Design and Experimental Study of an E-Band CW Space TWT

Abstract

This article presents a design and experimental study of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$</tex-math> </inline-formula> -band continuous wave (CW) space traveling wave tube (TWT) at 71–76 GHz. To ensure a high beam transmission, a double anode electron gun and periodic permanent magnetic (PPM) focusing system were designed, while linear tapered transition waveguides with diamond windows were used to form an energy coupling system as to increase output power. A four-stage depressed collector was also designed to improve overall efficiency. A prototype <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$</tex-math> </inline-formula> -band CW space TWT was then fabricated and tested at a relatively lowered beam voltage of 14.8 kV and beam current of 73 mA. The testing results show that this tube is capable of providing over 87-W output power, 41-dB gain, and overall efficiency of over 31%, within a bandwidth of 5 GHz at 71–76 GHz, with a maximum saturated output power of 110 W, a corresponding gain of 49 dB, and an overall efficiency of 37%. Given the relatively lowered operating voltage and current, it is believed the overall performance of this <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$</tex-math> </inline-formula> -band TWT exhibits a substantial improvement as compared to those of the reported similar tubes.