International audienceThis paper presents a flat, high gain, wide scanning, broadband continuous transverse stub (CTS) array. The design procedure, the fabrication, and an exhaustive antenna characterization are described in details. The array comprises 16 radiating slots and is fed by a corporate-feed network in hollow parallel plate waveguide (PPW) technology. A pillbox-based linear source illuminates the corporate network and allows for beam steering. The antenna is designed by using an ad hoc mode matching code recently developed for CTS arrays, providing design guidelines. The assembly technique ensures the electrical contact among the various stages of the network without using any electromagnetic choke and any bonding process. The main beam of the antenna is mechanically steered over ±40° in elevation, by moving a compact horn within the focal plane of the pillbox feeding system. Excellent performances are achieved. The features of the beam are stable within the design 27.5-31 GHz band and beyond, in the entire Ka-band (26.5-40 GHz). An antenna gain of about 29 dBi is measured at broadside at 29.25 GHz and scan losses lower than 2 dB are reported at ±40°. The antenna efficiency exceeds 80% in the whole scan range. The very good agreement between measurements and simulations validates the design procedure. The proposed design is suitable for Satcom Ka-band terminals in moving platforms, e.g., trains and planes, and also for mobile ground stations, as a multibeam sectorial antenna
Abstract-This paper deals with the design of tensorial modulated metasurfaces able to implement a general radiating aperture field distribution. A new aperture synthesis approach is introduced, based on local holography and variable impedance modulation. In particular, it is shown that tensorial metasurfaces can be used to generate general radiating distribution (phase and amplitude). In addition, a step by step algorithm is presented. In order to validate the method, several solutions are presented at 20 GHz which implement aperture distributions able to radiate different beams with general polarization.Index Terms-Metasurface antenna, leaky-waves, periodic surface, surface-waves. I. INTRODUCTIONn recent years, metamaterials have become an appealing subject of research. They are synthetic materials that have exotic properties that cannot be found in nature: double negative materials, negative index materials, left-handed materials… Metasurfaces are the equivalent of metamaterials in the case of 2D structures. The properties of these surfaces are described in terms of tensorial or scalar surface impedances (analogous to the constitutive parameters for volumetric metamaterials). Metasurfaces [9], orbital angular momentum communication [10] or transformation optics [11]-[12].All these works are based on the propagation properties of waves over a sinusoidally modulated impedance [13]. By choosing an appropriate modulated surface impedance, it is possible to control the propagation of SW along a surface or to obtain the transition from SW to leaky wave (LW) modes in order to realize antennas [16], [17].Surfaces composed of sub-wavelength printed elements over grounded dielectric slabs were largely used in order to obtain modulated scalar impedances by locally changing the dimensions of the elements [1]- [15]. Symmetric elements are used to produce scalar impedances [1] [19]. However, the direction of the radiating aperture field (or the equivalent surface current) is dictated by the source [19]. This latter aspect limits the number of possible aperture field distributions that can be implemented.Recently, tensorial metasurfaces were successfully used in antenna design that can radiate CP waves [1], [20] and isoflux shaped beam antennas for space applications [20], [21].The additional degrees of freedom offered by tensorial metasurfaces could be used to overcome the limits of scalar solution by generalizing the procedure presented in [19].Our objective is to propose a systematic procedure for the design of metasurface antennas capable of implementing a general aperture field distribution (amplitude, phase and direction). The principal novelty of this approach is the independent control of the generated aperture field components. This important aspect (critical for general aperture implementation), is achieved by introducing independent modulations of the impedance tensorial components and a new exact holographic formulation. Moreover, average impedance variation along the propagation direction is introduced in ord...
International audienceThis paper deals with the design of scalar metasurface antennas able to radiate a well-polarized beam in the far field or near field zones. The equivalent electric current over the metasurface is used to derive design equations to generate the desired field pattern based on the scalar impedance condition. In particular, it is shown that scalar metasurfaces can be used to generate linear and circular polarizations for a fixed pointing direction in the far field by properly changing locally the scalar impedance boundary condition. In addition, they can also be used to generate normal polarized Bessel beams in the near field region. Several solutions are presented at 20 GHz, with different polarizations and feeders developed in the framework of a two-year research project financed by the French space agency (Centre National d'Etudes Spatiales, CNES). Measurements and full-wave results validate the proposed approach
This paper addresses the RF link budget of a communication system using unusual waves carrying an orbital angular momentum (OAM) in order to clearly analyze the fundamental changes for telecommunication applications. The study is based on a typical configuration using circular array antennas to transmit and receive OAM waves. For any value of the OAM mode order, an original asymptotic formulation of the link budget is proposed in which equivalent antenna gains and free-space losses appear. The formulations are then validated with the results of a commercial electromagnetic simulation software. By this way, we also show how our formula can help to design a system capable of superimposing several channels on the same bandwidth and the same polarization, based on the orthogonality of the OAM. Additional losses due to the use of this degree of freedom are notably clearly calculated to quantify the benefit and drawback according to the case.
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