Research Article Performance Investigations of Quasi-Yagi Loop and Dipole Antennas on Silicon Substrate for 94 GHz Applications Osama M. Haraz, 1,2 Mohamed Abdel-Rahman, 3 Najeeb Al-Khalli, 4 Saleh Alshebeili, 1,3,4 and Abdel Razik Sebak 1,5 1 KACST Technology Innovation Center in Radiofrequency and Photonics for the e-Society (RFTONICS), King Saud University, Riyadh 11451, Saudi Arabia 2 Electrical Engineering Department, Faculty of Engineering, Assiut University, Assiut 71515, Egypt 3 Prince Sultan Advanced Technologies Research Institute (PSATRI), College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia 4 Electrical Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 5 Department of Electrical and Computer Engineering, Concordia University, Montreal, QC, Canada H3G 1M8 Correspondence should be addressed to Osama M. Haraz; osama m h@yahoo.com Received 27 August 2014; Revised 20 November 2014; Accepted 22 November 2014; Published 8 December Academic Editor: Kerim Guney Copyright © 2014 Osama M. Haraz 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 introduces the design and implementation of two high gain Quasi-Yagi printed antennas developed on silicon substrate for 94 GHz imaging applications. he proposed antennas are based on either driven loop or dipole antennas fed by a coplanar waveguide (CPW) feeding structure. For better matching with the driven antennas, a matching section has been added between the CPW feedline and the driven antenna element. To improve the gain of either loop or dipole antennas, a ground relector and parasitic director elements have been added. Two Quasi-Yagi antenna prototypes based on loop and dipole antenna elements have been fabricated and experimentally tested using W-band probing station (75–110 GHz). he measured results show good agreement with simulated results and conirm that the proposed antennas are working. In addition, a feed and matching coniguration is proposed to enable coupling a microbolometer element to the proposed Quasi-Yagi antenna designs for performing radiation pattern measurements. 1. Introduction In recent years, the printed Yagi-Uda antennas have attracted much interest with many applications in radar, millimeter- wave (MMW) imaging, wireless communication systems, phased arrays, and so forth. his is because they have many advantages such as wide bandwidth, high gain, low cost, end-ire radiation patterns, and ease of manufacturing and integration with other microwave circuits. In 1982, the printed Yagi-Uda antenna was introduced for the irst time [1]. It consists of a driven element, a relector, and one or more directors to create end-ire radiation characteristics. Presently, many researchers have exerted signiicant eforts to come up with several planar Yagi and Quasi-Yagi antenna designs to improve their performance [2–17]. One key factor to obtain a wide operating bandwidth is the design of a suitable feed structure for these kinds of antennas. A diferentially fed high gain Yagi-Uda antenna with folded dipole feed was introduced in [2]. However, it has a bigger size along with degraded performance because of its complex feeding structure. A Quasi-Yagi antenna with a wide bandwidth of 74% and a gain of 4–8dBi was proposed [3]. However, the asymmetry of those antennas also deteriorated their radiation performances. he complementary metal- oxide semiconductor transistor (CMOS) technology is used to design a CPW-fed on-chip Yagi-Uda antenna operating at 60 GHz [4]. However, a very low gain of −10 dB was achieved. In order to enhance the front-to-back ratio of the Quasi-Yagi antenna, another design based on a series-fed two-bowtie dipole array is presented [5]. In order to reduce the size of Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2014, Article ID 105625, 9 pages http://dx.doi.org/10.1155/2014/105625