Design of a KA-band helix traveling wave tube for LMDS (local multipoint distribution service)

Summary form only given. A Ka-band helix traveling-wave-tube (TWT) amplifier is designed. A sheath helix theory and HFSS code are validated by benchmarking the Northrop-Grumman's C-band TWT amplifier. Electron gun was designed by the Pierce gun theory, EGUN code, POISSON code and MAGIC 2D code. Cathode diameter is 1.6 mm to load beam current density 2 A/cm 2 . 49 magnets of PPM were used to focus electron beam. EGUN and MAGIC 2D simulation shows 8% of beam ripple. Coupler is designed by Chebyshev transformer theory and HFSS code, fabricated and tested. A Ka-band helix circuit is designed by the use of the sheath helix theory and HFSS code. The Pierce linear gain theory predicts a linear gain growth rate and a helix circuit length. The MAGIC 2D code and 1D LMSUITE code are utilized to predict a large signal, non-linear performance of the amplifier. Simulations show that saturated amplified output power is 40 W at 26-30 GHz, corresponding to electronic efficiency of 8% and gain of 47 dB where beam voltage, current and axial magnetic field are 9.4 kV, 80 mA and 2200 gauss, respectively