ABSTRACT
A miniaturized, multi-band, four-port wearable Multiple Input Multiple Output (MIMO) antenna is proposed, which contains a leaky wave textile antenna (LWTA) on denim (εr = 1.6, tanδ = 0.006) as substrate and Shieldit Super Fabric as conductor textile. The concept in this work involves incorporating the metal and plastic zipper into the garment to function as an antenna worn on the body. Simulations and measurements have been conducted to explore this idea. The LWTA has dimensions of 40 × 30 × 1 mm³. Every two ports are separated by a zipper with two different kinds of materials: Acetal Polymer Plastic (APP) and 90 % brass to improve the isolation, gain, and Impedance bandwidth. The antenna operates in the frequency ranges covering the L, C, S, and X bands. Additionally, diversity performance is evaluated using the Envelope Correlation Coefficient (ECC) and diversity gain (DG). Simulation and measurement findings agree well, with a maximum gain of 12.15 dBi, low Specific Absorption Rate (SAR) based on the standards, DG greater than 9.65 dB, circular polarization (CP), and strong isolation (<-23 dB) between each port. Since the antenna's characteristics do not change significantly under bending and when the zipper is opened, the proposed antenna is a viable candidate for body-centric wireless communications on the battlefield. For example, it can facilitate communication covering wireless local area network (WLAN) and fifth-generation (5G) communications.
ABSTRACT
In this study, at two different fifth generation (5G) low-frequency bands (3.7-4.2 GHz and 5.975-7.125 GHz) and based on nonuniform transmission lines (NTLs) theory, a compact three-quarter-wave resonators interdigital bandpass filter (IBPF) is analyzed, designed, and fabricated. The compact proposed filter is considered as a good candidate for reconfigurable 5G low-frequency bands and ultrawide band (UWB) antenna, which will reduce the size of the final RF communication system. Firstly, a uniform transmission line (UTL) IBPF at these two bands is designed and tested; then the NTL concept is applied for compactness. For both UTL and NTL IBPFs, different parametric studies are performed for optimization. At the first frequency band, size reductions of 16.88% and 16.83% are achieved in the first (symmetrical to the third resonator) and second λ/4 resonator of UTL IBPF, respectively, with up to 36.6% reduction in the total area. However, 16.46% and 16.33% size reductions are obtained in the first (symmetrical to the third resonator) and second λ/4 resonator, respectively, at the second frequency band with a 40.53% reduction in the whole circuit area. The performance of the proposed NTL IBPF is compared with the UTL IBPF. The measured reflection coefficient of the proposed NTL IBPF, S11, appears to be less than -10.53 dB and -11.27 dB through 3.7-4.25 GHz and 5.94-7.67 GHz, respectively. However, the transmission coefficient, S12 is around -0.86 dB and-1.7 dB at the center frequencies, fc = 3.98 GHz and 6.81 GHz, respectively. In this study, simulations are carried out using high-frequency structure simulator (HFSS) software based on the finite element method (FEM). The validity of the proposed theoretical schematic of this filter is proved by design simulations and measured results of its prototype.
ABSTRACT
Theoretical investigations are carried out to study hybrid SPP wave propagation along the Chiral-Graphene-Metal (CGM) interface. The Kubo formulism is used for the physical modeling of single-layer graphene and the impedance boundary conditions approach is applied at the CGM interface to compute the dispersion relationship for hybrid SPP waves. It is demonstrated that the chirality (ξ) and chemical potential (µc) parameters can be used to modulate the resonance surface plasmon frequencies of the upper and lower propagating modes. Furthermore, the propagation bandgap between the upper and the lower modes can be tuned by changing the chirality parameter. The effect of the chemical potential (µc)and the relaxation time (τ) on the normalized propagation constant, propagation length, and the effective refractive index is studied. The present work may have potential applications in optical and chiral sensing in the terahertz frequency range.
ABSTRACT
This paper presents theoretical investigation of the electromagnetic wave tunneling and anomalous transmission around the trapped modes in a pseudochiral omega slab. The dispersion relation, the conditions of the trapped modes, and the evanescent wave coupling and tunneling in two different reciprocal pseudochiral omega slab structures are derived. The Berreman's matrix method is applied to obtain the transmission coefficients across the pseudochiral omega slab. When the structure is perturbed, a resonance phenomenon is detected around the trapped modes. This resonance results in transmission anomalies (total transmission and total reflection) and dramatic field amplifications around the trapped modes. The number of the discrete trapped modes and then the resonance frequencies are prescribed by the parameters of the pseudochiral omega slab such as the value of the omega parameter and its orientation and the slab thickness.
