On: Why Are Ultrasound Machines So Expensive?

[hwillis]

Mixing is only useful when the change in the signal is slow. In ultrasound you're operating around single wavelengths so you can't mix down.

[highd → hwillis]

FMCW systems would be slowly changing around the central wavelength. It wouldn't work for pulsed systems, though - I'm not sure what's more common.