Microstrip circuit applications of high-Q open microwave resonators

An open microwave resonator can be formed above a planar microstrip substrate by suspending a spherical reflector above it. A theory is developed to account for the coupling between such an open resonator mode and a microstrip line. The open resonator is shown to have useful circuit properties similar to a dielectric resonator, but with the potential of efficient operation well into the millimeter-wave range. Experimental confirmation of the theory is demonstrated by a scale model of a microstrip-based single-pole bandpass filter, which shows a loaded Q of 860 and a minimum loss of 0.8 dB+or-0.4 dB at 10 GHz.<
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