In this work, the influence of human body within the estimation of dosimetric values is analyzed. A simplified human body model, including the dispersive nature of material parameters of internal organs, skin, muscle, bones and other elements has been implemented. Such a model has been included within an indoor scenario in which an in-house 3D ray launching code has been applied to estimate received power levels within the complete scenario. The results enhance previous dosimetric estimations, while giving insight on influence of human body model in power level distribution and enabling to analyze the impact in the complete volume of the scenario.

In this paper, we propose an approach for designing and quantitatively assessing the performance of the multilayered radar-absorbing structure. In our proposed approach, a five layered radarabsorbing materials design is optimized from the predefined materials database. But to determine the optimal choice of the material and thickness of each layer, a combined binary and real-coded genetic algorithm (GA) is used to handle the integer and real variables involved in such designs. Further, the proposed approach employs the Latin hypercube sampling with Monte Carlo Simulation to carry out the performance based reliability analysis of the design. Absorber synthesized results are compared with the published work using other algorithms. The outcomes of our approach show that the combined GA works quite well, and most prominently the reliability analysis provides the decision maker a means to select among the several design alternatives available before him.

In this paper a low cost, high gain, low cross-polar and compact edge feed printed elliptical antenna with a partial ground plane and parasitic patches is proposed and investigated. The proposed antenna is backed by partial ground and parasitic patches. It is fabricated on 1.6 mm thick FR4 substrate with dielectric permittivity of 4.4 and tanδ of 0.025. The total planar area of the proposed antenna (L x W) is 28 mm x 24 mm. Both the simulated and experimental result shows that the proposed antenna provides a frequency range compatible with the ultra-wideband (UWB) standard, i.e., 3.5 GHz-12 GHz frequency band. The radiation pattern produced by the proposed antenna is approximately omnidirectional with in-phase excitation of Surface waves resulting in less cross-polarization level (less than 20 dB) compare to its co-polar component for complete impedance band width. The maximum measured gain for the fabricated antenna is around 6.27dBi with an average efficiency of above 90% throughout the bandwidth. A linear phase response (phase S₂₁) accompanied by a constant group delay of 1ns throughout the measured bandwidth makes the proposed antenna a good candidate for UWB applications.

The classical transmission line theory is expanded to include convection current flow and electromagnetic radiation in unbalanced transmission lines. A theory for the generation of the nonlinear convection current in unbalanced transmission lines is developed. The convection current and the radiation parameters are included in the transmission line equations and a generalized transmission line theory is developed.

Material properties in radio frequency and microwave regimes are limited due to the lack of molecular resonances at these frequencies. Metamaterials are an attractive means to realize a prescribed permittivity or permeability function, but these are often prohibitively lossy due to the use of inefficient metallic resonators. All-dielectric metamaterials offer excellent potential to overcome these losses, but they provide a much weaker interaction with an applied wave. Much design freedom can be realized from all-dielectric structures if their dispersion and anisotropy are cleverly engineered. This, however, leads to structures with very complex geometries that cannot be manufactured by conventional techniques. In this work, artificially anisotropic metamaterials are designed and then manufactured by 3D printing. The effective material properties are measured in the lab and agree well with model predictions.

This paper presents a novel compact microstrip hybrid four-mode bandpass filter (BPF) with good selectivity and multi-transmission zeros. By adding an external resonator to a triple-mode stub-loaded uniform impedance resonator, four modes are generated in the desired passband and a hybrid four-mode BPF is implemented. Even- and odd-mode theory is introduced to investigate the mode characteristics of triple-mode resonator in detail. Circuit model and coupling matrix are built to further explain the proposed methodology. A microstrip BPF with central frequency of 3.4 GHz for wireless communication was designed and fabricated. Three transmission zeros are obtained at 3.2 GHz, 3.55 GHz and 3.73 GHz, which improve selectivity and out-of-band rejection of the filter. The measured results of the fabricated filter represent good in-band and sharp sideband characteristic, which match well with simulated results.

The adaptive linearly constrained minimum power (LCMP) beamformer can improve the robustness of the Capon beamformer. And quadratic constraints on the weighting vector of the LCMP beamformer can improve the robustness to pointing errors and to random perturbations in sensor parameters. But how to solve it and how to select the constraint parameters are its key problems. In this paper, the Lagrange multiplier method is proposed to solve the LCMP beamformer under quadratic inequality constraint (QIC). The problem of finding the optimal weight vector is solved, and the choice of the quadratic constraint parameter is analyzed and the selected bound is also given. Since the quadratic equality constraint (QEC) is stronger than the quadratic inequality constraint (QIC), the performance of the QECLCMP beamformer is more robust than that of the QICLCMP beamformer. Therefore, the QECLCMP beamformer is proposed and is solved effectively. Numerical examples attest the correctness and the efficiency of the proposed algorithms. And the results show that the QECLCMP beamformer has the advantage of overcoming the steering vector mismatch, namely the optimal negative loading has the preferable robustness.

