Reflectivity of some materials at 94 GHz

In order to better understand the characteristics of discrete natural land clutter at millimeter wavelengths, an experimental investigation of the relative reflectivity of various materials at 94 GHz was performed using a substitution technique. The data show that nonconducting materials have a relative reflectivity on the order of 2–3%, and that absorbed water can increase the relative reflectivity significantly.     

A multi-sample 94 GHz dissolution dynamic-nuclear-polarization system

We describe the design and initial performance results of a multi-sample dissolution dynamic-nuclear-polarization (DNP) polarizer based on a Helium-temperature NMR cryostat for use in a wide-bore NMR magnet with a room-temperature bore. The system is designed to accommodate up to six samples in a revolver-style sample changer that allows changing samples at liquid-Helium temperature and at pressures ranging from ambient pressure down to 1 mbar. The multi-sample setup is motivated by the desire to do repetitive in vivo measurements and to characterize the DNP process by investigating samples of different chemical composition. The system can be loaded with up to six samples simultaneously to reduce sample loading and unloading. Therefore, series of experiments can be carried out faster and more reliably. The DNP probe contains an oversized microwave cavity and includes EPR and NMR capabilities for monitoring the DNP process. In the solid state, DNP enhancements corresponding to ～45% polarization for [1-(13)C]pyruvic acid with a trityl radical have been measured. In the initial liquid-state acquisition experiments described here, the polarization was found to be ～13%, corresponding to an enhancement factor exceeding 16,000 relative to thermal polarization at 9.4 T and ambient temperature.     

Skin-effect analysis of a shielded polymer Y-fed coupler electro-optic modulator over a wide bandwidth of 94 GHz

A novel technique and related formulations are proposed for analyzing the influences of the skin-effect on the performances of a polymer Y-fed coupler electro-optic modulator with shielded push-pull micro-strip electrodes. Using the extended point-matching method, coupled mode theory and electro-optic modulation theory, thorough design and optimization are performed. By introducing the effective applied voltage, formulas of the high-frequency response under skin-effect are deduced, and characteristics under skin-effect are analyzed. Under the central wavelength of 1550 nm, the half-wave voltage is as low as 1.097 V for the device with an active region length about 8.884 mm. Considering the influences of the skin-effect, the 3-dB modulating bandwidth of the microwave signal is up to 94 GHz. A high extinction ratio of more than 20 dB and a low insertion loss of less than 4.18 dB are achieved when the microwave frequency is below 68 GHz under skin-effect. This design technique is proven to be accurate by the comparison with the beam propagation method (BPM).     

94GHz基波复合腔回旋管数值模拟

通过对94 GHz基波复合腔回旋管中谐振腔结构、电子注参数以及注-波互作用过程的模拟计算研究,分析了复合腔回旋管的高频结构特性和工作参数优化问题.给出了基波H61 -H62模式对复合腔回旋管的模拟设计结果.数值模拟结果表明:在电子注电压40 kV、电流5A、电子横纵速度比1.3、工作磁场3.6T时,回旋管可获得78 k...     

Terrain radiation: Measurement investigation at 94 GHz

Using the 94 GHz — radiometers situated on board of a helicopter and on a measuring tower, there were investigated radiating properties of various surface types of soil and sea under their different states and season-weather conditions. The measurements were accompanied with controlling biogeophysical parameters of the surfaces and atmosphere. The plotted dependencies and the interrelations noticed in the process of discussion of the results of our work may be used when working out and estimating efficiency of the operation algorithms of the systems providing remote sensing of the surround medium.     

Earth cover back scattering characteristics at the frequencies 94 GHz and 136 GHz

There are presented experimental investigations of interrelationships of wide-spread terrain-surface types with their biogeophysical parameters over the short millimeter wave range. Found angular, polarization and frequency dependencies, as well as the considered regularities may be useful when choosing apparatus parameters of remote-sensing systems, and also when working out and evaluating algorithms of their operation.     

