A DECISION FEEDBACK EQUALIZER FOR NON-LINEAR CHANNELS

A Simple and useful decision feedback equalizer used for non-linear channels with severe linear distortion and mild non-linear distortion is proposed. It is a combination of a nonlinear channel equalizer based on connectionist model and a common decision feedback equalizer for linear channels. For a typical non-linear channel model it is shown that the equalization performances of the proposed equalizer are improved significantly.

Targeted tissue engineering:hydrogels with linear capillary channels for axonal regeneration after spinal cord injury

Spinal cord injury（SCI）frequently results in the permanent loss of function below the level of injury due to the failure of axonal regeneration in the adult mammalian central nervous system（CNS）.The limited intrinsic growth capacity of adult neurons,a lack of growth-promoting factors and the multifactorial inhibitory microenvironment around the lesion site contribute to the lack of axonalregeneration. Strategies such as transplantation of cells,

Blind channel identication of nonlinear folding mixing model

Signals from multi-sensor systems are often mixtures of （statistically） independent sources by unknown mixing method. Blind source separation（BSS） and independent component analysis（ICA） are the methods to identify/recover the channels and the sources. BSS/ICA of nonlinear mixing models are difficult problems. For instance, the post-nonlinear model has been studied by several authors. It is noticed that in most cases, the proposed models are always with an invertible mixing. According to this fact there is an interesting question, how about the situation of the non-invertible non-linear mixing in BSS or ICA？ A new simple non-linear mixing model is proposed with a kind of non-invertible mixing, the folding mixing, and method to identify its channel, blindly.

Sparse Recovery of Linear Time-Varying Channel in OFDM System

In order to improve the performance of linear time-varying（LTV）channel estimation,based on the sparsity of channel taps in time domain,a sparse recovery method of LTV channel in orthogonal frequency division multiplexing（OFDM）system is proposed.Firstly,based on the compressive sensing theory,the average of the channel taps over one symbol duration in the LTV channel model is estimated.Secondly,in order to deal with the inter-carrier interference（ICI）,the group-pilot design criterion is used based on the minimization of mutual coherence of the measurement.Finally,an efficient pilot pattern optimization algorithm is proposed by a dual layer loops iteration.The simulation results show that the new method uses less pilots,has a smaller bit error ratio（BER）,and greater ability to deal with Doppler frequency shift than the traditional method does.

Two-Hop Gaussian Relay Channel with Linear Relaying： Achievable Rate and Optimization Design

The relay node with linear relaying transmits the linear combination of its past received signals.The optimization of two-hop relay channel with linear relaying is discussed in this paper.The capacity for the two-hop Gaussian relay channel with linear relaying is derived,which can be formulated as an optimization problem over the relaying matrix and the covariance matrix of the signals transmitted at the source.It is proved that the solution to this optimization problem is equivalent to a "single-letter" optimization problem.We also show that the solution to this "single-letter" optimization problem has the same form as the expression of the rate achieved by Time-Sharing Amplify and Forward(TSAF).In order to solve this equivalent problem,we proposed an iterative algorithm.Simulation results show that if channel gain of one hop is relatively smaller,the achievable rate with TSAF is closer to the max-flow min-cut capacity bound,but at a lower complexity.

A Multi-Gap Multi-Channel Gas Switch for the Linear Transformer Driver

A multi-gap and multi-channel gas switch with convexo-convex discal planet electrodes was designed and investigated. Eight gaps are formed in series by a trigger electrode, six intermediate electrodes and two high voltage electrodes with a uniform gap length of 5 ram. The self breakdown and triggered breakdown performance of the switch are reported. Both the delay time and jitter decrease with the increase in the trigger voltage, switching coefficient and the decrease in the trigger isolating resistor. The delay time of the switch is about 40 ns, and the jitter is less than 2 ns when charged with 4-85 kV and triggered by a voltage pule of -75 kV. The inductance of the switch is about 30 nH.

