i am making a dual band LNA for 2.4GHz and 1.8GHz . i am using switches (NMOS) to tune the LNA between the two frequencies.
my problem is ..... when i tune the LNA to 1.8GHz , the input and output impedances are becoming real at 1.8GHz and matching is also fine but still the maximum gain(S21) is occuring at 2.2GHz but not at 1.8GHz. Actually the max gain should also occur at 1.8GHz