In this article, a novel square monopole antenna for ultra wideband applications with variable frequency band‐notch characteristic is presented. By using T‐shaped slots, additional resonances are excited and hence, the fractional bandwidth is increased up to 150%. A modified T‐shaped conductor‐backed plane is used to generate the frequency band‐stop performance. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2065–2069, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25395

A compact microstrip lowpass filter (LPF) with prominent cutoff sharpness and wide stopband is presented. The microstrip LPF is composed of a broadened microstrip line on the top side of the microstrip structure, an H-shaped defected ground structure (DGS) and a modified dumbbell (DB) DGS in the ground plane. It has a simple design procedure and easily can be tuned. The designed filter is developed and experimental results show that it has a sharp cutoff frequency response. Keywords: Defected Ground Structure (DGS), Elliptic function filter, Lowpass Filter (LPF) Classification: Microwave and millimeter wave devices, circuits, and systems Propag., vol. 153, no. 4, Aug. 2006. [5] J. Yang and W. Wu, "Compact elliptic function low-pass filter using defected ground structure," IEEE Microw. Wireles Compon. Lett., vol. 18, no. 9, Sept. 2008. [6] A. B. Abdel-Rahman, A. K. Verma, A. Boutejdar, and A. S. Omar, "Control of bandstop response of Hi-Lo microstrip lowpass filter using slot in ground plane," IEEE Trans. References