共查询到20条相似文献,搜索用时 109 毫秒
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(上接第 0 9/ 10期 )4 .2 广播电视微波匹配传输与导抗圆图计算在微波广播电视匹配传输设计中 ,在传输线的计算 ,也就是某些波导元件的分析和微波测量等方面 ,经常要遇到阻抗设计计算的问题。如已知负载阻抗ZL,求传输线的输入阻抗 ,或已知驻波比S及波节点位置 ,求解负载阻抗等。当然 ,这些也可以采用数学公式来计算 ,但是 ,这种运算是很麻烦的。我们在微波广播电视匹配传输设计计算实践中 ,总结出各种不同形式的诺模图 (图形计算 )计算方法 ,既简便迅速 ,又具有满足设计计算要求的准确度。其中一种就是由等反射系数圆、等电阻圆、等电抗… 相似文献
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为满足上海65 m射电望远镜噪声注入要求,设计了一种新型的同轴环激励圆波导耦合器,该耦合器有较低的同轴激励口驻波和平坦的耦合值,利用环天线和传输线概念分析了该耦合器的工作原理,作为实例,设计了一个S波段的耦合器,加工了耦合器实物样品,实验测量表明,测量结果和仿真结果吻合良好。 相似文献
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结合Smith圆图,利用微波大功率自动调配器测试系统,采用负载牵引法,给出搜索等功率圆曲线的算法。此算法在可以确定的圆方程上进行搜索,避免了在整个圆图中搜索很多个点再进行圆回归拟合的繁琐。等增益、等噪声都是可以Smith圆图中表示的圆,因此,此算法对以后其他参数的圆图搜索也有实际意义。 相似文献
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一种改善圆阵波束指向性性能的加权方法 总被引:1,自引:0,他引:1
该文在分析圆阵波束指出性的基础上,提出了一种改善圆阵波束指向性性能的对称指数加权方法,利用该方法能较有效地抑制旁瓣,而主瓣的增宽效应并不明显。 相似文献
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WQ—502型自动外圆切割机电子工业部第45研究所黄克飞,王明权概述WQ—502型自动外圆切割机是参阅瑞士TS4型大片自动外圆切割机的设计特点,根据国内使用厂家的要求设计的一种新型切割设备。该机可广泛用于光学玻璃、磁性材料、石英、陶瓷、冰洲石等脆硬晶... 相似文献
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介绍了提高ACTFELD对比度的一种新方法,该方法利用在显示面板前添加圆偏振片来减小环境光对对比度的影响。在2800lx的环境光照射下,得到了加有圆偏振片的显示区比无圆偏振片的显示区对比度高33%的结果。 相似文献
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本文研究主动视觉系统中投影仪的平面标定方法。用固定的投影仪向画有青色同心圆的标定板上投影黄色与洋红色相间的棋盘格,用固定的摄像机采集若干幅标定板不同朝向的图像,对采集图像进行颜色通道过滤,得到投影仪标定所需的同心圆分量和棋盘格分量,结合摄像机投影仪图像之间的映射关系和同心圆的秩2约束来标定投影仪。此方法仅需用三幅图像,不仅可以标定出投影仪的所有内参数(包括倾斜参数),如果再一步深入,还可以标定出摄像机的内参数矩阵和主动视觉系统的外参数矩阵。实验结果表明本文的标定算法精度比较可观。 相似文献
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飞机电源系统恒功率电子负载的EMI滤波器设计 总被引:1,自引:0,他引:1
功率开关装置驱动的电动机控制系统,作为飞机电源的负载时必须采用EMI滤波器,以消除对电网的高频噪声。由于闭环系统为电源的恒功率负载,有负阻抗特性,在EMI滤波器的设计中,必须考虑系统的稳定性。该论文研究了这种恒功率电子负载的EMI滤波器设计方法,给出了滤波器参数的约束条件。 相似文献
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An analytical expression for the minimum achievable noise figure for a specified gain at a given frequency is derived for a microwave amplifier. The minimum noise figure is given in terms of the specified gain, the amplifier noise parameters, and the S-parameters. Similarly, another expression for the maximum gain at a specified noise figure is derived in terms of the noise figure, the noise parameters, and the S-parameters. It is shown that these expressions simplify the tradeoff considerations for broadband low noise amplifier design by avoiding the need to draw several constant noise and gain circles at each frequency of interest 相似文献
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Niu G. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(9):1583-1597
This paper presents an overview of the physics, modeling, and circuit implications of RF broad-band noise, low-frequency noise, and oscillator phase noise in SiGe heterojunction bipolar transistor (HBT) RF technology. The ability to simultaneously achieve high cutoff frequency (f/sub T/), low base resistance (r/sub b/), and high current gain (/spl beta/) using Si processing underlies the low levels of low-frequency 1/f noise, RF noise, and phase noise of SiGe HBTs. We first examine the RF noise sources in SiGe HBTs and the RF noise parameters as a function of SiGe profile design, transistor biasing, sizing, and operating