S11 = 50-j200 (315MHz) and S11 = 50-j145 (433.92MHz)
L2 is thus needed to match the LNA to 50 Ohms (or other antenna impedance). Therefore, in order to match the MAX1470 to a 50-Ohm antenna, one only needs to cancel out the -j term. This can easily be accomplished with L2, which would need to be (at 315MHz).
L2 = 200/2 3.14 315e6 = 100nH
A look at the S11 with the help of the network analyzer will allow this to be tuned even better. Set the test port power of the network analyzer to -30dBm so as not to saturate the input stage. Figure 2 shows the S11 of a not so perfectly matched board. The S11 is tuned to 355MHz instead of 315MHz. [...]