A Kind of Magnetron Cavity used in Rubidium Atomic Frequency Standards Yang Shiyu(杨世宇), Cui Jingzhong(崔敬忠), Tu Jianhui(涂建辉), Liang Yaoting(梁耀廷)

研究了一种应用于铷原子频标的磁控管腔,其中包括磁控管腔的主要特征和参数计算,测试结果与计算理论吻合较好,所设计的磁控管腔能够满足铷原子频标的设计要求。     

铷原子钟微波谐振腔的发展与应用

随着现代通信技术以及市场需求的发展，铷原子钟产品不断更新迭代，正在向小型化、高性能的方向发展。微波谐振腔作为铷原子钟的核心部件，正在不断向小型化方向发展。本文阐述了铷原子钟工作原理以及微波谐振腔的谐振理论，分析了铷原子钟常用的谐振模式及其场分布，介绍了铷原子钟微波谐振腔的发展以及模式转变，由此发展了填充陶瓷介质的TE₁₁₁标准谐振腔以及模式类似TE₀₁₁的非标准谐振腔。铷原子钟微波谐振腔未来也将继续向着体积更小、性能更高的方向发展。     

旭日型磁控管谐振系统的等效电路模型与分析

通过分析旭日型磁控管的等效电路,利用扇形谐振腔的等效电容和等效电感的计算公式,计算旭日型磁控管各模式的谐振频率;简化了谐振频率的计算公式,得到了谐振频率关于结构尺寸的解析表达式;分析了π模谐振频率随大、小腔的半径、角度的变化情况。 结果表明:等效电路计算结果与仿真结果基本一致,特别是π模谐振频率十分相符。 因此,该等效电路计算方法是可行的。π模谐振频率随大、小腔半径和小腔角度的增大而减小,随大腔角度的增大而增大,研究结果有助于旭日型磁控管的预先设计与分析。     

用于折射率仪的高Q腔谐振频率跟踪系统

提出了一种用于折射率仪的采用方波调制的微波高Q腔谐振频率跟踪系统，分析了其工作原理。计算机仿真结果表明，系统跟踪速度快，稳定性好，无稳态误差；在小型微波折射率仪中的应用结果表明，作为系统输出的VCO频率对高Q腔谐振频率的跟踪灵敏度优于5×10-8f0（f0为高Q腔谐振频率）。     

高品质因子氧化硅微腔的制备和光频梳产生(特邀)

基于超高品质因子（Q值）和非线性光学微腔产生的光学频率梳（微腔光频梳）在大容量光通信、光学数据中心、光子神经形态运算以及大规模并行激光雷达等方面有着重要的应用。回音壁模式（WGM）微腔是研究微腔光频梳技术的一个重要平台,具有创纪录的超高Q值和超高精细度（Finesse）,能够实现超窄线宽激光、窄线宽光学频率梳,合成超低噪声的光子微波;同时也是研究腔内孤子动力学的重要平台,对掌握孤子态的光学频率梳特性起到了重要的支撑作用。利用二氧化碳（CO₂）激光器熔融氧化硅（SiO₂）石英棒制备了高Q值的WGM微腔。其自由光谱范围（FSR）在10 GHz以上,Q值达到了108。对腔的谐振和耦合理想特性进行了表征,并在开放环境下观察到微腔受潮引起的Q值退化现象,通过二次退火实现了Q值的回升。在SiO₂微腔中验证了基于非线性克尔（Kerr）效应的光学频率梳产生,其主要状态为调整不稳定性主导的低相干频率梳。同时,实验中也观察到了对应于全相干耗散孤子态频率梳的“阶跃”信号,表明目前制备的SiO₂微腔具备实现低噪声孤子光频梳的能力,并具有微腔光频梳的应用潜力。     

高Q值小型化氢频标蓝宝石微波腔的实验研究

针对蓝宝石氢原子频标的小型化问题,通过理论分析推导出微波腔参数的求解方程;通过计算机仿真分析,提出了设计小型微波腔的方法.该方法利用腔频率、Q值随腔尺寸及填充蓝宝石尺寸的变化关系,在保证温度系数的前提下,获得一种高Q值、小尺寸宝石的小型化腔,并利用仿真软件进行验证及优化,最后通过实验测得了该微波腔的参数,与仿真计算结果基本一致.实验得到该腔的Q值为68000,温度系数为-59.7kHz/℃,圆柱腔的外径为153mm,高度为172mm,与传统微波腔的参数(其中Q值50000,温度系数-62kHz/℃,腔外径176mm)相比有较大进步.     

