J Comput Electron DOI 10.1007/s10825-017-0995-6 Size miniaturization of microstrip antenna embedded with open-ended ground slots Bappadittya Roy 1 · A. Bhattacharya 1 · S. Mondal 1 · U. Chakraborty 2 · S. K. Chowdhury 3 · A. K. Bhattacharjee 1 © Springer Science+Business Media New York 2017 Abstract A compact rectangular microstrip antenna embed- ded with open-ended ground slots is presented in this paper. Three equal open-ended ground slots have been incorporated inside the ground plane in order to excite the antenna with a lower order resonant mode. On variation of the length param- eter of the middle slot of the antenna, a resonant mode of lower order has been obtained near 1.52 GHz. The maxi- mum size reduction of the designed structure is obtained, considering the lower band resonant frequency obtained is about 85.83% with a fractional bandwidth of 6.97%. The simple configuration has been fabricated on low-cost FR- 4 substrate material. The proposed low-profile triple band microstrip patch obeys all the necessary standards prescribed for wireless communication and, therefore, finds its applica- bility in multiband wireless communication systems. Keywords Size miniaturization · Open-ended slots · Meandering ground · Multiband antennas 1 Introduction Compact sized multiband antennas are of huge importance in modern wireless communication industry. One of the techniques for reducing the size of the handheld or wire- less communication devices is to reduce the size of the B Bappadittya Roy bappadittya13@gmail.com 1 Department of Electronics and Communication Engineering, National Institute of Technology, Durgapur 713209, India 2 Department of Electronics and Communication Engineering, National Institute of Technology, Silchar 788010, India 3 Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700032, India microstrip antenna used. In available literature, many popu- lar size reduction techniques for microstrip antennas have been discussed. In [1], an open-ended triangular slot has been added near the upper edge of the patch to lower the generated resonant frequency mode and to improve the gain- bandwidth of the antenna. As a result, the antenna size had been reduced by 46.2% with a bandwidth of 160 MHz. In [2] a microstrip patch has been designed using a “T”-shaped defected ground structure (DGS), where the resonant fre- quency has been tuned from 3.188 to 1.80 GHz with an impedance bandwidth of 4.03%. However, the size reduc- tion was about 80%. In Kang and Song [3], have shown that the 10 GHz resonant frequency has been lowered by 361 MHz with a fractional bandwidth of 3.61%. This has been achieved by controlling the air gap thickness of the substrate layer pro- duced due to application of an external DC bias. However, in the presented report, a very small shift of the resonant fre- quency and impedance bandwidth have been obtained, which was even less than 4%. Design of compact microstrip anten- nas using meandered ground slots has been presented in [4]. An analytical approach to study the behavior of defected patch structures has been carried out in [5], where the effects of shorted slots in microstrip patches have been discussed. A compact dual-band microstrip antenna for IEEE 802.11a WLAN application has been proposed in [6]. Also, various design techniques have been reported to reduce the size of the antenna designed with substrates with higher dielectric constant [7–12]. The objective of this work is to reduce the size of the antenna and excite a resonant frequency point around 1.5 GHz with higher gain and operating bandwidth and to investigate the effect of open-ended ground slots (OEGS) on the (1) resonant frequency, (2) bandwidth, and (3) gain of the antenna. The proposed antenna has gain of around 0.99 dBi at 1.52 GHz (lower resonant mode) with a size reduction of 123