SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY Gain Enhancement of Patch Antenna Using L-slotted Mushroom EBG R Venkata Sravya, Runa Kumari Department of Electrical and Electronics Engineering Birla Institute of Technology and Science, Pilani Hyderabad Campus, Hyderabad, India firstname.lastname@example.org,email@example.com In , a cylindrical mushroom EBG is placed around a circular patch antenna to enhance gain by 2.9 dB. The EBG has two periodic structures: metallic rings and vias. A gain enhancement of 4.57dB is achieved by using mushroom EBG with a proximity fed V-band patch antenna, which is having liquid crystal polymer as its substrate . In , an N-shaped coplanar EBG structure without vias is designed. In this structure, all the EBG are interconnected. The comparison between patch antenna with EBG and without EBG resulted a gain of 1.9 dB, a bandwidth of 100 MHz and -3dB enhancement in return loss. A novel uniplanar compact EBG is designed in  by creating slots in it. Using this design, a gain enhancement of 3dB is achieved. Four layered rectangular slotted mushroom EBG is designed in , where a gain enhancement of 2.5 dB is achieved. The EBGs are arranged in chessboard format to reduce deformations caused by first layer of EBG and also to reduce RCS. In  a novel two via rectangular slot-EBG (TVS-EBG) is designed to achieve bandwidth enhancement by increasing effective capacitance. In this paper a new mushroom EBG with L- slot (LSEBG) is designed. A gain enhancement of 1.2 dB is achieved. The new EBG structure is based on mushroom EBG. On the EBG patch, an L shaped slot is created. The paper is organized as follows. Section II provides the analysis and design of the rectangular patch antenna without any EBG structure. In Section III, standard mushroom EBG is designed and the performance of the patch antenna along with EBG is studied. The new L-slot EBG structure design is explained in Section IV. A comparison of the results with mushroom EBG has been done. A conclusion is presented in Section V. All simulations are done in Ansoft HFSS. Abstract—Gain enhancement of patch antenna is investigated in this paper. A rectangular patch antenna fed by coaxial probe is designed for a resonant frequency of 5.8 GHz. The resulted gain and bandwidth are 5.3 dB and 160 MHz respectively. Using standard mushroom Electromagnetic Bandgap (EBG) placed at a distance 3 mm from edge of the patch, a bandwidth of 143 MHz and a gain of 5.5 dB is achieved. A novel L-slot mushroom EBG (LS-EBG) is proposed. The L-slot one layer and two layers of EBG structures are used to further enhance the gain by 0.6 dB and 1.2 dB respectively. Index Terms—Microstrip patch antenna, Mushroom EBG, surface waves, gain enhancement. I. INTRODUCTION Microstrip patch antennas are most commonly used for wireless communication . Few of its advantages are compactness, less weight, low cost, ease of fabrication etc. The major limitations of microstrip antennas are low gain (3 to 5dB) and narrow bandwidth (30MHz). In practical applications, a finite ground plane kept at a distance less than λ/4 from the radiating patch is used . This causes surface waves to be generated in the substrate, thereby decreases gain and bandwidth. To suppress the surface waves, high impedance surfaces such as EBG are used. EBGs are periodic structures which suppress/assist the propagation of electromagnetic waves (EM) in a specific band of frequency for incident angles and all polarization states . EBG can be categorized based on their geometrical configurations as: three-dimensional, twodimensional and one-dimensional. One such two dimensional EBG structure which suppress the EM waves is mushroom EBG. Mushroom EBGs are mostly used because of ease of analysis and fabrication. Mushroom EBG which is placed around the radiating patch at some distance, consists of a patch and vias. The vias is connected between the EBG patch and the ground plane. The