Artificial noise (AN) aided method in mmWave is hard to realize due to large transmit antennas and also requires additional power. This paper proposes coding matrix secure transmission based on quadrature spatial modulation (QSM) utilizing a frequency modulated diverse retrospective array (FMD-RDA). Specifically, we adopt coding matrix for frequency increment with QSM symbols to form part of FMD-RDA angular-range array factor. Consequently, low probability of detection (LPD) is created during the QSM transmission without additional power. The desired receiver should know the particular coding matrix a priori. Importantly, the system has automatic user tracking ability with no channel state information (CSI) needed at the desired receiver and can handle receivers with highly correlated channels. Further, secrecy outage probability (SOP), asymptotic lower bound on eavesdropper's (Eve's) detecting error probability and average data leakage rate are analyzed without Eve's CSI. Simulation results show that increasing the coding matrix, satisfactory secrecy is attained for the proposed scheme. Moreover, through the results certain essential secrecy information has been highlighted that is not captured by the classical SOP making the proposed scheme an attractive technique for QSM applications.

An ultra-wideband microstrip bandpass filter which operates from 3.1 GHz to 10.6 GHz, with high selectivity and sharp notched band is presented and experimentally verified. The filter is composed of a square loop shaped defected ground structure, metal faces, and microstrip lines. By adding two short stubs connected by a short circuit point on the microstrip lines, the filter achieves an attractive capacity in out-of-band rejection. By placing open stubs in microstrips, the filter realizes a notched band in passband. To illustrate the possibilities of the new approach, an ultra-wideband microstrip bandpass filter is designed and fabricated. Measured results agree well with the predicted counterparts.

In the paper, a universal compensation method is presented to improve the imbalance of a trans-directional coupled-line (TRD-CL) based balun caused by the inevitable physical separation between the TRD-CLs. Using this method, the input mismatch and output imbalance can be effectively solved. Moreover, since the compensation is achieved by shortening the two TRD-CLs instead of adding additional stubs, size miniaturization is maintained. Design formulas are derived using the signal flowchart and even-odd mode analysis. A prototype operating at 1.6 GHz is also designed and measured to verify the proposed method.

In this paper, a spectral domain implementation of the fast multipole method is presented. It is shown that the aggregation, translation, and disaggregation stages of the fast multipole method (FMM) can be performed using spectral domain (SD) analysis. The spectral domain fast multipole method (SD-FMM) has the advantage of eliminating the near field/far field classification used in conventional FMM formulation. The goal of this study is to investigate the similarities and differences between the spectral domain analysis and conventional FMM formulation. The benefit of the spectral domain analysis such as transforming the convolutional form of the Green's function to a multiplicative form is incorporated in the SD-FMM method. The study focuses on the application of SD-FMM to one-, two-, and three-dimensional electric field integral equation (EFIE). The cases of perfectly electric conducting (PEC) strips, circular perfectly conducting cylinders, and perfectly conductor spheres are analyzed. The results from the SD-FMM method are compared with the results from the conventional FMM and the direct application of Method of Moments (MoM). The SD-FMM results agree well with results from the direct application of MoM.

In this paper, a monolayer metasurface that can simultaneously generate multi-mode vortex waves in ultra-wideband is proposed. Smooth phase variation is obtained by properly assigning the arm lengths of arrow-shaped metal on the top of the reflective metasurface unit cell. Different reflective cells are arranged in different sectors to form a phase-shifted surface that can convert a linearly polarized plane wave into a vortex wave. The full-wave simulations show that the designed reflective metasurface can generate vortex wave with multi-mode in ultra-wideband from 18 GHz to 42 GHz, which is in good agreement with the theoretical analysis. The proposed reflective metasurface paves an effective approach to generate vortex wave with multi-mode in ultra-wideband for OAM-based systems. Compared to the traditional ways of generating vortex waves, our design has the advantage of wide bandwidth.

We report decoupling of two closely located resonant dipole antennas dedicated for ultra-high field magnetic resonance imaging (MRI). We show that a scatterer slightly raised over the plane of antennas grants a sufficient decoupling even for antennas separated by very small gap (below 1/30 of the wavelength). We compare the operations of two decoupling scatterers. One of them is a shortcut resonant dipole, and the other is a split-loop resonator (SLR). Previously, we have shown that the SLR offers a wider operational band than the dipole and the same level of decoupling. However, it was so for an array in free space. The presence of the body phantom drastically changes the decoupling conditions. Moreover, the requirement to minimize the parasitic scattering from the decoupling element into the body makes the decoupling dipole much more advantageous than the SLR.

