Microstrip—line split—ring resonators and their application to bandpass filters

The author has already reported a much more miniaturized split‐ring resonator compared with the existing one‐wavelength ring resonators by using microstrip lines and a prototype two‐stage tunable bandpass filter. In the present paper, basic characteristics and salient features of split‐ring resonators are summarized. Using a general‐purpose simulation program for analysis of microwave circuits, calculating methods of filter coupling parameters, derived by using generalized expression of inverters, were described. The design chart was constructed indicating the concrete steps for designing. Finally, a three‐stage filter for a 600‐MHz band based on the forementioned results was designed and fabricated, and its operational characteristics were presented. The experimental results agreed quite well with the results of a computer simulation. The validity of the present design method has been confirmed. The bandpass filters using split‐ring resonators have a suitable structure for a high‐frequency hybrid IC. They are considered to be applicable over a wide frequency band in UHF to SHF bands.