Frequency Selective Surface

There is a growing demand for new materials to enhance device performances at low cost. For several years, many periodicals there have been published (built from large number of uniform cells) which show that such engineering issues can be resolved.

Numerous cases demonstrate how some typical problems can be solved by using WIPL-D software.

They include: dipole radiation modified by very close FSS at 13 GHz, coupling between dipoles over FSS (WIPL-D is inherently able to calculate very low values of antenna coupling, well below -100 dB), RCS from FSS on dielectric slab (7×7 cells), energy transfer through FSS (additional 30 dB isolation), rectangular horn covered with FSS metallic radome. All models are run on standard desktop PC equipped with inexpensive GPU card. Simulation time is under 1h even for the most complicated cases.

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Wire Equivalents of Antenna Standoffs

The paper presents an efficient technique to determine equivalents of antenna dielectric standoffs in the form of wires with distributed loadings. The capacitive coupling of the antenna tube with the ground is characterized by capacitance per unit length (e.g. in pF/foot) of the transmission line made by the tube and the ground. Influence of each dielectric standoff can be emulated by wire of properly determined radius and distributed loading. The equivalent radius and the distributed loading are determined by cross-section dimensions of the standoff and its electrical properties (relative dielectric constant). The relative dielectric constant can be determined the tube radius and capacitance per unit length in the presence of dielectric stand. Using reverse engineering, dielectric constant can be emulated if the capacity per unit length is known. If simple and fast model are required for fast simulation and optimization, replacement of the dielectric standoff with wires with distributed loadings is the right approach. It is shown that the results obtained using WIPL-D are very close to the theoretical result, which proves the concept.

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Log-Periodic Dipole Antenna in AW Modeler

Log-Periodic Dipole Antenna with the 52 printed dipoles is created in WIPL-D AW Modeler and then simulated in WIPL-D Pro. The symmetry has been applied, as well as edge manipulation (other simulation parameters are left at the default). Entire antenna is around 261 mm long and it is placed 4.25 mm away from the metallic circle with diameter 248 mm. The longest arm of the antenna is around 76.2 mm long and length of the shortest one is around 1.53 mm.

Simulation times and number of unknowns needed for simulating LPDA antenna at different operating frequencies in the frequency range from 1 GHz to 18 GHz, are presented in the application note. The simulation hardware is standard desktop PC, empowered by low-end Nvidia GPU card (GPU solves has been used to speed up matrix inversion).

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WIPL-D 2-D Solver

WIPL-D 2-D Electromagnetic Solver is indented for numerical electromagnetic analysis of cylindrical structures, theoretically infinitely long. The program works with 2-D cross-sections (cuts) of the analyzed structure.

Numerical engine is based on the surface integral equation formulation: electric field integral equations (EFIE) for metallic structures and PMCHWT formulation for dielectric and magnetic materials. It can handle arbitrary combinations of piecewise linear materials along with any combination of infinitely or finitely thin layers with distributed loadings.

The examples in the application note include near field in the vicinity of PEC elliptical scatterer, demo of complex 3-D structure with incorporated tool for extraction of cuts, and 12-decade frequency sweep of backscattered RCS from a perfectly conducting cylinder with circular cross section of 1 m radius.

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WIPL-D Optimizer

WIPL-D Optimizer is a powerful multi-algorithm optimization tool that is being used by many successful professionals around the world. The tool calculates single solution as well as multiple solutions for complex/multi-criteria optimizations. Thanks to its simple and intuitive graphical interface, you can quickly solve the problem at hand.

Built in optimization algorithms are: Particle Swarm, Genetic, Simulated Annealing, Random, Gradient, Systematic and Simplex. Unique feature is that two optimization procedures with different algorithms can be performed in succession. The first one is used for coarse optimization and the second one is used for fine tuning. The examples include optimized horn antenna and automated design of a waveguide filter.

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Microwave Tomography in Biomedicine using (A)Symmetry

This application note provides detailed theoretical explanation on how the asymmetry feature is implemented in the WIPL-D suite. The user effectively models half, quarter or one eight part of the structure and sets asymmetry planes. The last step is to adjust the required voltages of generators (equal amplitudes are the default value). The code afterwards determines minimum number of simulations required (by combining simulations with PEC and PMC planes).

The usage of the feature reduces number of unknowns 2/4/8 times and simulation time up to 4/16/64 times. The simulation time reduction depends on the electrical size of the problem and is more pronounced for the electrically larger problems. The usage of the feature allows using tremendously less powerful WIPL-D license and extends the range of structures that can be simulated.

The simulations have been carried out on inexpensive hardware platforms owing to GPU technology and the GPU solver. The examples include a simple circularly placed array of dipoles (to verify accuracy), canonical PEC cuboid (to verify reduction of number of unknowns and simulation time) and realistic 3D microwave tomography system. Last example shows how asymmetry allows solving demanding example in engineering acceptable time in UWB application

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