There are numerous techniques for designing microwave power amplifiers. These may be broadly split between tube and solid state technologies. For high power requirements (> 100 Watts), typically these are satisfied with tube based designs. Tube amplifiers, such as Traveling Wave Tube Amplifiers (TWTAs), require a high voltage power supply, typically require warm-up time, and have significant aging related issues. For solid state amplifiers to achieve similar performance often requires switching between
narrow-band amplifiers, with deleterious effects to the overall linearity and gain/power flatness. The switches themselves embody performance compromises. Mechanical switches, while quite linear and relatively low loss, have switching speed limitations, and are subject to failure after repeated switching cycles. Solid state switches may overcome the speed issue, but are not nearly so linear or low loss. Both the signal fidelity and loss issues limit the usefulness of solid state switches for high power microwave amplifiers. Furthermore, switching between narrowband amplifiers requires external stimulus with the software control complication that entails.