Research Article Logarithmic Slots Antennas Using Substrate Integrated Waveguide Jahnavi Kachhia, Amit Patel, Alpesh Vala, Romil Patel, and Keyur Mahant Department of Electronics and Communication Engineering, Charotar University of Science & Technology, Changa, Anand, Gujarat, India Correspondence should be addressed to Amit Patel; amitvpatel.ec@charusat.ac.in Received 29 May 2015; Revised 24 August 2015; Accepted 13 September 2015 Academic Editor: Xianming Qing Copyright © 2015 Jahnavi Kachhia et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. his paper represents new generation of slotted antennas for satellite application where the loss can be compensated in terms of power or gain of antenna. First option is very crucial because it totally depends on size of satellite so we have proposed the high gain antenna creating number of rectangular, trapezoidal, and I shape slots in logarithm size in Substrate Integrated Waveguide (SIW) structure. he structure consists of an array of various shape slots antenna designed to operate in C and X band applications. he basic structures have been designed over a RT duroid substrate with dielectric constant of 2.2 and with a thickness of 0.508 mm. Multiple slots array and shape of slot efects have been studied and analyzed using HFSS (High Frequency Structure Simulator). he designs have been supported with its return loss, gain plot, VSWR, and radiation pattern characteristics to validate multiband operation. All the proposed antennas give gain more than 9 dB and return loss better than −10 dB. However, the proposed structures have been very sensitive to their physical dimensions. 1. Introduction Rapid development in the ield of wireless communication system that operates in the microwave range is payed more attention from industry and academia [1–3]. In the present, rectangular waveguides are widely used in microwave engi- neering for antenna [4], ilters [5, 6], couplers [7], and so forth due to their advantages of low losses, high power handling, and high isolation [8]. In addition, slot array antennas based on waveguides that feature favorable antenna performance such as high directivity, low cross-polarization, and low cross- talk have been presented [9, 10, 15]. In 1943, the slot array was invented at McGill University in Montreal by Watson. One of the best features of this antenna is horizontal polarization and omnidirectional gain around the azimuth. A slot along the length is cut into the wall of a waveguide that disrupts the transverse current lowing in the wall, which enforces the current to travel at border of the slot and induces an electric ield in the slot [11, 12]. he location of the slot in the rectangular waveguide decides the current low. hus, the pose determines the impedance introduced to the transmission line and the amount of energy coupled and radi- ated from the slot. Slotted waveguide arrays (SWA) have some advantages over microstrip antennas such as having low loss, high isolation, and high power handling [11]. Due to these advantages, SWA antennas are widely used in communica- tion and radar systems particularly at microwave wave fre- quencies. Regarding conformal array applications, microstrip antennas are easier to implement compared to SWA anten- nas; however, excitation of antenna elements by a waveg- uide feed network is advantageous compared to micros- trip feed network in terms of eliminating radiation losses and cross coupling problems. Moreover, complex feed network structure is not needed in SWA to excite the slots in the same waveguide. Furthermore, the array of waveguides can be formed without cross coupling problems. However, the manufacturing of these waveguides needs to be accomplished with suicient accuracy so as to allow for operation at millimeter wave frequencies. On the other hand, antennas and microwave components used at lower frequencies typically rely on planar designs which are mostly realized with the Printed Circuit Board (PCB) processing technique [13, 14]. Moreover, conformal arrays have a speciic shape determined by the parameters other than radiation pattern and input match requirements and they can easily Hindawi Publishing Corporation International Journal of Microwave Science and Technology Volume 2015, Article ID 629797, 11 pages http://dx.doi.org/10.1155/2015/629797