mushroom EBG can be realized using lumped elements as LC-parallel resonance circuit where the current passing through the vias from EBG patch to ground plane generates inductance. The capacitance is generated because of the dielectric between two EBG patches (metal). II. ANTENNA DESIGN A microstrip patch antenna is designed at 5.6 GHz. The FR4 sheet (ϵr = 4.4, δ=0.002) with 1.6 mm height is used as a substrate in the proposed design The schematic of the proposed antenna structure is shown in Fig 1. The patch antenna dimensions are calculated using equations given in  and are found to be: length (lpatch) = 11.57 mm and width (wpatch) = 15.739 mm. 37 Authorized licensed use limited to: Birla Institute of Technology & Science. Downloaded on September 09,2021 at 09:42:37 UTC from IEEE Xplore. Restrictions apply. SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY f0 (2) (3) Ph L 1 2SLC BW K L C (4) where f0 is the resonant frequency, BW is the bandwidth, C is the capacitance and L is the inductor in mushroom EBG structure. The dimensions of mushroom EBG to resonate at 5.6 GHz are: width and length of EBG patch (w1 = L1) is 7 mm, periodicity (w1+g) = 8 mm. The vias diameter considered as 1 mm. The distance (G) between EBG layer and patch edge is 3 mm. The bandwidth and the gain obtained are 143 MHz and 5.517 dB respectively, shown in Fig. 4 and Fig. 5. The resulted gain in comparison to the patch antenna without EBG has been enhanced by 0.2 dB. Fig. 1.(a) Top view of rectangular patch (b) side view of Microstrip patch antenna with coaxial feeding Fig.3. (a) Top view of mushroom EBG (b) Schematic for Microstrip patch antenna with mushroom EBG Fig.2. Gain of microstrip patch antenna without EBG A coaxial probe feed at distance 4 mm along y-axis (y) and 2 mm along x-axis (x) from the center of the patch is used. The size of the substrate is 50 × 50 mm2. The bandwidth and gain obtained at 5.6 GHz is 160 MHz and 5.3 dB respectively. Fig. 2 shows the gain of the microstrip patch antenna without EBG. The gain of the patch antenna has been further enhanced by 0.2 dB and 0. 6 dB by using mushroom and L-slot mushroom EBG respectively. The design and analysis are explained in the following sections. III. ANALYSIS OF PATCH ANTENNA WITH MUSHROOM EBG A mushroom EBG shown in Fig 3 is designed using the Equations (1)-(4) given below . The substrate height (h) is considered to be 1.6 mm and the gap between the EBG patches (g) is considered to be 1mm. §W g · WH 0 (1 H r ) (1) ¸ cosh 1 ¨ C S ¨ © g Fig. 4. S11 plot for microstrip patch antenna with standard mushroom EBG ¸ ¹ 38 Authorized licensed use limited to: Birla Institute of Technology & Science. Downloaded on September 09,2021 at 09:42:37 UTC from IEEE Xplore. Restrictions apply. SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY Fig. 5. Gain of microstrip patch antenna with standard mushroom EBG IV. Fig.7 .Microstrip patch antenna with proposed L-slot mushroom EBG DESIGN OF THE PROPOSED SLOTTED MUSHROOM EBG In the previous sections design of patch and the patch antenna with mushroom EBG is analyzed. A new EBG substrate using L-slot mushroom EBG is presented in this section. The schematic of the proposed EBG substrate is given in Fig.6 and Fig. 7. The EBG is placed at a distance 3 mm (G, same as mushroom EBG) from patch edge. The EBG dimensions are: width of EBG patch (w1) = 7 mm, periodicity (w1+g) =8 mm, vias diameter (r) =1 mm, slot length (L2) =5 mm, slot width (w2) = 1 mm. The distance between L-slot and EBG patch center (d) is 2 mm. Fig. 8. S11 plot for microstrip patch antenna with L-slot mushroom EBG Fig. 9. Gain of microstrip patch antenna with L-slot mushroom EBG Fig. 6. Schematic for L-slot mushroom EBG (a) Square L-slot mushroom EBG with 7 mm EBG patch width (w1), 1 mm slot width (w2) and 5 mm slot length (L2) (b) Top view of microstrip patch antenna with L-slot mushroom EBG Fig.8 and Fig. 9 shows the S-parameter and Gain