Insertion loss of Balun device

[rf1008]

Hello all,

I have a little question now on balun loss. This is a general balun,**broken link removed**

The insertion loss in the spec is about 0.32dB@1000MHz. I think the total or actual insertion loss from the unbalunced port to one of the twobalanced port is 0.32+3dB=3.32dB,because one balun is special power divider with 180 degrees phase invertion between two balanced ports,and as we know the ideal power divider has 3dB loss from input to one of the two ports.

Why does the supplier not specify the total and autual loss? thanks.

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A ha! Maybe i got the answer. It's the concept issue.

The 3dB is the distribution loss which is the theoretic value of the 2-way power divider, the insertion loss is only the loss due to material, VSWR and others.

 

[FvM]

Yes, insertion loss is the ratio of input to output (forward) power. Although a balun can described as unbalanced 3-port and e.g. measured with a VNA in this configuration, I won't see it as a power divider, because it doesn't provide any isolation or reflection suppresion for the single ended halves of the balanced port. To split or combine individual unbalanced signals, you would use e.g. a Wilkinson divider.

 

[BigBoss]

Ideal Balun does not have 3dB insertion loss.The power dividers have it, don't confuse..
If Balun has 0.32dB insertion loss, Unbalanced-to-Balanced (one of them) insertion loss means 0.32dB.

 

[rf1008]

Ideal Balun does not have 3dB insertion loss.The power dividers have it, don't confuse..
If Balun has 0.32dB insertion loss, Unbalanced-to-Balanced (one of them) insertion loss means 0.32dB.

I 'm really confused. you mean balun's insertion loss doesn't include the 3dB loss which is the constribution loss in power divider devece.For example, when 0.32dBm power is applied to the unbalanced port of my balun(MA/Com ETC1-1-13, it has 0.32dB insertion loss),0dBm is abtained at every balanced port and then the total output power at both balanced ports are 3dBm. BUT 3dBm is larger than 0.32dBm which means output power is larger than input power????

Please kindly advise. thank you.

 

[FvM]

You are creating the confudion by describing the balun as a power divider. But the specification is that of a two port with an unbalnced and a balanced side.

 

[rf1008]

You are creating the confudion by describing the balun as a power divider. But the specification is that of a two port with an unbalnced and a balanced side.

Of course balun is generally a two-port device and the insertion loss is defined by the power tranmission loss from unbalanced port to balanced port, the loss is lower than 1dB. but if you think it as three-port device, the insertion S21=S31=3dB. Also of course nobody use balun as power divider for the poor isolation and the phase difference.

 

[FvM]

For the said 1:1 balun, |S21| and |S31| would be considerably below -3dB, because the matched impedance of the two unbalanced ports is 25 rather than 50 Ohm, so there's a mismatching loss im addition.