How to rate RF power handling of a part

1. Oct 5, 2011

sszhao

I made a DIY RF trasformer, and I want to know how much RF power can it handle, I want it to work from 500K hz to 3Ghz, have DC resistance 0.1ohm, L primary=5nH. There would be no DC current through this part.

How would I know how much RF power my part handles? Do I send a voltage through the primary, or connect the part to a RF amplifier with a power meter and measure how much the part heat up?

what is the proper way of measuring it?

2. Oct 5, 2011

Staff: Mentor

Welcome to the PF.

Before addressing the power handling capabilities, what is the impedance of your primary inductance at 500kHz? That would seem to be an issue, no?

3. Oct 5, 2011

yungman

First, read the rating on the core you use, everything else is secondary. I doubt you can find a core for 3GHz. Not to mention you want 0.1Ω impedance. At this freq, transformer is really not the way, all core material literally stop working unless there are new materials since a few years ago.

You need to give more info, 0.1ohm is very very low impedance, you might have to resort to other method depend on whether you want to step up voltage or what. If you need wide band, your choice will be very limited, if you work with one freq at a time, transmission line impedance transformation is the way to go.

4. Oct 5, 2011

sszhao

Sorry I'm not being clear.
The parimary winding have DC resistance of 0.1 ohm, it is measured using precision ohm meter, it is a known value.
I didn't measure impedance of the primary. since L is 10nH at 100Khz, Z would be jwL = 0.01 ohm? at 1ghz Z=62 ohm How do I know how much RF power this part can handle?

5. Oct 6, 2011

yungman

I don't think you can use Z=jwL for that kind of frequency. You have to take into consideration of the parasitic. If you can tell us more about what you are trying to do, maybe there are other ways. Transformer with winding and core is not going to work very well for 500MHz and over. The length of the wire of the transformer is going to be comparable to the wavelength and everything don't behave in the traditional V=IZ anymore.

6. Oct 6, 2011

skeptic2

Ask yourself what are the characteristics of the transformer that could be destroyed by too much power and what are the effects of too much power that can destroy them. I can think of two. Heat may cause the insulation to melt or deteriorate, degrade the core if you're using one or even melt the wires. Another is that excessive voltage may cause arcing between turns or even between the primary and secondary.

You need to quantify how much heat or voltage it would take to cause damage. Generally you can look up the specifications of the materials you're using or if you can't find them, a little destructive testing may be required.