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。     

半导体中的谷间电子转移和体振荡

从GaAs/AlAs量子阱的量子限制、能带混合和隧穿共振中发现了新的异质谷间转移电子效应。用它制成了定位精度高的高效谷间电子布居控制极。把这种控制极设置于耿氏有源层的阴极端,消除了器件中的死区,抑制了强场畴,产生高效的电场弛豫振荡模。通过长有源层样品的模拟设计,发现了新的触发多电子束弛豫振荡模,实现了体振荡。模拟设计得出在20～25GHz频段能获得50W以上的脉冲振荡输出,效率大于40%。     

Correction Due to a Finite Permittivity for a Ring Resonator in Free Space

To better determine the resonant fields of a dielectric resonator with high permittivity epsilon/sub r/, the asymptotic theory with1//spl radic/epsilon/sub 3/ as a small parameter is extended by adding higher order terms in 1//spl radic/epsilon /sub r/ in the fields, the resonant wavenumber, and radiation Q. Extensive data are shown for the Phi independent "nonconfined" mode of a ring resonator, which radiates as a magnetic dipole. Some results are added for the "magnetic quadruple" mode.     

Mode tuning and hysteresis behaviour of Gunn-effect cavity-controlled generator

It is shown that, for both the bias voltage and the resonant circuit oscillation period, a range exists in which two values of oscillation amplitude are possible. These values correspond to the mixed mode and to the under-voltage resonant mode. The conditions for the transition from one mode to another are investigated.     

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。     

用于铷原子频标的磁控管腔研究

研究了一种应用于铷原子频标的磁控管腔，对用于磁控管腔的主要特征和参数计算进行了研究，主要包括磁控管腔的谐振频率、Q值、微波场模式。研究结果表明磁控管腔的谐振频率可以调谐至6.835GHz，Q值都能够调至600～1000之间，其微波场谐振模式是典型的TE011模式，频率温度系数较小（32.5KHz/℃－35.0 KHz/℃），所设计的磁控管腔能够满足铷原子钟物理部分的设计要求。     

Observations of voltage and current waveforms of the transferred electron oscillators

The results of the observations of current waveforms of the resonant domain mode and the LSA mode are presented. The drift current which is very characteristic of the LSA oscillation is experimentally revealed by the subtraction of the displacement current from the total current, thereby confirming the oscillation of the LSA mode.     

240-325-GHz GaAs CW fundamental-mode TUNNETT diodes fabricated with molecular layer epitaxy

Gallium arsenide (GaAs) transit-time diodes with tunnel injection of electrons (TUNNETT) with transit-time layer thickness of 100 and 150 nm were fabricated with molecular layer epitaxy (MLE). Continuous-wave fundamental-mode oscillation in the frequency range of 240 to 325 GHz in metal rectangular resonant 0.86 /spl times/ 0.43 mm size (WR-3) cavities was obtained. Output power of -13 dBm was generated at 322 GHz. The fundamental mode operation, as well as experiments on different impedance matching configurations, suggest that it is possible to develop fundamental mode TUNNETT generators for the frequency range of 350 GHz to 1 THz. Operation of the TUNNETTs confirms device quality of the MLE.     

Printed dual-band dipole antenna with U-slotted arms for 2.4/5.2 GHz WLAN operation

Dual-band operation of a printed dipole antenna with U-slotted arms is presented. Due to the embedded U-shaped slots, two additional dipole arms are obtained in the proposed design, which form a second dipole antenna with a smaller length and which can generate a higher resonant mode for the 5.2 GHz band operation. By incorporating the original dipole arms designed for the 2.4 GHz band operation, the proposed antenna can perform WLAN operations in the 2.4 and 5.2 GHz bands.     

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.     

An Analysis of an Electronically Tunable N-GaAs Distributed Oscillator

The effective Schottky-barrier height of a contact to n-GaAs can be designed arbitraily by interposing a thin, highly doped layer between a metal and n-GaAs and by controlling the thickness optimally. An n-GaAs diode with a Schottky-barrier cathode exhibits various space-charge modes depending on the barrier height. A traveling dipole domain mode in an n-GaAs diode changes into a cathode trapped domain mode as the injection current at the cathode decreases. It has been shown that an n-GaAs diode, which operates in a cathode trapped domain mode, exhibits a negative conductance over a fairly wide frequency range. A super semiconductor. wide-band electronically tunable distributed oscillator can he achieved by inserting an n-GaAs diode with a suitably designed Schottky-barrier cathode between resonant microstriplines in place of conventional dielectric material. It has been shown that the frequency of the distributed oscillator would be electronically tunable over a fairly wide frequency range from 9 to 26 GHz.     

Self-sustained phase-shift modulated resonant converters: modeling, design, and performance

This paper presents an improved control technique for the full bridge series, parallel, and series-parallel resonant converters. This control technique combines a self-sustained oscillation mode with a phase shift modulation technique that can significantly reduce the range of frequency variation necessary for obtaining zero voltage switching in the resonant converters. This frequency reduction provides optimized component ratings and operating frequency. A simple and accurate low order mathematical model based on the sampled data technique that fully describes the steady-state, and dynamic performance of the resonant converters, has been developed. A refinement algorithm is developed to enhance the accuracy of the modeling technique and the converter design. The improved converter performance and the feasibility of the developed dynamic model have been investigated using the series-parallel resonant converter topology with a capacitive output filter. Finally, MATLAB numerical solutions, PSIM simulation results, and experimental results are given to highlight the merits of the proposed work.     

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.     

