The eikonal equation for inhomogeneous anisotropic metamaterials with equal relative permittivity and permeability tensors (ε(r) = μ(r)) is derived from a free boundary variational principle. An original approach is proposed considering the wavefront as a moving discontinuity surface in an extended continuous media described by the Lagrangian density of electromagnetic fields. The eikonal equation arises as natural (non prescribed) boundary conditions for variational problems.

As we all know, traditional transmission electromagnetic pulse simulator has restricted test space problem. This paper proposes a new directed radiation fast rising time electromagnetic pulse (FREMP) simulator scheme which is based on transverse electric magnetic (TEM) wave antenna of a wire edge curl structure. Through numerical simulation, we study the influence of the parameters of wire edge curl TEM horn antenna and the effect of absorption resistance on radiation field. The simulation results show that the wire edge curl TEM horn antenna can effectively improve the ability of low frequency radiation. It can provide a theoretical support for developing FREMP simulator. We also demonstrate the feasibility of developing FREMP simulator using wire edge curl TEM horn antenna through experiments. Finally, the experimental results show that the radiation field of FREMP simulator developed by wire edge curl TEM horn antenna can meet high-altitude nuclear electromagnetic pulse (HEMP) requirements.

An improved mutual coupling calibration approach based on the element pattern reconstruction (EPR) method is proposed in this paper. Compared to previous calibration methods in which the calibration is carried out in the entire space, the space angle ranges to be calibrated in this method is partitioned according to the interested directions. Through the partition of the space angle region, the angle ranges to calibrate are narrowed, and thus more accurate calibration matrix can be obtained in corresponding angle regions. With the employment of the calibration matrix on 2-D DOA estimation, more effective mutual coupling calibration and more accurate DOA estimations are achieved by alternate iteration in each angle region. The validity of this method is verified by an L-shaped microstrip antenna array, and the performance of mutual coupling calibration is presented by the better accuracy in 2-D DOA estimations.

A new formulation of the Wave Concept Iterative Process (WCIP) method is presented in this work. This approach uses an analysis with the longitudinal components instead of the transverse components. This approach includes decomposing the transverse TM modes into two longitudinal terms: the TM and TEM modes. This approach is applied to model a Vertical Interconnect Access VIA hole. The current density behavior is studied in the two cases with and without VIA hole. Also this method is used to study a SIW slot antenna. Compared to those obtained by available published data, our results show that the proposed method gives convincing results.

A terahertz (THz) antenna is proposed that offers high input resistance and gain in the presence of an electrically thick GaAs substrate. The antenna is centrally fed using two vertical probes connected to a photomixer on a thin low temperature grown gallium arsenide (LTG-GaAs) film which is supported by the GaAs substrate. An input impedance of ~3.3 kΩ has been achieved using a dipole antenna that is printed on a thin dielectric slab, and isolated from the supporting substrate using a metal ground plane. A square aperture has been introduced to facilitate the illumination of the photomixer with two laser beams. Furthermore, a frequency selective surface (FSS) has been incorporated in the configuration, which results in a broadside gain of ~19 dBi at a resonance frequency of 0.97 THz.

In this paper, a frequency-domain-based transient electromagnetic model of grounding system in horizontally stratified multilayer medium is presented. The basis of the model is an improved version of the time-harmonic electromagnetic model of grounding system. Using the originally developed continuous numerical Fourier transform algorithm, the results obtained by the time-harmonic model are synthesized into a complete time domain solution. The presented model features very high accuracy and fast execution speed and is validated through several numerical examples.

εThis paper presents an analytical solution to study the reflection and transmission of an electromagnetic wave impinged upon a multilayered structure. The structure is composed of a fractal slab sandwiched by ordinary material on either side. Modified Maxwell equations for fractional dimension space are used to represent the fields in a fractal slab. The electromagnetic characteristics of the structure are studied for different dimensions (D) and numerical results are presented for both the classical (D is integer) and fractal (D is non-integer) slabs. This study provides foundations for investigating the waveguides filled with fractal media and electromagnetic waves propagation in multilayered structures at fractional boundaries.

