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This paper presents some of the results of the measurement campaign that was undertaken in order to validate some of the properties that had been previously anticipated for the enhanced leaky lens antenna. To our knowledge the link between two leaky lenses is demonstrated to be less dispersive than any other radiation link previously reported .

This paper provides a comparison between two different techniques for the array pattern side-lobe reduction in a passive radar system based on a circular array. The first method retrieves the phase modes pattern for the reference array and then applies a conventional tapering for the side lobe suppression of the obtained virtual uniform linear array. The second approach foresees instead an optimization algorithm in order to obtain the desired level of the side lobes. Both techniques have been adapted for being used with an 8 elements FM-based circular array for passive radar applications developed at TNO - Defence, Security and Safety in The Hague. The effect of the directional elements has been also considered for the array pattern synthesis. The different advantages of the algorithms are described and a distinction about the possible fields of application is retrieved. © 2010 EuMA.

In this paper the concept of limiting frequency selective surface (FSS) is presented. The design of a reconfigurable FSS equipped with PIN diodes, aimed at the protection of a radar receiver from high power impinging electromagnetic waves is outlined and verified against the measurement results of a hardware demonstrator.

This paper describes an efficient methodology for the design of steep roll-off Frequency Selective Surfaces (FSS’s). The proposed technique is based on the Multimode Equivalent Network (MEN) approach, which was originally developed for the analysis of waveguide junctions. The MEN has been extended to the study of multi-layer patch based and aperture based FSS’s. The result is a general formulation that allows characterizing complex structures, consisting of radiating apertures and FSS’s, in the same framework used to account for feeding and filtering elements inside the waveguides. Moreover, thanks to the modularity of this approach, it will be shown in the paper that it can be used as agile design tool. In particular, this paper describes the design procedure for a multi-layer FSS to be integrated with the X-band phased array of a Multi Functional Radar (MFR) in order to prevent interference from an antenna located in its proximity and operating in a partially overlapping frequency range. The analysis results of this integrated structure, obtained with our tools, were compared with those produced by a commercial code, showing very good agreements. The designed FSS has been manufactured and measured for different incidence angles.

The use of Frequency Selective Surfaces (FSS) is becoming more and more frequent in the design of antennas for complex warship platforms. From the antenna point of view, the main challenge is the capability of designing antennas with high performances, integrated in complex platforms with low Radar Cross Section (RCS) and a high number of different antenna systems mounted on the same support. This clearly requires the capability of improving the frequency and angular selectivity of the antenna, keeping at the same time under control the dimensions and shapes of the antenna itself. The solution to these requirements is the design of array antennas integrated with FSS panels with different frequency/angular filtering behavior. In previous works, we have already presented an efficient and flexible approach to this kind of problem based on a Multi-mode Equivalent Network (MEN) method (G. Gerini, L. Zappelli, Conference Proceedings 31st European Microwave Conference, 2001, pp. 321-324), (S. Monni, G. Gerini, A. Neto, XXVII URSI General Assembly, 2002). This technique allows the derivation of an accurate multi-mode impedance matrix representation of the overall structure including array, arbitrary shaped FSS’s and radomes placed on the top of the array itself. A crucial aspect in terms of accuracy and efficiency is the choice of the expanding functions for the unknown electromagnetic quantities. Hence, in order to investigate this aspect, in this contribution we analyze the effects of expanding the unknown electromagnetic quantities in terms of different basis. We have considered both piecewise sinusoidal expanding functions and full-domain modal representations obtained by the BCMM (boundary contour mode matching) method (F. Giese, J. M. Reiter, F. Arndt, IEEE MTT'S Digest, 1995, pp. 1359-1362). These different expansions have been applied to dual problems like metallic patches and screens of infinitesimal thickness and arbitrary cross-section. In general, piece-wise sinusoidal functions have a very simple analytical form and offer a great flexibility in terms of shapes that can be analyzed. On the other end, their large spectral content is such that a very large number of terms (proportional to the scalar product of the expanding functions with the Floquet’s modes) have to be summed up in the kernel of the integral equation. This would lead to a relatively large CPU time, unless efficient acceleration techniques are applied in the summation of the series. On the contrary, full domain basis functions are less flexible for the analysis of complex shapes and often require the solution of an eigenvalue problem for the eigenmodes determination. Nevertheless, a relatively smaller number of functions are necessary to describe the unknown fields in complex geometries and furthermore their spectral content is such that the kernel of the IE is more rapidly converging. A comparison between results for the same problem obtained with the two expansion sets will be presented at the conference, together with a detailed trade-off study in terms of accuracy and computing time.