\n This study presents a novel configuration of a cuboidal quad-port ultra-wideband multiple-input and multiple-output antenna with WLAN rejection characteristics. The designed antenna consists of four F-shaped elements backed by a partial ground plane. A 50 Ω microstrip line is used to feed the proposed structure. The geometry of the suggested antenna exhibits an overall size of 23 × 23 × 19 mm3, and the antenna produces an operational bandwidth of 7.6 GHz (3.1–10.7 GHz). The notched band characteristic at 5.4 GHz is accomplished by loading a pair of spiral electromagnetic bandgap structures over the ground plane. Besides this, other diversity features such as envelope correlation coefficient, and diversity gain are also evaluated. Furthermore, the proposed antenna system provides an isolation of −15 dB without using any decoupling structure. Therefore, to validate the reported design, a prototype is fabricated and characterized. The overall simulated performance is observed in very close agreement with it's measured counterpart.

Cuboidal quad-port UWB-MIMO antenna with WLAN rejection using spiral EBG structures

Transformation optics is a powerful tool allowing remapping a generic domain into another yet maintaining a correspondence of the solution of Maxwell's equations within the two domains. Transformation optics has been used in the past to conveniently solve for modes in a generic waveguide by transforming its cross‐section into a circular one. Such a transformation needs particular care in enforcing boundary conditions in the transformed, circular, domain. In this paper, a theoretical treatment of boundary conditions is presented, allowing for an accurate computation of all field components in a generic waveguide.

Considerations on boundary conditions in transformation optics for complete field computation in generic waveguides

Mode matching method is here applied to waveguide fields calculated in a transformation optics framework. The proposed approach allows to obtain modes in terms of an expansion onto analytical basis functions for a waveguide of general cross-section provided that the contour can be expressed as a single-valued function in polar coordinates. Mode matching surface integrals are then easily reconducted to line-integrals on the contour thanks to the analytic expansion. The effectiveness of the proposed technique is validated against full-wave results from a commercial simulator and measurements available in literature. The proposed method shows a substantial speed-up, especially if the contour contains arcs of circumference, with a comparable accuracy. An in-depth study on the numerical convergence of mode matching and on the accuracy of the line integral formulation is also provided.

https://ieeexplore.ieee.org/ielx7/9171629/9206027/10138314.pdf

Transformation Optics Combined With Line-Integrals for Fast and Efficient Mode Matching Analysis of Waveguide Devices

Mode matching method is here applied to waveguide fields calculated in a transformation optics framework. The proposed approach allows to obtain modes in terms of an expansion onto analytical basis functions for a waveguide of general cross-section provided that the contour can be expressed as a single-valued function in polar coordinates. Mode matching surface integrals are then easily reconducted to line-integrals on the contour thanks to the analytic expansion. The effectiveness of the proposed technique is validated against full-wave results from a commercial simulator and measurements available in literature. The proposed method shows a substantial speed-up, especially if the contour contains arcs of circumference, with a comparable accuracy. An in-depth study on the numerical convergence of mode matching and on the accuracy of the line integral formulation is also provided. 

/pdf/transformation-optics-combined-with-line-integrals-for-fast-29oounfd.pdf

Giacomo Giannetti

Papers

Modes computation in arbitrarily shaped waveguides by a transformation optics approach

Considerations on boundary conditions in transformation optics for complete field computation in generic waveguides

Transformation Optics Combined With Line-Integrals for Fast and Efficient Mode Matching Analysis of Waveguide Devices