ANALYSES OF A SQUARE RING RESONATOR USED FOR BANDPASS FILTER DESIGN WITH MULTISPURIOUS SUPPRESSION

摘要

In this article, we proposed a method to analyze the voltages, currents, and imaginary impedances of the resonant modes in the square ring resonator by converting the square ring resonator to a guided wavelength transmission line. The impedance of the first four resonant modes of the ring resonator can be found and used as the coupling region for the bandpass response design with a high quality and multispurious suppression. A filter example using this concept was designed, fabricated, and measured. The filter composed of two square ring resonators and a half wavelength microstrip line showed a wide rejection bandwidth until four times the passband frequency. The simulated and measured results of the filter example were in a good agreement.