This paper presents an online noise source impedance extraction method based on network analyzer. Firstly, the composition scheme of the measurement method is given, the equivalent circuit model of the measurement system established, and the port structure of the equivalent circuit analyzed. Secondly, two known standard resistances are used to calibrate the measuring system and connecting wires. Finally, the passive device and DC/DC converter are used as the equipment to be tested, and the measurement results are compared with those of other methods and impedance analyzer. The comparison results show that the measurement method has high measurement accuracy and good temperature sensitivity.

Enhancing the electromagnetic absorption properties of pozzolanic cement provides scope for low cost realisation of frequency screened buildings. Electromagnetic wave attenuation attribute of conductive filler inclusions determines the absorption properties of filler loaded cement mortar. A transmission line based rapid measurement technique for the speedy estimate of microwave attenuation of conductive fillers is presented, providing quick approximates of cement mortar thickness for realizing customized absorption loss. Ash from three units of steel plant including EAF, AoD, and ARS units is investigated. Coaxial transmission line supports TEM propagation, hence is well suited for estimating plane wave characteristics. Ash filled coaxial transmission structures are subjected to scattering matrix measurements in the frequency range 800 MHz-4 GHz. Plane wave attenuation is estimated from the scattering matrix transfer coefficient (S₂₁). Ashes guarantee minimum 10 dB/m attenuation in the specified frequency range with ash from ARS unit providing loss over 50 dB/m. The database of customized cement mortar (composite) thickness for realizing varied absorption losses, incorporating ARS ash, is projected. The presented technique reduces the requirement of anechoic chambers, broad band horns, and liability of prototyping large mortar samples (all frequency dependent), for estimating shielding properties of conductive filler loaded cement mortar composites, over wide band. Cement panels with customized absorption loss provide scope as low cost solution for managing device co-location issues encountered in evaluating EMI/EMC concerns is future IoT based systems.

In this article, a novel idea of designing a graphene based planar plasmonic patch antenna for terahertz wireless applications with detailed analysis is proposed. Based on the Surface Plasmon Polariton Waves (SPP) behaviour in graphene, a novel wideband planar graphene-based patch antenna is investigated here. As graphene with its wondered properties supports SPP in much lower infrared frequencies unlike the noble metals such as gold and Nickle which support SPP at much higher frequencies, the proposed planar antenna works on THz gap (0.1-10 THz) by covering a range of frequencies from 0.1 THz and goes beyond 10 THz, thus covering the whole THz gap. The proposed antenna is a simple planar structure with overall size of 31.8 x 6.4 μm² having a Silicon with a relative permittivity (ε_r) of 11.9 used as a substrate material, and simple plane wave is used for excitation. Furthermore, radiating material comprises single layer graphene and copper with a partial ground of copper material, and for comparison purpose, only graphene layer as a radiating material is also analysed. Single layer graphene conductivity having chemical potential of 0.4 ev, relaxation time of 0.6 ρs, and a temperature of 298 K is discussed. Parametric analysis for getting optimum results is also studied. The unity peak absorption of above 98% is observed throughout the resonating frequency range. The proposed design is numerically simulated in CST MWS v2020, and other parameters results, such as unity peak absorption and surface current, are also discussed.

This paper presents a miniaturized antenna-based wearable self-powered wireless systems; the proposed study identifies the possibility to compact a flexible Solant-Rectenna integrated to low energy devices. The proposed system uses the obtained DC currents from RF rectifier and solar panel to recharge batteries. A low-profile Hilbert-shaped metamaterial (MTM) array forming a rectangular patch is conducted to minimize the shadowing effects to 13.3% on the solar panel area. Nevertheless, an Electromagnetic Bandgap (EBG) square pads array is introduced as defects on the ground plane to remove the negative effects, in terms of losses, of the solar panel bus-bar on the antenna performance. Moreover, the proposed EBG ground plane is utilized to isolate the human body from the undesired electromagnetic radiation leakage in addition to minimize the antenna impedance mismatch caused by the proximity to human tissues. For this, the Specific Absorption Rate (SAR) is analysed numerically to assess the feasibility of the proposed EBG layer. The antenna expresses a frequency bandwidth, S₁₁ < -10 dB, from 0.8 GHz up to 10 GHz; moreover, the EBG inclusions increase the front to back ratio to provide the gains of -10 dBi, -4 dBi, 0 dBi at 0.915 GHz, 1.88 GHz, and 2.45 GHz, respectively. Moreover, a SAR reduction is achieved up to 64% down after the EBG layer introduction. In addition, the antenna distortion effect in terms of group delay (G_d) after 3.1 GHz up to 10 GHz is tested; the maximum variation is found to be less than 1ns which shows a linear phase response with distortionless waveforms. Such a feature is found very suitable for UWB applications in modern wireless systems. The antenna performance improvement after introducing the proposed EBG defects is validated experimentally and numerically. The solar panel I-V characteristics are measured after the antenna structure introduction. Next, the solant RF port is connected to a rectifier circuit to realize the rectenna performance port that collects the RF energy at three bands in terms of efficiency spectra. Finally, it is proofed that the proposed Solant-Rectenna offers an excellent, compacted, and flexible candidate for the wearable self-powered devices at different bands.

