Ferrite materials are commonly used for transformers for kHz and low MHz frequencies. Some vendors of RF products do however provide small transformers using small binocular cores (it looks like ferrite - could also be iron powder..) which have low insertion loss all the way up to 2 GHz or more. Does anyone know which kind of core mix is typically/can be used in such transformers?
Does anyone know which kind of core mix is typically/can be used in such transformers?
Ferrite core vendors supply separate material data sheets for their cores. Just look at those to understand the high frequency characteristics. The material data sheets are unspecific to core size (and shape) and reasons will be apparent when you look at a few. It keeps things easier to analyse. The actual core data sheets will be specific to core shapes and sizes and, they will quote the relevant materials used i.e. you get a cross reference to the material in the core data sheet. This links everything together nicely IMHO.
Ok, I think I got your point now. The transformer vendor actually provides a material declaration.. I found it now. I thought you were talking about the core vendors. Thanks, this could be an answer to the question.
Done! Any further help on specific cores/materials, just leave a comment.
In the GHz range: transformers, filters, diplexers, combiners use air as a coupling media.
The external metal case plays a key role in the design.
Many filters are layied up on a RF PCB and then enclosed in a metal case.
I've never seen commercially available magnetic cores working in the GHz range.
Magnetic dipoles of ordinary materials like soft ferrite are too slow to change orientation in space in the nano second range.
Maybe in some lab they are working on an advanced material working in the GHz range.