Concept of a complex navigation signal generator

The paper presents a concept and the first experimental results of a complex navigation signal generator (CNSG). The generator forms a signal of a predefined radio-navigation beacon received at a specific aircraft position. Recently the beacon is represented by a GNSS satellite and its movement is incorporated. The CNSG consists of the two main parts. The first is the DSP part which physically generates the resulting signal and is based on the FPGA device followed by a suitable DA converter. The second part of the CNSG is a software simulator of the navigation situation. A numerical model of a fixed wing aircraft which is suitable to simulate relative position of an aircraft with respect to the beacon is continually resolving the vector aircraft-beacon. That vector and its time derivatives are then transformed into the resulting amplitude, Doppler shift and phase shift of the signal. The aircraft model is based on a description of dynamic characteristics in form of the equations of motion with respect of the fundamental control forces. The main idea is to keep the model as simple as possible. Therefore only those relevant influences are incorporated.