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ayadi
Joined: 29 Dec 2003
Posts: 3
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 01 Jan 2004 21:32 Microstrip Transmission Line |
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Hi Everyone and thank you for the answers
I am doing my first design in HFSS and it is about a Microstrip TL. I would like to know what is the procedure, what should I look for. How do I analyze it, when can I say "I am done with it and I am satisfied with the results". How far should the simulation results be from the theory?
I appreciate any comment
Regards
sally
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ghb
Joined: 15 Jul 2002
Posts: 82
Helped: 5
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| 02 Jan 2004 14:08 Re: Microstrip Transmission Line |
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ansoft has an example describing this procedure in detail
i dont have the file but its a pretty straightfoward process
you may be able to dl it from their server or someone maybe able to post it for you
good luck
gb
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toonafishy
Joined: 18 Jun 2002
Posts: 425
Helped: 19
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| 02 Jan 2004 21:57 Re: Microstrip Transmission Line |
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Here is how to check your work for this example.
Design your microstrip transmission line. Make it longer than 1/4 wavelength. Plot the S11 on a 50 ohm Smith chart starting at zero Hertz and make a note when the spiral 1st crosses the real axis on the Smith chart. Calculate the reflection coefficient at this point. It will be a real number but the sign may be + or - depending on the angle being 0 or 180 degrees. Calculate the actual line impedance using this formula:
Zline = (50 ohms)*square_root[ (1+reflex)/(1-reflex) ]
To check this, I designed a microstrip 100 ohms, 135 degrees long @ 1GHz. It 1st crossed the real axis at 670 MHz, Z=192.3 ohms. Reflection coefficient calculates to 0.5873 @ 0 degrees.
Zline = (50 ohms)*square_root[ (1+0.5873)/(1-0.5873) ]
Zline = 98.06 ohms
This is also the way to check actual transmission lines using a network analyzer.
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cross coupling
Joined: 22 Jul 2003
Posts: 14
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| 07 Jan 2004 2:24 |
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This is also my question.
I will check tonafishy's method
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chinaing
Joined: 05 Dec 2003
Posts: 35
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| 09 Jan 2004 5:19 |
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Zline = (50 ohms)*square_root[ (1+reflex)/(1-reflex) ]
right it is !!
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