International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-1, Issue-2, February 2014 1 www.alliedjournals.com Abstract - Analysis of a single-feed arrangement of hexagonal patches by tuning the length and the angle of stub is proposed, which is capable of providing circular polarization along with broadband implementation. An antenna is designed on a glass epoxy FR-4 substrate with overall thickness of the structure less than 1.6 mm. VSWR bandwidth better than 1.213% at 5.7 GHz, 2.418% at 8.27GHz may be achieved with the proposed geometry. Measured Return loss and VSWR variations of the proposed antenna with frequency are compared to simulated results for better understanding. The measured E-plane and H-plane radiation patterns in the entire impedance bandwidth are same in shape, and the direction of maximum radiations is normal to the patch geometry. In the complete axial ratio bandwidth range of the proposed hexagonal patch antenna, the E-plane left circularly polarized patterns are nearly 15 dB higher than the corresponding right circularly polarized patterns. Therefore, in order to get the best performance regardless of the position of the Modern communication, circular polarization is chosen for design. By properly adjusting the location of the single feed point, hexagonal patch antenna with good circular polarization is created. Index Terms - VSWR bandwidth, SMA, circularly polarized, radiation patterns, hexagonal microstrip antenna. I.INTRODUCTION The Compact circularly polarized broadband microstrip antennas are becoming useful structures for modern communication systems including mobile, wireless, and global positioning systems [1, 2]. Microstrip antennas are small in size, and can be integrated with other planer components. Three main limitations associated with the conventional microstrip structures are their capability to resonate at a single frequency, narrow impedance bandwidth, and low gain. However with the demand of compact-size antennas for modern communication systems, several alterations in these antennas were proposed [3-5]. Fig. 1. Side view of hexagonal patch antenna Manuscript received February 15, 2014. Abhishek Joshi, Ph.D Scholar, BITS Pilani, Rajasthan, India The bandwidth of conventional microstrip antennas may be improved considerably by applying suitable narrow stub [6, 7] at an appropriate location on the patch [9]. Circular polarization in conventional patches may be achieved by suitable selection of the feed location [10]. With conventional patches, it is extremely difficult to achieve large impedance bandwidth and large axial ratio bandwidth simultaneously. In this paper, the design and performance of a compact single-feed arrangement of an antenna for circularly polarized broadband performance is reported. The proposed antenna provides improved impedance and VSWR bandwidths and also presents improved Return loss [8]. II.ANTENNA DESIGN AND RESULTS Single-Layer Hexagonal Microstrip Antenna with a Stub First, we have considered a single-layer hexagonal patch an- tenna with a narrow slot as shown in Figure 2. This antenna is designed on a glass epoxy FR-4 substrate (ε r -4.4, tanδ - 0.025, substrate thickness h- 1.58 mm). The simulation analysis of this antenna is carried out by applying HFSS simulation software [11]. The antenna is fed through a single inset feed arrangement by using an SMA connector. The patch has patch dimensions radius of 5mm. With optimization in stub dimensions 5mm x 2mm, it is realized that the best performance with such an antenna may be achieved by feeding diagonally. Fig. 2. Proposed design for analysis of hexagonal patch antenna The measured variation of the reflection coefficient (S 11 ) with frequency, as shown in Table 1, indicates that the antenna resonates at two frequencies, 5.6 GHz and 8.2 GHz, corresponding to two different modes of excitation. The measured input impedances presented by the antenna at these frequencies are close to 50 Ω, but the simulated gains at these frequencies are very low. The optimal impedance bandwidths of this antenna (for S 11 < -10 dB) at both resonance frequencies (5.6 and 8.2 GHz) are narrow Exploration of Dual Band Circularly Polarized Microstrip Antenna by Tuning the Dimension and Orientation of Stub Abhishek Joshi