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发射机及接收机的对准误差都会引起前置光放大卫星激光通信系统信号的衰落,在同时考虑发射机、接收机对准误差的条件下优化系统性能非常重要。将接收机对准误差引起的空间光耦合损耗用一个高斯函数近似,并同时考虑发射机对准误差引起的对准损耗,推导出了接收光功率概率密度的近似解析表达式,应用该概率密度函数,建立了基于平均误码率原则的前置光放大卫星激光通信系统的优化模型。仿真结果表明,在给定平均误码率要求及对准误差一定时,存在一个最佳发射光束宽度、接收天线直径及空间光耦合参数,使所需的发射功率最小,采用更大的接收天线并不能降低对发射功率的要求。 相似文献
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1数字卫星信号接收的特点(1)调整天线指向定位难模拟接收机接收的是模拟信号,天线是否对准卫星直接体现为信号的好坏,而数字接收机接收的是数字信号(0、1),天线是否对准卫星体现为信号有无,加上数字接收机收到卫星信号后需要时间做解压缩处理,因此数字接收机... 相似文献
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1概述
智能天线的原理是将无线电信号导向具体的方向,产生空间定向波束,使天线主波束对准用户信号到达方向(Direction of Arrival,DOA),旁瓣或零陷对准干扰信号到达方向,达到充分高效利用移动用户信号并消除或抑制干扰信号的目的。TD-SCDMA系统中,智能天线以多个高增益窄波束动态地跟踪多个期望用户。接收模式下,来自窄波束之外的信号被抑制;发射模式下,能使期望用户接收的信号功率最大,同时使窄波束照射范围以外的非期望用户受到的干扰最小。 相似文献
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为了响应莱芜市委市政府关于全力支持莱芜市省级开发区建设的指示精神 ,给韩国商人创造良好的生活环境 ,应有关部门及韩商的要求 ,我们于 2 0 0 1年 6月 5日在韩商别墅区架设了地面站 ,成功地接收到了韩国电视节目。下面谈一下接收韩国电视信号的体会。1 数字卫星信号接收的基础知识与模拟卫星信号接收相比 ,数字卫星信号接收的特点是 :(1)调整天线指向定位难模拟接收机接收的是模拟信号 ,天线是否对准卫星直接体现为信号的好坏。而数字接收机接收的是数字信号 (0、1) ,天线是否对准卫星体现为信号有无 ,加上数字接收机收到卫星信号后需要… 相似文献
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卫星地球站天馈线系统是地球站播出设备的重要组成部分之一,是保证卫星地球站正常运行和传输质量的关键设备。地球站的天馈线系统.是实现空间传播的电磁波能量与发射或接收的行波能量之间联系的设备.它把发射设备产生的大功率微波信号,以微波的形式向卫星方向辐射.并接收卫星转发的微波信号,送至接收低噪声放大器。天馈系统由伺服控制系统保证天线轴始终对准卫星方向。因此,正确对天馈线系统进行维护就显得特别重要。 相似文献
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通过使用频谱仪或接收机来寻找、调整、接收卫星信号,使地球站天线和卫星天线口面准确无误地对准,从而进行信号交换。 相似文献
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郑秀峰 《卫星电视与宽带多媒体》2005,(19):66
一用户新安装一套模拟套站。入夏时节,一场风雨过后,就接收不到信号了。最初怀疑天线被风吹偏了,怎么调整天线也接收不到信号。四日后,用户将接收机和高频头一并拿给笔者,让笔者帮助检修。先将接收机与室外已对准卫星的天馈系统连接,能接收到信号。换上用户的高频头,则接收不到 相似文献
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一种基于正弦波磁光调制的空间大范围方位自动对准方法 总被引:8,自引:0,他引:8
针对基于正弦波磁光调制的方位对准系统存在方位失调角对准范围小的问题,在阐述了方位对准原理、分析磁光调制后混合信号成分的基础上,提出了一种空间大范围方位自动对准方法。通过磁光调制前后交流信号(AC)的相位对比得出了判断失调角正负的方法,利用方位对准系统中下仪器的初始架设位置和转动方式实现了初始光强的自主测量,在此基础上利用大角度范围内采集的磁光调制后的直流信号(DC)建立了粗略失调角的计算模型,并详述了具体实现方案,下仪器在粗略失调角信号的控制下逐渐转动至小角度范围内。之后,利用磁光调制后采集的交流信号实现了小角度范围内失调角的精确测量,两个模型紧密配合保证了空间大范围方位自动对准。仿真结果表明,提出的方法理论上可以实现-90°~90°范围内较高精度的自动对准,有效扩大了方位失调角的对准范围,解决了传统的方位对准范围小的问题。 相似文献
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A novel wideband LFM interference suppression method is proposed based on fractional Fourier transform (FRFT) and projection techniques. By using the concentration property of LFM interferences in fractional Fourier domain, the initial frequency, frequency modulation rate and direction-of-arrival (DOA) of LFM interferences are first estimated. Afterwards, the space–time interferences subspace is constructed. In order to suppress wideband LFM interferences, the received signal is projected onto the subspace orthogonal to the interferences subspace when the signals are uncorrelated. Furthermore, considering the scenario when the signals are coherent, according to the properties of oblique projection, LFM interferences are suppressed by projecting the received signal onto the joint signal–noise subspace. Then, the desired signal is extracted by beamforming. Unlike the existing algorithms, the proposed method not only can exactly estimate parameters and directly solve the DOA of LFM interferences but also can construct the interferences subspace with the time-variant steering vector of interferences. Moreover, our method can effectively suppress LFM interferences without reducing the freedom, and significantly improve the performance, even at low signal-to-noise ratio (SNR) or small number of snapshots. Simulation results demonstrate the effectiveness of the proposed method. 相似文献
