Dependence of Output Power on Cavity Length in a Gyrotron Backward Wave Oscillator

A relativistic electron beam (500 keV, 200 A, 10 ns) generated magnetically tunable microwave radiation in a frequency range of 9-13 GHz when it is injected into an X-band rectangular waveguide immersed in a uniform axial magnetic field (4-10 kG). The mechanism of the microwave radiation was identified as the gyrotron backward wave interaction. The output power of the radiated microwave increased exponentially with the increase of the cavity length.     

The Axially Modulated, Cusp-Injected, Slowly Varied Section Opened Cavity, Magnicon Amplifier

I introduce a novel hybrid microwave amplifier that utilizes the axial bunching mechanism of klystrons in conjunction with the energy extraction mechanism of cyclotron resonance masers on TM mode. A simpler analytic model is used to show the viability of the device configuration and to explore limitations of the scheme. An example of an 11.5 GHz, fourth harmonic amplifier is presented. Adopting a multi-particle in azimuth range of (0, π/2) whose divide thickness of beam into three share approach, numerical simulation are used to demonstrate bunching in physical space and to estimate system efficiency et al. It shall be shown that this configuration enables the design of eficient, high harmonic devices over a wide range of parameters. Magnicon [1]-[11] is a kind of microwave amplifier tabe, it operates on the mode of rotating E_n10 in cylindrical cavity and there is solid focus fine electrons beam. In it from theory, the paper researches the new type magnicon, it is changed into using annular electron beam and using slowly variable section opened cavity. Compared with magnicon, its pervence beams will may be increased, its frequency may be increased up to millimeter wave band, its bandwidth also will may be increased same times. Than model of new type magnicon is put forward. Starting from large signal's theory, interacting of the annular electron beam into driver cavity in between the mode of rotating E_n10, numerical value to simulate. It done on the small current density and small density of electron in space that electrons dynamic are simulated, which may uses Runge-Kutta method to do it.     

Powerful electromagnetic millimeter-wave oscillations produced by stimulated scattering of microwave radiation by relativistic electron beams

The stimulated scattering of electromagnetic waves in microwave generators, in which a high-current electron beam excites either a backward wave (BWO) or a quasi-critical frequency wave (orotron) is investigated experimentally. The scattering occurs at the same electron beam and the high-frequency feedback is provided by the inhomogeneities of the electrodynamic system of the microwave generator itself. A power of several tens of megawatts has been achieved in the 3-mm range. The mode selection permitted to obtain single-mode scattering.     

Electron drift velocity in GaAs using a variable frequency microwave time-of-flight technique

A modified form of microwave time-of-flight technique has been developed which uses a variable frequency microwave deflection system to modulate the electron beam. This enables electron drift velocities to be measured absoslutely over a wide range of values whereas previous microwave time-of-flight measurements have given only relative velocities and require at least one point of normalisation. This new technique has been applied to measure the drift velocity of electrons in n-type GaAs for electric fields up to 135 kV cm^?1 and over the temperature range 77–400 K. For fields above 10 kV cm^?1, excellent agreement is obtained with conventional time-of-flight measurements.     

A cyclotron-wave rectifier for S-band and X-band

A device for converting microwave power into either dc power or low-frequency ac power has been investigated both theoretically and experimentally. Rotational energy is stored in an electron beam by a Cuccia coupler, then converted to longitudinal energy by interaction with a space-dependent dc magnetic field, and finally recovered as electric energy by a depressed collector. A simple kinematic analysis demonstrates that the Cuccia coupler can convert large amounts of microwave power into electron beam rotation. Limits on the electric field strength and asynchronism between signal frequency and cyclotron frequency are established for both classical and relativistic coupler operation. Efficiency analyses of the process of conversion from orbital energy to dc electric energy, both classical and relativistic, indicate that the efficiency exceeds 95 percent for a particular range of operating conditions. As an ac power supply, the device responds to the modulating frequency of the signal. Theory predicts near-negligible harmonic distortion as well as flatness of frequency response from dc to about 1.0 MHz modulating frequency. Four tubes and a prototype (with "artificial" coupler) were tested experimentally. The first three tubes exhibited efficiencies up to 22 percent, being hindered by reflection of electrons into the coupler. Certain design changes were tested on the prototype, where efficiencies from 36 percent to 75 percent were obtained. Incorporating these design changes into the fourth tube yielded measured efficiencies up to 34 percent, or when corrected to disregard unusually large cavity losses, up to 59 percent. Experimental tests of the tube as an ac converter yielded excellent frequency response and about 20 percent second-harmonic distortion. It is concluded that the theoretical foundation of efficiency predictions has thus far been based on too optimistic assumptions.     

