we have a uwb chip which is connected to this lna (along with the referred matching as given in the datasheet ) and then it is given directly to the antenna. no other components.
so on your post 2 regarding the "drop in the gain" since no other components were used in this path, we were not expecting the performance to be this much bad in the recommended frequency range.
also since we have started testing the board now i do not have sufficient data, so i thought s parameter can give pretty good idea. now i am thinking to measure the received power after this lna just to make sure that the problem is in lna block (matching or layout, if it exist even after changing the components than can be more sure that it is happening because of the layout thing as you said). although this same as s para measuement
also pretty sure that the network analyzer was calibrated because repeated the experiment twice from start just to make sure and got the same results also tried also lifting the board and the cable of sna whether any loose connection but the response was still the same, so yeah pretty sure about the measurement.
one thing which i am still puzzled about is that why the s11 got changed as nothing was done on it used the same board just with different cable.(already checked for any short).
can you recommend any measurement or test to confirm the layout or matching issue to be sure why the performance is so poor.