毫米波折叠波导行波管输入输出过渡波导设计

折叠波导以其宽频带、加工方便而成为一类重要的毫米波与太赫兹波段行波管慢波线。针对折叠波导慢波系统与标准波导的匹配过渡连接,通过等效电路分析与电磁计算软件模拟,设计出了直渐变波导、双曲圆弧渐变波导、切比雪夫阶梯渐变波导3种输入输出过渡波导结构,分析了各种过渡波导的优缺点及结构尺寸对性能的影响。计算表明,经过合理优化的设计,3种过渡结构均可以使反射系数在28~40 GHz波段小于0.05。     

Design of Coupling Structure for MMW Folded Waveguide TWTs

A significant advantage of the folded wave traveling wave tube (TWT) is simple coupling structure. In millimeter wave band, owing to higher frequency, linear double taper can be used as impedance transformer. The design method and calculation results for the folded waveguide TWTs in K-band are given.     

Review of the Novel Slow-Wave Structures for High-Power Traveling-Wave Tube

All-metal slow-wave structures are being paid great attention because of their advantages, such as good heat dissipation, high power capacity, wide passband, good wholeness of structure and large size etc. The emphases in this paper concentrate on the present state of study of four types of structures: helical groove, ring-plane, folded waveguide and periodically loaded waveguide, including theoretical analyses and practical applications. The problems and directions for future studies of these types of slow-wave circuits are also discussed. It is pointed out that all-metal slow-wave structures are suitable for applications in millimeter wave vacuum devices, like TWT, BWO, Gyro-TWT, and relativistic devices.     

Performance and Application of Slow Wave Circuits for Power TWT in Millimeter Wave

In millimeter wave range, high-power traveling wave tube (TWT) is a key device with broadband and high-power amplification. Basis of comparing traditional and new type slow wave circuits for high-power TWT in MMW, analysis and computation of propagating and RF performance for folded wave circuit are carried out. Theoretic calculation and experimental test show that folded wave circuit is an ideal slow wave structure for broadband and high-power TWT in MMW. There is extreme wide application for the circuit in high-power TWT. This development possesses important consult value to designer for MMW power amplifiers.     

Analysis of Performances for Broadband Millimeter Wave Folded Waveguide TWTs

On the basis of computation of dispersion and coupling impedance for folded waveguide circuit (FWC), main performances: interact coefficient, saturated gain and output power are analyzed. Computation shows that if FWC is used in MMW amplifier, high power and wide band can be easy reached.     

A RF window for broadband millimeter wave tubes

The equivalent circuit and design method for a RF window in millimeter wave band are presented. Computation and experiment show that matching band of the RF window is wider. It can be used as output window for broadband millimeter wave tubes.     

Computation of matching characteristics between rectangular coupled cavity and waveguide for millimeter wave TWT''s

A rectangular coupled cavity slow wave structure is a new type of circuit for high power millimeter wave TWTs in recent years. Matching characteristics of trasition between rectangular coupled cavity and waveguide are calculated by equivalent circuit method. The results obtained by this method are compared with experiments and it is shown that useful accuracy can be obtained.     

曲折圆形槽波导慢波系统的高频特性

 对曲折圆形槽波导新型慢波系统的高频特性进行了研究，通过理论分析和数值计算，得到了它的色散曲线和耦合阻抗表达式，并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明：当周期变小时色散减弱，耦合阻抗增加；而增大直波导长度时色散变弱，但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低，可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点，在毫米波及亚毫米波段的行波管中具有较好的发展前景。     

Optimum Design of a Ridge Waveguide Transformer for MMW Tube's

A ridge waveguide transformer is commonly used in output structure for millimeter wave tubes(such as magnetron and traveling wave tube). It is not satisfied, if a traditional designing method is used in broadband case. The optimum design of a ridge waveguide transformer is given in this paper. The computation results show that the reflect character of the transformer can be met the demands for broad band match.     

Study of Propagating Characteristics for Folded Waveguide TWT in Millimeter Wave

Folded waveguide circuit (FWC) is an ideal slow wave structure for broadband power traveling wave tube (TWT) in millimeter wave. But owing to changes of propagating character by reflecting of waveguide bend and electron beam hole, stopband can be formed. On the basis of computation of the stopband, effects of the dimension of FWC on stopband width are analyzed. It is available for design in FWC TWT.     