Analysis and Comparison of Time Replica and Time Linear Interpolation for Pilot Aided Channel Estimation in OFDM Systems

This paper analyzes and compares two time interpolators, i.e., time replica and time linear interpolator, for pilot aided channel estimation in orthogonal frequency division multiplexing (OFDM) systems. The mean square error (MSE) of two interpolators is theoretically derived for the general case. The equally spaced pilot arrangement is proposed as a special platform for these two time interpolators. Based on this proposed platform, the MSE of two time interpolators at the virtual pilot tones is derived analytically;moreover, the MSE of per channel estimator at the entire OFDM symbol based on per time interpolator is also derived. The effectiveness of the theoretical analysis is demonstrated by numerical simulation in both the time-invariant frequency-selective channel and the time varying frequency-selective channel.

数据模型协同驱动的MIMO系统性能预测方法

在具有未知同频干扰和信道状态信息具有不确定性的复杂场景下,现有的多输入多输出系统的性能分析和优化方案通常会退化甚至失效。为了适应这些挑战并更好地完成网络自动调优任务,提出了一个通用的数据模型协同驱动框架,该框架是真实通信系统的数字孪生,系统性能指标由系统参数决定。为了解释所提出的框架是如何工作的,将正则化迫零预编码作为实例。该实例中,首先在模型驱动方面,使用确定性等同理论来获得系统的性能近似结果。但是,该近似结果仅在理想条件下成立,例如系统已知信道状态信息不确定度、无穷天线数和没有任何未知同频干扰。因此在数据驱动方面,使用神经网络以网络参数和近似结果为输入,来进一步推断更准确的系统性能。因为利用了模型数据双驱动方法,轻量级的神经网络具有很好的性能。数据模型双驱动的性能估计器也是该系统的数字孪生。基于该数字孪生,设计了一个信道不确定度估计的流程和算法,以快速感知信道不确定度来支持该系统的自适应优化。该流程中,系统首先以一个初始信道不确定度做信号传输,并获得系统性能指标的检测结果。随后,根据性能估计器,使用梯度投影法,以该检测结果来反推信道不确定度,纠正环境非理想因素。仿真结果验证了所提算法的有效性,该数据模型协同驱动框架对于复杂场景下多输入多输出系统的性能预测具有研究意义。

激光回馈双通道位移测量创新实验平台设计

针对激光回馈技术中多目标同步检测以提高测量效率的问题,提出了一种基于线性调频的测量通道拓展方法。在线性电流注入下,激光器输出的光频率近似线性变化;2个被测物体到激光器距离不同时,回馈信号的频谱中出现分别对应2个物体的独立谱峰,通过全相位频谱分析方法在2个谱峰处进行相位解算可以重构2个物体的运动曲线。基于Python语言构建的仿真模型和相应的双通道位移测量实验系统均证实了该方法的有效性,2个通道的位移测量相对误差小于5%。

基于分数阶傅里叶滤波的数字信道化储频

现代战场环境电磁日趋密集和复杂,各类信号相互混迭,同时各种相参雷达采用脉冲压缩技术以及相参处理方法,抗噪声和抗干扰能力大大增强,特别是采用线性调频(LFM)信号满足了雷达大威力、低截获的功能设计需求,抗干扰能力也得到提高。常规的数字储频(DRFM)采用宽带采集,在数字上对宽带信号进行调频、叠加等调制处理,在瞬时带宽内调制样式、参数是相同的,此处理方式导致瞬时带宽内多信号时,无法针对性施加不同的调制样式,以致干扰粗放、不够精确。为实现精确、有效的干扰相参脉冲压缩雷达,文中提出了采用频域子带处理与分数阶傅里叶滤波的数字信道化干扰设计,增强LFM信号去噪能力,通过DRFM技术形成假目标干扰信号,实施有效干扰。

