Coplanar Waveguide Fed Ultra-Wide-Band Monopole Antenna for Radio Frequency Energy Harvesting Applications

Summary

This protocol defines the simulation, design, testing, and fabrication of a low-cost, coplanar waveguide-fed (CPW) Ultra-Wide-Band (UWB) antenna for radio-frequency energy harvesting (RFEH) across multiple communication bands.

Abstract

The RFEH based on wireless charging is a promising technology for powering low-energy Internet-of-Things (IoT) devices; however, its efficiency is still limited by antenna design and impedance matching. In this work, a printed antenna suitable for RFEH is developed with a CPW feed. The antenna is composed of a semicircular fractal curve, similar to a fig leaf tree radiating patch, with rectangular notches to be fabricated on an FR4 low-cost substrate. It has an operational bandwidth of 700 MHz to 3 GHz, covering key communication bands, including GSM, WLAN, ISM, and Wi-Fi applications. Numerical simulations were performed using computational electromagnetic modeling software. The experimental work demonstrated the suitability of this antenna for stable omnidirectional radiation patterns and successful RF-to-DC conversion efficiencies at the five target frequencies, including 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2400 MHz. The antenna shows potential for powering low-energy IoT devices in ambient RF conditions. The proposed work aims to compare the measured and simulated results. Lastly, the numerical and experimental results are compared and show remarkable agreement.

Introduction

Recent developments in wireless communication systems such as 5G, 6G, and IoT^1,2,3,4 have resulted in an increasing demand for efficient RFEH solutions. Urban environments are filled with ambient RF signals from cellular base stations, Wi-Fi access points, and broadcast transmitters, which makes them a suitable parasitic power source for low-energy electronic devices^5,6,7. In particular, UWB antennas, such as monopole configurations, are well-suited....

Protocol

The consumables, equipment, and software used are listed in the Table of Materials.

1. Antenna design and simulation

1. Substrate selection and initial geometry
   1. Select an FR4 substrate with a dielectric constant (εr) of 4.3, loss tangent (tan δ) of 0.025, and dimensions of 125 mm × 95 mm × 1.6 mm as seen in Figure 1.
   2. Open the electromagnetic field simulation software. Create a new project and set units to millimeters.
   3. Define the substrate material using the built-in FR4 model.
   4. Draw a semicircular copper patch (radius = 40 mm....

Results

Figure 1 shows the geometry of the proposed antenna, which consists of a semicircular radiating patch with two symmetrical rectangular notches and a CPW feed line. The surface current distribution at 1.8 GHz, as shown in Figure 2, confirms the strong current concentration along the feed line and the lower edges of the patch, consistent with the fundamental resonant mode responsible for the wideband impedance matching. Figure.......

Discussion

A simple modified monopole structure with two symmetrical rectangular notches is proposed to design a wideband CPW-fed UWB monopole antenna with a working frequency range from 700 MHz to 25 GHz. This section offers a critical methodological interpretation of the protocol, discusses optimization decisions and troubleshooting considerations, compares the design with existing approaches, and explores future applications and developments.

Key protocol steps that affect performance and repr.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Acetone (Photoresist Stripper)	Fisher Chemical	A18-4	Purity ≥ 99.5%
Ansys HFSS 2022 R2	Ansys Inc.		Version: 2022 R2, Solver: Finite Element Method (FEM)
Compact Anechoic Chamber	ETS-Lindgren	Model 5300	Internal dimensions: 4 m × 4 m × 4 m, Frequency range: 700 MHz – 40 GHz
Copper Cladding	Generic PCB copper foil		Thickness = 35 µm (1 oz), Adhesion = 1.5 N/mm²
CST Studio Suite 2022		Dassault Systèmes	Version: 2022, Solver: Finite Integration Technique (FIT)
Digital Multimeter (DMM)	Keysight	34461A	DC Voltage range: 0–100 V, Accuracy: ±0.0035%
Digital USB Microscope	Celestron	44308	Magnification: 10x–200x, LED illumination
Dry Photoresist Film	ORCAL	925	Thickness = 1.2 mil, Lamination temperature = 110 °C
Electronic Calibration Module (ECal)	Keysight	N4691B	Frequency range: 10 MHz – 26.5 GHz, 2-port
Ferric Chloride Etchant	MG Chemicals	415	Concentration = 40–42 °Baumé, Temperature = 40 °C
FR4 Epoxy Laminate	Isola Group	FR408	εr = 4.3, tan δ = 0.025, Thickness = 1.6 mm, Dimensions = 125 mm × 95 mm
Hot Roll Laminator	GBC	H65	Temperature range: 80–140 °C, Speed: 0.5–3 m/min
Isopropyl Alcohol (Cleaning Agent)	Sigma-Aldrich	34863	Purity = 99.9%
KiCad 7.0	KiCad EDA		Open-source, used for Gerber file verification
Lab Coat	Medline	DYNA23100	65% polyester / 35% cotton
Lead-Free Solder Wire	Kester	245 No-Clean	Diameter = 0.8 mm, Composition: Sn96.5/Ag3.0/Cu0.5
Motorized Antenna Positioner	Orbit	FR-959	Azimuth rotation: 0–360°, Elevation: ±180°, Step resolution: 0.1°
Nitrile Gloves	Kimberly-Clark	Kimtech	Powder-free, thickness: 5 mil
PCB Drill (for connector holes)	Proxxon	MICROMOT 50/E	Drill bit diameter: 1.2 mm (for SMA mounting holes)
Powercast P2110B Evaluation Board	Powercast Corporation		Integrated matching network, Schottky rectifier, and storage capacitor
Precision Tweezers	Excelta	225A-SF	Anti-magnetic, stainless steel
RF Signal Generator	Keysight	N5172B	Frequency range: 9 kHz – 13.6 GHz, Output power: +23 dBm
Safety Goggles	Uvex	Stealth	Anti-fog, UV protection
SMA Cable, 50 Ω	Huber+Suhner	Sucoflex 104	Length = 1 m, Frequency range: DC – 26.5 GHz, Insertion loss < 0.5 dB at 18 GHz
SMA Female PCB Edge Mount Connector	Amphenol	901-9871	50 Ω, Frequency range: DC–18 GHz
Sodium Carbonate (Developer)	Sigma-Aldrich	451614	Concentration = 1% w/v in deionized water
Standard Gain Horn Antenna	ETS-Lindgren	3164-05	Frequency range: 800 MHz – 5 GHz, Gain: 6–12 dBi
UV LED Exposure System	M&R	Saturn 2	Wavelength: 365 nm, Power: 120 W
Vector Network Analyzer (VNA)	Keysight	N5222B	Frequency range: 10 MHz – 26.5 GHz, Ports: 2