In terms of new tech for the RA function, the designers of autonomous vehicles and e-crap spin-offs like emergency braking and lane change assist have developed very capable consumer grade systems that can detect at distance rapidly moving objects, work in congested and all-weather environments, can operate in busy radio clutter even on the same frequencies. These things operate in the 20Ghz or now more commonly around the 75Ghz bands, far away from the frequencies used by mobile telecoms.
E.g.
https://www.bosch-mobility-solutions...-radar-sensor/
They are still a very long way from aviation certification, however most of their development is being paid for by the automotive industry for their own markets. In an aviation context it also suffers from the need to acquire worldwide agreements/standards for frequency allocation use/purpose, which doesn't happen overnight.