# Measurement of mutual inductance of two wireless power coils

1. ## Measurement of mutual inductance of two wireless power coils

Hi All, I saw in some papers that the coupling factor k of two wireless power coils (L1 and L2) equals to M/SQRT(L1*L2), while M is the mutual inductance of these two coils. I am wondering if there is any method we can use to measure this M when the two coils are placed at a certain distance (say, 1cm in the perfect alignment condition). I do not have the vector network analyzer, is it possible for me to do this measurement in the lab? Both L1 and L2 are known since they are commercial available products.
Thank you!

•

2. ## Re: Measurement of mutual inductance of two wireless power coils

All standard coupled inductance measurement methods can be used. Induced voltage, inductance variation with open/short of coupled coil, resonator detuning with open/short, inductance variation with series versus anti-series circuit.

•

3. ## Re: Measurement of mutual inductance of two wireless power coils

Originally Posted by FvM
All standard coupled inductance measurement methods can be used. Induced voltage, inductance variation with open/short of coupled coil, resonator detuning with open/short, inductance variation with series versus anti-series circuit.
Hi FvM, would you give me some more details? I have a circuit like this:

where Vtx and Vrx are two sinusoidal signals. The transfer function between Vtx and Vrx are like this:

The C_PRI is resonant with L_PRI at f1, and C_SEC is resonant with L_SEC at f2. The coupling between L_PRI and L_SEC caused the flat band between f1 and f2.
My questions are:
(1) which could be the most suitable "coupled inductance measurement method" for me to use in this circuit?
(2) I asked you about the bandwdith question in a different thread. We look at the first picture, if I have this open loop system, with some signal processing circuit to translate the sinusoidal signal Vrx to a DC voltage, how can I measure the bandwidth of this open loop system? Should I still measure Vout/Vin?
Thank you!

--[[ ]]--