In this paper, the problem of RCS reduction in cylindrical structures with various boundary conditions are investigated comprehensively. It has been done through a general form of boundary conditions called Mixed-Impedance boundary conditions. Genetic algorithm, a powerful optimization method, is used to explore specific conditions that provide major reduction of cylindrical structure's RCS. The optimizations are performed in case of normally and obliquely incident illuminations. Finally, the optimized values are formulated in terms of incident angle to construct a simple and fast way of evaluation of the minimum RCS situation. The results are compared with a cylindrical PEC structure, and it has been verified that the optimized values of MI boundary conditions could result in significant backward RCS reduction for both normal and oblique incident.

A novel microstrip bandpass filter with four transmission zeros is proposed. Four transmission zeros close to the passband are realized to improve the selectivity for the passband. A sixth-order passband is realized with two shorted stubs and a dual-mode ring resonator. The transmission zeros near the passband can be adjusted conveniently by only changing the characteristic impedances of the coupled lines. For demonstration, a planar bandpass filter (3-dB bandwidth 21.9%) was designed and fabricated.

A novel log-periodic dipole antenna for dual-polarized radar systems is presented. The proposed antenna employs meander line technology and matched loads. The simulated and measured results show that the -6 dB reflection coefficient bandwidth of the dual-polarized antenna covers the desired band of 2-8 GHz and the port isolation is higher than 32 dB, along with -20 dB cross-polarization discrimination for both E- and H-planes.

This paper presents the transmission line analysis, thermal and structural analysis of a multi-section coaxial coupler (MSCC) used in traveling-wave tubes (TWTs) to handle high average power over a wide frequency range. Power transmission through coupler from the device demands very good matching between load and source impedances such that low VSWR is achieved. Modeling of the MSCC for wideband TWTs in commercially software packages takes very long iteration time even in high-end computers. An analytical approach has been developed to model MSCC which takes less iteration time even in ordinary computer. Analytical results have been compared to those obtained from CST microwave studio. Finally, thermal and structural analysis has been carried out to study the thermal aspects for handling high average RF power.

A compact microstrip notched ultrawideband patch antenna (UWB) with inverted E- and F-shaped slots is presented. By introducing a new inverted E-shaped notch in the radiating plane, band-notch about 2.68 to 3.55 GHz is achieved. A new type of Defected Ground Structure (DGS) in the ground plane is employed to extend the lower limit of the bandwidth so as to cover ISM 2.4 GHz WLAN-frequency band. The proposed antenna offers 126% bandwidth overall dimension of 13×17×1.6 mm³. The experiment results indicate that the proposed antenna can meet the requirement for UWB communication with size miniaturization.

A systematic procedure is presented for synthesis of generalized Chebyshev lossy bandstop filters with nonparaconjugate transmission zeros. From a lossy scattering parameters with the prescribed reflection zeros, the transformation formulas from the scattering matrix to the admittance matrix are obtained by reconstructing the non paraconjugate transmission zeros as paraconjugate ones. The canonical transversal array is modeled by partial fraction expansion of the normalized admittance functions, resulting in an increased order of the final network provided there are nonparaconjugate transmission zeros. The methods are simpler and more general than the ones in the literature. So it shows great versatility, and can also accommodate lossless network or a transfer function with symmetrical transmission zeros. To illustrate the proposed synthesis procedure, three typical examples have been carried out to validate the synthesis method.

General dispersion equation is obtained at arbitrary inclination angles of the external magnetic field and wave vector of an incident EM wave. Statistical characteristics of the phase fluctuations of scattered high frequency EM waves in the collision magnetized plasma caused by electron density and external magnetic field fluctuations taking into account polarization coefficients for both ordinary and extraordinary waves are calculated analytically. The influence of collision frequency, anisotropy factor and angle of inclination of prolate irregularities of electron density fluctuations with respect to the geomagnetic field of lines on the broadening of the spatial power spectrum is analyzed. Phase portraits of the phase fluctuations caused by the geomagnetic field fluctuations are constructedat different spatial parameters characterizing magnetic field and electron density fluctuations. Numerical calculations are carried out for the ionospheric F-region parameters using experimental data.

A novel technique for extrapolation of transient response using early-time and low-frequency data is proposed in this paper. An improved extrapolation scheme using approximate prolate series is presented to obtain a transient electromagnetic response. The approximate prolate series, which has an approximately band-limited and sub-domain nature, is a better choice for extrapolating the time-domain electromagnetic response than orthogonal polynomials, such as Laguerre functions and Hermite functions. A novel regularization method based on truncated generalized SVD is also proposed to solve the ill-posed extrapolation problems, which make the extrapolation technique much less sensitive to noise in the known part of the response. Some numerical results are presented to illustrate the effectiveness and accuracy of the proposed method in extrapolation of transient electromagnetic problems.

