大功率毫米波行波管AM/PM转换特性大信号解析理论的研究

毫米波行波管是未来通信发展的重要方向,由于AM/PM转换是影响毫米波行波管通信的重要非线性特性指标,因此AM/PM转换的研究对实现毫米波行波管线性化具有重要意义．本文基于相位展开的毫米波行波管欧拉大信号注波互作用理论模型,忽略高于二阶的非线性项,建立简化的欧拉大信号注波互作用理论模型．采用逐次逼近法推导其解析解,建立二阶逼近的欧拉大信号解析理论模型．利用欧拉大信号解析理论模型推导AM/PM转换的解析解,并发现AM/PM转换的产生与电子相位直流分量的激励成正比．应用建立的欧拉大信号解析理论和AM/PM转换解析模型对一支Q波段毫米波行波管进行大信号分析,并与拉格朗日理论模型以及传统的欧拉非线性理论模型进行对比．结果表明：欧拉大信号解析解的功率、增益和相移以及AM/PM转换与拉格朗日理论在线性区和中度互作用区十分吻合,饱和增益最大误差小于8.5%．同时,相较于传统的欧拉非线性模型,欧拉大信号解析解对非线性区增益和相移非线性特性的描述更具优势,即不但具有更高的精度,而且表现出传统欧拉非线性模型无法描述的增益压缩和相位失真现象．仿真结果验证了欧拉大信号解析解和AM/PM转换解析模型在线性区到中度互作用区的正确性和有效性．该AM/PM转换解析模型为后续研究毫米波行波管AM/PM转换非线性特性的物理机制与抑制方法奠定了基础．     

一种行波管用毫米波射频预失真线性化器

射频预失真是提高功率放大器线性度的一种有效手段,精确补偿放大器的非线性失真需保证幅度和相位补偿同时满足要求.针对Ka波段行波管放大器的线性化,提出一种新型射频预失真电路.该电路由前置、后置电平调节模块和基于矢量合成技术的非线性信号产生模块构成.改变两电平调节模块的增益,可实现补偿区间的调节;改变非线性信号产生模块中两支路的偏置电压,可实现预失真补偿量调节及幅度/相位的独立调节.将实际电路与配用Ka行波管联测,在输出功率回退6 dB时,行波管三阶互调系数提高约11.5 dBc.     

模拟信号在SOA中的交叉相位调制特性研究

为了研究模拟光信号在半导体光放大器中的交叉相位调制特性,以正弦波和三角波两种模拟光信号为例,采用数值计算的方法,详细分析了交叉相位调制过程中模拟信号的增益、非线性相移差和啁啾。结果表明,当信号光和控制光之间采用帧同步方式时,信号光脉冲各点的增益及增益差出现波动,非线性相移差将围绕理想值π出现不同程度的偏离;采用比特同步方式可使信号光脉冲各点非线性相移差均衡,此时所需的控制光脉冲和信号光脉冲波形类似。     

短射频脉冲相位测量系统

本文所述的相位测量系統主要是用于測定大功率行波管所产生的窄射頻脉冲的相位变化的。这种测量技术也适用于精确地测定工作过程中管子参量改变时所出現的相对相移。它是一个双臂系統,用一个平衡调制器产生一个偏置信号,同时用一个零拍检波器把相位信息轉换成一个高的中频信号。这种特殊的另值法,即使被比較的信号幅度在一个相当大的范围內变化时,也能保証高精度测量。     

零相移瞬时极化滤波器

常规极化滤波方法会造成目标信号相位的改变,滤波器参数的变化影响相移的大小,进而导致相位失真.为避免相位失真,本文在普通单凹口、多凹口逻辑积极化滤波器的基础上提出零相移瞬时极化滤波器,通过线性极化变换、普通极化滤波和相位(和幅度)的补偿实现目标相位(幅度)的保持.实际数据的处理结果表明,在抑制高频雷达电台干扰的实验中,信干比改善可以达到27dB以上.     

一种螺旋线型空间行波管的线性设计

本文介绍一种螺旋线行波管的线性设计,该行波管用于通信。为保证通信信号的质量,该型行波管必须具有较好的线性性能,如相移、三阶交调等,文中将结合一种Ka频段空间行波管的改进过程,以相移作为线性参数的代表性指标,分析所采取的改进措施对行波管线性性能的提升。目前,该行波管的主要高频参数为:相移50°(饱和回退20dB)、饱和增益50dB、互作用效率20%。     

幅相一致低杂散多通道上变频器设计

介绍了一种幅相一致、低杂散多通道上变频器的电路组成及混频、滤波及增益控制等关键电路的设计。论述了杂散的产生及抑制,对影响幅度一致性和相位一致性的因素进行了分析,并提出了控制多路上变频器的幅度一致性、相位一致性的方法。该多通道上变频器的幅度一致性优于1dB,相位一致性优于6°,带内杂散优于-60dBc,带外杂散优于-45dBc。     

行波管放大器相位噪声的分析及其抑制

主要分析规则调相信号对行波管放大器频谱纯度的影响,并且根据行波管放大器相位噪声产生的过程和原因,提出两种抑制相位噪声的方法.     

一种Ku波段空间行波管预失真器

提出一种无需直流偏置的Ku波段空间行波管预失真器.基于90°电桥、反向并联GaAs肖特基二极管对和负载电阻,产生预失真信号.同时可通过改变微带线长度和负载阻值实现可调性.此外,该电路自身具有良好的输入输出匹配特性,简化了电路结构.实测结果表明,该预失真器在带宽500MHz范围内可获得约7dB增益扩展和45°相位扩张.与行波管联测表明,行波管双音饱和输入功率回退3dB时,三阶交调可获得约6dB的改善效果.     

