Compact stop band filter based on double tuned rectangular split ring defected microstrip structure for ISM band applications

A novel compact stop band filter consisting of a rectangular split ring resonator (SRR) etched on the 50 ohm microstrip transmission line is presented in this paper for designing a sharp band rejection filter. Compared to the conventional defected slots like DGS, EBG etc., the proposed rectangular split ring shaped slot has a simple shape but compact in size as it occupies only the width of 50 Ω microstrip line. Another smaller rectangular split ring slot is attached inside the previous split ring slot to obtain a sharp double pole stopband response. Experimental results show that the proposed band stop filter with two rectangular split ring slots having a good agreement with theoretical simulation results. This double resonant bandstop filter can be tuned to reject the frequencies at 2.45GHz and 5.8GHz, which are applicable for ISM bands. This is useful to reject the notch band at 2.45 GHz and 5.8 GHz of an ultra wideband bandpass filter.