Design and analysis of a novel wide-band covering, hetero triangle linked hybrid web fractal antenna is presented in this paper. The hetero triangle linked hybrid web structure has been designed through multiple iterations in the CST MICROWAVE STUDIO electromagnetic simulation tool and has been fabricated on FR4 dielectric of ε_r = 4.4 with height of 1.6 mm. The proposed antenna offers a comprehensive bandwidth of 18.055 GHz, covering from 1.945 GHz to 20 GHz. It supports various applications starting from 3G, LTE, ISM, Bluetooth, Wi-Fi, WLAN (2.4-2.48 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.72-5.82 GHz), WiMAX operating in the 2.3/2.5 GHz (2.305-2.36 GHz/2.5-2.69 GHz), 5.5 GHz (5.25-5.85 GHz) and Satellite communication (Ku band: Uplink of 14 GHz and Downlink of 10.9-12.75 GHz). The proposed antenna provides peak realized gain of 7.17 dB with efficiency more than 78% in the operating band. The antenna parameters such as reflection coefficient, gain and radiation patterns are determined through numerical simulation, and good matching is obtained with measured results.

A one-shot rescaling process, namely Automated Scaling Region of Interest (AS-ROI), is combined with an inversion technique of Forward-Backward Time-Stepping (FBTS). The purpose is to alleviate the ill-posedness and nonlinearity of inverse problem by reducing the size of the unknown problem. The inversion solution is carried out to reconstruct tumour as an unknown object in coarse investigation domain of lung area which is then rescaled down corresponding to object location and size. In this paper, edge preserving methods consisting of edge preserving regularization and anisotropic diffusion are imposed alternately on the solution and reconstructed profiles to improve the current method of AS-ROI. Results on the reconstructed lungs and tumours give significant insight of the proposed work. Accuracy level for the reconstructed profiles are significantly improved in spite that spatial resolution is retained as the original setting of FBTS.

Research on RCS evaluation for electrically large objects has been a hot topic for decades. Although multilevel fast multipole algorithm (MLFMA) has been the most popular method in scattering computation, due to the limitation of both CPU speed and memory size in a single computer, realistic large targets require discretization with millions of unknowns still cannot be solved by sequential implementations of MLFMA. In this paper, we introduce a Docker-enabled parallel MLFMA computing system based on MPI, which is proved to be friendly for deployment and economical for scalability, to solve electrically large scattering problems. In addition, the capability of the proposed system has been demonstrated by several canonical examples.

In this work, the design of a switched beam antenna array based on an optimized Butler matrix feeding network was done with a compact microstrip structure and a set of microchip antennas working at 2.45 GHz. The obtained antenna feeding network was tuned and optimized by using suitable unsupervised techniques to obtain a compact and efficient structure. A microstrip antenna array prototype composed by four elements was fabricated and experimentally tested. Good impedance matching and radiation properties have been experimentally verified with reference to the main beam steering capability.

Based on the multi-mode interference effect in the periodic dielectric waveguide, a novel waveguide crossing structure is proposed and analyzed. The structure can achieve crossing connection of three periodic dielectric waveguides at the same position with low crosstalk and relative high transmission coefficient. Based on electromagnetic numerical simulation methods, the proposed crossing structure of three periodic dielectric waveguides is calculated and analyzed in details, and at the optical communication wavelengths near 1.55 μm, crosstalks below 22 dB between the three crossing periodic dielectric waveguides are achieved.

An omnidirectional compact antenna based on dual-band Split Ring Resonators (SRRs) for 2.45 GHz wireless local area network (WLAN) and 3.5 GHz worldwide interoperability for microwave access (WiMAX) applications is presented. Dierent and new properties of SRRs, such as dual-band or multi-band performance in the design of compact antennas, can be obtained by making the rings unequal and asymmetric. The dual-band SRR antenna is designed with a bandwidth control technique based on stored electromagnetic energy on the resonator rings. The obtained results show that the SRR antenna has good omnidirectional radiation pattern for both bands and good impedance bandwidth. In addition, compactness and flexibility are obtained with a simple structure of the SRRs.

Generally, the null steering is performed by controlling the amplitude and/or phase weightings of all element excitations or only a small number of them. In such cases, a need for extra RF components such as variable attenuators and variable phase shifters with each element in the array is inevitable. In this paper, an alternative method is introduced where the null steering is performed by thinning (or turning off) only a small subset of the elements in the uniform linear arrays. To find an optimum combination of active (on) and inactive (off) elements, a binary genetic algorithm is used. In large arrays, the number of required nulls is much smaller than the total number of array elements, thus only a small subset of the array elements could be sufficient for producing the required nulls rather than optimizing all the array elements. By this way, a faster convergence speed of the optimizer and lowest peak sidelobe level can be obtained. The effectiveness of the proposed method with various subset configurations will be demonstrated and compared with some standard null steering methods.