Wideband chaos generation using a delayed oscillator and a two-dimensional nonlinearity induced by a quadrature phase-shift-keying electro-optic modulator

We present a new optoelectronic architecture intended for chaotic optical intensity generation. The principle relies on an electro-optic nonlinear delay dynamics, where the nonlinearity originates from an integrated four-wave optical interferometer, involving two independent electro-optic modulation inputs. Consequently, the setup involves both two-dimensional nonlinearity and dual-delay feedback dynamics, which results in enhanced chaos complexity of particular interest in chaos encryption schemes. The generated chaos observed with large feedback gains has a bandwidth ranging from 30 kHz to 13 GHz and is confirmed by numerical simulations of the proposed dynamical model and bifurcation diagram calculation.     

NRD leaky-wave antenna for narrow beams in 94GHz

Theoretical analyses and numerical results of NRD leaky-wave antenna are presented. The results show that the characteristics of frequency scanning and very narrow beam can be implemented by NRD leaky-wave antenna. At the freguency of 94GHz, the half-power beamwidth of 0.14° of the antenna canbe obtained when the length of the antenna is 1.5m. From 90 to 98GHz, frequency scanning is about ±7° relating to the beam angle at 94GHz. The theoretical results are compared with the experimental data.     

94 GHz回旋管准光模式变换器设计

基于几何光学理论和矢量绕射理论,研究了将回旋管及其他高功率微波器件的振荡输出模式转换成准光高斯波束的模式变换器,采用伏拉索夫(Vlasov)辐射器和三级准光反射面实现了准高斯模TEM₀₀的横向输出.研究了Vlasov辐射器的工作机理,运用矢量绕射理论计算出波导辐射场,口面电流分布的方法计算反射面辐射场.通过编写程序设计了将94 GHz,模式为TE₆₂的毫米波转化为准光高斯波束的内置式准光模式变换器. 关键词： 94 GHz回旋管 内置式准光模式变换器 Vlasov辐射器 矢量绕射理论     

Experimental demonstration of a W-band (94 GHz) gyrotwystronamplifier

A four section, TE₀₁ mode W-band gyrotwystron amplifier has been designed, built, and tested. The circuit consists of three cavities followed by a traveling wave output section, each operating near the fundamental cyclotron frequency. The gyrotwystron has produced 50 kW peak output power, corresponding to 17.5% efficiency for a 57 kV, 5 A electron beam; the amplifier is zero drive stable at the operating point. The measured center frequency is 93.9 GHz with a full width half maximum instantaneous bandwidth of 925 MHz. These results represent a substantial improvement in the power-bandwidth product over previously demonstrated gyro amplifiers in this band. The small signal and saturated gains were 39 and 30 dB, respectively. The measured results are in good agreement with theoretical predictions     

94 GHz的TE11-HE11模式变换器设计

基于模式匹配技术的迭代综合方法优化设计了94 GHz的TE11-HE11模式转换器。采用商用电磁仿真软件对设计的模式变换器的性能进行了验证,两者结果基本一致。在88~102 GHz的频带范围内,模式输出纯度超过98%,其中最大模式纯度为99.1%。设计的基于半径微扰的光滑壁圆波导结构的模式变换器结构简单,易于加工,同时避免了波纹模式变换器波纹间隔易发生击穿的弊端。     

94 GHz回旋管过模波导模式转换与传输

在耦合波理论的基础上,研究了94 GHz回旋管内置TE03-TE02-TE01模式转换器和外接的TE01-TE11模式转换器。采用半径渐变微扰和轴线微扰几何结构以及不同的相位重匹配技术进行优化分析,得到了可靠的最优几何参量,设计出了紧凑、高效的94 GHz波纹波导模式转换器和蛇形线模式转换器。回旋管的热测实验中测出的模式样图表明,所设计的内置模式变换器有效地实现了TE03-TE02-TE01的模式转换。     

