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Terahertz backward wave oscillators based on double corrugated waveguides are enabling devices for modern satellite communication systems. This research focuses on the design of a 0.34 THz double corrugated waveguide-based interaction structure using a sheet beam. This choice allows the use of shorter pillars along with a narrow gap between pillar rows. Shorter pillars are easier to manufacture and a narrow gap is required for better interaction impedance. Circular beams restrict the use of larger pillars and narrow gap between pillars. The performance of this interaction structure is compared with a folded waveguide. Under the same operating conditions involving a 20 kV beam voltage and a 30 mA beam current, the double corrugated waveguide interaction structure exhibits impressive performance in simulations, featuring an interaction impedance of 0.52 Ω at 0.34 THz, an output power of 3.2 W, and a bandwidth extending to approximately 20 GHz. In contrast, the folded waveguide, as per simulation results, registers values of 0.43 Ω , 2.6 W, and a 12 GHz bandwidth, respectively. The proposed double corrugated waveguide-based interaction structure is fabricated using modern CNC machining. Experimental validation reinforces the effectiveness of this design, with measurements indicating reflection below −20 dB and transmission exceeding −2 dB. [ABSTRACT FROM AUTHOR]

A $Q$ -band traveling-wave tube (TWT) with profiled helix pitches and profiled inner diameters of slow wave structure (SWS) is proposed. The transmission characteristics of the $Q$ -band TWT are simulated by the Computer Simulation Technology (CST). In the operating frequency band (36.5–41.5 GHz), the simulated voltage standing wave ratio (VSWR) is less than 1.5. In addition, the beam–wave interaction is simulated to predict the performance of the $Q$ -band TWT when the beam voltage and beam current are 8.5 kV and 60 mA, respectively, and the axial focusing magnetic field is 0.4 T. In the operating frequency band, the self-oscillation is well suppressed, and the device efficiency of the $Q$ -band TWT exceeds 63.5%, and the saturated output power and gain exceed 83 W and 45 dB, respectively, especially the device efficiency can reach the maximum of 69.5% at 37 GHz. When it is backed off 6 dB from the saturation, the device efficiency exceeds 40.5%, up to 42.7% at 39 GHz. Preliminary experiments have confirmed the design. These results show that the proposed $Q$ -band TWT has important applications to the next generation wireless communication system with high efficiency. [ABSTRACT FROM AUTHOR]

A novel electron-optical system (EOS) for ${G}$ -band traveling-wave tubes (TWT) is investigated by simulation and verified by experiment. The EOS includes a sheet beam electron gun, a tunable periodic cusped magnetic focusing (TPCMF), and a collector. An elliptical focus electrode (FE) featuring a simple geometry and easy fabrication is utilized to compress the pencil beam into the sheet beam with a cross section of 0.4 mm $\times0.1$ mm. The electron gun with a cylindrical cathode of 0.8 mm diameter generates the sheet beam with voltage of 22 kV and current of 115 mA. Based on the sheet beam electron gun, the TPCMF with easy assembly and compact size is then proposed. The experimental results show that the beam transmission is 92.1% within a beam tunnel (its length 21.2 mm and cross section 0.8 mm $\times0.15$ mm). The EOS is suitable for ${G}$ -band TWT. [ABSTRACT FROM AUTHOR]

A novel sine groove waveguide slow wave structure (SGW-SWS), originated from the sine waveguide (SW), is proposed for a wideband terahertz (THz) traveling wave tube (TWT). SGW-SWS not only has high interaction impedance in a relatively wide frequency band, but also has a wide beam tunnel. In addition, it can be fabricated using the Nano-Computer Numerical Control (CNC) milling techniques. The high-frequency simulation results show that, under the same dispersion, the passband of SGW-SWS is 23 GHz wider than that of SW-SWS, and the average interaction impedance of SGW-SWS is higher than that of SW-SWS in the whole passband. And the transverse dimension of beam tunnel is independent of the dispersion characteristics of SGW-SWS, so the beam current can be further increased by enlarging the size of beam tunnel. Moreover, the particle-in-cell (PIC) simulation results reveal that the saturated power and electronic efficiency of SGW-TWT in the frequency range of 201–260 GHz are more than 84.9 W and 2.72%, respectively, when the operating voltage is 20.8 kV and the beam current is 150 mA. [ABSTRACT FROM AUTHOR]

In this article, a novel dielectric-supported staggered dual-meander-line (DS-SDML) planar slow-wave structure (SWS) is proposed for a traveling wave tube (TWT) working at ${E}$ -band. The proposed staggered arrangement of meander-lines (MLs) leads to a stronger beam–wave interaction and achieves higher output power as compared to the symmetric arrangement. The input–output couplers have been designed by using staggered stepped double ridge waveguide, to connect the standard ${E}$ -band rectangular waveguide and the DS-SDML SWS. An attenuator and pitch tapering have been applied to the proposed SWS to suppress the unwanted frequencies and to improve the output power. Particle-in-cell (PIC) simulation results show that for an 11.8-kV, 200-mA sheet-beam, the output power can reach 283 W at 75 GHz, with a maximum gain and electronic efficiency of 34.5 dB and 11.9%, respectively. [ABSTRACT FROM AUTHOR]

