Need help with Microwave Office

[ND]

microwave office roughness

I have a task to project some filters i microstrip line.
My problem is in following:
Conductor have distinct ruggedness, and i don't know how to simulate it.

Thanks.

 

[toonafishy]

I think you mean conductor roughness. It is usually specified in the substrate description.

 

[ND]

Thanks, i'll try it.

 

[Abhishekabs]

The surface roughness information can be obtained from manufacturer.
It is usually specified in microinches.
for example
for RT duroid 5870 1/2 OZ (rolled copper foil)
surface roughness is 55 microinches.

You must see datasheet of PCb manufacturer.
roughness changes with type of method used for coper adhesion.

Abhishekabs

 

[ND]

Thanks, but i don't t have specified substrate.

Some specifications for substrate (εr and H) i' m using are given by my professor and hi sad only that copper conductor have surface roughness.

 

[Abhishekabs]

tell me what specifications of substrate you have. I may be able to guess which substrate you are using.
what are you designing?
Surface roughness do not affect much.
It causes power loss. But it will be always there.
If you design a specific circuit for power say 10dBm
& you get O/p as 5 dBm. then the losses are mainly
dielectric losses & surface discontinuity such as bends, corners etc..
I dont think surface roughness will cause a problem at lower frequency.
Use roughness value that i have given you. dont worry.
Important thigngs in microstrip is hight of substrate, εr & copper thicknees sometimes at very high frequency.

 

[ND]

εr=2.33
H=31mil = 787.4um teflon based laminate
t= 18um Copper
Filters (LC, interdigital, combline, parallel coupled)
fo=1ghz, B=10%, S11<-15dB

So far, as i noticed surface roughness does not affect much (as you said).
I increased resistivity for 15% and S21 fall was nearly nothing.
I am using MWO 5.51 (or MWO 2002), and i was unable to find any other solution to model surface roughness.

Thanks.

 

[Abhishekabs]

Your substrate is Rogers 5870. ( My guess)
tan delta= 0.0012
metal roughness= 1.39*10^-3 mm

Best of luck
Abhishekabs

 

[ND]

My professor said that tand=0.0003.

Thanks for the help.

 

[vagarwal]

i dont think you need to wory for roughness at this frequency...