental verification, two 5-pole band-pass filters using different realizations of individual resonant elements are designed and fabricated. The filters operate at a centre frequency of 1.8 GHz with a percentage bandwidth of 2%. The individual split-distributed resonator of these filters consists of 9 resonant elements, where each element is a distributed resonator of the second order and fourth order respectively. The measured insertion losses of the filters are in a good agreement with the values predicted by the simulations.