The two primary types of TWTAs are Helix and Coupled Cavity amplifiers.
Helix TWT amplifiers are low power amps that work by sending radio waves down a helix-shaped wire. A helix amplifier is ideal in applications that call for low noise, high sensitivity, and broadband operation, i.e. test equipment and radar receivers.
Coupled-Cavity TWT amps are higher power, designed to amplify signals for high-power transmitters. Instead of a helix wire, these TWTs send the sign through cavity resonators. Their higher output power is paired with a narrower bandwidth.
TWT amplifiers can also be divided into broadband and narrowband.
Broadband TWT power amplifiers generate an output power of up to 2.5 kW.
Narrowband TWT amplifiers utilize coupled cavity traveling wave tubes, which deliver power levels up to 15 kW.