Stefania Monni

UWB, Non Dispersive Radiation From the Planarly Fed Leaky Lens Antenna—Part II: Demonstrators and Measurements

We provide for the first time the experimental characterization of a planarly fed ultrawideband leaky lens antenna. The paper includes the description and the experimental characterization of two antenna prototypes with radiating element realized in printed circuit board technology. The impedance parameters and the radiation patterns of the antennas have been measured showing excellent pattern quality and efficiency. The link between two antennas has also been characterized in the frequency and time domains in terms of mutual coupling impulse response respectively. Unprecedented performance in terms of pulse fidelity are demonstrated suggesting very high potentials of these antennas for all applications that require preservation of narrow pulses.

Multimode Equivalent Networks for the Design and Analysis of Frequency Selective Surfaces

A modular technique originally proposed for waveguide junctions, the multimode equivalent network approach based on the integral equation formulation (IEMEN), is extended to the analysis of multilayer frequency selective surfaces integrated with waveguide array antennas. This technique represents each layer and transition between layers in terms of a generalized impedance or admittance matrix, obtained directly from the solution of an integral equation with reduced kernel. Thanks to the adopted formulation, the integral equation needs to be solved only in a limited set of frequency points. The IEMEN method is validated by comparison with results available in literature.

Frequency-Selective Surface to Prevent Interference Between Radar and SATCOM Antennas

Interference between neighboring antennas operating in nearby frequency ranges can lead to damage of the front-end electronics. This letter presents the design of a frequency-selective surface (FSS) aimed at preventing the saturation of the low noise amplifiers of a phased-array radar antenna due to the carrier of a satellite communication antenna located in its proximity. A fast design was possible thanks to the integral equation method for the derivation of multimode equivalent networks (IEMEN) and was then validated by reflection and transmission measurements of a hardware demonstrator.

Frequency Selective Surfaces for Extended Bandwidth Backing Reflector Functions

This paper deals with the use of frequency selective surfaces (FSS) to increase the efficiency X bandwidth product in wideband antenna arrays, whose efficiency is limited by the front-to-back ratio. If the backing reflector for the antenna is realized through a single metal plane solution, its location will be suitable only on a relatively limited frequency range especially if wide angle scanning is required. In order to extend the frequency range of usability, an FSS can be sandwiched between the antenna and the ground plane, providing an additional reflecting plane for an higher frequency band. The possibility to integrate in the antenna different functionalities, otherwise performed by several antennas, is also discussed in the paper. The proposed backing structure composed by the FSS and the ground plane has been designed to be used in conjunction with a wideband antenna consisting of an array of connected dipoles. A hardware demonstrator of the backing structure has also been manufactured and tested.

Frequency Selective Surfaces for the RCS reduction of low frequency antennas

This paper describes the design and measurement of a two-layers gangbuster Frequency Selective Surface (FSS). The FSS is aimed to limit the RCS of the compartment of a ship¿s mast housing telecommunication antennas and should guarantee a pass-band at low frequencies, in the operating band of the antennas, while reflecting the incoming signal at higher frequencies, up to 20 GHz. Based on the design, a panel has been manufactured and measured in three frequency bands: S-band, X-band and quasi L-band. The measurement results obtained for the first two bands are in good agreement with the simulations. Measurements in the third band pose some challenges and required defining a new ad-hoc measurement setup.

Integrated filtering in reconfigurable planar phased-array antennas with spurious harmonic suppression

In the present work, the possibility to integrate filtering functionalities in a phased-array antenna at radiating element level is investigated. The filtenna concept has been applied to an X-band phased array of slot-fed patches. An effective strategy for the suppression of spurious harmonics, based on the perturbation of the patch currents of the patch associated to the higher order modes, is described. Furthermore, frequency reconfigurability has been introduced at the antenna level, making the radiating structure capable of covering the entire radar X-band ([8.5-10.5] GHz).

Phased array antenna integrated with a frequency selective surface - theory and experiments

A modeling tool is described to characterize the array antennas integrated with frequency selective surfaces by means of a multimode equivalent network approach applied to infinite periodic structures. The theoretical formulation of the problem is presented in this paper together with the numerical results for an array of dielectric loaded waveguides integrated with a patch based FSS. Waveguide simulator measurements are also reported for comparison.

Detection of IEDs with leaky wave antennas

A novel leaky wave antenna with ultrawide band radiation and high fidelity (low dispersivity) is presented. The suitability of this antenna for a hand-held GPR is evaluated through measurements in a quasi-monostatic setup of an antipersonnel mine and an anti-tank IED-like object buried in dry sand.

Analysis acceleration in the design of frequency selective surfaces using parametric techniques

The design of multi-layer frequency selective surfaces often requires characterising the behaviour of the structure in wide frequency and angle ranges. Moreover, a fine tuning of the design leads to a large parameter space and results in a long computational time. To address this problem, an efficient parameterisation and interpolation technique has been implemented within the multimode equivalent network approach based on the integral equation formulation, a technique developed for the analysis of multi-layer periodic structures. The paper describes this technique and shows for a test case consisting of an array integrated with an FSS how the calculation time can be drastically reduced.

Near field resolution measurements with the leaky wave antennas

Leaky wave antennas operate in a wide frequency band, have a relatively high gain and high pulse fidelity. These properties are valuable for a GPR system, where often a trade-off between antenna efficiency and operational bandwidth has to be made. This paper presents laboratory measurements of near field resolution with two leaky wave antennas in a quasi-monostatic setup.