This paper presents a novel type of basis functions, whose spectral-and space-domain properties can be exploited for the efficient method of moments (MoM) analysis of planar metasurface (MTS) ...antennas. The effect of the homogenized MTS is introduced in the integral equation as an impedance boundary condition (IBC). The proposed basis functions are shaped as Gaussian-type rings with small width and linear azimuthal phase. The analytical form of the spectrum of the Gaussian ring basis allows for a closed-form evaluation of the MoM impedance matrix's entries. Moreover, these basis functions account for the global evolution of the surface current density in an effective manner, reducing the size of the MoM system of equations with respect to the case of subdomain basis functions. These features allow one to carry out a direct solution for problems with a diameter of up to 15 wavelengths in less than 1 min using a conventional laptop. The applicability on practical antennas has been tested through the full-wave analysis of MTS antennas implemented with small printed elements.
This paper presents new designs, implementation and experiments of metasurface (MTS) antennas constituted by subwavelength elements printed on a grounded dielectric slab. These antennas exploit the ...interaction between a cylindrical surface wave (SW) wavefront and an anisotropic impedance boundary condition (BC) to produce an almost arbitrary aperture field. They are extremely thin and excited by a simple in-plane monopole. By tailoring the BC through the shaping of the printed elements, these antennas can be largely customized in terms of beam shape, bandwidth and polarization. In this paper, we describe new designs and their implementation and measurements. It is experimentally shown for the first time that these antennas can have aperture efficiency up to 70%, a bandwidth up to 30%, they can produce two different direction beams of high-gain and similar beams at two different frequencies, showing performances never reached before.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Multibeam by Metasurface Antennas Gonzalez-Ovejero, David; Minatti, Gabriele; Chattopadhyay, Goutam ...
IEEE transactions on antennas and propagation,
06/2017, Volume:
65, Issue:
6
Journal Article
Peer reviewed
We explore various possibilities for designing multibeam antennas using a single metasurface (MTS) aperture. Both single-source and multisource feeding schemes are considered. For the single-source ...case, two approaches are investigated. In the first one, the MTS aperture is divided into several angular sectors, each one devoted to the formation of a beam in a given direction. In the second approach, the whole aperture is shared by a superposition of individual modulations, which correspond to those required to obtain beams in the desired set of directions. It is shown that the latter solution provides beams with a higher gain. The configuration based on a multisource feeding scheme is also tailored by a superposition of modulation patterns. The main advantage of the latter approach is the possibility of having one independent beam at a time when each of the sources are active, as opposed to the single-source case where all the beams coexist at the same time. Closed-form expressions are provided for the MTS surface impedance in each of the proposed solutions. The design equations include appropriate amplitude tapering to improve the beam efficiency. Numerical results based on the method of moments are presented for validation.
This paper presents design and analysis methods for planar antennas based on modulated metasurfaces (MTSs). These antennas operate on an interaction between a cylindrical surface-wave (SW) excited by ...an isotropic TM radiator, and an MTS having a spatially modulated equivalent impedance. The MTS is realized by using sub-wavelength patches printed on a grounded slab, thus resulting in a structure with light weight and compact volume. Both features are appealing characteristics for space applications. This paper introduces for the first time an impedance-based amplitude synthesis of the aperture field distribution and shows several new examples of antennas for space applications obtained in recent research projects financed by the European Space Agency.
This article presents a 2-D-beam-steering antenna for Satcom applications based on a simplified Risley scanner, which consists of a leaky wave feed (LWF) and a single deflector fabricated by additive ...manufacturing. Such a configuration simplifies classical Risley scanners, where a source illuminates a combination of two prisms. The pointing direction of the radiated beam is controlled by the relative azimuthal positions between the LWF and the deflector. The LWF comprises a modulated metasurface (MTS) antenna fed by a quasi-optical system to maximize its aperture efficiency. The angular dispersion of the MTS is engineered to reduce the beam squint in the frequency band of interest while preserving the efficiency and compactness of the structure. In turn, the deflector is composed of partially dielectric-loaded metallic waveguides, achieved through the combination of two additively manufactured parts. A prototype validates the concept showing a field of view of 360° in azimuth and 50° in elevation with a maximum realized gain of 25.4 dBi at a broadside of 20.2 GHz.
This communication presents the experimental validation of independent and wide beam scanning with a dual-band transmitarray antenna (TA) in Satcom up- and down-links at Ka -band. The TA consists of ...two subarrays: one operates in the down-link with central frequency at 19.5 GHz, while the other one operates in the up-link centered at 29 GHz. Both subarrays share a common radiating aperture to obtain the compact configuration. The TA layout is made of 1 bit unit-cells and its design relies on the bifocal technique to extend the beam-scanning capability. The proposed bifocal prototype includes 1500 up-link unit-cells in a <inline-formula> <tex-math notation="LaTeX">30\times50 </tex-math></inline-formula> matrix and 1581 down-link unit-cells arranged in a <inline-formula> <tex-math notation="LaTeX">31\times51 </tex-math></inline-formula> rectangular lattice. The 1-D scanning is validated by displacing the feed horn along one direction. We show that the TA beam can be scanned in a ±40° and ±30° independently in each band while keeping a very low scan loss (<2 dB).
