International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-8, Issue-4, November 2019 9658 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: D9942118419/2019©BEIESP DOI:10.35940/ijrte.D9942.118419 Abstract : This paper presents a design of substrate integrated waveguide slot array antenna for X and Ku band applications. This is a low weight and simple profile antenna covering a vast range of frequencies. A substrate integrated waveguide is formed by two rows of metallized cylinders connecting upper and bottom layer of substrate. On the metallic plate, slot arrays are etched in a periodic fashion to achieve broad bandwidth. The SIW is excited by the microstrip feeding through a tapered transition to achieve smooth flow of current. The simulated result shows that -10 dB return loss of the proposed antenna is -35 dB, -29 dB and -22 dB at 11.1 GHz, 12.7GHz and 17.6 GHz respectively. The simulated bandwidth of the design is 7.6 GHz from 10.4-18 GHz which covers X band partially and Ku band. The gain of the antenna is about 6 dB. The proposed design is simulated using 3D full wave simulator named Ansys HFSS. Keywords : Substrate integrated waveguide, slot arrays, broad bandwidth, X band and Ku band applications. I. INTRODUCTION Substrate integrated waveguide (SIW) is an emerging technology for the design of microwave circuits, antennas and cost-effective components. Traditional transmission lines like microstrip and coaxial lines suffer conductor and radiation losses at high frequencies. The metallic waveguide has good performance at high frequency but it is bulky and costly. In order to balance the cost and performance, SIW was developed. This SIW has three layers namely top metallic layer, bottom metallic layer and intermediate dielectric substrate. Metallic cylinders are inserted between top and bottom metallic conductors. This SIW has the merits of high power handling capacity, low radiation losses and less fabrication cost. The structure of SIW is similar to dielectric filled rectangular waveguide [1]. The slot is etched on the top surface of the SIW to radiate the electromagnetic waves. Different shapes of slot [2-3] are etched to increase the bandwidth since conventional rectangular slot is a narrow band [4]. The slot arrays are introduced to create resonance at different frequencies and the bandwidth is extended for different microwave applications [5-7]. Such slot arrays on SIW is also employed to design passive devices like couplers [8], filters [9], etc. In this paper, slot arrays are etched on the top metallic layer of SIW and they finds its application in X and Ku bands. The SIW is fed through microstrip feeding on both the ends via tapered transition. Revised Manuscript Received on November 22, 2019. * Correspondence Author Rekha S*, Dept. of ECE, Sreenidhi Institute of Science and Technology, Hyderabad, Telangana. S Ramani, Dept. of ECE, Sreenidhi Institute of Science and Technology, Hyderabad, Telangana. II. DESIGN EQUATIONS OF SIW The proposed design is built on the substrate namely Rogers RT/Duroid 5880 having εr as 2.2, μ r as 1 and having dielectric loss tangent of 0.0009. The top and bottom geometry is shown in figure 1 and 2. The dimension of the proposed design is mentioned in Table 1. The overall dimension of the design is 40 x 14.6 x 0.762 mm 3 . The resonant frequency of the SIW slot array antenna is given in equation (1). (1) where, c - velocity of light in free space, εr - relative permittivity of the substrate, a,b,c - width, height and length of SIW, m,n,p - positive integers. To minimize leakage between the consecutive metallized cylinders, equation (2) and (3) are maintained. d/s ≥ 0.1 (2) d/λо ≤ 0.1 (3) where, d is diameter of the metallized cylinder, s is center to center distance between the successive cylinders and λ 0 is free space wavelength. The slots of a particular shape are etched in the definite intervals on the top conductor. These slots are placed on the dense current distributed region having a distance of λ/4 from the tapered edge. The distance of λ/4 is maintained in order to create constructive interference of radiated waves. Fig. 1. Top view of the proposed SIW slot array antenna Substrate Integrated Waveguide Slot Array antenna for Broadband Applications Rekha S, S Ramani