Lesson 4 - PCB Design

Also Microwave circuits are affected by moisture content in the dielectric substrate and we used low moisture materials which cost a little more than the standard materials. Rogers 4003 was a good solution for some boards  FR4 has a tendency to absorb moisture as do some of the PTFE based materials.

Note the copious use of vias along the RF path and the clearance between the signal and ground planes. Also the absence of soldermask on the signal path, soldermask can be lossy to microwave RF signals. Also note the presence of a metal backing plate under the board, serves 2 purposes, one is rigid assembly construction and the other is the heat dissipation for the hotter components.