International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 08 | Aug 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1270 Improving Performance of Circularly Polarized Patch Antenna by Varying Stub Positions Gulshanpreet Singh 1 , Sehaj Rattan Singh 2 , Kuldeep Singh 3 1 Student, Department of Electronics & Communication Engineering, University Institute of Engineering and Technology, Panjab University, Chandigarh, India 2 Student, Department of Electrical & Electronics Engineering, University Institute of Engineering and Technology, Panjab University, Chandigarh, India 3 Assistant Professor, Department of Electrical and Electronics Engineering, University Institute of Engineering and Technology, Panjab University, Chandigarh, India ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - In this paper, we analysed the stacked microstrip planar antenna and improved its performance by implementing circular polarization through change in stub position. Circular polarization is necessary to have constant receiving power levels. In order to create circularly polarized radiation, it is required to excite two orthogonal patch modes on the antenna with 90° phase difference. The extent of improvement is measured through some parameters like return loss, axial ratio and radiation efficiency of antenna using IE3D software. Key Words: Axial ratio, Circular polarization, Return Loss, Radiation efficiency, Stub, Bandwidth 1. INTRODUCTION A three layer stacked microstrip planner antenna with air sandwiched in them is used. The outer layers are equally thick and have the same dielectric constant. Circular polarization [1] can be obtained by a number of methods [2] such as: 1. 3-dB hybrid 2. Truncated corner 3. Stub on radiating edge 4. Corner fed 5. Slot centre (Refer to Figure 1). An antenna mostly radiates an elliptical polarization defined by parameters such as axial ratio, tilt angle and sense of rotation. In our experiment we have used the Stub position method in order to generate unity axial ratio i.e.0 dB for a perfect circular polarization. 2. PROPOSED ANTENNA DESIGN The simple structure of single-feed circularly polarized microstrip antennas [3] does not require an external polarizer. Although this offer some advantages but the main weakness of an ordinary microstrip antenna is its narrow bandwidth. There are several techniques [4] to overcome this problem. We have used the method of stacked microstrip patch as shown below (Figure 2): Fig-1: (a) 3-db hybrid (b) Truncated corner (c) Stub on radiating edge (d) corner fed (e) Slot centre Fig-2: A patch antenna in a three layers dielectric The stacked microstrip patch method for the multilayer (three Layers) microstrip antenna structure involves addition of a superstrate layer [5] over the patch. With the addition of superstrate, effective permittivity of all the substrate reduces. Hence, the length of the patch is decreased than the original length required for the resonance at 2.4 GHz. We will use the following quasi- static equation [6] for the multilayer dielectric structure