Optimisation of asymmetries in mm-wave single-element fractal antenna for gain-bandwidth enhancement

ABSTRACT

In this study, a low-loss substrate was used to create an Asymmetric Irregular Hexagonal Fractal (AIHF) mm-wave antenna. The antenna consists of an Asymmetric Defected Ground Structure (ADGS) attached to the bottom of a 0.55λ₀ ×0.40λ₀ ×0.032λ₀ mm³ substrate and an Irregular Hexagonal Fractal (IHF) patch on top of the substrate. The proposed fractal technique is unique and based on fractal-slot 3-stage iterations. The IHF patch is created by etching seven fractals arranged symmetrically about the y-axis, one of which has a central 1/3^rd (scaling) iteration factor and six hexagonal fractals that are 1/9^th of the parent 0^th order iteration. On the patch, these fractal slots are evenly spaced out. By etching an Asymmetric Cascaded Double Dumbbell (ACDD) slot on the ground plane, an ADGS is created. With this etching in the patch and ground, a gain of > 5.0 dBi for a −10 dB S₁₁ bandwidth of 4.655 GHz (32.84–37.215 GHz), a recorded peak gain of 13.4 dBi is at 33.55 GHz and an average radiation efficiency of 87.75% is achieved. Using the High-Frequency Structure Simulator (HFSS), the width of ADGS, the position of ACDD on ADGS, and the dimensions of etched fractals are optimised through a pattern search parametric iterative technique. These results are validated using the Vector Network Analyser (VNA), and the Anechoic Chamber and it is revealed that they agree well with the simulated results. The designed AIHF antenna’s RLC electrical equivalent circuit modelling is presented along with evaluated R, L, and C values.

KEYWORDS:

• AIHF
• ACDD
• fractal
• irregular
• gain-bandwidth

Disclosure statement

No potential conflict of interest was reported by the author(s).