A high frequency vibration compensation approach for ultrahigh resolution SAR imaging based on sinusoidal frequency modulation Fourier-Bessel transform

Ultrahigh resolution synthetic aperture radar(SAR)imaging for ship targets is significant in SAR imaging,but it suffers from high frequency vibration of the platform,which will induce defocus into SAR imaging results.In this paper,a novel compensation method based on the sinusoidal frequency modulation Fourier-Bessel transform(SFMFBT)is proposed,it can estimate the vibration errors,and the phase shift ambiguity can be avoided via extracting the time frequency ridge consequently.By constructing the corresponding compensation function and combined with the inverse SAR(ISAR)technique,well-focused imaging results can be obtained.The simulation imaging results of ship targets demonstrate the validity of the proposed approach.

High order single step time delay compensation algorithm for structural active control

The optimal instantaneous high order single step algorithm for active control is first discussed and then, the n+1 time step controlling force vector of the instantaneous optimal algorithm is derived from way of n time state vector. An estimating algorithm, is developed from this to solve the problem of active control with time delay compensation. The estimating algorithm based on this high order single step β method (HSM) foundation, is proven by simulation and experiment analysis, to be a valid solution to problem of active control with time delay compensation.

Modeling of high permittivity insulator structure with interface charge by charge compensation

An analytical model of the power metal–oxide–semiconductor field-effect transistor(MOSFET)with high permittivity insulator structure(HKMOS)with interface charge is established based on superposition and developed for optimization by charge compensation.In light of charge compensation,the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage(BV)and minimizing specific ON-resistance(R_(on,sp)).From this optimization method,it is very efficient to obtain the design parameters to overcome the difficulty in implementing the R_(on,sp)–BV trade-off for quick design.The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region,the extraction of the parameters is qualitatively and quantitatively optimized for trading off BV and Ron,sp with JFET effect taken into account.

STEERABLE ANTENNAS MOVEMENT COMPENSATION FOR HIGH ALTITUDE PLATFORM

High Altitude Platform(HAP) must compensate for relative motion with respect to the ground because of the stratosphere complexity,which is important to guarantee Quality of Service(QoS) in intended coverage area.With analysis on HAP movement models for predicting the geographical coverage in the cases of shift horizontally and vertically,yaw,roll and pitch,the mechanisms of steerable antennas movement compensation are investigated.The mechanism is applied to a scenario of 127 cell architecture,with a cell cluster size of four.By the simulation results of Carrier to Interference Ratio(CIR),the steerable antenna movement compensation mechanism decrease influence of HAP movement and guarantee effective coverage of the service area.

Pre-Compensation for Continuous-Path Running Trajectory Error in High-Speed Machining of Parts with Varied Curvature Features

Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.

RESEARCH ON MOTION COMPENSATION FOR HIGH RESOLUTION PROFILE OF EXTENDED TARGET FOR STEPPED CHIRP RADAR AND DSP IMPLEMENTATION

A discrete model is set up for High Resolution Range Profile (HRRP) of an extended target and the model of echo from an extended target for a Stepped Chirp Radar (SCR) is proposed. The effect of target motion on a range profile is thoroughly analyzed, and based on which precision re- quirement is developed for motion compensation. By studying the time domain correlation and the rule based on the least burst error, a motion compensation algorithm which satisfies the project requirement is presented, and the cyber-emulation confirms the conclusion. At last the processor is designed by using DSP devices to realize motion compensation and target recognition.

High Speed Column-Parallel CDS/ADC Circuit with Nonlinearity Compensation for CMOS Image Sensors

A high speed column-parallel CDS/ADC circuit with nonlinearity compensation is proposed in this paper.The correlated double sampling (CDS) and analog-to-digital converter (ADC) functions are integrated in a threephase column-parallel circuit based on two floating gate inverters and switched-capacitor network.The conversion rate of traditional single-slope ADC is speeded up by dividing quantization to coarse step and fine step.A storage capacitor is used to store the result of coarse step and locate the section of ramp signal of fine step,which can reduce the clock step from 2 n to 2 (n/2+1).The floating gate inverters are implemented to reduce the power consumption.Its induced nonlinear offset is cancelled by introducing a compensation module to the input of inverter,which can equalize the coupling path in three phases of the proposed circuit.This circuit is designed and simulated for CMOS image sensor with 640×480 pixel array using Chartered 0.18μm process.Simulation results indicate that the resolution can reach 10-bit and the maximum frame rate can reach 200 frames/s with a main clock of 10MHz.The power consumption of this circuit is less than 36.5μW with a 3.3V power supply.The proposed CDS/ADC circuit is suitable for high resolution and high speed image sensors.

Seismic energy dispersion compensation by multi-scale morphology

Seismic energy decays while propagating subsurface, which may reduce the resolution of seismic data. This paper studies the method of seismic energy dispersion compensation which provides the basic principles for multi-scale morphology and the spectrum simulation method. These methods are applied in seismic energy compensation. First of all, the seismic data is decomposed into multiple scales and the effective frequency bandwidth is selectively broadened for some scales by using a spectrum simulation method. In this process, according to the amplitude spectrum of each scale, the best simulation range is selected to simulate the middle and low frequency components to ensure the authenticity of the simulation curve which is calculated by the median method, and the high frequency component is broadened. Finally, these scales are reconstructed with reasonable coefficients, and the compensated seismic data can be obtained. Examples are shown to illustrate the feasibility of the energy compensation method.

