Performance of CRLH-TL-Hilbert Structure Inspired Antenna Loaded with AMC Reflector for Wireless Applications

Summary

This study presents a high-gain CRLH transmission line antenna integrated with a Hilbert fractal EBG and an artificial magnetic conductor reflector for 5G sub-6 GHz applications. The design achieves 20 dBi gain, 2.1 GHz bandwidth, improved front-to-back ratio, and limited optical beam steering using light-dependent resistors for reconfigurability.

Abstract

This study presents a novel reconfigurable antenna design for 5G‑sub6 GHz communication networks, achieving significant gain enhancement and beam‑steering capability through the synergistic integration of a composite right/left‑hand transmission line (CRLH‑TL), a Hilbert‑curve electromagnetic bandgap (EBG) structure, and an artificial magnetic conductor (AMC) reflector. The antenna comprises 17 CRLH TL unit cells coupled to a third-order Hilbert fractal EBG, eliminating conventional via holes and minimizing surface-wave losses. Without the AMC reflector, the antenna achieves a peak gain of 16 dBi at 5.6 GHz. Incorporation of a 7 × 10 hexagonal AMC reflector array exhibiting zero reflection phase enhances forward gain to 20 dBi at 5.6 GHz, representing a 4 dB improvement while suppressing back lobes and producing a unidirectional radiation pattern. Reconfigurability and beam‑scanning are enabled via an optical switching mechanism employing light-dependent resistors (LDRs), achieving gain variation and ±5° beam steering at 5 GHz. The design achieves a 2.1 GHz impedance bandwidth (S11 < –10 dB) and 78% radiation efficiency. Compared to prior CRLH‑TL antennas, this work demonstrates a 4 dB gain improvement and introduces optical reconfigurability without via-based fabrication complexity. Simulation and measurement results exhibit excellent agreement, validating the design methodology. The proposed antenna is suitable for adaptive 5G base stations, satellite communications, and beam-steerable radar systems.

Introduction

The increasing demand for adaptive, high-performance antennas in fifth-generation (5G) wireless communication systems has accelerated research into metamaterial (MTM)-based designs^1,2. Metamaterials offer unique electromagnetic properties, including negative permittivity and permeability, which enable zero-order resonance in composite right/left-hand transmission line (CRLH-TL) structures, facilitating significant antenna miniaturization^3,4. However, conventional MTM antennas frequently suffer from low gain, narrow impedance bandwidth, and fabrication ....

Protocol

Antenna design and simulation setup
The antenna was designed using commercial 3D electromagnetic simulation software based on the finite integration technique (FIT)¹⁰. The simulation parameters were configured as follows: (i) solver type: time domain solver with hexahedral mesh; (ii) frequency range: 4–7 GHz; (iii) mesh density: 20 lines per wavelength, adaptive mesh refinement enabled with accuracy threshold of –30 dB; (iv) boundary conditions: open (add space) in all directions with minimum distance of λ/4 from the structure; (v) farfield monitors: configured at 0.1 GHz intervals across the frequency ra....

Results

Antenna design and simulation setup
The simulated and measured S11 parameters for the baseline CRLH-TL antenna (without AMC reflector) demonstrated excellent agreement across the 3–6 GHz frequency range. The antenna exhibited a –10 dB impedance bandwidth of 2.1 GHz (3.7–5.8 GHz), with the minimum S11 of –32 dB occurring at 5.6 GHz. The corresponding VSWR was below 1.5 across the entire operational bandwidth. Parametric studies revealed that increasing the number of interdigital capacitor fingers from.......

Discussion

This work proposes a novel methodology for achieving high-gain, reconfigurable radiation in a planar metamaterial antenna through the synergistic integration of three complementary technologies: via-less CRLH TL with Hilbert EBG for loss minimization, a zero-phase AMC reflector for gain enhancement, and optical LDR switching for reconfiguration that inspired by Al Naiemy²¹. The approach uniquely eliminates the fabrication complexity associated with conventional via-based CRLH‑TL implementati.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Substrate	Taconic	www.taconic.co.kr/rf-43	Rogers RT/duroid 8550, εr=2.55, h=1.5 mm
Photoresist	MicroChemicals	www.microchemicals.com/products/az-4562	AZ 4562 positive photoresist
Developer	MicroChemicals	www.microchemicals.com/products/az-400k	AZ 400K developer concentrate
Etchant	Sigma-Aldrich	270290-1KG	Ferric chloride, 40% w/v
Solvent	Sigma-Aldrich	270725-1L	Acetone, semiconductor grade
Solvent	Sigma-Aldrich	278475-1L	Isopropyl alcohol, semiconductor grade
Conductive epoxy	CircuitWorks	www.chemtronics.com/cw2400	CW2400 conductive epoxy
LDR	Advanced Photonix	PDV-P8103	Light-dependent resistor, 5-10 kΩ (light) / 1 MΩ (dark)
Laser diode	Thorlabs	L635P5	635 nm, 5 mW, elliptical beam
Galvanometer	Cambridge Technology	6215H	Optical scanning mirror system
VNA	Keysight	37347A	Vector network analyzer, 10 MHz-20 GHz
Horn antenna	ETS-Lindgren	3117	Dual-ridge horn, 1-12 GHz
Positioner	ORBIT/FR	AL-4163-4A	Azimuth/elevation positioning system
RF chamber	ETS-Lindgren	FACT-3	Shielded enclosure, 4.5×3.0×2.5 m
Simulation software	Dassault Systèmes	CST Studio Suite 2023	3D electromagnetic simulator