Simulation Study Of 140 GHz Extended Interaction Amplifier

The extended interaction device,combines the ideas of the klystron and the traveling wave tube.It has a compact structure,small size and high peak power.But its individual cavities are still narrow-band resonant cavities,the bandwidth advantage is not obvious.In this thesis,the bandwidth expansion of the 140 GHz extended interaction amplifier is studied.Besides,an electron gun and a permanent magnetic focusing system which generates a unidirectional uniform magnetic field is designed.The details of this thesis are as follows.Firstly,an attempt to expand the bandwidth of the 140 GHz extended interaction amplifier is made.Considering the advantages of the?-mode,the unequal width slot extended interaction cavity is used.After an analysis to the dispersion characteristic,synchronization conditions and the influence of the structural parameters on the high-frequency characteristics,a four-cavity,five-gap,unequal-width extended interaction amplifier structure is designed.By simulating this high frequency structure and analyzing the effect of the frequency difference between the output and input cavities on the output power,the structure obtains a maximum peak output power of 537 W,a 3 d B bandwidth of 500 MHz,a relative bandwidth of 0.35%.At an operating voltage of 22 k V and a current of 0.3 A,the electronic efficiency is 8.13%.With an input power of 31.25 m W,the gain is 42.35 d B.The input and output cavities of the conventional extended interaction amplifier are replaced by the folded waveguide slow wave structure,the limitation to the transmission bandwidth of the extended interaction amplifier is solved.The cluster bandwidth is extended by increasing the number of intermediate cavities.The broadband EIA with two intermediate cavities and three intermediate cavities with unequal width slot extended interaction cavities are designed.The simulation test of the broadband extended interaction amplifier with two intermediate cavities has obtained a peak power of 420 W,a 3 d B bandwidth of 800 MHz,a relative bandwidth of 0.57%,and an electronic efficiency of 6.5%under the conditions of an operating voltage of 21.5 k V and a current of 0.3 A.under the condition of input power of 5 m W,the gain is 49.2 d B.At the same operating voltage,current and input power,simulations of a broadband extended interaction amplifier with three intermediate cavities gave a peak power of 351 W,a 3 d B bandwidth of 1.3 GHz,a relative bandwidth of 0.92%,an electronic efficiency of 5.4%at peak power and a gain of 48.4 d B.Based on the EIA high frequency structure,two electron guns are designed with an spherical emitting surface of 1.09 mm~2,an operating current of 0.3 A and operating voltages of 22 k V and 21.5 k V,respectively.A unidirectional permanent magnetic focusing system is designed for this electron gun to realize the focus of the electron beam.Under a longitudinal magnetic field of 0.5 T,the minimum area of the electron beam is compressed to 0.02 mm~2,with a compression ratio of 54.