Active DVB-T antenna: Evaluation of noise figure and gain with far field measurements

It is well known that both gain and noise figure depend on the source impedance. Minimum noise figure and maximum gain are two goals that cannot be reached simultaneously. In our particular case the problem consists of the fact that the source is a radiating element, e.g. a bow-tie radiator. All influences in the near field of this element cause a change to the source impedance. Thus, we have to avoid such influences during measurements and this was accomplished by our application of a far field method as described below.