Search Results (23)

This paper presents a W-band low-voltage traveling-wave tube (TWT) incorporating a spoof surface plasmon polariton (SSPP) slow-wave structure (SWS) and a dual-sheet beam. The SSPP-based SWS adopts a periodic double-F-groove configuration, which provides strong field localization, increases the interaction impedance, and reduces the phase velocity, thereby enabling a low synchronization voltage. Owing to its symmetric open geometry, the SWS naturally forms a dual-sheet beam tunnel, which enhances the effective beam current without increasing the aperture size. Eigenmode calculations indicate that, within the 92–97 GHz band, the normalized phase velocity is between 0.198 and 0.208, and the interaction impedance exceeds 2.65 Ω. Moreover, an energy-coupling structure was developed to ensure efficient signal transmission. Three-dimensional particle-in-cell (PIC) simulations predict a peak output power of 366.1 W and an electronic efficiency of 6.15% at 95.5 GHz for a 2 × 250 mA dual-sheet beam at 11.9 kV, with stable amplification and without self-oscillation observed. The proposed low-voltage, high-efficiency W-band TWT offers a manufacturable and easily integrable solution for next-generation millimeter-wave systems, supporting high-capacity wireless backhaul, airborne communication, radar imaging, and sensing platforms where compactness and reduced power-supply demands are critical. Full article

As solid-state devices continue to advance, vacuum electron devices maintain critical importance due to their superior high-frequency power handling, long-term reliability, and operational efficiency. Among these, traveling-wave tubes (TWTs) excel in high-power microwave (HPM) applications, offering exceptional bandwidth and gain. However, developing THz-range TWT slow-wave structures (SWSs) presents significant design challenges. This work systematically outlines the SWS design methodology while addressing key obstacles and their solutions. As a demonstration, a staggered double vane (SDV) SWS operating at 1 THz (980–1080 GHz) achieves 650 mW output power, 23.35 dB gain, 0.14% electronic efficiency, and compact 21 mm length. Comparative analysis with deformed quasi-sine waveguide (D-QSWG) SWS confirms the SDV design’s superior performance for THz applications. Full article

This paper presents the design and investigation of a two-stage flat-roofed sine waveguide (SWG) traveling-wave tube (TWT) incorporating a novel coupling structure. Initially, the slow-wave structure (SWS) of a 220 GHz flat-roofed SWG was optimized, and the output performance of the corresponding TWT was thoroughly analyzed. Subsequently, a specialized coupling structure was designed and fabricated, with the experimental results demonstrating an excellent agreement with the simulation predictions. The coupling structure exhibits low reflection and is easily manufacturable, making it highly suitable for energy coupling in two-stage TWTs. Finally, a two-stage TWT, integrating both the optimized flat-roofed SWG structure and the coupling structure, was developed and characterized. Under operating conditions of a 20.8 kV beam voltage, 150 mA current, and 150 mW input power, the proposed TWT achieved remarkable performance metrics: a maximum output power of 160 W within the frequency range 210–230 GHz and a 3 dB bandwidth exceeding 20 GHz. This research provides a valuable reference solution for the realization of high-power, broadband terahertz radiation sources, contributing significantly to the advancement of terahertz vacuum electronic devices. Full article

During the early growth stages of fish larvae, there are significant challenges to their viability, so improving their visual environment is essential to promoting their growth and survival. Following the successful knockout of thyroid hormone receptor beta 2 (thrb2) using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology, there was an increase in the expression of UV opsin (short-wave-sensitive 1, sws1), while the expression of other cone opsins was significantly decreased. Further analysis of the retinal structure demonstrated that the thrb2 knockout resulted in an increased lens thickness and a decreased thickness of the ganglion cell layer (GCL), outer plexiform layer (OPL), and outer nuclear layer (ONL) in the retina. The slowing down of swimming speed under light conditions in thrb2^−/− may be related to the decreased expression of phototransduction-related genes such as G protein-coupled receptor kinase 7a (grk7a), G protein-coupled receptor kinase 7b (grk7b), and phosphodiesterase 6c (pde6c). Notably, thrb2^−/− larvae exhibited a significant increase in the amount and proportion of first feeding, and their growth rate significantly exceeded that of wild-type controls during the week after feeding. This observation suggests that although the development of the retina may be somewhat affected, thrb2^−/− larvae show positive changes in feeding behaviour and growth rate, which may be related to their enhanced ability to adapt to their environment. These results provide novel insights into the function of the thrb2 gene in the visual system and behaviour and may have implications in areas such as fish farming and genetic improvement. Full article