An effective technique utilizing neutralization lines to increase the isolation of a compact two-element dual-frequency microstrip antenna array is proposed in this paper. Two neutralization lines connect the two elements at the edge of each radiating patch. The positions and lengths of the two neutralization lines are studied to get the best performance of element isolation. A prototype of the proposed design was fabricated to validate the results. The measured results agree well with the simulated ones. It is shown that an increase of about 25 dB at the lower frequency and that of 17 dB at the upper frequency in isolation between the two antennas have been achieved.

This paper proposes a hybrid multichannel processing method for spaceborne Hybrid Phased-MIMO SAR (HPMSAR) that can achieve different applications of multi-direction swath imaging on the same platform. The method is optimal because it is a combination of two-dimension (2-D) advanced digital beamforming (DBF) technology and multichannel pre-filter technology for high-resolution wide-swath SAR signal processing. Multichannel signal processing technology for future spaceborne SAR will no longer be single and this combination may be the best choice. The proposed method could avoid spectrum aliasing caused by low pulse repetition frequency (PRF), separate the overlapped echoes caused by different subpulses corresponding to multi-direction swathes and remove the range ambiguity and azimuth ambiguity deeply. At first, we build the signal model of HPMSAR system. Furthermore, the pre-filter design is presented by using matrix inversion method. Then, we address different methods applied to 2-D DBF and propose the advanced linearly constrained minimum variance (LCMV) method. Image results on simulated distributed targets validate the proposed hybrid multichannel processing method.

This paper presents a new implementation technique of transmission zeros in an in-line coupled filter. Neither cross couplings between non-adjacent resonators nor separate side-line resonators have been used. Instead a mixture of single-mode hairpin resonators and dual-mode patch resonators have been adopted in a bandpass filter with one asymmetric transmission zero. The introduction of the patch led to an improved frequency selectivity through an independently controllable transmission zero. This approach has been verified by a three-pole filter at 2.6 GHz with 8% bandwidth and a transmission zero at 2.4 GHz. Good agreement has been shown between the measurements and the simulation.

In this article, a novel printed quasi-self-complementary antenna with tri-band characteristic is presented for WLAN and WiMAX applications. A triangular quasi-self-complementary structure, which consists of a radiating patch and its counterpart slot on the ground, is employed to produce two operating bands centered at about 2.5 and 5.2 GHz. Then, by introducing a rectangular slit cut from the patch and its complementary mirror image strip inserted into the slot, an additional resonance at 3.5 GHz is excited and tri-band operation can be realized. A prototype of the proposed antenna has been successfully fabricated and measured. Both the simulated and measured results are obtained to demonstrate the promising performance required for practical applications. Based on the results, it is shown that 10-dB impedance bandwidths of the proposed antenna are 510 MHz (2.25-2.76 GHz), 330 MHz (3.38-3.71 GHz), and 770 MHz (5.1-5.87 GHz), respectively. Also, nearly omnidirectional radiation patterns and acceptable antenna gains can be achieved over the three operating bands.

The success of a ground penetrating radar (GPR) signal modeling scheme largely depends on its accuracy and computational efficiency. Most of the modeling schemes suffer from inaccuracy because of unrealistic assumptions of complex GPR environment. In this respect full wave model (FWM) of GPR signal is a promising approach for accurate characterization of multi-layered media. However, large computation time of FWM compared to other simplified models makes the approach inefficient for real time application. In this work an FWM scheme is developed based on electric field equivalent magnetic current density at antenna phase center. The compact analytical expression of Green's function representing response due to layered media is derived. Then a plane wave model (PWM) is proposed by introducing a spreading factor based on simplified expression of the FWM. The model inversion is successfuly carried out by a gradient based algorithm. A stepped frequency continuous wave GPR in off-ground monostatic configuration is implemented in laboratory environment to verify performances of the models. Experimental analysis proves that the proposed PWM is as accurate as FWM, and its computation efficiency is enormous to detect layered media parameters.