Loop-Gap Resonator: A Lumped Mode Microwave Resonant Structure

Loop-gap resonators are newly developed microwave resonant structures with a field configuration that is intermediate between lumped and distributed. Typical characteristic dimensions are of the order of 1/10 of the resonant wavelength, and typical Q's are of the order of 1600-2000 in the frequency range of 1-4 GHz. Data are presented for Q's and frequencies for a series of resonators of various dimensions and compared with theory. Various coupling and frequency tuning techniques are discussed, and results of experiments are reported. Results of preliminary application of the stictire in microwave filters and oscillators are presented. Loop-gap resonators provide a useful design alternative, it is concluded, to dielectric and surface acoustic-wave resonators at low microwave frequencies.