Received April 25, 2018, accepted May 27, 2018, date of publication June 1, 2018, date of current version June 29, 2018. Digital Object Identifier 10.1109/ACCESS.2018.2842749 YIG Thick Film as Substrate Overlay for Bandwidth Enhancement of Microstrip Patch Antenna INTAN HELINA HASAN 1 , (Member, IEEE), MOHD NIZAR HAMIDON 1,2 , (Senior Member, IEEE), ALYANI ISMAIL 2 , (Member, IEEE), ISMAYADI ISMAIL 1 , ANWER SABAH MEKKI 1 , MUHAMMAD ASNAWI MOHD KUSAIMI 1 , SAMAN AZHARI 1 , AND ROSIAH OSMAN 1 , (Member, IEEE) 1 Institute of Advanced Technology, Universiti Putra Malaysia, Seri Kembangan 43400, Malaysia 2 Faculty of Engineering, Universiti Putra Malaysia, Seri Kembangan 43400, Malaysia Corresponding author: Intan Helina Hasan (i_helina@upm.edu.my) This work was supported in part by the Ministry of Science, Technology and Innovation, Malaysia (Science fund), under Grant 03-01-04-SF1860, Universiti Putra Malaysia (Putra) under Grant GP-I/9439400, and in part by the Ministry of Higher Education, Malaysia (NanoMITe), under Grant LRGS/2015/UKM-UPM/NanoMITe/04/02. ABSTRACT Research on microstrip patch antenna (MPA) has been growing in the past few decades due to its planar profile and easy fabrication. Its simplicity of structure, which includes a conductive patch, a dielectric substrate, a ground plane, and a microstrip feeder, is making it more popular for integration in devices which are more focused on miniaturization and flexibility. There are, however, a few disadvantages of MPA, such as narrow bandwidth, low power, and limited inexpensive material selection if a current printed circuit board etching fabrication technique is used. Ferrite substrates are known to be able to help overcome this issue, but the properties of bulk ferrites are difficult to control. This paper aims to solve this problem by using thick-film technology, which utilizes a screen printing method to include ferrite thick film in the MPA structure as substrate overlay to help enhance the performance of MPA. Yttrium iron garnet was chosen as the starting ferrite nanopowders, and the preparation and characterization of the ferrite thick-film paste were carried out to investigate properties of the thick film. Results showed that the thick film showed moderate permittivity and permeability, which is suitable for MPA fabrication. The actual fabricated MPA with ferrite thick-film inclusion on FR4 substrate showed that the thick film improved the performance of MPA with low firing temperature of 200 ◦ C. For MPA which is designed to work at 5.8 GHz, the return loss and −3-dB bandwidth improved 100% and 73%, respectively. In conclusion, ferrite thick-film inclusion in MPA fabrication has proven to improve the performance of the antenna in terms of return loss and bandwidth enhancement. INDEX TERMS Ferrites, patch antennas, printed circuits, thick films, yttrium compounds. I. INTRODUCTION Antenna plays a very important role in telecommunication technology; without antenna integrated in a communication device, the device cannot send or receive information in the form of signals. There are several types of antennas, including dipole antenna, horn antenna, wire antenna and others. In 1950s, microstrip patch antenna (MPA) was first introduced [1] and since then has gained a lot of interests from telecommunication industry players due to its flat or planar profile, easy to fabricate, small size and lower manufacturing cost. This type of antenna is currently widely applied in wireless communication systems, including cellu- lar devices, Global Positioning System (GPS) devices, and wireless internet routers [2], [3]. Patch antenna is typically constructed by fabricating a conductive patch onto a dielectric substrate. The permittivity and thickness of the substrate give influences to the parameters of the antenna, including the resonant frequency, bandwidth and return loss of the antenna [4], [5]. There are few types of materials that are being studied and used as the substrate, such as ceramic, VOLUME 6, 2018 2169-3536  2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. 32601