Search

This article introduces a novel microstrip slot antenna array (SAA) configuration for radar applications. The proposed antenna is specifically designed for operation in the K-band, spanning from 23 to 24.3 GHz. The antenna structure comprises two substrates: the feed network and ground plane are on the bottom substrate, and the radiating slots are on the top layer of the first substrate. The incorporation of a unique grid feed configuration, featuring 50 Ohm center excitation for the first time, improves the feed mechanism of the microstrip SAA. This innovation contributes to achieving a compact size and high gain. To enhance the side lobe level, the design incorporates a substrate-integrated waveguide-backed cavity, which significantly reduces surface waves. The SAA consists of 25 radiating elements with a gain of 14 dBi. In the elevation and azimuth planes, the half-power beamwidths are measured at 12.1° and 69.1°, respectively. The proposed antenna array's measured impedance bandwidth ranges from 23.15 to 24.75 GHz, guaranteeing a reflection coefficient (S11) of less than − 10 dB. The suggested antenna's applicability for automotive multi-input multi-output radar has been validated. [ABSTRACT FROM AUTHOR]

In this paper, a textile two-port multi-input multi-output (MIMO) half-circle antenna with corrugated borders is designed and fully analyzed for nearfield ultra-wideband biomedical diagnostic applications. The orthogonal polarization technique is introduced for mutual coupling reduction, signal quality, and imaging accuracy improvement. A low pass filter with significant out-of-band rejection is inserted between the two MIMO structural elements to improve the isolation from element to element. For simple system integration, A 50 ohms feed coplanar waveguide is suggested for each element. The entire antenna is constructed using textile materials, with the radiating element composed of conductor fabric. The substrate, on the other hand, is crafted from cotton material which possesses a relative permittivity of and a tan δ value of 0.025. The size of each antenna element has low-profile dimensions of 40 × 40 × 0.3 mm 3 . The measured results obtained demonstrate an extremely broad bandwidth extends from 2.5 GHz to 12 GHz. Omnidirectional radiation pattern is obtained, with 6 dBi maximum gain and 96% efficiency. In order to ensure flexibility, a range of bending conditions were analyzed, and the durability was assessed through wash ability testing. Safety was confirmed by measuring the specific absorption rate. Furthermore, time domain and MIMO performance assessments were performed to ensure its suitability for imaging systems. [ABSTRACT FROM AUTHOR]

A design of high sensitivity Vivaldi antenna is introduced for detecting the low sugar and salt concentrations in water. The reason for selecting the Vivaldi antenna configuration is to provide two desired features; ultra-wideband and a high directivity so the surrounding clutter effect can be minimized. The prospective antenna embraces the ultra-wideband from 4 to 11 GHz. Two techniques are exploited to improve the antenna detectability; epsilon-near-zero (ENZ) metamaterial and antenna aperture amending. The ENZ metamaterial is very sensitive to the permittivity of the substrate, so any loading effect can easily alter the electric field distribution and hence affect the antenna phase properties. The aperture amending is used to improve substrate-air matching. An equivalent circuit model is scrutinized for further emphasis of the ENZ metamaterial operation, showing good agreement with EM simulation results. In terms of phase variation, the designed antenna is employed to sense sugar and salt in water. The amount of sugar and salt affects the material characteristics of the solution and, as a result, the reflected phases. Practical observations reveal that when the sugar and salt contents in the liquid increase, the phase falls. At 5 GHz the difference between the highest and lowest sugar concentrations is about 3° in the sugar case and 5° in the salt case, but at 8 GHz, the phase difference is about 30o in the sugar case and about 50° in the salt case. The sensitivity can be increased by operating at a higher frequency since the proposed antenna can detect very low levels (1%) of salt and sugar concentrations. The time-domain analysis is discussed, revealing low distortion of received pulses. [ABSTRACT FROM AUTHOR]

This study provides a comprehensive synthesis and meticulous examination of barium hexaferrite (BHF), barium titanate (BT), and their respective nanocomposites, unveiling their potential in specific applications, including electromagnetic interference shielding. The successful formation of BHF and BT was confirmed through Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses, revealing distinct absorption peaks indicative of the tetragonal configuration of BT and the BHF's crystal structure. Scanning electron microscopy (SEM) depicted the unique morphologies and dispersions of particles in the synthesized nanocomposites, with BHF appearing larger (~ 82 nm) than BT (~ 50 nm). Vibrating sample magnetometry (VSM) findings exhibited an increased resistance to demagnetization with the addition of BT, despite a slight decline at 75% BT concentration due to the non-magnetic nature of BT dominating. Uniquely, the study presented an in-depth analysis of the composites' conductivity, detailing their non-monotonic behavior across a frequency range. A detailed investigation into the complex permittivity and permeability revealed the composite's enhanced ability to store and dissipate both electrical and magnetic energy, a function influenced by the concentrations of BT and BHF. A pivotal highlight of this research was the significant achievement of a reflection loss (RL) value of − 45 dB at 9.3 GHz for the composite with 75% BHF, suggesting the composite's potential as an effective microwave absorber. This study represents a significant step toward designing and optimizing nanocomposites for specific applications in the realm of electromagnetic materials. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the electromagnetic (EM) properties of hybrid materials made from polypyrrole (PPy) and barium hexaferrite (HF) for possible use in electromagnetic interference (EMI) shielding applications. X-ray diffraction and Fourier-transform infrared spectroscopy methods were used to confirm the presence of PPy and HF phases inside the hybrid structure. A scanning electron microscope analysis revealed that the HF particles were evenly dispersed throughout the PPy structure. The composites' dielectric and magnetic attributes were evaluated across a spectrum of frequencies, with the highest values observed in the PPy specimen. Adding HF to the PPy matrix altered the dielectric and magnetic properties of the composite, with the percentage of HF in the composite influencing its dominance over these properties. It was determined that a 25% HF content produced the most stable and efficient composite for absorbing EM waves in the X-band. This study demonstrates the potential of conductive polymer composites for EMI shielding applications, with advantages, such as improved EMI shielding, lightweight, flexibility, corrosion resistance, and tailored properties. The novelty lies in optimizing the composition of the PPy/HF composite and the characterization of its EM properties, providing insights into the design of more efficient EMI shielding materials. [ABSTRACT FROM AUTHOR]