具有抗干扰能力的光电转换电路

光探测或光电转换在自动化、过程控制等领域中有着广泛的应用。为接收或探测信号光束或瞬时光脉冲而设计的任何一种系统几乎不可避免的都处在环境光的影响之下。这样,就存在着一个如何提高和增强系统的接收灵敏度及抗杂散光干扰能力的问题。特别是当有用的光信号比较微弱而且是一种瞬时光脉冲的情况下,这个问题更为突出。为要解决这一问题。

基于基站信息盲解调的卫星转发器干扰定位方法

基站串扰型卫星上行站干扰是一类较特殊的卫星干扰形式,采用传统的双星定位方法效果一般不佳。本文介绍一种通过解析基站小区识别码后进行位置映射的干扰定位方法,可快速、准确地完成干扰卫星上行站的定位和排查,有效解决这类特殊干扰难以定位的技术难点,本文给出的实际干扰定位案例证明了该方法的有效性。同时对于此类干扰的防范方法也给出了建议。

LTE室内分布系统干扰类问题优化分析与方法研究

LTE室内分布系统(以下简称:室分)场景作为高流量发生区,是运营商增收的重点,而针对室分系统覆盖优化是各运营商抢占的技术高地,其中高层导频污染和合路干扰问题对用户影响较大,且优化难度较高。本文通过室分干扰类问题的原理探讨,结合DAS质量对高层导频污染的影响、POI隔离度对相邻工作频段干扰优化实践,给广大网优人员提供了有效的分析解决方法。

如何排除CATV系统中的干扰

在有线电视系统中所谓干扰基本分为:随机噪声、相互调制、交扰调制、邻频干扰、同频干扰、污染干扰、天电干扰、工频干扰、户间干扰和重影干扰……总之所有图像以外的任何附加成份都是干扰,下面就几种常见而典型的干扰现象及解决方法做一些介绍。

基于全交织的Turbo码方案

根据Turbo码编码器的组成及码序列交织的原理 ,提出了一种全交织的Turbo码方案 .码距离分析表明 ,该方案能减少输出码组中最小汉明距离码字的分布 ,提高系统对突发误差的抗干扰能力 .仿真结果显示 ,采用该方案可得到 0 .5dB左右的最大编码增益 .

数学形态学在配电网故障选线中的应用

针对配电网故障选线的研究现状,提出了一种暂态选线新算法。该算法利用两结构元素并行复合形态滤波器对选线数据进行滤波预处理,然后利用形态学算子对滤波后的波形数据进行形态突变检测,由此确定故障线路。采用EMTP仿真和Matlab数据处理相结合的方法对该算法进行验证,结果表明当配电网发生单相接地故障时,该算法不受过渡电阻、故障时刻和系统运行方式变化的影响,能够准确地确定故障线路。

Sinusoidal FM Fuze's Channel Leak and Its Jamming Mechanism

Aim To get the theory base of designing FM fuze's jamming signal, its jamming mechanism was studied. Methods A sinusoidal FM fuze was analyzed in time domain and frequency domain and the concept of channel leak was presented. Results It was proved that information channel leak exists in FM fuze because of the nonlinear property of the mixer. The jamming signal was designed based on the channel leak and the jamming mechanism was analyzed in detail. Conclusion This kind of jamming signal can jam the sinusoidal FM fuzes effectively just depending on the jamming signal's feature itself. It's different from the traditional jamming way of simulating echo. Though the sinusoidal FM fuze was just analyzed, the principle is applicable to all FM fuzes. At the same time, it may be used as the reference for FM radar and communication countermeasures.

Method of Jamming C/A Code GPS Receiver

The schemes and effects of electronically jamming GPS’s C/A code receivers are studied by using CW as the narrow band jamming signal and BPSK signal modulated by Gold code which is incoherent to that adopted by GPS as the wide band one. By simulating with Monte Carlo method and programming in Matlab language, the various jamming results in terms of bit error rate under several jamming scenarios are obtained. Through analyzing the simulation results and quantitative dependences of jamming effects on the distance from jammer to GPS receiver and the jammer’s height over ground, it is concluded that jamming with wide band jammer is much more effective than that with narrow band one.

浅谈有线电视系统常见故障现象的分析与处理

以有线电视系统中常见故障为例进行分析和判断，以提高排除故障的能力和保证有线电视信号的传输质量。

面对海湾电子战的思考

在分析海湾电子战战情和教训的基础上,重新思考防空体系面对未来电子战作战及抗干扰问题的新需求,特别强调采用系统对抗的设计思想,并提出需加快研究的几个方面。

Application of pseudo-random frequency domain electromagnetic method in mining areas with strong interferences

Due to the strong electromagnetic interferences and human interference,traditional electromagnetic methods cannot obtain high quality resistivity data of mineral deposits in Chinese mines.The wide field electromagnetic method(WFEM),in which the pseudo-random signal is taken as the transmitter source,can extract high quality resistivity data in areas with sever interference by only measuring the electric field component.We use the WFEM to extract the resistivity information of the Dongguashan mine in southeast China.Compared with the audio magnetotelluric(AMT)method,and the controlled source audio-frequency magnetotelluric(CSAMT) method,the WFEM can obtain data with higher quality and simpler operations.The inversion results indicate that the WFEM can accurately identify the location of the main ore-body,which can be used for deep mine exploration in areas with strong interference.

