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An arcing amplifier in a large amplifier array operating from a common power supply and energy storage bank must be isolated from the rest of the system to permit continuous operation of the system. A gas-tube isolator circuit is proposed wherein the tube is programmed to charge the individual secondary capacitance bank of each amplifier during the interpulse interval. Since the gas tube is nonconducting during the pulsing period of the amplifier, it isolates the amplifier from the rest of the system in case of a fault. 相似文献
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A ceramic material having a large dielectric constant at 77 K, ε=8000-12000, has been developed for capacitive energy storage at this temperature. A large matrix of multilayer ceramic capacitors were fabricated using conventional tape-casting methods to optimize the dielectric breakdown strength at 77 K, and measured energy storage values on these capacitors range up to 6 J/cm3 at 77 K. An unfused bank of these capacitors was voltage-cycled 105 times at 77 K without failure, and the heating effects during cycling were immeasurably small (i.e., nitrogen boiloff was monitored). An electrocaloric effect on discharge (ΔT~1 K) contributes to the thermal stability. Measurements of the frequency dependence of the dielectric properties of the ceramic at 77 K indicate a fundamental limit of about 8 μs for the switching repetition rate. Improved capacitor-manufacturing methods are discussed which can increase the energy density to the 20-30 J/cm3 range 相似文献
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一些航拍图像的尺寸较大,现有的特征点提取算法在对其处理时均要耗费大量的时间,针对这一问题,提出一种快速有效的特征点提取算法。首先构造原始图像的拉普拉斯金字塔,以获得图像的尺度信息,同时保留图像的方向信息;再使用非均匀多方向滤波器组将金字塔图像分解在不同方向上,在分解后的图像中提取局部极值点作为候选特征点集;采用特定的合并策略合并候选特征点最终得到特征点集,并根据方向滤波器组为特征点分配方向向量。试验结果表明,本文算法在基本保证提取到的特征点匹配率及正确率的前提下,有较高的效率。 相似文献
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一些航拍图像的尺寸较大,现有的特征点提取算法在对其处理时均要耗费大量的时间,针对这一问题,提出一种快速有效的特征点提取算法。首先构造原始图像的拉普拉斯金字塔,以获得图像的尺度信息,同时保留图像的方向信息;再使用非均匀多方向滤波器组将金字塔图像分解在不同方向上,在分解后的图像中提取局部极值点作为候选特征点集;采用特定的合并策略合并候选特征点最终得到特征点集,并根据方向滤波器组为特征点分配方向向量。试验结果表明,本文算法在基本保证提取到的特征点匹配率及正确率的前提下,有较高的效率。 相似文献
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An analysis of the relationship between a linear amplifier chain and an analog-to-digital converter (ADC) in a digital microwave receiver, with respect to sensitivity and dynamic range issues, is presented. The effects of gain, third-order intermodulation products and ADC characteristics on the performance of the receiver are illustrated and design criteria for the linear amplifier chain (given a specified ADC) are developed. A computer program is included which calculates theoretical receiver performance based on gain and third-order intermodulation product selections. Experimental results are also presented and compared with theoretical values 相似文献
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Ross M. Hankin R. B. Dallafior E. P. Swendsen R. H. 《IEEE transactions on aerospace and electronic systems》1966,(1):62-73
Electrooptical systems exist which can make use of the available bandwidth and directivity at optical frequencies without utilizing the coherence aspects of lasers. Development of a sensitive, very highspeed (microwave response) photoelectric detector which can function as a high-gain microwave amplifier and mixer is described. Sysyems are described for radar, communications, and reconnaissance purposes. Basic noise considerations are shown. CW and FM-CW optical range and range rate tracking systems are described in which the required detection bandwidth is not a direct function of the range resolution, allowing highly accurate range and range rate determination at low signal levels. Communication systems utilizing noncoherent carriers, microwave subcarriers, and the dynamic crossed field electron multiplier as the detector-amplifier-mixer are described. 相似文献
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A new resonant mode power amplifier design is described which has a number of advantages over the power amplifiers available today. In particular, it has low or no EMI because of the nature of its operation. The new amplifier design is based upon a resonant mode dc-dc converter used in a push-pull configuration. All the advantages of the resonant mode power converters, such as high efficiency, small size and weight, excellent dynamic performance, low or no EMI (compared to PWM switch mode power converter), etc., are present in this new design. 相似文献
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基于噪声匹配的有源接收天线设计 总被引:1,自引:0,他引:1
为了提高接收天线的增益和灵敏度,采用将天线与低噪声放大器集成到一起设计的方案,将天线的输出阻抗作为放大器的源阻抗,省略了天线与放大器之间的阻抗匹配网络。通过调节天线馈电系统的尺寸调节天线阻抗,使其等于放大器的最佳源阻抗。利用HFSS仿真软件计算天线的辐射特性及阻抗,用ADS Designer软件对低噪声放大器进行优化设计。利用2SC5507晶体管设计了一个工作于2.0GHz的与低噪声放大器集成在一起的缝隙耦合微带天线,所设计的噪声系数为1.664dB,放大器增益为16.75dB。 相似文献
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The possibilities of using spectrographic observations of microwave radio emission as a solar flare plasma diagnostic are discussed. The spectral fine structure of the emission is interpreted in the context of plasma emission mechanisms. The balance equations for particles and plasma turbulence together with the transfer equations for electromagnetic waves in a plasma are solved for a model containing a diverging magnetic loop. As a result of the analysis of the blip-type spectral feature, the structure of energy release region and the unperturbed plasma concentration in the preflare loop are evaluated. The number of accelerated electrons and the intensity of the plasma turbulence in the source region are estimated using the properties of the weak continuum emission following the blip. Based on the degree of circular polarization of both the narrow band and the continuum emission, estimates for the external magnetic field strength and the angular width of the radiating plasma turbulence have been obtained. 相似文献
