传感器信号的线性化处理与非线性补偿

介绍了两种对传感器输出信号进行线性化处理的方向；同时，对传感器不可避免的非线性提出了线性补偿的方法。     

一种用于补偿卫星通信信道记忆非线性的数字基带预失真技术

研究了卫星通信系统中记忆非线性信道的自适应数字基带预失真线性化技术,提出了一种基于记忆多项式的非直接学习结构的自适应基带预失真方案,给出了自适鹰算法。仿真结果表明,该方案能有效抑制带外频谱扩散,减小带内失真,降低误比特率,实现卫星通信系统中记忆非线性失真的自适应预失真。     

卫星信道中高阶APSK调制的非线性失真补偿算法

针对高阶APSK调制在卫星信道中存在有记忆非线性失真的现象,提出一种联合补偿算法,该算法充分利用APSK调制信号星座图的特点,在大幅度减小无记忆数据预失真计算量的基础上,联合非线性均衡实现对有记忆非线性卫星信道的自适应补偿.其优点是存储量和计算复杂度随调制阶数的增加变化很小.仿真结果表明,该算法能够达到有记忆数据预失真的补偿性能,且最佳工作点提高0.2 dB.     

外调制光发射机非线性补偿技术研究

讨论了外调制光传输系统中非线性补偿技术,分析了外调制光发射机存在的非线性失真问题:包括功率放大器引起的失真以及外调制器引起的失真。重点讨论了预失真补偿技术,寻找一种针对整个外调制发射机端非线性失真的补偿方案,设计出适用于外调制光发射机的预失真电路。     

改善放大器非线性失真的各种技术

本文介绍了改善放大器非线性失真指标的各种技术，包括功率回退、预失真、前馈和砷化镓等。指出了各种技术的应用场合。     

一种AM-VSB光发射机非线性失真补偿电路

本文提出一种相对简单的有线电视光发射机非线性预失真补偿电路网络,从理论分析得知,可以通过调节非线性元件的静态工作点和网络末端的放大器的增益,能使光发射机的二次失真和三次失真降低。实验测试结果表明该电路能改善CTB、CSO指标。     

微波放大器的非线性失真分析及线性化技术

针对当前第三代通信技术对微波放大器的线性度的要求,分析了微波放大器的非线性失真特性,介绍了几种提高线性化特性的技术方案,并比较了各自的优缺点。最后,基于功率回退技术研制了一个W-CDMA(Wide-Code Division Multiple Access)线性功率放大器,并给出了实验测试结果。     

中频数字预失真法改善功率放大器的非法性

对高功率放大器的失真特性进行了数学分析,描述了功率放大器三阶和五阶互调产物随工作状态不同而发生的变化。总结了常用的几种预失真线性化方法,着重详细介绍了中频数字预失真线性化方法对非线性功率放大器的校正原理和预失真电路系统设计,并通过Matlab仿真软件对设计电路进行了仿真,给出了仿真结果。对工程设计具有一定的指导意义。     

雷达接收机中的非线性失真

讨论雷达接收机在多频干扰作用下产生的互调失真和交调失真，并介绍脉冲多普勒雷达接收机中三阶互调和抑制率，无假响应动态范围，无交调失真动态范围，干扰互调抑制度和干扰交调抑制度等参数的测试方式。     

FH-MCPFSK信号的数字接收机

讨论了在跳频方式下对多进制连续相位频移键控调制(CPFSK)载波偏差和位定时 联合估计的实现方法,对Caire等人的算法进行分析基础上做了优化,在保证精度的前提下,明 显减少了计算量。实际仿真结果表明每一跳需要传输20个码元就能够较好完成位定时与载 波同步,适用于跳频软件接收机。     

Iterative receiver employing phase noise compensation and channel estimation for millimeter-wave OFDM systems

This paper proposes an iterative OFDM millimeterwave receiver employing low-complexity decision-directed phase noise compensation (DD-PNC) to alleviate degradation due to the phase noise. High bit-rate OFDM transceivers based on the single-chip Si RF-CMOS IC technology in the 60-GHz millimeter-wave band have been extensively studied for wireless personal area network (WPAN) systems, and the relatively large phase noise in the phase locked loop (PLL) synthesizer severely degrades transmission performance. The proposed OFDM receiver iterates DD-PNC and decision-directed channel estimation (DDCE) by exploiting the output of the channel decoder. DDPNC estimates the phase noise each sampling time by using the decoder output, and then it removes the estimate from a time-domain received signal. In addition, DDCE estimates a channel impulse response by using the compensated received signal. Computer simulations demonstrate that in the 64QAM modulation with the coding rate of 3/4, the proposed receiver with DD-PNC and DDCE can perfectly remove the phase noise of -85 dBc/Hz at 1 MHz offset, and that it can alleviate the degradation of the channel estimation due to the phase noise.     