In this article, the diffraction of E-polarized electromagnetic plane waves by a double half-plane structure is taken into account. The shift of the upper half-plane through the horizontal axis for different wavenumber and boundary conditions are considered. On the double half-plane structure, fractional boundary conditions are required on the half-plane surfaces. The half-planes are parallel to each other with a variable shift in distance and location. The formulation of the problem is given where the boundary condition is explained, and the integral equations for each half-plane are obtained by using fractional calculus and Fourier Transform techniques. Then, for numerical calculations, the induced current on each half-plane is expressed as the summation of Laguerre polynomials. This leads to having a system of linear algebraic equations needed to be solved. The numerical results show that the shift and the distance between the half-planes give a very important effect on the field values inside and outside the guiding structure. The results are compared and analyzed with Method of Moment and previous results.

The capacitance matrix relates potentials and charges on a system of conductors. We review and rigorously generalize its properties, block-diagonal structure and inequalities, deduced from the geometry of system of conductors and analytic properties of the permittivity tensor. Furthermore, we discuss alternative choices of regularization of the capacitance matrix, which allow us to find the charge exchanged between the conductors having been brought to an equal potential. Finally, we discuss the tacit approximations used in standard treatments of the electric circuits, demonstrating how the formulae for the capacitance of capacitors connected in parallel and series may be recovered from the capacitance matrix.

A multiband microstrip antenna is designed for wireless communication application with fractal and defected ground structures. Antenna prototype is fabricated using Rogers RT Duroid 5880 dielectric material on a double layer PCB with dielectric constant 2.2 and thickness 0.8 mm. Through implementing the concept of elliptical shape fractal geometry to microstrip patch antenna, more miniaturization is achieved. Further with defected ground structures, wide impedance bandwidth and gain are achieved. A compact microstrip feedline is used to couple electromagnetic energy to radiator through lumped port. Proposed antenna shows multiband characteristics. Antenna resonates at 2.6 GHz, 6 GHz and 8.2 GHz frequency bands with impedance bandwidth of 410 MHz, 1070 MHz and 4840 MHz. Experimental validation is done to validate simulation results. Antenna operates on different wireless standards like Wi-Fi (2.4 GHz), WLAN (2.4/5.2/5.8 GHz), Wireless Body Area Network (2.3/2.4 GHz), which falls under ISM (Industrial Scientific and Medical) band applications. It also covers communication bands, X-band (8-12 GHz) and S-band (2.3-2.4 GHz).

A conformal circularly polarized UHF antenna integrated on the body of a CubeSat is presented. The antenna operates at 485 MHz and provides at least 10 MHz impedance bandwidth. Traditional UHF antennas for CubeSat have been wire or tape measures that require mechanical deployment, whereas the antenna reported in this paper does not need such treatment and therefore has a potential application in CubeSat mission by promising a more reliable communication link and reduced cost. The measurements showed good agreements with the design data, validating frequency response, bandwidth, and circular polarization level of the proposed antenna.

This article presents the design and development of a low profile substrate integrated waveguide semi-circular cavity-backed antenna loaded with dielectric cylinders of glass-reinforced epoxy and Teflon. The substrate integrated waveguide semi-circular cavity-backed antenna without dielectric loading radiates at 5.8 GHz with 3.13 dB gain. The antenna is modified by putting dielectric cylinders of different materials and different sizes at the edge of a semi-circular cavity to enhance the gain of the antenna. The new antenna thus created has improved gain of 8.13 dB. All simulations are done using high frequency structure simulation software. The proposed design is fabricated on a glass-reinforced epoxy substrate with a semi-circular cavity having a size of 60 mm x 50 mm. The measured results are in good agreement with simulated ones.

The Ricean probability density function (pdf) is widely used to estimate the electromagnetic field distribution in indoor environments. The goal of using the Ricean or other pdfs is to evade the computational cost of deterministic field calculation. The parameters of the pdfs are usually obtained using the maximum-likelihood estimation which is here shown to fail in local areas close to the antenna where the direct field varies significantly. This paper presents the new localized maximum likelihood method which is valid in close regions as well. Moreover, the maximum-likelihood method requires a large number of field values within the local area to yield the parameters of the pdf. This paper presents the ray-tracing maximum-likelihood (RTML) method where a much lower number of field values are required. These values are determined using ray-tracing and without the need to account for the computationally expensive higher-order reflections. The RTML fails in local areas close to the antenna, and thus the new localized RTML is presented to restore accuracy.

