Degradation of effective carrier-power-to-noise densityratio based on code trackingspectral sensitivitycoefficient for GNSS radio frequencycompatibilityin C band

The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.

A Novel Peak-to-Average Power Ratio Reduction Scheme via Tone Reservation in OFDM Systems

In this paper, a novel signal-to-clipping noise ratio and least squares approximation tone reservation scheme(SCR-LSA TR) is proposed to reduce the peak-to-average power ratio for orthogonal frequency division multiplexing systems. During the SCR procedure, only the element with the maximal amplitude is picked for processing, which not only decreases the algorithm complexity, but also helps to overcome the BER deterioration. With the LSA method, the amplitude of the peak-cancelling signals can approximate to that of the original clipping noise as much as possible. Through the combination of the optimization factor in the LSA method, the classic SCR method can achieve better PAPR reduction with faster convergence. Simulation results show that the proposed SCR-LSA TR scheme has less in-band distortion and smaller out-of-band spectral radiation. The BER of the proposed scheme shows a better performance especially under the 16-QAM over the additive white Gaussian noise channel.

A Multiobjective Optimization Method for Designing <i>M</i>-Channel NPR Cosine Modulated Filter Bank for Image Compression

This paper proposes a method to design multichannel cosine modulated filter bank for image compression using multiobjective optimization technique. The design problem is a combination of stopband residual energy, least square error of the overall transfer function of the filter bank, coding gain with dc leakage free condition as constraint. The proposed algorithm uses Non-dominated Sorting Genetic Algorithm (NSGA) to minimize the mutually contradictory objective function by minimizing filter tap weights of prototype filter. The algorithm solves this problem by searching solutions that achieve the best compromise between the different objectives criteria. The performance of this algorithm is evaluated in terms of coding gain and peak signal to noise ratio (PSNR). Simulation results on different images are included to illustrate the effectiveness of the proposed algorithm for image compression application.

Performance of joint dual links dynamic power control and smart antenna for TDMA/TDD cellular mobile communications

Interference cancellation is made available by using smart antenna at cellular base stations. Well distributed cumulative probability of signal to interference plus noise power ratio appears to be vital for cellular mobile multimedia communications. A scenario of dual links dynamic power control combined to a solution of smart antenna is proposed to adjust the instant transmission power in terms of the disparity from the favorite range. Simulation results show that this method is quite effective to improve the cumulative distribution probability performance. Meanwhile, accompanying low power consumption is also obtained at both base stations and mobile stations.

星载功率放大器NPR测试方法研究

针对星载功率放大器噪声功率比(noise power ratio,NPR)指标缺乏考核方法的问题,根据多载波非线性工作原理,使用基于数字I/Q调制的方法在Matlab里编辑基带波形文件,形成具有陷波的宽带多载波信号,依据频谱仪采样的数字预处理方法校准宽带多载波信号的幅度平坦度,调节矢量信号源I/Q两路的功率偏置进而调整陷波的深度来生成满足条件的宽带多载波激励信号。通过输入放大器该校正后的激励信号、分析被测放大器件输出端频谱陷波内产生的互调失真分量的测试方法,设计了通过矢量信号源和频谱仪进行测试的方案。根据方案所搭建的测试系统,完成了某K频段行波管放大器(主载波频率为19800MHz,带宽为80MHz)的测试验证。研究结果表明,提出的NPR测试方法有效可行,为考核星载微波功率放大器NPR指标提供了具体的测试方法。

Power control scheme for multiple antenna systems with space-time coding in Rayleigh fading channels

Two optimal power control （PC） schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information （CSI） are presented. One is based on the minimization of a bit error rate （BER）, and the other is based on the maximization of a fuzzy signal-to-noise ratio. In these schemes, different powers are allocated to individual transmit an- tennas rather than equal power in the conventional one. For the first scheme, the optimal PC procedure is developed. It is shown that the Lagrange multiplier for the constrained optimization in the power control does exist and is unique. A practical iterative algorithm based on Newton＇s method for finding the Lagrange multiplier is proposed. In the second scheme, some existing schemes are included, and a suboptimal PC procedure is developed by means of the asymptotic performance analysis. With this suboptimal scheme, a simple PC calculation formula is provided, and thus the calculation of the PC will be straightforward. Moreover, the suboptimal scheme has the BER performance close to the optimal scheme. Simulation results show that the two PC schemes can provide BER lower than the equal PC and antenna selection scheme under the imperfect CSI.

