Programa del congreso

Magnetic coupling between components may greatly reduce performance of compact electromagnetic interference filters at frequencies above several hundreds of kilohertzs or a few megahertzs. This work analyzes the performance of shielding strategies based upon the use of copper bands (high-conductivity material) and/or flexible ferrite sheets (high-permeability material) to improve the attenuation provided by these filters.

We make use of a high-frequency circuit model of the filter and an advanced search algorithm to identify the condition of partial shielding as the main cause of the limited shielding performance of high-conductivity materials and to quantify the reductions in the mutual inductances between the components of the filter that can be obtained by using alternative arrangements of the shielding structures that include ferrite sheets. Measurements on several filter prototypes demonstrate that the shielding techniques proposed here can provide 20 to 30dBs increase in the attenuation provided at high frequencies by the electromagnetic interference filter for differential mode noise.

Testing the immunity to conducted radiofrequency disturbances, induced by radio-frequency fields, is fundamental within the electromagnetic compatibility assessment of devices having input and/or output cables. This procedure requires assuring the repeatability and accuracy of the test level applied, that is, the voltage and power of the signal injected into the equipment’s cables when these tests are performed. During a preliminary calibration, different instruments could be employed to measure and adjust the disturbance voltage to the corresponding test level, typically, power meters, test receivers or spectrum analyzers. In this paper it is proposed to use oscilloscopes as measuring device and the calibration method has been adapted accordingly. Results indicate oscilloscopes enable valid and time efficient measurements of the radiofrequency voltage signals involved in the tests according the EN 61000-4-6 standard method, with comparable accuracy at lower costs, while it provides further measurements analysis capability and increased robustness.

La tendencia actual a desarrollar dispositivos electrónicos cada vez más pequeños, con mayores funcionalidades y mejor rendimiento provoca que las interferencias electromagnéticas (EMI) se conviertan en un gran problema. El apantallamiento contra las EMI es un aspecto importante que hay que tener en cuenta en el proceso de diseño de un dispositivo electrónico. Cuando el problema se detecta en etapas posteriores una de las técnicas más empleadas se basa en recurrir al uso de board-level shields (BLS). En este artículo se describe un método de medida empleado para la caracterización de una shielding cabinet sin juntas basado en la medida de las pérdidas por inserción (insertion loss). Además, se incluyen las simulaciones realizadas para comprobar cómo afecta el efecto de las aberturas en la efectividad del apantallamiento de la cabinet.