Compact Design of Modified Pentagon-shaped Monopole Antenna for UWB Applications Sanyog Rawat 1 , Ushaben Keshwala 2 , and Kanad Ray 3 1 Manipal University Jaipur, India. 2 Amity University Uttar Pradesh, India. 3 Amity University Rajasthan, India. Email: sanyog.rawat@gmail.com; ukeshwala@amity.edu; kanadray00@gmail.com Abstract— In this work detailed analysis of a modified, pentagon-shaped planar antenna is presented for ultra-wide bandwidth (UWB) applications. The proposed antenna was designed on an FR-4 substrate and has a compact size of 12 × 22 × 1.6 mm 3 . It achieves an impedance bandwidth of 8.73 GHz (3.8–12.53 GHz) in the UWB range. The design has a uniform gain and stable radiation pattern in the operating bandwidth. Index Terms—Golden angle, pentagram, pentagon, star- shaped antenna I. INTRODUCTION Nowadays, wireless communications and their high- speed data rate are becoming increasingly popular. The research in the field of microstrip antennas has also been conducted at higher speeds to achieve a higher data rate. Since the declaration of the ultra-wide bandwidth (UWB) band (3.1-10.6 GHz) by the Federal Communication Commission in 2002 for commercial use, research on UWB antennas has reached new heights [1]. The UWB monopole antennas have become one of the most emerging fields of research to acquire ultra-wide bandwidth and high data rate for wireless communication. Recently, many wideband UWB monopole antennas with different shapes have been proposed [2]-[4]. Many star-shaped and pentagon-shaped antennas are also presented and reported [5]-[8]. Many similar modified UWB configurations for wider bandwidth, multi-band response, and notch characteristics have been investigated using slots in the radiating patch, ground plane, or feed line [9]-[12]. Many of the reported antennas are very large in size and have complex structures. The star- shaped antennas presented are not regular star-shaped pentagrams but have more than five angles. The presented antenna is of a very compact size when compared to the previously investigated structures. The unique feature of a golden ratio is incorporated to design the pentagram star-shaped patch geometry. The initial design of the pentagram star-shaped monopole was modified to another pentagon monopole for enhanced radiation performance. Both geometries retain the concept of a golden ratio in their structures. The paper is organized into three sections. Section I consists of the Manuscript received November 18, 2017; revised March 28, 2018. introduction, and in Section II the initial antenna geometry is presented and discussed. In the preceding section, the modified pentagon-shaped antenna is elaborated and the results are discussed. II. ANTENNA GEOMETRY A. Initial Pentagram Star-shaped Antenna The antenna presented in this paper was designed on a FR-4 substrate, which was a partial ground on one side and a conducting patch on the opposite side. The antenna design is initially started with a pentagram star shape and then the shape was modified into a pentagon shape. The pentagram is also called a pentangle, i.e., 5-pointed star [13]. The geometry of the microstrip line fed star-shaped monopole antenna is shown in Fig. 1. The width and length of the presented antenna are 12 mm and 22 mm, respectively. The star (pentagram)-shaped patch was printed on one side of the FR-4 substrate. The overall side length of the pentagram is a = 10.47 mm. The full ground was optimized to a partial ground for improved results. The overall dimensions of the antenna are 12 × 22 × 1.6 mm 3 . The pentagram considered in this paper is a regular five angle star [13]. The pentagram star has one unique quality or number hidden inside its geometry called the golden ratio, which is approximately equal to 1.618 and denoted by the letter Phi (Φ =1.618). The golden ratio is also known as the golden mean or divine proportion. The unique characteristic of the golden ratio is that it differs from its reciprocal by unity [14], given by Φ−1/Φ = 1 (1) Figure 1. The geometry of the pentagram star-shaped monopole antenna: (a) Front-view and (b) back-view. The concept of the golden ratio was utilized for the design of the patch geometry. The golden ratio for the International Journal of Electrical and Electronic Engineering & Telecommunications Vol. 7, No. 2, April 2018 ©2018 Int. J. Elec. & Elecn. Eng. & Telcomm 66 doi: 10.18178/ijeetc.7.2.66-69