共查询到20条相似文献,搜索用时 140 毫秒
1.
本文通过矩量法及其高效数值方法(MLFMA)对近距离目标--单脉冲收发天线的电磁互作用进行一体化数值仿真,定量研究了单脉冲天线的近场角度测量特性.在该近场模型中,目标散射近场的幅、相分布和同轴探针激励的喇叭单脉冲天线的辐射场(对应远场和波束)、接收端响应(对应远场差波束)均采用全波数值模拟获得.首先,计算单脉冲天线的辐射场并将其作为对目标照射的激励条件;接着,计算目标散射近场的空间分布;并计算出单脉冲天线所接收到的目标散射场;最后,使用幅值法和相位法计算出单脉冲天线近场测角角度,并在此基础上对近距离测角误差进行研究.在导弹目标算例中,将天线--目标一体化建模和天线口径面上散射近场的幅、相分布计算结果用于近距离条件下单脉冲天线测角误差的研究,并通过频率、距离的变化对测角精度做了对比分析;发现目标近场散射幅、相分布的非均匀性,是导致单脉冲天线近距离角度测量产生较显著的测角误差的主要原因;而频率较低时,测角误差较小.文中给出了物理解释,并提出近距离测向时借助于较低频信号的校正以降低测角误差的建议. 相似文献
2.
幅度相误差会影响四元组射频目标模拟器中的最终目标模拟位置的精度。为了最大程度减小幅相误差,采用
迭代方法进行校准。迭代校准方法需要各射频器件的实际S21 的幅值和相位的实测数据,而高分辨率的数控衰减器和
移相器所需测量数据巨大,传统手工测试效率低下且准确度难以保证。为解决此问题,本文设计了一种基于VEE 的
自动测试系统。 相似文献
3.
提出了一种基于衰减器附加相位补偿技术的Ka波段四通道幅相控制芯片,采用有源矢量合成移相器和无源衰减器进行高精度幅相控制,每个通道由功率放大器、有源移相器、无源衰减器、功分器等单元构成。提出了一种新颖的基于可调谐补偿电容阵列的相移补偿技术,实现了较低的衰减附加相移。测试结果表明,通道增益大于24 dB,带内增益平坦度小于2 dB,输出1 dB压缩点大于10 dBm,发射效率大于12%@P_1dB,6位RMS移相精度小于2°,5位RMS衰减精度小于1 dB,衰减相位误差小于4°。 相似文献
4.
5.
6.
7.
8.
9.
10.
11.
The operation of a hybrid tracking (HT) phase-locked loop (PLL) in radio-frequency interference (RFI) is considered. Results from a perturbation analysis for the loop phase error in continuous-wave (CW) RFI are found to compare favorably with results obtained by digital computer simulation. These results, together with simulation results for wide-band (in comparison to the loop bandwidth) RFI, indicate that loop structures which track both on the signal carrier and modulation components are advantageous in RFI plus Gaussian noise backgrounds. 相似文献
12.
13.
The assumption that observed signals are ideally received is commonly used in the literature on time-delay estimation. However, for practical digital receivers, the received radio-frequency signals are usually downconverted to the baseband and digitized by analog-to-digital converters. Because inaccurate and unstable system clocks are used, frequency and phase offsets are usually induced by the frequency-mixing procedure, whereas a time stretch may ensue from the sampling procedure. The aforementioned problems are almost inevitable for incoherent reception systems. Therefore, the neglect of imperfect reception for incoherent systems may reduce the performance of conventional time-delay estimation methods. In this paper, employing refined signal models developed specifically for incoherent time-delay estimation in active and passive systems, the corresponding joint maximum likelihood estimates of time delay and system-clock frequency error are proposed. The Cramér–Rao lower bounds (CRLBs) on time-delay and clock frequency error estimations are also derived. The performance of the proposed time-delay estimators can be improved for frequency/phase offsets and time stretches, approaching the performance of the CRLBs in scenarios of moderate and high signal-to-noise ratios. Furthermore, both CRLBs analysis and simulation results verify that the accuracy of the proposed time-delay estimator is unaffected by the performance of the system clock in moderate scenarios. 相似文献
14.
An analysis is presented showing the effect of carrier phase error on the error-rate of a duobinary shaped, quaternary, phaseshift keying digital radio system. A simple upper bound on the probability of error as a function of phase error is derived and the results are compared to those obtained by computer simulation. The conclusion is reached that such a system exhibits approximately 1.0 dB degradation for a carrier phase error of 3° at an error-rate of 10-5and a 10 dB degradation at a phase error of 15°. 相似文献
15.
16.
17.
18.
Chow J.H. Littler I.C.M. Glenn de Vine McClelland D.E. Gray M.B. 《Lightwave Technology, Journal of》2005,23(5):1881-1889
This paper discusses a phase-sensitive technique for remote interrogation of passive Bragg grating Fabry-Pe/spl acute/rot resonators. It is based on Pound-Drever-Hall (PDH) laser frequency locking, using radio-frequency phase modulation sidebands to derive an error signal from the complex optical response, near resonance, of a Fabry-Pe/spl acute/rot interferometer. We examine how modulation frequency and resonance bandwidth affect this error signal. Experimental results are presented that demonstrate, when the laser is locked, this method detects differential phase shifts in the optical carrier relative to its sidebands, due to minute fiber optical path displacements. 相似文献
19.
20.
为了阐明随机偏振模板在光学加密系统中的作用,采用理论分析与数值模拟相结合的方法,进行了在双随机偏振光学加密系统中偏振模板的特性参量对系统加密效果及解密误差的影响的理论和仿真分析;对比了随机相位模板和随机偏振模板对光学加密系统加密效果及解密误差的不同影响。结果表明,加密方面,采用随机偏振模板或随机相位模板均能生成平稳白噪声分布的密文,但是偏振模板有两个构造参量,密钥空间更大;解密方面,系统对相位模板以及偏振模板中不同参量的解密敏感性有一定差异,随机偏振加密具有更高的应用灵活性。该结果对理解相位及偏振编码光学加密系统的本质属性及设计安全性更高的光学加密系统有一定的帮助。 相似文献