I am working on a GNSS (GPS and Galileo) RF-FE. I have found the AD8347 part which seems to be a fantastic Direct conversion Quadrature Demodulator. This part comes along with a baseband automatic gain control.
My concern is whether the AD8347 is a good choice for GPS and Galileo signals which are very weak, below themal noise.
The AD8347 has its own AGC loop. Will this AGC loop will also work with this kind of very weak signal below thermal noise? According t datasheet (page 17 of 28) "two signals proportional to the square of each output channel are summed together and compared to a built-in threshold". In my design it would have to work with the square of thermal noise in each I/Q channel....