耦合腔行波管功率合成

介绍了脉冲幅相一致耦合腔行波管的研制,并较为详细地介绍和分析了耦合腔行波管功率合成实验--脉冲相位一致性测试的一种途径.     

Accurate parametric modeling of folded waveguide circuits for millimeter-wave traveling wave tubes

In this paper, results of different models are compared for calculating effective, cold-circuit (beam-free) phase velocities and interaction impedances of folded waveguide (FW) slow wave circuits for use in millimeter-wave traveling wave tubes (TWT). These parameters are needed for one-dimensional (1-D) parametric model simulations of FW traveling wave tubes (FWTWTs). The models investigated include approximate analytic expressions, equivalent circuit, three-dimensional (3-D) finite difference, and 3-D finite element. The phase velocity predictions are compared with experimental measurements of a representative FW circuit. The various model results are incorporated into the CHRISTINE1D code to obtain predictions of small signal gain in a 40-55 GHz FWTWT. Comparing simulated and measured frequency-dependent gain provides a sensitive, confirming assessment of the accuracy of the simulation tools. It is determined that the use of parametric 1-D TWT models for accurate, full band predictions of small signal gain in FWTWTs requires knowledge of phase velocity and impedance functions that are accurate to <0.5% and <10%, respectively. Saturated gain predictions, being approximately half as sensitive to these parameters, appear to require correct specification of phase velocity and interaction impedance to within /spl sim/1% and 20%, respectively. Although all models generate sufficiently accurate predictions of the interaction impedance, not all generate sufficiently accurate predictions of the effective axial phase velocity.     

Linear Analysis of Traveling Wave Tubes with Nonuniform Lossy Interaction Structures

A linear theory model is developed to analyze traveling wave tubes (TWT) employing distributed wall loss. The loss can be a function of position. The electronic and circuit equation are derived, taking into account the spatial variation of the circuit loss. This model can be used to provide a first-cut design of the TWT.     

脊加载环板行波管高频特性的研究

脊加载环板行波管是一种频带相对较宽的大功率行波管,本文用场匹配和变分原理相结合的方法,研究了脊加载环板慢波结构的导波特性及这种行波管的小信号、大信号特性,讨论了结构的几何尺寸及电子注参量对慢波的传播特性、小信号增益及注-波互作用非线性效应的影响.本文的结果将为脊加载环板行波管的设计提供理论基础.     

Theory of long term gain growth in traveling wave tubes

The properties of the attenuator materials used in traveling wave tubes (TWT) are a major factor in determining the gain of the tube. Carbon is a commonly used attenuator material which is typically deposited on the dielectric rods used to support the helix slow wave structure in TWTs. The deposited carbon layers are susceptible to ion bombardment induced damage during operation and outgassing of the tube, which increases the electrical resistivity of the layer and reduces the rf loss in the tube. The total gain in the tube grows during this process until the bombardment ceases or the layer damage saturates. A simple theory is developed that relates this gain change to the gas evolved in the tube that results in the particle bombardment of the layers during operation. The model accurately describes the observed time dependent behavior of the gain, and the time constant for outgassing the tube is found for several tubes ranging from S to Ka band. The time constant increases significantly for smaller, high frequency tubes with a low conductance and poor pumping speeds. The model shows that stabilization of the gain occurs after several time constants have passed, which may take hundreds to thousands of hours     

Design of a tapered helix for suppressing backward wave oscillations in MMW TWT’s

Backward wave oscillations are easy occurred in high power helix millimeter wave traveling wave tubes (MMW TWT’s), owing to larger ka value and higher operating voltage. The start current of backward wave is calculated for helix TWT in Ka band. It is shown that start current will increase by used a tapered helix. Backward wave oscillations can be suppressed in tube. The design method of the tapered helix is given in this paper.     

Design of a 300 GHz Band TWT with a Folded Waveguide Fabricated by Microelectromechanical Systems

For future broadband wireless links, we have designed a 300 GHz band traveling wave tube (TWT) with a folded waveguide fabricated by microelectromechanical systems (MEMS). The TWT operates at a beam voltage of 12 kV and a beam current of 8.3 mA. The classical large signal simulation code predicts the output power greater than 1 W and gain larger than 20 dB over the bandwidth from 280 to 300 GHz.     

高效率X波段40W空间行波管的设计

作为卫星通讯系统所用的高增益、高功率微波放大器件,行波管的效率和线性是非常重要的.本文根据卫星通讯的需要,给出了高效率X波段40 W空间行波管的设计,并成功研制出了样管.     

高效率毫米波行波管

行波管可以应用于雷达和卫星系统中,具有高效率、高功率和高增益的特点。文章介绍了国际上高效率毫米波行波管研制现状,分析了提高行波管效率的几个主要方法,包括提高电子效率、收集极效率及高性能电子光学技术。     

Calculation of the Parameters for Ring-loop Traveling Wave Tube in MMW

The feature of the ring-loop slow wave structure is high coupling impedance and low harmonic wave components. Therefore ring-loop traveling wave tube (TWT) has advantages of high gain, small dimension, higher operating voltage and less danger of the backward wave oscillation. But calculation of the ring-loop is rather difficult. Here on basis of calculation of dispersion and impedance, a fast estimation of interaction efficiency, output power and saturated gain for Ka-band ring-loop TWT are given.     

Space qualified low-/high-power radar TWTs

This paper is a report about recent development activities in the area of space-qualified pulsed traveling wave tubes (TWTs). For an economical development in such a low-volume market, the application of a modular design concept is necessary. As an example for such a concept, two projects will be described, a high-power X-band TWT with 6-kW peak output power and a low-power Ku-band TWT with 135-W peak output power.