Author Topic: Even-odd mode analysis  (Read 2273 times)

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Offline promachTopic starter

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Even-odd mode analysis
« on: March 17, 2019, 03:18:52 pm »
Could anyone show an actual circuit example using the even-odd mode analysis concept ?

By the way, I am reading this useful textronix TDR impedance measurement application note

 

Offline rfeecs

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Re: Even-odd mode analysis
« Reply #1 on: March 17, 2019, 04:22:15 pm »
It is used all the time in analyzing differential pairs, like the inputs to op-amps.  Same as differential mode / common mode.  It is mentioned on the last page here:
http://www.ittc.ku.edu/~jstiles/723/handouts/Odd%20Even%20Mode%20Analysis.pdf

Also used in analyzing coupled transmission lines:
http://emlab.uiuc.edu/ece451/notes/coupled.pdf

https://www.ewh.ieee.org/r5/denver/rockymountainemc/archive/2000/diffimp.pdf

And coupled line structures like directional couplers:
http://www.ittc.ku.edu/~jstiles/723/handouts/Analysis%20and%20Design%20of%20Coupled%20Line%20Couplers.pdf
 

Online T3sl4co1l

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Re: Even-odd mode analysis
« Reply #2 on: March 17, 2019, 10:54:18 pm »
An example would be a VNA with a single measured port and an open/short/terminated far port.  A single port is just an impedance, but by seeing how that impedance changes due to the far port's impedance, you obtain the transfer characteristics (s21).

Tim
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Offline rfeecs

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Re: Even-odd mode analysis
« Reply #3 on: March 17, 2019, 11:30:03 pm »
An example would be a VNA with a single measured port and an open/short/terminated far port.  A single port is just an impedance, but by seeing how that impedance changes due to the far port's impedance, you obtain the transfer characteristics (s21).

Tim

This would only work if you were measuring a reciprical network (S21 = S12).  Then you have three measurements and three unknowns.

For an amplifier or a network with isolators / circulators, it won't work.

Also, I don't see how this is an example of even / odd mode analysis.
 
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Offline promachTopic starter

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Re: Even-odd mode analysis
« Reply #4 on: March 18, 2019, 12:39:24 am »
I just found this nice article about even-odd mode analysis for Wilkinson Power Divider

Before reaching the even-odd mode analysis, I am bit confused with slides 10 and 11.

For slide 10, why "250-ohm transmission line loads in parallel" ?

For slide 11, why "quarter-wave transformer could convert RS to 2RS so we can match input ports" ?
« Last Edit: March 18, 2019, 01:28:53 am by promach »
 

Offline rfeecs

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Re: Even-odd mode analysis
« Reply #5 on: March 18, 2019, 02:23:57 am »
I just found this nice article about even-odd mode analysis for Wilkinson Power Divider

Before reaching the even-odd mode analysis, I am bit confused with slides 10 and 11.

For slide 10, why "250-ohm transmission line loads in parallel" ?

Appears to be a typo.  It should be "Two 50-ohm transmission line loads in parallel"

Quote
For slide 11, why "quarter-wave transformer could convert RS to 2RS so we can match input ports" ?

Convert 50 ohm to 100 ohm on each arm, then in parallel they look like 50 ohms.
 


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