A general procedure to evaluate the electromagnetic fields generated by moving seawater through the geomagnetic field is proposed. It contains two essential steps: modeling of velocity vector of seawater according to its dynamic mechanism, and solution of Maxwell equations under a stratified ocean configuration. Two kinds of motions are considered in this work, wind-driven waves and wakes due to a moving body. The ocean is taken to be infinitely deep at the moment. Both the velocity vector and magnetic field are expressed as a superposition of sinusoidal waves. Simulation results show that the magnetic fields produced by moderate wind waves or a middle-size body moving at moderate speed are on the order of one hundred pico-Tesla near the sea level. The spectrum characteristics of the two kind magnetic anomalies are distinct.

A novel and simple dual-band dual-sense circularly polarized (CP) metal-strip antenna is proposed. The antenna fed by a coplanar waveguide (CPW) with the advantages of uniplanar geometry and easier fabrication consists of a square slot and two split-ring elements. By appropriately introducing dual split-ring elements, the proposed dual-band CP design can easily be achieved. The two resonant frequencies are controlled by the size of the two split-ring elements. The proposed antenna prototype is fabricated and measured. Experimental results show that good CP radiation performances are obtained at both resonant frequencies. The proposed antenna has an impedance bandwidth (|S₁₁|≤-10 dB) of 63.3% (2.0~3.9 GHz), and the dual band circular polarization with left hand circular polarization (LHCP) at 2.2 GHz and the right hand circular polarization (RHCP) at 3.8 GHz are obtained. Also, the 3-dB axial ratio bandwidths are about 220 and 190 MHz at the lower and upper band, respectively.

Electromagnetic wave absorption inside a human body is investigated. The human body has been modeled using 3D voxel based dataset considering different electrical parameters. At GSM 900 band, Specific Absorption Rate (SAR) induced inside the human body model exposed to a radiating base station antenna (BSA) has been calculated for multiple number of carrier frequencies and input power of 20 W/carrier. Distance (R) of human body from BSA is varied in the range of 0.5 m to 5.0 m. Values of whole-body average SAR obtained by hybrid FDTD method closely match with that obtained by SFDTD method. For number of carrier frequency equal to five and R = 0.5 m, maximum value of whole-body average SAR obtained by both hybrid FDTD and SFDTD method is found to be 0.69 W/kg which decreases either with increase of R or decrease of number of carrier frequencies. Safety distance for general public is found to be 1.5 m for number of carrier frequencies equal to five. Summary of performance comparison shows that hybrid FDTD method is faster and requires less memory than SFDTD method.

This paper is devoted to the study of beam-wave interaction behavior of a 35 GHz photonic band gap cavity (PBGC) gyrotron operating in a higher order TE₃₄₁ mode. For the present gyrotron, PBGC is used instead of conventional tapered cylindrical cavity due to its promising feature of the mode selectivity. In order to observe the beam-wave interaction behavior, multimode theory has been used for the PBG cavity operating at the fundamental harmonic mode. Multimode theory provides the performance of a gyrotron in the presence of all competing modes. Results obtained from the analysis have been validated using a commercially available 3D PIC code. The energy and phase variations of electrons demonstrate the bunching mechanism as well as energy transfer phenomena. RF power output obtained from the analysis as well as PIC simulation is compared and is found in close agreement within 12%. More than 45 kW of stable RF power output is achieved in TE₃₄₁ mode with ~17% efficiency. The existence of competing modes has been considerably reduced, and the single mode operation of PBGC gyrotron has been achieved.

Tracing the dynamics of electrons inside atoms molecules or solids as they occur in real time resides at the forefront of modern science and technology. Advances in attosecond physics over the last decade and beyond are now enabling this essential experimental capability. Here we discuss some of the key developments in light sciences that made possible attosecond metrology and control of electronic processes inside matter on native time scales. These developments hold the promise for new, fundamental insights into the innerworkings of the microcosm as well as the identification of innovative routes for light-based electronic and photonic devices operating at PHz rates.

The paper is devoted to the theory of eigen electromagnetic waves propagating across the axis of symmetry in waveguides with a non-circular cross-section. The case of waveguides filled with isotropic cold plasma is studied theoretically. Plasma particles motion is described in fluid approximation; expressions for the waves' fields are derived from Maxwell equations. Cross-section of the studied waveguide is modeled by Fourier series with coefficients, which values are less than unity. This allows one to apply method of successive approximations for analytical research of this problem. Boundary conditions, which are formulated in non-linear form over the small parameters of the problem have been applied for derivation the dispersion equations, which determine frequency spectrum of these surface waves for waveguides of different constructions. Studied eigen electromagnetic waves propagate in the form of wave packets, which are approximately described by the main azimuthal harmonic and two nearest satellite spatial harmonics. Represented results have been obtained both analytically and numerically. Possible spheres of the studied eigen waves are discussed.

