do we have any sources / research papers / proof-of-concept for active cancellation ? I've always been skeptical because phased arrays have worse gain for large deviations (https://www.radartutorial.eu/06.antennas/Phased%20Array%20Antenna.en.html) which means good covering for any incoming wave may require conformal radar arrays in several different places, which we have never seen for all of those planes.