信道相关对空间分集接收信号闪烁的影响

为了探究信道相关性对无线光通信中空间分集接收信号闪烁的影响,给采用空间分集接收技术的通信端的各子孔径大小与分布设计提供参考,理论推导了弱起伏条件下空间分集接收信道相关系数的表达式,给出了信道相关系数与分集接收信号闪烁的关系;数值研究了水平湍流均匀路径与整层大气湍流非均匀下行传输路径下的信道相关系数。结果表明,对于平面波,湍流非均匀路径下孔径接收时信道间存在明显的负相关特性。对于球面波,湍流非均匀路径下孔径接收时的信道相关性与湍流均匀路径情况类似,负相关特性都不明显。     

应用于TTNT信号的树形信道化数字接收机

在确定频点参数的情况下,采用信道化接收机能够准确高效地实现对跳频信号的接收,其中树形结构接收机既保证信道间具有一定独立性,同时结构灵活。将该结构应用于战术目标瞄准网络技术（TTNT）数据链信号的接收,设计了TTNT信号非均匀分布的16个跳频频点的树形多级结构数字化接收机。分析了该结构的运算量大小,并通过仿真实验验证了该结构的可行性。仿真结果表明,树形多级级联结构相对于多相离散傅里叶变换（DFT）滤波器组结构运算量有所增加,但结构灵活,能够有效地分离出TTNT不同频点的信号,实用性更强。     

A TECHNIQUE FOR MEASURING THE LINEARITY OF A LINEARLY FREQUENCY-MODULATED SIGNAL

A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.     

Holographic simulation of compensation for atmospheric wavefront distortion

An experiment is described which demonstrates the validity of the concept of compensating, by holographic techniques, for atmospheric distortions of wavefronts.     

Blind compensation of nonlinear distortion for bandlimited signals

Nonlinear distortion of bandlimited signals results in spectral spreading. This paper develops a blind nonlinear compensation method for bandlimited signals by suppressing the spectral content of the distorted signal above the original signal bandwidth by means of adaptive nonlinear filtering. The nonlinear compensator is constructed using a power series filter with adaptive coefficients. The adaptive coefficients are identified blindly by applying a least-squares criterion to the out-of-band spectral content of the nonlinear compensator output. The extraction of the out-of-band signal is efficiently performed by the discrete cosine transform. The effectiveness of the blind nonlinear compensation method is demonstrated by way of simulation examples involving periodic, colored noise, and bandlimited speech signals.     

Generalized polynomial-based receiver for the flat fading channel

This letter presents a simple polynomial predictor-based sequence detector for the Rayleigh nonselective fading channel. Unlike the polynomial predictor-based sequence detector proposed by Borah and Hart, the new receiver is not restricted to constant envelope modulation schemes. Analytical and simulated results are presented. In some instances, the proposed receiver performs within 6 dB of the equivalent maximum-likelihood sequence estimation receiver.     

大气光通信信道特性及相位补偿技术研究

大气湍流使光载波的强度和相位在空间和时间上都呈现随机起伏,从而极大地降低了激光通信系统的性能.基于大气湍流信道的特点,分析了各种湍流效应对大气激光通信系统性能的影响,介绍了自适应光学相位补偿技术在大气激光通信系统中的应用进展,特别指出基于随机并行梯度下降(SPGD)算法的自适应光学技术由于具有诸多优点,在未来的大气激光通信系统中可能有较为广阔的应用前景.     

Extended MLSE receiver for the frequency-flat, fast-fading channel

This paper develops a maximum likelihood sequence estimation (MLSE) receiver for the frequency-flat, fast-fading channel corrupted by additive Gaussian noise when linear modulations (M-ASK, M-PSK, and M-QAM) are employed. This paper extends Ungerboeck's derivation of the extended MLSE receiver for the purely frequency-selective channel to the time-selective channel. Although the new receiver's structure and metric assume ideal channel state information (CSI) at the receiver, the receiver structure can be used wherever high-quality CSI is available. The receiver is maximum likelihood for a variety of channels, including Ricean, Rayleigh, lognormal, and additive white Gaussian noise (AWGN) channels. Bounds on the receiver's bit error rate (BER) are deduced for ideal and pilot tone CSI for fast Rayleigh fading. A crude lower bound is developed on the BER of predictor-based receivers for the same channel. This paper offers insight into matched filtering and receiver processing for the fast-fading channel and shows how pilot symbols and tones should be exploited