Description of an interference test facility (ITF) to assess GNSS receivers performance in presence of interference

The E5 and E6 bands, which will be used by Galileo, will have to be shared with many ground-based applications in the aeronautical, communications and military domains. It becomes crucial to evaluate the effects of interference from terrestrial sources on the performance of GNSS Receivers. In order to solve this issue, the data recording in different locations (e.g. urban, rural and airport) in addition to the ability to replay and generate GNSS signals with identified interference may help the investigation of advanced interference mitigation techniques and the testing of their implementation in the receivers. The objective of this paper is to present the Interference Test Facility (ITF), a test-bed to assess GNSS receiver performance in presence of interference. This project aimed at developing an interference test facility to be used to generate (simulate or replay) interference and to assess the performance of the GNSS receivers when they have to face an intentional or non intentional interference. The paper introduces the hardware description of the ITF platform and its main functionalities. The paper addresses also a panorama of the potential interference signals in the GPS and Galileo bands and a test campaign that was performed to collect data representative of the interferences that may impact the GNSS receivers in various environments (urban, airport, etc.). This data collection was used further in the ITF project during the validation phase in order to demonstrate the capacity of the ITF platform to replay real interference signals. This validation consisted in demonstrating the equivalence of the impact of simulated and real interferenc

Influence of microstructural heterogeneity on the scaling between flow stress and relative density in microcellular Al-4,5%Cu

We explore the influence of the metal microstructure on the compressive flow stress of replicated microcellular 400-mu m pore size Al-4.5 wt%Cu solidified at two different solidification cooling rates, in the as-cast and T6 conditions. It is found that the yield strength roughly doubles with age-hardening, but does not depend on the solidification cooling rate. Internal damage accumulation, measured by monitoring the rate of stiffness loss with strain, is similar across the four microstructures explored and equals that measured in similar microcellular pure aluminium. In situ flow curves of the metal within the open-pore microcellular material are back-calculated using the Variational Estimate of Ponte-Castaeda and Suquet. Consistent results are obtained with heat-treated microcellular Al-4.5 wt%Cu and are also obtained with separate data for pure Al; however, for the as-cast microcellular Al-4.5 wt%Cu, the back-calculated in situ metal flow stress decreases, for both solidification rates, with decreasing relative density of the foam. We attribute this effect to an interplay between the microstructural and mesostructural features of the microcellular material: variations in the latter with the former held constant can alter the scaling between flow stress and relative density within microcellular alloys