plots of patch antenna with L-slotted mushroom EBG. 39 Authorized licensed use limited to: Birla Institute of Technology & Science. Downloaded on September 09,2021 at 09:42:37 UTC from IEEE Xplore. Restrictions apply. SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY The gain of microstrip patch antenna with 2 layers of L-slot mushroom EBG is given in Fig 11. A comparison of the results has been done by tabulating the data, given in Table I. Using a slot EBG, the gain of the simple patch antenna can be enhanced by 1.2 dB. V. CONCLUSION In this paper, a new mushroom EBG with L-slot is designed and analyzed. The obtained gain of microstrip patch with L-slot mushroom EBG is 5.9 dB with one layer and 6.45 dB with two layers. The gain enhancement of 0.6 dB with one layer and 1.2 dB with two layers is achieved. The resulted gain of one and two layers of L-slot mushroom EBG in comparison to one and two layers of mushroom EBG is enhanced by 0.4 dB and 0.5 dB respectively. Fig.10. Schematic for patch antenna with two layers of L-slot EBG structure The bandwidth and gain obtained for patch antenna by using one layer of L-slot mushroom EBG is 143 MHz and 5.9 dB. The bandwidth obtained for patch with mushroom EBG and patch antenna with L-slot mushroom EBG is same. The patch with L-slot mushroom EBG results in a gain enhancement of 0.6 dB. A schematic for two layers of L-slot EBG with periodicity 8 mm is shown in Fig. 10. Further analysis has been done by using two EBG layers around the patch. When two layers of mushroom EBG is used the bandwidth and gain obtained are 143 MHz and 6 dB and with two layers of L-slot mushroom 146 MHz bandwidth and 6.45 dB gain is obtained. REFERENCES          C. A. Balanis, Antenna Theory: Analysis and Design. 3rd edition, John Wiley & Sons, Inc., Hoboken, New Jersey, pp:811-872 , 2005. D.F. Sievenpiper, “High Impedance Electromagnetic Surfaces,” Ph.D. dissertation, Univ. California, Los-Angeles, CA.1999. F. Yang and Y. Rahmat-Samii, Electromagnetic Band Gap Structures in Antenna Engineering. Cambridge University Press, 2009. H. Boutayeb and T. A. Denidni, “Gain Enhancement of a Microstrip Patch Antenna Using a Cylindrical Electromagnetic Crystal Substrate,” IEEE Trans. Antennas Propag., vol. 55, no. 11, pp. 3140– 3145, Nov. 2007. Y. Wang, J.-C. S. Chieh, and A.-V. Pham, “A wideband and high Gain V-band EBG Patch Antenna on liquid crystal polymer,” Antennas and Propag. (APSURSI), 2011 IEEE Interna. Symposium on, 2011, pp. 1820–1823. A. Ameelia Roseline, K. Malathi, and A. K. Shrivastav, “Enhanced performance of a Patch Antenna using Spiral-shaped Electromagnetic bandgap structures for high-speed wireless networks,” IET Micro. Antennas Propag., vol. 5, no. 14, pp. 1750-1755, 2011. Z.-J. Han, W. Song, and X.-Q. Sheng, “Gain Enhancement and RCS Reduction for Patch Antenna by Using Polarization-Dependent EBG Surface,” IEEE Antennas Wireless Propag. Lett., vol. 16, pp. 1631– 1634, 2017. M.S.S. Dalenjan, P.Rezari,M.Akbari,S.H.Gupta, and A.R.Sebak, “Radiation properties enhancement of a microstrip antenna using a new UC-EBG structure,” 17th Interna. Symposium on Antenna Techn. Applied Electromag. (ANTEM), 2016. P. P. Bhavarthe, S. S. Rathod, and K. T. V. Reddy, “A Compact Two Via Slot-Type Electromagnetic Bandgap Structure,” IEEE Micro. Wireless Propag. Lett.,, vol. 27, no. 5, pp. 446–448, May 2017. Fig. 11. Gain of microstrip patch antenna with 2 layers of L-slot mushroom EBG S.No 1 2 3 4 5 Table 1: Summary of Results for slotted EBG Structure Bandwidth Patch antenna without EBG 160MHz Patch antenna with mushroom EBG 143MHz Patch antenna with L-slot mushroom EBG 143MHz Patch antenna with 2 layers mushroom 143MHz EBG Patch antenna with 2 layers L-slot 146MHz mushroom EBG Gain 5.3dB 5.5dB 5.9dB 6dB 6.5dB 40 Authorized licensed use limited to: Birla Institute of Technology & Science. Downloaded on September 09,2021 at 09:42:37 UTC from IEEE Xplore. Restrictions apply.