An ultra-wideband (UWB) bandpass filter (BPF) with hybrid coplanar waveguide (CPW)/microstrip structure is introduced in this paper. Then a pair of lowpass filters is integrated on the CPW feed lines to achieve a good out-of-band rejection. At last, a notched band with two transmission zeros is realized at 5.8 GHz by using a symmetric E-shaped slot-line and etching slots on microstrip resonator. Two transmission zeros are realized in the desired notched band, and out-of band rejection is more than 32 dB. In order to prove the validity, the proposed filter is fabricated and measured, and the measured results are in good agreement with simulated ones.

The near-field scattering characteristics of rough target are analyzed by using a revised bidirectional reflectance distribution function (BRDF) of a rough surface based on least squares support vector machine (LS-SVM). The revised BRDF is more reliable in a larger range of incident angles and scattering angles that beyond the scope of experimental measurements. The basic principle of LS-SVM and the modeling process are firstly introduced in detail. Then the comparison among LS-SVM, the back propagation neural network (BPNN) and the measured data is carried out．The results show that the LS-SVM model has better integrative performance, stronger generalization ability and higher precision. On this basis, the calculation of the near-field radar cross section (RCS) of a complex target is safely performed and analyzed. The method proposed is helpful to better investigate the near-field scattering characteristics of rough target.

Electromagnetic imaging is based upon the fundamentals of electromagnetic (EM) fields and their relationship with the material properties under evaluation. A new system based on a Giant Magneto-Resistive (GMR) sensor array was built to capture the scattered EM signal returned by metallic objects. This paper evaluates the new system's capabilities through the classification of metallic objects based on features extracted from their response to EM fields. A novel amplitude variation feature as well as the combinations of typical features is proposed to obtain high classification rates. The selected features of metallic objects are then applied to well-known supervisedclassifiers (ANN and SVM) to detect and classify `threat' items. A collection of handguns with other commonly used metallic objects are tested. Promising results show that a high classification rate is achieved using the proposed new combination features and classification framework. This novel procedure has the potential to produce significant improvements in automatic weapon detection and classification.

Electromagnetic band gap (EBG) structures are usually realized by periodic arrangement of dielectric materials. These periodic structures can help in the reduction of mutual coupling in array antennas. In this paper a new arrangement of EBG structures is presented for reducing mutual coupling between patch antenna MIMO arrays. The patch antennas operate at 5.35 GHz which is defined for wireless application. Here 2×5 EBG structures are used to reduce mutual coupling more than 20 dB. The total size of the antenna is 36 mm×68 mm×1.6 mm. So it is more compact in than pervious research. Experimental results of return loss and antenna pattern have been presented for 5.4 GHz and compared with HFSS simulation results. Also the EBG structures have been designed with numerical modeling and dispersion diagram. New EBG model is compared with conventional EBG model, and equivalent circuit model is given for new structure.

In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for tri-band WLAN/WiMAX applications is presented. The proposed antenna is composed of a simple monopole with the high resonant mode at 5.8 GHz, an open-ended slot embedded on the ground plane with the low resonant mode at 2.4 GHz, and a meander trip shorted to the ground with the middle resonant mode at 3.5 GHz. The three resonance frequencies of the antenna can be controlled by adjusting the geometries and the sizes of the monopole, the slot and the strip. The antenna occupies a very compact size of 22×12 mm² including the ground plane, has nearly omnidirectional radiation characteristics and reasonable gain in the operating bands. The simple feeding structure, compactness and uniplanar design make it easy to be integrated within the portable device for wireless communication.

In many ways light and nanoscience do not mix well. By convention light can be focussed to a spot no smaller than about a micron whereas nano structures by definition are three orders of magnitude smaller in scale. However recent theoretical advances show how to control light at the nanoscale, provided we can find the correct materials for our devices. I shall describe these new theories, and how they enable us to concentrate light to better than a nanometre. In this way light can detect single molecules, and the huge concentrations of optical energy can force photons to interact with one another which they normally do not do.

The finite-difference frequency-domain (FDFD) method is a very simple and powerful approach for rigorous analysis of electromagnetic structures. It may be the simplest of all methods to implement and is excellent for field visualization and for developing new ways to model devices. This paper describes a simple method for incorporating anisotropic materials with arbitrary tensors for both permittivity and permeability into the FDFD method. The algorithm is benchmarked by comparing transmission and reflection results for an anisotropic guided-mode resonant filter simulated in HFSS and FDFD. The anisotropic FDFD method is then applied to a lens and cloak designed by transformation optics.

