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Transition Microstrip to Rec waveguide using HFSS

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Asim Ali Khan

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Dear All

I am dealing with the transition from microstrip line to waveguide both are on substrate (PCB). I hv poblem assigning the excitation for my design. Actually I have three layers in my design one is the PCB substrate and the other two are copper layers sandwitching the substrate. How should I assign the excitaion should I select all three faces or just the substrate.

Thx in advance
Bye
 

First, you should build the electromagneticl model with back-to-back transition (that is, microstrip-transition-waveguide-transition-microstrip). In addtion, air box should be used for the open structure.

Secondly, you use the waveport for the excitation of microstrip.

I hope this can help you.
 
I concur with Burtons comments. You would also be well served if you read the section in HFSS where they discuss impedance calculation.

There are several twists with waveports that can easily be avoided.
 

i think you should search and get some info about SIC concept.

its pretty bulky,transition to microstrip from waveguide...
 

Thx for ur suggestions guys. Let me clear one thing in my case both the waveguid and microstrip line are on the same PCB i.e. integrated on PCB.

But I do not understand "SIC" wht is this?

Added after 10 minutes:

Thx for ur suggestions guys. Let me clear one thing in my case both the waveguid and microstrip line are on the same PCB i.e. integrated on PCB.

But I do not understand "SIC" wht is this?
 

Asim Ali Khan said:
Dear All

I am dealing with the transition from microstrip line to waveguide both are on substrate (PCB). I hv poblem assigning the excitation for my design. Actually I have three layers in my design one is the PCB substrate and the other two are copper layers sandwitching the substrate. How should I assign the excitaion should I select all three faces or just the substrate.

Thx in advance
Bye
Click to expand...

Microstrip port:
Can't you just put a layer of air above the PCB and set a waveport over the entire end of problem, which includes the air, PCB and the microstrip line? Then set your impedance line between microstrip and lower ground plane. Remember to set the waveport to include the face of PCB and air.

Waveguide port:
I would just set the waveport to cover the area of PCBs, from lower ground to upper ground. You might need to put small metal bodies on each end of your waveguide at the port face to connect the top and bottom ground planes. I think you could just put your impedance line to stretch from top to bottom ground plane near the middle of the waveguide.

Hope this helps...

--Max
 
I keep re-reading your question and your objective is not clear to me. Are you trying to transition from microstrip to rectangular waveguide? That is often done.

Or are you trying to transition from microstrip to strip line? This is also possible.

Part of my quandry is that when someone says waveguide they usually (but not always) are referring to rectangular waveguide. I am trying to understand how that fits with your comment about three conductors (usually the situation with stripline).

Or do you have something else in mind? Maybe microstrip to some kind of dielectric filled waveguide in the PCB? If that is the case you open the door to a discussion of via's (blind, buried, and through).

Your intent is not clear to me.
 

Dear Azulykit

I am talking about microstrip to SIRW structure. Now I have a problem with HFSS simulation. When I run the validity check it gives me all ticks but when I start simulation it gives me error saying "Not enough triangular structers to model blah blah ...."

Secondly, I have designed the structure such as substrate (a box) is sandwitched b/w to conducs (rectangles) for micro strip operation I have to make the base conductor ground. Should I separate the microstrip base(ground) to the SIRW base?

Asim
 

Mr. Khan,

there is another way of reconstructing a waveguide on a pcb. they called it substrate integrated circuits (SIC). im actually working on that.

you may contact me personaly.
bkadi(AT)gyte.edu.tr
 

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