回旋速调管群聚腔研究

本文采用场匹配法对回旋速调管群聚腔进行了理论分析和数值模拟,讨论了两端开孔对腔谐振特性的影响及引入损耗介质层降低Q值方法,给出了一种工作频率为34GHz,工作模式为TE 01的回旋速调管低Q群聚腔的计算结果,结果表明,开孔大小明显影响腔内的谐振特性及驻波分布,损耗介质层的厚度增加将使群聚腔Q值迅速降低,选择适当的腔体结构,损耗介质及其厚度能有效地降低Q值,满足设计要求.     

捷变频磁控管最新的发展动态

1概述微波真空电子器件一个重要管型——磁控管，直到二次世界大战中，英国发明了多腔磁控管装备于雷达系统后，这类微波器件得以迅速发展，成为具有许多型号的大量管种，包括：脉冲磁控管、同轴磁控管、频率捷变磁控管、电压调谐磁控管以及连续波磁控管等。磁控管是正交场器件的一个类型，正交场器件又称“M”型器件，所谓正交场器件是指管内直流磁场方向与电子漂移运动主方向和直流电场的方向相互垂直，由于这种与电子运动方向相垂直的磁场存在，使得正交场管内的电子运动特性发生了很大变化，并出现特有的相位聚集、电子挑选、电子回轰…     

识别同轴磁控管各种模式的场分析

本文对同轴磁控管电磁系统进行了分析。分析时把系统看作是几个径向波导的组合,这些径向波导从阴极通过阳极叶片和内腔壁上的隙缝伸展到同轴外腔。得到了以隙缝为参考端的导纳(对于任意频率)。此导纳服从福斯特(Foster)电抗定理,它的零点揭示了系统的谐振特性。电纳随频率变化的速率揭示了系统的储能,并使我们能够计算它的R_(sh)/Q值。除了这些谐振腔的谐振以外,还有外腔和叶片系统组成的折迭线所产生的谐振。谐振时,线长等于半波长的整数倍,主π模对应于两个半波长,而另一个π模则出现在较低的频率(对应于一个半波长)和较高的频率上(对应于三个或三个以上的半波长。) 分析结果和VMS-1178同轴磁控管的测量值作了比较,各种观测到的振荡确实为理论所证实。     

不同方法制备BiNbO4微波陶瓷的研究

研究了固相反应法和熔盐法两种制备方法对BiNbO4微波陶瓷的烧结温度、微观形貌、结构和介电性能的影响。实验表明:在添加CuO和V2O5分别为0.1%(质量分数)时,固相反应法在较低的烧结温度下可获得较致密的陶瓷样品,样品表面晶粒呈球状,品质因数与谐振频率的乘积即Q×f值较大,谐振频率温度系数为正值;熔盐法制得的陶瓷样品具有明显的各向异性,晶粒呈棒状,谐振频率温度系数随烧结温度的升高由正值向负值变化,在940℃烧结,介电常数为38,Q×f值为7781 GHz,谐振频率温度系数近零,为0.92×10-6/℃。两种方法制得的陶瓷样品在微波频段介电常数相近。     

A kind of magnetron cavity used in rubidium atomic frequency standards

Research on the magnetron cavity used in the rubidium atomic frequency standards is developed, through which the main characteristic parameters of the magnetron cavity are studied,mainly including the resonant frequency,quality factor and oscillation mode.The resonant frequency and quality factor of the magnetron cavity were calculated,and the test results of the resonant frequency agreed well with the calculation theory.The test results also show that the resonant frequency of the magnetron cavity can be attenuated to 6.835 GHz,which is the resonant frequency of the rubidium atoms,and the Q-factor can be attenuated to 500-1000.The oscillation mode is a typical TE₀₁₁ mode and is the correct mode needed for the rubidium atomic frequency standard.Therefore these derivative magnetron cavities meet the requirements of the rubidium atomic frequency standards well.     

一种宽带速调管中高次模式振荡的抑制

该文描述了在一种S波段宽带速调管研制过程中出现的高次模式振荡现象,分析了抑制这种振荡的可能方式,提出了一种抑制这种振荡的方法。该方法通过改变谐振腔结构,在基本不影响基模频率的前提下,使高次模式频率产生较大的改变,从而使该高次模式的振荡得到抑制。利用Ansoft HFSS模拟设计软件,对谐振腔进行了改进设计并完成了相应的实验验证。利用改进设计的谐振腔,进行了速调管整管试验,有效地抑制了速调管中高次模式的振荡。     

无隔模带磁控管谐振系统的理论分析与仿真

为了提高磁控管稳定性,需要研究各耦合因素对磁控管谐振频率及模式分隔度的影响。该文采用等效电路的方法,给出了无隔模带磁控管在电容、电感耦合下的谐振频率及模式分隔度的表达式,并分析谐振频率随模数的变化趋势及电感、电容耦合强弱对模式分隔度的影响。采用CST-MWS软件对不同阴极半径及顶盖高度的谐振系统的谐振频率进行仿真,并将仿真结果与理论结果进行对比。理论分析与计算机仿真表明,对于无隔模带磁控管谐振系统,电容耦合使谐振频率随模数的增大而增大,电感耦合使谐振频率随模数的增大而减小;两者分别通过增大和降低模频率从而增大模式分隔度,两者共同作用时模谱图取决于占主导地位的耦合因素。     

