A methodology to benchmark flexible payload architectures in a megaconstellation use case

International audienceThis paper proposes a methodology to benchmark satellite payload architectures and find the optimal trade-offs between high flexibility and low complexity. High flexibility would enable the satellite to adapt to various distributions of user terminals on the ground and fulfill the data rate demand of these users. Besides, low complexity is required to keep satellite networks competitive in the context of emerging 5G networks. To estimate the flexibility of a payload, an indicator to characterize the non-uniformity of user distributions is proposed. Each benchmarked payload may be characterized by a graph relating the throughput to this parameter further denoted mu. The payload provides the same throughput trends for different scenarios of user distributions with the same mu parameter. As a consequence, the average capacity of the system may be estimated by (a) calculating the probability distribution of mu over the orbit and (b) integrating the throughput based on this payload response. It thus results in a straightforward way for benchmarking payloads directly on an estimation of the averaged capacity, accounting for the user distribution over the earth. A simulation platform has been developed to characterize the payload throughput including the implementation of a resource allocation algorithm that accounts for constraints of various payloads. Using this definition and the developed tool, we benchmark a bent-pipe architecture, a beam hopping architecture and a hybrid beam-steering architecture for a LEO megaconstellation use case. The methodology showcases the interest for investigating different payload architectures depending on realistic traffic scenario analysis

Dual-Polarized Aperture-Coupled Patch Antennas With Application to Retrodirective and Monopulse Arrays

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Circuit Modeling of 3-D Cells to Design Versatile Full-Metal Polarizers

International audienceAn original mechanism is here proposed to achieve polarization convertion from linear to circular with the use of full-metal polarizing screens. Such screens are self-supported and conceived from the periodic arrangement of 3D unit-cells. They are built from sections of rectangular waveguides operating below cutoff frequency and loaded with slotted discontinuities. The polarizer operates in transmission: the discontinuities are responsible for both its high return losses and the conversion of the impinging linear polarization to circular. Two types of 3D-cells are presented, both of them are analyzed and designed through equivalent circuit models. These models have been thoroughly built in order to capture all the phenomena underlying the discontinuities' behavior. The characterization of the first cell is fully done analytically whereas the second cell needs reduced help from a full-wave solver. Furthermore, the circuit models allow simple design guidelines to be identified for this type of polarizer. Two designs are performed operating in Ka-band, proving that an extension of the operation bandwidth (axial ratio and S11) to 11% is possible by employing the second cell

Matching and gain enhancement of leaky-wave dielectric horn antenna

By flaring a dielectric waveguide in the H-plane, an H-plane dielectric horn is formed, which could be directly excited by an SIW feed. However, matching and radiation performances are poor due to the thinness of the substrate. To improve these performances, some periodic parallel strips are printed both on the top and bottom planes of the dielectric horn. These strips guide and leak the electromagnetic waves gradually along the horn, finally enhancing the end-fire radiation both in H-plane and E-plane. Moreover, they increase the impedance bandwidth up to 40% in Ka-band, and improve the realized gain by more than 2 dB. Indeed, a gain of 14.9 dBi is achieved at the center frequency, with a front-to-back ratio of 33.8 dB, and a side-lobe level of -22.9 dB in the H-plane. With these quite impressive performances, the proposed leaky-wave dielectric horn antenna is very compact, low cost, and easily integrated

Circuit-based synthesis of a reflectarray

International audience—This paper presents a new methodology for synthesizing reflector panel based on a fully analytical model. The present methodology is applied to the simple case of a two levels reflector panel consisting of metallic strips unit-cell. The model generates a maximal error of 3.39 degree on the reflection phase

Synthèse indépendante des coefficients de réflexions de la matrice de diffusion d'une méta-surface

National audienceCette communication présente la synthèse d'une cellule réflectrice afin d'approcher une matrice de diffusion voulue. Cette étude est motivée par le besoin grandissant de contrôler le coefficient de réflexion en co-polarisation des méta-surfaces ainsi que le couplage entre polarisations incidente et croisée, en amplitude et en phase. L'utilité de la synthèse est montrée avec une application de conversion de polarisation linéaire en polarisation circulaire, la bande sous 3dB du rapport elliptique obtenue est de 17% autour de 16GHz. Toutes les simulations sont effectuées sous CST