1648 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 3, MARCH 2012 Low-Cost and High-Efficient W-Band Substrate Integrated Waveguide Antenna Array Made of Printed Circuit Board Process Nasser Ghassemi, Ke Wu, Stephane Claude, Xiupu Zhang, and Jens Bornemann Abstract—A novel class of low-cost, small-footprint and high-gain an- tenna arrays is presented for W-band applications. A 4 4 antenna array is proposed and demonstrated using substrate-integrated waveguide (SIW) technology for the design of its feed network and longitudinal slots in the SIW top metallic surface to drive the array antenna elements. Dielectric cubes of low-permittivity material are placed on top of each 1 4 an- tenna array to increase the gain of the circular patch antenna elements. This new design is compared to a second 4 4 antenna array which, in- stead of dielectric cubes, uses vertically stacked Yagi-like parasitic director elements to increase the gain. Measured impedance bandwidths of the two 4 4 antenna arrays are about 7.5 GHz (94.2–101.8 GHz) at 18 1 dB gain level, with radiation patterns and gains of the two arrays remaining nearly constant over this bandwidth. While the fabrication effort of the new array involving dielectric cubes is significantly reduced, its measured radi- ation efficiency of 81 percent is slightly lower compared to 90 percent of the Yagi-like design. Index Terms—Antenna array, substrate integrated waveguide (SIW), W-band antenna, Yagi-like antenna. I. INTRODUCTION A wide range of applications has attracted growing attention from industry and academia to the W-band (75–110 GHz) [1]. Operating fre- quencies of wireless communication systems have increased in order to provide access to a less crowded part of the electromagnetic spectrum and also a wider bandwidth for data transmissions [2]. As shown in [3], the atmospheric absorption is much lower at W-band frequencies than at 60 GHz. Therefore, given a point-to-point wireless communication link, the W-band spectral window offers the possibility of gigabyte data transmission over several kilometers in normal weather conditions [4]. Wide bandwidth and low atmospheric loss features permit the imple- mentation of high resolution and long range detectors or sensors [5], which may be used in helicopter or aircraft collision avoidance radar [6], civil avoidance security [7], passive millimeter wave imaging [8], and radar sensors [9]. One of the most critical parts of such systems are low-cost, low-profile and lightweight antenna components. Although various microstrip-fed antenna arrays have been studied and used, these configurations suffer from severe losses as frequency Manuscript received May 14, 2011; revised July 20, 2011; accepted August 31, 2011. Date of publication December 16, 2011; date of current version March 02, 2012. N. Ghassemi and K. Wu are with the Poly-Grames Research Center and the Center for Radiofrequency Electronics Research of Quebec (CREER), Depart- ment of Electrical Engineering, Ecole Polytechnique, University of Montreal, Montreal, QC H3V 1A2, Canada (e-mail: nasser.ghassemi@polymtl.ca; ke.wu@ieee.org). S. Claude is with the National Research Council of Canada, Herzberg Institute of Astrophysics, Victoria, BC V9E 2E7, Canada (e-mail: Stephane. Claude@nrc-cnrc.gc.ca). X. Zhang is with the Department of Electrical and Computer Engineering, Concordia University, Montreal, QC H3G 1M8, Canada (e-mail: xzhang@ece. concordia.ca). J. Bornemann is with the Department of Electrical and Computer Engi- neering, University of Victoria, Victoria, BC V8W 3P6, Canada (e-mail: j.bornemann@ieee.org). Color versions of one or more of the figures in this communication are avail- able online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TAP.2011.2180346 Fig. 1. Layout of a 1 4 antenna array ( , , , and ). increases to the millimeter-wave range [10]. Recently, substrate-inte- grated waveguide (SIW) technology has been proposed to provide a low-cost alternative for millimeter-wave applications [11]. SIW enjoys not only the advantages of rectangular waveguide features but also of- fers other benefits such as low cost, compact size, light weight, and easy fabrication using PCB or similar processes. Furthermore, SIWs can easily be connected to microstrip and coplanar waveguides utilizing a wideband transition [12]. High gain and wide bandwidth are two of the key requirements for a large number of antenna designs. To increase antenna gain, the use of a substrate with either permittivity or permeability is proposed in [13]. However, the bandwidth is inversely proportional to the gain, and material with is generally expensive and lossy. Due to its directive radiation pattern, the Yagi antenna has been widely applied in communication systems. However, it requires a boom to structurally support individual antenna elements [14]. To eliminate the boom, printed Yagi antennas were demonstrated in X band [15], [16], with radiation in a plane parallel to the substrate. But such antennas have a very large footprint. In many applications, an antenna is desired to have a broad radiation pattern in the plane perpendicular to the substrate. Therefore, an interesting approach is to use stacked director elements in a Yagi-like arrangement to increase the gain of printed antennas [17]. Later, this technique has been used in a multilayer Yagi-like microstrip antenna at 31 GHz [18], a dipole stacked Yagi antenna at 5.8 GHz [19], a dual polarized circular patch Yagi antenna at 5.8 GHz [19] and a stacked Yagi antenna at 60 GHz [20] with a very small footprint. In this communication, we present a different design of low-cost and high-efficiency 4 4 antenna arrays for applications close to 97 GHz. SIW technology is used to feed the antenna elements through longitu- dinal slots in the top metallization. The main difference compared to a similar Yagi-like array [20], which has been redesigned and is also presented for comparison, is that the multi-layered Yagi arrangement is replaced by a dielectric block, thus significantly simplifying the fab- rication process. Compared with previous millimeter-wave SIW slot antennas [21]–[23], the antenna structures presented in this communi- cation result in higher gain, larger bandwidth and higher radiation effi- ciency with a more stable (less dispersive) gain within the operational bandwidth. II. DESIGN The proposed 4 4 W-band antenna array consists of four 1 4 antenna arrays as shown in Fig. 1. Each 1 4 element has three basic layers. The bottom layer is the SIW feed network, which is designed using a 20 mil Rogers/Duroid 6002 substrate. It is shown in Fig. 2 for the entire 0018-926X/$26.00 © 2011 IEEE