一种面向112 Gb/s PAM4接收机的自适应均衡设计方案

提出了一种适用于超短距离(Very Short Reach,VSR)信道、面向112 Gb/s PAM4(Pulse Amplitude Modulation 4)接收机的自适应均衡设计方案。在该方案中,接收机前端利用3个连续时间线性均衡器(Continuous Time Linear Equalizer,CTLE)对信号分别在高频、中频和低频进行补偿,可变增益放大器(Variable Gain Amplifier,VGA)和饱和放大器(Saturation Amplifier,SatAmp)则用于对信号幅值的缩放。除了3个数据采样器外,引入4个辅助采样器用于进一步改善阈值自适应算法性能。同时,采用符号最小均方算法,利用接收端数据采样器和辅助采样器之间的偏移推动辅助参考电压收敛到信号星座电平,从而确保PAM4接收信号的眼图在垂直方向上3个眼睛具有相等的间隔和恒定的信噪比(Signal-to-Noise Ratio,SNR)。仿真结果表明,所提出的112 Gb/s PAM4接收机能够在损耗为15 dB的信道上实现小于10~(-12)的误码率,并且具有良好的眼图性能,其最差眼高为75 mV,眼宽为0.34 UI(Unit Interval),与传统方案相比具有显著的性能提升。

应用于中继卫星通信系统的16QAM-TCM技术研究

网格编码调制技术可以在不改变信息传输频谱带宽的条件下,改善信噪比,减少发射功率,降低误码率,其实现的方法是分割星座图形成子集,逐步增大星座图中信号点之间的最小欧氏距离。本论文在项目组自研的中继卫星通信系统仿真平台上,仿真了8PSK与16QAM-TCM两种调制技术的解调性能,仿真曲线反映了误比特率需求与所需信噪比之间的关系。仿真结果表明:(1)在理想信道条件、I/Q(Inphase/Quadrature,同相/正交)幅相不平衡、幅频特性、群时延、相位噪声、功率放大器饱和点条件下,假设误比特率需求为1E-7,16QAM-TCM技术的信噪比需求与8PSK调制技术的信噪比需求相比,分别可节省8.85 dB、9.04 dB、8.45 dB、10.2 dB、8.5 dB、14.6 dB的信噪比;(2)在非线性信道条件下,当信噪比增大时,8PSK调制技术的误比特率在1E-3数量级附近波动,不再变化;(3)假设需求的误比特率为1E-7,16QAMTCM调制技术非线性信道信噪比仿真值与理想信道信噪比仿真值相比,损失了4.8 dB。

Lattice-reduction-aided MMSE precoding for correlated MIMO channels and performance analysis

The lattice-reduction （LR） has been developed to im- prove the performance of the zero-forcing （ZF） precoder in multiple input multiple output （MIMO） systems. Under the assumptions of uncorrelated flat fading channel model and perfect channel state information at the transmitter （CSIT）, an LR-aided ZF precoder is able to collect the full transmit diversity. With the complex Lenstra- Lenstra-Lov^sz （LLL） algorithm and limited feedforward structure, an LR-aided linear minimum-mean-square-error （LMMSE） pre- coder for spatial correlated MIMO channels and imperfect CSIT is proposed to achieve lower bit error rate （BER）. Assuming a time division duplexing （TDD） MIMO system, correlated block flat fad- ing channel and LMMSE uplink channel estimator, it is proved that the proposed LR-aided LMMSE precoder can also obtain the full transmit diversity through an analytical approach. Furthermore, the simulation results show that with the quadrature phase shift keying （QPSK） modulation at the transmitter, the uncoded and coded BERs of the LR-aided LMMSE precoder are lower than that of the traditional LMMSE precoder respectively when Eb-No is greater than 10 dB and 12 dB at all correlation coefficients.

