ORIGINAL CONTRIBUTION Radiation Pattern of Chair Armed Microstrip Antenna Rabindra Kishore Mishra 1 • Kumar Satyabrat Sahu 1 Received: 5 October 2014 / Accepted: 7 July 2016 / Published online: 20 July 2016 Ó The Institution of Engineers (India) 2016 Abstract This work analyzes planar antenna conformable to chair arm shaped surfaces for WLAN application. Closed form expressions for its radiation pattern are developed and validated using measurements on prototype and commercial EM code at 2.4 GHz. Keywords Conformal antenna Á Microstrip Á WLAN Introduction Today’s market is oriented towards miniaturization on systems. The antenna size is mostly dependent on operating frequency. So, while the system size is shrinking, antenna needs to be integrated onto a hybrid of surfaces, which can be any combination of cartesian, cylindrical and spherical surfaces. Antenna mounted on cylinder, cone, or sphere are common conformal antennas as per the IEEE standard definition for conformal antenna [1] which reads as ‘con- formal antenna that conforms to a surface whose shape is determined by considerations other than electromagnetic’. Conformability to the mounting surface is one of the major advantages of microstrip antennas. Now days the con- formability property is also being used in textile and polymer composites [2]. However conformal microstrip antenna shows changes in properties in comparison to planar microstrip antenna. Studies on probe-fed conformal microstrip antenna have been reported [3–5] in recent past. In this work, the radiation pattern of a chair armed microstrip antenna (Fig. 1) has been investigated. Due to its ease of mounting on the conformal surfaces it is less prone to physical damages and poor visibility; and hence suitable for many medical appliances, textiles and different flexible polymer composites for communications. Though in late 80s and early 90s the radiation pattern of conformal microstrip antennas has been extensively studied [6–9], they were limited only to one type of surface (like conical, spherical or cylindrical). The challenge in this study is that there are three surfaces here: a cylindrical section (that is, the tip of the chair-arm) connected to cartesian sections at its two ends (Fig. 2a). Moreover, instead of using numer- ical techniques, approximate closed form formulae for radiation pattern based on principles of physics have been developed. The proposed closed form formulae are then validated using commercial em code and measurements on a prototype. For validating the formulation, conventional planar MSA is closed first and is simulated using computer sim- ulation technology (CST) microwave studio. Then, the Chair Armed MSA is simulated in CST to find its radiation pattern. Also the radiation pattern is obtained from the formulae developed in this paper. Then these radiation patterns are compared to observe the deviation of pattern between planar MSA and Chair Armed MSA as well as simulated pattern and the pattern from the analytical formula. Radiation Pattern Following standard procedure, four generalized integrals Eqs. (1)–(4) are defined for obtaining far field expressions in closed form. In these equations, for cartesian surfaces, & Rabindra Kishore Mishra r.k.mishra@ieee.org 1 Department of Electronic Science, Berhampur University, Bhanja Bihar, Berhampur, Odisha, India 123 J. Inst. Eng. India Ser. B (December 2016) 97(4):577–580 DOI 10.1007/s40031-016-0255-3