Optimal Reactive Power Compensation of Distribution Network to Prevent Reactive Power Reverse

The capacitive reactive power reversal in the urban distribution grid is increasingly prominent at the period of light load in the last years.In severe cases,it will endanger the security and stability of power grid.This paper presents an optimal reactive power compensation method of distribution network to prevent reactive power reverse.Firstly,an integrated reactive power planning(RPP)model with power factor constraints is established.Capacitors and reactors are considered to be installed in the distribution system at the same time.The objective function is the cost minimization of compensation and real power loss with transformers and lines during the planning period.Nodal power factor limits and reactor capacity constraints are new constraints.Then,power factor sensitivity with respect to reactive power is derived.An improved genetic algorithm by power factor sensitivity is used to solve the model.The optimal locations and sizes of reactors and capacitors can avoid reactive power reversal and power factor exceeding the limit.Finally,the effectiveness of the model and algorithm is proven by a typical high-voltage distribution network.

Reliability Design and Simulation of a Surface-Mount Temperature Compensation Crystal Oscillator

This paper introduces the structure and principle of a surface-mount high-precision temperature compensation crystal oscillator,and specifically describes the reliability design of a quartz-crystal resonator used inside the surface-mount temperature compensation crystal oscillator,the reliability design of surface-mount ceramic base and the reliability design of hybrid micro-assembly.Finally,the thermal and mechanical simulation results and the experimental verification of this surface-mount temperature compensation crystal oscillator are provided,which prove that this crystal oscillator has high reliability.

一种低温度系数高阶补偿基准电压电路设计

基准电压对模拟系统的性能与精度有着至关重要的影响.一般的曲率补偿仅能消除与温度相关的二阶项,难以满足某些电路对高精度的要求.现有的电路存在温度系数较高的问题,亟须对更高阶进行补偿.本文提出了一种新的高阶曲率补偿方法,通过利用CMOS晶体管亚阈值特性设计,成功实现了一种低温度系数电压基准电路.该方法首先利用两个不同温度系数的电流流过相同的亚阈值区CMOS晶体管,产生两个具有不同温度特性的栅源电压.然后,通过对这两个不同温度特性的栅源电压进行相减,产生对数电压,并与一阶补偿电压进行加权叠加,从而实现高阶补偿.为了提高电源抑制比(PSRR),该电路采用了高增益负反馈回路,避免了传统电压基准电路中放大器的使用,进一步地降低了功耗.本设计基于0.18μm CMOS工艺,在Cadence软件下完成电路设计、版图设计与仿真验证.仿真结果显示,该电路正常工作电压范围为1.6~3 V,在2 V的工作电压下,基准电压输出295 mV,在-45~125℃范围内温度系数为1.26 ppm/℃,PSRR为51.1 dB@1 kHz,最大静态电流为8.9μA.结果表明,该基准电压电路能够满足高精度集成电路系统的需求.

一种改进的基于惯导运动补偿的实时成像方法

合成孔径雷达(SAR)作为一种主动式的对地微波遥感技术,具有全天候、全天时和远距离的特点。通过发射大带宽信号,获得距离向的高分辨。通过平台相对静止场景的运动形成合成孔径,获得方位向的高分辨,SAR平台的运动是成像的基本条件。对于机载SAR,由于载机在大气中飞行时受到大气湍流等因素的影响,不可能保持理想的运动状态,必然会产生运动误差,运动误差会导致相位误差和包络移动,从而导致图像散焦等问题。如何对SAR进行运动补偿是实现成像的关键。基于惯导数据的运动补偿是实现高分辨成像的重要手段之一。根据惯导数据的特点,结合卡尔曼滤波原理和SAR成像的几何模型,提出了一种基于卡尔曼滤波的惯导数据滤波和重采样方法。该方法可以有效剔除运动参数野值,精确地获得雷达平台的运动参数。文中所提出的运动补偿方法能和SAR成像算法很好的结合,实测数据的成像结果验证了该方法的准确性和有效性。

电压自校准的高精度多通道应变信号采集模块

针对现有应变采集设备存在采集精度低、测量范围窄、通道数较少、校准繁琐等问题,设计了一种具备电压自校准的高精度多通道应变信号采集模块,模块以高精度模拟调理转换电路为核心,结合电子线路噪声理论仿真与分析,由自校准电路对采集通道进行校准,通过补偿远端传输线的激励电压,实现了48通道大应变信号与差分电压信号的高精度测量。测试结果表明:应变信号测量范围可达±100000με,测量精度优于0.05%FS;电压信号测量范围可达±15 V,测量精度优于±(0.025%RD+500μV),准确度高,具备较好的稳定性和通用性。

