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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]

This article presents an in-depth investigation of wearable microwave antenna sensors (MASs) used for vital sign detection (VSD) and lung water level (LWL) monitoring. The study looked at two different types of MASs, narrowband (NB) and ultra-wideband (UWB), to decide which one was better. Unlike recent wearable respiratory sensors, these antennas are simple in design, low-profile, and affordable. The narrowband sensor employs an offset-feed microstrip transmission line, which has a bandwidth of 240 MHz at −10 dB reflection coefficient for the textile substrate. The UWB microwave sensor uses a CPW-fed line to excite an unbalanced U-shaped radiator, offering an extended simulated operating bandwidth from 1.5 to 10 GHz with impedance matching ≤−10 dB. Both types of microwave sensors are designed on a flexible RO 3003 substrate and textile conductive fabric attached to a cotton substrate. The specific absorption rate (SAR) of the sensors is measured at different resonant frequencies on 1 g and 10 g of tissue, according to the IEEE C95.3 standard, and both sensors meet the standard limit of 1.6 W/kg and 2 W/kg, respectively. A simple peak-detection algorithm is used to demonstrate high accuracy in the detection of respiration, heartbeat, and lung water content. Based on the experimental results on a child and an adult volunteer, it can be concluded that UWB MASs offer superior performance when compared to NB sensors. [ABSTRACT FROM AUTHOR]

This paper presents a new radar sensor configuration of a planar grid antenna array (PGAA) for automotive ultra-wideband (UWB) radar applications. For system realisation, the MIMO concept is adopted. The proposed antenna is designed to operate over the 24 GHz frequency band. It is based on split-ring resonator (SRR) elements to enhance the operating bandwidth and increase the antenna gain, leading to a better-performing radar system. The PGAA consists of thirty-one radiating elements, in which each element excitation is obtained using a common transmission line centre fed by a 50 Ω coaxial probe. By introducing a superstrate dielectric layer at a distance of λ / 2 from the top of the antenna array, the PGAA gain and impedance bandwidth are further improved. The gain is improved by 2.7 dB to reach 16.5 dBi at 24 GHz, and the impedance bandwidth is enhanced to 9.3 GHz (37.7%). The measured impedance bandwidth of the proposed antenna array ranges from 20 GHz to 29.3 GHz for a reflection coefficient ( S 11 ) of less than −10 dB. The proposed antenna is validated for automotive applications. [ABSTRACT FROM AUTHOR]

This research presents an innovative hexagonal dielectric resonator antenna (DRA) with circular polarization and multi-input multi-output (MIMO) characteristics. The DRA consists of two dielectric layers, providing a fractional bandwidth of 9% (4.05 to 4.38 GHz).The antenna ground plane features has an S-shape slot, when coupled with a 50 Ω microstrip line, enables the generation of right-hand circular polarization. To enhance performance, the feed line includes a bandpass filter with a semi-elliptical form, resulting in outstanding selectivity. The proposed design demonstrates a gain of 9.2 dBi and encompasses a 3 dB axial ratio bandwidth of 9.29%. The proposed design is fabricated, and a comparison is made between the simulated and the measured results. Furthermore, the study introduces a MIMO antenna system by combining two filter arrays. The MIMO antenna demonstrates a reasonable port isolation of >25 dB across the operating band with acceptable MIMO parameters. [ABSTRACT FROM AUTHOR]

This paper presents a unique structure of a dual-band microstrip bandpass filter (BPF) that works at 1.25 GHz, 1.9 GHz for global positioning systems (GPS) and TV broadcast auxiliary service applications, respectively. The proposed BPF provides compactness, small fractional bandwidth (FBW), small frequency separation, and low IL. The prospective filter is constructed employing broadside-coupling techniques to achieve low insertion loss (IL). The feeding structure is accomplished utilizing a 50 Ω co-planar waveguide (CPW) scheme due to its low loss characteristics. The small 3-dB FBW is accomplished by inserting four transmission zeros (TZs). The size of the overall structure, including I/O transmission lines, is 34.9 × 23.5 mm2. The measured and simulated results fit well with each other and show an IL of 0.77 dB and 0.5 dB, and FBW of 7.6% and 8.4% at 1.25 GHz and 1.9 GHz, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel compact design of a low pass filter (LPF) with a vast rejection band, low insertion loss (IL), and sharp roll-off. The prospective LPF is fed using a modified E-shape microstrip line to improve the higher frequencies rejection band. Two ring slots are engraved in the ground plane and linked to the feeding line through metallic via to provide further improvement in the rejection band. Three coupled stepped impedance resonators (SIRs) are jointed between the I/O ports to improve the filter roll-off. The proposed LPF provides cutoff frequency at 2.8 GHz, and stopband ranges from 3.2 to 20 GHz with an attenuation level less than −20 dB. The lumped RLC circuit model of the proposed LPF is introduced and confirmed by simulation and theory using Keysight Advanced Design System (ADS). This LPF is designed and fabricated on Rogers RT3006 with compact size 13 mm × 8.2 mm. The measurements of the proposed LPF are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

