高速数字微波传输中的多电平调制技术

多电平调制是在高速数字微波传输中实现频带有效利用的最关键技术之一。本文首先从近代信息传输的信号设计角度出发,论述功率、频带利用性能最为优良的两大类多电平调制方式,即ND-MAPK(N维-M阻平振幅相位键控)和MCPFSK(M电平连续相位频移键控)。作为2D-MAPK特例的M电平QAM方式,具有装备简单,且性能接近最优信号结构的基本特点,因此在数字微波中继传输中获得了广泛的应用。本文将以16电平至256电平的QAM调制系统为例,介绍其调制解调器硬件的一般构成,高速多电调制技术的应用前景及发展趋向。     

LDPC编码AMC-OFDM系统中的两种MCS选择准则

该文提出低密度奇偶校验(LDPC)码的自适应调制编码正交频分复用(AMC-OFDM)系统,并详述了该系统的原理。针对传统AMC系统中调制编码方案(MCS)的选择准则对性能提升有限的问题,提出可用于该AMC系统的两种MCS选择准则,根据接收到的所有单元信号的后验SNR确定相应自适应块采用的MCS。文章分析了这两种准则的吞吐量性能。仿真结果表明,把这两种准则应用于LDPC编码的AMC-OFDM系统中,能够带来比传统选择方法更高的吞吐量。     

直接调制光发送机调制电平控制系统调制电平的选择和系统稳定性

光发送机中的激光器调制电平自动控制系统,用于抑制输入射频电平的波动,使激光器入口有一个稳定的调制电平值,这个值应使激光器输出光波中的非线性失真和载噪比达到较好的水平。本文根据自动控制理论,讨论激光器调制电平自动控制系统的设计依据和动态分析方法,说明系统产生不稳定的原因及解决方案。     

几种数字调制方式的仿真与分析

提出了一种数字调制系统仿真平台的设计方法。针对数字调制系统中五种常见的调制方式,基于Matlab将各个环节对调制性能的影响及仿真模型的可靠性进行了跟踪分析;最后利用图形用户界面（GUI）功能设计了一个仿真系统,比较了各种调制方式的性能,仿真结果与理论值比较接近。     

自适应调制的MCS新准则及其应用

为了解决传统调制编码方案(MCS)选择准则对于性能提高的有限性,文章提出了一种新的MCS选择准则,并将其应用到自适应调制编码(AMC)的长期演进(LTE)系统.新准则用加权后的信噪比(SNR)为AMC系统确定合适的MCS.仿真结果表明,当吞吐量为2.8 bit / symbol时,新准则能够比两步预测准则带来2 dB的好处.将新准则应用到AMC-LTE系统,不仅在保证误码率(BER)性能的情况下补偿了由于信道时变引起的性能下降,而且也最大化了系统吞吐量.     

应用于滚动轴承分布式状态监测诊断系统的无线数据通信系统

为了克服有线数据传输的局限性,提出了采用无线数据传输方式实现滚动轴承监测诊断系统中上、下位机之间的数据传输。该无线数据通信系统采用二次调制/解调方案,主要包含2FSK调制/解调电路、无线发射/接收模块、电平转换电路。该系统结构简单,传输可靠,体积小,应用范围广。实验证明,该无线数据通信系统传输可靠,完全满足设计要求。     

MIMO系统探通一体化信号矩阵设计方法

由于多输入多输出(MIMO)系统具有波形、空间分集和多路复用等优势,MIMO探通一体化(DFRC)系统通过共享软硬件资源以同时实现目标探测和保密通信功能受到了极大关注。该文针对基于预编码矩阵调制的MIMO探通一体化系统,提出了基于交替方向乘子(ADMM)的一体化信号矩阵设计方法。通过用户和窃听用户参考密码本约束下最大化方向图峰值主瓣旁瓣电平比(PMSR),保证了探测方向图性能的同时防止通信信息被窃听。针对预编码矩阵通信解调问题,提出了基于交替方向惩罚(ADPM)的排序学习优化解调方法,提升了一体化波形信息解调效率。数值仿真验证了所提设计方法实现探通一体化的有效性,与已有算法相比可实现多用户通信和更高的PMSR。     

