Combining the Effects of Rain-Induced Attenuation and Depolarization in Digital Satellite Systems

Rain depolarization causes crosstalk on a dual polarization communications link. The effects of depolarization can be expressed as a degradation of the carrier-to-noise ratio (CNR) which can then be combined with the rain-induced attenuation to yield an effective attenuation. The effective attenuation is computed for a hypothetical satellite link at 11, 14, 20, and 30 GHz. It is shown that at 20/ 30 GHz the increase in system margin required by dual polarized use is small.     

ATS-6 Technical Aspects of the Health/Education Telecommunications Experiment

The Health/Education Telecommunications (HET) Experiment involved six different experiments conducted under the auspices of the Department of Health, Education, and Welfare (HEW) with technical assistance from NASA. The HET Experiment on ATS-6 was operated and controlled from a network coordination center in Denver, Colo., which included a 4-and 6-GHz Earth station. The HET Experiment used remote Earth terminals with 3-m-diameter dishes having a 35 dB gain at 2.5 GHz. In addition, comprehensive terminals operating at both C-band and S-band were used for communications with Alaska. The total network involved a complex of satellite and land links at C-band, S-band, and very high frequency (VHF), using the ATS-1, ATS-3, and ATS-6 satellites. The network performance exceeded expectations with remote terminal operations exhibiting a peak-to-peak signal to weighted rms noise ratio of 49 dB at least 99 percent of the time. The remote site operators performed well and were well motivated although they had little previous technical experience.     

ETS-II Experiments Part I: Japan's First Geostationary Satellite

Engineering Test Satellite Type II (ETS-11) "Kiku-2" was launched on February 23, 1977, and positioned in geostationary orbit at 130°E on March 5. Propagation experiments have been carried out by using 3 coherent beacons at 1.7, 11.5, and 34.5 GHz on a 24 h/day basis from late in April. The project and related plans are outlined. The 4 papers which follow in this Transactions introduce the experimental system and preliminary results using data from May to November 1977.     

Interference experiments between fixed-satellite and terrestrialradio-relay services

To resolve interference problems between fixed-satellite and terrestrial radio relay services and expand coordination areas between the two services, theoretical and experimental studies were carried out. Theoretical D/U values calculation formulas between the two systems were derived, interference data from 4 GHz and 11 GHz band terrestrial radio-relay systems were obtained by a measuring system mounted on a vehicle. By comparing those results, it becomes clear that the ensemble interference reduction factors for 4 GHz and 11 GHz bands are around 20 dB, which is mixed values of attenuation and reflection from big buildings in urban areas     

Optimized RF test range for educational purposes

Both the design and construction of a composite scale airframe and the equipment for an anechoic test range plus the in-house production of absorptive wall covering-all for engineering education-are briefly described. It is shown, that low cost home-made absorbing material with an attenuation of 30 dB or more can be designed. Waveguide and ground plane antennas for test purposes can be constructed from surplus materials. In this case the design and measurements of a 3 GHz antenna pair are shown. Finally, as a test object, a cheap yet effective scale model of a modern fighter aircraft is used for measurements of radar cross section and antenna installations. As a demonstration of the total system capabilities, the measurement of installed F-18 antennas is shown     

微波在液体火箭发动机真空羽流中的衰减

为研究液体火箭发动机真空羽流对微波的衰减作用,以某双组元液体火箭发动机为对象,使用热力计算程序对燃烧室内的电子数密度进行了计算,使用冻 结假设和有限化学反应速率假设两种情况对喷管内带电粒子的电离和再结合过程进行了模拟,并对羽流中带电粒子数密度和5~30GHz微波穿过羽流的衰减量进行了估算.研究结果显示:该发动机燃烧室和喷管出口的电子数密度量级分别为 1013~1014cm-3和1010~1011cm-3,K,Na等碱金属为主要电子释放剂,Cl-,OH-等基团为主要电子吸收剂;低频微波在羽流中衰减更严重,5GHz微波的衰减可达4.5dB;微波斜穿羽流的衰减通常大于横穿情况.      

