Hello Everyone,

I want to design a RF to DC conversion Rectifier.

For that, I need to couple little the input RF signal.

But i dont know how start with RF power coupling. Your help and suggestions would be of great help !!

Looking forward for the replies.

 

1kW is a lot and 2% is 20W. what did you do so far? what is your RF pickup? is it an antenna?

 

The RF power is entering into microstrip line conductor. From this line I have to take fraction of the RF power to rectify.

So far I have been looking how I can take fraction of this power from main (Input) microstrip line. I think simple lumped element like capacitor can be used to sense & take fraction of this input power and then it can be given to rectifier circuit. But I am bit confused and don't know from where I should start (calculation parts , circuit topology etc).

 

Hello,

Coupling with a capacitor is a bad idea.
It is like connecting it directly to the main line.
Using a coupling coil would be an better idea.

Bertus

PS take great care NOT to touch anything.
RF signals can cause serious burns.

 

Hello,

One thing is strange to my ears.
Why is a microstrip line inductor used at 80 MHz?
I would expect that at much higher frequencies. (in the upper hundreds to thousands of mega herz).

Can you post a schematic and a photo of the circuit?

Bertus

 

Hello,

The only circulators I know of are working in the GHz range.
1kW at the gigaherz range is very dangerous.
It will cause burns UNDER the skin.

Do you have more info on the frequency range?

Bertus

 

Hello,

The frequency range will be 70-85 MHz with mainly at 80 MHz operation. So I have to sense this input RF signal and take little amount of it for DC conversion.

Could you please suggest / send few documents or data which would be helpful to clear my basic concepts ? At this point I am not able start anything.

 

Hello,

Without YOUR schematics I can not give the advice.
I now do not know how to couple the signal.

Bertus

 

Hello,

I will not communicate by mail.
Here are the instruction for attaching images:
Attachments and Images

Bertus

 

Hello,

As stated before, circulators are use from VHF and higher.
At the lower frequencies they will become to large to handle.
http://en.wikipedia.org/wiki/Circulator

If there is an open line available, run a line on a couple of mm next to it.
Ground the new line at one side, put a diode on the other side and measure the voltage.
This way you will have a kind of RF transformer.

Bertus

 

Hello,

Thank you very much for the reply and valuable suggestions.

Could you please suggest me some relevant document/ Design Guide for this technique ? As I am beginner, it would be better to clear my basic concepts & for further component calculations.

Regards,

 

Hello,

Have a look how directional couplers work:
http://www.rfcafe.com/references/electrical/directional-coupler.htm

They also have calculation software:
http://www.rfcafe.com/business/software/rf-cafe-calculator-workbook/rf-cafe-calculator-workbook.htm

Bertus

 

Hello,

I want to design following rectifier topology (please find the attachment) for MHz frequency range. Can anybody suggest me with relevant formulas for calculating component values ?

So far I have obtained Load current & Capacitor C2 calculation equations for normal Half wave rectifier.

Vdc= Vsmax- Vr/2
I= Vdc/RL
C2= I * (dT /Vripple)

Are they same for this circuit ? Also, what modifications should be made when the load is not pure R (has some imaginary part)?

How can I calculate C1 value and micro strip equivalent lumped elements for MHz frequency ?

Looking forward for the replies.

Regards