Methodology of Band Rejection / Addition for Microstrip Antennas Design Using Slot Line Theory and Current Distribution Analysis Yasser M. Madany * , Senior Member, IEEE, Ayman I. Almahallawy ** , Graduate Student Member, IEEE, and Hassan M. Elkamchouchi *** , Life Senior Member, IEEE Communications and Electronics Department, Alexandria University, Egypt E-mail: * ymadany@ieee.org, ** almahallawy@ieee.org, *** helkamchouchi@ieee.org. Abstract—Radio or wireless communication means to transfer information over long distance without using any wires. Millions of people exchange information every day using pager, cellular, telephones, laptops, various types of personal digital assistance (PDAs) and other wireless communication products. The worldwide interoperability for microwave access (Wi-Max) aims to provide wireless data over a long distance in variety of ways. It was based on IEEE 802.16 standard. It is an effective metropolitan area access technique with many favorable features like flexibility, cost, efficiency and fast networking, which not only provides wireless access, but also serves to expand the access to wired network. The coverage area of Wi-Max is around 30-50 km. it can provide high 100 Mbps data rates in 20 MHz bandwidth on fixed and nomadic applications in the 2-11 GHz frequencies. In this paper, a methodology of band rejection/ addition for microstrip antennas design using slot line theory and current distribution analysis has been introduced and analyzed. The analysis and design are done by a commercial software. The radiation characteristics, such as; return loss, VSWR, input impedance, and the surface current densities have been introduced and discussed. Finally, the proposed optimum antenna design structure has been fabricated and the measured S-parameters of the proposed structure can be analyzed with network analyzer and compared with simulation results to demonstrate the excellent performance and meet the requirements for wireless communication applications. Keywords—Microstrip patch antenna; band rejection/addition methodology; slot line theory; current distribytion analysis; wireless communication applications. I. INTRODUCTION With the progress in wireless communications techniques in recent years, a new promising concept of wireless systems has received well-deserved attention by researchers all over the world. The most important component in wireless is its TX/RX antenna. Advantages like low power consumption, high data rate wireless connectivity and simple hardware configuration made microstrip patch antenna a primary choice for application in wireless communication technology. Also, the radiation pattern characteristics depend on the substrate parameters as well as on the antenna geometry. The dielectric constant of the substrate is generally low (ε r < 9.8) and the substrate is electric-ally thin [1]-[5]. In Ref. [6], a notch frequency has been added using only the slot line theory. The basic slot line consists of a dielectric substrate of dielectric constant with a narrow slot width etched in the metallization on one of the surfaces of the dielectric substrate of thin thickness [7]-[14]. In this paper a methodology of band addition/rejection for multiband patch antennas design, using slot line theory and current distribution analysis has been introduced with more effective, accurate and efficient method compared with the method discussed in Ref. [6]. The proposed structure has been designed using Rogers RT/duroid 6006 substrate with (ε r = 6.15, tanδ = 0.0019) and thickness of 0.635 mm. The characteristics of the proposed structure are obtained and analyzed using HFSS simulator [15] to demonstrate the performance. The optimum proposed design structure at the frequency range 2-11 GHz has been fabricated measured and analyzed with Agilent 8719ES S-Parameters network analyzer. II. THE SLOT LINE THEORY Slot-line is considered one of the most important and widely used structures in the design of band rejection/addition or band enhancement antennas. Design formulas, based on Ref. [7], are provided for the effective dielectric constant ε eff and the characteristic impedance Z 0 . The effective dielectric constant is the inverse of square of the normalized slot wavelength λ g /λ 0 . The characteristic impedance is based on the power-voltage definition, Z 0 = |V| 2 /P, where V is the rms transverse voltage across the slot in the plane of the slot and P is the average power flow along the slot. Since the slot line is non-TEM in nature, its characteristic impedance is not defined uniquely. For selected substrate material with ε r = 6.15 and h = 0.635 mm, the following formulas are all valid for the frequencies 3, 4, and 5 GHz within 0.006 ≤ h/λ 0 ≤ 0.06 and 0.0015 ≤ w/λ 0 ≤ 1.0, where h is the substrate thickness and w is the slot width. (1) (2) 2014 Loughborough Antennas and Propagation Conference (LAPC) 10 - 11 November 2014, UK 978-1-4799-3662-5/14/$31.00 (C)2014 IEEE 602