Kai Zhang

Microwave sensing techniques have shown strong potential for detecting skull fractures due to their non-ionizing nature and suitability for compact, low-cost, and portable point-of-care applications. This study investigates a wideband circularly polarized antenna integrated with a metasurface reflector for fracture detection and evaluates the impact of reducing its lateral dimensions by 30% on performance. Two antenna configurations, the original and a scaled variant, were analyzed using simulations with a multilayer head tissue model containing 1 mm and 3 mm linear skull fractures. The results demonstrate that miniaturization can be achieved while preserving fracture detectability across multiple antenna–skin distances, supporting the development of compact microwave-based diagnostic systems.

This paper proposes a dual-band, polarization-reconfigurable glass-mounted transparent antenna for Vehicle-to-everything (V2X) communications. The antenna is etched on a polyester (PET) with a thickness of 0.1 mm using indium-doped tin oxide (ITO) transparent conductive film with a thickness of 0.125 mm, achieving an overall light transmittance of 84.2%. The antenna structure includes two circular monopole patches and a frame surrounding the monopole patch. The circular monopole patches are coupled and fed by T-type feedlines. Four diode switches are soldered onto the ITO surface using conductive silver paste to control the polarization of the antenna. The biasing of the diodes switches the antenna in three different polarization states: linear polarization, left-handed circular polarization and right-handed circular polarization. Simulations and measurements of the antenna were conducted on a vehicular glass. The overall size of the antenna is 96.7×68.9 mm², with a total thickness of 0.225 mm, a linear polarization matching bandwidth of 2.3 GHz-6.5 GHz, and a circular polarization bandwidth of 5.4-6.4 GHz (15%) in the 2.5 GHz and 5.8 GHz dual-frequency operation. Finally, the ground-to-air communication link is studied using transmission coefficient between the glass-mounted (proposed) antenna and an unmanned aerial vehicle (UAV) operating with different attitudes. Results indicate link improvements due to the polarization reconfigurability offered by the proposed antenna.

This paper presents a novel multi-band polarization diversity watch antenna designed for smartwatch applications. The proposed antenna adopts the loop multimode resonant technology and the odd-even mode feeding technology. By exciting the first three modes of the loop of the watch frame, the effective resonance at 2.5 GHz, 4.4 GHz and 5.8 GHz are achieved. The polarization diversity technology on the commonaperture is realized respectively through the odd-even mode feeding technology. Therefore, the orthogonal current directions are generated within the watch frame, and the watch strap is efficiently used for the diversity at 0.82 GHz, for n5, n41, n79, and industrial scientific medical (ISM) band applications. Simulations and measurements from the watch antenna showed excellent performance in terms of reflection, far field, and polarization diversity. Besides that, additional evaluation on the human wrist also indicates a low specific absorption ratio (SAR) and envelop correlation coefficient (ECC) levels. To the best of our knowledge, such multi-band diversity antenna with favorable characteristics designed for watches are not evident in other state-of-the-art literature.

Abstract-This paper presents a novel approach to design a compact wideband metasurface (MS) antenna with multi-mode resonance for Internet of Things (IoT) applications. The proposed antenna incorporates an aperiodic MS structure and an aperture-coupled feeding structure, operating within the frequency range of 2.15 GHz to 3.84 GHz, covering n7, n38, n41, and n78 frequency bands. Initially, an MS resonant antenna is designed based on the left-handed dispersion characteristics of metamaterials, generating TM _(-10) and TM _(-20) modes, which are then merged. Subsequently, the unit structure is adjusted to transform the antenna into an aperiodic structure, resulting in the generation of the TM _(-21) mode. The working frequency is from 2.15 GHz to 3.84 GHz with 56 % fractional bandwidth. The three negative resonant modes are cleverly combined to enable broadside patterns with a maximum realized gain of 4.22 dBi. Besides that, its simultaneous wideband operation and miniaturized form factor makes this design unique compared to previously reported literature.

This article provides a comprehensive review of methods for enhancing antenna gain, using existing antenna solutions as examples by incorporating reflector plates for gain improvement. However, the article has the following issues: (1) Lack of innova...

This paper presents a metasurface (MS)-based wideband wearable circularly polarized (CP) antenna to communicate with in-body devices. The antenna consists of a crossed dipole, an MS plane and a CP feeding network. The feed network generates a quasi-90° phase delay between each adjacent arm of the crossed dipole. This produces CP radiation and reduces polarization mismatch between the telemetry antenna and the implantable antenna. The MS consisting of a 5×5 unit cell array functions as a reflector for the crossed dipole to improve forward radiation while maintaining a low profile structure. This is by designing the unit cells with a near-zero phase reflection over the operating band. To enable conformity with on-body usage, the antenna is designed fully using flexible materials. Textile conductive elements are embedded into a PDMS substrate. It is sized at 106×106×5mm3 (1.24λ×1.24λ×0.05λ at 3.5 GHz). Results indicated a -10 dB impedance bandwidth from from 2.25 to 6 GHz (90%). The 3-dB axial ratio bandwidth is from 2.9 to 4.95 GHz (52%), with a maximum on-body gain of - 10.5 dBi. Finally, the specific absorption rate (SAR) assessment of the antenna indicated values far lower than the limits of the FCC.

Wearable antennas are increasingly being miniaturized and broadened in terms of bandwidth due to the increasing need for multi-standard biomedical communication and imaging capabilities. In this paper, a novel, compact and wideband button-like antenna based on composite right/left-handed transmission line (CRLH TL) theory is proposed. The antenna consists of a compact FR-4 PCB as its substrate and a semi-rigid coaxial cable is used as feed. The button dish has a dimension of π × 6 × 6 × 1.5 mm ³ (π × 0.11 × 0.11 × 0.027λ ³ ) at 5.5 GHz. The ring-shaped radiator includes two end-to-end CRLH TL unit elements on top of the substrate, which is excited by coupling with a concentric circular patch. The zeroth-order resonance (ZOR) mode and +1st order mode are generated and combined to achieve an ultra-wideband operation from 5.15 GHz to 9.35 GHz (58% fractional bandwidth). Furthermore, a spiral structure is employed in this design to decrease the negative effects of the ground plane, resulting in a high gain and a low specific absorption rate (SAR). To our best knowledge, this is the first button ZOR antenna based on CRLH TL structure designed for wearable applications with such wide bandwidth besides acceptable gain and compactness levels.