LOW-COMPLEXITY JOINT BEAMFORMING AND POWER ALLOCA-TION FOR SINR BALANCING IN COGNITIVE RADIO NETWORKS

We consider the Signal-to-Interference plus Noise Ratio(SINR) balancing problem in-volving joint beamfoming and power allocation in the Cognitive Radio(CR) network,wherein the Single-Input Multi-Output Multiple Access Channels(SIMO-MAC) are assumed.Subject to two sets of constraints:the interference temperature constraints of Primary Users(PUs) and the peak power constraints of Cognitive Users(CUs),a low-complexity joint beamforming and power allocation algo-rithm called Semi-Decoupled Multi-Constraint Power Allocation with Constraints Preselection(SDMCPA-CP) for SINR balancing is proposed.Compared with the existing algorithm,the proposed SDMCPA-CP can reduce the number of matrix inversions and matrix eigen decompositions signifi-cantly,especially when large numbers of PUs and CUs are active,while still providing the optimal balanced SINR level for all the CUs.

Design of multi-antenna relaying for OFDM in impulsive noise environment

A low-complexity multi-antenna relaying scheme is proposed for Orthogonal Frequency Division Multiplexing (OFDM) in the presence of Class-A Impulsive Noise (IN). One way and two way relaying are considered. The signal is transmitted and received by two terminal nodes, each with a single antenna in two time phases. In the proposed design, the processing at the relay consists of Maximal-Ratio Combining (MRC) or Power-based Selection Combining (PSC) for receive combining, Amplify and Forward (AF) for power scaling, and Space Time Block Coding (STBC) for transmit diversity. Channel State Information (CSI), Discrete Fourier Transform (DFT), and Inverse Discrete Fourier Transform (IDFT) are not needed. The Selective Mapping (SLM) technique is used at the transmitter to reduce the Peak-to-Average Power Ratio (PAPR) of the OFDM signal. Then, at the receiver, the clipping technique is used to reduce the impulses that result from the impulsive noise. The proposed system reduces the complexity of the conventional system, which uses multi-relay with a single antenna. Simulation results show that the Bit Error Rate (BER) of the proposed scheme outperforms that of the conventional scheme due to the diversity inherent in the proposed scheme.

New Wavelet Thresholding Algorithm in Dropping Ambient Noise from Underwater Acoustic Signals

Underwater Wireless Communication, largely dependent on the acoustic communication between the machines, is largely affected by various types of noise in the shallow and deep water. However ambient noise which is due to multiple sources (e.g. shipping, wind) and no one source dominates. Ambient noise masks the acoustic signal to a large extent. Hence today it has drawn the attention of the experts to reduce its effect on the received signal. This paper discusses ambient noise problem and devises a new wavelet thresholding method to reduce its effect. Afterwards a comparative study on statistical parameters is shown to prove the efficiency of the devised method.

Optimal Power Allocation Strategy for TBLAST Based 4G Systems

There is a big demand for increasing number of subscribers in the fourth generation mobile communication systems. However, the system performance is limited by multi-path propagations and lack of efficient power allocation algorithms in conventional wireless communication systems. Optimal resource allocation and interference cancellation issues are critical for the improvement of system performance such as throughput and transmission reliability. In this paper, a turbo coded bell lab space time system (TBLAST) with optimal power allocation techniques based on eigen mode, Newton and convex optimization method and carrier-interference-and-noise ratio (CINR) are proposed to improve link reliability and to increase throughput with reasonable computational complexity. The proposed scheme is evaluated by Monte-Carlo simulations and is shown to outperform the conventional power allocation scheme.