高海拔潮气量双环PID控制系统研究

为解决高海拔地区气压降低导致急救呼吸机潮气量控制精度下降的问题,提出了双环PID潮气量控制系统。该系统采用气压补偿型PID控制器调整风机转速,并辅以积分分离式PID控制器,以实现对气流速度的精确控制。在实际海拔4370 m、大气压59 kPa的环境中,系统性能测试表明,相较于单环PID控制,双环控制系统在高海拔条件下表现出快速响应和无超调的卓越性能。平均气流速度输出误差为3.19%,最大误差为4.1%,优于现有临床设备的准确性。这一技术突破不仅提供了高海拔急救呼吸机潮气量控制的有效解决方案,也为特殊环境下的通气控制技术发展贡献了重要参考。

薪酬税收激励与劳动收入份额

我国推动企业高质量发展的税收优惠政策多数偏向资本要素,而激励使用劳动要素的较少。前者通常不利于提升劳动收入份额,后者的影响又如何呢?对此,本文基于2008年薪酬抵税改革运用双重差分实证分析。研究发现:薪酬税收激励能提升劳动收入份额,在样本均值处约上升4.62%。该政策促进企业提高薪酬待遇,且普通员工受益大于管理层,并且对企业效率和效益均有正向影响。综合来看,此类税收优惠政策能更好兼顾高质量发展和共同富裕,践行“在高质量发展中促进共同富裕”宜更多运用。

高速精确的光纤光栅信号解调方案设计

为提升光纤光栅的应用效果,为此,设计高速精确的光纤光栅信号解调方案。依据LPFG的光纤光栅信号解调原理,设计两个LPFG双边缘滤波器处理两路反射光,并且利用光电探测器探测光功率结果,以此解调光栅的中心波长;采用光纤干涉仪检测解调频率,对其进行正反扫描,依据光传播时延引起的解调误差和解调频率扫描方向之间的关联,完成解调结果补偿。测试结果显示:该方案具有较好可行性,光谱发生不同程度重叠时,光纤光栅信号的解调结果标准差均小于1.85 pm;光栅波长的解调误差均在-5~5 pm之间;有效降低解调误差,提升光纤光栅解调精度,可靠获取信号中的信息。

基于高频正交方波注入法的永磁同步电机控制研究

针对传统高频注入法解调过程复杂和观测精度受非理想因素时延影响的不足,提出一种基于高频正交方波注入法的零低速位置估计方法。首先,考虑估计旋转轴系注入的低可靠性,选择将高频信号注入静止轴系,采用简单代数运算提取出高频响应电流,通过解调正向虚拟高频响应电流初步估计转子位置;然后,针对主要非理想因素进行影响分析,在此基础上,通过解调负向虚拟高频响应电流提取出相位滞后角,完成补偿;最后,为避免启动阶段位置收敛错误,通过获取电感变化趋势判断出磁极极性。实验结果表明,所提算法在各类工况均能稳定收敛,且最大平均误差不超过1°,说明了算法的抗扰性以及准确性。

双极化复用信号的接收技术研究

针对双极化复用传输系统的交叉极化干扰问题,提出一种适用于双极化复用信号的接收技术。在接收链路本振不同源的情况下,参考信号与干扰信号载波频率不同,干扰不能被对消。从理论上推导了参考信号与干扰信号之间的频率关系,并通过频率补偿模块消除参考信号与干扰信号间的频差,使得参考信号与干扰信号频率一致,从而实现极化干扰对消。测试结果表明,链路本振不同源的情况下,该方法可有效减少交叉极化干扰带来的误码率恶化。

地铁气体灭火系统气瓶微变形监测技术研究

市场上使用的部分消防气瓶已远超年限,存在潜在的安全隐患,容易发生气瓶爆炸事故。因此,为保障消防气瓶安全,研究开发了以检测消防气瓶微变形为基础的安全监测技术,采取在气瓶表面缠绕线型传感器的方法检测变形。通过气瓶爆破试验,验证了该技术可有效探测高压气瓶的微变形,并利用以太网将信息传输至大数据平台集中管理,实现主动监管功能。

考虑MAF延时和前馈补偿的高压直流快速锁相环

同步参考坐标系锁相环是高压直流(high voltage direct current,HVDC)同步触发控制系统中广泛应用的一种窄带宽锁相环,在交流系统故障引起相位跳变情况下,其动态响应缓慢。为增大锁相环的带宽,一种滑动平均滤波器(moving average filter,MAF)被前置于锁相环路,然而MAF本身存在响应延迟,制约了锁相环的同步速度。为了缓解响应延迟问题,文中提出一种考虑MAF延时和前馈补偿的HVDC快速锁相环。首先,利用MAF线性暂态特征预测相位变化,并分别针对故障接入和切除引起的相位跳变问题提出不同的补偿策略;接着,利用不变性原理对锁相环路进行前馈补偿,在负反馈控制和前馈补偿共同构成的复合校正控制系统的作用下,锁相环能够在较小PI参数下实现快速响应;最后,将所提快速锁相环在CIGRE HVDC标准模型和三峡—上海直流工程模型中进行仿真验证。结果表明,该快速锁相环能够有效缓解滤波器响应延迟的制约,缩短失锁时间,进而提高高压直流逆变侧抵御换相失败的能力。