Electro-optic diffraction grating for light beam modulation and diffraction

The interaction between a strong traveling microwave signal and an optical beam in an electro-optic material is described in the limit of very high microwave dielectric constant. The interaction produces effects analogous to those produced by a moving diffraction grating. When the optical beam is wider than the wavelength of the microwave signal, the first grating order is resolved from the zero-order or main beam. Under this condition two types of devices become possible: 1) a beam deflector which can position an optical maser beam on, for example, 10⁵distinct points with negligible crosstalk and with address times of order 10^-7s, 2) a baseband light intensity modulator which is founded on the fact that light deflected into the first-order beam by the microwave signal is removed from the main beam. The amount deflected into the first-order beam is proportional to the microwave power; the intensity modulation follows the microwave envelope. The power required for a given modulation depth is inversely proportional to the seven halfs power of the dielectric Constant. As an example, for a not unrealistic choice of dielectric constant of 10⁴, complete transfer from the zero-order to the first-order beam requires 5 watts of microwave power. The interaction length is of order one centimeter and the interaction bandwidth is essentially unlimited. As a baseband modulator the maximum instantaneous bandwidth is of order 10 percent of the subcarrier frequency. Experimental verification is provided in an earlier paper [1].     

低磁场S波段相对论返波振荡器模拟与实验

为实现高功率微波(HPM)系统的小型化,设计一个S波段较低磁场相对论返波管(RBWO)振荡器.针对低磁场特点,分析慢波结构、引导磁场、束压、束流等对输出微波的影响,通过模拟软件(PIC)优化结构.以此设计引导磁场为0.24 T,电子束束压为725 kV,束流为6 kA,频率为3.53 GHz,输出微波功率为1.22 G...     

A 22-GHz-band low-noise down-converter for satellite broadcastreceivers

A simple low-cost and high-performance 22 GHz band down-converter developed for a direct-to-home satellite broadcasting system is discussed. The down-converter consists of a low-noise high electron mobility transistor (HEMT) preamplifier, an image recovery mixer with a particular structure using dielectric resonator filters, a 21.4 GHz GaAs FET oscillator stabilized by a dielectric resonator, and an IF amplifier. These components are fully integrating using microwave integrated circuit technology into a small size. A total noise figure of less than 2.8 dB is obtained over the 22.5-23.0 GHz frequency range. The local oscillator achieves a frequency variation of less than 600 kHz_p-p over a temperature range of -20° to +60°C     

Submicron AlGaN/GaN HEMTs with very high drain current density grown by plasma-assisted MBE on 6H-SiC

High electron mobility transistors (HEMTs) were fabricated from AlGaN/-GaN layers grown by plasma-assisted molecular beam epitaxy on semi-insulating 6H-SiC substrates. Room-temperature Hall effect measurements yielded a polarization-induced 2DEG sheet charge of 1.3/spl middot/10/sup 13/ cm/sup -2/ and a low-field mobility of 1300 cm/sup 2//V/spl middot/s. Submicron gates were defined with electron beam lithography using an optimized two-layer resist scheme. HEMT devices repeatedly yielded drain current densities up to 1798 mA/mm, and a maximum transconductance of 193 mS/mm. This is the highest drain current density in any AlGaN-GaN HEMT structure delivering significant microwave power reported thus far. Small-signal testing of 50-/spl mu/m wide devices revealed a current gain cutoff frequency f/sub T/ of 52 GHz, and a maximum frequency of oscillation f/sub max/ of 109 GHz. Output power densities of 5 W/mm at 2 GHz, and 4.9 W/mm at 7 GHz were recorded from 200-/spl mu/m wide unpassivated HEMTs with a load-pull setup under optimum matching conditions in class A device operation.     

