RESEARCH ARTICLE Broadband and high gain stacked microstrip antenna array Suman Wadkar 1 | Balaji Hogade 2 | Rinkee Chopra 3 | Girish Kumar 3 1 Electronics and Telecommunication, Pillai College of Engineering, Navi Mumbai, India 2 EXTC, Terna Engineering College, Navi Mumbai, India 3 Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, India Correspondence Suman Wadkar, Electronics and Telecommunication, Pillai College of Engineering, Navi Mumbai, India. Email: swadkar@mes.ac.in Abstract In this article, broadband and high gain antennas are designed for bandwidth from 1.7 to 2.5 GHz which covers GSM 1800, 3G, 4G, and Wi-Fi applications. The antennas are designed using 1 bottom and 2 top patches (1B2T) stacked microstrip antenna configuration and its array. The antenna structures consist of copper metallic plate as the bottom patch and low-cost FR4 substrate for the top patches in air suspended mode. The antennas are enclosed in a metallic cavity which supports top substrate and increases gain and front-to-back ratio. The bandwidth for |S 11 | ≤-10 dB and peak gain for this configuration are 41.5% and 11.9 dBi, respectively. A broadband 2 × 2 array of 1B2T configuration is designed using tapered feed network to provide impedance matching for broad bandwidth. The structures are designed, fabricated, and tested. A bandwidth of 44% and peak gain of 16.6 dBi has been achieved using 2 × 2 array. The simulated and mea- sured results are in good agreement. The proposed anten- nas are good candidates for wireless communication systems. KEYWORDS broadband microstrip antenna, broadband microstrip array, electromagnetically coupled, high gain, multilayer multiresonator 1 | INTRODUCTION Antennas are one of the most important components for the communication link. With the enormous evolution of tele- com industry, defense, and satellite applications, microstrip antennas (MSA) have been the key area of research as they provide ease of integration, and have light weight. The requirement for broadband systems has led to the develop- ment of several MSA configurations. The bandwidth (BW) of MSA can be increased by using planar multi- resonator (gap coupled, directly coupled) and multilayer multi-resonator (electromagnetic coupling, aperture cou- pling) MSA configurations. 1–10 Broadband MSA using gap coupled resonators configuration along the radiating edges achieved BW (331 MHz, 10.06%) which is five times as compared to rectangular MSA (RMSA; BW of 65 MHz, 1.9%) in S-band at 3.29 GHz. 2 By using a broadband five gap coupled circular MSA (CMSA), BW of 160 MHz (18%) with a gain of more than 10.65 dBi at 2.6 GHz is achieved as compared to single CMSA BW of 40 MHz (4.5%) and 6.6 dB gain. 6 A multilayer multi-resonator probe-fed MSA has a BW of 41% and gain of more than 9 dB. 8 A 1-bottom and 2-top (1B2T) configuration of circular patches yield a BW of 47% with a gain of 9.54 dBi. 9 By using two parasitic patches along radiating edge and stacking 1 parasitic element on the top of fed patch, a BW of 42.65% and gain of 6.08 dBi is achieved. 10 The stacked coplanar waveguide fed MSA with a dog-bone slot has a BW of 21% and gain of 8.5 dBi at 4.68 GHz. 11 Another approach to obtain broad BW with increased gain is by using stacked and gap coupled multi-resonator MSAs. 12 In this configuration, three gap coupled patches of equal length are placed above a single bottom rectangular patch. A BW of 25.7% and gain of 10 dBi is obtained at 2.8 GHz. A stacked multi-resonator probe fed MSA provides BW of 41% and gain of more than 9 dBi. 13 A configuration 14 using wideband aperture coupled stacked MSA results in a BW of 32.5% at 20.42 GHz. Prox- imity feed technique has been employed to increase the BW for substrate thickness greater than 0.07λ O. 15 In broadband proximity fed RMSA, a BW of 40% and gain of 5 dBi is obtained. 16 The broadband proximity fed square ring MSA design gives a BW of 43% and 9-dBi gain at 1000 MHz. 17 Surrounding the patch elements with metal walls effectively prevents surface waves from being excited in the substrate thus allowing the substrate thickness to be increased without deleterious effects. 18 Several metamaterial antennas have Received: 18 December 2018 DOI: 10.1002/mop.31813 Microw Opt Technol Lett. 2019;1–7. wileyonlinelibrary.com/journal/mop © 2019 Wiley Periodicals, Inc. 1