Double Vane Slow Wave Structure Research Articles

Experimental Investigation of a Shape-Optimized Staggered Double-Vane Slow-Wave Structure for Terahertz Traveling-Wave Tubes

Enormous concerns focus on the high-power and wide bandwidth traveling-wave tube (TWT) for its outstanding performance. In this article, a shape-optimized staggered double-vane slow-wave structure (SWS) for terahertz (THz) sheet beam TWT is proposed. The shape-optimized staggered double-vane SWS takes the advantages of higher interaction impedance, lower transmission loss, and lower phase velocity than conventional staggered double-vane SWSs. The shape-optimized staggered double-vane SWS with 85 periods is designed, fabricated, and cold tested. The measured transmission loss of the shape-optimized staggered double-vane SWS is less than 0.79 dB/cm in the frequency range of 0.211–0.26 THz, which is in good agreement with the simulation results. Furthermore, the beam–wave interaction analysis of a sheet beam TWT with this SWS is given. The output power is predicted to be >100 W with 3-dB bandwidth of >50 GHz. The results show that the shape-optimized staggered double-vane SWS is a very promising scheme to construct a high-power and wideband THz TWT for future applications such as communication and imaging.

Double-mode and double-beam staggered double-vane traveling-wave tube with high-power and broadband at terahertz band

In this paper, a 220 GHz broadband and high-power staggered double-vane traveling-wave tube has been designed and verified. Firstly, a planar double-beam staggered double-vane slow-wave structure is proposed. By using the double-mode operation scheme, the transmission performance and bandwidth have been almost increased with twice as the single mode. Second, to satisfy the high output power requirement and improve the stability of the traveling-wave tube, a double pencil-beam electron optical system has been designed, the 20–21 kV driven voltage and the 2 × 80 mA current are set as the design target. By using the mask portion and the control electrode in the double beam gun, the two pencil beams can be focused with a compression ratio of 7 along their respective centers with narrow distances of about 0.18 mm with good stability. The uniform magnetic focusing system has also been optimized. The stable transmission distance of planar double electron beams could reach 45 mm with the focusing magnetic field of 0.6 T, which was long enough to cover the whole high-frequency system (HFS). Then, to verify the availability of the electron optical system and the performance of the slow-wave structure, particle-in-cell (PIC) simulation has also been carried out with the whole HFS. Results demonstrate that the beam-wave interaction system can get a nearly 310 W peak output power at 220 GHz with a 20.6 kV optimized beam voltage and beam current of 2 × 80 mA, the gain is of 38 dB with the 3-dB bandwidth over 35 dB about 70 GHz. Finally, the high precision microstructures fabrication has been carried out to verify the performance of the HFS, the results show that the bandwidth and the transmission properties are in good agreement with simulation result. Thus, the proposed scheme in this paper is expected to develop the high-power and ultra-wideband terahertz band radiation source with potential applications in the future.

Design of RF Planar Slow Wave Interaction Structure for THz Devices

Micro fabricated planar slow wave structure (SWS) in a travelling wave tube (TWT) has shown a superior performance when compared with the circular helix structure for RF power amplification. The circular helix structure applications are limited to the maximum operating frequency of 70 GHz. In the proposed paper, a rectangular planar slow wave structure operating at terahertz (THz) is designed. Fabrication of the beam interaction system is complex especially operating at higher frequencies as the device dimensions decrease. Use of planar interaction system simplifies the miniaturised fabrication process. The present paper focused on the design of staggered double vane slow wave structure (SWS) and simulated the corresponding dispersion diagram and S-parameters of the model by using CST Studio Suite software. The results for designed RF planar slow wave structure are then analysed.

Multiple-beam and double-mode staggered double vane travelling wave tube with ultra-wide band

This paper presents design, fabrication and cold test of an ultra-wide band travelling wave tube (TWT) with planar alignment multiple pencil beams. The fundamental double-mode of staggered double vane slow wave structure (SDV-SWS) rather than the only one mode are put forward and adopted to match with the same electron beam to increase the bandwidth greatly. Simultaneous planar alignment multiple pencil beam tunnels are designed to improve interaction impedance and then to enhance output power, gain, efficiency, growth rate. The transmission performance of a two-stage 51-period SDV-TWT in G-band with structure attenuator between two sections shows that it indeed has an ultra-wideband performance from 81 to 110 GHz. By using computer numerical control machining, the SDV-SWS was manufactured and a detailed cold test was conducted. Good agreement is found at the wide band, where S21 is above − 5 dB and S11 is below − 10 dB. 3D PIC simulations with double-mode multiple-beam SDV-TWT within total length of 70 mm show that it can get a nearly 2120 W peak output power, a 42.5 dB corresponding gain and a 10.7% electron efficiency at 94 GHz with a 22.1 kV beam voltage and a 3 × 0.15A beam current. The 3 dB bandwidth of our double-mode SDV-TWT can achieve about 29 GHz.

A staggered double-vane slow-wave structure with double sheet electron beams for 340 GHz traveling wave tube

ABSTRACTAn improved slow-wave structure (SWS) for a 340 GHz traveling wave tube (TWT) is proposed. The dispersion curve and transmission characteristics of SWS have been calculated and analyzed. The transmission and reflection of the RF structure are S21 > −7 dB and S11 < −16 dB, respectively. Two sheet electron beams with identical physical parameters are used to control the operation of a TWT. In addition, the output power, gain, and bandwidth of the TWT were studied using three-dimensional particle-in-cell (PIC) simulation method. A uniform constant magnetic field with the magnetic field density of 0.2 T is used to focus the sheet electron beam. The results of the PIC simulations show that the TWT achieves the maximum output power of 12 W and the 3 dB bandwidth of 25 GHz (328–353 GHz) at the input power of 10 mW. At 340 GHz, the output power of 12 W and the gain of 30.8 dB are obtained.

