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A traveling-wave tube (TWT) is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs to a category of "linear beam" tubes, such as the klystron, in which the radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube.〔 Although there are various types of TWT, two major categories are:〔 *Helix TWT - in which the radio waves interact with the electron beam while traveling down a wire helix which surrounds the beam. These have wide bandwidth, but output power is limited to a few hundred watts. *Coupled cavity TWT - in which the radio wave interacts with the beam in a series of cavity resonators through which the beam passes. These function as narrowband power amplifiers. A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencies, a wide bandwidth. The bandwidth of the helix TWT can be as high as two octaves, while the cavity versions have bandwidths of 10–20%.〔〔 Operating frequencies range from 300 MHz to 50 GHz.〔〔 The power gain of the tube is on the order of 40 to 70 decibels,〔 and output power ranges from a few watts to megawatts.〔〔 TWTs account for over 50% of the sales volume of all microwave vacuum tubes.〔 They are widely used as the power amplifiers and oscillators in radar systems, communication satellite and spacecraft transmitters, and electronic warfare systems.〔 A TWT has sometimes been referred to as a "traveling-wave amplifier tube" (TWAT),〔(Military Acronyms, Initialisms, and Abbreviations ) on (Federation of American Scientists ) web site〕 although this term was never widely adopted. "TWT" has been pronounced by engineers as "twit", and "TWTA" as "tweeta". ==Description== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Traveling-wave tube」の詳細全文を読む スポンサード リンク
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