The optically pumped rubidium maser

The optically pumped rubidium maser oscillator is the most recent addition to a growing number of atomic frequency standards. It is the first atomic frequency standard which is small enough and simple enough to be considered as a replacement for crystal oscillators. These factors and the extreme phase stability which results from the maser action make this device unique among all frequency standards. The device generates a microwave output at the ground-state hyperfine frequency of Rb⁸⁷(6835 Mc/s). The maser consists of a microwave cavity filled with Rb⁸⁷vapor and nitrogen gas. Oscillation occurs when the vapor is illuminated with filtered rubidium resonance radiation. The power output of the maser is 10^-10watts, and higher powers can be expected. In this paper the physical principles and construction of the device are described. The effects of optical pumping, buffer gas, and temperature on the maser are discussed, and experimental results are given. The short-term stability for observation times of about one second is expected to be about one part in 10¹². This may be increased by an order of magnitude by increasing the powser output to 10^-8watts. The long-term stability is expected to be comparable to that obtained in the passive rubidium standard (about one part in 10¹¹per month). These slow fluctuations arise from pressure shifts, light shifts, cavity pulling, and changes in the chemical composition of the buffer gas. The long-term stability can be improved by using the rubidium maser as the flywheel for an atomic beam frequency standard. Such a combination could be expected to have both long-term and short-term stabilities as great as one part in 10¹³.     

Effect of External Circuits on Gunn Oscillation

The "resonant mode" of oscillation of a Gunn oscillator is analyzed. Experimental results show the frequency of oscillation of the "quenched dipole mode" depends on the load admittance. These characteristics can be explained by a proposed model which considers the formation and extinction of a dipole layer due to the RF voltage excited in a resonant cavity. The discussion accounts for the time constant of the growth and decay of a dipole layer and derives the susceptance and negative conductance components of the diode model.     

Short-term stability of passive atomic frequency standards

The instability of passive atomic frequency standards caused by shot noise introduced by the atomic reference is calculated. This instability can be characterized by a figure of merit for the atomic reference, and the asymptotic functions for the rms frequency fluctuation for long and short averaging times expressed in terms of this quantity. Measurements of the rms frequency fluctuation of cesium atomic beam and rubidium vapor frequency standards are compared with theory, and the predicted performances of various existing and proposed atomic standards are tabulated. It is feasible to build atomic beam frequency standards whose stability for averaging times less than one second is limited by noise in the crystal oscillator rather than by shot noise, a criterion generally met by rubidium vapor frequency standards. For long averaging times, shot noise will always be the fundamental limiting factor in atomic frequency standard stability.     

An interpretation of magnetron problem

The electron motions inside a magnetron can be understood by dividing them into three stages. At low voltage the turbulent nature of electron motion may produce high electron temperature which, in turn, causes both violation of Hull's cutoff condition and back bombardment of the cathode. As the voltage reaches such a value that the average back bombarding energy makes the coefficient of secondary emission greater than one, a process of cyclic multiplication at the cathode surface may happen, and it has the property to transform the disorder motion into space-charge oscillation which has been repeatedly observed in smooth-bore magnetrons. When the predominating mode of the space-charge oscillation synchronizes with the π mode frequency of the cavity resonators, the magnetron oscillates.     

Cavity decay rate and relaxation oscillation frequency inunconventional laser cavities

Measuring the relaxation oscillation frequency ω_r versus the normalized pumping rate r can provide a useful technique for determining either cavity or atomic parameters in many different kinds of lasers. Measurements of relaxation frequency versus pumping rate in a Nd:YAG laser using a gain-guided unstable-cavity design were recently found, however, to yield values of cavity decay rate which were unreasonably large compared to other estimates of the cavity losses. This difficulty has been resolved by a closer look at the relaxation oscillation dynamics in this type of laser. We find that in nonorthogonal laser cavities with nonuniform gain distributions the energy decay rate of the cavity oscillation mode usually employed in the relaxation frequency formula must be replaced by a different decay rate relevant to oscillation mode perturbations. A numerical simulation including this more general effect gives values very close to our experimental results, confirming the validity of this modified analysis     

Resonant Frequency of Open-Ended Cylindrical Cavity

The TE/sub 011/ mode of oscillation in an open-ended circular cylindrical microwave cavity is analyzed. The cavity consists of a circular waveguide that is terminated at each end with a thin cylindrical partition coaxial with the circular waveguide. The resonant frequency of the cavity is computed by using Laplace transform and Wiener-Hopf techniques. Numerical values for the resonant frequency are presented.