we know that GPS receiver can reach sensitivty of -168dBm, and also it is possible to make receivers with similar sensetitvity can operate at another bands/frequencies .
but I just want to know if possible to build amplifier with input of -168 dBm ? I want increase signal power at some -90s dBm range to make the system able to receive high bitrate at very weak signals "-160s dBm" .
I know the noise will also amplified , but the SNR still unchanged or slightly.
thanks,
Best Answer
-168 dBm is very tiny and equivalent to ~1.7 nV RMS in a 50 ohm system over a measly and pathetic bandwidth of only 3.8 Hz at about 30degC.
If that bandwidth is no good then you'll have to start cooling the radio receiver front end. For instance a 50 ohm resistor generates -168 dBm when cooled to -100 degC but with a slightly improved bandwidth of 6.6 Hz.
Realistically, the "best" formula around that I know of is this: -
Minimum signal power = -154dBm + 10.log\$_{10}\$(data rate)
At a data rate of 1 Hz, mimimum power a receiver needs at about 27degC is -154dBm. At 10 bps this is -144dBm and at 100 bps it's -134dBm.
You can probably see the trend; every tenfold increase in BW requires a signal power that is 10dB more.
At 1M bps, the receiver requires -94 dBm etc...
So, it looks like cooling is the only option but, unfortunately, even when cooled at -272 degC, a 50 ohm resistor will produce -168 dBm over only a 1kHz bandwidth.