结构吸波材料多层阻抗渐变设计及应用

对多层阻抗渐变的吸波结构设计思想进行了分析,介绍了多层阻抗渐变思想在吸波层板和泡沫两类结构吸波材料设计上的应用。理论计算与试验验证结果均表明,采用多层阻抗渐变设计能够使吸波层板和泡沫的吸波带宽向低频拓展,同时显著提高吸波泡沫的吸收强度。具有三个阻抗渐变吸收层的4 mm厚吸波层板在5~18 GHz频段反射率小于-10 d B;具有六个阻抗渐变吸收层的22 mm厚吸波泡沫在2~18 GHz频段反射率小于-10 d B,其中在6~18 GHz频段反射率小于-20 d B,8~12 GHz频段反射率小于-30 d B。多层阻抗渐变设计是提高结构吸波材料吸波性能的有效手段。     

Simulation of the Canadian GOES Signal Processor

An international experiment is being conducted to assess the use of geostationary spacecraft to relay 406 MHz distress beacon signals. The development is described of a signal processor that will search a nominal 10 kHz portion of the 406 MHz band, detect anddemodulate a small number of beacons, and produce an alertmessage with low probability of message error. It is shown that thenominal composite link C/No is about 30 dB Hz. The proposedprocessor is described and simulation results are presented. Theresults indicate that the processor has a threshold of about26 dB · Hz, a message error rate of 2 percent or less, and a messagetransfer time of less than 10 min.     

A hybrid amplifier as an RF building block

A hybrid RF amplifier SMD-chip offers the benefit of a really simple bypass circuitry, ease of construction and minimal size. As an example, with the MiniCircuits VNA, a gain of about 15 dB can be achieved through the frequency band of 500 MHz to 3 GHz. Input matching can be near a VSWR of 1.9. At frequencies above 3 GHz however the input might provide a reflection coefficient greater than unity depending on the mechanical solutions of the test setup. Conventional assembly techniques can be used, but hybrid amplifiers are better-suited to more complex SMD boards     

UWB radar for human being detection

UWB radar for detection and positioning of human beings in complex environment has been developed and manufactured. Novelty of the radar lies in its large operational bandwidth (11.7GHz at -10dB level) combined with high time stability. Detection of respiratory movement of a person in laboratory conditions has been demonstrated. Based on experimental results human being radar return has been analysed in the frequency band from 1 GHz to 12 GHz. Novel principle of human being detection is considered and verified experimentally.     

Ka频段卫星通信雨衰分析及解决对策

Ka频段卫星通信中,降雨引起的信号衰减对通信链路的通断起着非常重要的作用.本文在阐述雨衰原理的基础上,分析了Ka频段雨衰对信道特性的影响,提出了Ka频段抗雨衰的各种对策,并通过实例说明了对策的有效性.     

电路模拟吸波材料带宽拓展方法探索

电路模拟吸波材料有一定的频率选择特性,电磁波有效损耗的带宽通常比较窄,通过多层电路屏、掺杂电损耗介质、磁损耗介质层组合、磁电损耗组合的方法,对电路模拟结构吸波材料在2~18GHz区间电磁损耗带宽的拓展进行了初步探索。结果证明:四种方法都能够提高电路模拟吸波材料的有效吸波带宽,并能够不同程度地提高材料的吸波效率。多层电路屏、掺杂电损耗介质的多层电路屏、组合磁损耗介质层的多层电路屏、组合磁损耗介质层和电损耗介质的多层电路屏,其反射率≤-5dB的带宽较单层电路屏的1.2GHz分别增加了6.4、10.6、9.6、10.6GHz,最小反射率分别达到-8、-10、-12、-25dB。     

UWB Radar for Human Being Detection

UWB radar for detection and positioning of human beings in a complex environment has been developed and manufactured. The novelty of the radar lies in its large operational bandwidth (11.7 GHz at -10 dB level) combined with high time stability. Detection of respiratory movement of a person in laboratory conditions has been demonstrated. Based on experimental results, human being radar return has been analysed in the frequency band from 1 GHz to 12 GHz. The novel principle of human being detection is considered and verified experimentally.     

ATS-6 Preliminary Results from the 13/18-GHz COMSAT Propagation Experiment

The 13/18-GHz COMSAT Propagation Experiment (CPE) is reviewed, the data acquisition and processing are discussed, and samples of preliminary results are presented. The need for measurements of both hydrometeor-induced attenuation statistics and diversity effectiveness is brought out The facilitation of the experiment-CPE dual frequency and diversity site location, the CPE ground transmit terminals, the CPE transponder on Applications Technology Satellite-6 (ATS-6), and the CPE receive and data acquisition system-is briefly examined. The on-line preprocessing of the received signal is reviewed, followed by a discussion of the off-line processing of this database to remove signal fluctuations not due to hydrometeors. Finally, samples of the results of first-level analysis of the resultant data for the 18-GHz diversity site near Boston, Mass., and for the dual frequency 13/18-GHz site near Detroit, Mich., are presented and discussed.     

