Massimiliano Casaletti

Efficient Analysis of Metallic and Dielectric Posts in Parallel-Plate Waveguide Structures

A mode-matching method is proposed for the accurate and fast analysis of structures composed by metallic and dielectric posts in a parallel-plate waveguide environment. The incident and scattered fields on each post are expressed with a cylindrical mode expansion. After enforcing the appropriate boundary conditions, a set of matrix equations is derived. The corresponding solution are the coefficients of the field vector expansion. The method is validated with several examples found in the literature and compared with the results obtained with the commercial software Ansys HFSS. The proposed method can be used for a very fast electromagnetic analysis of substrate integrated waveguides and substrate integrated slab waveguides.

Compact multibeam rotman lens antenna in SIW technology

We introduce here a novel dual-layer multibeam antenna with a folded Rotman lens as a compact beam forming network. The antenna is based on substrate integrated (SIW) technology. The objective is to reduce the overall size of the antenna system by folding the Rotman lens on two layers along the array port contour. The Rotman lens is folded by resorting to a novel transition based on an exotic reflector and several coupling vias holes. To validate the proposed concepts, an antenna system has been designed at 24.15 GHz. The radiating structure consists of a SIW slotted waveguide array made of fifteen resonant waveguides. The simulated results show very good scanning performances over an angular range of ±47°. It is also demonstrated that the proposed transition can lead to a size reduction of about 50% for the lens, and more than 33% for the overall size of the antenna.

A new synthesis technique for near-field focusing systems

Summary form only given. Pattern synthesis techniques have been widely used during the years to define and sculpt the radiation patterns of an antenna system in its far-field region. However, in several applications such as near-field probing and radiometry, medical imaging, etc. it is important to focus the energy in the Fresnel zone or even in the extreme near-field (reactive zone) of an electromagnetic device. In (J. W. Sherman, III, IRE Trans. Antennas Propagat., vol. AP-10, no. 4, pp. 399-408, July 1962), the properties of the electromagnetic fields in the far-field and Fresnel zone of a focusing radiating aperture are examined. The latter are the fields near the axis of a defined focal plane parallel to the aperture. It is shown that the fields in these two zones present the same properties as long as a quadratic phase taper of the tangential field distribution is adjusted on the focusing aperture. Therefore, the optimization/shaping of fields in the Fresnel zone can be achieved by using classical far-field techniques. However, this is not possible within the near-field or reactive zone of a radiating system. In contrast to previous works derived from Shermans conclusions, here we propose a new technique for shaping the near field of a focusing aperture based on an alternate projection method (O. M. Bucci, et al. Proc. IEEE, vol. 82, no. 3, pp. 358-371, Mar. 1994). The required near field is defined along a focusing plane in front of the aperture in terms of the desired axial pattern around the focal point and/or transverse plane patterns. The required field is described in terms of the focus depth, relative amplitude of forelobes and aftlobes. side lobe level, half power beamwidth, etc. Circular and linear polarized fields are considered. The possibility to control specific components of the field is also envisaged. Once the required near field pattern is defined, the aperture field distribution is found thanks to a combination of the alternate project method and a Fast Fourier Transform (FFT) algorithm. The FFT algorithm is used to evaluate the field at the focusing and aperture plane avoiding unnecessary approximations of previous works. Finally, a radial line slot array (RLSA) is used to synthetize the derived aperture field distribution in phase and amplitude. An in-house fast Method of Moments is employed during this step to control the aperture efficiency and distribution error. Several examples will be proposed during the conference. In particular, the possibility to generate with an RLSA arbitrary propagating Bessel beams will be presented. The proposed technique paves the way to the synthesis of any desired field shape in the near-field zone of a radiating structure.

Optimized analysis of slotted substrate integrated waveguides by a method-of-moments mode-matching hybrid approach

A full-wave hybrid formulation is proposed for the efficient and accurate modeling of substrate integrated waveguides by rigorously accounting for all possible interactions among elements such as vertical metallic or dielectric posts and coupling or radiating slots. The method is specifically accelerated in order to maximize the efficiency of the analysis of common structures. Its flexibility allows for the study of a large class of devices, possibly in stacked-waveguide configurations, and for the characterization of radiated fields and input port parameters.

Generalized Shannon Basis for Flat Faces of Scatterers and Planar Apertures

This paper introduces a new type of entire-domain basis functions for the analysis of the scattering from 3D polyhedral bodies. A non-redundant set of basis functions is determined a priori by explicit approximate formulas either for currents or radiated field representation. Numerical results are presented to shown the accuracy of the method.