In the gyrotron traveling wave amplifier (gyro-TWA), high loss dielectric materials loaded in a cylindrical waveguide are adopted to suppress the unwanted parasitic oscillations. It is of great importance to accurately understand the relative permittivity ε_r and tanδ for studying the microwave and millimeter wave dispersion, and loss properties of a specific mode. The high lossy dielectric loaded circuit of the gyro-TWAs made of the BeO-SiC ceramic with certain relative permittivity and loss tangent are theoretical calculated, simulated and measured. The field distribution, dispersion and loss properties of three different dielectric loaded circular HE^d₁₂, HE^d₂₂ and TE^d₀₂ modes (corresponding to the TE₁₁, TE₂₁ and TE₀₁ modes in the smooth hollow cylindrical waveguide respectively) in different frequency bands are respectively investigated. The theoretical analysis, simulation, and measurement results have a good agreement. This work has clear guiding significance for the stable work of gyro-TWAs.

In this paper, using binary phase-shift keying (BPSK) modulation, analytical expressions of bit-error-rate (BER) for various non-homogeneous fading environments (α-μ, η-μ and κ-μ) subjected to SαS noise are obtained. The derived results are expressed in terms of Meijer's G-function and Gamma function. These expressions are used to study the performance of other prominent fading models (like Nakagami-m, Rayleigh, Rician, and Hoyt) available in the technical literature. Further, it is shown that the effect of the impulsive index (α) over BER is much pronounced compared to the amount of fading (AF). Numerical results are provided for different impulsive settings. The derived results corroborate with simulations.

Electromagnetic waves propagation in both homogeneous and random magnetized conductive plasma is considered including longitudinal, Pedersen and Hall's conductivities. The second-order statistical moments of scattered electromagnetic waves in the conductive turbulent magnetized plasma slab with electron density fluctuations are investigated on the bases of the set of stochastic differential equation. Refractive index and polarization coefficients of both the ordinary and extraordinary waves are calculated for the polar terrestrial ionosphere. Using new spectral method and the boundary conditions, transversal components of scattered electromagnetic waves are calculated. Experimentally observed Stokes parameters describing the depolarization effects are calculated for the arbitrary correlation function of electron density fluctuations. Coherent matrix describing polarization features of non-plane waves generalizing the Stokes parameters is obtained.

In this paper, a novel compact lowpass-bandpass microstrip diplexer with high isolation is proposed. The proposed structure consists of a lowpass filter section and a bandpass filter section. The lowpass filter section is designed at a cut-off frequency of 2 GHz with sixth order elliptic filtering characteristics. The bandpass filter section is designed at 3.5 GHz by using a meandered dual-mode loop resonator (MDMLR). The MDMLR is coupled to input port by open circuited feeding lines. The lowpass-bandpass diplexer is formed by combining lowpass and bandpass filter sections without using an additional matching circuit. The designed lowpass-bandpass diplexer has been fabricated and measured in a very good agreement with the simulated results. Isolation between the output ports has been measured as better than 40 dB.

This paper proposes a novel terahertz demultiplexer based on metamaterials. Its surface metal structure comprises double U-shaped structures and a rectangular wire. The demultiplexer can separate terahertz of 0.225 THz and 0.410 THz, with high isolations of 41 dB and 38 dB, low insertion losses of 0.07 dB and 0.11 dB, and stable group delays of 3.5 ps and 3.8 ps at the center frequency, respectively. The equivalent parameters of metamaterials are simulated, and the electric field, current, and power distribution characteristics at operating frequency points are analyzed. This metamaterial is easy to process and is expected to be applied in future 6G wavelength division multiplexing systems.

Recently, optical nano-antennas (NAs) have been introduced as an alternative approach for photovoltaics devices in solar power harvesting application. In this work, we introduce a new modification to the conventional Archimedean spiral NA to improve its radiation/harvesting efficiency and directivity. The proposed design is a rectangular spiral NA of two tip-to-tip opposing arms which are separated by an air gap. The reported design performance is investigated in terms of the radiation efficiency, directivity, polarization, radiation pattern and total harvesting efficiency. The numerical study is carried out using the finite integration technique (FIT) within the wavelength range 300-1600 nm. The presented design offers a maximum radiation efficiency of 88% in free space and 97.9% on top of silicon dioxide (SiO₂) substrate at a wavelength of 500 nm where the maximum radiation of the sun occurs. In addition, the proposed design has a maximum directivity of 10.8 in free space which is increased to 19.1 on top of a substrate at 500 nm. It is found that the suggested rectangular design shows an enhancement in the radiation efficiency and directivity over the counterpart Archimedean nano-spiral antenna by 10% and 208%, respectively. The proposed rectangular design introduces total harvesting efficiencies of 96.2%, 98.1% in free space and on the substrate, respectively. Moreover, the effect of round edges that may appear in the fabrication process is also considered.

