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red5000
Joined: 06 Nov 2006
Posts: 120
Helped: 32
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 18 Dec 2008 11:37 help to calculate propagation constant |
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| how calculate propagation constant from S parameters, and thanks.
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somada141
Joined: 13 Mar 2008
Posts: 65
Helped: 23
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18 Dec 2008 12:16 help to calculate propagation constant |
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| If you mean β then i think it is b=2*pi/λ
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red5000
Joined: 06 Nov 2006
Posts: 120
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19 Dec 2008 18:39 help to calculate propagation constant |
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| but if i want calculate β from the field how can i proceed to calculate it ? for example from fdtd
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somada141
Joined: 13 Mar 2008
Posts: 65
Helped: 23
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19 Dec 2008 19:52 help to calculate propagation constant |
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Well I suppose that since in FDTD you know the used frequencies then you know the wavelength range. For example you may know that λ is between 1 and 5 mm hence you know the propagation constant for each frequency (I believe every freq has its own β)...However let me check it out and I'll come back to you ASAP
Added after 13 minutes:
Well according to Pozar there may be another way...
The formula for the resistance of a material is given by this :
η=sqrt(μ/ε)=ωμ/β
where μ is the permeability of the material and ε the permittivity. Of course ω is ω=2πf.
Hence you can easily calculate β for any media like this.
Of course the propagation constant is different for every frequency and every different material.
So in FDTD you'll have a diffrent β for vacuum and different for other materials for any frequency...
Lastly you can calculate η and therefore β using field values like this:
η=Ex/Hy or two filed components perpendicular to each other.
However I strongly suggest finding β for every material using the first formula since you'll have to do it once for every frequency and you won't have any error due to FDTD inaccuracies...
Hope it helps...If you need any help plz ask...
(PS. Thnx for the helped me. Glad to see there is some recognition)
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red5000
Joined: 06 Nov 2006
Posts: 120
Helped: 32
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20 Dec 2008 18:29 help to calculate propagation constant |
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| but some dispersive materials like ferrites, the wave lenght change when the field pass this materials, then we don't can calculate the beta from the classical formulas, and we must use the numerical solution.
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Abhishekabs
Joined: 12 Jan 2007
Posts: 727
Helped: 84
Location: India
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22 Dec 2008 7:02 help to calculate propagation constant |
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| red5000 wrote: |
| how calculate propagation constant from S parameters, and thanks. |
I don't think you can calculate Beta from S parameters.
You can calculate impedances, Return loss etc. using S parameters data.
According to my info Group Delay is calculated in simulation.
For example HFSS.
Refer following document for understanding.
http://web.uct.ac.za/courses/rfmicrosys/NOTES/group.pdf
Added after 1 hours 25 minutes:
http://home.comcast.net/~chorneys/Professional/GroupDelayinWaveguides.pdf
Also refer this
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22 Dec 2008 7:02 Ads |
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somada141
Joined: 13 Mar 2008
Posts: 65
Helped: 23
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22 Dec 2008 20:24 help to calculate propagation constant |
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Well after questioning a professor the answer was:
"You don't calculate the propagation constant from the S parameters. You calculate the ABCD prameters from the S ones and then using those and by employing phase unwrapping you can calculate the propagation constant"
Up to the ABCD part things are easy since you use standard formulas...
Beyond that, it is beyond me. I don't know much on this but if I find out more I'll inform you...
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prakashmedical
Joined: 07 Dec 2008
Posts: 2
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23 Dec 2008 2:47 Re: help to calculate propagation constant |
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| Can u send me the circuit diagram of shortwave diathermy...
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somada141
Joined: 13 Mar 2008
Posts: 65
Helped: 23
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23 Dec 2008 8:16 help to calculate propagation constant |
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Shortwave diathermy?
This post is for propagation constant. What do you mean?
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red5000
Joined: 06 Nov 2006
Posts: 120
Helped: 32
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23 Dec 2008 11:50 help to calculate propagation constant |
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| thank you for your help somada141
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somada141
Joined: 13 Mar 2008
Posts: 65
Helped: 23
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24 Dec 2008 16:06 help to calculate propagation constant |
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| No big deal red5000. Sorry I could be of more help but I haven't delved so far in FDTD yet. If I can help in any way don't hesitate to ask
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red5000
Joined: 06 Nov 2006
Posts: 120
Helped: 32
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24 Dec 2008 20:52 help to calculate propagation constant |
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| i'm looking for web site who give any pattern program in fdtd and specially for waveguide, if you know one help me please.
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Zottiri Kusuta
Joined: 02 Sep 2005
Posts: 75
Helped: 13
Location: Columbus, OH
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25 Dec 2008 2:09 Re: help to calculate propagation constant |
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i have explained this in another post:
http://www.edaboard.com/viewtopic.php?p=1087055
edit: you need to calculate the transfer (ABCD) matrix from [S] matrix. for 2 port networks this is easy using formulae from books. for more ports, you can still find a formula of conversion.
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