In this paper, a compact tri-band microstrip filter is designed and fabricated for application in wireless communication systems such as Bluetooth, WIMAX (World Wide Interoperability for Microwave Access), and WLAN (Wireless Local Area Network). In the proposed filter, three resonators, i.e., Stub-Loaded Resonator (SLR), Stepped-Impedance Resonator (SIR), and Square Split Ring Resonator (SSRR), are used. The dimensions of the proposed filter are equal to 16.2×12.3 mm² or 0.219λ_g×0.166λ_g. These dimensions indicate that the proposed structure has reduced the size by about 40% compared to the conventional samples. This is the main advantage of the proposed filter. Finally, in order to investigate analysis and simulations, the proposed filter is fabricated. The results prove correctness of the design, analysis, and simulations.

Design of a resistive-loaded Transverse Electromagnetic (TEM) horn antenna for air-coupled ground penetrating radar (GPR) is proposed in this paper. As the focus is on the application in sensing pavement subsurface, some issues should be considered, such as ultra-bandwidth (UWB) performance, air-coupled detection, high fidelity, compact structure, and simple fabrication. The resistive-loaded horn antenna with a microstrip-type balun was constructed and measured to facilitate the issues. With the radiation towards concrete ground at a height of 0.5 meters, the measured results suggested that the impedance bandwidth of the antenna was 0.5~14 GHz with a return loss less than -10 dB. The radiation waveform of the horn antenna also showed a late-time ring. A radar experiment result showed that the antenna performed excellently for pavement layer detection.

In this paper, magnetic fluids based on iron oxide Fe₃O₄ and 5BDSR alloy were obtained. Magnetic particles were obtained by nanosecond pulsed laser ablation. The preparation of the magnetic fluid was carried out by mechanical and ultrasonic stirring in a solution of polymethylphenylsiloxane. It is shown that under the influence of an external magnetic field, the spectral properties of the magnetic fluid of the 5BDSR alloy correspond to characteristics that can be used to create a magnetic gate.

In this paper, a compact reconfigurable tri-band bandstop filter (BSF) with sharp-rejection and high selectivity is presented. The proposed filter is based on a 50\,Ohms microstrip feed line, six hexagonal metamaterial cells (HMCs) with different sizes and switches. The structure of the filter has seven different modes of operation characterized. A good agreement between the simulated and measured results is obtained. The results indicate that the proposed filter design, with overall size of 0.28λ_gx0.17λ_g, is a good candidate for multiservice radios applications.

This second paper presents the numerical evaluation of the statistical hybrid model for a number of indicative overhead medium-voltage (OV MV) and underground medium-voltage (UN MV) broadband over power lines (BPL) topologies. In essence, this paper assesses the effect of a number of key of factors already reported in [1], such as the distribution power grid type, BPL topology class, coupling scheme, channel attenuation statistical distribution, and injected power spectral density (IPSD) limits, on the computed capacity ranges of the statistical hybrid model. For the assessment of the different channel attenuation statistical distributions, the graphical analysis and the proposed metrics of capacity percentage change and average absolute capacity percentage change are demonstrated while two rules of thumb estimating the fidelity results are also proposed.

This pair of papers proposes a new approach towards the channel modeling of transmission and distribution broadband over power lines (BPL) networks either on the theoretical or on the practical basis. The proposed statistical hybrid model is the synthesis of the well-validated deterministic hybrid model and a set of well-known statistical distributions widely used in communications literature such as Gaussian, Lognormal, Wald, Weibull and Gumbel statistical distributions. In this paper, the theoretical framework of the statistical hybrid model, as well as the flowchart of the statistical hybrid model, is analytically presented.

A wide Ka-band frequency agility synthesizer with low phase noise and high frequency stability is presented in this paper, which serves as the emission source of transmitter and the local oscillator (LO) of receiver in fully electronic millimeter wave (MMW) imaging system. In order to improve operating frequency and shorten hopping time, a novel method is proposed in this synthesizer. By mixing direct digital synthesis (DDS) with multiple phase locked loops (PLLs) and multiplying the mixed signal, a high output frequency with low phase noise and rapid frequency hopping is realized. The experimental results show that the frequency synthesizer achieves frequency resolution of 1 MHz from 27 to 32 GHz and phase noise of -95 dBc/Hz at 10 kHz carrier offset. In addition, the frequency switching time is 2 μs, and broadband spurs do not exceed -60 dBc.

This research proposes a novel method based on generative adversarial network (GAN) and hidden Markov random field (HMRF) models, for use in large-scale high-resolution synthetic aperture radar (SAR) images. The method consists of three stages. In the first stage, a virtual target and a SAR image are generated by using the GAN model, according to the statistical and gray-level features of the original SAR image used in detection. In the second stage, the virtual target is embedded in the generated image. In the third stage, real targets are detected in the generated image by using the HMRF model. The experiment results show that the proposed algorithm based on GAN and HMRF models can be applied to ship detection in high-resolution SAR images, with high accuracy and processing speed.

