共查询到20条相似文献,搜索用时 62 毫秒
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Hybrid technique of finite element method (FEM) and Gaussian mode expansion method is implemented for the analysis of transmission
property of dielectric phase gratings used in holographic power combining systems. It takes advantages of the versatility
of FEM and the simplicity of the mode expansion method. Apparently, this hybrid method is well suited for the analysis of
phase gratings with complex profiles, which provide more degrees of structural freedom than those of classical rectangular
groove gratings. The transmitted fields of an array of two and three fundamental Gaussian beams through the multi-stepped
and curved gratings are calculated by the hybrid method. Numerical results show that much less phase distortion can be fulfilled
for the reconstructed pseudo-plane wave by the modified phase gratings, especially the curved ones. This is advantageous for
improving the combining efficiency in spatial millimeter wave and sub-millimeter wave power combining systems. 相似文献
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Jungang Miao Thomas Rose Klaus Kunzi Peter Zimmermann 《International Journal of Infrared and Millimeter Waves》2002,23(8):1159-1170
The instrument concept of a future spaceborne millimeter/sub-millimeter radiometer is proposed in this paper for the remote sensing of ice clouds from satellite. The proposed radiometer is expected to operate at a series of frequencies within the millimeter and sub-millimeter wave range from 150 to about 900 GHz. Five frequencies are selected in the atmospheric windows, i.e., 150, 220, 463, 683, 874 GHz, and at each frequency there are two orthogonally polarized channels. Three water vapor channels located close to 183.31 GHz are also included in this instrument, since they can provide water vapor information, which is needed for ice cloud parameter retrieval. To simplify system design and test, a modular design philosophy is followed in the receiver frontend design and two antennas are used separately for the millimeter and sub-millimeter channels. Overall, the instrument requirements can be met with today's technology, except for the channels at the highest frequencies, where the radiometric sensitivity can be larger than the required 1.0 K for the 10 km spatial resolution (2.5 ms integration time). However, this situation can be improved by averaging neighboring pixels in data processing if certain compromise in the spatial resolution can be made at these frequencies. 相似文献
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《Journal of Quantitative Spectroscopy & Radiative Transfer》1987,38(2):121-130
The measurement of small concentrations of hydrogen peroxide through the detection of rotational transitions in the millimeter and sub-millimeter wave regions is discussed. Calculated transition frequencies and absorption coefficients of H2O2 for frequencies up to 2000 GHz are presented. The reliability of the calculated values is illustrated by measurements of the linewidths and absorption coefficients of transitions in the 140 GHz range. Finally, methods for the detection of trace quantities of the peroxide molecule are briefly described. 相似文献
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In this paper, a planar Schottky varistor diode is studied and modeled by equivalent circuit method and three dimensional full wave electromagnetic (3D-EM) method, respectively. The diode's equivalent circuit is extracted from millimeter-wave small-signal S-parameter measurements. Since the package of the diode influences the electromagnetic field distribution at millimeter and sub-millimeter wavelengths, a 3D-EM model and an improved equivalent circuit model is applied to describe the field precisely. The simulated results of equivalent circuit, improved equivalent circuit and 3D-EM model are compared with the measured results. In addition, the effects caused by silver paste conductive adhesive are considered in 3D-EM model and improved equivalent circuit model. The results show that both the 3D-EM model and improved equivalent circuit model have good S-parameter consistency with measured results. 相似文献
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A millimeter and sub-millimeter wave frequency selective surface beamsplitter for geostationary orbit microwave radiometers 下载免费PDF全文
We report the design of three frequency selective surface(FSS) filters used on the FengYun-4(FY-4) microwave satellite,which separate five-frequency bands in the frequency range of 50-429 GHz with the insertion loss less than 0.4 dB,and separation between adjacent channels more than 20 dB for either TE or TM incidence.Firstly,we briefly introduce the disadvantages of two types of FSS filter:waveguide-array FSS and printed FSS,which are commonly employed in the millimeter and sub-millimeter wave band.In order to meet the insertion loss requirement and specified spectral transmission response,we adopt a filter composed of two closely spaced freestanding metal plates,which contains an array of resonant ring slot elements.Computer simulation technology(CST) is used to optimize the structural dimensions of the resonant unit and interlayer separation.Numerical results show that these FSS filters exhibit transmission loss of less than 0.4 dB and separation between adjacent channels of more than 20 dB.Simulated transmission coefficients are in close agreement with the required specification,and even exceed the performance specifications. 相似文献
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Wenkai Xie Guangdi Qian Zhixun Cheng Shenggang Liu 《International Journal of Infrared and Millimeter Waves》1999,20(12):2091-2098
Very efficient power combining of solid-state millimeter wave sources may be obtained through 3-mirror quasi-optical resonators and Source arrays. The location and configuration of the source array are determined by CAD (Computer-aided design) technique. 相似文献
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对曲折圆形槽波导新型慢波系统的高频特性进行了研究,通过理论分析和数值计算,得到了它的色散曲线和耦合阻抗表达式,并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明:当周期变小时色散减弱,耦合阻抗增加;而增大直波导长度时色散变弱,但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低,可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点,在毫米波及亚毫米波段的行波管中具有较好的发展前景。 相似文献
