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[SOLVED] Stripline with a crack - simulation error

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waqsoh

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Hi,

I am simulating a simple stripline, which has a crack, in HFSS. The stripline with a crack is shown in Fig 1.
The cracked stripline should block dc or lower frequencies and pass higher frequencies. When the crack width is 0.0002 mm, the simulation works fine. Figure 2 shows the results, where the s21 and s11 parametrs show dc blocking characteristics.
However when i reduce the crack width to 0.0001 mm, the results show as if there is no crack. Figure 3 shows the results for 0.0001 mm case. The s21 and s11 parameters show no dc blocking and high frequency pass characteristics.
The dimensions of the stripline are as following
length = 10mm
width = 0.3 mm
di-electric height = 0.2mm
--- Updated ---

Crack in stripline means that there is a discontinuity of certain width in the stripline
 

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  • crack_Transmission line.PNG
    crack_Transmission line.PNG
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  • 0.0002mm crack.PNG
    0.0002mm crack.PNG
    53.8 KB · Views: 195
  • 0.0001mm crack.PNG
    0.0001mm crack.PNG
    51.8 KB · Views: 156

This appears to be a meshing issue. You should put a seed mesh in the gap (place a vacuum block in the gap(s) and assign a seed mesh to it) with a maximum size of half the gap width; this should solve your problem.
 
This appears to be a meshing issue. You should put a seed mesh in the gap (place a vacuum block in the gap(s) and assign a seed mesh to it) with a maximum size of half the gap width; this should solve your problem.
Thanks. Creating a vaccum box solved the issue. What do you mean by seeding the vaccum box.
 

Name your "crack": microstrip gap capacitor, and you will find a lot of information how it behave at RF frequencies:

Thankz. Yes micorowave gap revealed alot of information. I dont have microwave background.
If you can give guidance in this regard, ot will be really helpful.
Whatif instead of gap there is just a slit(transmission line is still connected). If we vary the depth of slit from small to full length gap. Will it change electrical model from inductor to capacitor. As full length gap represents a capacitor and transverse slit represents inductor.
Any guidance will be really helpful for me.
 

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