Passive/metastatic radar is much cheaper and likely to be more effective for many years to come. Also, passive can be cheaply deployed using COTS hardware and Gnu Radio. An open Ultra-Wide-Band transceiver chip set could not only enable excellent covert comms. but also, when several transmitters using them are time locked for coherence, can be used for passive radar. On Tue, Apr 24, 2018, 8:01 PM jim bell wrote:

Canada developing quantum radar to detect stealth aircraft - http://www.bbc.co.uk/news/technology-43877682