Staggered double-grating slow-wave structures (SDG-SWSs), which are easy to fabricate and have broadband characteristics, play a core role in research on high-power terahertz (THz) traveling-wave tubes (TWTs). However, their relatively low interaction impedance restricts further improvements in the output power of SDG-TWTs. A modified staggered double corrugated waveguide (MSDCW) SWS that evolved from a staggered double corrugated waveguide (SDCW) SWS is proposed in this study for the first time. The MSDCW-SWS has both the advantages of a wide bandwidth and a high interaction impedance. The width of the beam tunnel also has little effect on the lower cutoff frequency. High-frequency calculations reveal that the passband of the MSDCW-SWS is 10 GHz wider than that of the SDG-SWS, and the interaction impedance is about 1.34 ohm higher than that of the SDG-SWS and 1.07 ohm higher than that of the SDCW-SWS at 220 GHz when the dispersion is the same. The results of the interaction simulation show that the MSDCW-TWT has a maximum gain of ~22.11 dB with a maximum output power of ~117 W and a maximum electron efficiency of ~2.64% at 220 GHz with an electron beam of 24.6 kV and 180 mA. The MSDCW should therefore be considered as a promising SWS for high-power and wideband THz traveling-wave amplification. Full article

For the purpose of improving performance and reducing the fabrication difficulty of terahertz traveling wave tubes (TWTs), this paper proposes a novel single-section high-gain slow wave structure (SWS), which is named the symmetrical quasi-synchronous step-transition (SQSST) folded waveguide (FW). The SQSST-FW SWS has an artificially designed quasi-synchronous region (QSR) to suppress self-oscillations for sustaining a high gain in an untruncated circuit. Simultaneously, a symmetrical design can improve the efficiency performance to some extent. A prototype of the SQSST-FW SWS for 650 GHz TWTs is designed based on small-signal analysis and numerical simulation. The simulation results indicate that the maximum saturation gain of the designed 650 GHz SQSST-FW TWT is 39.1 dB in a 34.3 mm slow wave circuit, occurring at the 645 GHz point when a 25.4 kV 15 mA electron beam and a 0.43 mW sinusoidal input signal are applied. In addition, a maximum output power exceeding 4 W is observed at the 648 GHz point using the same beam with an increased input power of around 2.8 mW. Full article

A staggered vane-shaped slot-line slow-wave structure (SV-SL SWS) for application in W-band traveling wave tubes (TWTs) is proposed in this article. In contrast to the conventional slot-line SWSs with dielectric substrates, the proposed SWS consists only of a thin metal sheet inscribed with periodic grooves and two half-metal enclosures, which means it can be easily manufactured and assembled and has the potential for mass production. This SWS not only solves the problem of the dielectric loading effect but also improves the heat dissipation capability of such structures. Meanwhile, the SWS design presented here covers a −15 dB S₁₁ frequency range from 87.5 to 95 GHz. The 3-D simulation for a TWT based on the suggested SWS is also investigated. Under dual-electron injection conditions with a total voltage of 17.2 kV and a total current of 0.3 A, the maximum output power at 90 GHz is 200 W, with a 3 dB bandwidth up to 4 GHz. With a good potential for fabrication using microfabrication techniques, this structure can be a good candidate for millimeter-wave TWT applications. Full article

A miniaturized traveling wave tube (TWT) was studied by proposing a novel metamaterial (MTM) slow wave structure (SWS). The dispersion results show that n = −1 space harmonic of the fundamental mode exhibits the “forward” wave properties, which is the foundation of the MTM-inspired TWT. Meanwhile, the interaction impedance for mode 2 of the novel MTM SWS can be sharply decreased by introducing four blend edges to weaken the corresponding longitudinal electric field. Also, two coaxial couplers are presented to input/output the signals. The transmission results show that the reflection is as low as −15 dB from 2.90 GHz to 3 GHz, which ensures the amplified signal can be effectively outputted. The MTM-inspired TWT exhibits miniaturized superiority for its compact high frequency structure including the MTM SWS and the coaxial couplers. Especially, for the high-frequency structure, the transverse and longitudinal sizes are ~λ/5 and ~3λ, respectively (λ is the free-space wavelength at the operating frequencies). The simulation of the beam wave interaction shows that the proposed MTM-inspired TWT yields output powers of kW levels from 2.90 GHz to 3 GHz, with a gain of 23.5–25.8 dB and electronic efficiency of 14–22% when the beam current is 0.5 A and the beam voltage is 13 kV. The results indicate that the gain per wavelength is as high as 8.5 dB in the operating bands. The simulation results confirm that it is possible to weaken the backward wave oscillation from the higher mode in the miniaturized MTM-inspired TWT. Full article

In this paper, a novel staggered double-segmented grating slow-wave structure (SDSG-SWS) is developed for wide-band high-power submillimeter wave traveling-wave tubes (TWTs). The SDSG-SWS can be considered as a combination of the sine waveguide (SW) SWS and the staggered double-grating (SDG) SWS; that is, it is obtained by introducing the rectangular geometric ridges of the SDG-SWS into the SW-SWS. Thus, the SDSG-SWS has the advantages of the wide operating band, high interaction impedance, low ohmic loss, low reflection, and ease of fabrication. The analysis for high-frequency characteristics shows that, compared with the SW-SWS, the SDSG-SWS has higher interaction impedance when their dispersions are at the same level, while the ohmic loss for the two SWSs remains basically unchanged. Furthermore, the calculation results of beam–wave interaction show that the output power is above 16.4 W for the TWT using the SDSG-SWS in the range of 316 GHz–405 GHz with a maximum power of 32.8 W occurring at 340 GHz, whose corresponding maximum electron efficiency is 2.84%, when the operating voltage is 19.2 kV and the current is 60 mA. Full article

