A Triband Patch Antenna with Monopole-like and Patch-like Radiation Patterns for Multifunctional Wireless Systems

Hai-Na Song,Zhao-Hui Chen,Jian-Feng Li

doi:10.1155/2020/3268729

Abstract

A triband patch antenna with monopole-like and patch-like radiation patterns for multifunctional wireless systems is proposed. The antenna consists of a single square radiation patch with an annular slot, a ground plane, and a top-loaded metal sheet. The top-loaded metal sheet is shorted to the ground plane for producing a zeroth-order resonant (ZOR) mode, which has an omnidirectional radiation pattern at the lowest operation band, and its performance is robust to the location of the probe feed. With the annular slot and the off-center probe feed, a dual-resonant TM01 mode is excited, yielding unidirectional radiation patterns for the two upper operation bands. The ZOR and the dual-resonant TM01 modes can be independently controlled, and a triband antenna prototype with a square patch of 24 mm is fabricated and tested. The first bandwidth is 2.5–2.7 GHz with omnidirectional radiation pattern, the second and the third bandwidths with unidirectional radiation are 3.3–3.9 GHz and 4.8–6.1 GHz, and the realized gains over the three bands are about 2.6, 6.5, and 7.5 dBi, respectively.

Highlights

With merits of 360° full coverage, low profile, low cost, and easy fabrication, monopolar patch antennas are widely used in portable devices, such as the mobile phone, laptop, and GPS
By etching a small annular slot into the square radiation patch, its original TM01 mode is split into two TM01 modes with controllable resonant frequencies, and they work at the two upper operation bands with unidirectional radiation pattern
A rectangular metal sheet printed on the top layer of FR4 substrate 2 is shorted to the ground plane through two conductive vias to excite a monopole-like zeroth-order resonant (ZOR) mode working at the lowest operation band. e dimension of the rectangular metal sheet is Ml × Mw, and the two conductive vias are arranged symmetrically with a distance of Vd. ere are two clearance circles etched on the radiation patch and are placed around the two conductive vias, respectively, and the radiation patch and the conductive vias are separated

Summary

Introduction

With merits of 360° full coverage, low profile, low cost, and easy fabrication, monopolar patch antennas are widely used in portable devices, such as the mobile phone, laptop, and GPS. Four monopoles shorted to the ground and one square patch loaded with a slot were utilized by the antenna to obtain dual-band and dual-sense radiation patterns [14]. Utilizing a top-loaded small metal strip, a dual-band circular patch antenna with omnidirectional ZOR mode for the lower band and unidirectional TM01 mode for the upper band was studied in [19]. For the proposed square patch antenna, the method for the square radiation patch to excite monopole-like ZOR mode is introducing a rectangular metal sheet, and its performance is robust to the probe feed position. By etching a small annular slot into the square radiation patch, its original TM01 mode is split into two TM01 modes with controllable resonant frequencies, and they work at the two upper operation bands with unidirectional radiation pattern. Based on the equivalent circuit as well as the distributions of electric field and current, the principles of the antenna are discussed. ese concepts are verified by a triband antenna prototype; it exhibits omnidirectional radiation in 2.5–2.7 GHz and unidirectional radiations in both 3.3–3.9 GHz and 4.8–6.1 GHz. e radiation efficiencies are larger than 77%, 84%, and 86% for the three operation bands, respectively

Antenna Design

Analysis of Working Mechanism

Conclusions