Engineering Design Method of Energy Coupler and Impedance Transformer for Millimeter Wave Tubes

The engineering design method of heliz-waveguide and rectangular coupled cavitiy-waveguide energy coupler employed in millimeter wave tubes is described. Experiments show that, the former has broadband matching character )VSWR is less than 2 at 26 - 40GHz). And the later has small reflection (VSWR is less than 1.5 at 34-37.5 GHz). Optimum design method of multi-section and linear taper waveguide impedance transformer is also given in this paper. These impedance transformers can operate at wide frequency range in microwave and millimeter wave band. The design method and examples of couplers and impedance transformers can be referred for tube designers.     

Analysis of space harmonic selectivity of period-varying folded waveguide

A period-varying folded waveguide is formed by varying the period of a folded waveguide. It has the advantages of the space harmonic selectivity and the wide bandwidth. However, the regularities of the variety of these period-varying folded waveguides are unavailable from the published papers. In order to solve this problem, the principle of the space harmonic selectivity of a period-varying folded waveguide is analysed, and the conditions to select the space harmonic for this slow wave system are obtained. In addition, the space harmonic selectivities for a linear period-varying folded waveguide and a hyperbolic sine-varying period folded waveguide are also analysed as examples.     

Analysis of a Novel Ka-band Folded Waveguide Amplifier for Traveling-Wave Tubes

A novel Ka-band folded waveguide （FW） amplifier for traveling wave tubes （TWT） is investigated. The dispersion curve and interaction impedance are obtained and compared to the normal FW circuit by numerical simulation. The interaction impedance is higher than a normal circuit through the whole band. We also study the beamwave interaction in this novel circuit, and the nonlinear large-signal performance is analyzed by a 3-D particlein-cell code MAGIC3D. A much higher continuous-wave （CW） output power with a considerably shorter circuit compared to a normal circuit is predicted by our simulation. Moreover, the novel FW even has a broader 3-dB bandwidth. It therefore will be useful in designing a miniature but high-power and broadband millimeter-wave TWT.     

具有分布损耗波导结构的回旋行波放大器绝对不稳定性

 详细推导了具有分布损耗波导结构的回旋行波放大器的色散特性。通过绝对不稳定性振荡出现的条件,给出求解具有损耗波导结构回旋行波管放大器的绝对不稳定性起振电流的数值计算方法。研究结果表明：绝对不稳定性起振电流与损耗波导的集肤深度有关,选择有较大的集肤深度的损耗波导可以提高绝对不稳定性起振电流;绝对不稳定性起振电流同时也与工作磁场偏离饱和磁场的程度以及电子束的纵横速度比有关;通过设计具有分布损耗波导结构的注-波互作用电路,以及工作磁场、电子束的纵横速度比,可以在兼顾带宽、效率的条件下,保证回旋行波管放大器稳定工作。     

An Open Rectangular Waveguide Grating for Millimeter-Wave Traveling-Wave Tubes

Millimeter-wave traveling-wave tube(TWT) prevails nowadays as the amplifier for radar,communication and electronic countermeasures.The rectangular waveguide grating is a promising all-metal interaction circuit for the millimeter-wave TWT with advantages of high power capacity,fine heat dissipation,scalability to smaller dimensions for shorter wavelengths,compact structure and robust performance.Compared with the traditional closed structure,the open rectangular waveguide grating(ORWG) has wider bandwidth,lower cut-off frequency,and higher machining precision for higher working frequencies due to the open transverse.It is a potential structure that can work in the millimeter wave and even Terahertz band.The rf characteristics including dispersion and interaction impedance are investigated by both theoretic calculation and software simulation.The influences of the structure parameters are also discussed and compared,and the theoretical results agree well with the simulation results.Based on the study,the ORWG will favor the design of a broadband and high-power millimeter-wave TWT.     

