自动增益在CDMA系统功率控制中的应用

介绍CDMA系统中的功率控制与自动增益控制(Auto-maticGainControl,AGC),通过理论研究并结合实例,提出一种适用于CDMA系统的自动增益控制。介绍的CDMA系统中的闭环功率控制方法能有效控制移动台功率,还介绍了高精度RF功率检测器LMV225实现功率控制的实际应用。     

CDMA基站收发信机中的DAGC电路实现

介绍了一种新的数字自动增益控制算法,在FPGA中实现了CDMA系统中大动态ADC采样结果与基站所用基带调制解调芯片CSM5000的接口,并对结果进行了仿真.相对于模拟硬件电路设计的自动增益控制(AGC)而言,采用的DAGC设计方法具有控制平坦、建立时间快、电路结构简单和成本低等特点.采用DAGC省去了模拟增益控制器件的复杂调试,提高了CDMA系统的集成度和稳定性.在最终实现的电路中,性能达到了96dB的动态范围, 控制精度小于或等于0.1dB.     

基于功率控制CDMA容量优化的应用

为了克服CDMA系统的远近效应和边缘效应,解决CDMA网络容量受限的问题,采用了功率控制技术,对前向链路减小基站发射功率,对反向链路调整移动台发射功率,降低系统内的干扰水平,满足用户QoS要求,有效提高CDMA系统容量。理论阐述了功率控制技术与CDMA系统容量的关系,从系统载扰比分析入手验证了功率控制对CDMA系统容量的影响,得到了基于功率控制技术两种容量优化方法即远近控制和C/I控制。实际案例仿真结果表明,通过优化功率控制参数的方法能够有效地提升CDMA系统的容量,促使CDMA网络软容量达到最佳,为CDMA网络优化人员提供可以借鉴的思路和方法。     

CDMA系统中的一种新的自适应功率控制方法

作为第三代移动通信的关键技术之一,功率控制技术在CDMA系统中得到了广泛的应用。本文在分析传统固定步长功率控制方法缺点的基础上,提出了一种将Markov过程理论应用到功率控制中的新的自适应变步长功率控制方法。     

基于C8051F340控制的TD直放站控制方案设计

介绍一种基于C8051F340快速单片机控制的直放站设计;采用GPS同步法,按时隙功率控制,自动增益控制AGC环路,系统的非线性指标良好、抗干扰性强、可靠性高.比以功率检测的同步方法和基于特征窗搜索的同步方法实现简单,应用范围更广,可用于任何无线直放站应用场合,特别适用于干放及无线射频交换场合.     

CDMA蜂窝通信系统的容量问题

CDMA系统是干扰受限系统,其容量取决于系统内用户的相互干扰,为了不影响通话质量而使得系统容量最大化,功率控制是有效措施之一,更是系统容量最大化的基础.本文从不同角度讨论了CDMA系统的容量问题,以及功率控制对系统容量的影响.仿真表明,CDMA系统容量在无衰落和有衰落环境下差异较大,有效的功率控制技术不但能够大大降低系统干扰,还能很好地提高系统容量.     

τ指数距离驱动功率控制在CDMA中研究

简要阐述了CDMA通信系统的特点和功率控制的作用,提出了τ指数距离驱动功率控制算法.该算法根据用户距基站距离的不同,收发信号采用不同的功率,从而使小区内所有用户享有均匀服务.在其基础上对CDMA蜂窝通信系统的下行链路进行理论的分析,结果表明:采用τ指数功率控制的系统比没有采用功率控制的系统,其容量至少提高三倍.     

雷达接收机噪声系数分析仪中测试辐射计设计

介绍了雷达接收机噪声系数分析仪噪声系数Y因子测量法,详细阐述了噪声接收模块测试辐射计的设计思路和实现方法,通过控制中频衰减器实现了增益自动调整功能,有效地利用了测试辐射计的检波线性区,增加了系统的测量动态范围.实验证明,测试辐射计具有自动增益调整功能且功率检波具有严格的线性特性.     

CDMA中的功率控制

本文对DS-SS CDMA蜂窝移动通信中的功率控制问题进行了分析。在对信号传输的信道因素的分析基础上,针对频分双工(FDD)和时分双工(TDD)两种不同系统的特点,分别提出了两种功率控制方案,从而扩大了系统容量,改善了系统性能。     

数字闭环自动增益控制系统设计与实现

提出了一种针对语音信号处理的数字闭环自动增益控制(Automatic Gain Control,AGC)系统的设计,详述了数字闭环自动增益控制原理、电路设计与实现.设计中采用一款适用于语音信号处理的低噪声增益可编程放大器(DS4420),FPGA(EP1C3T100C6)通过I2C总线与其连接实现闭环控制.FPGA实时检测放大器输出,通过实时运算,能够有效控制放大器DS4420的增益,实现自动增益控制.针对自动增益控制算法中的对数等复杂运算,文中采用适合于FPGA的CORDIC算法进行简化运算,把复杂的对数运算简化为只包含移位和加减法的简单运算,不仅极大地降低了运算量,同时还保证了很高的精度.该数字闭环AGC系统具有较高的动态范围(60dB),并且自动增益控制算法简单有效,具有运算量小、控制灵活的特点,在实时系统中能够快速有效地完成自动增益控制的功能.通过实验验证分析,该设计能够根据输入语音信号的大小快速有效地调整放大器增益,有很好的工程实用性.     