Theory of noise in a kilo-Hz cascaded high-energy Yb-doped nanosecond pulsed fiber amplifier

A theoretical analysis of noise in a high-power cascaded fiber amplifier is presented. Unlike the noise theory in low power communication, the noise of a high power system is redefined as the leaked output energy between pulses with coherent beat noise uncounted. This definition is more appropriate for high power usage in which the pulse energy receives more attention than the pulse shape integrity. Then the low power pre-amplifying stages are considered as linear amplification and analyzed by linear theory. In the high-power amplification stages, the inversion is assumed to recover linearly in the time interval between pulses. The time shape of the output pulse is different from that of the input signal because of different gains at the front and back ends of the pulse. Then, a criterion is provided to distinguish the nonlinear and linear amplifications based on the signal-to-noise ratio （SNR） analysis. Then, an experiment that shows that the output SNR actually drops off in nonlinear amplification is performed. The change in the noise factor can be well evaluated by pulse shape distortion.

基于活动性检测动态估计噪声的心音降噪算法

针对基于小波分解和最优改进对数幅度谱估计的心音降噪算法存在噪声残留和心音失真的问题,提出一种基于心音活动性检测(HSAD)动态估计噪声的心音降噪算法。通过设计的HSAD判断当前心音帧是否为基础心音帧(FHS),根据判断结果分别采用改进最小值控制递归平均(IMCRA)算法和递归平滑算法对噪声功率进行动态估计与更新,采用非因果先验信噪比,实现心音信号的降噪。实验结果表明,提出算法能更好在提升降噪性能的同时,降低FHS的失真。

基于自动增益控制的信号量化损耗分析

在卫星信号接收的过程中,量化是模数转换的重要环节,信号量化会带来能量损失,对于信号后续的处理产生影响,根据信号特性选取合适的量化位数和系统基准功率可以有效改善这种损失.本文采用量化前后信号信噪比(signal to noise ratio,SNR)对比的形式来直观表示量化损耗,并给出了一般性分析公式.说明了自动增益控制(automatic gain control,AGC)模块在信号量化中的作用,结合量化损耗公式,通过确定最佳增益系数给出了一种基准功率的选取方式,使得不同SNR的信号量化损耗明显降低.仿真结果表明:在低位量化时,该方式对卫星导航信号的量化损耗能改善约1.5 dB.该分析对于接收机的设计以及工程实现具有一定的参考意义.

基于逆全极点滤波器的高频PWM噪声整形方法

高频开关功率放大器具有高功率、低纹波、高响应的优点,是高加速、高精度定位系统的核心部件。为了解决高频PWM中开关频率与占空比分辨率的矛盾,该文分析调制中噪声整形的基本原理,采用误差反馈结构提取PWM量化噪声进行数字整形,阐述噪声整形滤波器设计约束条件。提出通过逆全极点无限脉冲响应(IIR)滤波器获得有限脉冲响应(FIR)噪声整形滤波器的简明设计方法,仿真及实验表明,该文提出的方法可利用低阶FIR整形滤波器获得平坦的通带和高整形衰减。在不足9位的PWM中,4阶的FIR噪声整形滤波器能够恢复调制信号在10 kHz频段内约40 dB的信噪比损失。

一种高PSRR超低噪声CL-LDO设计

提出了一种高电源抑制比(PSRR)超低噪声无片外电容低压差线性稳压器(CL-LDO)。采用自偏置折叠共源共栅结构的自适应误差放大器降低系统噪声;利用过温保护电阻和电流增强电阻的基准电压源结构,使电压基准源在高工作电压下具有较高PSRR;同时在电流源正温度系数支路引入一对温度系数相反的电阻,简化电流源零温度系数调节过程。该CL-LDO基于CSMC 0.18μm BCD工艺进行电路验证,该电路在输出电容为1 pF,电源电压为4.9 V~5.2 V,负载电流为200μA至90 mA条件下,可稳定提供3.3 V电压输出,电源抑制比为-44 dB@10 kHz,等效输入噪声仅为17nV/√Hz@100kHz。电源电压5 V时具有12.1μV/mA的负载调整率和4.8 mV/V的线性调整率。阶跃负载电流上升/下降时间为1μs的情况下,该CL-LDO恢复时间小于2.2μs。

