高阶柔性结构系统振动控制中加权函数的选择

 总结了混合灵敏度H_∞控制算法中加权函数阵的选择方法,提出了一种新的选择加权函数矩阵的思想。以某悬臂梁为研究对象,将混合灵敏度H_∞控制方法应用在高阶柔性结构的振动主动控制问题中,完成了两输入两输出结构振动控制的控制器设计和算法仿真。结果表明,通过本方法选择加权函数矩阵,可在满足鲁棒稳定性的前提下,使外部干扰得到有效抑制,减振效果良好。     

A Technique for Improving the Clutter Performance of Coherent Pulse Train Signals

The clutter performance of a radar using coherent pulse train signls depends upon the phase and amplitude weighting used on transmit and receive. This paper describes an iterative technique to determine better weightings. Each iteration improves the signal-to-interference ratio, where the interference is the sum of the mean square noise voltage and the mean square clutter voltage at the time of peak signal. Two examples are presented to illustrate the method and to demonstrate that in many cases the procedure will yield weightings that may be used in a system where the transmitter permits no amplitude weighting.     

Design of Weighting Functions Under Peak Amplitude and Effective Radiated Voltage Constraints

The problem of designing optimum weighting functions subject to peak amplitude and effective radiated voltage constraints occurs in the design of active phased arrays and in spectrum control of high-pulse-repetition frequency (PRF) pulsed Doppler transmitters. Algorithms for generating such weighting functions are developed using a least-squares technique. Numerical results are presented which show that these algorithms yield substantial performance improvement over textbook weighting functions in favorable circumstances.     

Clutter Suppression Properties of Weighted Pulse Trains

A common but troublesome requirement on radar sensors is the detection of a target in the interference from undesired scatterers, or clutter. Systems with coherent processing of pulse trains are uniquely suited for the purpose because, with pulse trains, it is possible to concentrate the receiver output for particular values of Doppler and thus suppress the clutter by Doppler filtering. This paper discusses to what degree the effectiveness of the method can be enhanced by tapering, or weighting, of the pulse amplitudes. The general results are illustrated by computer-plotted response functions for weighted pulse trains. The clutter suppression efficiency of weighting is calculated both for unilateral weighting in the receiver and for bilateral weighting in both receiver and transmitter. The significance of additional phase weighting is discussed and the results for pure amplitude weighting are compared with publishedwork on phase and amplitude weighting.     

Phase quantized SAR signal processing: theory and experiments

A complete theory of synthetic aperture radar (SAR) processing from phase-only data is presented, for both analogue and coded raw signals and reference functions. Appropriate processing architectures are presented as well as quality indexes to judge performance of the selected coding. The analysis encompasses both images and interferometric fringes for interferometry SAR (IFSAR) application. Theoretical results are validated by a large number of experiments, comparing the performance of the suggested coding levels, and their combinations between raw and reference functions. Experiments are extended until the comparison of final digital elevation models     

Generalized Response of a Linear FM Pulse Compression Matched Filter

A pulse compression matched filter is analyzed so that the response may be computed when the pulse width, FM rate, and center frequency simultaneously differ from design conditions. Unilateral and bilateral time domain amplitude weighting for sidelobe reduction is included. A general cross-ambiguity function is defined to include these effects and some basic computed results are presented for the peak envelope response with various degrees of Hamming weighting. Computer evaluation of this cross-ambiguity function allows one to choose a combination of mismatches for signal design trade-off between resolution and detection performance. Since no restrictions are placed upon the mismatch parameters, this analysis may also be used to evaluate the filter discrimination against various interfering signals.     