94GHz的TE_(11)-HE_(11)模式变换器设计

基于模式匹配技术的迭代综合方法优化设计了94 GHz的TE11-HE11模式转换器。采用商用电磁仿真软件对设计的模式变换器的性能进行了验证,两者结果基本一致。在88~102 GHz的频带范围内,模式输出纯度超过98%,其中最大模式纯度为99.1%。设计的基于半径微扰的光滑壁圆波导结构的模式变换器结构简单,易于加工,同时避免了波纹模式变换器波纹间隔易发生击穿的弊端。     

94 GHz回旋管过模波导模式转换与传输

 在耦合波理论的基础上,研究了94 GHz回旋管内置TE₀₃-TE₀₂-TE₀₁模式转换器和外接的TE₀₁-TE₁₁模式转换器。采用半径渐变微扰和轴线微扰几何结构以及不同的相位重匹配技术进行优化分析,得到了可靠的最优几何参量,设计出了紧凑、高效的94 GHz波纹波导模式转换器和蛇形线模式转换器。回旋管的热测实验中测出的模式样图表明,所设计的内置模式变换器有效地实现了TE₀₃-TE₀₂-TE₀₁的模式转换。     

Optical intensity modulator using inverted slot line at 60GHz

Optical and Quantum Electronics - The inverted slot line (ISL) structure which has been proposed for millimetre wave LiNbO3 optical modulator is found to be very simple in structure, and is also...     

94 GHz渐变复合腔二次谐波回旋管的设计

根据注-波互作用自洽非线性理论,编写了分析渐变复合腔的计算程序,通过该程序,获得了工作模式对为TE021-TE031的注-波互作用腔体和相关电磁参量的优化结果。应用粒子模拟软件对设计的复合腔进行了模拟,模拟与数值计算结果基本一致。根据计算结果研制了二次谐波回旋管,在加速电压57.5 kV、电流10 A下,测得其工作频率为94 GHz,输出模式为TE01,峰值功率和效率分别为156 kW和27.1%。计算、模拟和实验结果基本一致。     

94GHz渐变复合腔二次谐波回旋管的设计

根据注-波互作用自洽非线性理论,编写了分析渐变复合腔的计算程序,通过该程序,获得了工作模式对为TE021-TE031的注-波互作用腔体和相关电磁参量的优化结果。应用粒子模拟软件对设计的复合腔进行了模拟,模拟与数值计算结果基本一致。根据计算结果研制了二次谐波回旋管,在加速电压57.5kV、电流10A下,测得其工作频率为94GHz,输出模式为TE01,峰值功率和效率分别为156kW和27.1%。计算、模拟和实验结果基本一致。     

94 GHz单阳极磁控注入式电子枪初始参数设计

根据94 GHz回旋振荡管对电子束的需求,在理论分析电子枪工作原理的基础上通过大量编程对94 GHz单阳极磁控注入式电子枪的一系列参数进行了初始设计, 基于粒子模拟软件CHIPIC开发了专门针对磁控注入式电子枪的计算模块并对其进行了数值模拟。模拟结果显示:该枪的电子束横纵速度比为1.42、速度零散为4.6%,符合回旋振荡管对电子注的要求。     

94 GHz单阳极磁控注入式电子枪初始参数设计

根据94 GHz回旋振荡管对电子束的需求,在理论分析电子枪工作原理的基础上通过大量编程对94 GHz单阳极磁控注入式电子枪的一系列参数进行了初始设计, 基于粒子模拟软件CHIPIC开发了专门针对磁控注入式电子枪的计算模块并对其进行了数值模拟。模拟结果显示：该枪的电子束横纵速度比为1.42、速度零散为4.6%,符合回旋振荡管对电子注的要求。     

Far-field pattern analysis of 94 GHz extended hemispherical lens monopulse antennas

In this paper, the far-field patterns are investigated for double-slot antenna array placed on extended hemispherical lenses. The radiation patterns of the extended hemispherical lens fed by single double-slot antenna or double-slot antenna array are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The computation results show that the sharp null of the difference pattern is below -37dB.