Low profile concentric distributed resonators and filters

In this paper we introduce a new family of low-profile and high quality factor distributed resonators, termed concentric distributed resonators. The study of the proposed resonators commences by the investigation of its key parameters, such as frequency of operation, quality factor and maximum electric fields as a function of the number of individual resonant elements along the periphery of concentric circles. In one case, it is shown that the height of the entire resonator can be kept as low as 3.5 mm, while still achieving a quality factor of about 1,400. As an experimental verification of the proposed resonators, a 3-pole filter is designed to operate at a frequency of 1.8 GHz with an absolute bandwidth of 40 MHz, equivalent to 2.22 %. Each resonant chamber of the presented filter consists of 25 individual resonant elements arranged in an interdigitated fashion along the circumference of three concentric rings. The internal height of the filter (5 mm) is among the lowest reported in the literature.