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The key issues in microwave power system engineering are beam safety, frequency allocation, and affordability. These major issues are presented, discussed, and suggestions for resolving them are offered. The issue of beam safety can be captured in the phrase “Fear of Frying.” Can a properly engineered beamed power safety system allay the public perception of microwave radiation dangers? Openness, visibility, and education may be keys to resolving this issue satisfactorily. “Not in my Spectrum” is a phrase that is frequently encountered in connection with the issue of where can the microwave power beam frequency be located. International cooperation may provide a part of the solution to this issue. “Wow, that much!” is a phrase encountered when dealing with the issue of economic affordability of large beamed power systems. A phased engineering approach for multiple uses even during construction is presented to aid in garnering revenue during the system build phase. Also, dual mode DC-RF converters are encouraged for bi-directional power flow utility and economies of scale in production 相似文献
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Reducing energy storage requirements of space power systems by illuminating the photovoltaic arrays with a remotely located laser system is addressed. It is proposed that large lasers be located on cloud-free sites at one or more ground locations and that large lenses or mirrors with adaptive optical correction be used to reduce the beam spread due to diffraction or atmospheric turbulence. During the eclipse periods or lunar night, the lasers illuminate the solar arrays to a level sufficient to provide operating power. Two applications are discussed: illumination of geosynchronous orbit satellites and illumination of a moonbase power system. Issues for photovoltaic receivers for such a system are discussed 相似文献
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Schiller G.J. Maybeck P.S. 《IEEE transactions on aerospace and electronic systems》1997,33(4):1122-1131
The application of moving-bank multiple model adaptive estimation and control (MMAE/MMAC) algorithms to an actual spade structure (Space Integrated Controls Experiment (SPICE)) being examined at Phillips Laboratory at Kirtland AFB, NM, is presented. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. Kalman filtering and LQG (linear system, quadratic cost, Gaussian noise) control techniques are utilized as the primary design tools for the components of the MMAE/MMAC. Implementing a bank of filters or controllers increases the robustness of the algorithms when uncertainties exist in the system model, whereas the moving bank is utilized to reduce the computational load. Several reduced-order models are developed from the truth model using modal analysis and modal cost analysis. The MMAE/MMAC design with a substantially reduced-order filter model provides an excellent method to estimate a wide range of parameter variations and to quell oscillations in the structure. 相似文献
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This review attempts to present an integrated view of the several types of solar cosmic ray phenomena. The relevant large and small scale properties of the interplanetary medium are first surveyed, and their use in the development of a quantitative understanding of the cosmic ray propagation processes summarised. Solar cosmic ray events, in general, are classified into two phenomenological categories: (a) prompt events, and (b) delayed events. The properties of both classes of events are summarised. The properties considered are the frequency of occurrence, dependence on parent flare position, the time profile, energy spectra, anisotropies, particle species, velocity dispersions, etc. A single model is presented to explain the various species of delayed event. Thus the halo and core events, energetic storm particle events, EDP events and proton recurrent regions are suggested to be essentially of common origin. The association of flare particle events with electromagnetic phenomena, including optical, X-ray and microwave emissions is summarised. The conditions in a sunspot group, and solar flare that are considered to be conducive to cosmic ray acceleration processes are discussed. Considerable discussion is devoted to physical processes occurring near the Sun. Near Sun particle storage, and diffusion, and secondary injection processes that are triggered by a far distant solar flare are reviewed. In order to explain the considerable differences between aspects of the prompt and delayed events, we propose selective diffusion processes that only occur at early times in a solar flare. The type IV radio emissions at metric wave-lengths are suggested to yield direct evidence for the storage processes that are necessary to explain the properties of the delayed events, and also as yielding direct evidence of secondary injection processes. We conclude by briefly summarising the ionospheric effects of the solar cosmic radiation. 相似文献
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探讨吸波Cf和吸波SiCf的制备方法方法和微波电磁特性,降低Cf的碳化温度、改变Cf的截面形状和大小、对Cf进行表面改性以及对Cf进行掺杂改性能制备出吸波性能优良的Cf,采用高温处理,对纤维进行表面改性和掺杂异种元素可制备出吸波SiCf. 相似文献