Retrodirective antennas send signals back to the direction of communication partners without knowing their exact position and without performing complicated direction of arrival estimations. They can offer directive communication links to moving partners mostly by conjugating the phase of the incoming signal for each antenna element. Thus, they are a strong candidate for different high-rate data links in satellite communications or safety-of-life applications using HAPs. Different architectures of varying complexity have been proposed for retrodirective antennas. However, they suffer from limitations that constrain their usage for practical applications. E.g. it is not possible to realize a large frequency difference between received and transmitted signals which is important for satellite communications.
The goal of the project RADIANT is to develop and validate new retrodirective antenna architectures that are simpler than digital beamforming antennas or phased arrays but free of the severe limitations of current retrodirective antennas. The proposed solutions are carefully analysed by detailed numerical simulations that cover the whole signal chain, including antenna, RF front-ends and digital signal processing. Co-simulations between different programs are used, e.g. electromagnetic field simulators and signal processing tools. Thus, the joint behaviour of the system parts can be analyzed. Validation of the most promising architectures is done by extensive tests including monostatic and bistatic far-field measurements of functional demonstrators.