Advanced Electromagnetics

Polarization-Reconfigurable Single-Port Patch Antenna with Switchable Horizontal and Vertical Modes for Mid-Band 5G Applications

2026-05-14T08:28:55+02:00

With the growing demand for compact, high-performance and reconfigurable antenna systems in mid-band 5G communication (3.3–6 GHz), polarization agility has become essential for improving link reliability and spectral efficiency. This paper presents the design, simulation and experimental validation of a polarization reconfigurable microstrip patch antenna capable of dynamically switching between vertical (VP) and horizontal (HP) linear polarization states using a single RF excitation port. The antenna employs two orthogonal microstrip feedlines connected via PIN diode switches to a common feed, enabling selective excitation of adjacent patch edges. This facilitates activation of the fundamental TM01 or TM10 mode, producing vertical or horizontal polarization, respectively. Fabricated on an FR4 substrate, the antenna features a low-profile, planar configuration ideal for compact RF systems. Simulated and measured resonances occur at 5.31/5.40 GHz (VP) and 5.27/5.33 GHz (HP), respectively. The antenna achieves –10 dB impedance bandwidths of 3.52% (VP) and 6.01% (HP), peak gains of 2.48 dBi and 2.76 dBi and axial ratios above 48 dB, confirming high polarization purity and low cross-polarization. Radiation patterns show good agreement with simulations. The proposed design offers a compact and efficient solution for applications demanding polarization reconfigurability, making it well-suited for advanced wireless communication systems.

CPW-Fed Slotted Hexagonal-Shaped Antenna with Circular Splits for Ultra Wideband Applications

2026-04-30T11:27:38+02:00

This paper presents a coplanar waveguide-fed (CPW) slotted hexagonal-shaped antenna for ultra-wideband (UWB) applications. The proposed antenna consists of a radiating patch with a standard hexagonal shape. Fractal structures are etched into the hexagonal radiating patch to increase the impedance bandwidth. These fractal structures are formed by etching five different slots into the radiating element.The antenna is designed at 3 GHz on an RO4350B substrate, with a compact footprint of 0.388 λ₀ ×0.364 λ₀ × 0.015 λ₀ at 2.98 GHz. A prototype was fabricated and tested to validate the simulation results. Measurements performed with a well-calibrated Agilent 8722ES vector network analyzer show that the proposed antenna achieves a −10 dB bandwidth covering 2.98 GHz to 11.8 GHz, corresponding to 119.35%. Radiation patterns measured in an anechoic chamber exhibit stable and well-defined characteristics across the band. Furthermore, the antenna demonstrates high efficiency and reasonable realized gain over the entire operating bandwidth. Hence, the proposed antenna is a suitable candidate for many modern UWB wireless systems.

A Compact Four-Element MIMO Antenna with DNG Metamaterial Decoupling Structure for 2.4 GHz Wi-Fi Applications

2026-03-27T08:43:52+01:00

This paper presents a small four-element MIMO antenna that can work with a frequency of 2.4 GHz and was designed such that it would maximize isolation and radiation efficiency without changing the size of the antenna. Unlike conventional designs of MIMO, which utilize the inter-element spacing of λ/2 to reduce the mutual coupling between the elements, the proposed structure has successfully demonstrated good performance with a smaller inter-element spacing of 15mm. It is worth noting that the center-to-center spacing between the antenna elements is approximately 0.39λ₀ at 2.4 GHz, which is significantly smaller than the ideal λ₀/2 separation typically required for low-coupling MIMO configurations. This reduced spacing naturally increases mutual coupling highlights the necessity of the proposed DNG-based decoupling approach. The very high electromagnetic interaction of this proximity is compensated by embedding between some pairs of selected antennas (ports 2–3 and 1–4) a double-negative (DNG) metamaterial unit cell. These cells inhibit surface-wave propagation and near-field coupling, leading to large gains in isolation and stable impedance properties. The antenna is designed on FR-4 substrate (εr = 4.3, h = 1.6 mm) and its measured performance is to be; S11 = -15.9 dB, S21 = -17.7 dB, S31 = -64.6 dB, S41 = -44.7dB at 2.4 GHz. In addition, a realized gain of 12.68 dBi, radiation efficiency of 87.5% and envelope correlation coefficient (ECC) of 0.0002. The proposed DNG-based MIMO antenna is a good alternative in the future of wireless communication systems in the Wi-Fi and IoT where it is necessary to achieve high isolation in a small physical space.