For the measurement of microwave device in high-power, traditional methods are inefficient, inaccurate and not on-line real-time measurement. A new type of high-power microwave impedance tuner (26.5 GHz~40 GHz) based on load-pull technique and a corresponding rapid calibration method based on curve fitting are proposed. A new structure using increased width rectangular waveguide slotted in the center is adopted as the main transmission line. In order to prevent the leak of electromagnetic waves transferring in rectangular waveguide, two choke grooves are added in upper cover plate of the waveguide cavity. The results (standing wave ratio range of 1.02~10.98, insertion loss of 0.063 dB at minimum standing wave ratio) show by practical measurement that this structure and method are feasible. The device can meet the requirement of design, and the new method has less time for calibration.

This paper provides a modified formula for calculating dielectric loss of dielectric resonator of working in TE_01δ mode in closed cavity. The measurement system is divided into six regions with all electromagnetic field distributions given in each region. Based on analyzing the formula of loss tangent published in literatures, a quality factor of a substrate is created, and a modified formula is proposed. Validating the modified formula, with three substrates as supports, the frequencies and unloaded quality factors of dielectric resonators made of two sorts of dielectric materials with permittivity 38 and 75 respectively are measured using a closed cavity method. The measured results are compared with those obtained by other well-known formulas and show a good agreement with the result given by the parallel plate method.

Inverse synthetic aperture radar (ISAR) imaging is an effective method to identify unknown targets regardless of weather and illumination conditions. Research results published regarding this topic have focused mainly on imaging and automatic target recognition (ATR) of single targets. However, targets generally fly in formation, so the applicability of ISAR images to ATR of multiple targets must be studied. This paper proposes an ATR procedure for targets flying in formation. ATR accuracy derived using five targets composed of point scatterers and the measured radar signal of a Boeing747 aircraft was as high as that of the solo flight in terms of SNR and the size of the training database; this result shows that ISAR is an adequate tool for ATR even if an image is contaminated by radar reflections from neighboring targets.

This paper presents a novel power divider with filtering responses. By using quarter-wavelength resonators with a novel feeding structure, both power division and bandpass responses are obtained, and compact size is realized. Discriminating coupling is utilized to suppress the third harmonic to obtain wide stopband. The isolation resistor is connected at two ends of the input feed line, and good isolation is obtained. Two transmission zeros are generated at two edges of the passband, resulting in high selectivity. For demonstration, a filtering power divider is implemented. Comparisons of the measured and simulated results are presented to verify the theoretical predications.

The transmission and reflection coefficients of electromagnetic waves propagating through the finite periodically layered chiral structure are defined both theoretically (using the propagation matrix method) and experimentally. The coefficients of the propagation matrix of the periodically layered chiral medium are obtained. The boundaries of the forbidden bands for a periodic medium, whose unit cell consists of two different chiral layers were determined. It is shown that the boundaries of the forbidden bands do not depend on the chirality parameter of the layers. It is found that for certain values of the layers thicknesses, the forbidden band widths tend to zero and that the proposed method for calculation of the reflection and transmission coefficients can be used to determine the effective constitutive parameters of artificial chiral metamaterials. The transmission and reflection coefficients of plane electromagnetic waves propagated through the finite periodically layered chiral structure were determined experimentally for 20-40 GHz range. A good agreement between the experimental results and theoretical studies of the forbidden band spectrum for the structure under research has been shown.

A multimode collocated microstrip patch antenna with reduced mutual coupling is proposed in this paper. The antenna is designed to achieve polarization and pattern diversity for use in multiple-input-multiple-output (MIMO) terminals. The four-port antenna resonates at 2.45 GHz and have total dimension of 1.03λ with reduced mutual coupling (< -20 dB) between its ports. It consists of a simple square patch and a square ring antenna, with a novel square ring slot defected ground structure (DGS). Square ring slot on ground improves isolation by 7 dB by reducing surface waves in both E and H planes. With defected ground structure (DGS), coupling between patch and ring antennas is about -25 dB and correlation factor is less than 0.1. Pattern diversity, mutual coupling and correlation coefficient between signals for a four-port antenna fabricated using FR4 substrate is discussed in this paper.

As the boundary of the universe which is explored by human expanded, antenna used in deep space exploration (DSE) could become too large to carry and deploy, miniature deep space probe based antenna arrays (MDSPBAA) provide a novel solution for the problem. This kind of antenna array may lower the difficulty of sending antenna to the area where is tend to be detected and may also monitor cost effectively in the work of deep space detect. However, turbulence and positional errors provide a challenging operational environment when it comes to the implementation of these systems. Turbulence will deteriorate SLL badly. In some cases, the level could be changed by almost 10 dB. Therefore, a SLL control algorithm is presented, which could well compensate the SLL which is caused by positional error.