This manuscript introduces orthogonally polarized quad-element multi-input multi-output (MIMO) antenna with improved isolation. The proposed design of a miniaturized volume of 43 × 43 × 1.5 mm3 covers vast impedance bandwidth more than 17.85 GHz commences at 2.15 GHz to more than 20 GHz, corresponding to reflection coefficient below – 10 dB. A quad-port low-pass filter (LPF) with a very wide rejection band and low cutoff frequency is suggested as a decoupling structure to boost the isolation to more than 20 dB across most of the bandwidth. Equivalent circuit model is scrutinized to investigate the enactment of the decoupling-structure. The MIMO antenna performing satisfies UWB requirements of relatively omnidirectional radiation patterns and stable radiation characteristics with an average gain 5 dBi. Envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC) are analyzed to show the applicability of the proposed antenna to the short-range communications. Both simulated and fabricated results demonstrate good agreement. [ABSTRACT FROM AUTHOR]

The paper describes the fabrication of new artificial material through a compression-molding technique. Four composites PVDF/BaFe 11·7 Al 0·3 O 19 (HF) were produced at various PVDF concentrations (5%, 10%, 15%, and 20%), wt.%. The produced samples were examined by an X-Ray diffraction (XRD) analysis and Fourier transform infrared (FTIR) spectroscopy. The examination proved that the produced samples formed the required hexaferrite and its composites. The magnetic and electrical characteristics of all the samples were examined by using a vibrating sample magnetometer (VSM) and a vector network analyzer. The samples were tested for electromagnetic shielding and Antenna application at a frequency of 2.45 GHz. The study of the dielectric properties suggests that 10% PVDF is the optimized ratio composite, which can provide a perfect opportunity for improving the Antenna gain and efficiency. The shielding efficiency due to the reflection of 10% PVDF composite is 32 dB. Therefore, PVDF/HF composites can be promising candidates for practical applications such as high frequency, electromagnetic interference (EMI) suppressor, electronic, communication, and future gigahertz antenna applications. [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]

The research comprehensively analyzes the structural, electrical, and electrodynamic characteristics of Ba 0.7 Sr 0.3 TiO 3 nanoparticles synthesized using a sol-gel approach. The formation of a tetragonal perovskite phase and the nano-crystalline nature have been confirmed using X-ray diffraction (XRD) analysis. Fourier transform infrared (FTIR) spectroscopy has been employed to identify characteristic absorption bands correlated with the crystal lattice vibrations of Ba 0.7 Sr 0.3 TiO 3. The sample's morphology has been examined using scanning electron microscopy (SEM), revealing a relatively dense and homogeneous composition composed of small spherical particles. The electrical properties of Ba 0.7 Sr 0.3 TiO 3 nanoparticles have also been investigated using a ferroelectric measurement technique. The soft electric hysteresis loop with a small coercive field value makes the sample suitable for photovoltaic applications. Finally, a compact dielectric resonator antenna (DRA) based on Ba 0.7 Sr 0.3 TiO 3 nanoparticles has been designed and characterized. The designed DRA demonstrates good impedance matching, broadside radiation pattern, and high antenna gain and efficiency at the frequency band of 5.6–6.15 GHz, making it suitable for sub-6 GHz (5 G) applications. • Ba 0.7 Sr 0.3 TiO 3 nanoparticles were produced using a tartaric precursor technique. • Nanoparticles were confirmed for perovskite structure and uniformity via XRD, FTIR, and SEM. • Ba 0.7 Sr 0.3 TiO 3 nanoparticle dielectric properties were tested for 5 G applications. • A compact antenna design using Ba 0.7 Sr 0.3 TiO 3 was proposed and evaluated. • Proposed antenna showed high gain, efficiency, and potential for mm-wave 5 G usage. [ABSTRACT FROM AUTHOR]

This paper exhibits a high-gain, low-profile dipole antenna array (DAA) for 5G applications. The dipole element has a semi-triangular shape to realize a simple input impedance regime. To reduce the overall antenna size, a substrate integrated cavity (SIC) is adopted as a power splitter feeding network. The transition between the SIC and the antenna element is achieved by a grounded coplanar waveguide (GCPW) to increase the degree of freedom of impedance matching. Epsilon-near-zero (ENZ) metamaterial technique is exploited for gain enhancement. The ENZ metamaterial unit cells of meander shape are placed in front of each dipole perpendicularly to guide the radiated power into the broadside direction. The prospective antenna has an overall size of 2.58 λ g 3 and operates from 28.5 GHz up to 30.5 GHz. The gain is improved by 5 dB compared to that of the antenna without ENZ unit cells, reaching 11 dBi at the center frequency of 29.5 GHz. Measured and simulated results show a reasonable agreement. [ABSTRACT FROM AUTHOR]