A NEW DIGITAL MODULATION RECOGNITION METHOD USING FEATURES EXTRACTED FROM GAR MODEL PARAMETERS

Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognition method is proposed in this paper. Because of the better noise suppression ability of the GAR model and the powerful pattern classification capacity of the MLP neural network classifier, the new method can significantly improve the recognition performance in lower SNR with better robustness. To assess the performance of the new method, computer simulations are also performed.     

Binary code compression algorithm used for the real time compensation of the modulation error in miniaturized FOG

This paper presents a kind of novel binary code compression algorithm to reduce the size of the signal processing circuit and to realize real time compensation for the modulation error in fiber optic gyroscope (FOG). The disadvantage of general compensation method is figured out firstly. The modulation error is modeled and analyzed with taking the closed-loop characteristics into consideration. The analysis indicates the condition in which the error compensation is effective and real time. Then the compensation algorithm based on binary code compression operation is described. The functional design of the algorithm is realized in a single field programmable gate array (FPGA) by using modular design method, substituting some harewares in signal processing circuit, and system speed is very fast. The simulation and experiment results suggest that the algorithm and implementation is valid. The modulation error is real time compensated in every error detection cycle, and the error compensation resolution is enhanced from 2⁻¹⁰ to 2⁻¹⁶ rad/V.     

Optimization of exit-plane waves restored from HRTEM through-focal series

Atomic-resolution transmission electron microscopy has largely benefited from the implementation of aberration correctors in the imaging part of the microscope. Though the dominant geometrical axial aberrations can in principle be corrected or suitably adjusted, the impact of higher-order aberrations, which are mainly due to the implementation of non-round electron optical elements, on the imaging process remains unclear. Based on a semi-empirical criterion, we analyze the impact of residual aperture aberrations on the quality of exit-plane waves that are retrieved from through-focal series recorded using an aberration-corrected and monochromated instrument which was operated at 300 kV and enabled for an information transfer of ∼0.05 nm. We show that the impact of some of the higher-order aberrations in retrieved exit-plane waves can be balanced by a suitable adjustment of symmetry equivalent lower-order aberrations. We find that proper compensation and correction of 1st and 2nd order aberrations is critical, and that the required accuracy is difficult to achieve. This results in an apparent insensitivity towards residual higher-order aberrations. We also investigate the influence of the detector characteristics on the image contrast. We find that correction for the modulation transfer function results in a contrast gain of up to 40%.     

GaAs半导体掺杂浓度的电反射光谱的研究

在波长300～1 100nm范围内,对GaAs进行了电反射光谱的研究。建立了电反射光谱的测试系统,并对实验和理论作了详细分析。推导了某一固定波长电反射光谱与半导体表面掺杂浓度的理论关系。并利用电反射光谱的实验曲线计算了GaAs的表面掺杂浓度,所得结果与电化学C—V的测试结果一致,其精度为5％。     

MBE法生长的调制掺杂GaAs／Al＿xGa＿（1－x）As异质结构材料的输运特性研究

采用变磁场霍尔效应方法，在低磁场（Ｂ＜０．６Ｔ）和低温（Ｔ＝７７Ｋ）条件下，研究了ＨＥＭＴ器件用调制掺杂ＧａＡｓ／Ａｌ＿ｘＧａ＿（１－ｘ）Ａｓ异质结构材料的输运特性。给出了材料电学参数（ρ、ｎ和μ）与Ｂ的依赖关系，揭示了平行电导对材料质量的影响，并对上述依赖关系作了初步的定量分析。     

基于统一混沌系统参数调制的保密通信方案

提出一类基于新近提出的统一混沌系统的参数自适应调制解调保密方案，利用Lyapunov函数方法对方案的可行性进行了证明，数值仿真实例表明了本方案的可行性；同时指出，如在保密通信装置的接收端加上一个低通滤波器（low pass fliter)，即使被携带传输的信号含有噪声也能被成功解调。     

无线通信系统中的高速传输技术

增加数据传输速率和提高频谱利用率是对现有移动通信系统提出的新的要求。文章分述了几种无线通信系统的高速传输技术,着重介绍了正交频分复用(OFDM)调制技术。     

音乐信号自适应加重网络增量调制的理论与实现

本文分析了音乐信号自适应加重网络增量调制(ΔM)的原理和适用性,从理论上推导了自适应加重网络的传递函数表达式,且描绘了音乐信号的加重曲线,并得出了在工作频率为3KHz可提高信噪比约7dB的结论。在文章的最后给出了整个自适应加重网络实现的具体框图和部分电路。     

快速1.3μm InGaAsP/InP台面边发光二极管

本文介绍了快速1.3μm InGaAsP/InP台面边发光二极管(ELED)的研制过程,通过有源区重掺Zn杂质和引进台面结构,提高了器件的调制频率,使-3dB调制带宽达500MHz,70mA电流下输出功率为130μW。     

100G比特以太网物理层标准和传输问题

为了获得超高宽带以太网的支持,介绍IEEE802.3ba工作组对100G比特以太网制定的标准,叙述应对高带宽需求发展的高速传输光纤技术,分析网络信号调制方式及其优缺点,讨论100G比特以太网信号传输的解决方法。