Design of W‐band sheet beam travelling wave tubes based on staggered double vane slow wave structure

In this study, a complete and viable plan about a W-band sheet beam travelling wave tube based on a staggered double vane slow wave structure is drawn up. The dispersion characteristics, transposition characteristics of high-frequency system, sheet electron beam gun, vacuum window, periodically cusped magnetic focusing system and beam–wave interaction are analysed by CST Microwave Studio, CST Particle Studio and HFSS. An attenuator is used in this device to suppress oscillation. A phase velocity taper is used to increase output power. The operation voltage is 20.6 kV and the current is 80 mA. With a 10 W input power, the output power is 1100 W versus the gain is 20.41 dB at 95 GHz. The peak amplitude approaches 1200 W versus the gain approaches 20.79 dB at 99 GHz.

Study on Ka-Band Sheet Beam Traveling Wave Tube Focused by Closed PCM

This paper reports a Ka-band sheet beam traveling wave tube (TWT) focused by a 0.2 T closed periodic cusped magnet (PCM) system. The TWT with one section of staggered double-vane slow-wave structure (SWS) is driven by a 0.8-A sheet beam with rectangular cross-sectional area of 3.2 mm × 0.6 mm. This sheet beam TWT can produce 100 W output power, and the 3 dB band is 33–38.5 GHz. In order to improve the output power, an optimized sheet beam TWT with two sections of SWSs focused by a novel closed PCM system is proposed. The new closed PCM system is with annular magnetic blocks and can be fabricated and adjusted easily. The simulation shows that the optimized sheet beam TWT can produce 2000 W output power and the 3 dB band ranging from 33 to 40 GHz.

0.22 THz two-stage cascaded staggered double-vane traveling-wave tube

A two-stage cascaded staggered double-vane slow-wave structure (SWS) has been proposed to develop a compact, practical terahertz radiation source. This paper reports the model of the two-stage cascaded staggered double-vane SWS and its transmission characteristics. The particle-in-cell simulation results revealed that this circuit can be applied to produce over 15 W of peak power in the range from 0.205 to 0.23 THz powered by two 30 mA, 18.7 kV, well-focused electron beams, with a maximum gain of 27.6 dB at 0.22 THz. Moreover, the current density of $$98.4\hbox { A}/\hbox {cm}^{2}$$98.4A/cm2 and circuit length of 27.45 mm produce a significant advantage for beam generating and focusing.

$W$ -Band Multiple Beam Staggered Double-Vane Traveling Wave Tube With Broad Band and High Output Power

A design study for a high-power, high-efficiency, high-growth-rate wideband traveling wave tube (TWT) in $W$ -band using a staggered double-vane slow-wave structure (SWS) combined with three plan alignment pencil beams is described in this paper. The electromagnetic characteristic simulation shows that it has a wide bandwidth, high interaction impedance (about two to three times higher than those of the same structures with the sheet beam scheme), and a more simply designed input/output coupler. 3-D particle-in-cell simulations predict that the TWT can produce over 2000 W of output power from 91 to 95 GHz just using a 52-period two section SWS with a total length of 70.3 mm when the voltage and current of three pencil beams are set to 22 kV and $140\times 3$ mA, respectively. The maximum peak output power is about 2256 W with a corresponding gain of 43.5 dB and an electronic efficiency of 12.2% at 94 GHz. The 3-dB bandwidth can be achieved at about 15 GHz with an instantaneous relative bandwidth of about 15.9%. Finally, the comparisons of sheet beam, multiple beam, and single pencil beam staggered double-vane TWT are presented and analyzed.

220GHz三级串联交错双栅慢波结构

220GHz三级串联交错双栅慢波结构

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications.

W-Band 1-kW Staggered Double-Vane Traveling-Wave Tube

A design study for a W-band traveling-wave tube (TWT) using a staggered double-vane slow-wave structure combined with a sheet electron beam shows that an output power of over 1 kW should be possible. Numerical eigenmode calculations indicated that the structure has a strong longitudinal component of electric field for interaction with the electron beam. A novel input and output coupler was proposed that can produce good input and output matches. Finally, a TWT model with moderate dimensions was established. The particle-in-cell simulation results revealed that the tube can be expected to produce over 1 kW of peak power in the range from 90 to 95 GHz, assuming an RF input signal with a peak power of 0.15 W and a beam power of 10.3 kW. The corresponding conversion efficiency values vary from 9.87% to 12.15%, and the maximum gain is 39.2 dB at 93 GHz.

Design and simulation of 140 GHz high power staggered double vane traveling-wave tube

Staggered double vane slow wave structure (SWS) and sheet electron beam are employed to investigate a 140 GHz high power traveling wave tube. Numerical calculation of eigenmode shows that the SWS has a good characteristic of dispersion and interaction impedance. The transition structure, input/output coupler and concentrated attenuator are especially proposed for the circuit to ensure that the tube will work well. Particle-in-cell simulation results demonstrate that the traveling wave tube can provide over 300 W of peak power in a frequency range of 132-152 GHz with a maximum of 546 W and a corresponding gain of 37.37 dB at 138 GHz assuming a beam power to be 5.115 kW and input power to be 0.1 W. The output power of the tube can exceed 440 W in a frequency range of 128-152 GHz with a corresponding interaction efficiency of over 8.6% when the input powers range from 0.027 W to 0.46 W. Such a traveling wave tube has a great significance and a potential application in high power short millimeter wave field.