Frequency synthesizers up to 370 GHz

A new generation of frequency synthesizers up to 370 GHz is described. The main parts of them are microwave frequency synthesizer covering 11–15 GHz band, effective frequency multipliers-mixers using an opposite pair of planar Shottky diodes and a lock-in loop of a backward-wave oscillator tube covering millimeter and longer part of submillimeter wave bands with tens of milliwatts of output power. The ways of further increase in the operating frequency of such synthesizers are discussed.     

Polarization properties of some materials at near millimeter wavelengths

The degree of polarization of some materials widely used as optical components in the submillimeter and millimeter region has been measured in the wavelength interval 0.5÷3 mm. The procedure used in the measurements allows to determine degress of polarization of the order of 10^–5.     

Measurments of attenuation and refractive dispersion due to atmospheric water vapor at 80 and 240 GHz

Field line-of-sight propagation experiments were made at 80 and 240 GHz on a horizontal path of 810 m. The measured attenuations showed quadratic dependences on atmospheric water vapor density, and absorptions in excess of theoretical predictions were observed at both frequencies, while the measured refractive dispersion between these two frequencies showed a linear dependence on water vapor density and was in good agreement with theoretical prediction. Liebe's model for water vapor attenuation including empirical continuum absorption is confirmed to be effective for 80 and 240 GHz.     

Application of multilayer structures at millimeter wavelengths

The paper presents results of theoretical analyses and experimental investigations of the optical characteristics of devices based on multilayer dielectric structures and intended for the millimeter wave band. As is shown, multilayer dielectric structures can prove useful in devices with variable optical characteristics representing coupling elements for quasioptical open resonators, adjustable reflection coefficient mirrors in narrow-band interference Fabry-Perot filters or adjustable multilayer polarizers.     

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.     

Detection of Target Embedded in Sea Clutter by Means of Millimeter Wave Radar

Sea clutter was measured using a millimeter wave radar with a frequency of 34.86GHz and pulse length of 30ns. A car carrier ship target was embedded in sea clutter. It has been discovered that target pulse-to-pulse fluctuations obey a Weibull distribution and sea clutter obey a Rayleigh distribution. We obtained target to clutter ratio improvement of 23.8dB by applying the cell average LOG/CFAR techniques. The computer simulation has been made to evaluate the detection probability and the false alarm probability. The simulation result was in good agreement with the observed data.     

Amplitude Statistics of Sea-Ice Clutter Using a Millimeter Wave Radar

Sea-ice clutter was measured using a millimeter wave radar with frequency of 34.86GHz and pulse length of 30ns. To determine the sea-ice clutter amplitude statistics, we investigated the log-normal, Weibull, log-Weibull and K-distributions using the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least-squares method. It is shown that the amplitude of sea-ice clutter obeys almost a log-Weibull distribution.     

Measurement of permittivity of aqueous solutions at 44 GHz by FM receiver

An instrument using a variable-thickness waveguide cell has been developed for measurement of absolute complex permittivity at 44 GHz. The superheterodyne is used to rise the sensitivity. The results of measurements of water and saccharose aqueous solutions in the range of 15–27 °C are presented.     

Surface resistance measurements at 337 GHz

A high Q quasioptical hemispherical resonator, capable of making measurements on samples as small as 5 mm in diameter, was used to make surface resistance measurements at 337 GHz on samples of Al, Au, Mo, and Cu. Results for A1 agree with the low frequency approximation, the other metals are some what higher.     

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.     

半导体远红外反射镜中反射率和相位研究

以GaAs材料为例，研究了半导体远红外反射镜中的反射率和相位.通过拟合不同掺杂浓度下样品的远红外反射谱，得到了自由载流子的弛豫时间随掺杂浓度变化的经验公式，并把该规律应用到数值计算中.详细讨论了反射镜的结构和材料参数对反射率R和相位φ的影响.根据腔体内吸收率最高的判据得到了最优的反射镜的参数，并计算了这种优化后的反射镜的波长选择特性.最后，通过远红外反射光谱的测量，从实验上验证了这种反射镜的实际效果. 所得结论为半导体远红外器件中的反射镜设计提供了参考. 关键词： 远红外反射镜 反射率 相位     

