The amplifier housing was designed to be compact. The microwave and bias circuits were split into two separate cavities on opposite sides of the housing. This way, the microwave side could be kept small to eliminate in-band cavity resonances. DC bias for the transistors was brought up to the microwave cavity from the DC cavity using small feed-thru pins. The DC cavity contains filtering capacitors and provides space to add overvoltage protection diodes.
The microwave connectors are SMA. The size of the housing was determined by the DC bias circuit board and the Hirose bias connector. Although a smaller connector would be desirable, this particular connector seems to be well designed and built, and has given us no problems. The housing could be made significantly smaller if necessary by using a smaller bias connector and redesigning the DC bias circuit board.
The housing was made of brass since brass is an easy material to machine. It was finished in wire-bondable gold, for obvious reasons.
For a printable version of the AutoCAD drawings, here are PDF files of the block and the lid.