I think I coundn't explain the problems.
1. The PLL is used in GPS receiver not as Frequency demodulator but to generate LO frequency 1.4GHz.The confusion is "PLL locked at 1.4Ghz " means refrence input to PLL is 1.4GHz?(Triple conversion using fixed LO frequency architecture)
2.I have read "PLL is used as LO & Clock generator in digital system".For the 1st stage mixer we have RF input (1.5GHz)& LO(1.4Ghz).Its double balanced open collector mixer.Now is it a mixer or modulator??
3. Since we have a VCO, does it ensures it's analog PLL? What about the Phase Dector then? Is it a multiplier?