Traveling wave tube amplifier
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A traveling wave tube amplifier (abbreviated TWTA and often pronounced "TWEET-uh") is an electronic device used to produce high-power radio frequency signals. The bandwidth of a broadband TWTA can be as high as one octave, although tuned (narrowband) versions exist, and operating frequencies range from 300 MHz to 50 GHz.
A TWTA consists of a traveling wave tube (TWT) coupled with its protection circuits (as in klystron)) and regulated power supply (EPC, electronic power conditioner), which may be supplied and integrated by a different manufacturer. The main difference between most power supplies and those for vacuum tubes is that efficient vacuum tubes have depressed collectors to recycle kinetic energy of the electrons and therefore the secondary winding of the power supply needs up to 6 taps of which the helix voltage needs precise regulation. The subsequent addition of a linearizer (as for inductive output tube ) can, by complementary compensation, improve the gain compression and other characteristics of the TWTA; this combination is called a linearized TWTA (LTWTA, "EL-tweet-uh").
Broadband TWTAs generally use a helix TWT, and achieve less than 2.5 kW output power. TWTAs using a coupled cavity TWT can achieve 15 kW output power, but at the expense of bandwidth.
[edit] Uses
A TWTA whose output drives an antenna is a specific type of transmitter. TWTA transmitters are commonly used in satellite transponders. They are also used extensively in radar, particularly in airborne fire-control radar systems, and in electronic warfare and self-protection systems. In these types of applications, a control grid is typically introduced between the TWT's electron gun and slow-wave structure to allow pulsed operation. The circuit that drives the control grid is usually referred to as a grid modulator.
Another major use of TWTAs is for the EMC testing industry for immunity testing of electronic devices.
