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The combined source (CS) condition isemployedtoaugment the electric field integral equation (EFIE), whereby the CS condition is implemented as a modification of the weak form Leontovich impedance boundary condition. By doing so, both electric and magnetic surface current densities can be modeled with Rao-Wilton-Glisson (RWG) basis functions. Strict point-wise orthogonality of electric and magnetic...
A time gating approach for antenna measurements is presented which is based on a ℓ1-norm regularized convex optimization. Exploiting the sparsity of the time domain signal consisting of direct and echo signal contributions helps to increase the time domain resolution and to decrease the necessary measurement bandwidth. The method is applied to echoic measurement data to show its effectiveness in echo...
Due to the linear formulation of their algorithms, many inverse synthetic aperture radar imaging systems are known to produce artifacts in case of monostatic setups with multiple interactions at the scatterer. Bistatic systems, where transmitting and receiving antennas are separated, may avoid this problem and are therefore of high interest. Considering relatively small bistatic angles, it is shown...
We present an analysis of the application of (general) hierarchical basis preconditioners developed for preconditioning the electric field integral equation (EFIE) to the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) integral equation on simply and multiply-connected geometries. First, we discuss the correct choice of the rescaling factors for the solenoidal and non-solenoidal hierarchical bases...
A powerful Shooting and Bouncing Rays (SBR) solver for scattering computations, utilizing NVIDIA CUDA, is presented. The asymptotic simulation tool can treat arbitrary metallic and dielectric objects and is thus well suited to quickly predict electromagnetic scattering caused by large realistic objects.
The consistent analysis of complex antenna setups with statistically varying media attributes is performed in this paper through a 3-D curvilinear stochastic finite-difference time-domain technique. The new method generalizes the concept of covariant/contravariant metrics for curved structures and derives the mean value and standard deviation of field components in a single run. Also, for the acceleration...
A new stirring mode for reverberation chambers is proposed and analyzed using a cavity Green's function boundary element method algorithm. In contrast to the standard mode, parts of the stirrer are rotated clockwise while the other parts are moved counterclockwise. The performance of synchronized and interleaved modes is investigated by determining the number of independent stirrer positions and testing...
A finite element boundary integral approach with the Green's function of the rectangular cavity is introduced and applied to the simulation of reverberation chambers. In contrast to all other approaches that use the cavity Green's function, the computationally expensive part of the system matrix is factorized in the spectral domain yielding a significant acceleration of the algorithm. Numerical results...
When the Electric Field Integral Equation (EFIE) is discretized with a stable basis, such as the RWG basis functions, the resulting system matrix is, in general, ill-conditioned. Hierarchical bases can be used as preconditioner to overcome this issue. For a complete regularization of the EFIE, they require, however, a structured mesh (i.e., a mesh resulting from a dyadic refinement), which limits...
A novel Method of Moments approach with the Green's function of the rectangular cavity is introduced, compared, and validated against the Method of Moments with the free-space Green's function. The Ewald method is employed to accelerate the computation of the cavity Green's function. The spectral part of the system matrix is factorized in the spectral domain resulting in a significant reduction in...
The widely used high-frequency approximation methods GO/UTD (Geometrical Optics with Uniform Theory of Diffraction) and PO/MEC (Physical Optics with Method of Equivalent Currents) for wave propagation problems are compared with respect to their scattering behavior, where the focus is on the near-field accuracy of the scattered fields. This topic is of great importance for vehicular wireless system...
Eigenvalues of periodically constituted waveguides with complicated material distribution are efficiently determined, where eigensolvers in software packages show difficulties in finding the eigensolutions. Moreover, the treated waveguide structures are open, causing even more trouble with available numerical solvers or rather demanding procedures within analytical approaches. Since open configurations...
A new magic-T using HMSIW and slotline coupling is presented. Due to the metal ground inserted into the middle of the substrate, the power divider has a 180° reverse phase. A slotline in the middle ground can couple the energy and functions as the H-arm of magic-T. A Ku-band magic-T is fabricated, good agreement between the measured and simulated results is observed, indicating that the planar magic-T...
This paper presents different enhanced electromagnetic models of mirror-type BAW resonators that are simulated with a 3D electromagnetic solver, whereas the acoustic effects are computed with a 1D solver. Further, the effects of the electromagnetic mesh-cell-density in simulations for the different resonator models are analyzed. The simulations of BAW resonators and duplexers can be improved by appropriate...
This paper presents the results of frequency domain channel sounding of wireless in-car channels. Based on an extended measurement campaign different application-specific channels are characterized by channel gain, cumulative density functions and time dispersion parameters. The measurement sets are chosen for the freely disposable industrial, scientific and medical (ISM) frequency bands. Characteristic...
A new accelerated method for generating a fully polarimetric 3-D image of an arbitrary current distribution is proposed. The sampled farfield radiation pattern is sufficient for the reconstruction of the image. The algorithm is based on a coherent summation of the fully polarimetric plane wave spectrum. The processing of the spectrum is accelerated by a Multi-Level Fast Multipole Method-inspired hierarchical...
The leakage attenuation makes the modelling of substrate integrated waveguides (SIWs) a complicated complex eigenproblem. The analogy to resonators opens up a new way to solve the eigenproblem from a physical point of view. A novel driven eigenproblem computation is presented in this paper to solve the eigenproblem in periodic structure like SIW by treating the structure in a unit cell with periodic...
Estimation of the transmitter position based on the received signal strength (RSS) appears to be an attractive approach for indoor applications. However, strong power level fluctuations within buildings decrease the accuracy and reliability considerably. In this paper we present an extensive study based on simulations by applying a distributed antenna system for localization purposes in indoor scenarios...
Measurements in the antenna near field allow to compute the far-field radiation pattern by a postprocessing near-field far-field transformation. These algorithms use equivalent sources to model the radiation behavior of the antenna and have to consider the field probe influence present in near-field antenna measurements when relating the measured probe signals to the equivalent sources. In order to...
For the solution of electromagnetic surface integral equation problems, a fast solver based on multilevel interpolation of the respective Green's functions is presented. Besides the commonly used electric current mixed-potential integral equation formulation (MPIE) of the electric field integral equation (EFIE), the effectiveness of a direct field formulation for very ill-conditioned low-frequency...
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