Abstract
To realize the miniaturization of E-band traveling-wave tubes (TWTs), the size analysis and optimization design were carried out based on an improved cosine-vane folded waveguide (CV-FWG) slow-wave structure (SWS) that operates in a low voltage. In addition, a novel miniaturized T-shaped coupler was proposed to achieve a good voltage standing wave rate (VSWR) in a broad bandwidth. The coupler length was reduced by as much as 77% relative to an original design. With higher coupling impedance, the radius and length of the shortened SWS were optimized as 1.3 mm and 50 mm, respectively. Using microwave tube simulator suit (MTSS) and CST particle studio (PS), 3D beam–wave simulations at 9400 V, 20 mA predicted a gain of 20 dB and a saturated output power of 9 W. The simulation results for CV-FWG TWTs were compared with conventional FWG TWTs from 81 GHz to 86 GHz, showing significant performance advantages with excellent flatness for high-rate wireless communication in the future. The CV-FWG SWS circuit will be fabricated by 3D printing, and this work is underway.
Highlights
It was proved that the beam–wave interaction of is stronger compared compared to the folded waveguide (FWG) and facilitates the reduction of the length of slow-wave structure (SWS)
We introduced a miniaturized CV-FWG SWS that was designed to operate in the voltage
To couple the CV-FWG, a compact T-shaped coupler was proposed with a good matching property
Summary
The Federal Communications Commission (FCC) opened up the E-band (71–76 GHz and 81–86 GHz) for millimeter wave frequency microwave communication [1]. Among vacuum electron devices (VEDs), the traveling-wave tube (TWT) is a preferable choice for millimeter waves, which have high power and wide bandwidth [6,7,8]. BVERI developed an E-band TWT that can produce more than 75 W continuous wave saturated output power over the range of 81–86 GHz with a voltage of 16.3 kV and a current of 105 mA [10]. Utilizing the same design rules and fabrication technology, an E-band TWT with a saturated output power of 8 W will be built [13]. The normalized phase velocity in thein the frequency range below 55 GHz increases with the increase of d, while the trend reverses above 55 GHz. The cutoff frequency is almost constant.
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