A power amplifier uses a modular architecture in which each of the one or more modules spatially combines the power from multiple amplified channels. The individual modules are configured to operate in the EHF band and above at low loss. This entails reconfiguring the input and output splitters, the end-launched transitions between the amplifier chips and the input and output splitters and the packaging of the DC power and control board. The input splitter uses a split-block technology. The output splitter maps each amplified channel into a two-dimensional aperture.