Space-Borne Circular Antenna Array Optimization with Mountain Gazelle Optimizer for Element Failure Correction

2026-04-14T09:58:35+02:00

Active phase array antennas are capable of providing high gain, wider coverage, and dynamic beam switching in a desirable direction, thus making them extremely suitable for space-borne applications such as radio astronomy, satellite communication, deep space vehicles, telemetry tracking and control communication systems. Nonetheless, there is a probability that a single or multiple antenna elements go faulty in an array, because of which the radiation pattern of the array gets distorted. The distorted radiation pattern increases the side lobe level (SLL) and reduces the directivity and hence degrades the array performance. In such space applications where it is extremely tedious, time-consuming, and costly to replace the faulty elements, a self-recoverable mechanism of failure correction can be implemented by using metaheuristic algorithms, thus mitigating any manual intervention. The enhanced SLL not only wastes the radio frequency energy but also raises potential challenges due to interference caused by receiving and transmitting the signals in an undesirable direction. In this research article, a circular antenna array (CAA) is investigated for the element failure correction of a faulty array. A mechanism of a self-recoverable array is proposed, having the capability of restoring the SLL of a failed array by recalculating and reoptimizing the array parameters with the remaining active elements within the array. Radiation pattern recovery is achievable by implementing a metaheuristic known as the mountain gazelle optimizer (MGO), and its effectiveness is validated by comparing the simulated results with other algorithms.

Double-Layer Metamaterial Microwave Sensor for Olive Oil Quality

2026-03-24T10:37:20+01:00

This paper presents a double-layer metamaterial microwave sensor for the selective detection of water adulteration in virgin olive oil. The proposed design employs an E-comb resonator configuration that enhances electric-field confinement and improves interaction between the resonator and the material under test compared with conventional single-layer resonant sensors. The sensor was first characterized through broadband full-wave electromagnetic simulations using CST and HFSS over the 1–15 GHz frequency range, followed by fabrication and experimental validation using vector network analyzer (VNA) measurements. Experimental results demonstrate a strong and selective response to polar contaminants, exhibiting a resonance frequency shift of approximately 0.5 GHz for only 5 % (v/v) water adulteration. In contrast, non-polar adulterants such as sunflower oil produce negligible resonance variation. The dielectric properties of the samples were extracted using the Cole–Cole relaxation model and showed good agreement with reported literature values, confirming the reliability of the proposed sensing mechanism. Furthermore, a quality factor-based index is introduced as a quantitative indicator for assessing oil purity. The proposed approach provides a non-destructive, real-time sensing technique with strong potential for automated quality control in the olive oil industry, using a compact and cost-effective microwave sensing platform.

Design and Characterization of a High sensitivity 2.45 GHz E-Field Probe for Precise Electromagnetic Measurements

2026-03-24T07:21:30+01:00

This work presents the design, simulation, and experimental validation of a novel electric-field (E-field) probe operating at 2.45 GHz, developed specifically for electromagnetic field measurements and calibration applications. The proposed probe incorporates a compact cylindrical dipole architecture, enhanced with a low-loss Teflon dielectric spacer to ensure structural stability and minimal field disturbance. A high-speed Schottky diode rectification circuit is employed to enable efficient detection of weak electric fields while maintaining a reliable response over the operating bandwidth. The resulting probe achieves good impedance matching, with S₁₁ < –16 dB at 2.45 GHz, and offers a usable bandwidth of approximately 100 MHz around the target frequency. Performance evaluation demonstrates high sensitivity (10 mV/m), strong linearity (R²= 0.996), and low measurement uncertainty (±2.8 dB). When compared with widely used commercial probes, such as the NARDA NBM-50, the developed design exhibits comparable performance in terms of sensitivity and stability, making it suitable for EMC and dosimetry applications.

