saam wrote on Sep 12th, 2010, 1:10am:please can anyone clarify my basic Q'ns so that i can move in rf world
I don't think so.
With understanding only these easy questions, you can not still even touch a door of RF World.
saam wrote on Sep 12th, 2010, 1:10am:(1) matching impedance of LNA depends on the type of antenna we are using..
is my statement is correct???
Correct.
saam wrote on Sep 12th, 2010, 1:10am:and 50ohms for which antenna???
Impedance of conventional commercial product's antenna is 50ohm.
http://www.designers-guide.org/Forum/YaBB.pl?num=1245527790saam wrote on Sep 12th, 2010, 1:10am:(2) If there is no filter between antenna and LNA
then what about the impedance matching for LNA ???
You have to match input impedance of LNA to output impedance of antenna.
saam wrote on Sep 12th, 2010, 1:10am:(2)(3) If there is a filter between antenna and LNA
then as matching for antenna-fliter and filter-LNA.
You have to care about termination's condition of filter.
So you have to apply it as matching for antenna-filter and filter-LNA.
saam wrote on Sep 12th, 2010, 1:10am:(3)(4) what is the effect of transmission line or co-axial cable on impedance matching???
Consider a behavior of Γ in smith chart.
If line is perfectly lossless, Γ keeps a constant magnitude(that is a constant VSWR) and changes its phase.