Performance analysis of electrically coupled SRR bowtie antenna for wireless broadband communications

Abstract

This paper presents a broadband Bowtie antenna with metamaterial periodical structure for broadband wireless systems and emerging 5G communication frequency band. The modified Bowtie antenna operating from 4 to 6.8 GHz with electrically coupled split-ring resonator (ECSRR) unit cells are proposed and analyzed. In two element Bowtie antenna, the third tuning arms are included to improve matching in the proposed operating frequency band. Four different shaped electrically coupled split-ring resonator (triangle, elliptical, hexagon and pentagon) with negative permeability and negative permittivity metamaterial unit cells are proposed and their reflection properties are analyzed. The triangle shaped ECSRR have the broadband reflection phase property which can be used to enhance the gain of the Bowtie antenna. The 5 $$\times$$ 6 periodical ECSRR unit cell embedded with modified Bowtie antenna in FR4 epoxy substrate ( $$\epsilon _r$$ = 4.4, thickness = 1.6 mm, tan $$\delta$$ = 0.025) was designed and fabricated. The presented Bowtie antenna design achieves a wide impedance bandwidth of 50% from 4 to 6.8 GHz (S11 $$\le$$ $$-$$ 10 dB) and maximum gain of 5.75 dBi. The designed metamaterial periodical structure has the reflection bandwidth of 4–6 GHz within $$-$$ 90 $${^{\circ }}$$ to + 90 $${^{\circ }}$$ in reflection phase and zero degrees phase reflection at 5.5 GHz. The metamaterial embedded bowtie antenna achieves a maximum gain of 11.08 dBi at 5.5 GHz. By tilting the metamaterial periodical structure, the major lobe direction of the modified Bowtie antenna can also be tilted. The experimental results show that the major lobe of the antenna can be tilted 34 $${^{\circ }}$$ approximately for 30 $${^{\circ }}$$ tilting of metamaterial structure with maximum gain of 9.8 dBi.