Theoretical Study of Millimeter Wave Harmonic Oscillator Stabilized with a Transmission Cavity

An equivalent circuit model of millimeter wave second harmonic oscillator stabilized with a transmission cavity has been proposed for constructing analytical formulations between performance parameters of the oscillator and parameters of the circuit. The model consists of an equivalent circuit of fundamental wave and that of second harmonic wave. Each of the circuits comprises circuit models of main cavity, transmission waveguide, and transmission cavity. Absorbing material placed between the transmission waveguide and the transmission cavity can suppress additional resonances originated from transmission cavity. The behavior of the second harmonic oscillator can be effectively described by the circuit model. Furthermore, based on this model, mechanical tuning characteristics have been studied at first, and then analytical formulas for quality factor and efficiency depending on circuit parameters have been derived. The circuit parameters can be conveniently extracted by electromagnetic field simulation. Hence the formulas exhibit both compact form and enough accuracy. Thereafter, general rules of performance parameters varying with circuit parameters have been deduced for the harmonic oscillators. Then some design considerations have been derived according to the corresponding analysis. The equivalent circuit model is useful for designing and adjusting millimeter wave second harmonic stabilizing oscillator with a transmission cavity.     

Theoretical Study for Folded Waveguide Traveling Wave Tube

A wideband folded waveguide traveling-wave tube (TWT) amplifier has advantages of simpler coupling structures and robust structure over the conventional helix TWT. The phase velocity of waves in folded waveguide is slowed down to the velocity of electron beam. Slow-wave interaction with the electron beam in folded waveguide is studied in a linear fashion. For a cold beam, the linear theory predicts a gain of 2 dB/cm and a bandwidth of 37% at the center frequency of 14 GHz. A closed algebraic dispersion relation for the frequency and the axial phase shift per period is obtained using an equivalent circuit model. Numerical solution calculated from the dispersion relation and three-dimensional electromagnetic code, HFSS simulations predict a mode coalescing in the folded waveguide. And a theoretical phase velocity prediction of the electromagnetic wave in this circuit is verified by HFSS simulations.     

The development of nonradiative dielectric waveguide transmitting front-end in Ka-band

The operating theory,design method and experimental results of the nonradiative dielectric waveguide (NRD-guide) transmitting front-end in millimeter wave band are related in details in this paper. As a kind of dielectric waveguide,the NRD-guide possesses fine transmission performances, and it can be used to fabricate the millimeter wave hyterodyne integrated circuits. The two kinds NRD-guide transmitting front-ends substantiated in the paper, the voltage controlling oscillator(VCO) and twin-Gunn-diode power-combiner,have very similar structures to each other and possess compact sizes, fine machinery and electric performances.For the VCO front-end in Ka-band, the frequency modulation band is greater than 150MHz, the output power is larger than 20mW.For the power-combiner, the output power is larger than 40mW,the combination efficiency is better than 90%,the frequency stabilization reaches 1.68×10^–5. Combined with the receiving front-end reported before,the transmitter and receiver can be composed to a dielectric waveguide R/T module to be applied in some millimeter wave sub-systems.     

Estimation of RF Parameters for Millimeter Wave Ring-Bar TWTS

In millimeter wave band, interaction impedance and efficiency of the ring-bar circuit are higher than helix. Ring-bar traveling wave tubes (TWTs) do not easy yield backward wave oscillation at high operating voltages. Thus ring-bar TWTs can reach higher power lever. On basic of computation of dispersion and interaction impedance, a fast estimation models of RF parameters for MMW ring-bar TWTs are given in this paper. It is available in designing tube to reduce developing period.     

W波段折叠波导行波管振荡抑制

为了抑制W波段折叠波导行波管研制中的自激振荡,保证行波管正常放大工作,分析了折叠波导慢波结构中反射振荡、返波振荡和带边振荡的产生原因,开展了折叠波导行波管振荡抑制技术研究,通过优化设计和工艺研究采用周期跳变作为关键技术用于W波段折叠波导行波管的研制。通过模拟检验和实验验证,证明采用了振荡抑制技术后行波管自激振荡得到了有效的抑制,W波段脉冲行波管在20%占空比时脉冲输出功率大于100 W,带宽大于5 GHz。