Simple Bandstop Filter Research Articles

Integral Equation Formulation for Planar Plasmonic Structures With Finite Thickness in Layered Media

A detailed Volume Integral Equation (VIE) formulation for planar plasmonic nano structures with finite thickness in flat multi-layers medium is presented. The boundary condition along the localized metallic objects is expressed in terms of the unknown polarization current flowing through these objects in the form of an integral equation, which is solved using the Method of Moments (MoM). The Green's functions associated with a layered medium of practical importance are expressed in the spectral domain. The corresponding spatial domain Green's functions are obtained using the Discrete Complex Images Method (DCIM). Special treatment for the spectral function's asymptote at high spectral values is performed. The presented formulation is applied on different plasmonic structures immersed inside layered media. The structures include nano-rod and nano-patch excited by an incident plane wave. In addition, a simple band-stop filter based on quarter-wavelength stubs is considered. This filter is fed with a couple of plasmonic transmission lines. The obtained current distributions and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters are compared with those obtained using a commercial full-wave electromagnetic simulator, namely CST Microwave Studio. A very good agreement is observed. The proposed integral equation formulation enjoys high degree of stability, numerical efficiency, and accuracy.

Tuning space mapping: The state of the art

The electromagnetic (EM)-simulator-based tuning process for rapid microwave design can combine EM accuracy with circuit-design speed. Our own approach is based on the intuitive engineering idea of “space mapping.” In this article, we explain the art of microwave design optimization through “tuning space mapping” procedures. We list various appropriate types of models (called “surrogates”). We demonstrate the implementation of these surrogates through a simple bandstop filter. We provide application examples using commercial simulation software. Our purpose is to help microwave engineers understand the tuning space mapping methodology and to inspire new implementations and applications. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22: 639–651, 2012.

Progress in Simulator-Based Tuning—The Art of Tuning Space Mapping [Application Notes

We discuss tuning space mapping (port-tuning) techniques that can significantly reduce time and effort for design closure. We elaborate on various possible approaches. We distinguish between Type 1 and Type 0 embedding to indicate how tuning elements may be introduced into EM simulations to form suitable tuning models or surrogates. We optimize and update such surrogates iteratively to predict good EM designs. We illustrate the techniques using a simple bandstop filter and demonstrate their power using more complex filter design examples. Finally, we discuss from a physics point of view the possible locations of cuts, the effects of the cutting and reconnection, and we compare models that employ internal cuts with models that consider combinations of submodels.

Demonstration of the Stierwalt effect caused by scatter from induced coating defects in multilayer dielectric filters

Many applications of optical technology require the use of narrow bandpass filters with superior levels of out-of-band rejection. Frequently, system designs require that the filter be placed in close proximity to a detector or focal plane array. Many years ago Stierwalt (Opt. Eng. 13 (1974) G115; Proc. SPIE 132 (1978) 134) discovered that some filters that met out-of-band rejection specifications in a spectrophotometer did not meet specification when integrated into a focal plane assembly. In fact, he reported that proximal to the detector, one filter passed three orders of magnitude more out-of-band light. Since then, the Stierwalt effect has become widely discussed, but few papers have been published regarding this effect. Many investigators assume that the effect originates with scatter in the films, but very little data have been reported. In this paper, we demonstrate that optical coatings with high levels of scatter resulting from introduction of model coating defects exhibit an enhanced Stierwalt effect as compared to otherwise identical coatings that do not contain these defects. The seeding was done by depositing sparse 1 μm polystyrene spheres upon a clean substrate before sputter depositing a simple band-stop filter. Light rejection from filters prepared in this way showed a strong dependence upon the distance between the film and the detector. Filters deposited without the spheres showed a much smaller effect.