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| | Please help me wilkinson power splitter/combiner questions - RF Cafe Forums |
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Guest Post subject: Please help me wilkinson power splitter/combiner questions. Unread postPosted: Wed May 25, 2005 5:29 am
Thingking of 2-way equal wilkinson power splitter/combiner and setting port 1 input(output),port 2 output(input), port 3 output(input)
1. I just know the banlance resistor is 100ohm, but how to get this value by mathematic formula? 2. All these three ports are matched. Looking into port 1, I can understand why it is matched ( port 2 resistor and port 3 resistor at joint are the same 2Z0, and 2Z0//2Z0=Z0). But I can't understand why it is matched looking into port 2 or port 3? 3. Why say the balance resistor provide good isolation? How to compute? 4. If power P enters into port 1, I know the power of port 2 and port 3 are the same, P/2. But if power P enters into port 2, how to compute the power of port 1, port 3, and balance resistor? 5. If port 1 mismatch, how to compute the power consumed by the balance resistor? If port 2 or port 3 mismatch,how to compute the power consumed by the balance resistor?
If possible, Please give me detail information. These questions puzzeled me many days. Many thanks!!! My email is: sunstar16@163.com
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Guest Post subject: Unread postPosted: Wed May 25, 2005 9:44 am
You need to look for EVEN-ODD mode analysis.
You will find this analysis in "Microwave Engineering" from POZAR
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malvinas2 Post subject: Unread postPosted: Fri May 27, 2005 4:09 am
Or just 'google' around:
http://www.google.de/search?hl=de&q=wilkinson+power+splitter&meta=
gives you plenty of useful links.
BTW: There'll be always power consumed by the resistor, without the resistor the divider wouldn't be matched at all ports. You've to read something about "S-Parameter" (scatter parameter).
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Guest Post subject: Unread postPosted: Fri May 27, 2005 9:30 am
Malvinas,
I do not understant why you say there is alway power dissipated in the resistor.
If the system is perfecly balance, I mean same amplitude, same phase at both outputs(inputs), same impedance, then there is no dissipation in the resistor, since both of it's terminals are at the same potential
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malvinas2 Post subject: Unread postPosted: Fri May 27, 2005 10:27 am
All three ports matched means: Sii=S11 = S22 = S33 = 0
/ 0 S12 S13 \ S =| S21 0 S23 | (3) \ S31 S32 0 /
no dissipation is expressed by
S_transposed_conjugated * S = E (unity matrix) (4)
e.g.:
|S21|² + |S31|² = 1 (5) |S12|² + |S32|² = 1 (6) |S13|² + |S23|² = 1 (7) S32* S31 = 0 (8)
Symmetry:
Sik = Ski (9)
Let's say S23 = S32 /= 0. according to (8) and (9) S31 = S13 = 0, what can't be because of (5), (6), and (9)
A three-port device can't be matched at all ports and lossless at the same time.
the wilkinson dividider is matched, but not lossless, because his scattering matrix breaks formula (4)
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Rod Post subject: Unread postPosted: Fri May 27, 2005 11:42 pm
As a power splitter, there is no power dissipated in resistor .
As a combiner, half the power is dissipated in the resistor.
If you combiner 2 signals in phase and amplitude, no power is dissipated in the resistor.
Posted 11/12/2012
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