A new C-band monopole antenna is proposed for use in a CAPS-based vehicle monitoring system. This monopole antenna has highly omnidirectional main beam with low elevation angle and sufficient half-power beamwidth by using a cone-shaped ground plane. The impedance bandwidth defined by 10 dB return loss is 650 MHz (5.50-6.15 GHz), and the main beam elevation angle and the half-power beamwidth are about 20° and 40° at the operating frequency 5.885 GHz, respectively. The manufactured prototype has survived a long-distance terrestrial test across China, and the design requirements for the satellite link budget, volume, cost, etc. have been reached.

Eddy current testing (ECT) is known as an effective technology for inspecting surface and near surface defects in metallic components. It is well known that the amplitude of eddy current (EC) density decreases with increasing depth, which is referred to as skin effect. Skin depth is an important parameter that quantifies the speed of attenuation of EC in the depth direction and is closely related to the capability of ECT for detecting deeply hidden defects. It is found that the traditional formula for calculating skin depth derived under the assumption of uniform plane field excitation is not applicable to the cases of ECT with coils. The skin effect in component with flat surface excited by pancake coil has been investigated by the authors. The skin effect in conductive tube tested by bobbin coil and that in conductive bar tested by encircling coil are more complex. The paper studies the skin effect in these two cases. Finite element analysis shows that the attenuation of EC is not only due to the ohmic loss, but also influenced by the diffusion effects, the aggregation effect, and the combined cancellation/diffusion effect of EC. The skin depth of EC associated with bobbin coil is always smaller than that associated with uniform plane field excitation, whereas the skin depth of EC associated with encircling coil can be greater than that associated with uniform plane field excitation under certain conditions.

In the recently published article, Sood et al. (Progress in Electromagnetics Research M, Vol. 44, 3946, 2015) proposed a wide-angle ultra-thin metamaterial absorber structure for wideband applications. The reported unit cell was shown to have simulated wideband absorbivity FWHM bandwidth of 1.94 GHz i.e. from 5.05 GHz to 6.99 GHz. In this article, we prove that the reported structure is not an electromagnetic wave absorber. For the reported structure, we find that absorption is less than 22.3% over a operating bandwidth of 4 GHz to 8 GHz. It is demonstrated that the strong absorption was caused due to ignorance of cross-polarization effect rather than true absorption as they claimed.

This is the first communication reporting a compact broadband printed circular slot antenna with stair shaped ground plane in which bandwidth is enhanced mainly in the lower frequency band on adding 19 strips at regular space intervals in the partial ground plane. The impedance matching at specific band (7.1-8.4 GHz) takes place as a result of circular slot in the patch. The proposed structure is printed on an FR4 substrate with ε_r = 4.3 and 0.025 loss tangent over a compact volume of 20×25×1.5 mm³. The impedance bandwidth (S₁₁ < -10 dB) of the proposed antenna is 133.7 % (3.0-15.1 GHz). The antenna exhibits 4.9 dB peak gain and 74 % peak radiation efficiency in the operating band. Satisfactory results and such a simple and easy to fabricate design with compact space make the proposed antenna a suitable choice for UWB applications, 5.2/5.8 GHz WLAN bands, 3.5/5.5 GHz Wi-MAX bands, X band (8-12 GHz) and other wireless communication systems. Measured and simulated results are in good agreement, affirming the simulation process. Omnidirectional radiation patterns are generally observed in the operating band of the designed antenna.

The discovery of ``quasi-crystals,'' whose X-ray diffraction patterns reveal certain unusual features which do not conform with spatial periodicity, has motivated studies of the wave-dynamical implications of ``aperiodic order.'' This paper discusses various aperiodic configurations generated by Rudin-Shapiro (RS) sequences. These RS sequences constitute ones of the simplest conceivable examples of deterministic aperiodic geometries featuring random-like (dis)order. The scattering properties of aperiodically-ordered thinned 2-D patch arrays based on RS sequences are analyzed by using physical optics approximation. Compared to a periodic case, RS-based antenna array is found to have a substantial reduction in the magnitude of the backscattering component of the scattered signal with half of the elements and the same magnitude of specular reflection. This property is verified by illustrative numerical parametric studies.

