In this paper, a fast time domain imaging algorithm called bistatic forward-looking fast factorized backprojection algorithm (BF-FFBPA) based on sub-aperture and sub-image is proposed for general bistatic forward-looking synthetic aperture radar (BFSAR) with arbitrary motion. It can not only accurately dispose the large spatial variant range cell migrations and complicated motion errors, but also achieve high imaging efficiency. First, the imaging geometry and signal model are established, and the implementation of backprojection algorithm (BPA) in the BFSAR imaging is given to provide a basis for the proposed BF-FFBPA. Then, considering motion errors, the more accurate requirements of splitting sub-aperture and sub-image in the BF-FFBPA is introduced based on the range error analysis to offer the tradeoff between the imaging quality and efficiency. Finally, the implementation and computational burden of the BF-FFBPA is provided and analyzed. Simulated results and evaluations are given to prove the correctness of the theory analysis and the validity of the proposed approach.

An efficient and accurate hybrid model has been developed for the electromagnetic leakage from two apertured cascaded metallic rectangular enclosures connected by a metallic plate with an aperture covered by a non-magnetic conductive sheet excited by an electric dipole located in the enclosure. The leakage fields through the covered aperture are derived by using the dyadic Green's function and employing the approximate boundary conditions at both sides of the sheet which is regarded as an infinite conductive plate. Then, the leakage fields into the external space through the aperture regardless of its thickness at the end of the enclosure are derived based on a generalization of the method of moments (MoM). Finally, the shielding effectiveness (SE) at the target points outside the enclosure is calculated for the intermediate analysis of the leakage fields. Comparison with the full wave simulation software CST has verified the model over a wide frequency band. The hybrid model then is employed to analyze the effect of different factors including the thickness and the conductivity of the conductive sheet on the SE, and the corresponding physical mechanisms of the leakage fields are also illuminated. The hybrid model can also be extended to deal with other cases, including the whole plate made of non-magnetic conductive material without apertures, the infinite thickness of the aperture at the end of the enclosure, and the aperture at the end of the enclosure is also covered by a non-magnetic conductive sheet.

The analysis of the electromagnetic scattering from perfectly electrically conducting (PEC) objects with edges and corners performed by means of surface integral equation formulations has drawbacks due to the interior resonances and divergence of the fields on geometrical singularities. The aim of this paper is to show a fast converging method for the analysis of the scattering from PEC polygonal cross-section closed cylinders immune from the interior resonance problems. The problem, formulated as combined field integral equation (CFIE) in the spectral domain, is discretized by means of Galerkin method with expansion functions reconstructing the behaviour of the fields on the wedges with a closed-form spectral domain counterpart. Hence, the elements of the coefficients' matrix are reduced to single improper integrals of oscillating functions efficiently evaluated by means of an analytical asymptotic acceleration technique.

A procedure is reported to determine accurate, invertible, block-diagonal factorizations for matrices obtained by discretizing integral equation formulations of electromagnetic interaction problems. The algorithm is based on the combination of localizing source/receiver transformations with orthogonally matched receiver/source transformations. The resulting factorization provides a single, sparse data structure for the system matrix and its inverse, and no approximation is required to convert between the two. Numerical examples illustrate the performance of the factorization for electromagnetic scattering from perfectly conducting elliptical cylinders of different electrical size.

The utilization of an open-ended coaxial probe for characterization of dielectric properties or quantitative nondestructive detection of defects in materials firstly requires evaluating the aperture admittance. For the case that the probe is terminated into low-loss dielectrics backed by a conducting sheet, however, the admittance expression encounters poles in the vicinity of the path of integration, resulting in low convergence rate or even overflow in numerical quadrature. In this study, locations and properties of the singularities of the integral formulation for generally lossy, low-loss, and lossless dielectric slabs backed by a perfectly conducting sheet are investigated above all. Subsequently, making use of the contour integral technique, a fast and stable integration method is put forward to calculate the admittance integral formulation. Finally, numerical experiments are conducted to justify the validity and efficiency of the proposed integration method for low-loss dielectric cases by comparison with the traditional integration method as well as commercial FEM software.

Electrical conductivity imaging in the human body is usually pursued by either electrical impedance tomography or magnetic induction tomography (MIT). In the latter case, multiple coils are almost always used, so that nonlinear reconstruction is preferred. Recent work has shown that single-coil, scanning MIT is feasible through an analytical 3D convolution integral that relates measured coil loss to an arbitrary conductivity distribution. Because this relationship is linear, image reconstruction may proceed by any number of linear methods. Here, a direct method is developed that combines several strategies that are particularly well suited for inverting the convolution integral. These include use of a diagonal regularization matrix that leverages kernel behavior; transformation of the minimization problem to standard form, avoiding the need for generalized singular value decomposition (SVD); centering the quadratic penalty norm on the uniform solution that best explains loss data; use of KKT multipliers to enforce non-negativity and manage the rather small active set; and, assignment of the global regularization parameter via the discrepancy principle. The entire process is efficient, requiring only one SVD, and provides ample controls to promote proper localization of structural features. Two virtual phantoms were created to test the algorithm on systems comprised of ~11,000 degrees of freedom.