Parameter validity control in process control systems

Possibility of identifying the (explicit and implicit) invalidity in sensors’ indications within the process control systems (automatic control systems for industrial processes) is considered, on the basis of statistical data on industrial processes provided by the control system; the data is represented in the form of simulation model with interval validity estimates of the parameters. In the designed model, validity identification includes verifying all the functional relations specified for the selected industrial process. The issue of implementing the suggested model is studied subject to process control systems in the energy sector.     

Minimizing control variation in nonlinear optimal control

In any real system, changing the control signal from one value to another will usually cause wear and tear on the system’s actuators. Thus, when designing a control law, it is important to consider not just predicted system performance, but also the cost associated with changing the control action. This latter cost is almost always ignored in the optimal control literature. In this paper, we consider a class of optimal control problems in which the variation of the control signal is explicitly penalized in the cost function. We develop an effective computational method, based on the control parameterization approach and a novel transformation procedure, for solving this class of optimal control problems. We then apply our method to three example problems in fisheries, train control, and chemical engineering.     

网络控制系统中的时戳预测函数控制

传统预测函数控制算法不能有效处理网络控制系统中的随机延迟,为此提出了时戳预测函数控制算法.该算法使用时间戳来估计由网络引入的控制延迟,在预测系统未来输出时明确考虑了该延迟,然后借鉴传统预测函数控制算法的基本策略,得到了适用于网络控制系统的控制规律.进一步由TrueT im e工具箱搭建了网络控制系统仿真平台,对比了时戳预测函数控制算法和传统预测函数控制算法.仿真结果表明随着网络引入延迟的增大,时戳预测函数控制算法给出控制品质明显优越于传统预测函数控制算法.     

在连续控制系统中实现断续的前馈补偿控制

采用以时间最优为指标的断续控制器作为系统的前馈 ,根据对象状态的条件 ,判断和变换断续控制器的作用 ,补偿连续控制器的控制值。这种连续控制与断续控制混合的控制系统 ,把 PID控制器与对设定值变化及对干扰抑制实现快速控制的邦 -邦控制器结合起来 ,能够快速地实现系统动态调节 ,且超调量小 ,并克服了由于控制器硬件的某些限制 ,不能较大范围改变控制信号的缺陷 ,在实际过程控制中达到了很好的动态和稳态响应。     

Multiple time-scale decomposition in cheap control problems--Singular control

A linear quadratic regulator problem where a small parameter μ²multiplies the control cost is considered. Asmu rightarrow 0, it exhibits a dynamic behavior with multiple time-scales, whereas formu = 0, it is a singular control problem. At first a multiparameter singularly perturbed model of the given problem is constructed by transferring the singularity that exists in the performance index to the dynamic equations. Then the problem is decomposed into several subproblems of minimal order, each pertaining to only one time-scale. The method developed permits under a single framework the characterization of asymptotic behavior of optimal closed-loop poles, state and control trajectories, performance index, and optimal transfer function asmu rightarrow 0. Moreover, the asymptotic solution brings into focus 1) the nature of singular control and its connection to transmission zeros and 2) the presence of various types of impulses and other higher order distributions in both state and control. The approach unifies and extends significantly several ideas previously somewhat disjoint.     

The effects of redundant control inputs in optimal control

For a stabilizable system, the extension of the control inputs has no use for stabilizability, but it is important for optimal control. In this paper, a necessary and sufficient condition is presented to strictly decrease the quadratic optimal performance index after control input extensions. A similar result is also provided for H ₂ optimal control problem. These results show an essential difference between single-input and multi-input control systems. Several examples are taken to illustrate related problems.     

Compensation for control packet dropout in networked control systems

With the integration of communication networks and distributed control in modern manufacturing and process industries, networked control systems (NCSs) are becoming increasingly important due to its simplicity, scalability, flexibility, and cost effectiveness. However, there are still significant technical barriers that limit the applications of NCS technologies. Two challenges are network-induced time delay and data packet dropout. Applying a real-time queuing protocol that we developed recently, we are able to limit the sum of the network-induced communication delay and the control computation delay within a control period. This one-period delay is further guaranteed by well designed compensation for control packet dropout. Then, this paper proposes to compensate for the control packet dropout at the actuator using past control signals. Three model-free strategies for control packet dropout compensation, namely, PD (proportional plus derivative), PD2 (proportional plus up to the second-order derivative), and PD3 (proportional plus up to the third-order derivative) are developed. They are suitable for a large number of NCSs without the need to tune the compensator parameters. The proposed dropout compensation schemes are demonstrated through numerical examples.     

Predictive control and scheduling codesign in network control systems

A codesign approach combining predictive control compensation and network scheduling is presented in this paper to overcome the adverse influences of stochastic time delays and packet losses encountered in network-based real-time control systems. The state estimation and control prediction compensation algorithms are used for the random network delays in the feedback and forward channels, and the stability criteria are analyzed. The proper sampling rate is given with network scheduling to meet the desired system performance, while the network-induced delay is tolerated. Simulations show that the codesign approach works well with the bounded network delay.