https://ria.asturias.es/RIA/handle/123456789/6462 2026-02-26T15:05:40Z https://ria.asturias.es/RIA/handle/123456789/12386 Title: Wideband Shaped-Beam Reflectarray Design Using Support Vector Regression Analysis Authors: Rodriguez Prado, Daniel; López Fernádez, Jesús Alberto; Arrebola Baena, Manuel; Rodríguez Pino, Marcos; Goussetis, George Abstract: In recent years, machine learning techniques (MLTs) have been applied to accelerate analysis and design of electromagnetic devices. Algorithms such as artificial neural networks or support vector machines for regression (SVRs) have been proposed for the design of large reflectarrays for space applications at a single frequency. However, multi-frequency optimization of such large antennas has not been tackled with MLTs. In this letter and for the first time, we propose a technique based on the use of SVR analysis to obtain the reflection coefficients to accelerate the design of a very large shaped-beam reflectarray for direct broadcast satellite in a 15% bandwidth. An in-house method of moments based on local periodicity is employed to generate samples to train the SVRs for each considered frequency. Then, the surrogate model is used for a design at central frequency, which is used as starting point for a wideband design procedure that is accelerated more than an order of magnitude without a significant loss of accuracy. It is shown that, by virtue of the proposed methodology, the minimum copolar gain in the coverage zone is improved more than 10dB at the upper frequency while maintaining a computationally efficient design procedure. 2019-11-01T00:00:00Z https://ria.asturias.es/RIA/handle/123456789/11945 Title: Wideband Reflectarrays with Improved Performances for Space Applications Authors: Rodriguez Prado, Daniel; Arrebola Baena, Manuel; Rodríguez Pino, Marcos Abstract: This work presents the design and optimization of two very large reflectarrays with improved polarization purity for Direct Broadcast Satellite missions in dual-linear polarization. The first antenna is a one-meter contoured-beam reflectarray working in a 15% frequency band providing European coverage. The second reflectarray has a diameter of 1.1 meters and provides coverage for South America in transmit and receive bands. In both cases, the design approach is as follows. First, a layout is obtained at central frequency. Then, using a limited number of degrees of freedom (DoF), a copolar only optimization is carried out in the whole frequency band. Finally, increasing the number of DoF, cross-polarization requirements are also included in the optimization. For the reflectarray with European coverage, a minimum copolar gain of 28 dBi is obtained inn the whole band, with XPI values higher than 31.5 dB. On the other hand, the reflectarray with South American coverage complies with all copolar and cross-polarization requirements with a loss budget of at least 0.49 dB in both receive and transmit bands. 2019-10-01T00:00:00Z https://ria.asturias.es/RIA/handle/123456789/10549 Title: A very simple analog control for QSW-ZVS source/sink buck converter with seamless mode transition Authors: Martín, Kevin; Vázquez, Aitor; Arias, Manuel; Sebastián, Javier Abstract: A simple, analog, control circuit is proposed for seamless transition between source and sink modes in a Quasi-Square-Wave Zero Voltage Switching (QSW-ZVS) source/sink buck converter. The inductor current is controlled by a variablewidth hysteretic current mode control. The upper and lower bounds of the hysteretic band are clamped to ensure QSW-ZVS operation with a single current command from the control loop and independently from the power flow direction. This enables the control of any PWM converter able to operate in QSW-ZVS with a single control loop. If the proposed circuit is used, using a complex multi-mode or look-up-table based digital control is no longer required, simplifying the implementation and lowering the cost of the converter. A 50 W buck converter is built to demonstrate the proposed control circuit and experimental measurements are shown to verify its correct operation. 2018-06-28T00:00:00Z https://ria.asturias.es/RIA/handle/123456789/6703 Title: Verificación del Modelo Analítico de Pérdidas en Conmutación para MOSFET de Superunión con modelado de Capacidades No-Lineales y Diversificación de Corrientes Authors: Castro, Ignacio; Roig, Jaume; Bauwens, Filip; Lamar, Diego G.; Rodriguez, Juan; Vazquez, Aitor 2015-07-09T00:00:00Z