We report a MEMS (micro-electro-mechanical systems) compatible distributed loss type sever design for the 220 GHz double vane half period staggered traveling-wave tube amplifier (TWTA) . The cold test simulations for a full TWT model including input/output couplers and broadband tapered vane transitions incorporating the sever, predicted a return loss (S11) of < -10 dB in the pass band (205 GHz-275 GHz) while an insertion loss/isolation (S21) of < ~-27 dB. The return loss of the TWT circuit did not degrade by the inclusion of the sever (< -10 dB) while still maintaining a good isolation (S21) for the RF signal. Particle-In-Cell (PIC) simulation analysis for the full 220 GHz TWT circuit (a) without sever and (b) with sever was conducted. With the inclusion of the sever, the TWTA showed generally a stabilized output response for all cases. The maximum power from the long sever case was ~25 W for Pin ~50 mW and the gain was ~27 dB. The reverse power was decreased to ~30 mW. For the short sever, the PIC results were even better with a maximum output power of ~62 W and a gain of ~30.92 dB with a reduced reverse power of ~5 mW for an input power of 50 mW at 220 GHz. The FFT spectrum of the RF signal at the output port also showed a spectrally pure waveform at 220 GHz.
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