INVERTED L-SHAPED AND PARASITICALLY COUPLED INVERTED L-SHAPED MICROSTRIP PATCH ANTENNAS FOR WIDE BANDWIDTH D. K. Neog, 1 S. S. Pattnaik, 2 M. Dutta, 3 S. Devi, 2 B. Khuntia, 2 and D. C. Panda 2 1 Dhemaji College Dhemaji Assam, Pin. 787 057, India 2 NERIST, Nirjuli-791 109, India 3 Tezpur Central University Assam, India Received 23 December 2003 ABSTRACT: Coax-fed inverted L-shaped microstrip antennas and par- asitically coupled inverted L-microstrip antennas are presented. The inverted L-shaped microstrip antenna gives an impedance bandwidth of 30.6%, which is increased to 33.7% by parasitic coupling. The band- width has been achieved with a substrate thickness of 2 mm. Radiation patterns and gains are also studied and presented. © 2004 Wiley Peri- odicals, Inc. Microwave Opt Technol Lett 42: 190 –192, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20248 Key words: inverted L-microstrip antenna; parasitically coupled; radia- tion pattern; wide bandwidth INTRODUCTION Microstrip antennas in various forms and geometries have been exten- sively used in many applications [1, 2]. In the recent past, significant work has been reported on small size, broadband width, and suitable polariza- tion of microstrip antennas for wireless communication systems. To enlarge the inherent narrowband width of microstrip patch antennas, a large number of techniques have been proposed. The use of thick sub- strate, stacking, and so on, is among the acceptable techniques in broad- band design. In this paper, the authors have successfully generated a wide-bandwidth 30.6% impedance bandwidth and a 26.5% pattern band- width by the asymmetric feeding of an inverted L-microstrip patch antenna in its narrow side. The large bandwidth has been achieved on a substrate thickness of 2 mm (thin substrate) without any stacking or parasitic elements. Upon seeing the current distribution of the inverted L-microstrip patch, a parasitic strip is placed on the side of the notched edge to compensate the reactance component in order to generate further wideband width. An impedance bandwidth of 33.7% and a pattern bandwidth of 33.7% are achieved by this method while occupying a space similar to that of a rectangular microstrip antenna. The size of the antenna is also 1/3 rd of the wavelength. DESCRIPTION OF ANTENNAS Figure 1(a) depicts the geometry of the inverted L-microstrip antenna, which is fed at a point ( x f = 3.8 mm, y f = 3.2 mm), whereas Figure 1(b) represents the parasitically coupled inverted Figure 1 (a) Inverted L-shaped microstrip antenna; (b) parasitic coupled inverted L-shaped microstrip antenna Figure 2 Smith Chart plot of (a) inverted L-shaped microstrip patch antenna; (b) parasitically coupled inverted L-shaped microstrip patch an- tenna. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] 190 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 42, No. 3, August 5 2004