ADS Simulation: Schematic to find input impedance

I'm following a paper, using ADS, to find the input impedance of a shunt Schottky diode. The paper's schematic is Fig. 1, and my schematic is Fig. 2.

I could not get the same result as the paper reported. Here are their steps and my corresponding results:

1. Their method: Shortening the Impedance Matching tool, varying Pin. It was said the rectifier operates optimally when the diode's peak reverse voltage, Vr_max reaches Bv (6.4 V as in the model). They found Vr_max = 6.4 V @ Pin = 12.320 dBm (Fig. 3).

2. My results: Vr_max = peak(Vd). With Pin in the range (-5, 15), my Vr_max could not reach 6.4 V. At Pin = 12.320 dBm, my Vr_max = 4.509 V while Vout = 2.599 V (Fig.4).

Therefore Zin (input impedance) is totally different from the paper's findings. Could anyone tell me what I did wrong?