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V. P. Ryabukha D. S. Rachkov A. V. Semeniaka Ie. A. Katiushyn 《Radioelectronics and Communications Systems》2012,55(10):443-451
We consider separate space-time adaptive signal processing against the background of combined interferences, which involves the fixation of weight vector of spatial signal processing against the background of noise interferences for the time of adaptive interperiod signal processing against the background of clutter. By means of mathematical modeling and hydroacoustic simulation the fixation interval is estimated, which keeps in allowable limits the losses in quality of noise interferences suppression. 相似文献
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It is commonly known that, in order to calculate the demodulated noise power of the wanted frequency division multiplexedfrequency modulated (FDM-FM) signal due to interference, the convolution between the power spectra of the wanted FM signal and interference is required to be obtained. This concise paper shows a simple approach to calculate this convolution without direct calculation of the power spectrum of the FDMFM signal when the power spectrum of the interference is given (by measurements or calculation) and the highest and lowest channel frequencies of the baseband signal and rms frequency deviation of the wanted FDM-FM signal are known. Since the calculation of the FDM-FM signal power spectrum is not an easy problem in some cases, this approach makes much simpler an accurate evaluation of the output noise power due to interference. 相似文献
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A new direction-of-arrival (DOA) estimation method for coherent global positioning system (GPS) signals is proposed. It is applicable to the GPS propagation environment with rich multipath, strong interferences and noise. According to the properties of oblique projection, interferences and noise are first suppressed and only the coherent GPS signals are retained by projecting the received signal onto the signal subspace. Then, the coherent GPS signals are resolved by the Toeplitz decorrelation scheme. Using the proposed method, interferences and noise can be suppressed simultaneously, and more accurate DOA estimation for coherent GPS signals can be obtained in GPS propagation environment. Simulation results demonstrate the effectiveness of the proposed method. 相似文献
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CCD类成像器件的噪声研究 总被引:1,自引:1,他引:0
CCD图像传感器的输出信号是空间采样的离散模拟信号,其中夹杂着各种噪声和干扰。对CCD信号进行处理的目的就是在不损失图像细节的前提下,尽可能地消除噪声和干扰,以提高信噪比,获取高质量的图像。为此,必须对CCD的噪声种类和特性有所了解,并针对各种噪声进行相应的去噪处理。所以对CCD成像器件噪声部分的研究,有利于提高CCD成像器件的分辨率,也能提高探测微弱光的能力。 相似文献