Expression of interferon-alpha/beta receptor protein in liver of patients with hepatitis C virus-related chronic liver disease

ABM: To study the expression of interferon-alpha/beta (IFN-α/β) receptor protein in liver of patients with hepatitis C virus (HCV)-related chronic liver disease and its clinical significance. METHODS: A total of 181 patients with HCV-related chronic liver disease included 56 with HCV-related liver cirrhosis (LC) and 125 with chronic hepatitis C (CHC). CHC patients were treated with five megaunits of interferon-α1b six times weekly for the first 2 weeks and then every other day for 22 wk. The patients were divided into interferon (IFN) treatment-responsive and non-responsive groups, but 36 patients lost follow-up shortly after receiving the treatment. The expression of IFN-α/β receptor (IFN-α/βR) protein in liver of all patients was determined with immunofluorescence. RESULTS: In liver of patients with HCV-related chronic liver disease, the expression of IFN-α/βR protein in liver cell membrane was stronger than that in cytoplasm and more obvious in the surroundings of portal vein than in the surroundings of central vein. Moreover, it was poorly distributed in hepatic lobules. The weak positive, positive and strong positive expression of IFN-α/βR were 40% (50/125), 28% (35/125), 32% (40/125), respectively in CHC group, and 91.1% (51/56), 5.35% (3/56), and 3.56% (2/56), respectively in LC group. The positive and strong positive rates were higher in CHC group than in LC group (P<0.01). In IFN treatment responsive group, 27.8% (10/36) showed weak positive expression; 72.2% (26/36) showed positive or strong positive expression. In the non-responsive group, 71.7% (38/53) showed weak positive expression; 28.3% (15/53) showed positive or strong positive expression. The expression of IFN-α/βR protein in liver was more obvious in IFN treatment responsive group than in non-responsive group. CONCLUSION: Expression of IFN-α/βR protein in liver of patients with HCV-related chronic liver disease is likely involved in the response to IFN treatment.

Co-channel interference rejection for MIMO-OFDM systems

A method based on the maximum a posteriori probability （MAP） criterion is proposed to estimate the channel frequency response （CFR） matrix and interference- plus-noise spatial covariance matrix （SCM） for multiple input and multiple output orthogonal frequency division multiplexing （MIMO-OFDM） systems. An iterative solution is proposed to solve the MAP-based problem and an interference rejection combining （IRC） receiver is derived to suppress co-channel interference （CCI） based on the estimated CFR and SCM. Furthermore, considering the property of SCM, i. e., Hermitian and semi-definite, two schemes are proposed to improve the accuracy of SCM estimation. The first scheme is proposed to parameterize the SCM via a sum of a series of matrices in the time domain. The second scheme measures the SCM on each subcarrier as a low-rank model while the model order can be chosen through the penalized-likelihood approach. Simulation results are provided to demonstrate the effectiveness of the proposed method.

INTERFERENCE MITIGATING BASED ON FRACTIONAL FOURIER TRANSFORM IN TRANSFORM DOMAIN COMMUNICATION SYSTEM

The method of FRactional Fourier Transform (FRFT) is introduced to Transform Domain Communication System (TDCS) for signal transforming in the paper after theoretical analysis. The method yields optimal Basis Function (BF) by FRFT with optimal transform angle. The TDCS using the proposed method has wider usable spectrum, stronger robustness and better ability of anti non-stationary jamming than using usual methods, such as Fourier Transform (FT), Auto Regressive (AR), Wavelet Transform (WT), etc. The main simulation results are as follows. First, the Bit Error Rate (BER) Pb is close to theoretical bound of no jamming no matter in single tone or in linear chirp interference. Second, the interference-to-signal ratio J /E is at least 12dB more than that of Direct Spread Spectrum System (DSSS) under the same BER if the spectrum hopping-to-signal ratio is 1:20 in chirp plus hopping interfering. Third, the Eb /N 0(when estimation difference is 90% between trans- mitter and receiver) is about 3.5dB or about 0.5dB (when estimation difference is 10% between transmitter and receiver) more than that of theoretical result when no estimation difference un-der Pb=10-2.

