GNSS Receiver Testing by Hardware Simulation with Measured Interference Data from Flight Trials

The new signals and services provided by future GNSSs like Galileo and modernized GPS will foster the use of satellite navigation for safety of life applications, e. g. for precision landing approaches of higher categories in aviation. These new signals and services require the development of advanced receiver technologies, which make full use of the performance provided by the new signal characteristics. In aviation environments various potential interference sources exist, which can degrade the performance of receivers. In particular, DME/TACAN is one of the main interference sources in the E5 Galileo band in aviation environments. Therefore, besides functional receiver validation under nominal conditions also the behaviour of the receiver under strong interference conditions must be tested. Software and hardware simulations have shown already that DME interference can reduce the C/N0 of a receiver by some dB even if pulse blanking is applied in the receiver [1], [2]. However, there is a gap of real measurements for flight conditions. Therefore, a flight measurement campaign was performed within the frame of the “ANASTASIA” project, which was financed by the Sixth Framework Program of the EU. During this campaign terabytes of data have been recorded in the E5 band at different flight levels over the Frankfurt DME hotspot area [7]. These data contain numerous recordings of DME and other interferers. The measurements were made with a skyward looking navigation antenna for the Galileo E5/L1 bands. This antenna belongs to a L1/E5 Galileo mock-up receiver for safety-of-life applications which was also developed within ANASTASIA. The receiver that is compliant with current Galileo MOPS standards has been already tested and validated with the help of simulated Galileo signals which were superposed with synthetic DME data [3]. The Galileo signals were generated at the nominal RF carrier frequencies and power levels by the very powerful Multi-output Advanced Signal Test Environment for Receivers (MASTER) [4, 5] of the German Aerospace Center (DLR) and fed into the antenna port of the receiver under test. The synthetic DME data were generated with a programmable signal generator according to the test procedures defined in the Galileo MOPS [6] by EUROCAE WG 62. In this paper a similar approach will be used, but now the synthetic data will be replaced by the recorded data from the flight measurements, which will be again superposed with simulated Galileo signals. The collection of the interference data as well as the test setup will be described and test results will be presented. During the simulations the navigation performance of the receiver under interference conditions will be investigated.