[SOLVED] Measure the precise coupling coefficient of two wired inductors at low frequency

[Josephchiang]

Dear all,

I want to use vector network analyzer(VNA) to measure the coupling coefficient of two wired inductors which operated at low frequecny(1MHz).

I have consult the user manual of VNA and the operation frequency at 1MHz is permissible.

But I don't quie sure that the value is correct in such the low frequency operation.

Does anyone have any suggestion for me?

I really appreciated your help.

 

[BigBoss]

Since If they say it's working, it will work..
Specifications are measured and proven,otherwise they don't mention..

 

[mtwieg]

At low frequencies, the "industrial leakage" method where you measure winding inductance while the other winding is open and short is usually sufficient. However, it can be more complicated if your mutual impedance has a significant real portion to it (which is often the case if you're using a lossy core material).

 

[FvM]

A complete measurement of the four two-port parameters includes the necessary information to calculate the coupling factor. Accuracy depends on the S-parameter result range, instrument specification and correct calibration.

But you didn't tell how you want to calculate coupling from the set of S-parameters.

 

[Josephchiang]

In my case,the coupling coefficient is very low due to the two inductors placed 10cm apart.

I want to connect one terminal of each coil to ground and the other one to VNA port.

And transform the measured S parameter into z matrix.

Mutual inductance=imag(Z(2,1))/(2*pi*freq)

Am I right?

 

[mtwieg]

Z21 will be equal to mutual impedance, but you'll have to derive Z parameters from measured S parameters (with good calibration). Ideally Z21 will be the impedance of the mutual inductance alone, but as I said above any losses in the core/medium will skew that result.

 

[Josephchiang]

Thanks for all good advice.