Cavity for Launch Circuit

Hi,

I saw in some amplifier module design that the designer create an air cavity underneath the RF launch circuit. I think this is to improve the S11/S22 of the overall performance.

Does anybody has any reading material related to this type of cavity design? I was wondering if there is such formula that can be used to calculate the size of this cavity.

Thanks in advance for the help.

Poktuyu

Hi,

I was wondering if anybody could help with the earlier posting. I heard some engineers were saying that the cavity is created to prevent the waveguide mode (TE, TM) in the circuit.. I am trying to find any reading material related to this to understand more on this topic.

Please help. Thanks.

cavity is generate as an heat sink to carry away heat generated in transistor