Compact Super Wideband Frequency Diversity Hexagonal Shaped Monopole Antenna With Switchable Rejection Band

Abstract

To reduce interference from other wireless communications, a compact super wideband frequency diversity hexagonal shaped monopole antenna with switchable rejection band capabilities is proposed. The patch consists of hexagonal structure with an open-ended horizontal slot that divides the patch into upper and lower parts. The overall size of the proposed antenna is 36 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,36$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,1.6$ </tex-math></inline-formula> mm on an FR-4 substrate material with a loss tangent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$tan\delta$ </tex-math></inline-formula> = 0.02. The notch switchable features and the frequency diversity are controlled by changing the length of the resonator through alternating the state of two inserted parallel PIN diodes inside the horizontal open-ended slot. The upper part of the hexagonal patch is connected to the negative terminal of the diodes and the biasing circuit in the back layer through a conducting via. The lower part is connected to the positive terminal of the diode. When both diodes are OFF, the proposed antenna behaves as a super wideband covering a bandwidth from 3.37 GHz to 27.71 GHz. When both diodes are ON, there is a band notch and a frequency a frequency band (3.81 – 6.62 GHz) is filtered. The antenna’s radiation pattern is broadsided directional, and the efficiency is observed 92.9% and 96% for the ON and OFF cases, respectively. The reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> ) at the rejection band is −3.06 dB at 5.38 GHz. Hence, the proposed super wideband antenna is well-suited for applications in wireless communications.