Investigation of new nondegenerate dual-mode microstrip patch filter

A new nondegenerate dual-mode microstrip patch filter structure is introduced. The proposed filter is based on a square microstrip patch with four slots etched in symmetrical form. Besides its simple structure, the filter has the advantages of small size and low loss. The full-wave IE3D package is used to analyse the proposed structure. Design curves that relate the mode resonance frequencies and fractional bandwidth against slot parameters are presented. A bandpass filter is designed, analysed and tested at 2.15 GHz. Experimental results show good agreement with theoretical results.