How can I bias the varactor in ADS
The physical model is showed in the below Fig
How can I bias this varactor?
I should apply voltage bias to this circuit
I want to get curve of sweeping Capacitor vs. voltage bias in ADS
So what is the problem? You can a DC_Block element or an inductor.
I simulate it according to the below figure
Base on the following formula, the curve of capacitor vs. bias is shown
but the result isn't correct :(
which part of simulation is wrong?
There's no variable (voltage dependent) capacitance in your model.
can you try placing term 1 after DC feed?
How can I define variable voltage? I just sweep a DC source
I eliminate DC feed and DC block in this schematic but result doesn't change
I'm not talking about setting variable voltage, that's fine in your simulation setup. But I can't see how you are making "Cx" voltage dependent.
However, as pragash mentioned, even if you have implemented a reasonable variable capacitance in your circuit, you won't see it's effect because the voltage across the varactor model is always zero. Insert a termination, e.g. a choke, or remove DC_block1.
How can I make "Cx" voltage dependent?
I did this simulation based on example of ADS
It's easy. Just use the data in the datasheet.
Such as in some varactor datasheet, it says:
Vr(V) CT(pF)
0 8.86
0.5 6.17
1 4.37
1.5 2.96
etc.
So you can make a curve with the data and calculate the CT at any voltage.
Do you think is it oK?
And your design is lack of DC loop for varactor.
Keep in mind to distinct AC and DC, and make loops for them respectively.
No No
I want to find these values I just use some data of datasheet such as V(j) C(j) and M for drawing curve of C vs. V.
If I have these values, I won't need any more data
I should bias figure 1 and then getting its curve based on this schematic
If you check the ADS help for keyword "varactor", you will find multiple documents and this example
SHPEESOF_DIR/examples/Tutorial/SDD_Examples_wrk