用活性碳毡制备电路模拟吸波材料的研究

研究了以粘胶基活性碳纤维为导电材料制备单层电路模拟吸波材料的微波吸收特性。结果表明：感性电路屏在毡条宽为5mm、α／b为2时吸波性能最好，在8GHz～18GHz内达到-10dB以下的反射衰减，最大衰减峰达一30dB以上；容性电路屏在毡块间距为5mm、α／b为1．4时吸波性能最好，在8GHz～18GHz内达到-10dB以下的反射衰减，最大衰减峰值-30dB以上。可用粘胶基活性碳毡制备质轻价廉的雷达吸波材料。     

Studies of Electromagnetic Properties of MWCNTs after Electroless Plating with Co-Fe Alloy

A method of electroless plating is utilized to deposit Co-Fe alloy on the surface of multi-walled carbon nanotubes (MWCNTs), and electromagnetic parameters of MWCNTs with and without electroless plating are discussed. The MWCNTs covered by Co-Fe is a desirable light absorbent in wide wave band by utilizing electroless plating process in experiments. Field-emission scanning electron microscope (FESEM) and field-emission transmission electron microscope (FETEM) images as well as energy dispersive spectroscopy (EDS) results are presented to show the morphology, components and electromagnetic parameters of MWCNTs. Electromagnetic properties of MWCNTs are enhanced after electroless plating observed from contrast of results between MWCNTs with and without plating. In conclusion, the covering Co-Fe on the surface of MWCNTs in 2-18 GHz frequency range has better electromagnetic properties. When the material is in the 6.5 GHz electromagnetic waves, the reflection loss is up to ?10 dB, and the bandwidth more than ?4 dB is 5 GHz. The excellent electromagnetic properties make it probable for MWCNTs to be utilized as absorbent in electromagnetic shielding materials.     

新型超宽带共面波导结构天线的设计

设计了一款共面波导馈电的新型超宽带平面天线,该天线印刷在介电常数为4．4的FR4覆铜介质基板上,尺寸为20mm×30min×1．2mm,利用仿真软件HFSS对天线参数进行优化仿真。调节辐射贴片上各枝节的长度与宽度,通过不同谐振点的耦合来展宽频带宽度,可实现天线频带宽度为3-11．7GHz（S11〈-10dB）,相对带宽达到119％。按照优化尺寸对天线进行加工,实测数据与仿真值基本吻合。结果表明,该天线不仅可以实现超宽频带,而且结构简单,尺寸小,易于集成。     

Observations of fragmented energy release

Energy release into coronal plasmas is observable in the forms of heating and acceleration. In flares and active stars, heating and acceleration have been found to be related as indicated by an approximately constant ratio of microwave (synchrotron) and soft X-ray (thermal) emission. The discovery suggests a flare-like heating process for the quiescent coronae of active stars.The energy release in solar flares involves several time scales: (i) The largest is the rate of homologous flares in an active region of the order of one per five hours. (ii) Hard X-ray andH emissions suggest a total flare duration of ten minutes, (iii) with individual episodes of contiguous acceleration of one minute. (iv) Elementary hard X-ray peaks have 5–10 s duration, corresponding to groups of beams observable as type III radio bursts. (v) The effective injection time of these beams is of the order 0.1 s. (vi) The smaller time scale is observed in narrowband radio spikes in the 0.2–8 GHz range with durations of a few times 0.01 s.     

ATS-6 Millimeter Wave Propagation and Communications Experiments at 20 and 30 GHz

The Applications Technology Satellite (ATS-6) Millimeter Wave Experiment, developed and implemented by the NASA Goddard Space Flight Center, has provided the first direct measurements of 20-and 30-GHz Earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques In addition to direct measurements on the 20-and 30-GHz links, methods of attenuation prediction with radars, rain gauges, and radiometers were developed and compared with the directly measured attenuation. This paper presents a review of the major results of the first year of measurements with ATS-6, with emphasis on the impact of the measurements on millimeter wave space systems design.