# Miniaturized PIFA for 5G Communication Networks
## 1 Introduction  
Today, the miniaturization of the antenna is becoming increasingly needed due to the small size of the wireless communication system. As the size of the antenna is mainly determined by the wave length, it is difficult to miniaturize the antenna for current mobile communication services. To overcome this difficulty, the method of using dielectric materials with high permittivity to miniaturize the antenna has been studied by many researchers [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11]. However, this method causes a decline of the antenna gain due to the decline of the radiation effectiveness and dielectric loss. For this reason, the need to study the miniaturization of the antenna by modifying the structure of the antenna, not by using dielectric materials has increased. Therefore, this paper suggests a new method for designing a compact multi-band internal antenna with a patch and a ground plane for common mobile communication services. A patch antenna is a low-profile radio antenna which can be installed on a flat surface. It consists of a flat metal patch that is mounted over a ground plane. Patch antennas have a structure that is easy to fabricate, modify and customize. The original type of the patch antenna is the microstrip antenna. Two metal plates form a resonance in microstrip transmission lines which have a length of approximately one-half wavelength of the radio waves, and at these microstrip transmission lines, radiation occurs due to discontinuities. The radiation at the microstrip transmission lines gives the antenna a larger electric field area than its physical dimensions, which means that the antenna can be resonant. Usually, the length of the microstrip transmission line is slightly shorter than one-half a wavelength at the interested frequency, and a patch antenna is built on a dielectric plate. The designed multi-band internal antenna can cover the frequency bands for Global System for Mobile communications (GSM), Digital Cellular System (DCS), Personal Communications Service (PCS), Wideband Code Division Multiple Access (WCDMA), Long Term Evolution (LTE) communication services, and 5G communication networks. As mentioned above, there are many methods for the miniaturization of the antenna. In consideration of the antenna gain and the effectiveness, modifying the structure of the antenna is a better method to miniaturize the size of the antenna than using dielectric materials with high permittivity. Therefore, this paper suggests a new structure of a compact multi-band internal antenna for mobile handsets for WCDMA800, WCDMA850, GSM900, DCS, PCS, WCDMA2100, LTE2100 communication services and 5G communication networks.  
This paper is organized as follows. In Section 2, we design a multi-band internal antenna for various mobile communication services. In Section 3, we introduce a coordinate system for analyzing various antenna characteristics. Afterwards, we simulate and measure antenna characteristics, including antenna gain, voltage standing wave ratio (VSWR), and radiation pattern, in Sections 4 and 5. Finally, we conclude the paper and lay out our future research plan on related topics in Section 6.