Impedance matching using a ferrite tuner (voltage control)

[ohadmos]

Hi
I wanted to ask you a question regarding a changing load impedance and reflection coefficient.

I have a system in which the load at the end of the transmission line changes radically all the time in matter of less than 0.1 second.
In order to deliver it a maximum power I have to match it to the source and network impedance (lets say 50ohm).
I can detect at any time the incident power and returned power in order to get the reflection coefficient, and standind wave pattern.

right now we are using a 3-stub system which moves with controlled engines, and its not good enough.
I have read a bit on the use of Ferrite Tuners in antenna systems, I was thinking of matching network of a ferrite rod before the load which is voltage controlled.
We are talking about a system which operates in 28V, 150W..

Can someone here tell me if it will work, how can it work, and where do I find these tuners?

Thanks, and sorry for the long text.

 

[ohadmos]

Re: Impedance matching using a ferrite tuner (voltage contro

If no1 knows about this tunning method, or if it is not the thread for this kind of matters, please redirect me to right spot.

Thanks again.

 

[biff44]

Re: Impedance matching using a ferrite tuner (voltage contro

I guess it all depends on how radically the load impedance changes over time, and the magnitude of the reflection coefficient.

Does it start as a |ρ|=1 and end up as a |ρ|=0 load, or is it much more constant?

Frequency 100 MHz?

 

[ohadmos]

Re: Impedance matching using a ferrite tuner (voltage contro

The load changes are very radical, yes - reflection coeffiecient can go from 1 to 0 quit fast.
frequency is about 2.2GHz.

 

[biff44]

Re: Impedance matching using a ferrite tuner (voltage contro

Well, I have not thought it thru, but it seems to me that if you could vectorially cancel the reflected wave from the load, then you would be matching the load to the source.

I would observe the forward vs reflected wave from the load with a dual directional coupler.

I would generate the drive signal by sending maybe 80% of the power to the load, and the other 20% of the power through a vector phase modulator. I would then recombine the power somewhere at the load (forward or reflected wave? I would have to think on that a little.) I would then dynamically adjust the phase and amplitude of the 20% power so that they overall reflected power from the load is minimized.