This paper presents a broadband planar printed antenna comprising two dipoles with different lengths and a transition structure of microstrip (MS) to coplanar stripline (CPS). These two dipoles are serially connected through CPS. By adding trapezoid and stepped patches, the dipole elements are modified for enhancing the impedance matching of the antenna. In addition, a tapered transition is adopted in the CPS to achieve improved impedance matching. The current work shows a good agreement between measured and simulated results. The measured bandwidth is from 2.43 to 8.04 GHz for VSWR≤2, corresponding to 107.2% fractional bandwidth. Measured peak gain≥4.0 dBi is obtained in the whole operating band.

The problem of electromagnetic (EM) wave scattering on small particles is reduced to solving the Fredholm integral equation of the second kind. Integral representation of solution to the scattering problem leads to necessity to determine some unknown function contained in integrand of this equation. The respective linear algebraic system (LAS) for the components of this unknown vector function is derived and solved by the successive approximation method. The region of convergence of the proposed method is substantiated. The numerical results show rapid convergence of the method in the wide region of the physical and geometrical parameters of problem. Comparison of the obtained results with Mie type and asymptotic solutions demonstrates high degree of accuracy of the proposed method. The numerical results of scattering on particles of several forms and sizes are presented.

A new class of tri-band bandpass filter (BPF) is presented, and harmonic passband bandwidth can be independently controlled. In the implementation, three coupling paths are used to control the bandwidth of each passband. The first coupling path is two grounded vias which are utilized to realize coupling between two short-stub loaded resonators. And the first coupling path delivers signals at the first passband. Meanwhile, the second coupling path delivers signals at both the first and second passbands. And the third coupling path only delivers signals at the third passband. Using this method, both the frequency and bandwidth of each passband can be designed and tuned easily. In this filter design, the first harmonic passband can be adjusted separately and is independent of the fundamental passband. Two grounded vias improve flexibility and form a fundamental passband and harmonic passband independently controllable passband filter. For demonstration, a tri-band BPF with three passbands at 1.5 GHz, 2.5 GHz, and 3.5 GHz with insertion losses of 0.34, 0.76 and 1.08 dB is designed, fabricated and measured. So this proposed filter will be attractive in wireless communication systems.

A new microstrip-to-microstrip vertical transition structure for ultra-wideband (UWB) applications is proposed in this paper. The transition consists of a low impedance microstrip ring stub and a couple of slotline square multiple-mode resonators (MMRs) on the common ground plane. The low impedance microstrip ring stubs are realized by the connection of three single stubs in parallel, and the high-impedance section of slotline SIR is realized by the connection of four single stubs in series. The simulated and measured results are in good agreement, showing good wideband filtering performance with ultra-wideband fractional bandwidth.

In this paper, we present a straightforward numerical algorithm for visual image sequential motion detection based on half quadratic minimization method. To solve the optimization problem modeled for sequential motion detection, an auxiliary functional is introduced. The proposed algorithm is more efficient since the iterative computation is operate mainly on the current frame rather than the whole batch of images. As for the standard visual image sequences with RGB color representation, an intuitive way is to convert it to grayscale image to achieve an approximate motion detection with relatively low computational load. Instead, we propose an improved processing scheme for more accurate detection by utilizing the algorithm separately and then perform fusion on a higher level. Experiment results show that the proposed algorithm can successfully detect moving object in practical visual surveillance applications.