For analyzing the electromagnetic problems with the fine structures in one or two directions, a novel weakly conditionally stable finite-difference time-domain (WCS-FDTD) algorithm is proposed. By dividing the 3-D Maxwell's equations into two parts, and applying the Crank-Nicolson (CN) scheme to each part, a four sub-step implicit procedures can be obtained. Then by adjusting the operational order of four sub-steps, a novel 3-D WCS-FDTD algorithm is derived. The proposed method only needs to solve four implicit equations, and the Courant-Friedrich-Levy (CFL) stability condition of the proposed algorithm is more relaxed and only determined by one space discretisation. In addition, numerical dispersion analysis demonstrates the numerical phase velocity error of the weakly conditionally stable scheme is less than that of the 3-D ADI-FDTD scheme.

In this work, we show how to manipulate the electromagnetic wave at will by using an indefinite medium with extremely strong anisotropy. The negative element in the indefinite permittivity tensor goes to the negative infinity while the positive element is equal to 1, which stretches the hyperbolic equifrequency contour into a straight line type. The direction of the Poynting vector and the wave vector is aligned by the straight line type equifrequency contour along the orientation of the extremely negative permittivity, thus control the wave propagation. The other permittivity of 1 makes the indefinite medium matched with the air. Moreover, because of the hyperbolic equifrequency contour, evanescent wave can also transmit in the indefinite medium under the propagation mode, implying the possibility of controlling an evanescent wave by this special indefinite medium. Simulations are performed to demonstrate the controlling performance and a potential design to realize such a medium by metamaterial with multilayered metal/dielectric structure. This work may supply a shortcut for those former devices based on the Transformation optics.

This paper studies the characteristics of a constant-K lens when considered as a possible substitute for a Luneburg lens in a reflector. The competitiveness of the substitute lens is investigated in its 2D analogue, by comparing the backscattering radar cross section for the range of D/λ ∈ (0, 200). The performance of cylindrical reflectors with either a constant-K lens or a cylindrical Luneburg lens (approximated by a finite number of stepped-index dielectric layers) when illuminated by an electromagnetic plane wave is studied using the semi-analytic Method of Regularization. Because of similar underlying physical principles, these studies provide insight into the 3-D analogue. The radar cross section calculations of the two reflectors for incidence angles varying from normal to grazing incidence show that the cheaper-to-manufacture constant-K lens reflector is able to provide a more powerful and stable backscattering performance than the cylindrical Luneburg lens reflector, for electrical sizes in the range considered.

A convenient method for canceling the parasitic winding capacitance of integrated electromagnetic interference (EMI) filter is proposed. Based on the concept of split ground structure, mutual inductances and structural capacitances can be appropriately utilized to expand the effective frequency range in common mode (CM) noise suppression. Compared with the former approaches, it requires no additional conductor layers or components since the split winding can simultaneously serve for CM capacitance. To demonstrate the parasitic capacitance cancellation mechanism, a simplified equivalent circuit is derived and investigated. Besides, the design procedure with considered structural constraints is presented to obtain the best parasitic capacitance cancellation effect. Prototype of an integrated CM filter with split ground layers is designed and constructed. Experimental results show the split winding can effectively shift the resonance frequency of filter inductor, and hence better filtering characteristics can be achieved.

This paper presents differential-fed patch antennas with excellent cross-polarization. This paper provides a detailed graphic illustration of factors that lead to deteriorated H-plane cross-polarization by the conventional single-ended feeding probes. A novel differential rat-race feeding structure was constructed to allow easy impedance matching. An experimental antenna was realized on low-temperature co-fired ceramic (LTCC) at 8 GHz. An excellent cross-polarization of less than -22.5 dB was achieved. When the operation frequency is high, the parasitic inductance caused by feeding probes may degrade the performance of antennas. This paper further proposes the use of differential aperture-coupled structures at high frequencies. An aperture-coupled antenna, realized at 40 GHz with low cross-polarization <-15 dB has been achieved.

In this paper, a chiral metamaterial (CMM) with complementary U-shaped structure assembly is proposed. The microwave experimental and simulated results of the proposed complementary structure exhibit giant optical activity. The experimental results are in good agreement with the numerical ones. The retrieval results reveal that negative refractive indices for right-handed and left-handed circularly polarized waves could be easily realized due to strong chirality. The mechanism of the chiral behaviors of resonance frequencies will be illustrated by simulated current distributions. Further, the complementary U-shaped structure assembly also exhibits stronger circular dichroism, giant optical activity, and negative index at near-infrared region by simulations.

