cascade noise ads

For design of GPS system,
suppose the GPS receiver CHIP's Noise Figure is 3dB, and I need deisgn a LNA with 1.2dB , just like this
LNA + GPS_IC
1.2dB + 3dB
which the total noise figure is 3.2dB?

anybody help me ? thanks

Here is a simple explanation of cascaded noise figure:
http://www.qsl.net/va3iul/Noise/noise.html

Hi,

How much gain do u have in first amp?


David

u need to the read the lecture of the noise of Ali niknijad

http://rfic.eecs.berkeley.edu/~nikne.../lectures.html

it will help a lot

khouly

Read about Friis equation

h**p://www.microwaves101.com/encyclopedia/noisefigure.cfm

What many people fail to include is the losses in the interstage networks. If these have a loss of X dB they are included as a stage with a NF of X dB and a gain of -X dB.

thanks for your help
As i know ,in GSM system, the SAW loss is about 2dB just the SAW's NF is 2dB, if the GSM Transceiver's NF is 2dB, the Total NF is 4dB
But in this GPS case , i need to cal the total nosie Figure from LNA to GPS_IC i need to give the first gain and the second stage gain only give the first and second stage NF can't cal the total nosie figure
here i had distinguished it from your help
thanks again