Efficient DME/TACAN Blanking Method for GNSS-based Navigation in Civil Aviation

摘要

In the context of the evaluation of the GNSS L5/E5a interference environment dominated by DME/TACAN and JTIDS/MIDS pulses, RTCA DO-292, 2004 [1] proposes a model to compute the blanker duty cycle and the equivalent noise level contribution of the non-blanked interference; however the corresponding blanker model is not clear. That blanker cannot be a pure envelope detector triggering the blanker by comparing at each epoch the magnitude of the envelope of each individual single interference pulse to a threshold, as it may have been assumed in [1]. Also, for standardization purposes, it is proposed to define a very simple mechanism validating the operation of a GNSS receiver in the L5/E5a environment, also defined as a minimum blanker. In this paper, three simple blanker mechanisms were tested assuming the US hot spot DME/TACAN environment: Instantaneous blanker, Average power and Blank-and-Hold blankers. This study shows that the Instantaneous Blanker is not providing adequate performance, nor the Blank-and-Hold mechanism. It also shows that the Average Power blanker with a window of 0.5 μs allows to obtain performance very similar to that of the analytical model based on the [1] blanking methodology.