A novel helical groove rectangular waveguide slow wave structure (HGRW-SWS) which evolves from the double staggered grating waveguide (DSGW) SWS is put forward to develop the high-gain and high electron efficiency terahertz (THz) traveling wave tube (TWT). The major advantages of the HGRW SWS are the higher interaction impedance, lower ohmic loss, and lower phase velocity especially in higher frequency band compared with the DSGW SWS. The gain and electron efficiency of TWT using HGRW-SWS have been significantly improved, respectively, compared with the TWT using DSGW-SWS. [ABSTRACT FROM AUTHOR]

High-power vacuum electron devices (VEDs) are attractive, because of their broad applications, such as advance radars, electromagnetic warfare, and plasma reactors. In this paper, a Ka band mega-watt sheet electron beam traveling wave tube (TWT) is reported. A two-staged rectangular waveguide grating slow wave structure (SWS) driven by a sheet electron beam (20 mm × 1 mm, 164.8 kV, 850 A, 20 ns) is used in this TWT. In order to suppress the self-excited oscillation, a rectangular BeO attenuator is inserted between the two-staged SWSs. The experimental results show that the TWT can produce more than 2 MW output power from 34.2 to 35.5 GHz. And the maximum output power is 4.24 MW at 35 GHz, corresponding to the gain of 25.9 dB. In the future, the TWT will be used to perform research on biomedical effects and imaging. [ABSTRACT FROM AUTHOR]

A 140-GHz folded-waveguide traveling wave tube (FWG-TWT) with a relatively larger circular electron beam tunnel was designed and developed. Using simulation software, the high frequency characteristics, the transfer characteristics, and the beam-wave interaction of the TWT were studied in detail. The simulation predicted up to 98 W output power and about 43 dB gain of FWG-TWT at the center frequency. The input and output couplers compatible with the FWG-SWS and the periodic permanent magnet focusing structure were designed. The FWG-TWT thus designed was fabricated and tested. The experimental result shows the output power exceeding 1.6 W and the gain exceeding 25 dB at 140 GHz when the input power is 5 mW. The reasons for the departure of the experimental from the simulated results have been explained. [ABSTRACT FROM PUBLISHER]

In this paper, a wideband 220-GHz sheet-beam traveling-wave tube (TWT) based on staggered double vane slow-wave structure (SWS) is investigated. A novel method of loading the attenuator into the SWS for suppressing backward wave oscillation is proposed. In addition, a novel focusing electrode of the sheet beam gun is carried out in this paper, which is a whole structure but divided into two parts artificially, one is used to compress the electron beam in $X$ -direction and the other is used to compress the electron beam in $Y$ -direction. In addition, a novel anode is redesigned to reduce the defocusing effect caused by the equipotential surfaces. A nonuniform periodically cusped magnet is used for focusing the sheet electron beam, which is predicted to exhibit 100% beam transmission efficiency in a 75-mm length drift tube. The high-frequency characteristics of the SWS and the beam-wave interaction are also studied. The results reveal that the designed TWT is expected to generate over 78.125-W average power at 214 GHz, and the 3-dB bandwidth is 31.5 GHz, ranging from 203 to 234.5 GHz. [ABSTRACT FROM PUBLISHER]

It is attractive to use sheet beam vacuum devices to generate high frequency, high-power microwave radiation. In this paper, we present the numerical and experimental studies of a high-power Ka-band sheet electron beam backward wave oscillator (BWO), in which the double-grating rectangular waveguide is used as the slow wave structure (SWS) for its thermal and mechanical robustness. The fundamental mode of this kind of SWS is an antisymmetric mode which has an antisymmetric longitudinal field distribution and will nonsynchronously interact with the electron beam on two sides of the electron channel along the vertical direction. We put forward a method to overcome this trouble in this paper. To drive this BWO, a high-power sheet beam is used with a cross section of 30 mm $\times\,$ 1 mm. A thin graphite cathode is used for its superiority in producing a high current, high-quality electron beam. For an experimental electron beam of 141 kV and 1668 A, the output power of over 46.8 MW at 31.68 GHz is obtained, which corresponds to a beam–wave interaction efficiency of 19.9%. Compared with the conventional hollow beam BWO and the single-grating rectangular waveguide sheet beam BWO, the double-grating sheet beam BWOs efficiency is higher, which indicates that the double-grating sheet beam device is promising for producing millimeter wave radiation with high power and high efficiency. [ABSTRACT FROM PUBLISHER]

An attenuator supporting meander-line (ASML) slow wave structure (SWS) is proposed for a Ka-band traveling wave tube (TWT) and studied by simulations and experiments. The ASML SWS simplifies the fabrication and assembly process of traditional planar metal meander-lines (MLs) structures, by employing an attenuator to support the ML on the bottom of the enclosure rather than welding them together on the sides. To reduce the surface roughness of the molybdenum ML caused by laser cutting, the ML is coated by a thin copper film by magnetron sputtering. The measured S11 of the ML is below −20 dB and S21 varies around −8 dB to −12 dB without the attenuator, while below −40 dB with the attenuator. Particle-in-cell (PIC) simulation results show that with a 4.4-kV, 200-mA sheet electron beam, a maximum output power of 126 W is obtained at 38 GHz, corresponding to a gain of 24.1 dB and an electronic efficiency of 14.3%, respectively. [ABSTRACT FROM AUTHOR]