High-Frequency Gunn Oscillators (Short Papers)

Recent work to achieve high output power of fundamental mode Gunn-effect oscillators at frequencies ranging from 25 to 71 GHz is described. Ambient powers of 370 mW at 6.7-percent efficiency at 25 GHz, 260 mW at 4.5-percent efficiency at 38 GHz 150 mW at 4-percent efficiency at 54 GHz, and 30 mW at 1-percent efficiency at 71 GHz were obtained from single-diode structures. Combining two diodes in a push-pull circuit yielded 400 mW at 3.5-percent efficiency at 32 GHz and 260 mW at 4.0-percent efficiency at 42 GHz. This represents some of the highest powers and efficiencies reported to date from millimeter-wave Gunn-effect oscillators.     

Rain Attenuation Statistics from a 19 and 28 GHz COMSTAR Beacon Propagation Experiment: One Year Cumulative Distributions and Relationships Between the Two Frequencies

Cumulative attenuation distributions for one year and relationships between attenuations at 19 GHz and 28 GHz are presented for an earth-space propagation path terminating at Crawford Hill, New Jersey. An example from the distributions indicates that 20 dB attenuation was exceeded for 0.012% of the year at 19.04 GHz and for 0.06% at 28.56 GHz. For both frequencies the polarization was linear and oriented 21° from vertical at the receiver. When the attenuation at 19 GHz was less than 20 dB, the attenuation in dB at 28 GHz averaged 2.1 times that at 19 GHz. This ratio was lower at higher attenuations.     

Free space video detection of harmonic content of 100 GHz IMPATT oscillator

The harmonic content of a commercial c.w. 20 mW 100 GHz IMPATT oscillator operating at ambient temperature has been determined at 200 and 300 GHz using free space techniques. The highest power levels observed at these frequencies were 16.6 and 37.5 dB below the fundamental, respectively, corresponding to power levels of 0.5 mW at 200 GHz and 4.5 ?W at 300 GHz at the oscillator.     

不同剂量率下偏置对双极晶体管电离辐照效应的影响

对双极晶体管进行了不同剂量率、不同偏置的电离辐照实验。结果表明，对于不同偏置条件，晶体管在低剂量率辐照下，电流增益都有更为明显的衰降；各种剂量率辐照下，电流增益在发射结反向偏置时比浮空偏置时有更为显著的下降。文章对相关机理进行了探讨。     

A 10-GHz frequency divider using selectively doped heterostructure transistors

We report the first complementary clocked frequency divider using dual gate selectively doped heterostructure transistors (SDHT's). The circuit employs a master-slave flip-flop design which consists of four direct coupled AND-NOR gates. The nominal gate length and the gate-gate, separation in the dual gate SDHT's are 1 µm. A maximum dividing frequency of 10.1 GHz at 77 K was achieved; at this frequency the circuit dissipated 49.9 mW at 1.67-V bias. This is the highest operating frequency reported for static frequency dividers at any temperature. At room temperature the dividers were operated successfully at frequencies up to 5.5 GHz with a total power dissipation of 34.8 mW at 1.97-V bias. The lowest speed-power product at room temperature was obtained at 5 GHz with 14.9-mW power dissipation at 1.45-V bias.     

A unique method for reducing losses of bends in dielectric optical wave guide

The dielectric optical wave guide is finding growing attention at millimeter wave frequencies. However the dielectric optical waveguide radiates at bends and thus transmission loss increases. These radiations are in the outword direction of bends. This output radiation at output bends arises due to change in phase velocities of the propagating wave at the centre of the dielectric guide and the phase velocity at the outer surface of the dielectric guide. A unique methiod is suggested to avoid these radiation losses.Experimental results are also shown at microwave frequencies.     

Phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the sn-rich corner

Knowledge of phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the Sn-rich corner is important for the understanding of the interfacial reactions at the Sn-Ag-Cu/Ni contacts, which are frequently encountered in recent microelectronic products. Various Sn-Ag-Cu-Ni alloys were prepared and equilibrated at 250°C. The alloys were then quenched and analyzed. The phases were determined by metallography, compositional analysis, and x-ray diffraction (XRD) analysis. No quaternary phases were found. The isoplethal sections at 60at.%Sn, 70at.%Sn, 80at.%Sn, and 90at.%Sn at 250°C are determined. The phase equilibrium relationship was proposed based on the quaternary experimental results and the 250°C isothermal sections of the four constituent ternary systems, Sn-Ag-Cu, Sn-Ag-Ni, Sn-Cu-Ni, and Cu-Ag-Ni. Because there are no ternary phases in all these three systems, all the compounds are in fact binary compounds with various solubilities of the other two elements.     

