looking for good books for balance impedance matching !!

[mckinson]

I want to make match for balance . But I don't know how to
start ? How to measure the balance impedance by network analyzer ? What is difference from single ended ?

Best regards !!

 

[pewang]

look into agilent websit and search for "balance measurement".
Balun is the popular circuit type when doing balance matching.You can either buy one or make by hand.
Mini-circuit and Aneren and Murata all provide this device in SMT package.

 

[peter7488]

Re: looking for good books for balance impedance matchin

in Agilent web-page. you can download the appcad which contain a program for balun applicaton. Have a try.

 

[Mazz]

Re: looking for good books for balance impedance matchin

The procedure that I follow to match the differential impedance is the following one:
I have a board with the differential pins of the DUT connected to microstrips and SMA connectors. I calibrate the VNA to the input pins of the DUT (this is fundamental).
Then I measure the s2p parameters of the DUT with port1 connected to differential+ and port 2 connected to differential-.
Then I apply the formula:
GD=((2*S(1,1)-S(2,1))*(1-S(2,2)-S(1,2))+(1-S(1,1)-S(2,1))*(1+S(2,2)-2*S(1,2)))/((2-S(2,1))*(1-S(2,2)-S(1,2))+(1-S(1,1)-S(2,1))*(1+S(2,2)))
obtaining a set of complex numbers that represents the differential s-parameters.

Then I design the matching network.
The starting point is one half of GD and use a simple tool (smith chart based) in single end mode. Then I make the differential equivalent network and verify the results on a high level simulator (ADS).
Bye
Mazz

 

[rfic]

Who have the usage book of appcad?

 

[chihhao]

Re: looking for good books for balance impedance matchin

Hi Mazz,
What's the next procedure when you get GD ?
Could you please explain it again ?
one half GD ?? Thanks.

 

[spikeyang]

1)According to Mazz,
I found the formula too,but still dont know how it comes.
You get GD(I think it's the reflection coefficient of the balance port);
GD = (Z-Z0)/(Z+Z0)
then
Z = Z0*(1+GD)/(1-GD);

Z0 is 100 Ohm,I think;but
from MAXIM's web it's 50 Ohm,who is wrong?

2)in the hybrid S parameter definition:

Sdd11=(s11-S21-S12+s22)/2;
I dont think Sdd11 here have any difference with GD above,but the formula are totally different. Why,then?

3)The safest way is to use the appcad 3.0.2,it has a
tool in [everything S parameter] to convert single-ended two-port s parameter into differential s parameter. Very convient.

Spikeyang

 

[chihhao]

Re: looking for good books for balance impedance matchin

Am I right for this matching procedure.
(1) Got GD
(2) Calculate differential impedance according to GD
(3) Put the differential impedance to be the load termination in differential structure simulation.

Please advise.Thanks.

 

[Mazz]

ajhsu
I think you have now read the pdf I've put in .
Your procedure is correct.
Take care about this: you need to measure accurately the S2P of differential impedance, with MEASUREMENT PLANE AT DUT. Usually deembedding techniques are applied, or TRL calibration is performed.
As there is a post processing of S2P -> GD, phase errors can give you wrong results.
I hope it can help.
Mazz