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A probe-fed dielectric resonator antenna (DRA) element is investigated for operation in a waveguide environment with application to spatial power combining amplifier arrays. The method of analysis is based on the finite-difference time-domain (FDTD) approach, wherein a rectangular waveguide and DRA are discretized by using a traditional Yee cell griding and a coaxial line is modeled by a thin wire approximation. The input impedance and scattering parameters are studied by varying geometrical and material parameters of the DRA and the coaxial probe feed. The numerical results obtained by the proposed FDTD method are compared with those generated by using a commercial software and exhibit very good agreement.

Artificial Magnetic Conductors (AMCs) are a relatively recent invention [1,2,3], and hold significant promise in reducing antenna size, particularly thickness [4]. It is important to be able to simulate these complex structures accurately in order to better understand their behavior and improve their design. A Sievenpiper AMC [3] with a UHF dipole was designed, and WIPL-D [5] was used to model this structure. The simulated results were compared with S11 measurements on a prototype structure. WIPL-D returned results that predicted the resonance frequency and in-band behavior of the structure with high accuracy, and also showed some of the observed behavior at frequencies other than the main resonance.

The return loss of rectangular, single- layer, coax- fed patch antennas designed to resonate at 1904 MHz was computed using WIPL-D and HFSS and the results compared with experiment. It was found that neither WIPL-D nor HFSS estimates the bandwidth and the resonant frequency with sufficient accuracy. However, the resonant frequency predicted by WIPL-D was found to be closer to the experimental value than predicted by HFSS.

The most difficult cases for EM analysis are large and realistically complex scatterers. Method of moments (MoM) allows efficient and accurate simulation of structures of small to moderately large electrical size. Traditional MoM scales poorly to higher frequencies on a given object, but this problem has been significantly mitigated through such innovations as higher-order basis functions (HOBFs) and the multi-level fast multipole (MLFMM) algorithm. Asymptotic methods, also known as high-frequency (HF) methods, are widely used to efficiently compute the scattering by objects whose overall size and features are electrically large. In this paper, an asymptotic ray-tracing code (Savant) and an MLFMM MoM code (WIPL-D Pro) are used to predict bistatic RCS of an electrically large, realistic vehicle. The accuracy of each method is carefully controlled to effect meaningful comparisons. The results demonstrate the efficacy of MLFMM in significantly extending the frequency reach of traditional MoM and that, at high-enough frequencies, complex objects can be simulated by asymptotic ray-tracing methods with comparable accuracy to direct methods.

A wideband UHF antenna was designed for use in a linear array. The array was to be scanned in the H-Plane. The principal design constraints were wide bandwidth, broad array plane pattern (for scanning), light weight, and small overall size. The Balanced Antipodal Vivaldi antenna [1] was employed as a starting design because it met several of these criteria, because its unbalanced construction facilitated feeding via a coaxial line, and because of its low cross polarization. The resulting antenna was shortened considerably and the high dielectric substrate replaced with foam. The resulting antenna was further reshaped to meet impedance and pattern constraints, and suppress mutual coupling effects. WIPL-D [2] was used extensively in the design process. Three prototypes were built. Measurements agreed well with analysis, but small shape adjustments were required to optimize performance.

The diakoptic surface integral-equation formulation (DSIE) is used for simulations of complex 3-D scatterers. Comparisons to solutions found using the classical method of moments are presented, illustrating accuracy, acceleration, and storage reduction achieved using the diakoptic approach. The implemented DSIE uses the WIPL-D engine for calculation of MoM-SIE coefficients and for the post-processing of results.

Simulations were run in WIPL-D [1] using homogeneous metallic or dielectric material separately with the same scattering structure at grazing angle. The frequency domain (FD) data was processed with Gaussian windowing and the inverse discrete Fourier transform. The resulting time domain (TD) plots are compared. The conclusion is that a metallic structure simulation can provide information relevant to the dielectric structure in much less time using fewer unknowns. An approximation for the structure\'s observed resonance is discussed.