Prediction methods for rain attenuation statistics at variable path angles and carrier frequencies between 13 and 100 Ghz

Fade depth and space diversity statistics of propagation along earth-satellite paths have been calculated from radar reflectivity data of rain using modeling procedures. The reflectivity data base was obtained during the summer of 1973 at Wallops Island, Va., using a high resolutionSband radar interfaced with a computer and digital processing system. Fade statistics have been calculated for various path angles at several frequencies between 13 and 100 GHz. Subsequent analysis has demonstrated the ability to predict the following: 1) fade statistics at other path elevation angles given similar type statistics at a particular path angle, 2) space diversity statistics at other frequencies, given similar type statistics at a particular frequency, and 3) fade statistics at a third frequency given similar type statistics at two other frequencies. Although a specific data base was used pertaining to the climatology at Wallops Island, the techniques developed are general and may be applied to existing or future "fade measurements" at other climatological locations.     

CORRUGATED CONICAL HORN FOR MULTI-FREQUENCY BAND USE

The theory of corrugated conical horn operating at multi-frequency bands is described,and aprqactical corrugated conical horn is constructed.It can operate at three frequency bands(4,6,11 GHz)atleast.The cross polarization peak level is better than -25 dB at 4,6 GHz frequency bands,and the amplitudepattern at 11 GHz frequency band is also very good.It is shown theoretically and experimentally that thecorrugated conical horn operating at multi-frequency bands is the best condidate for multi-frequency bandfeeds.     

大功率LED在线性及PWM调光下的电光转换效率及热分析

在相同输入电功率下,对大功率LED在线性及PWM两种调光模式下的光参数及电参数进行了测试。比较了LED在两种调光模式下的色温、光效及电光转换效率随输入功率的变化,得出在两种调光模式下,色温随平均输入电流的降低而降低,但线性调光模式下的色温漂移大于PWM调光模式下的色温漂移;光效及电光转换效率随平均输入电流的降低而升高,但在相同输入功率下,LED在PWM调光模式下的电光转换效率大于线性调光模式下的电光转换效率,且随平均输入电流的降低,线性调光模式下的电光转换效率的上升速度要快于PWM调光模式。利用T3STER热阻测试仪,建立LED的瞬态热阻抗模型。使用电子学热仿真分析方法对LED在两种调光模式下的电光转换效率随结温变化的规律进行了仿真分析。分析得出LED在PWM调光下的光电转换效率主要受结温温升的影响,而在线性调光下,电光转换效率除了受到结温温升的影响,还受到无效电流注入的影响。因此,LED在线性调光模式下电光转换效率的上升速度要快于PWM调光模式。     

CaF_2/Si(111)界面的电子结构和化学键(英文)

CaF_2/Si(111) interfaces formed at 700℃ as well as at room temperature have been studied with XPS, UPS and LEED. The experimental results show that the substrate temperature has a significant influence on the interface in respect of ifs electronic structure and chemical bond. When the substrate temperature was at 700℃, the interface is found to be consisted of predominate Si-Ca bonds which correspond to an interface state located at 1.2eV below Fermi level. There is depletion of fluorine atoms due to the dissociation of the CaF2 molecule at the interface. When the substrate was at room temperature, there are no chemical bonds between substrate and adatoms nor depletion of fluorine atoms at the interface. Annealing of this interface at 700℃ results in preferential evaporation of F, and the surface undergoes a number of reconstructions until a 3×1 reconstruction is obtained. The bonding at this interface is similar to that of CaF2/Si(111) interface when the substrate temperature was at 700℃.     

城市对流层气溶胶观测分析与研究

利用激光雷达测量数据反演出了北京测站和西藏那曲测站上空对流层大气气溶胶散射比和消光系数的垂直分布,利用消光系数和风速数据,进行了相关分析。结果表明,北京测站上空气溶胶的组分、浓度、粒径和分布较那曲呈现更大的不均匀性;西藏那曲地区的空气质量较北京城区要高;那曲测站上空的贴地层高度较北京城区低;北京测站近地面气溶胶消光系数和风速的负相关特性较为明显。     

High-intensity terahertz pulses at 1-kHz repetition rate

We report the generation of terahertz pulses with 0.4-μJ pulse energy at 1-kHz repetition rate using a large-aperture GaAs photoconductor with 3-cm gap aluminum electrodes, biased at voltages up to 45 kV. The terahertz output energy saturates at a laser fluence of 40 μJ/cm² at low-bias fields, while no clear saturation point was observed at high-bias fields. The output was found to be dependent on the repetition rate: at high fluences, pulse energy at 1 kHz is higher than that at 100 Hz by as much as 60%. A study of the behavior of the terahertz pulse energy and pulsewidth as a function of the pulsewidth of the laser excitation was conducted and compared with theoretical predictions. Propagation properties of the terahertz beam were also characterized, leading to a focal spot size as small as 800 μm at the focus of a 2.5-in focal length parabolic mirror     