In this article, the first 237 GHz traveling wave tube (TWT) is presented as a high-power amplifier for the terahertz (THz) cloud radar. As is common with previous G-band traveling wave tubes developed at Beijing Vacuum Electronics Research Institute, the 237 GHz traveling wave tube employs a 20 kV, 50 mA pencil electron beam focused using periodic permanent magnets (PPMs) to achieve compactness. A folded waveguide (FWG) slow-wave structure (SWS) with modified circular bends is optimized to provide high impedance and eliminate sideband oscillations. Limited by insufficient drive power, this device is not saturated. The measured maximum output power and gain are 8.9 W and 35.7 dB, and the 3 dB gain bandwidth achieves 4 GHz. Full article

A novel slow-wave waveguide structure is proposed, the guided-wave properties of which can be controlled by the rotation of nonuniform metasurface elements loaded on the surface of the substrate-integrated waveguide. The proposed nonuniform metasurface unit cell can exhibit anisotropic guided-wave parameters of interest, i.e., equivalent permittivity and permeability along the transverse direction that are different from those along the longitudinal direction. Such characteristics suggest different propagation behaviors along different directions. Therefore, the equivalent permittivity and permeability change as the proposed nonuniform cross-unit cell rotates through various angles, which would modify the guided-wave properties as well. In this way, the cutoff frequency and phase constant of the proposed anisotropic SW-SIW can be controlled flexibly by rotating the patterned metasurface unit cells over different angles. Several SW-SIW experimental prototypes with different rotation angles are implemented, and their respective measured results are in good agreement with their simulated counterparts. Thereby, the proposed method can provide more flexibility for designing and controlling an anisotropic SW-SIW. Full article

A traveling-wave tube (TWT) with a sheet electron beam and staggered double-grating slow-wave structure (SWS) is a promising high-power, wideband terahertz amplifier. In such tubes, electron-optical systems (EOSs) with a converging sheet beam are mostly used, which allow a reduction of the cathode load, increase the lifetime, and enable operation in a continuous-wave (CW) mode. This paper presents the results of a 3D particle-in-cell (PIC) simulation of the 0.22 THz TWT driven with a converged sheet beam, which is compressed to less than 100 μm thickness in the EOS with a magnetically shielded cathode. The beam with high compression has a significant transversal velocity spread and essentially non-uniform current density distribution over the cross-section. These factors significantly affect the beam–wave interaction. We compare the performance of the TWT driven by the compressed sheet beam and by an idealized initially rectilinear beam without any velocity spread. Full article

A multiple dielectric-supported ridge-loaded rhombus-shaped meander-line (MDSRL-RSML) slow-wave structure (SWS) is proposed for a V-band wideband traveling wave tube (TWT). The high-frequency and transmission characteristics of the SWS are investigated. The proposed structure can realize stable output via attenuator and special phase-velocity jumping. Particle-in-cell (PIC) results indicate that, for a 7 kV, 0.1 A sheet-beam, the average output power can reach 60 W at 60 GHz and a 3 dB bandwidth of 9 GHz, with the corresponding gain and electron efficiency of 30.8 dB and 17.2%, respectively. Compared with the dielectric-supported rhombus-shape meander-line (DS-RSML) SWS, the proposed structure has a wider bandwidth, higher gain, more stable structure, and better heat dissipation ability, which make it a good candidate source in millimeter-wave communications. Full article

To increase the output power of microstrip line traveling-wave tubes, a staggered rings microstrip line (SRML) slow-wave structure (SWS) based on a U-shaped mender line (U-shaped ML) SWS and a ring-shaped microstrip line (RML) SWS has been proposed in this paper. Compared with U-shaped ML SWS and RML SWS, SRML SWS has a wider transverse width, which means SRML SWS has a larger area for beam–wave interaction. The simulation results show that SRML SWS has a wider bandwidth than U-shaped ML SWS and a lower phase velocity than RML SWS. Input/output couplers, which consist of microstrip probes and transition sections, have been designed to transmit signals from a rectangular waveguide to the SWS; the simulation results present that the designed input/output structure has good transmission characteristics. Particle-in-cell (PIC) simulation results indicate that the SRML TWT has a maximum output of 322 W at 32.5 GHz under a beam voltage of 9.7 kV and a beam current of 380 mA, and the corresponding electronic efficiency is around 8.74%. The output power is over 100 W in the frequency range of 27 GHz to 38 GHz. Full article

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. Full article