Light-sheet microscopy has attracted considerable attention since it is a fluorescence imaging technique with rapid optical sectioning capabilities for transparent sample. In our study, we report a new application based on light-sheet microscopy for exploratory investigating three-dimensional surface topography of opaque sample. Instead of using inelastic scattering fluorescent signal, our method utilizes the elastic scattering light from the surface of opaque sample, which is illuminated by a light sheet generated by a cylindrical lens. Through a simple structural modification by removing the fluorescent filter, the orthogonally imaging module can capture the elastic scattering image. As the opaque sample is scanned by a motorized stage, the light-sheet microscope acquires a serial of sectional images, which can be stitched to be a three-dimensional surface topography image. This method also offers the opportunity to visualize 3D fingerprint on micron level. Therefore, this technique may be useful in industry and biomedical field for the measurement of surface microstructure.

An approach to separate metallic and dielectric losses in ferroelectric capacitors in all range of tuning under control dc voltages (Udc) is considered. The procedure is based on measurements of the dc voltage dependencies of microwave losses (tanδt(Udc)) and capacitance (C(Udc)) for a set of capacitors with similar layout but with different nominals. Linear extrapolation of tanδt(C) dependencies at different control dc voltages to C = 0 allows to evaluate the dielectric losses tanδd as a function of the control dc voltage. The procedure of separation was performed for a set of sandwich metal/(Ba0:5Sr0:5)TiO3/metal capacitors. Capacitors parameters were measured at a frequency of 2 GHz in a range of electric field strength in ferroelectric of E = (0 - 30) V/μm. The intrinsic commutation quality factor of BSTO lm itself was estimated by the method proposed.

This paper describes a method of designing Frequency Selective Absorber (FSA) which has a transmission band between two neighboring absorption bands. The proposed FSA is composed of a lossy layer on the top and a lossless layer at the bottom. The transmission characteristic is produced by the parallel LC resonators embedded in the lossy layer while the absorption ability is realized by the lumped resistors constructed in the lossy layer. An equivalent circuit model (ECM) is developed and discussed for a better understanding of this method. An FSA prototype is fabricated and measured for demonstration. Experiments show that the proposed FSA has a transmission band at the center frequency of 8.14 GHz, which agrees well with simulation. Both transmission and refection coefficients from 4.5 GHz to 7.5 GHz and from 9.1 GHz to 11.3 GHz are under -10 dB, which indicate good absorption in these frequency bands. In addition, the performance of the proposed FSA demonstrates a low sensitivity with respect to the polarization of incident EM waves and is maintained well when the incident angles range from 0˚ to 45˚.

High frequency measurements at 50 MHz-10 GHz were performed for the first time using interdigitated electrodes on a low temperature co-fired ceramic substrate to analyze fungal spores. Wet and dry spore generation methods were evaluated and tested with two different fungal species. The dry generation method was found feasible for RF measurements, since the component capacitance increased 14-21% in the 2-6 GHz range, but for the wet generation method the capacitance decreased only slightly (<1%). Based on these initial results the RF measurements have the capacity to evaluate the quantity of fungal spores but not to identify their species.

A printed dual-port coplanar waveguide (CPW)-fed antenna is proposed for wideband communication systems. The antenna includes two identical hybrid trapezoidal-elliptical radiating elements that are printed perpendicular to each other. Also, two orthogonal CPW lines are used to feed the antenna. In order to achieve broadband dual-polarized operation with a compact size, the geometrical parameters of the antenna are optimized by using Ansoft HFSS. The antenna was fabricated and tested. Reasonable agreement between the simulation and experimental results is obtained. The fabricated prototype with a small size of 25×53 mm² can cover the wide operating frequency band from 2.4 to 18 GHz (reflection coefficient less than -10 dB) for both ports. The measured isolation is better than 25 dB over the entire operating bandwidth. Moreover, the measured results show that the proposed antenna can provide omnidirectional radiation patterns with a good orthogonal polarization operation, reasonable gain, high radiation efficiency, and constant group delay.

