LDACS Demonstrator

In the development of LDACS, testing and verification plays a crucial role. Therefore, DLR has developed an experimental setup for the generation and processing of LDACS radio signals in the laboratory, which we call the LDACS demonstrator.

It consists of a transmitter and a receiver setup, both comprising an analogue frequency conversion and amplification unit, as well as a digital signal processing unit.

Figure LDACS Demonstrator

The signal processing system contains D/A and A/D converters to interface with the RF frontend at an intermediate frequency of 30 MHz, and uses FPGA technology for signal processing in the digital domain. With the FPGA design developed at DLR, any LDACS signal according to the published specification can be generated. The RF frontend handles analogue signal amplification and frequency conversion. It can be tuned to channels in the aeronautical L-band between 985 MHz and 1072 MHz with a 500 kHz channel spacing. Thanks to its duplexer filters, it permits full-duplex operation with frequency-division duplexing (FDD) as per the LDACS specification.

The LDACS demonstrator has already been used successfully in tests of the LDACS communication performance as well as in compatibility tests with legacy aeronautical radio equipment. The latter were conducted at the laboratories of DFS, the German ATC authority and investigated interference between LDACS and the navigational Distance Measurement Equipment (DME). As a first result, it could be confirmed that LDACS can operate under severe interference from DME. Secondly, important data has been collected for the establishment of the necessary separation criteria which warrant the correct operation of both systems.

Figure LDACS Demonstrator 2

Further technical details on the implementation of the LDACS demonstrator and on the compatibility experiments have been published in several papers presented at international conferences.

Recently, industry has taken over the further LDACS demonstrator development. Frequentis AG is building an LDACS demonstrator within SESAR and Rohde & Schwarz within the German national project MICONAV (Migration towards Integrated COm/NAV Avionics). These industrial LDACS demonstrator will be used for future compatibility testing and flight trials.

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