Active antenna simulation

Hi there. I googled an active antenna schematics and tried to simulate it using ADS. Acording to the result, S11 is 0dB throughout all the band and S21 varies between 11dB and 17dB. The band is 1-30MHz. What's the meaning of this?

The S11 parameter says that all signal is being reflected, but the S21 says that there is a gain greater or equal to 11dB. Is the circuit working as it should? The schematics is attached. Notice that I modeled the antenna as a 5ohms input terminal (the impedance is low because the antenna is electrically small).

To get gain flatness and good return loss over this bandwidth, using this kind of schematic is challenging.
I would recommend using a Norton type preamplifier which has many advantages over this frequency range.

See second and third examples in the link below:
RF Preamplifier