Low-Voltage and High-Speed Operations of 30-nm-Gate Pseudomorphic $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}/hbox{In}_{0.7}hbox{Ga}_{0.3} hbox{As}$ HEMTs Under Cryogenic Conditions

In this letter, we fabricated 30-nm-gate pseudomorphic In_0.52 Al_0.48As/In_0.7Ga_0.3As HEMTs with multilayer cap structures to reduce source and drain parasitic resistances; we measured their dc and radio-frequency characteristics at 300, 77, and 16 K under various bias conditions. The maximum cutoff frequency fT was 498 GHz at 300 K and 577 GHz at 77 K. The maximum fT exceeded 600 GHz at 16 K. Even at a drain-source voltage V _ds of 0.4 V, we obtained an fT of 500 GHz at 16 K. This indicates that cryogenic HEMTs are favorable for low-voltage and high-speed operations. Furthermore, the present 30-nm-gate HEMTs at 300 K show almost the same fT values at the same dc-power dissipation as compared to 85-nm-gate InSb-channel HEMTs. The improvement of the maximum-oscillation-frequency f _max values was also observed at 77 and 16 K.     

Laboratory measurements of the 36 GHz backscattering cross sectionfrom water waves

The backscattering cross section per unit area σ₀ of a roughened water surface at 36 GHz is needed in the development of new remote sensing instrumentation that will operate at this frequency. One instrument, the multimode airborne radar altimeter (MARA), will illuminate the surface at incidence angles ranging from nadir to 12° off-nadir. Laboratory tests were performed at the Wallops Wind-Wave Tank Facility to determine the variability of σ₀ at these angles and as a function of windspeed. The measurement procedures used in a 6-in.-diam aluminum sphere as the calibration source. The results are compared with earlier measurements at this frequency. Little variability with windspeed was found in the cross-section values for 12° off-nadir, while the cross section decreased with windspeed at nadir. The nadir cross section exceeded the off-nadir result by about 7 dB at a windspeed of 10 m/s (at a 10-m effective height above sea level)     

Low frequency noise in MOST's at cryogenic temperatures

Noise measurements in the audio frequency range showed that p-channel MOST's, working at 4°K, had lower noise levels than at room temperature, though the levels at 77°K were very much lower. 1/ƒ^a noise was observed where a is 1.0 or 1.2 at room temperature and is 0.8 at lower temperatures and slightly frequency dependent. Measurements of noise versus quiescent point revealed that at 77°K a noise process not involving modulation of channel conductivity was present in some cases. Noise in the presence of trapping is a possible explanation of results at 4°K.     

Second breakdown of IC structured power transistors

The authors attempt to characterize second breakdown as heating phenomena which can occur in one of two places, either at the p-n interface at low current or at the n-n⁺interface at higher current. The transition point between these two states occurs at a current It= qVsatNDS where the n-region field is uniform and at a voltage Vt= εsatWepijust necessary to saturate the drift velocity in Wepi.     

Reflector efficiency evaluation by frequency scaling

In recent evaluations of large parabolic reflector antennas, engineers have investigated the antenna performance at several frequencies. In this paper it is shown that the efficiency at any frequency can be estimated from a measured efficiency at another frequency and a carefully calculated design efficiency. In practice, an efficiency measurement at some frequency usually serves to determine the efficiency at all lower frequencies.     

多频段共用的波纹圆锥喇叭

本文阐述了波纹圆锥喇叭的多频段工作原理,并介绍了一个至少能在4,6和11 GHz三个频段共用的波纹圆锥喇叭。此喇叭在4,6 GHz频段的交叉极化峰值优于-25dB,在11GHz频段的幅度方向图性能优良。理论和实践表明,使用不止在一个工作区工作的波纹圆锥喇叭可以实现多频段共用的馈源喇叭。     

用三点弯方法研究微氮硅单晶机械强度

通过三点弯方法研究普通和微氮硅单晶在室温下的机械强度 ,以及它们的高温抗弯强度 .实验发现 ,由于氮的掺入 ,硅片室温下的机械强度有明显的改善 ,同时证实了高温下氮对位错的钉扎作用 ;研究还指出 ,硅片表面状态和晶向对室温时机械强度也存在影响 .对室温下氮杂质增强机械强度的可能机理进行了探讨