sga4586

SGA4586 from sirenza microdevices as LNA at 1575MHZ? in this freq the NF = 1.8

Is NF the only factor for selecting LNA? or other parameters exist for selection?

You can use this but if you are looking only for a narrow band (i.e. GPS) you can probably do better than NF=1.8 dB. You also have to consider P1dB or IP3. If your input signals may be strong, or have a strong jammer next to a weak signal, your LNA must be capable of amplifying without much distortion or intermod products, or else you'll need a pre-slection filter before the LNA which degrades your noise figure. You need to do a budget analysis of your down-conversion chain to find out how much dynamic range is needed out of each stage.

what part numbers you recommend for LNA in this freq range?

Avago has some GPS LNAs:

http://www.avagotech.com/products/pa...29,C5510,C5509

Also try:

http://www.cel.com