In this letter, we present a design of a linear array of tilted dipoles to achieve radiation patterns with asymmetric angular filtering characteristics. To realize the asymmetric radiation, the dipole elements are spaced by a distance larger than half a wavelength, thus allowing for grating lobes to occur in the visible region. Moreover, the dipoles are loaded with artificial dielectrics to increase the front-to-back ratio and consequently to enable higher gain in certain desired angular regions. Based on the design, a linear array with ten elements is manufactured and tested. The measured results show the ability of such an array to achieve stable gain from broadside up to 90° scanning while implementing a stopband angular filter for negative scanning angles.@en

In this work, we present a study on the radiation and impedance properties of antenna arrays with tilted elements. We developed a spectral method of moments (MoM) for the analysis of doubly-periodic arrays with arbitrarily tilted dipole or stacked dipole elements, in free space or in the presence of a backing reflector. By using this analysis method, we study the radiation characteristics of arrays of stacked dipoles over a ground plane, highlighting the variation of the patterns as a function of the inter-element distance and the angle of inclination of the elements. The guidelines derived from the MoM analysis have been applied to the design of a linear array of tilted stacked dipoles.

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A five-layer frequency selective surface (FSS) composed of subwavelength elements with large harmonic rejection bandwidth is presented. The FSS design is based on an equivalent circuit model, where the interlayer interaction is only described with a single transmission line representing the fundamental Floquet wave. A prototype of the designed FSS is fabricated, and the measured response exhibits good stability over a wide conical incidence range up to 45°. The FSS is combined with a wide-scanning connected array of dipoles to implement a phased array with integrated filtering properties. A dispersion analysis is performed to define the distance between the array and the FSS that avoids the propagation of surface waves between the combined structures, allowing to maximize the radiation efficiency. The performance of the array combined with the FSS is experimentally characterized, showing high-order harmonic rejection better than 17 dB over a large bandwidth.@en

We present the design of a frequency selective surface (FSS) with large harmonic rejection bandwidth. The FSS comprises five metal layers, each consisting of a periodic array of subwavelength elements. The design is based on an equivalent transmission line model that includes only the fundamental Floquet mode. This model is valid under the condition that the unit cell size is smaller than the distance between layers. The multi-layer FSS has an overall height of one sixth of the free-space wavelength at the central frequency of operation. The simulated frequency response exhibits good stability over a wide conical incidence range, up to 45 degrees. A prototype of the designed FSS is fabricated and combined with a wide-scanning connected array of dipoles to implement an antenna element for phased array applications, with integrated filtering properties.

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In this work, the problem of enhancing the frequency selectivity property of an antenna array has been studied. A solution based on a multi-layer frequency selective surface (FSS), composed of sub wavelength elements is proposed. An equivalent circuit model is used for the design, under the assumption that the inter-layer interaction is dominated by a single Floquet mode. This approximation remains valid by keeping the unit-cell size comparable to the inter-layer distance. Results for generic oblique incidence are presented. Fast roll-off is achieved by using a 3 pole Chebyshev filter design. Moreover, the FSS is used in combination with a connected slot array antenna. The resulting structure allows to scan up to 45° in both principal planes with a relative bandwidth (S11<; -10 dB) of 15% around the central frequency f0 = 4.8 GHz. Higher order harmonics are rejected up to 18 GHz.@en

In this paper, two approaches for compensation of mutual coupling and phase shifts in a passive radar system based on a circular array are compared. The first method is based on the measurement of the antenna scattering parameters and of further relative phase and amplitude variations between the channels introduced by the receiver analog front-end and by the analog-to-digital converter. The second method derives a total coupling matrix, which contains both the antenna and the front-end contributions, by measuring the signals transmitted from known positions. The two procedures have been applied to an FM-based passive radar that uses an 8-element circular array. It appears that for the considered geometry the antenna mutual coupling does not significantly affect the radiation pattern, while the major contribution is due to phase shifts introduced by the receiver front-end.@en

To demonstrate the ultra-wide bandwidth performance while retaining manageable lens dimensions, 12 GHz has been chosen as lowest operating frequency. The planar feed has been realized in standard printed circuit board (PCB) technology. The matching layers reduce the reflection at the dielectric/air interface and this is therefore the preferred implementation of the Leaky Lens antenna design. However, for applications at sub-mm wave frequencies the realization of the matching layers poses serious technological challenges. Thus, the performance degradation of the planarly fed Leaky Lens antenna without the matching layers has also been quantified. A link between two prototypes has been experimentally characterized. From the measured S-parameters, the pulse preserving property of the antenna link demonstrates the phase linearity and phase center stability of each antenna as well as the spectral amplitude preservation of the link. While the phase preserving properties arise from the Enhanced Leaky Lens radiation mechanism, the spectral amplitude preservation is strictly related to the specific geometry chosen for the dielectric lens.@en

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.@en