With the ever-growing requirements of human security check in public, near-field millimeter wave (MMW) imaging techniques have been developing rapidly in recent years. Due to the lack of MMW images, low resolution and indistinguishable texture in most MMW images, it is still a great challenge to do high performance object detection task on MMW images. In this paper, we propose a novel framework to automatically detect concealed weapons and potential dangerous objects based on a single human millimeter wave image, in which a deep convolutional neural network (CNN) is presented to simultaneously extract features, detect suspicious objects, and give the confidence score. Unlike traditional optical image level solutions, we comprehensively analyze the original MMW data for object representation, incorporate domain-specific knowledge to design and train our network. Moreover, combined with the modern focal loss theory, we devise an effective loss function elaborately to optimize our model. Experimental results on both our dataset and real world data show the effectiveness and improvement of our method compared with the state-of-the-arts.

Using uniform linear array (ULA), a passive localization algorithm is presented for mixed far-field (FF) and near-field (NF) signals scenarios. Based on the high-order cumulant (HOC) technique, a special Hermite matrix is constructed by three fourth-order cumulant matrices, which are calculated by dividing the ULA into two sub-arrays. Then, the special matrix of signals is decomposed to obtain the source subspace. According to ESPRIT algorithm, two transformation matrices of all sub-arrays can be obtained. Meanwhile, the two transformation matrixes could be used to calculate the range and angles of arrival (AOA) of NF sources, as well as AOAs of FF sources. Moreover, compared with twostage MUSIC (TSMUSIC) and four-order cumulant MUSIC method, the proposed algorithm has higher accuracy for localisation of both FF and NF sources without any spectral search.

This paper presents a Ka-band TDD transceiver system module for the secondary surveillance radar application with attractive temperature characteristic. Four multifunction chips and a MEMS filter are designed and fabricated in GaAs pseudomorphic high electron mobility transistor (pHEMT) process and MEMS technology in this work, respectively. These multifunction chips and MEMS filter with some other commercial chips are assembled in a compact cavity to form the transceiver system. The temperature characteristics of the designed chips and the whole transceiver module are measured respectively in this work. Benefiting from the designed temperature compensation circuits on the chips, the transceiver is able to work from -55˚C to +75˚C with little performance fluctuation. The noise figure of the receiver is less than 3.7 dB in the 400 MHz working bandwidth. Its dynamic range is more than 59 dB with more than 23.9 dB power gain. The maximum output power of the transmitter is larger than 30.3 dBm. The system only has two input/output ports and one control bus, which is suitable for the large-scale system integration.

We theoretically analyze perturbations of ambient magnetic field due to electric currents caused by motion of a dielectric ball in a conductive fluid half-space. The approximate analytical solution of the problem has been derived for the case of arbitrary orientation of the ambient magnetic field and under the requirement that the fluid flow around the ball is laminar and potential in character. We examine spatiotemporal distribution of these perturbations and their dependence on both the depth and distance from the moving ball. The amplitudes of electromagnetic perturbations generated by the fluid flow around the ball have been compared with that resulting from gravity waves in the fluid.

In-Service Inspection (ISI) plays a critical role in ensuring the safety and security of nuclear power plant and personnel. The limited access and high ambient temperature conditions impel the need for remote inspection techniques using semi automated vehicle. The electrical actuators driving the ISI robotic vehicle must satisfy the requirements of high operating temperature, high torque density,compact size and low weight.Currently, permanent magnet brushless motors are used due to its compact size and high eciency. However, due to risk of demagnetization at high temperature as well as due to depleting resources of rare earth material alternate topologies without using permanent magnets shall be considered. This paper investigates the performance of Permanent Magnet (PM) brushless motor and Switched Reluctance (SR) motors for high temperature applications. SR motor is designed as per fundamental design equations satisfying the application requirements. Electromagnetic performance isveried by Finite Element Analysis (FEA) and thermal performance is veried by lumped parameter thermal analysis. Finally the performance of SR motor is compared with PM motor in terms of torque, eciency, weight,cost and temperature rise.

A model-based inversion algorithm combined with the curl-conforming volume integral equation method is presented for the reconstruction of 3D anisotropic objects. The forward algorithm utilizes the curl-conforming volume integral equation method. The inversion algorithm is based on the Gauss-Newton method. The approach is applied to the reconstruction of the permittivities of 3D anisotropic objects. Moreover, sensitivity analysis of the data from different polarizations of transmitters and receivers to the anisotropic properties is performed. Numerical examples show the effectiveness of the inversion algorithm and demonstrate the sensitivities of data from different transmitter and receiver pairs to the anisotropy.

