Tube-vs.-Transistor Debate Continues

Many military and commercial applications require generous amounts of RF power, including satellite communications (satcom) uplinks and radar systems. Typically, satcom system designers automatically reach for a travelling-wave-tube-amplifier (TWTA) catalog for power levels in excess of 100 W at Ku-band (14 GHz), and there are many fine suppliers of this venerable technology (the latest TWTA from Comtech Xicom Technology will be reviewed in the upcoming February installment of Defense Electronics).

Solid-state technology was at one time automatically dismissed as inadequate for large amounts of output power at higher microwave frequencies. But transistor-amplifier designers are a feisty bunch, driven to displace TWTAs with their solid-state circuits. They may not be there just yet, but as the lead news item below illustrates, they're getting closer. And in the process, they bring along those simpler power supplies for transistors, often with improved operating efficiency compared to tubes. Inevitably, it appears that transistors will catch tubes in terms of power at a given frequency, but that challenge is firmly in the hands of the process and device developers, rather than the SSPA designers. In the meantime, let's enjoy the competition.