In this paper, the detection of through the wall multiple human subjects is proposed using the Doppler radar with the help of Hilbert vibrational decomposition (HVD). The proposed Doppler radar can detect the multiple human subjects behind the wall by respiration rate estimation of human subjects. With different breathing conditions resembling to the real life scenario, the respiration signals of human subjects are extracted. The algorithm works in every real life situation to detect the respiration rate of human subjects and finds application in the earthquakes, building collapses and security applications.

This work involves designing an antenna that meets the requirements of radar systems. The associated technology, which was for a long time reserved for the military field, is now available in the civil field, as well as in the biomedical sector for the development of ``monitoring'' systems allowing to monitor the state of health of a patient in a non-invasive way. The goal of this article is to design a wearable textile antenna to detect cancerous tumors of a patient without direct contact with the skin, taking into account the electromagnetic waves directed towards the human body due to the difference between the dielectric constants of healthy and unhealthy tissues. Here we present a miniature AMC antenna of rectangular shape that satisfies the UWB characteristics in terms of bandwidth and reflection coefficient. The proposed AMC antenna operates in X-frequency band, (8-12 GHz). Using a model of dielectric artificial skin, we have simulated the specific absorption rate on the human body in order to better respect the FCC standards allowed 1.6 W/kg averaged to 1g of human tissue.

In view of the dynamic wireless energy charging of electric vehicles, because of the different types or dynamic changes of carrying capacity, the distance between receiving coil at the chassis of electric vehicles and transmitting coil under the road will change dynamically. The unsuitable distance may make the system keep an under-coupling state and reduce the output power of energy transmission system. To improve the system output power, and a relay coil can be added between transmitting coil and receiving coil. But the system charging state may change from under-coupling state to over-coupling state directly because of the introduction of relay coil, and at the same time, the system may show frequency splitting phenomenon. These problems can be solved by adjusting the position of relay coil, the rotating angle of relay coil, and the load value. The experiment shows that the system output power can be improved obviously by increasing relay coil and suppressing frequency splitting. In order to obtain the optimal parameters about the position, rotation angle of relay coil, and load resistance, a genetic algorithm is introduced to improve the output power. At last, using the optimal system parameters, a magnetic coupling resonant wireless power transmission (MCRWPT) system is designed and manufactured, by which the effectiveness and advantage of this approach are verified by experiments.

We present an extension of Large Time Step (LTS) method to electromagnetic wave propagation involving multilayered homogeneous media. The LTS method proposed by LeVeque is an extension of Godunov's method for the numerical solution of hyperbolic conservation laws. In this method, very large time steps are allowed by an increase in the numerical domain of dependence compared to conventional explicit methods constrained by the Courant-Friedrichs-Lewy stability criteria. This can lead to additional complexities when being applied to multilayered homogeneous media due to presence of material interfaces. Appropriate treatment of material interface boundaries is proposed in the present work in the context of finite volume time-domain method with LTS. Numerical examples are presented involving solution of time-domain Maxwell's equations in a layered dielectric medium using LTS approach.

This paper presents the design of an ultra-wideband (UWB) antipodal Vivaldi antenna (APVA) for radar and microwave imaging applications. A slotted APVA design is introduced to improve the low-end bandwidth limitation frequencies as well as to enhance the gain and directivity of the antenna. The optimizations of the design offer good results by using a cost-effective substrate, fiberglass reinforced grade 4 (FR4) material. The regular APVA antenna design only presents average results of gain (4-6 dBi) and directivity (4-7 dB). However, the addition of slots on the edges of antenna is able to increase the peak value of gain and directivity up to 73.65% with 7.64 dBi and 8.92 dB, respectively. Besides, the radiation pattern of the antenna is also improved by using the slotted design where the main lobe level is larger than regular APVA design. Both antennas presented in this paper are designed in compact size of 42.8 mm x 57.3 mm. The antennas are also designed to operate within the frequency range of 3.6 GHz to 10 GHz frequency.

New accurate approximation is proposed using integral expressions for evaluating the magnetic force between cylindrical permanent magnet arrays. The magnetic field distribution is calculated analytically by using Coulombian model. In this paper, every cylindrical magnet is divided into elementary cuboidal magnets.The accuracy can be controlled by regulating the value of elementary cuboidal permanent magnets ``N''. The approximation can also be used to calculate the force interaction in the cylindrical linear single-axis-actuator. We confirm the validity of magnetic force calculation by comparing it with other methods and measurements. The calculation results are in very good agreement with measured values, which indicates the feasibility of our approximation.