基于分式二次规划的互模糊函数赋形方法

在开展认知雷达波形设计时,由于发射波形与接收滤波器的非匹配体制,互模糊函数赋形相比传统模糊函数赋形优化自由度更高。该文针对强杂波条件下微弱运动目标检测问题,以最大化信干噪比为优化准则,提出了一种联合发射相位编码序列与接收滤波器设计的互模糊函数赋形方法。在恒模约束下,优化问题被建模为二次分式规划形式;然后通过引入辅助变量,并利用共轭梯度法求解Stiefel流形空间上的最小化问题,非凸优化据此转化为恒模约束二次优化问题;通过交替循环和类幂迭代算法求得最优解。此外考虑到发射波形受硬件限制而难以实现严格恒模,该文构建了一种低峰均比约束二次优化问题模型,并利用最近邻向量法求得最优解。最后,不同参数下的仿真与实测数据实验表明,该文赋形方法相较于传统方法具有较高的信干噪比增益和收敛速度。

考虑HPSA的IRS辅助室内VLC系统光源优化

针对可见光通信(VLC)系统中接收平面光功率分布不均匀的问题,提出了一种基于混合粒子群算法(HPSA)的智能反射面(IRS)辅助室内VLC系统光源优化设计方案。以16个发光二极管(LED)的矩形和混合型布局为例,设置接收光功率方差为适应度函数,将所提出的HPSA与IRS技术相结合,对LED的位置布局、半功率角以及IRS的偏航角与滚转角进行优化。仿真对比了初始的(未经优化)、基于HPSA优化的室内VLC系统,以及基于HPSA优化的IRS辅助VLC系统的性能。结果表明,在考虑一次反射链路的情况下,与初始的VLC系统相比,采用HPSA优化的系统在两种光源布局下的接收光功率以及信噪比波动都明显降低;基于HPSA优化的IRS辅助室内VLC系统在矩形布局下对接收光功率波动的改善与基于HPSA优化的VLC系统效果相当,其在混合型布局下明显低于仅采用HPSA优化的VLC系统的光功率波动。3种可见光通信系统中,基于HPSA优化的IRS辅助VLC系统的平均接收光功率最大。此外,上述3种VLC系统采用混合型布局的平均均方时延拓展性能均优于矩形布局。研究工作对室内可见光通信系统光源分布研究具有一定参考价值。

一种低噪声、高PSRR的LDO设计

基于smic40工艺提出了一种低噪声、高PSRR的LDO,将在该LDO中,采用预放大结构,在传统误差放大器(EA)之前加入BJT预放大级,降低EA的1/f噪声,以提高LDO噪声性能。为了克服PSRR与其他诸如环路稳定性和负载能力等重要设计参数之间的权衡,提出的LDO使用带有二极管连接型的PMOS充当缓冲器,电源纹波通过晶体管的栅极,并通过NMOS缓冲器增强LDO的纹波抑制能力,PSRR改进超过40 dB。实验结果表明,该LDO实现了从10 Hz到100 kHz的RMS噪声在室温下小于2μV,液氮温度77 K下小于1μV;仿真在1 kHz时PSRR为-80 dB,100 kHz时PSRR为-44~-62 dB。

基于烟花算法的可见光通信光源功率优化方法

为了改善室内可见光通信系统接收平面光信号信噪比波动大的问题,提高可见光通信系统的整体性能,设计了基于群体优化算法——烟花算法的可见光通信系统的光源功率优化算法.该算法以无线光接收平面的信噪比因子为优化目标,优化每个LED(Light Emitting Diode)光源的发射功率,获取接收平面最优信噪比因子,有效降低光接收平面光信号波动度.结果表明,当光源数量为16个点光源时,接收平面信噪比因子比等功率的光源分布降低了45%,显著改善了接收光信号的波动幅度,从而保证不同位置点的光通信用户获得同等通信质量.该方法适用于任意数量和位置的LED光源,不受光源数量和位置的限制.对比分析发现,增加光源数量,接收平面信噪比因子更小,信噪比分布均匀性更优.

基于瞬时无功功率理论的电能质量扰动检测、定位与分类方法

提出了一种对电能质量扰动进行检测、定位、辨识与分类的有效方法。首先对含有噪声的信号进行小波去噪处理,得到信噪比较高的信号,再对去噪后的信号进行差变处理得到差变信号,通过小波去噪和信号差变法来确定扰动的位置和持续时间。将去噪后的单相电压信号通过移相?60°得到三相电压,并用三相电压代替三相电流,利用瞬时无功功率理论计算出瞬时有功,进而计算出瞬时电压幅值,根据扰动的持续时间和扰动的幅度对扰动类型进行识别。