# ADS Simulation: Schematic to find input impedace

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. The point is that, I could not get the same result as the paper reported. Here is their steps and my corresponding results:

1. Their method: Shorterning the Impedance Matching tool, varying Pin. It was said the rectifier operates optimally when the diode's peak reverse voltage, Vr_max reaches Bv(6.4V as in the model). So, they found Vr_max = 6.4V @ 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 6.4V. At Pin = 12.320 dBm, my Vr_max = 4.509V while Vout = 2.599V (Fig.4). Therefore Zin (input impedance) is totally different than the paper's findings. Could anyone tell me what I did wrong?

• There is a wide tolerance on Vbr and Infineon's is Vbr= 4V min @ 100uA yet the typical log curve indicates 5uA at 4V with a shift in the log curve at 2.5V then again at 3.5V Jan 5, 2019 at 3:40
• Thank you very much Tony EE. Could you please explain this in more details? Did you mean Vbr to be Bv, the breakdown voltage of the diode? Jan 5, 2019 at 3:50
• Vbr is the threshold at 100uA similar to Vt threshold for zeners and higher is Vzt for rated at 5mA Jan 5, 2019 at 4:04