Range Dependent Waveform of an Active Weighted Pulse Compression Receiver

This paper presents the output waveform of a correlation techniquewhich incorporates time domain amplitude weighting and matchedfiltering. This scheme may be used in pulse compression radars wherefine target detail is desired over an increment of range, the rangewindow. Analytic expressions describing the amplitude, phase, andfrequency modulation of the output waveform are obtained for thecosine-squared weighted spectrum, truncated Taylor weighted spectrum,and cosine-cubed weighted spectrum with weighting mismatchas a parameter. The effects of such mismatches on the amplitude,phase, and frequency modulation of the compressed waveform areplotted. However, the methods used to obtain these results are generalenough to obtain output waveforms of other weighting functions similarlymismatched.     

高超声速飞行器后体/尾喷管一体化设计

采用实数编码、小生境技术、稳态复制策略、多目标定级排序技术,改进了标准遗传算法,建立了多目标遗传算法,并将其应用于高超声速飞行器后体/尾喷管的一体化设计,以尾喷管的推力、升力和附加俯仰力矩系数为性能目标,得到了优化问题的Pareto最优前沿面,优化结果显示了设计变量与性能目标之间的关系,并提出了建议的外形方案。该优化算法可进一步推广应用于包含更加精确的流动模型的优化设计当中。     

Removing autocorrelation sidelobes by overlaying orthogonal coding on any train of identical pulses

A coherent train of identical linear FM (LFM) pulses is used extensively in radar because of its good range and Doppler resolution. Its relatively high autocorrelation function (ACF) sidelobes are sometimes reduced through spectrum shaping (e.g., nonlinear FM, or intrapulse weighting on receive). We show how to completely remove most of the ACF sidelobes about the mainlobe peak, without any increase to the mainlobe width, by diversifying the pulses through overlaying them with orthonormal coding. A helpful byproduct of this design is reduced ACF recurrent lobes. The overlaid signal also results in reduced Doppler tolerance, which can be considered as a drawback for some applications. The method is applied to several trains of identical pulses (LFM and others) using several orthonormal codes. The effect on the three important properties of the radar signal: ACF, ambiguity function (AY), and frequency spectrum is presented. The effect on Doppler tolerance is studied, and implementation issues are discussed. The new design is also compared with complementary and sub-complementary pulse trains and is shown to be superior in many aspects.     

Pulse Compression Results Using Metallic Reflective Array Lines

Radar pulse-compression results are presented for the first reflective-array compressor (RAC) dispersive delay lines (DDL) with both metallic reflecting arrays and phase-compensating films. The time-bandwidth product of the devices reported is approximately 400. Operation in a recirculation loop with a 37.5-dB Taylor weighting filter yielded 36-dB near-in range sidelobes. RMS phase errors less than 0.71 degrees across the band were achieved. Greater than 50-dB rejection of spurious response is achieved in the far-out range gate region. The potential for high-quality cost-effective fabrication of metallic RAC DDL for system applications is explored.     

The effect of I,Q mismatch errors on adaptive cancellation

The effects of in-phase (I) and quadrature-phase (Q) amplitude errors and low-pass-filter (LPF) errors on adaptive cancellers are investigated. I,Q errors occur because of errors in the synthesis process of the mixers and LPFs designed to be identical for each input channel. These I,Q errors among the channels result in cancellation degradation. Tapped delay line transversal filters have been proposed as a way to compensate for these errors and thus improve cancellation performance. However, it is shown that if there is any LPF mismatch, then transversal filtering has a small effect on improving canceler performance. The use of individual I,Q adaptive transversal filter weighting is suggested as a means of completely eliminating the phase amplitude errors, and making the canceler performance responsive to transversal filter compensation     

算术编码在航空侦察图像压缩中的应用

航空侦察图像原始数据量非常大,在实时回传的过程中必须进行压缩。在对图像进行有损或无损压缩时,无损压缩算法是必要的。本文研究了算术编码在系统中的应用,提出一种混合进制的算术编码,提高编码效率的同时增强了系统的抗误码扩散能力。试验验结果表明该算法明显优于单一进制的编码算法。     