Plasmon-Excitonic Polaritons in Metal-Semiconductor Nanostructures with Quantum Wells

A theory of plasmon-exciton coupling and its spectroscopy is developed for metal-semiconductor nanostructures. Considered as a model is a periodic superlattice with cells consisting of a quantum well and a layer of metal nanoparticles. The problem is solved self-consistently using the electrodynamic Green’s functions taking account of resonant polarization. Coulomb plasmon-exciton interaction is associated with the dipole surface plasmons of particles and their image charges due to excitonic polarization of neighboring quantum well. Optical reflection spectra are numerically investigated for superlattices with GaAs/AlGaAs quantum wells and silver nanoparticles. Superradiant regime caused by one-dimensional Bragg diffraction is studied for plasmonic, excitonic and plasmon-excitonic polaritons depending on the number of supercells. The plasmon-excitonic Rabi splitting is shown to occur in reflectivity spectra of resonant Bragg structures.     

Resonant Coherent Acoustic Oscillation in Nanoscale Ruddlesden–Popper Perovskite Films

Time-domain study of coherent acoustic phonons in nanomaterials provides dynamic and unparalleled insight into their mechanical and structural features. Ruddlesden–Popper (RP) perovskite shows excellent acoustic behaviors due to the large impedance mismatch between its hard perovskite frameworks and soft organic chains. However, the optical probe-independent acoustic nano-mechanical resonance and its real application in this important class of semiconductors have not yet been achieved. Herein, the acoustic breathing mode of resonant coherent phonons (RCP) in nanoscale RP perovskite films is reported. In contrast to the previously reported Brillouin mode in thick materials, such resonant breathing mode is no longer interfered by the optical probe, but as a self-sustained acoustic oscillation source whose features are directly related to material geometry along the direction of phonon propagation. As a nano-mechanical resonance, RCP oscillation is applied as a novel and non-destructive approach for quantitatively evaluating the decomposition of moisture-exposed RP perovskite. These results reveal the decisive effect of structural geometry on acoustic performances in perovskite nanomaterials. The nanoscale counterparts show evident advantages in acoustic mode modulation and structure detection.     

Design and analysis of a coaxial coupler for a 35-GHz gyroklystronamplifier

A single rectangular TE₁₀ feed four-slot coaxial coupler is designed and built for excitation of a TE₀₁₁ cylindrical cavity mode for use in high-power millimeter-wavelength gyroklystron amplifiers. A high degree of mode purity is obtained and matching of the cavity to the input line is studied. A model based on the mode-matching technique and dipole radiators has been formulated to predict operation of this coupler. The resulting numerical code is capable of finding resonant frequency and cavity bandwidth in a small fraction of the time taken by more general finite-difference/finite-element design tools. The model can be extended to self-consistently include an electron beam, and the model is compared to a coupler design based on Hewlett-Packard's High-Frequency Structure Simulator code. The coupler has been successfully used in a high-power gyroklystron-amplifier experiment     

A low-frequency analog for a Gunn-effect oscillator

After a brief introduction to the Gunn effect and an explanation of the proposed equivalent circuit of the Gunn diode, a low-frequency (5 Hz) lumped-circuit analog is described. The analog is able to simulate the initiation and circuit quenching of the domain, the transit time of a dipole domain, and the dynamic negative-resistance characteristic associated with the domain. Thus the analog can qualitatively account for many properties of the dipole domain modes. A short section also shows how, within certain limitations, the LSA mode can be investigated by means of the analog. The analog enables the behavior of the Gunn diode to be studied under various forms of loading, and the results to be related to a wide range of actual diodes in microwave circuits by a simple scaling process. The sciencies of various modes can be compared. Photographs are presented of an oscilloscope display showing the relevant current and voltage waveforms (including the domain voltage) for a pure resistive load, a parallel resonant load, and a series inductive load. The provision for a direct display of domain voltage means that a particularly clear visual distinction is possible between transit-time and circuit-quenched modes of oscillation. Tuning by variation of the external load is demonstrated; the importance of the semiconductor's current peak-to-valley ratio and of the choice of transit time in determining the efficiency in a given mode is illustrated. A possible explanation for the reported observation of subharmonics is provided by the analog, on the basis of alternate modes, i.e., a cycle of circuit-quenched operation followed by a cycle of transit-time operation. The limitations of the analog are discussed together with ways in which some of them could be overcome.     

均匀掺杂GaAs光阴极表面势垒特性研究

根据激活过程中光电流变化规律及原位光谱响应测试,模拟了GaAs光阴极表面势垒的形成过程,在光阴极表面双偶极子模型的基础上作了修正,建立了三偶极子模型。新模型认为,光阴极表面势垒由三个偶极层套构而成,第一偶极层由GaAs（Zn）-Cs+偶极子组成,第二偶极层由Cs2O偶极子组成,第三偶极层由GaAs-O-Cs偶极子组成,第二、三偶极层嵌入第一偶极层中。根据隧道效应与量子效率测试结果,确立了势垒中分段均匀的电势分布,计算得出势垒宽度为1.65 nm,有效电子亲和势为-0.44 eV。新模型的建立对理解光电阴极表面发射机理具有重要意义。     

A Sensitivity Analysis of Frequency Selective Surfaces at Millimeter Wave Band

This work presents a sensitivity analysis for the resonant frequency and bandwidth of frequency selective surfaces (FSS) as a function of the structural parameters. The frequency selective surface structure considered here is composed by crossed dipole conductive patches deposited on an anisotropic dielectric layer. Firstly, the moment method is used in combination with the immittance technique in the spectral domain to determine the frequency response of the analyzed structure. Secondly, numerical techniques are used to obtain the resonant frequency and bandwidth sensitivities as a function of the considered FSS structural parameters.