Single-Layer Dual-Mode Microstrip Antenna With No Feeding Network for Pattern Diversity Application
Hui Deng, Lei Zhu, Neng‐Wu Liu, Zhong‐Xun Liu
Abstract
A single-layer microstrip patch antenna (MPA) under the operation of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes for pattern diversity application without needing to rely on any feeding network is proposed for the first time in this letter. Initially, when a thorough analysis on mode excitation and inhibition of the MPA was deeply conducted, it demonstrated that its TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes could be independently excited by properly placing two coaxial ports underneath the radiating patch; thus, generating the desired broadside and bidirectional radiation patterns, respectively. Then, two sets of shorting pins are inserted below the core radiator, aiming to raise the resonant frequency of its TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode in proximity to that of the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode. In addition, the maximum input resistances of these dual radiative modes decrease dramatically as f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> increase, which enables good impedance matching. Finally, the proposed MPA is designed, fabricated, and tested to validate the working principle. The results illustrate that this antenna can operate over the overlapping frequency ranges of 5.83-5.89 GHz with an envelope correlation coefficient of lower than 0.015, while keeping its low-profile thickness of 0.045λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Due to its unique advantages of low profile, simple structure, and good diversity, the proposed MPA could be a promising option in wireless local area network (WLAN)-related applications.