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Gordon R. Harrison Thomas E. Sharon 《International Journal of Infrared and Millimeter Waves》1988,9(5):443-468
Many present and future military and commercial systems operating at millimeter wave frequencies require the use of sophisticated electronically controllable antennas for maximum capability and flexibility. Electronic control of the antenna pattern is provided by electronically switchable phase control of each radiating element such as that achieved in phased array antennas or via electronically reconfigurable antenna feeds referred to as beam forming networks (BFN). Multibeam antennas provided by BFN'S can be realized using switches, variable power dividers (VPD), and phase shifters. Ferrite materials and associated application technology are being utilized to achieve these switchable RF control components at millimeter wave frequencies. The performance achievable in ferrite switchable circulators, variable power dividers and phase shifters in the frequency region from 20 to 100 GHz is discussed. 相似文献
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S. Ramakrishnan S. S. Sarin 《International Journal of Infrared and Millimeter Waves》1999,20(3):453-459
Injection locked Gunn oscillators have been developed to amplify the upconverted millimeter wave frequencies. They are being used in millimeter wave communication systems at Ka, V and W-Bands respectively. 相似文献
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AbstractAn approach to generate an optical millimeter wave is introduced with frequency octupling using two cascaded polarization modulators followed by polarizers, respectively. By adjusting the modulation indexes of polarization modulators, only the ±4th-order sidebands are generated with a pure spectrum. Since no filter is needed, the proposed technique can be used to generate a frequency-tunable millimeter wave with a large frequency-tunable range. To prove the feasibility of the proposed approach, a simulation is conducted to generate an 80-GHz millimeter wave, and then its transmission performance is checked. 相似文献
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S. Van den Bulcke L. Zhang A. Franchois J. M. Geffrin J. Stiens 《International Journal of Infrared and Millimeter Waves》2008,29(11):1038-1047
For the development of millimeter wave imaging systems, it is important to be able to simulate some representative scattering
configurations. Typically, Gaussian beams are used in active imaging systems. Since these beams only illuminate a spatially
limited region, many objects can be treated as infinitely long 2D (in)homogenous cylinders. However, the incident Gaussian
beams have a 3D character. Therefore, a dedicated 2.5D scattering simulator was developed. In this paper, simulation results
obtained with this simulator are compared to measurements obtained from a bi-static microwave set-up and from a W-band millimeter
wave set-up. Comparison of simulations and measurements proves that the 2.5D algorithm is a good simulation tool to study
scattering of long inhomogeneous cylinders, illuminated by 3D plane waves or 3D Gaussian beams under different elevation angles. 相似文献
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A new method of measuring velocity and attenuation of leaky surface waves is presented. A single focused transmitting transducer and linear receiving array in a pitch-catch arrangement are used in the proposed system. The spatial distribution of the acoustic field in the leaky wave is recorded by the array, and the parameters of the leaky wave can be obtained by processing the output waveforms. In comparison with existing material characterization systems, the mechanical scanning of the transducers is not used any more, and the measurement time is only limited by the time of the wave propagation and speed of the electronic data acquisition system. 相似文献
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Quasi-Optical Sensors for Investigation of Acousto-Electromagnetic Phenomena of Popocatepetl Volcano
M. Tecpoyotl-T S. V. Koshevaya E. A. Gutiérrez-D A. Torres-J D. O. Solovjov 《International Journal of Infrared and Millimeter Waves》1999,20(11):1889-1893
This article focuses on meteorological electronics based on the space research of acoustic-electromagnetic phenomena caused by Popocatepetl volcano (Mexico). The main purpose is to present two different types of quasi-optical sensors, one of them is formed by a modulator based on a surface oriented p,i,n structure with deep junctions; and by a silicon detector (avalanche photodiode with separated regions of absorption and multiplication: APDSAM). This system guarantee both good sensibility and wide range of sensing, sub-millimeter and millimeter range. This sensor has the advantage that can be realized as a planar array. On the other hand, for the remote measurement of basic meteorological parameters and chemical state by means of radiobrightness temperatures (radiometer systems) a low noise receiver on the base of dielectric waveguide and Schottky diodes cooled by means of cryoelectronic element is used. 相似文献
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Y. Yan 《International Journal of Infrared and Millimeter Waves》2001,22(2):361-371
As the operating frequencies of communication systems more higher into the millimeter wave range, and the density of particles in medium is more denser, the effects of multiple scattering in sandstorm become more significant. This paper treats the problems of electromagnetic multiple scattering in strong sandstorm by the Monte Carlo method. Based on the analytical theory of multiple scattering, the millimeter wave propagation and scattering in discrete random media are investigated by means of the particle-tracking technique. The millimeter wave is regarded as a Markov chain of wave particle collisions in a medium in which it is scattered and absorbed. Considering the effect of multiple scattering, millimeter wave attenuation induced by strong sandstorm is simulated numerically. The values of theoretical calculation are in good agreement with the measured results of simulated experiment at 34 and 93 GHz. 相似文献