基于机理模型的热连轧板形快速控制技术

热连轧机组板形控制是一项关键的任务,它旨在解决板形变化对产品质量和生产效率的影响。针对热连轧机组板形控制过程中的板形约束变量问题,采用双因素线性插值的方法,在分析弯辊力和窜辊量对板形影响的基础上建立双因素传递系数模型和板形控制空间。首先对板形空间的插值方法进行设计,然后应用到弯辊力和窜辊量对轧制压力的传递系数模型的建立中,求出相应弯辊力与窜辊量对轧制压力的传递系数,这些传递系数可以被视为板形控制的关键参数,利用求出的传递系数基于板形调节建立轧机板形控制空间。通过对板形控制空间的求解,可在板形控制范围内实现板形的快速搜寻和弯辊力、窜动量对板形的快速控制,为热连轧机组的操作提供有效指导。该方法在解决板形控制难题上具有显著的效果,能够提高产品质量和生产效率。未来的研究可以进一步优化传递系数模型和板形控制算法,实现更加精确和自动化的板形控制。

JOINT SPACE-FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC-CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interference (MUI) in high-data-rate wireless communication systems. In this paper, the Uniform Linear Array (ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment. A joint space-frequency multiuser symbol sequence detector is developed for all active users within one macrocell without space-frequency channel estimation. Simultaneously, Directions-Of-Arrivals (DOAs) of all active users can also be estimated. By dividing the ULA into two identical overlapping subarrays, a specific auxiliary matrix is constructed, which includes both symbol sequence and DOA information of all active users. Then, based on the subspace method, performing the eigen decomposition on such auxiliary matrix, the closed-form solution of symbol sequences and DOAs for all active users can be obtained. In comparison with schemes based on channel estimation, our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity. Extensive computer simulations demonstrate the overall performance of this novel scheme.

MMIC LNA based novel composite-channel Al0.3Ga0.7N/Al0.05Ga0.95N/GaN HEMTs

A microwave monolithic integrated circuit （MMIC） C-band low noise amplifier （LNA） using 1 μm-gate composite-channel Al0.3Ga0.7N/Al0.05Ga0.95N/GaN high electron mobility transistors （CC-HEMTs） has been designed, fabricated and characterized. The material structure and special channel of CC-HEMT were given and analysed. The MMIC LNA with CC-HEMT showed a noise figure of 2.4 dB, an associated gain of 12.3 dB, an input return loss of -6 dB and an output return loss of -16 dB at 6GHz. The IIP3 of the LNA is 13 dBm at 6 GHz. The LNA with 1 μm ×100 μm device showed very high-dynamic range with decent gain and noise figure.

Optimal and suboptimal structured algorithms of binary linear block codes

The optimal and suboptimal structured algorithms of linear block codes from the geometrical perspective are represented.The minimum distance and weight property lemmas and the theorem are proved for the generator matrix.Based upon the property of generator matrix,the structured algorithms of linear block codes are demonstrated.Since the complexity of optimal structured algorithm is very high,the binary linear block codes is searched by using the suboptimal structured algorithm.The comparison with Bose-Chaudhuri-Hocquenqhem（BCH） codes shows that the searched linear block codes are equivalent on minimum distance and can be designed for more block lengths.Because the linear block codes are used widely in communication systems and digital applications,the optimal and suboptimal structured algorithms must have great future being widely used in many applications and perspectives.

Feature Conditioning Based on DWT Sub-Bands Selection on Proposed Channels in BCI Speller

In this paper, we present a novel and efficient scheme for detection of P300 component of the event-related potential in the Brain Computer Interface (BCI) speller paradigm that needs significantly less EEG channels and uses a minimal subset of effective features. Removing unnecessary channels and reducing the feature dimension resulted in lower cost and shorter time and thus improved the BCI implementation. The idea was to employ a proper method to optimize the number of channels and feature vectors while keeping high accuracy in classification performance. Optimal channel selection was based on both discriminative criteria and forward-backward investigation. Besides, we obtained a minimal subset of effective features by choosing the discriminant coefficients of wavelet decomposition. Our algorithm was tested on dataset II of the BCI competition 2005. We achieved 92% accuracy using a simple LDA classifier, as compared with the second best result in BCI 2005 with an accuracy of 90.5% using SVM for classification which required more computation, and against the highest accuracy of 96.5% in BCI 2005 that used SVM and much more channels requiring excessive calculations. We also applied our proposed scheme on Hoffmann’s dataset to evaluate the effectiveness of channel reduction and achieved acceptable results.