The electromagnetic susceptibility model of discontinuous microstrip circuits with the presence of a uniform plane incident wave is established. First, the analytical expressions are modeled as equivalent voltage and current sources for discussing the global effect of the incident plane wave on the associated interconnects. Then, these field-induced equivalent source expressions are incorporated into ADS circuit solver, and a fast model is established for analyzing the output responses of discontinuous microstrip circuits, such as the cross bend, the band-rejection filter and the single-stage amplifier. The corresponding simulation results from the proposed model are validated by comparing the results from both simulation and measurement. The results also show that the incident plane wave may influence the output terminal responses significantly, and the proposed approach would be an efficient method to solve the electromagnetic susceptibility problems associated with the discontinuous microstrip circuits.

Radar imaging experiment of ground moving target --- a light rail-way train by Ku-band radar with two receiving channel is introduced. Both coherent and incoherent imaging as well as co-pol and cross-pol interferometric imaging were conducted with SAR amplitude images as well as interferometric --- phase images obtained. In the obtained SAR images, there are 24 stronger scattering centers which correspond to 24 bigger doors of the train. Along-track interferometric --- phase images indicate that the train travels at an increasing speed in one direction and at a decreasing speed in the opposite direction. Short Time Fourier Transform (STFT) is applied to the azimuthal signals to get the instant Doppler frequencies (IDFs), from which one can judge acceleration or deceleration status of the moving train. Electromagnetic scattering characteristics of the train are analyzed according to the SAR images. The estimated speed and length of the train are very well agreed with real situation.

In this paper, an inverse procedure algorithm is proposed in the time domain to evaluate lightning return stroke currents along a lightning channel using measured magnetic flux density at an observation point while the current velocity along a lightning channel is assumed to be a height dependent variable. The proposed method considers all field components and it can evaluate the full shape of currents and the current velocity at different heights along a lightning channel. Moreover, a sample of measured magnetic flux density from a triggered lightning experiment is applied to the proposed algorithm and the evaluated currents and current velocities are validated using a measured channel base current and magnetic flux density at another observation point.

In this paper, a new ultra-wideband (UWB) disc antenna compatible with cognitive radio is presented. The proposed antenna is developed to operate from 0.77 to 11.23 GHz. It consists of a circular disc radiator with a rectangular slot on the patch and the implementation of the bevel technique on the ground plane. A prototype of the antenna has been constructed and shows adequate impedance matching, radiation pattern and gain for cognitive radio applications.

In the field of automatic target recognition and tracking, traditional image metrics focus on single images, ignoring the sequence information of multiple images. We show that measures extracted from image sequences are highly relevant concerning the performances of automatic target tracking algorithms. To compensate the current lack of image sequence characterization systems from the perspective of the target tracking difficulties, this paper proposes three new metrics for measuring image sequences: inter-frame change degree of texture, inter-frame change degree of target size and inter-frame change degree of target location. All are based on the fact that inter-frame change is the main cause interfering with target tracking in an image sequence. As image sequences are an important type of data in the field of automatic target recognition and tracking, it can be concluded that the work in this paper is a necessary supplement for the existing image measurement systems. Experimental results reported show that the proposed metrics are valid and useful.

Localized surface plasmon resonance (LSPR) biosensors are employed to detect target biomolecules which have particular resonance wavelengths. Accordingly, tunability of the LSPR wavelength is essential in designing LSPR devices. LSPR devices employing silver nano-particles present better efficiencies than those using other noble metals such as gold; however, silver nano-particles are easily oxidized when they come in contact with liquids, which is inevitable in biosensing applications. To attain both durability and tunabilty in a LSPR biosensor, this paper proposes alumina (AL2O3) capped silver nano-disks. It is shown that through controlling the thickness of the cap, the LSPR resonance frequency can be finely tuned over a wide range; and moreover, the cap protects silver nano-particles from oxidation and high temperature.

Traditional detection approaches for the dim moving target are addressed under the background of homogeneous sea clutter. However, the realistic clutter commonly appears inhomogeneous, resulting in the low detectability. A heterogeneous multiple-scan detection framework is described in this paper, which combines the inhomogeneous coherent integration in the dwell of single scan and the non-coherent integration of the results from single-scan process across the multiple scans. In the inhomogeneous coherent integration, the Heterogeneous Single-scan Coherent Detector (HSCD) is derived, resorting to the two-step Generalized Likelihood Ratio Test (GLRT) criterion and a hybrid covariance matrix estimation scheme, where the nonhomogeneous Kelly detector and the inhomogeneous Adaptive Matched Filter (AMF) are also considered. Additionally, the Viterbi-Like (VL) algorithm is employed as the noncoherent integration strategy. Finally, the numerical simulations with Monte Carlo method analyze the performance of the nonhomogeneous multiplescan detectors under amplitude and distribution clutter heterogeneity.