On the behavior of compact ultrawideband tunable bandwidth semicomplementary split ring resonator bandpass filter

Abstract

ABSTRACTThis article proposes a compact quasi elliptic ultrawideband band‐pass filter with low insertion loss using a defective ground structure (DGS). The proposed filter is a DGS filter. The measurements results for 1‐dB cutoff frequency show that, the pass‐band is 3.2–7.4 GHz or 79% fractional bandwidth at 5.3 GHz center frequency and minimum insertion loss in pass‐band is 0.33 dB at frequencies of 5.4 GHz with two transmission zeros are found at 1.8 and 8.6 GHz. The upper stopband is stretched up to 11.2 GHz, over which a rejection is higher than 21.2 dB. The group delay in pass‐band is less than 0.40 ns with a maximum variation of 0.1 ns approximately. Therefore, its value and variations is really low. The bandwidth of the proposed filter is potentially tunable and the 1‐dB cutoff fractional bandwidth can change from 58.4% at 4.62 GHz up to 98.4% at 5.93 GHz center frequency. Furthermore, the design methodology and some new geometries are presented. Moreover, the distributed equivalent circuit model based on geometrical filter parameters is introduced in this article. Thus, the microstrip‐slotline transitions are used for modeling the magnetic field coupling between microstrip line and slotline. Finally, this contribution proposes an improved model and results for the semicomplementary split ring resonator resonator that are shown by practical results, design methodology, and distributed equivalent circuit model. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:256–263, 2015