frequency, and then show a low-noise amplifier design example to bridge the gap between device and circuit level understandings. We then examine the low-frequency noise in SiGe HBTs and develop a methodology to determine the highest tolerable low-frequency 1/f noise for a given RF application. The upconversion of 1/f noise, base resistance thermal noise, and shot noises to phase noise is examined using circuit simulations, which show that the phase noise corner frequency in SiGe HBT oscillators is typically much smaller than the 1/f corner frequency measured under dc biasing. The implications of SiGe profile design, transistor sizing, biasing, and technology scaling are examined for all three types of noises. 相似文献
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测量含有自动增益控制(AGC)电路的射频模块噪声系数时,使用Y因子法将改变模块的功率增益,进而无法测定.本文提出了一种新的噪声系数测量方法.该方法在信噪比较小的条件下用误码率推算前端的载噪比,避免了用仪器标定载噪比受信道滤波器通带平坦性影响较大的问题;测量过程中,AGC输入端信号和噪声的总功率几乎不变,能够保证AGC功率增益不变,从而可准确测量含有AGC电路的射频模块噪声系数.通过理论推导和数值模拟分析了随机误差、系统误差、实验温度以及测量次数对噪声系数估计的影响,验证了方法的有效性.本文成果已用于我国"北斗一号"卫星导航定位用户机的射频模块测量. 相似文献
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Yuhua Cheng Chih-Hung Chen Matloubian M. Deen M.J. 《Electron Devices, IEEE Transactions on》2002,49(3):400-408
High-frequency (HF) AC and noise modeling of MOSFETs for radio frequency (RF) integrated circuit (IC) design is discussed. A subcircuit RF model incorporating the HF effects of parasitics is presented. This model is compared with the measured data for both y parameter and fT characteristics. Good model accuracy is achieved against measurements for a 0.25 μm RF CMOS technology. The HF noise predictivity of the model is also examined with measured data. Furthermore, a methodology to extract the channel thermal noise of MOSFETs from HF noise measurements is presented. By using the extracted channel thermal noise, any thermal noise models can be verified directly. Several noise models including the RF model discussed in this paper have been examined, and the results show that the RF model can predict the channel thermal noise better than the other models 相似文献
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Measuring the noise generated by a pulsed RF amplifier is not a simple task [1]. One method of making this measurement converts the RF pulse to video with a phase detector and uses a spectrum analyzer to measure the noise between the lines of the pulse spectrum. The measurement includes the combined effects of timing jitter, power-supply modulation, and amplifier noise. An alternate method, described in this note, requires less test equipment by using an RF spectrum analyzer to measure the noise at a point outside the pulse spectrum. This measurement responds only to amplifier noise and is valid if the noise density is the same both inside and outside the pulse spectrum. Since this situation tends to be true of broad-band amplifiers such as TWT's and CFA's, the second method is preferable because of its relative simplicity. This note describes the procedure for measuring pulsed amplifier noise using an RF spectrum analyzer. The test setup and measurement procedure are described, as well as the conversion of the measured spectral-density ratio to an equivalent CW signal-to-noise ratio. 相似文献