阵列旋转对功率倒置算法性能的影响分析

针对卫星导航抗干扰中,功率倒置算法下导航信号载噪比受干扰来波方向的影响,通过理论推导和数值计算的方法研究了天线阵列旋转与功率倒置算法抗干扰性能的关系。分析结果表明:天线阵列旋转会使功率倒置算法下的阵列增益在最大值和最小值之间呈现连续的、周期性的变化。相比固定天线阵不变的载噪比,阵列旋转能够使信号在一段时间内获得更大的载噪比,对于四阵元Y型阵列,阵列旋转理论上对载噪比的最大提升程度可以达到14dB左右。仿真结果验证了理论推导的正确性。     

Active,compact, wideband,receiving filtenna with power adaptation for space-limited wireless platforms

An active, compact, wideband, receiving filtenna with power adaptation for space-limited wireless platforms is presented. By organically combining a filtering antenna and a Variable Gain Amplifier (VGA), the proposed co-designed active filtenna is achieved. Its power adaptation is empowered by controlling gain of the VGA unit. A demonstrated prototype with a compact overall size is fabricated, assembled and measured. Good performances are achieved. Furthermore, in any condition, the proposed active filtenna displays outstanding impedance matching (|S₁₁| < ?10 dB) and high passband skirt selectivity at upper and lower stopbands (Selectivity ≥ 170 dB/GHz).     

Distributed fixed-time attitude coordinated control for multiple spacecraft with actuator saturation

This paper investigates the distributed fixed-time attitude coordinated control problem for multiple spacecraft subject to actuator saturation under the directed topology. First, a distributed fixed-time observer is presented for each follower spacecraft to estimate the leader spacecraft’s states. Compared with the commonly used fixed-time observer, the settling time of the proposed fixed-time observer can be easily adjusted by some free design parameters. Next, a distributed fixed-time control ...     

Adaptive feedback control of stability in an axial compressor with circumferential inlet distortion

The adaptive feedback control of stability with circumferential inlet distortion has been experimentally investigated in a low-speed, axial compressor. The flat-baffles with different span heights are used to simulate different distorted inflow cases. Compared with auto-correlation and root-mean-square analysis, cross-correlation analysis used to predict early stall warning does not depend on the distortion position. Hence, the cross-correlation coefficient was used to monitor the stable status of the compressor and provide the feedback signal in the active control strategy when suffering from different distortions. Based on the stall margin improvement of tip air injection obtained under different distorted inflow cases and the sensitivity analysis of cross-correlation coefficients to injected momentum ratios, tip air injection was adopted as the actuator for adaptive feedback control. The digital signal processing controller was designed and applied to achieve adaptive feedback control in distorted inflow conditions. The results show that the adaptive feedback control of air injection nearly achieves the same stall margin improvement as steady air injection under different distortion intensities with a reduced injection mass flow. Thus, the proposed adaptive feedback control method is ideal for the engine operation with circumferential distorted inflow, which frequently occurs in flight.     

Optimal trajectory design accounting for the stabilization of linear time-varying error dynamics

This study is dedicated to the development of a direct optimal control-based algorithm for trajectory optimization problems that accounts for the closed-loop stability of the trajectory tracking error dynamics already during the optimization. Consequently, the trajectory is designed such that the Linear Time-Varying(LTV) dynamic system, describing the controller’s error dynamics, is stable, while additionally the desired optimality criterion is optimized and all enforced constraints on the traje...     

一种互相关法测量相位噪声理论及仿真分析

相位噪声测量是无线电计测领域的重要研究内容，随着信号源等各种信号仪器设备的不断发展，相位噪声测量技术方面也产生了更高的要求。介绍了互相关法测量相位噪声的理论与仿真分析方法，通过理论推导阐释了互相关法抑制干扰噪声的原理，在推论的基础上建立了基于MATLAB的仿真分析模型，仿真验证了不同互相关次数下，系统噪声底部的改善程度，并进一步分析了双通道相关性对互相关运算结果的影响，得到了对应的仿真验证结果，为相关的工程设计提供参考。     

动态负调约束下固体冲压发动机燃气流量控制算法研究

变流量固体冲压发动机工作过程中，常采用控制燃气发生器压强的方式调节燃气生成量，在跟踪变化压强指令过程中，流量会产生明显的负调现象，严重影响发动机系统的安全性和可靠性。为 解决这一问题，本文以具有高度非线性、强时变特性的燃气发生器系统为对象，构建了基于粒子群算法的流量调节自适应PI控制器，并给出一种利用自适应微分跟踪器对期望控制指令进行“整形”的负调改善算法；首先，结合负调发生、终止判据，综合考量系统流量安全裕度，负调发生方向，构建了适配于动态负调约束的自适应跟踪微分器（TD），克服了传统跟踪微分器在负调抑制过程中控制精度不高，指向性不强等缺陷；进一步，开展了多工况下的负调抑制算法仿真校验，结果表明：所设计自适应控制算法具备良好的燃气流量控制能力，可实现在基本不改变响应时间情况下，将最大负调量削减56.6%的控制效果，展现出良好的工程应用前景。     

A power and thermal management system for long endurance hypersonic vehicle

Due to the pneumatic heating and combustion effect, the scramjet engine of hypersonic vehicle faces high temperature challenge. It is necessary to comprehensively consider its thermal management and power generation together. A new Power and Thermal Management System (PTMS) combined with Supercritical Carbon Dioxide (SCO₂) closed Brayton cycle and fuel vapor turbine is proposed and discussed in this paper. The new PTMS can meet the cooling requirement of hypersonic vehicle at Mach number 6–7, and avoid the coking and scrapping in the scramjet cooling channels. Compared with the PTMS only based on fuel vapor turbine, the new PTMS utilizes the waste heat of scramjet to generate more electricity. In addition, it can reduce the use of fuel sink for cooling, and the additional weight penalty can be compensated for long endurance hypersonic flight.