Dual-Resonance U-Shaped Wearable Antenna with T-Slot Ground for On-Body Biomedical Devices

2025-07-09T11:07:12+02:00

This study introduces a miniaturized and adaptable dual-band textile antenna, meticulously designed for implementation in wearable biomedical systems. It functions at 2.45 GHz and 5.8 GHz, covering the ISM (Industrial, Scientific, and Medical) frequency ranges. The antenna features a U-shaped patch with a T-shaped slotted ground plane, built from denim fabric (εr = 1.68) and ShieldIt Super conductive material. Following several design optimizations—such as via placement, curvature conformity, and slot tuning—the final prototype shows reliable impedance matching (S11 < -10 dB across both bands) and consistent radiation performance, validated using CST and COMSOL simulations. The antenna maintains dependable performance on the human body, with SAR levels staying within safe exposure thresholds (1.18 W/kg at 2.45 GHz and 1.44 W/kg at 5.8 GHz). Although radiation efficiency drops are observed when worn (approximately -10.5 dB and -15.6 dB at 2.45 GHz and 5.8 GHz respectively) due to body absorption, the radiation pattern remains directed and functional. These characteristics make the design well-suited for body-worn communication systems used in healthcare monitoring, fitness tracking, and military contexts. This flexible antenna meets safety and comfort requirements, offering a viable solution for WLAN/WBAN implementations in wearable technology.

Flexible Multi-wideband Wearable Antenna for Preliminary Evaluation of Tumour Detection in Breast Phantom Model

2025-09-02T11:05:38+02:00

The growing demand for non-invasive and wearable breast cancer diagnostic tools has driven the development of flexible and wearable antennas for microwave imaging. This study presents a flexible multi-wideband wearable antenna designed for breast tumour detection, with targeted operation at the 2.4 GHz Industrial, Scientific, and Medical (ISM) band which fabricated on a breathable cotton substrate with a 0.035 mm copper layer, the antenna measures 83 × 60 × 1.52 mm³ and is backed by a 2×3 Artificial Magnetic Conductor (AMC) array to enhance the gain whilst suppressing back radiation. Simulations and measurements are conducted in free space and on a realistic three-layer breast phantom consisting of skin, fat and glandular which is properly characterise in terms of electrical parameter has successfully, demonstrate a directional radiation, strong resonance at 2.4 GHz and wideband performance above 5.04 GHz. The antenna exhibits insensitivity to bending angle up to 60° and exhibits a low Specific Absorption Rate (SAR) value of 0.23 W/kg (10 g), ensuring safety compliance for wearable use to human skin proximity. While the current design supports tumour detection with varying sizes between 2–10 mm, future work will focus on extending the bandwidth below 5 GHz and miniaturizing the structure for enhanced early-stage diagnosis.

Global Minimality in Constrained Inverse Source Problems for Metamaterials

2025-04-15T19:07:49+02:00

Global minimality, boundedness, and uniqueness are established for a general, physically motivated class of inverse source problems in non-homogeneous electromagnetic media with generalized constitutive parameters. The existence of a solution was addressed earlier. The radiating source, represented by the current density, was reconstructed earlier by minimizing its L²-norm constrained to produce a prescribed radiated field while ensuring vanishing reactive power. Using the L²-norm allows for an analytically tractable measure of the physical resources of the source, while the reactive power constraint maximizes transmitted power. Numerical study suggests that sources within active metamaterial substrates can have remarkable tuning behaviors. Tuning stability can be achieved along specific permittivity and permeability curves on zero-reactive power plots. Each permittivity or permeability value can correspond to a discrete set of dual parameter values that enable effective tuning. The tuning characteristics observed suggest that double-positive (DPS) and double-negative (DNG) substrates are more favorable for tuning than single-negative (SNG) materials, possibly due to interactions dominant in DPS and DNG media. These results fill an analytical gap in the solution of a problem that is both intriguing and challenging due to its general formulation, which requires minimizing an objective functional with nonconvex functional constraints on an unbounded domain. They also offer numerical insights that may have implications for the design and optimization of sources in complex media, which is a topic of significant current interest.

Ultra-Compacted Antenna-based Capsule Endoscope in the ISM Band

2025-07-07T10:44:10+02:00

This article presents a proposal for the miniature implantable antenna of a microstrip patch that covers ISM bands (2400–2483.5 MHz) for deep-tissue implantation with a volume of just 0.3 mm³. The proposed antenna is the smallest and lightest antenna manufactured for wireless capsule endoscopy. The antenna can be integrated with an imaging sensor, electronic components, and a battery. The proposed Microstrip Patch Antenna MPA shows a 483 MHz wider bandwidth at 2483.5 MHz; Beef muscles were used to validate the antenna's performance experimentally. The safety issues are assessed to examine the performance of the proposed antenna incorporated in an endoscopy capsule device by considering the specific absorption rate (SAR).