CW measurement of HBT thermal resistance

Measurements of the temperature dependence of β and V_BE were made on AlGaAs-GaAs HBTs and used to determine device thermal resistance. The measurements were CW and not switched or pulsed in order to have a simpler procedure. With base doping greater than 10¹⁹ cm^-3, HBTs have negligible base-width modulation (i.e., flat I_C versus V_CE characteristics) which makes CW thermal resistance measurement especially direct and simple     

A method of the measurement of moisture in IC packages using microwaves

A new method to measure the moisture content of integrated circuit (IC) packages is demonstrated. The moisture contained in the encapsulant resin was determined by using microwaves. The microwave signal was transmitted into the encapsulant resin and reflected at the surface of the chip pad. The amplitude and phase of the reflection coefficient of the microwave signal, which varied with the moisture content of the encapsulant resin, were measured in order to determine the moisture content. A preliminary experiment was carried out, and the calibration equation was developed. The present technique indicates the possibility of determining the moisture content directly without drying and weighing IC packages.     

Microwave attenuation at 35.8 GHz due to rainfall

A short double-pass microwave link at 35.8 GHz has been used, with four rapid-response rain gauges, to measure excess attenuation from rain as a function of mean rainfall rate along the path. The results are in good agreement with theoretical predictions.     

Frequency and polarisation scaling of microwave attenuation during rainfall

Measurements are presented from eastern Canada of the polarisation-dependent ratio of microwave attenuation due to rainfall for vertical and horizontal linear polarisations, and of the frequency-dependent ratio of attenuation for a given polarisation. The exponent of the usual power law of frequency scaling of attenuation is 1.93±0.15 (SD) in the 11?17 GHz frequency range.     

Measurements of rainfall attenuation at 8 and 15 GHz

Measurements of attenuation at frequencies of 8 and 15 GHz, and their correlation with rainfall rate, along a 15.78 km path near Ottawa, are described. Empirical expressions which relate the observed attenuation to the measured rainfall rate are derived and compared with similar expressions obtained on the basis of earlier theoretical studies of the problem. It is concluded that while the theoretical predictions of attenuation in rain are reasonably satisfactory, at least for rains observed at Ottawa, there is a definite tendency for observed attenuations at low rainfall rates to be somewhat higher than the expected values. The cumulative distribution of rainfall attenuation over a six-month period is compared with the attenuation predicted on the basis of average rainfall data obtained during the last five years. Although the agreement between observation and prediction, using the theoretical relation between rainfall rate and attenuation, is good for path attenuations greater than 2 dB, it can be greatly improved if the empirical expression relating rainfall rate to attenuation is used.     

一种新的精确测试光纤衰减方法的探讨

在分析了光纤的衰减现有的三种测试方法的基础上,提出了一种新的测量方法,此方法消除了由测量方法设计而带来的光纤链路总衰减测量误差,极大地提高了测试精确度。     

Spatial correlation coefficients of rainfall intensity inferred from statistics of rainfall intensity and rain attenuation

On the basis of the reliable statistics of rainfall rate and rainfall attenuation for 8 localities in Europe, the spatial correlation coefficient of point rainfall intensity was inferred for each locality from the cumulative distributions of attenuation and rainfall intensity by inversely applying the modified Morita and Higuti rainfall attenuation prediction method. It was found that for European regions the spatial correlation coefficient with an exponential dependence on the horizontal distance is more appropriate for the prediction of rainfall attenuation than that proposed by Morita and Higuti for the Japanese climate. It was also found that although the spatial correlation characteristic varies significantly from one locality to another its variance is not so significant within a particular ccir rainfall climatic zone. This suggests that in predicting the rainfall attenuation it is desirable to employ the spatial correlation coefficient appropriate for the locality to be estimated.     

连续波HF化学激光器小信号增益的测量

描述了测量连续波HF化学激光器小信号增益空间分布的装置。给出了CL—9喷管的几个跃迁增益分布的测量结果并对实验结果及误差作了简单讨论。     

Laser-beam attenuation measurement using acousto-optic modulator

A laser-beam attenuation-measurement method using the first-order diffraction from an acousto-optic modulator is newly developed. The attenuation is determined from the voltage of the 30 MHz driving signal of the modulator. A value of attenuation of more than 50 dB can be measured at 633 nm.     

Self-consistency of polarization diversity measurement of rainfall

Polarization diversity measurements of rainfall, namely the reflectivity factor, differential reflectivity, and specific differential propagation phase, vary in a constrained three-dimensional space. Algorithms are derived to quantify this self-consistency of measurements. In particular, estimation of the specific differential propagation phase shift based on reflectivity and differential reflectivity is analyzed in detail. Theoretical simulation as well as radar observations of rainfall at S (CSU-CHILL) and C (Polar 55C) bands are used to demonstrate that the range profiles of differential propagation shift can be constructed from measurements of reflectivity and differential reflectivity     

Continuous measurement of optical-fibre attenuation during manufacture

An online method of continuously monitoring the attenuation of an optical fibre during its manufacture is described. It provides a complete attenuation/length profile of the fibre. The present system can measure an overall attenuation of 30 dB, and the results agree with corresponding offline differential measurements to better than ± 1 dB/km.     

