Analyst Script Syntax Answered
I am trying to understand what is going on when I try to modify the syntax in the example from the article "S-Parameters" by Chloe Allison. The script I refer to below is saw_p2.flxinp. I am trying to understand the script so as to be able to modify it by adding a width in the y-dimension and also put a gap of 6.56 um between IDT1 and IDT2.
1. In the script, I am trying to understand lines 85 to 91. For line 86, why is the #keycopy index 2 and 6?
2. If I comment out line 90, I thought IDT2 should not be generated as the copy of IDT1 has not occurred. However, in the "Preview Mode", IDT2 is still generated and also, IDT1 and IDT2 seem to overlap.
3. If line 90 is uncommented, the gap between IDT1 and IDT2 is very large, and looks to be much more than 6.56 um in the "Preview Mode" and I do not understand where this gap comes from.
4. I want to expand the y-dimensions of the model using the variable "edge_y". I have added that to the keypoint in line 95. However, the value of "edge_y" seems to affect the length of the IDT electrodes as well. How do I expand just the substrate in the y-direction by "edge_y?"
5. In the "Preview Mode," is there any way to measure the dimensions so that I know that what I scripted is correct?
6 comments
Hi there,
Thank you for getting in touch.
To answer your questions:
1. You can see the help for keycopy but right clicking the command
Keycopy copies the keypoints from the beginning index to the end index a number of times in a direction. In this example instead of continuing typing fin_width fin_gap over and over to keypoint the fingers we are just copying out the keypoints again. So instead of typing:
we are typing:
For the rest of your questions you reference lines 90 and 95 which are blank in the provided script
Could you point me towards the lines referencing the above image.
Best Regards,
Chloe
I apologize for the mistake. Line 90 should instead be line 88 and line 95 is meant to say line 93. Thanks.
To clarify the keycopy, my understanding is that in line 84, index 1 is referring to $fin_gap2, index 2 is $fin_width, and so on with the final $fin_gap in line 84 being index 5. So I'm just wondering why in line 85, it is being indexed up to 6.
1. Sorry, I misundersttod your question before. You are correct, the keycopy should be indexed from 2 to 5. You can fix this quickly by subtracting $fin_gap from $gap_rad.
2. If you comment out line 88 you also need to comment out lines 200-212 to remove the material assignment of IDT
3. Question 2 fixes this
4. If you add a keypoint you must adjust the site command accordingly i.e. specify the new ijk indices for the substrate and the IDTs
5. You cannot measure the dimensions in preview but you can output the model and measure it in post processor using
data
out modl
end
stop
Thank you. Things are clearer now. Another question is how many cycles are needed to get a proper 2-port s-parameter result? Is there a rule of thumb in determining the length of the transient simulation to run?
We recommend running the simulation until the charge has rang down. You can plot the charge and view via runtime graphics to track this.
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