A wide-band microwave photonic phase and frequency shifter

Advanced radar deception systems require wide-band devices which perform microwave processing of frequency and phase information. A wide-band microwave photonic phase shifter was constructed which is capable of imposing greater than 2π phase shift to microwave signals in the 2-18-GHz frequency range. The maximum standard deviation from the phase setting was 10° (7° typical). The phase shifter was then incorporated into a frequency translation architecture. The carrier suppression obtained was 50 dB with a spurious harmonic suppression of 23 dB     

Mode competition in Bragg resonator cyclotron resonance maser experiments driven by a microsecond,intense electron beam accelerator

We report an experimental study on mode competition in a high-g Bragg resonator cyclotron resonance maser (CRM) employing a microsecond, relativistic electron beam. The high quality annular electron beam of 20-80 A was produced through an apertured mask-anode. The high-Q Bragg resonator was designed to excite the TE₃₁, mode CARM oscillation at 18-9GHz. Two configurations of Bragg resonators were used; with ripples half inward and with ripples fully outward with respect to a smooth tubular centre section. Bragg resonator microwave emission was compared to radiation emitted when the electron beam interacted with smooth tubes with the same diameter as the Bragg resonator centre sections. In the present Bragg resonator CRM experiments, three parasitic oscillations were the most serious competing modes, apparently suppressing the TE31 CARM oscillation: TE₂₁, absolute instability, TE₁₁ gyro-BWO, second and third harmonic TE₅₁, mode. When a high current annular beam of 150-200 A was injected into the Bragg resonator, we observed the TE₂₁ absolute instability at B≥6-9kG, and a TE₁₁ gyro-BWO interaction at B≤5-2kG. Experimental evidence on the modes of the absolute instabilities were provided by gas breakdown patterns in fluorescent light tubes and frequency measurements.     

Radiation spectrum of a relativistic plasma microwave amplifier

A relativistic plasma microwave amplifier at a frequency of 3.2 GHz is experimentally studied. It is demonstrated that a relatively strong modulation of the electron beam in the presence of the electric field of an external microwave source leads to the termination of generation that is observed in the absence of the external signal. Thus, the microwave radiation with the above frequency and a power of 60 MW is generated at a high gain of 32 dB, a relatively low noise level, and the fixed phase difference of the input and output microwave signals.     

基于光电振荡器的光脉冲和电微波信号发生器

设计了一种基于相位调制器的用于产生光脉冲和电微波信号的光电振荡器。该方案采用直调激光器配合相位调制器产生大啁啾并由DCF压窄输出光脉冲。利用偏振分束器和合束器在不增加有源器件的基础上形成双环路结构抑制微波信号的边模。该系统可以产生9.8 GHz的重复频率,脉宽小于 12 ps的光脉冲同时输出该频率的电微波信号。测得相位噪声为-105 dBc/Hz@10 kHz,Q值大于10¹⁰。     

一种新颖的具有HEMT和GaAs MMIC的Ku波段低噪声放大器

本文介绍了一种具有高电子迁移率晶体管(HEMT)和砷化镓单片微波集成电路(GaAs MMIC)的Ku波段低噪声放大器。在11.7～12.2GHz频率范围内,该放大器的噪声系数小于1.9dB,相关增益大于27dB,输入和输出驻波比小于1.4。放大器第一级采用了HEMT和微波串联电感反馈技术,放大器未级采用了Ku波段GsAs MMIC。设计的关键是采用微波串联电感反馈方法同时获得最佳噪声和最小输入驻波匹配。放大器的输入端和输出端均为BJ-120波导。     

The traveling-wave phototube part I: Theoretical analysis

The traveling-wave phototube (TWP) is a broad-band photodetector which is useful for demodulation of light that has been amplitude-modulated at a microwave frequency, and for optical heterodyning of coherent light signals with microwave difference frequencies. In either application the light beam(s) results in the emission of a current-modulated electron beam from a photocathode; interaction between this beam and a slow-wave circuit such as a helix is employed for broad-band detection of the microwave modulation. Part I of this paper presents a detailed analysis of the TWP beam-circuit interaction process, including the effects of loss, space charge and asynchronism. Computer results are given for both current modulation and velocity modulation excitations, since the latter can be important under certain operating conditions. Conclusions regarding the effects of beam current, circuit length and circuit loss are drawn which are important in the design, understanding and use of TWP's. The results of this analysis are also generally applicable to other cases where a slow-wave circuit is excited by an electron beam. In Part II of this paper, a detailed experimental analysis of the TWP will show good agreement with the predictions of this theoretical treatment.     

