نتایج جستجو برای: twist reflector
تعداد نتایج: 16136 فیلتر نتایج به سال:
Abstract. Reflector antennas are characterized by very high gains (30 dB and higher) and narrow main beams. They are widely used in satellite and line-of-sight microwave communications as well as in radar. Reflector antennas operate on principles known long ago from the theory of geometrical optics. The first reflector system was made by Hertz back in 1888 (a cylindrical reflector fed by a dipo...
─ This paper presents and evaluates a parallel time domain analysis of a rectangular reflector on multicores machine. Rectangular reflector antennas have motivated the time-domain analysis of electromagnetic scattering problems. The asymptotic time domain physical-optics (TDPO) is applied to the analysis of a rectangular reflector illuminated by a Gaussian-impulse. It is a numerical technique u...
The future National Polar-orbiting Environmental Satellite System (NPOESS) Microwave Imager/Sounder (MIS), a space-borne conical scanning radiometer, uses an offset main reflector with multiple antenna feedhorns to receive upwelling microwave radiation from the Earth’s surface and atmosphere. The offset reflector approach is a convenient and economic way to achieve the desired antenna footprint...
NURBS surface representation, combined with Differential Evolution (DE), enables us to perform automated non-imaging reflector design. The overall result is a simple automated nonimaging reflector design technique and only a little data such as desired illuminance distribution and searching limits are needed. Merit functions specific to non-imaging reflector design are presented. Using differen...
Railway infrastructures are among the most important national assets of countries. Most of the annual budget of infrastructure managers are spent on repairing, improving and maintaining railways. The best repair method should consider all economic and technical aspects of the problem. In recent years, data analysis of maintenance records has contributed significantly for minimizing the costs. B...
A relatively fast and simple method utilizing Gaussian beams (GBs) is developed which requires only a few seconds on a workstation to compute the near/far fields of electrically large reflector antennas when they are illuminated by a feed with a known radiation pattern. This GB technique is fast, because it completely avoids any numerical integration on the large reflector surface which is requ...
Twist-weaving of kilim over the past centuries is preserved among the nomadic tribes of Kerman province, especially in Afshar tribe in Sirjan area and it has been used in decorating sofreh and salt bag. In recent decades, some changes are occurred in method of kilim weaving in this area and the "twist weaving" is used in all parts of kilim and has been famous as "Shirikipich Kili...
1 Introduction The previous researches on the modulated scattering antenna array (MSAA) have shown that the second-order intermodulation scattering signal is relatively low compared with the direct received signal [1]. In this report, a switched reflector is used to solve this problem. The diversity performance of the MSAA with a switched reflector is investigated. It is shown that the diversit...
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