component selection for RF circuits

[per_lube]

component dimension selection for RF circuits

Hi,

Got two questions,

1. Is there a general rule for selecting dimensions of components for RF circuits?
I've heard lumped component dimensions should be less than lambda/10 at the operating frequency... is that true?

2. Can we have holes in a metal package of a microwave circuit which will not allow to leak RF signals?
dimensions of the holes in terms of lamda? < lambda/10, <lambda/20 etc?

cheers,
per_lube

 

[Ow@i$]

i think size of component depends on the power they can handle 1/4Watt resistor must be smaller than 1Watt one. with same freq. but high Power requirement you will have to use a bigger one no matter how it effects lamda/10 or else!!
as a general rule use smallest package component that at the same time can handle required power, it is good for space minichrization point of view.

 

[mtwieg]

Power dissipation is one concern, but with regards to component sizing I'm usually concerned about how size effects signal losses and circuit accuracy. For example if I'm at 500MHz are 1008 packages still okay, or should I move down to 0805 or smaller? On one hand my components will probably behave more like they should with their marked values, but on the other hand they will have lower Q and more loss. So how do you know when to make the switch?