全数字音频功率放大器的噪声成形和脉宽调制

文章提出了用数字脉冲宽度调制和内插噪声成形技术将数字声音信号直接转换为模拟功率信号的方法,讨论了采用这种方法的数字功放的性能模拟结果。结合原型机设计参数的选取分析了简单的三阶系统。     

多电平PAM系统的最佳均衡理论

详细论述了多电平ＰＡＭ（脉冲幅度调制）系统的最佳均衡理论。首先建立了多电平ＰＡＭ系统的一种二进制码间干扰等效模型，将之视为二进制多路系统，从而说明其均稀可以用多个独立的二进制均衡器联事完成。在将均衡问题视为分类判决问题的基础上，根据贝叶斯准则导出了多电平ＰＡＭ系统的最佳均衡有达式和所能取得的最小符号概率的计算公式和近似计算公式。从最佳均衡解可以看到，无论是二进制通信系统还是多电平ＰＡＭ系统，其最佳     

不可信无线中继网络中基于用户选择的安全通信研究

该文研究在不可信解码转发无线中继网络中,基于用户选择的安全通信策略与性能分析.根据直接链路与中继链路的信道增益,本文提出三种不同的选择准则以提升系统的安全性;文章推导了三种选择准则下安全截断概率的闭式解析表达式及渐近表达式.根据渐近表达式和数值仿真结果可知,次优准则可以达到与最优准则几乎相同的系统安全性能.同时部分选择准则也能达到全分集增益性能.     

Nature-Based Design of Aperiodic Linear Arrays with Broadband Elements Using a Combination of Rapid Neural-Network Estimation Techniques and Genetic Algorithms

The developments presented in this paper address the challenge of determining the optimal element positions in nonuniformly spaced broadband phased-array antennas in order to best meet desired performance criteria. Specifically, this is accomplished by introducing a new nature-based design technique that couples a robust genetic-algorithm (GA) optimizer with rapid neural-network (NN) estimation procedures. These provide performance criteria as functions of the element positions over the entire scanning range and bandwidth of operation. The objective of this GA-NN technique is to determine the optimal element positions for a broadband aperiodic linear phased-array antenna in order to minimize element VSWRs and sidelobe levels. The NN estimation procedures circumvent the need for computationally intensive full-wave numerical simulations during the optimization process, which would ordinarily render such an optimization task impractical. The effectiveness of the new GA-NN design synthesis technique is demonstrated by considering an example where a nonuniformly spaced linear phased array of ten stacked patch antennas is optimized for operation within a given bandwidth and scanning range.     

雷达伺服系统二次优化设计及仿真

提出了一类新型非线性控制器和二次优化控制系统大相角裕量设计法，应用这些结果对线性优化系统进行优化，可以获得性能指标比原系统好得多的二次优化系统，文中给出用大相角裕量二次优化设计法来设计大型雷达伺服系统的实例，计算机仿真校验其性能指标的结果表明，二次优化系统的性能指标确经线性优化系统好。设计方法简便，通用，适用于工程设计。     

New Model for Synthesis of Symmetrical Thinned Linear Arrays

In symmetrical thinned linear arrays design, the positions of thinned array elements are very important for optimal performance in terms of its minimum peak side lobe level (Msll). For the synthesis of thinned arrays with a given thinning rate, it would have almost the same Msll solution between taking only segmental aperture nearby both ends of the aperture into account and taking all the aperture into account. In this paper, the element distribution characteristic over the aperture of many optimum thinned arrays is studied, then the aperture release model is founded by the least square method to synthesize the thinned arrays. This model is vital for the computing burden alleviation and the efficiency optimization, and would hardly bring any degradation of the obtained array performance.     