Pegylated IFN-α2b added to ongoing lamivudine therapy in patients with lamivudine-resistant chronic hepatitis B

AIM： To investigate the role of pegylated-interferon （IFN）α-2b in the management of patients with lamivudineresistant chronic hepatitis B. METHODS： Twenty consecutive anti-HBe positive patients were treated with pegylated IFN α-2b （100 IJg sc once weekly） for 12 mo. There was no interruption in lamivudine therapy. Hematology, liver biochemistry, serum HBV DNA levels were detected by PCR, and vital signs were also assessed. Liver histology was assessed in some patients at entry and at wk 52 for comparison. RESULTS： Nine patients （45%） had a partial virological end-treatment response; seven patients （35%） showed complete virological end-treatment response. Eight patients （40%） showed biochemical end-treatment response. There was a trend for higher virological response rates in patients who had previously responded to IFN and relapsed compared to IFN non-responders （four out of seven patients vs none out of six patients, respectively; P=0.1）. Patients without virological endtreatment response showed significant worsening of fibrosis [median score 2 （range, 1 to 3） vs median score 3 （range, 1 to 4）], in the first and second biopsy respectively （P=0.014）, whereas necroinflammatory activity was not significantly affected. Patients with complete or partial virological end-treatment response did not show any significant changes in histological findings, possibly due to the small number of patients with paired biopsies （n = 5）. Nevertheless, after 12 mo of follow-up, only onepatient （5%） showed sustained virological response and only 2 patients （10%） showed sustained biochemical response. Two patients （10%） discontinued pegylated ]FN both after 6 mo of treatment due to flu-like symptoms. CONCLUSION： Pegylated IFNα-2b, when added to ongoing lamivudine therapy in patients with lamivudineresistant chronic hepatitis B, induces sustained responses only in a small minority of cases.

Fast Secret Key Generation Based on Dynamic Private Pilot from Static Wireless Channels

In static or quasi-static wireless channel environments, secret key generation(SKG) based on wireless channels is vulnerable to active attacks due to the openness and invariance of public pilot, especially man-inthe-middle(MITM) attacks, where attacker acts as a transparent relay to manipulate channel measurements and derive the generated keys. In order to fight against this attack, a dynamic private pilot is designed, where both private pilot and secret key are derived from the characteristics of wireless channels and private to third party. In static or quasi-static environments, we use singular value decomposition techniques to reconstitute the wireless channels to improve the randomness of the wireless channels. Private pilot can encrypt and authenticate the wireless channels, which can make channel state information intercepted by MITM attacker reduced to zero and the SKG rate close to that without attacks. Results of analysis and simulation show the proposed SKG scheme can withdraw the MITM attacks.

Indoor measurement method of smoke screen disturbance efficiency based on Gaussian diffusion model

Because of ground clutter wave interf e rence,it is difficult to measure smoke screen disturbance in the field.In this pape r,a kind of indoor measurement method of smoke screen disturbance efficiency ba sed on Gaussian diffusion model is put forward.As a characteristic,the measur ement result of smoke screen area density proves that the indoor measurement met hod of smoke screen disturbance efficiency based on Gaussian diffusion model is fea sible.

An Anti-multipath Frequency Hopped Communication Technique in Shallow-water Acoustic Channels

This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate received signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10 -4 is demonstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.

A new PMSM speed modulation system with sliding mode based on active-disturbance-rejection control

A sliding mode and active disturbance rejection control(SM-ADRC)was employed to regulate the speed of a permanent magnet synchronous motor(PMSM).The major advantages of the proposed control scheme are that it can maintain the original features of ADRC and make the parameters of ADRC transition smoothly.The proposed control scheme also ensures speed control accuracy and improves the robustness and anti-load disturbance ability of the system.Moreover,through the analysis of a d-axis current output equation,a novel current-loop SM-ADRC is presented to improve the system’s dynamic performance and inner ability of anti-load disturbance.Results of a simulation and experiments show that the improved sliding-mode ADRC system has the advantages of fast response,small overshoot,small steady-state error,wide speed range and high control accuracy.It shows that the system has strong anti-interference ability to reduce the influence of variations in rotational inertia,load and internal parameters.

IMC based robust PID controller tuning for disturbance rejection

It is well-known that the IMC-PID controller tuning gives fast and improved set point response but slow disturbance rejection. A modification has been proposed in IMC-PID tuning rule for the improved disturbance rejection. For the modified IMC-PID tuning rule, a method has been developed to obtain the IMC-PID setting in closed-loop mode without acquiring detailed information of the process. The proposed method is based on the closed-loop step set point experiment using a proportional only controller with gain K_(c0). It is the direct approach to find the PID controller setting similar to classical Ziegler-Nichols closed-loop method. Based on simulations of a wide range of first-order with delay processes, a simple correlation has been derived to obtain the modified IMC-PID controller settings from closed-loop experiment. In this method, controller gain is a function of the overshoot obtained in the closed loop set point experiment. The integral and derivative time is mainly a function of the time to reach the first peak(overshoot). Simulation has been conducted for the broad class of processes and the controllers were tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms, in order to obtain a reasonable comparison. The PID controller settings obtained in the proposed tuning method show better performance and robustness with other two-step tuning methods for the broad class of processes. It has also been applied to temperature control loop in distillation column model. The result has been compared to the open loop tuning method where it gives robust and fast response.