In this paper, a novel ultra-wideband (UWB) power divider with dual notched bands using square ring multiple-mode resonators (SRMMRs) is presented. The characteristics of the proposed SRMMRs are investigated by using even- and odd-mode analysis. Then, the initial UWB performance is achieved by introducing SRMMRs to the basic Wilkinson power divider. Finally, two desired notched bands inside the UWB passband are achieved by embedding a pair of coupled dual-mode stepped impedance resonators (DMSIRs) into the SRMMRs. The central frequencies of the notched bands can be easily controlled by the electrical length of the DMSIRs. To validate the design concept, a novel compact UWB power divider with dual notched bands centered at frequencies of 5.8 GHz and 8.0 GHz is designed and measured. The simulated and measured results indicate that it has a low insertion loss and good return loss performance at all the three ports, and a high isolation between the two output ports across the UWB bandwidth from 3.1 to 10.6 GHz with a small size of 0.46λ_g×0.69λ_g, where λ_g is the guided wavelength at 6.85 GHz.

An omnidirectional antenna array is proposed in this paper. The antenna unit of the array is composed of ten radiation patches and the associated microstrip feeding network. Some gaps between top and back patches are introduced in the antenna to improve matching, ease of feeding and enhance the bandwidth. Microwave experiments and numerical simulations are performed to demonstrate antenna functionalities. The fabricated antenna exhibits a bandwidth of 14% (1-1.15 GHz) for VSWR ≤ 1.5, with a gain around 6 dBi. The results are valuable for the design and evaluation of omnidirectional planar antenna arrays with good impedance matching, which are important for airborne and navigation applications.

This paper discusses the spectrum relation in Multiple-Input-Multiple-Output (MIMO) structures and presents an imaging algorithm for sparse linear MIMO array for short range imaging. This algorithm is available for MIMO array consisted by transmit and receive arrays separated from each other. The wave propagation process is used to interpret the spectrum relation in linear MIMO structures; therefore, the convolution relation of spectrum can be clearly understood. Moreover, the spectrum shift effect in linear MIMO structure with separated transmit and receive arrays is discussed and solved according to the spectrum relation. Above all, the imaging algorithm for sparse linear MIMO structure is presented, and the image performance is demonstrated by simulation results.

In order to energize the biomedical implantable electronic devices wirelessly for in vivo health monitoring of patients in remote and inaccessible areas, an alternate driving energy source is highly desirable and increasingly important. In pertinent to this, a thermal energy driven resonant inductively coupled wireless energizing scheme has been developed for powering biomedical implantable devices. The system is designed to convert the generated heat energy to a high frequency energy source so as to facilitate energy transfer through resonant inductive link to the automated biomedical sensing system allied with the receiver unit. The automated biomedical smart sensor is competent to acquire the body parameter and transmit the consequent telemetry data from the body to the data recording segment. The real-time body temperature parameter in different conditions has been experimented. To ensure its accuracy, the sensed data have been matched with the observations carried out by a calibrated device. The intended scheme can be utilized for wireless monitoring of other health parameters like physiological signals and bladder as well as blood pressure of the patients.

This paper deals with the calculation of electric field in a copper piece of cubic shape which is submitted to a sinusoidal magnetic field. This 3D problem is set into equation and solved by means of two different approaches. A stochastic method for 3-D electric field computations is presented and compared to a finite element method. The main goal of this paper is to compare these two methods on a classical problem putting forward the advantages of the chosen method. First of all, we present the problem modelling. Then, the Monte-Carlo method used to solve 3D time dependent problem is described and is compared to the finite element method, in the last part.

The location and topology of grounding grid conductors are necessary to corrosion diagnosis and digging in most cases. In this paper, an integrated detecting device for grounding conductor buried position is designed. Based on the principle of magnetic field method, a multi-layer cascade PCB hollow coil sensor is designed. AC excitation current source, 16-channel control circuit, lock-in amplifier (LIA) circuit and 4-channel synchronous acquisition circuit are realized. The experimental test is completed for the integrated detection device, and results verify the feasibility of the system.

A superconducting synchronous generator (SSG) is proposed for wind power, in which magnesium diboride (MgB₂) superconducting coils are employed as field windings. The stator is composed of conventional copper coils and iron core, while the rotor has no iron core. The whole refrigeration method is adopted in this paper. The thermal barrier is not placed in between the stator and the rotor as compared with the prior HTS generators, so a small air gap width would be possible. In order to study the electromagnetic characteristics of the SSG, finite element method (FEM) is implemented to optimize the SSG and obtain the no-load and load performance of the initial and optimized SSG. Finally, the optimized SSG is compared with a traditional synchronous generator (TSG) of the same power. The results indicate that the optimized SSG has many merits such as small size, light weight, high efficiency and high power factor.