Why put Beryllium Oxide parts in a Directional Coupler?
hboy007, Fri Sept 07 2018, 10:11PMI couldn't help myself and bought one of those sub-1GHz directional couplers. Any clue what the stud might connect to and why one would need to make components out of BeO in there?
The device measures 30 x 30 x 90 mm³ without connectors and weighs 630 g ... I guess it's mostly one solid hunk of brass.
Re: Why put Beryllium Oxide parts in a Directional Coupler?
Hazmatt_(The Underdog), Sat Sept 08 2018, 03:28AM
BeO is a really good substrate for microwave, it has wonderful dielectric as well as thermal properties that make it an ideal substrate for microwave traces and transmission lines.
The stud is a detector diode output. Sometimes you see couplers with just an RF sampling port, and sometimes you get the oddity with the diode integrated into the coupler.
It looks like you have two sampling ports on the other side as well, but this looks to be a single directional coupler, and not a dual directional coupler, probably used for the ALC in a power amp as the feedback sampler.
Hazmatt_(The Underdog), Sat Sept 08 2018, 03:28AM
BeO is a really good substrate for microwave, it has wonderful dielectric as well as thermal properties that make it an ideal substrate for microwave traces and transmission lines.
The stud is a detector diode output. Sometimes you see couplers with just an RF sampling port, and sometimes you get the oddity with the diode integrated into the coupler.
It looks like you have two sampling ports on the other side as well, but this looks to be a single directional coupler, and not a dual directional coupler, probably used for the ALC in a power amp as the feedback sampler.
Re: Why put Beryllium Oxide parts in a Directional Coupler?
Conundrum, Sun Sept 23 2018, 01:04PM
Yes, its far superior to other insulators because its RF stable even when heated.
Interesting news: seems that some IGBTs and bricks use BeO so be careful please! And notably base station parts though this is less of a problem because you aren't going to be grinding *those* with a Dremel. At least I hope not!
Conundrum, Sun Sept 23 2018, 01:04PM
Yes, its far superior to other insulators because its RF stable even when heated.
Interesting news: seems that some IGBTs and bricks use BeO so be careful please! And notably base station parts though this is less of a problem because you aren't going to be grinding *those* with a Dremel. At least I hope not!
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