"Ordinary" antennas are completely passive, just a bit of metal. It's the maths for data recovery and trilateration (not triangulation!) that is processor heavy.
You can buy chips which only do the RF tasks. But you can also buy chips which do “everything”, the RF, the maths, some even do sensor fusion with data from accelerometers and wheel odometry sensors. All in one chip.
You can read here[1] more about what the RF frontend does. This is the crux of it: “Its two-stage receiver amplifies the incident 1575.42MHz GPS signal, downconverts it to a first IF of 37.38MHz, further amplifies it, and then downconverts to a second IF of 3.78MHz. An internal 2- or 3-bit ADC (selectable as a 1-bit sign with a 1- or 2-bit magnitude) samples the second IF and outputs a digitized signal to the baseband processor.”
Thanks for this! It's interesting that the article says doing it in software can be more power efficient than having a dedicated chip for the intermediate frequencies. Does that mean there exists "dumber" RF chips that do less, offloading the math to the main CPU for power savings? It seems like the kinda thing that would be commonplace if so...?
I guess my fundamental confusion is why "listening" to a broadcast signal takes so much power, vs say a FM receiver or passive wifi snooping.
"Ordinary" antennas are completely passive, just a bit of metal. It's the maths for data recovery and trilateration (not triangulation!) that is processor heavy.