Ground penetrating radar (GPR) may be used to detect cracks in a buried pipe. Using GPR, there are only a few techniques, such as statistical approach robust principal component analysis (RPCA). to detect cracks in buried objects. Buried nonmetallic pipe crack detection is an important application for GPR to analyze the structural health of underground pipelines. The strength of a reflected signal may be feeble from a cracked location as compared to position with respect to that from other positions of the pipe. Currently, crack detection is a challenging task, especially when the buried pipe is nonmetallic, and soil moisture varies. In this paper, the problem of crack detection in a PVC pipe using GPR is attempted. It is a challenge to detect small sized cracks in an underground PVC pipe because the GPR image is flooded with correlated background signal or clutter, and the image patterns are typically irregularly distributed. In order to efficiently detect the crack in a buried PVC pipe, a novel adaptive crack detection algorithm has been developed with the help of covariance of real GPR data and covariance of normal distributed synthetic Gaussian data. Results are evaluated and validated to show the effectiveness of crack detection algorithm.

The study done in this paper focuses on the detection of breast cancer by neuronal approach, by rotating the transmitting antenna from 15°, 30°, 45°, 60°, 75° to 90° relative to its initial position which is of 0° (i.e. to the opposite of the reciving antenna). We have generated our database by using a CST electromagnetic simulator for each antenna location. Then the learning and test phases of our artificial neural network (ANN) are done for seven antennae locations using two learning algorithms which are: the Scaled Conjugate Gradient Back-propagation (Trainscg) and the Gradient Descent with Momentum (Traingdm). A comparative study was conducted for all the seven cases. The results obtained are very satisfying and show that the best location of the transmitter antenna is at 60° and that the learning algorithm Trainscg gives better results than Traingdm.

This paper presents the power density evaluation and power mapping performance of a novel magnetic geared double-stator permanent magnet generator (DSPMG) which is proposed to address problems of mechanical geared generators for low-speed power generation applications. The operating principle is based on three PM rotors consisting of prime permanent-magnet (PM) poles in the middle rotor and field PM poles in the inner and outer rotors respectively. To evaluate the power density performance, a 2-D finite-element method (FEM) is used to predict the performance of the generator, and a demonstrator prototype is fabricated and evaluated experimentally. The power density characteristics of the proposed generator are analyzed and reported. The measured results agree closely with the simulated ones to verify the validity of the magnetic geared generator design. Finally, a measurable comparison is conducted with other published prototype magnetic gear machines to demonstrate its benefits of higher power density and smaller volume size.

In this paper, the design and implementation of a three-layer linear polarization converter having broadband and asymmetric transmission (AT) properties is demonstrated. A 3.2 mm thick transmission-type polarization converter with two separate operating frequency bands is obtained with a cut-wire sandwiched by two layers of diagonal split-ring resonator (DSRR). The asymmetric transmission property can be realized by rotating the upper and lower DSRR dislocation, and its physical mechanism can be explicated by the Fabry-Pérot-like interference effect. Experimental results are presented and compared to numerical simulations, and they demonstrate that the proposed polarization converter has a significantly polarization conversion ratio over 0.8 in frequency bandwidths 8-11 GHz and 17-21 GHz for the forward and backward incidences. The proposed polarization converter has a great potential to be used as an asymmetric transmission radome or diode-like device in microwave domain.

In this paper, a novel planar waveguide with quasi-TEM mode for periodic structure measurement applications is proposed. Unlike conventional parallel double conductor transmission lines (PDCTL) which suffer from mismatch to 50 ohms, high insertion loss in higher frequency band, the proposed planar waveguide consisting of an F4B substrate, s metal conductor line, and a metal base has easy access to match to 50 ohm through a special transition region and also has a satisfactory insertion loss in a wide band. The metal conductor line etched on one side of the F4B substrate, and the metal base is parallel to mimic a perfect electric wall, where a ``fake'' infinite plane is realized. The proposed planar waveguide has wide measurement bandwidth with the reflection coefficient below -15 dB, which cannot be realized by a standard rectangular waveguide. Good agreements between the simulated and measured results are obtained. In addition, a simple periodic structure is designed as an example. The transmission characteristics of the periodic structure are simulated and compared in two different methods, namely, standard periodic structure simulation method in free space and proposed planar waveguide method. All the measured results demonstrate the validation of our designed planar waveguide, which is convenient and economic for periodic structure measurement applications.