In theory a big phased array of cheap antennas is cheap, in practise not because you need to have equal impedance routing to all of the antennas, which means you need them all to be roughly equidistant to the amplifier. You could probably get away with blowing it up to the size of a large dinner plate, but then you also need a super stiff substrate to avoid flexing, and you need to convince manufacturers that they should make space for this in their design language without any metallic paint or chromed elements in front.
Which car brand do you think would take up these restrictions, and which customer is then going to buy the car with the big ugly patch on the front?
Modern phased arrays can have independent transmitters (synchronized digitally or with digital signal distribution) or you can have one 'cheap and stupid' transmitter and many receivers, doing rx beamforming, and as for complexity you mostly 'just' need to synchronize them (precisely). The receivers can then be made on the very cheap and you need some signal distribution for a central signal processor.
Non-linear or sparse arrays are also now doable (if a bit tricky to calibrate) and remove the need for complete array or rigid substrate or structure.
If you imagine the car as a multistatic many-small-antennas system there's lots that could be done. Exploding the RADAR 'box' into its parts might make it all far more interesting.
I'll admit I'm way over my head on the industrial aspects, so thanks for the reality check. Just enthusiastic, the underlying radar tech has really matured but it's not easy to use if you still think of the radar as one box.
I know even for the small patch antennas we were looking at, the design of the waveguides was insanely complicated. I can't imagine blowing it up to something larger with many more elements.
If you wanted separated components to group together many antennas I suspect the difficulty would be accurate clock synchronization what with automotive standards for wiring. I'm still not sure I understand how they can get away without having rigid structures for the antennas, but this would be a critical requirement because automotive frames flex during normal operation.
Cars are also quite noisy RF environments due to spark plugs.
I guess what you're speaking of will be the next 10-20 years of progress for RADAR systems as the engineering problems get chipped away at one at a time.
Which car brand do you think would take up these restrictions, and which customer is then going to buy the car with the big ugly patch on the front?