In this paper, the performance of circularly polarized (CP) adaptive sub-arrays integrated into 5G laptop device is investigated in the presence of a whole-body human phantom model. In addition, the radiation effect of the steered beam patterns has been analyzed by calculating the specific absorption rate distribution and temperature rise. In this target, a single-feed CP antenna element has been firstly designed to resonate at 28 GHz with high realized gain and radiation efficiency. Then, 4 sub-arrays have been constructed in a rectangular configuration with four-elements for each sub-array. To let the study more realistic, a complete human model is considered to investigate the radiation effects. The measured reflection coefficient and realized gain results of the designed antenna element are found to be -30 dB and 7.82 dB, respectively, in the assigned frequency band. Likewise, the antennas sub-arrays have approximately kept the same impedance matching attitude with high insertion loss of -22 dB and a realized gain and radiation efficiency of 16.85 dB and 86%, respectively, on average. Furthermore, the sub-arrays scan patterns and coverage efficiency has been studied considering the existence of the human body in different scenarios. Regarding the RF exposure, the results show that the resultant maximum values of specific absorption rate and power density do not exceed 1.52 W/Kg and 3.5 W/m², respectively, whereas, the maximum exposure temperature in such a case is less than 2.8°C after 30 minutes and decreases to 0.5°C after a penetration depth of 3 mm which reflects the possibility of safe use.

Using multiple-Input Multiple-Output (MIMO) configuration is not new in the field of wireless communication to increase the capacity of the system. This configuration is still valid to use nowadays with the modern wireless configuration such as the Fifth generation (5G). Massive MIMO is the key resource of the 5G systems due to its huge ability to increase the capacity of the network and on the other hand its ability to enhance both spectral and transmit-energy efficiency. The need for using Massive MIMO comes from the increase in using smartphones, tablets, and the rise of the Internet of Things. This increasing demand for the use of wireless applications requires networking and Internet infrastructures to meet the needs of current and future multimedia applications which massive MIMO satisfies. The key limitation of using massive MIMO is the cost of installation of these antennas and how to multiplex between them. In addition to this, the Radio Frequency (RF) links are also increased where this increase leads to high system complexity and hardware energy consumption. Because of this, reducing the required number of RF chains is essential to use by performing antenna selection which this paper aims to evaluate without significant performance loss which can be performed by employing low-resolution Analog-to-Digital Converter (ADC) to select an antenna with the best tradeoff between the additional channel gain and increase in quantization error. In this paper, Quantization-Aware Greedy Antenna Selection (QAGAS) algorithm has been proposed and compared with other antenna selection algorithms especially simple algorithms like random selection and Fast Antenna Selection (FAS) algorithm. The achieved capacity is compared with that of a very simple scheme that selects the antennas with the highest received power. The system capacity obtained from QAGAS is evaluated related to the transmit power of the Base Station (BS) and the quantization bits used in the low-resolution ADC. The simulation is also performed for different numbers of users served by the BS and with the number of antennas at the BS. The simulation results show that the proposed algorithm indicates a potential for significant reductions of massive MIMO implementation complexity, by reducing the number of RF links and performing antenna selection using simple algorithms.

This paper presents the analytic analysis, and proof-of-principle prototyping of a new type of magnetic spring with preload and a linear stroke length. An analytic based magnetic charge modeling approach is utilized to investigate the magnetic spring's energy density, stiffness characteristics and linearity. It is shown that whilst the proposed magnetic spring has a lower mass and energy density than a mechanical spring, the magnetic spring offers several unique characteristics, such as contact-free operation, inherent preload as well as over-force failure protection. In addition, the operating principle of the presented magnetic spring can be extended to realize both positive and negative variable stiffness adjustment characteristics.

Modern combat teams face an increasingly complex battlefield, where threats may arise from a number of different sources. Examples include not only conventional attacks through rocket propelled grenades but also improvised explosive devices and weaponised unmanned aerial vehicles. Combat teams can now be equipped with sophisticated surveillance and reconnaissance capability, as well as automatically activated defences. The focus of this paper is to consider the utility of collaborative active protection systems, which are designed to provide an active defence against threats to a combat team. Specifically, a general statistical framework for the analysis of such systems is introduced, with a particular focus on high power radio frequency directed energy weapon countermeasures. The mathematical model allows for a subset of the combat team to be responsible for target detection and tracking, and a time-varying subset of team members with suitable countermeasures to be specified separately. The overall probability of threat defeat and team survivability is then derived. Some examples are provided to investigate the utility of such systems.