A microwave power double-heterojunction high electron mobility transistor

A microwave power high electron mobility transistor (HEMT) has been developed and tested in theK-band frequency range. The HEMT has a unique configuration of a selectively low-doped (AlGa)As/GaAs/(AlGa)As double heterojunction resulting in both capability of high-current density and high gate breakdown voltage. The structure showed electron mobility of 6800 cm²/V.s and two-dimensional (2-D) electron density as high as 1.2 × 10¹²cm^-2at room temperature. An output power of 660 mW (550 mW/mm) with 3.2-dB gain and 19.3-percent power added efficiency was achieved at 20 GHz with 1-µm gate length and 1.2-mm gate periphery. A similar device with 2.4-mm gate width produced an output power of 1 W with 3-dB gain and 15.5-percent efficiency. These results offer microwave high power capability in a double-heterojunction HEMT (DH-HEMT).     

X波段同轴多注相对论速调管放大器模拟研究

 设计了工作在X波段的同轴多注相对论速调管放大器,建立了带输入、输出波导结构的三维整管模型,采用三维电磁粒子模拟软件对其高频特性进行了优化设计,对电子束经过输入腔后的束流调制、注入微波吸收情况、中间腔对束流的调制以及输出腔的微波提取情况进行了模拟研究.在输入微波功率为70kW,电子束束压为600kV,束流为5kA,轴向引导磁感应强度为0.6T的条件下,输出微波功率达到了1.3GW,效率为43%,增益为42dB,在较低的输入微波功率和较小的轴向引导磁感应强度的情况下,模拟实现了X波段RKAGW级的微波功率输出.     

Frequency selective limiters for high dynamic range microwavereceivers

A broadband frequency selective limiter (FSL) which provides over 14 dB of limiting across more than an octave bandwidth is described. The limiter is fabricated with epitaxially grown YIG (yttrium iron garnet) films in a stripline configuration and has a threshold power level of below 0 dBm. Individual limiter strips limit microwave signals in the 1-100-mW range across more than an octave of bandwidth. Multiple FSLs have been cascaded with amplifiers to allow compression of microwave signals with a power range of 60 dB into a range of less than 5 dB     

A NOVEL Ku-BAND LOW NOISE AMPLIFIER WITH HEMT AND GaAs MMIC

A novel Ku-band low noise amplifier with a high electron mobility transistor (HEMT)and a GaAs monolithic microwave integrated circuit (MMIC) has been demonstrated. Its noisefigure is less-than 1.9dB with an associated gain larger than 27dB and an input/output VSWRless than 1.4 in the frequency range of 11.7-12.2GHz. The HEMT and the microwave series in-ductance feedback technique are used in the first stage of the amplifier, and a Ku-band MMIC isemployed in the last stage. The key to this design is to achieve an optimum noise match and a min-imum input VSWR matching simultaneously by using the microwave series inductance feedbackmethod. The B J-120 waveguides are used in both input and output of the amplifier.     

110 GHz gyrotron with a built-in high-efficiency converter

A 110 GHz 1 MW pulse gyrotron has been elaborated. A built-in electrodynamic duct consisting of a new type quasi-optical converter and three matching mirrors transforms operating mode TE_15,4 into a gaussian beam going through the output window. The efficiency of the duct (ratio of the gaussian beam power outside the gyrotron to the total microwave power at the output of the cavity) is about 95%. A system consisting of the gyrotron and an outer mirror transmission line is proved to have efficiency (ratio of the microwave power measured by calorimeter at the end of line to the power of the electron beam) more than 40%.