A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna based on dual concentric, orthogonal slot split ring resonators is proposed and experimentally studied. The circularly polarized wave is generated by two split ring-slots etched in the upper metal layer of the SIW cavity resonator. These two slots are excited by a coaxial probe located in the gap of the external slot split ring to radiate the right-handed circularly polarized (RHCP) wave. By rotating the dual split slot ring resonators and the probe by 45 degreesrelative to the backed cavity, a better match characteristic and a slightly higher radiation gain are obtained. Because of theconcentricity of radiant split ring slots, the beamwidth of the circular polarization is obviously increased.From the experimental results, the impedance bandwidth was 10.8% for the reflection coefficient less than -10 dB, the axial ratio (AR) bandwidth was 1.54% for the AR less than 3 dB, and the RHCP gain was 4.44 dBi. Moreover, the 3-dB axial ratio beamwidth at the centre frequency of 10.40 GHz has been extended to 142° in the angular range from -78° to +64°.

There is growing interest in the use of nanocomposites based on carbon nanotubes (CNT) due to their excellent mechanical, thermal and electrical properties. The electromagnetic characteristics of nanocomposites with different types of multi-walled carbon nanotubes were investigated. CNTs with different geometries (length and diameter) were chosen in order to analyze the effect of the geometrical parameters on the electromagnetic properties. Nanocomposites with various percentages of CNT were made and the number of CNTs per cm³ in the composite was computed. CNTs were characterized by Field Emission Scanning Electron Miscroscopy (FESEM) and Raman spectroscopy. The complex permittivity of the NCs was measured with two different techniques, and the variation of the permittivity with the number of CNT per cm³ was investigated.

Coplanar monopole antennas printed using copper oxide nanoparticles on flexible substrates are characterized in order to study the effect of the ink drop spacing on the antenna parameters. Polyethylene Terephthalate and Epson paper were the chosen flexible substrates, and the antennas were designed to operate at 20 GHz. A maximum conductivity of 2.8×10⁷ Ω⁻¹m⁻¹ was obtained for the films printed on Polyethylene Terephthalate using a drop spacing of 20 μm. The corresponding antenna achieved a gain and an efficiency of 1.82 dB and 97.6%, respectively. Experiments showed that smaller drop spacings lead to bulging of the printed lines while the antenna performance worsens for longer ones. At the same drop spacing, antennas printed on Epson paper substrate showed a -10 dB return loss bandwidth which extended from 17.9 GHz to 23.3 GHz, leading to a fractional bandwidth of 26.0%.

A finite difference method in the frequency domain is evaluated to clarify characteristics of the Lorentz force exerted on a metal nanoscale particle by light irradiation. Numerical results are compared with exact values obtained from Mie theory to show that applying a smoothing algorithm to the surface of a nanoparticle increases the accuracy of the simulation. Analysis of the Lorentz force exerted between two spheres aligned closely indicates that strong forces cause the spheres to attract each other at the plasmon resonant frequency. It was also noticed that application of the smoothing algorithm was indispensable in order to achieve the above result.

In this paper, an antenna with reconfigurable radiation pattern in the H-plane at 2.45 GHz for high power applications is presented. It is based on a 3 slots array in the E-plane covered partially with a wall of plasma in order to reduce the length of the slots and consequently ensure electrically a modification of the radiation pattern in the H-plane. The power distribution of the array is ensured with a power splitter.

A mathematical model of a large rectenna array (LRA) is presented. It is shown that matrices describing the LRA linear subsystem have a number of specific features that must be considered when the rectenna mathematical model is developed. The state equation for the LRA was obtained. It is shown that the model functioning in nonlinear mode of the infinite rectenna array can be reduced to finding the parameters of one equivalent receiver-rectifier element (RRE) at the fundamental frequency and its harmonic. The external parameters of the RRE and LRA characteristics were obtained.

In this paper the results of the estimated electric field associated with tortuous lightning paths at close distance (50 m to 500 m) are shown. Such results are compared with experimental data available in the literature and are illustrated along with a quantitative analysis of the field waveforms and their frequency spectra. The limits of the usual straight-vertical channel assumption and the influence of tortuosity at different azimuth and distances from the lightning channel base are also highlighted.