The authors present the design, fabrication and testing of a W‐band monopulse antenna. This antenna consists of three main building blocks: an array with 48 × 48 slots, a tapered corporate‐feed ...network and a comparator. The comparator has four input ports to generate sum and difference patterns in orthogonal cardinal planes for monopulse operation. A novel octuple excitation is adopted for the corporate network to achieve a side lobe level lower than −20 dB for the sum patterns and simultaneously reduce drastically the manufacturing complexity. Diffusion bonding technology is used for fabrication. Twenty‐four etched copper sheets with a thickness of 0.2 mm are stacked to realise the prototype. The total size of the antenna is 40.76×40.76×1.51λ03 $40.76\times 40.76\times 1.51{\lambda }_{0}^{3}$, with λ0 being the wavelength at the centre frequency (94 GHz). The antenna presents an isolation better than 12 dB among the input ports in the 84–100 GHz band. The realised measured gain is 40.7 dBi at 94 GHz. The measured 3‐dB gain bandwidth is 17.4%. The difference patterns at 94.0 GHz present null depths of −24.0, −18.0, −17.5, and −17.4 dB, in the E‐, H‐, 45°‐, and 135°‐planes, respectively.
The authors present the design, fabrication and testing of a highly directive antenna at W‐band for MPT. Diffusion bonding is used to integrate a wideband planar monopulse comparator with a novel corporate feeding network (CFN) used to feed a 48 × 48 slot antenna array. The measured realised gain is more than 35 dBi across the full frequency band.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We demonstrate a silicon (Si)-gallium arsenide (GaAs) semiconductor-based holographic metasurface antenna operating at 94 GHz. The metasurface antenna molds the radiated beam by resorting to a ...holographic approach involving the modulation of a guided-mode generated by a pillbox beamformer. The pillbox beamformer is fed by three integrated horns in substrate-integrated waveguide (SIW) technology located in the focal plane of the parabolic reflector of the pillbox beamformer. The three horns correspond to three independent beams and allow beam steering by switching from one feed to another. The proposed metasurface antenna is planar and extremely low-profile, thus suitable for small platforms such as CubeSats/SmallSats. A prototype validates the concept demonstrating a directivity as high as 31.9 dBi and a reflection coefficient lower than −15 dB at 94 GHz.
This communication describes the bandwidth (BW) characteristics of reflecting Luneburg lenses (RLLs) implemented by a bed of nails (BoN). RLLs' beamformers consist of two vertically stacked ...parallel-plate waveguides (PPWs) of circular shape. The bottom PPW contains a graded index (GRIN) medium with azimuthal symmetry to address the rays launched by a point source on a focal line along curvilinear paths up to a corner reflector. After reflection and coupling, the rays emerge collimated in the top PPW. The lens' symmetry allows for generating plane waves with arbitrary directions by just changing the azimuthal position of the source in the bottom layer. The use of BoN with higher symmetries helps to synthesize the refractive index profile in the RLL, which also features high values and increases its operational BW by mitigating frequency dispersion. A Ka-band RLL featuring higher symmetries has been fabricated and tested. Simulations and measurements are in good agreement, showing an overall fractional BW of <inline-formula> <tex-math notation="LaTeX">{\approx } 39\% </tex-math></inline-formula>. This architecture constitutes a metal-only, low-profile beamformer with full azimuthal scanning from 26 to 40 GHz.
Antenna Calibration for Near-Field Material Characterization Hislop, Greg; Craeye, Christophe; Gonzalez Ovejero, David
IEEE transactions on antennas and propagation,
2016-April, 2016-4-00, 20160401, 2016-04, Volume:
64, Issue:
4
Journal Article
Peer reviewed
A novel antenna calibration method is presented for near-field problems, such as material characterization or inverse scattering. The procedure accurately accounts for differences between simulations ...of objects close to antennas and the equivalent experimental measurements. It is based on the method of moments (MoM) solution to surface integral scattering equations. An efficient choice of macrobasis functions (MBFs) is applied to the antenna, which reduces the computational costs by several orders of magnitude. The calibration involves scanning a target of known constitution through the antenna near field, assigning a tuning parameter to each MBF and optimizing said parameters, so as to reduce the error between antenna simulations and measurements. This adjusts the antenna's simulated surface currents, so as to more accurately represent the currents on the experimental apparatus. Thus, an efficient antenna model is obtained, which more accurately represents the real-world antenna. The calibration technique is verified by applying it to the characterization of dielectric objects of known but arbitrary shape.
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