Suppression of Sea-Ice Clutter Observed by a Millimeter Wave Radar Using a New Log-Weibull/CFAR System

Sea-ice clutter was measured using a millimeter wave radar with frequency of 34.860GHz, beamwidth of 0.25° and pulse length of 30ns. To determine the sea-ice clutter amplitude statistics, we investigated the log-normal, Weibull, log-Weibull and K-distributions using the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least-squares method. It is shown that the amplitude of sea-ice clutter obeys the log-Weibull distribution with shape parameters of 2.36 to 2.93 for both entire data and data within the beam width of an antenna. We propose a new log-Weibull/CFAR system uses a modified cell-averaging LOG/CFAR system. It is found that this log-Weibull/CFAR procedure is effective for suppression of sea-ice clutter and detection of target.     

Rain Attenuation at Millimeter Wavelengths

A method of determining the rationality for raindrop size distribution is first presented. The relative volume occupied by raindrops is derived. The attenuation and cross-polar discrimination induced by rainfall at millimeter waves are investigated with the incoming expression and a brief analysis is presented.     

Investigation of atmospheric emission and attenuation at wavelengths 2.07 and 3.34 mm

The results of processing the data of an annual cycle of synchronous measurements of the Earth's atmosphere emission in two transparency windows are reported.     

端面反射率的波长特性对外腔半导体激光器调谐范围的影响

端面镀增透膜的激光二极管构成的光栅外腔激光器（ECLD）中,考虑到镀膜端面剩余反射率对波长的依赖关系以后,利用等效腔法导出了该激光器阈值载流子密度随波长变化的解析表达式,以此为出发点,讨论了增透膜反射率极小位置对调谐范围的影响。结果表明,除了增大剩余反射率工和降低剩余反射率能够提高调谐范围这一明显结论这外,在镀膜工艺确定的情况下,即假定剩余反射率带宽和剩余反射率极小值变化不大时,通过控制剩余反射率极小值所对应的波长相对于镀膜前增益峰的偏移量,可进一步拓宽波长调谐范围。     

超高反射率的损耗比较测量法研究

描述了一种用两个激活谐振腔的损耗比较测量超高反射率的有效方法。其基本原理源于菲涅耳公式和布儒斯特定律。测量精度为±５．０×１０－５，并讨论了测量系统的若干问题。     

变反射率镜非稳腔的研究进展

回顾了变反射率镜非稳腔的研究历史,总结了实现变反射率的方法,分析了它们的优缺点,最后列表总结了典型使用VRM作为非稳腔输出耦合器的实验参数和结果.为大能量固体激光器的设计提供了理论和实验参考.     

周期性梯度折射率多层膜的软X射线反射率

由于界面互扩散的存在,实际的超薄多层膜很难具有清晰的界面结构.假设超薄多层膜为具有周期性梯度折射率的多层膜结构,用直线模型和余弦模型模拟了周期性梯度折射率多层膜的软X射线反射率.结果证明,折射率余弦渐变的多层膜虽然不具有清晰的界面,但它同样具有很高的反射率.     

70 GHz二次谐波倍频回旋速调管研究

 对70 GHz二次谐波倍频回旋速调管高频结构和电子与波互作用进行了研究。研究了TE02模腔体绕射品质因数及模式转化,解决了二次谐波倍频回旋速调管漂移段不能截止70 GHz的TE01模而引起的腔体间高频串扰的问题。分析了注电流、输入功率、电子横纵速度比和电子注引导中心半径等参数对输出功率、增益和效率的影响。针对二次谐波回旋速调管放大器工作频带窄、效率低,进行了高频结构优化设计,显著地展宽了工作频带,提高了互作用效率。在理论分析和高频计算的基础上,建立了注-波互作用PIC（粒子模拟）模型,进行了粒子模拟计算和优化,得到了70 GHz 的二次谐波倍频四腔回旋速调管放大器设计方案。粒子模拟结果表明：在工作电压70 kV,注电流13 A,电子注横向速度与纵向速度比为1.5时,中心频率69.81 GHz输出功率256 kW,带宽160 MHz,电子效率28%,饱和增益大于44 dB。