New Model for Synthesis of Symmetrical Thinned Linear Arrays

In symmetrical thinned linear arrays design, the positions of thinned array elements are very important for optimal performance in terms of its minimum peak side lobe level （Msli）. For the synthesis of thinned arrays with a given thinning rate, it would have almost the same Msll solution between taking only segmental aperture nearby both ends of the aperture into account and taking all the aperture into account. In this paper, the element distribution characteristic over the aperture of many optimum thinned arrays is studied, then the aperture release model is founded by the least square method to synthesize the thinned arrays. This model is vital for the computing burden alleviation and the efficiency optimization, and would hardly bring any degradation of the obtained array performance.     

A locally optimal handoff algorithm for cellular communications

The design of handoff algorithms for cellular communication systems based on mobile signal strength measurements is considered. The design problem is posed as an optimization to obtain the best tradeoff between the expected number of service failures and expected number of handoffs, where a service failure is defined to be the event that the signal strength falls below a level required for satisfactory service to the subscriber. Based on dynamic programming arguments, an optimal solution is obtained, which, though impractical, can be used as a benchmark in the comparison of suboptimal schemes. A simple locally optimal handoff algorithm is derived from the optimal solution. Like the standard hysteresis algorithm, the locally optimal algorithm is characterized by a single threshold. A systematic method for the comparison of various handoff algorithms that are akin to the receiver operating characteristic (ROC) curves of radar detection is presented. Simulation results show that the locally optimal algorithm outperforms the hysteresis algorithm, especially in situations where accurate prediction of signal strength is possible. A straightforward technique for adapting the locally optimal algorithm to changing environments is suggested. That natural adaptability is the algorithm's principle advantage over current approaches     

Optimal FIR Filter Design based on Curve Fitting Approximation for Uncertain 2–1 Sigma–Delta Modulator

Uncertain components in the integrators of 2–1 Sigma–Delta modulators cannot eliminate the first stage quantization noise completely, and the signal-to-noise ratio in analogue-to-digital converters is not reduced perfectly either. In order to solve the matching problem, older filter designs based on convex optimization are mathematically complicated, computationally intensive and not so efficient in application. In this paper, we propose a design method based on curve fitting approximation for uncertain linearized model of the modulator which is simple in principle and practical in application. Simulation results show that the optimal filter has better performance on multiple validations when compared to other modulator filters.     

半桥串并联谐振变换器的分析与设计

详细介绍了串并联谐振变换器(LCC型)在f_s>f_r下的工作原理,根据等效电路给出了稳态分析及最佳设计原则。最后以100kHz半桥ZVS-SPRC实验电路为例,给出了简单设计步骤、实验结果及相关波形。     

Optimal Antenna Radiation Characteristics for Diversity and MIMO Systems

This paper proposes a method for determining the antenna element radiation characteristics that maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the radiated power and allowable level of supergain. The discussion also focuses on how the resulting radiation characteristics approximately optimize average capacity for multiple-input multiple-output communications. Computational results reveal that optimal antenna characteristics can provide significantly more diversity gain than that offered by the characteristics of a simple design. An example computation using genetic algorithm optimization demonstrates that a numerically optimized practical design can be designed whose performance is relatively close to that of the optimal array.      

火炮随动系统多目标优化控制

给出了采用X-Q自适应控制器构成的一类非线性控制器以及实现多目标优化控制系统的计算机辅助设计参数寻优方法,讨论怎样应用X-Q自适应控制器实现多目标优化控制,并给出实现多目标优化火炮随动控制系统的实例,计算机仿真校验其性能指标的结果表明,多目标优化系统的性能指标好,设计方法简单、通用、适用于工程设计。     

磁测量记录和数据图形显示系统设计

分析研究磁测量仪器的工作原理,选用RS485串口,根据多机通信的原理,设计一款性价比较高的磁测量记录系统。对测量各种物理量的分仪器控制、操作、数据测量、数据传送,从而达到在计算机上多维物理量测试并图表显示。经测试此系统操作简便、性能可靠。