基于非球形雨滴的降雨对激光传输衰减的影响

为了进一步确定降雨对激光在大气中传输衰减的影响,将雨滴的非球形效应考虑在内,在雨滴的近似椭球模型、归一化谱分布的基础上,利用射线追踪法计算群雨滴在可见光和近红外波段的散射和衰减特性,讨论分析雨滴谱分布和降雨强度对可见光和近红外波段激光传输衰减的影响。数值模拟结果表明,不同谱分布的群雨滴散射能力从大到小依次为JD、MP、Gamma和JT分布;激光衰减不仅受降雨强度的影响,也与雨滴的数密度有关,数密度越大,激光衰减越大;而形状对群雨滴的影响较小。所得出的结论有助于准确评估降雨对激光传输的影响以及改善激光传输、通信和激光测风等应用。     

Lack of microbial genetic response to 2.45-GHz CW and 8.5- to 9.6-GHz pulsed microwaves.

Strain D4 of the yeast Saccharomyces cerevisiae, and strains TA-1535, TA-100 and TA-98 of the bacterium Salmonella typhimurium, were exposed to 2.45-GHz continuous wave or 8.5- to 9.6-GHz pulsed electromagnetic radiation (EMR) at various power densities from 1 to 45 mW/cm2. The temperature during radiation was maintained at 30 degrees C for yeast cultures and at 37 degrees C for bacterial cultures. The studies revealed no increase in mutations or of mitotic gene conversions when cells were radiated for two hours or less. Decreased viability of cells was noted in all cultures tested after radiation at power densities of 30 mW/cm2 or more; however, no reliable changes in genetic events occurred.     

SAW attenuation measurement in the acoustic microscope

A direct method for measuring surface-acoustic-wave attenuation using the scanning acoustic microscope is presented. The use of an annular lens excludes the longitudinal wave component from a normal V(z) measurement, and so an interference-free measurement of surface-wave attenuation alone is possible. Simple corrections compensate for both absorption in the coupling fluid as well as variations in the critical angle.     

The influence of heavy rainfall on attenuation at 18.5 and 30.9 GHz

Percent-of-time distributions of rain-induced fades obtained on a 6.4-km path in New Jersey operating at a frequency of 18.5 GHz are discussed for the period of 1968-1969; data obtained at 30.9 GHz on a 1.9-km path for the same period are also discussed. The attenuation distributions are compared with attenuations calculated from the distributions of average rain rates on the paths. With these data, it is found that distributions of attenuation can be predicted from the path-average rain-rate distributions for a given sample period. Detailed rain-rate and attenuation measurements at 18.5 GHz on the 6.4-km path are presented for the most intense storm observed in a three year recording period. Point rain rates in excess of 250 mm/h and path-average rates exceeding 180 mm/h were observed; the attenuation exceeded the 50-dB dynamic measuring range of the equipment for more than seven minutes.     

雨衰减预测中的降雨率调整因子概念

利用ITUR数据库地面视距链路和地空链路雨衰减数据,分析了传统雨衰减预报中所使用的基于柱状雨胞模型的雨衰减物理模型导出的路径调整因子与实测数据之间的矛盾.在此基础上,基于指数雨胞建立的雨衰减物理模型,通过理论分析导出了降雨率调整因子的概念.利用降雨率调整因子,可以解释实测数据的主要特征,表明：基于指数雨胞的雨衰减物理模型是合理的,利用降雨率调整因子的概念,可为发展新的地面视距链路和地空链路雨衰减预报模式和方法提供理论依据.     

Analysis of SAW attenuation measurement using acoustic microscopy

Effect of acoustic loss in solids on depths of dips in V(z) curves obtained by reflection acoustic microscopy was calculated. The results were in good agreement with the observed V(z) curves of steels. The applicability and limitations of measuring attenuation of surface acoustic waves from V(z) curves are discussed.     

腔长变化对连续波腔衰荡技术测量的影响

为了阐明腔长变化对测量的影响,在考虑入射光源光谱线宽的情况下,采用腔衰荡法和多光束干涉等有关理论,就两种极限情况下腔长变化对连续波腔衰荡法测量的影响进行了分析和数值模拟,并据此讨论了一般情况下腔长变化给测量带来的影响。分析表明,腔长变化主要使衰荡腔谐振频率变得不稳定,从而使得衰荡腔出射光功率及其衰荡特征发生变化,进而给测量带来严重误差,这将为分析该技术测量误差来源以及提高其测量精度提供理论指导。     

连续和脉冲CO2激光器频率稳定度的测量

采用拍频法测量CO2激光器频率稳定度。计算机通过IEEE488接口直接从计数器上接收数据,并通过程序计算得出激光器的频率稳定度。采用脉冲外差法测量脉冲CO2激光器频率稳定度。