Analysis of Two-Beam Ka Band Folded Waveguide Traveling-Wave Tube

The limiting factors in gain and bandwidth of folded-waveguide traveling-wave tube with single-beam are analyzed. A method of improving gain growth rate and broadening bandwidth by introducing two electron beams is proposed. Numerical results reveal that saturated output power of high-frequency interaction system with two electron beams is increased to 2.8 times than single-beam structure under the same as the operating voltage and current of single beam, that is, interaction efficiency is increased to 1.4 times ,and saturated length is reduced by 5 geometrical periods. Bandwidth is broadened due to two electron beams with different speeds, which can meet the synchronization conditions in a wider frequency range. A broad band amplifier is designed. Simulations show that the amplifier produces a saturated radiation power of 256 W at the frequency 27 GHz. The 3-dB gain bandwidth is 16.5% covering the range 25-29.5 GHz. In addition, the instability in gain caused by reflection is analyzed.