Simulation of cutoff frequency on ADS

[Ludovic_29]

Hello everyone.

I am Ludovic from France and new on the forum.

I am currently trying to simulate the cut off frequency of schottky diode (KEYSIGHT HSCH9161) via ADS for a RF to DC converter. However according to specification, it does not seem to give the datasheet result.

I have 2 different models running (spice and small signal).

You will find the schematic attached to this post.

The simulation runs in Harmonic Balance.

The results with SPICE approach give a cut off near 130 GHz which is far worth than the datasheet (200 GHz) and bad results with the small signal approach.

Surely there is something I misunderstood and I hope you will give me a clue in order to solve this problem.

Thanks in advance,

Ludovic.

 

[BigBoss]

-How do you define "Cut-off" frequency ?
-Your HB simulation set-up is wrong. "Frequency" is not a appropriate variable. Using "Parameter to Sweep" block is useless.
-Where are diodes in Small Signal Equivalent analysis set-up ? RLC components do not represent any diode. Instead, a "Linearized Diode Model" should be placed.
-RLC Components represent parasitic/stray elements of a Diode, not diode itself.
-What is the aim of using forward and reverse biased diodes simultaneously ? It doesn't make sense.

 

[Ludovic_29]

Thank you for your reply BigBoss.

The goal of the simulation is to define until which frequency the schottky diode could be used. Because of the RLC elements, it should have a cut off frequency that will not permit the diode to work properly, am i right ? This is the reason I used the frequency as a parameter to sweep.

For the small signal equivalent, it is the model of the diode given in the datasheet of the schottky diode with a zero bias voltage.

The spice model is from an old datasheet from the HSCH9161.

Regards,

Ludovic.

 

[BigBoss]

They have already mentioned that the Diode can work up to 110 GHz. You will accept this statement and build up your circuit. SPICE model can be valid-perhaps- 50 GHz or more or less, this is just for "getting an idea" not for practical results.
Simulations are not %100 valid in ALL cases, there are very critical deviations and process variations and other stuffs and those are not included in models.