A novel single-layer unit cell structure is proposed to design a dual-band dual-linear-polarization reflectarray antenna with different beams for X and Ku bands. The unit cell structure is composed of a circular ring and two cross bow-tie structures combined by a circular patch. Five tunable geometric parameters can be optimized to achieve the required phase distributions of the reflectarray antenna with independent radiation patterns for each band which is a challenge for single-layer linearly polarized reflectarrays. Besides, the proposed unit cell structure has the ability to meet the demand of dual-polarization applications. A 301-element center-fed reflectarray with an octagon-shape aperture operating at X and Ku bands is designed, manufactured and measured to verify the dual-band performance of the proposed unit cell. The measured results show that the object of achieving different beams at different frequencies is realized with good radiation patterns at both designed frequencies. Besides, the similar radiation patterns for both linear polarizations are also achieved at both bands.

In this paper, a three-layered chiral metamaterial composed of three twisted split-ring resonators is proposed and investigated. The simulated and measured results show that the proposed metamaterial can achieve efficient asymmetric transmission of linearly polarized wave and cross-polarization conversion for two distinct bands: X (6.95-10.05 GHz) and Ku (15.55-18.47 GHz). In the X-band, an incident y-polarized wave is almost converted to a x-polarized wave, while an incident x-polarized wave is completely blocked from passing through the structure. In the Ku-band, an incident x-polarized wave is almost converted to a y-polarized wave, while an incident y-polarized wave is blocked from passing through the structure. Moreover, the simulated and measured results confirm that the proposed metamaterial has a good robustness to misalignment, which provides convenience for fabricating in practical applications. Finally, the physical mechanism of this dual-band asymmetric transmission effect can be explained based on the different resonant modes of the proposed structure.

This paper presents the design and implementation of dual-band filters. The proposed method works well for dual-band filters with asymmetric dual-passband, high selectivity, and pre-assigned in-band return loss levels (e.g. equal or un-equal at two frequency bands). To verify the design concept, a prototype dual-band filter using combline coaxial cavity-type resonators was designed, fabricated and tested. Good agreement has been achieved among the theoretical synthesis results, simulation results and measurement results.

The possibility of employing highly-elliptical-orbit (HEO) satellites for SAR imaging is investigated. A constellation of two satellites in the Tundra orbits, which are capable of covering all the high-latitude areas, are chosen as the platforms for SAR imaging. The received signals are processed with an improved frequency-domain algorithm (FDA) to reconstruct the image. Simulation results verify that the proposed method can produce better SAR images with less computational load and memory than the conventional FDA.

A metal-insulator-metal (MIM) plasmonic waveguide coupled with two nanodisks as a resonator has been examined and numerically simulated with the finite-difference-time-domain (FDTD) and analytically by the Temporal Coupling Mode Theory (CMT). Based on the three-level system, the strong destructive interference between the two resonators leads to the distinct mode splitting response. The characteristics of mode splitting show that there is anomalous dispersion with the novel fast-light feature at the resonance. Meanwhile, the slow light characteristic can also be achieved in the system at wavelengths of the split modes. The relationship between the transmission characteristics and the geometric parameters is examined. The results show that the modulation depth of the mode splitting transmission spectrum of 80% with 0.175 ps fast-light effect of resonance can be achieved, while for the two modes these values are around 30% with -0.18 ps slow light-effect can be achieved. There is a good agreement between the FDTD simulated transmission features and CMT. The characteristics of the system indicate critical potential applications in integrated optical circuits such as slow-light and fast-light devices, optical monitoring, an optical filter, and optical storage.

In this paper, a 79 GHz microstrip antenna subarray, optimized for operation in a Phase Modulated Continuous Wave (PMCW) MIMO radar demonstrator is presented. The antenna combines all necessary features for this very specific type of applications. First of all, the spillover between transmit and receive channels in such a system is reduced by the combined effect of a microvia cage and the arraying of two elements. Second, it shows a wide band of 13.5%. Third, a wide beam in the E-plane (136 degrees), necessary for scanning, and a much smaller beamwidth in H-plane (36 degrees), advantageous to reduce mutual coupling, are realized. Finally, it has been fabricated with the advanced so-called ``Any-Layer'' technology. This technology is as accurate as other advanced technologies in the millimeter wave bands, but at a much lower cost, and thus very suited for mass production. The gain and radiation efficiency were simulated to be 7.27 dBi and 83%, respectively.

We aim to estimate the average dielectric properties of centimeter-scale volumes of biological tissues. A variety of approaches to measurement of dielectric properties of materials at microwave frequencies have been demonstrated in the literature and in practice. However, existing methods are not suitable for noninvasive measurement of in vivo biological tissues due to high property contrast with air, and the need to conform with the shape of the human body. To overcome this, a method of antenna calibration has been adapted and developed for use with an antenna system designed for biomedical applications, allowing for the estimation of permittivity and conductivity. This technique requires only two calibration procedures and does not require any special manufactured components. Simulated and measured results are presented between 3 to 8 GHz for materials with properties expected in biological tissues. Error bounds and an analysis of sources of error are provided.