Lorenzo Cifola

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).

Compact design of a planar filtering antenna array including a frequency selective common-mode rejection module

A new compact design of a planar phased-array antenna with inherent frequency selectivity properties is presented. In previous works, starting from an array of connected dipoles, the design of a filtenna structure and a strategy for the suppression of common-mode resonances have been addressed. In the present approach, a compact design solution has been obtained by the integration of part of the filtering function in the common-mode rejection module, consisting in a planar hybridring. As proved by simulation results, scanning up to 45° for the H-plane and up to 30° for the E-plane is achieved with a relative bandwidth of 21%.

Diamagneto-Dielectric Anisotropic Wide Angle Impedance Matching Layers for Active Phased Arrays

In this paper, we present the full process of designing anisotropic metamaterial (MM) wide angle impedance matching (WAIM) layers. These layers are used to reduce the scan losses that occur in active phased arrays for large scanning angles. Numerical results are provided to show the improvement in performances that such layers can ensure. The proposed anisotropic MM-WAIM layers achieve an improvement of about 1dB of more radiated power at θ = 70 ◦ from broadside, in a 13% of fractional bandwidth on the azimuthal plane φ = 90 ◦. Weaker improvements are obtained in the other azimuthal planes, however keeping the active reflection coefficient below −9dB for all azimuthal planes up to θ = 60 ◦ and up to θ = 70 ◦ off-axis for planes φ = 45 ◦,90◦ in the whole operational band.

Design of an active array filtenna for radar applications

A novel design of an S-band active array antenna with enhanced frequency selectivity properties, for radar applications, is presented. The array unit cell consists of a stacked-patch radiator, characterized by an operational bandwidth of [2.8 - 3.4] GHz. A microstrip two-pole band pass filter is connected to the antenna feeding line, improving in-band frequency selectivity. Furthermore, a stop-band region is created in correspondence of the third harmonic (X-band [8.5-10.5] GHz). This is achieved through the insertion of slots on the patch surfaces, lowering the respective resonant frequencies associated to the third harmonic. Furthermore, filter stub resonators have been properly designed in order to create stop-band region within the X-band. Good in-band matching and out-of-band suppression performances are achieved when scanning up to 60° for all the main planes (E, D, H).

ON THE USE OF GEGENBAUER PROTOTYPES IN THE SYNTHESIS OF WAVEGUIDE FILTERS

Filter prototypes derived from Gegenbauer polynomials can represent a useful trade-ofi between amplitude and phase behavior. This paper discusses the main features of this prototype through a comparison with the more classical Chebyshev and Butterworth solutions; it shows, in the case of an X-band waveguide realization, how its intermediate characteristics, with respect to both amplitude and phase responses, can be very useful in satisfying particular fllter performance requirements without increasing fllter order.