基于有向元的圆柱阵列波束赋形

对其形圆柱阵列进行了波束赋形,在考虑阵元有向性的基础上,利用基于最小均方误差的自适应算法迭代得到一组最优权值,通过对阵元激励的幅度、相位进行加权调整,能够使阵列波束方向、主波束形状、副瓣电平达到给定要求：运用此方法得到共形圆柱阵列的平预波束和余割平方波束方向图,效果较好,证明此方法对于共形阵列是有效的     

Effects of finite weight resolution and calibration errors on theperformance of adaptive array antennas

Adaptive antennas are now used to increase the spectral efficiency in mobile telecommunication systems. A model of the received carrier-to-interference plus noise ratio (CINR) in the adaptive antenna beamformer output is derived, assuming that the weighting units are implemented in hardware, The finite resolution of weights and calibration is shown to reduce the CINR. When hardware weights are used, the phase or amplitude step size in the weights can be so large that it affects the maximum achievable CINR. It is shown how these errors makes the interfering signals “leak” through the beamformer and we show how the output CINR is dependent on power of the input signals. The derived model is extended to include the limited dynamic range of the receivers, by using a simulation model. The theoretical and simulated results are compared with measurements on an adaptive array antenna testbed receiver, designed for the GSM-1800 system. The theoretical model was used to find the performance limiting part in the testbed as the 1 dB resolution in the weight magnitude. Furthermore, the derived models are used in illustrative examples and can be used for system designers to balance the phase and magnitude resolution and the calibration requirements of future adaptive array antennas     

Optimum Signals for Radar

The research reported herein deals with the general problem of the selection of radar waveforms. The investigation is specifically concerned with the synthesis of radar signals which are optimum in the sense that they are characterized by ambiguity surfaces minimized over certain predetermined regions of the ambiguity plane. The weighted ambiguity surface is utilized as the weighted error criterion. This error criterion is mathematically tractable and pertinent to radar system performance but is not unduly restrictive as some orientation parameters are left unspecified for subsequent cost or penalty function analysis. The signal optimization is approached by variational techniques augmented by equality and inequality constraints, for example, limiting the amount of bandwidth or frequency modulation to be less than some system requirement. Several examples are presented demonstrating the optimization techniques and providing a minimum error for the stated problem. It is shown that for any given type of amplitude modulation of the radar signal, the variance or dispersion of the ambiguity surface is not decreased for any type of phase modulation added. The optimum signal for an elliptical weighting function is derived for several cases. The minimum error is shown to depend upon the constraints and the unspecified orientation parameters and, for one case, on the second moment of the signal.     

Equalization of QPSK Data Transmission in Specular Multipath

This paper gives performance results for transversal-filter equalization of quadriphase phase-shift-keyed (QPSK) signals with two-component multipath and demodulator phase error. An analytical expression for optimum, minimum mean-square-error tap weights in terms of the multipath and signal parameters is given. Probability of error results for no equalization and equalization with adaptive decision-feedback tap-weight adjustment are compared. The results show that significant improvement can be obtained with relatively simple equalizer structures.     

航空发动机PID神经网络解耦控制

对航空发动机的双变量解耦控制方法进行了研究,提出了一种基于遗传算法的PID神经网络解耦控制算法。该算法将遗传算法用于多层前向神经网络的连接权系数的学习,克服了BP算法易陷入局部权值的缺点,并具有PID神经网络控制器结构简单规范、动态和静态性能良好等优点。     

线性最优调节器的加权阵选择

 本文提出了一种新的线性二次到调节器的加权阵的选择方法。使用这种方法设计的线性调节器具有状态（或输出）调节时间最短、超调量小对初始条件鲁棒性强的特点。提出的递推算法是简便的。这种方法在一个实际的飞行器控制系统设计中得到应用。     

任意拓扑结构的耦合振荡器阵列及其在共形阵中的应用

提出了一种利用耦合振荡器阵列实现共形相控阵天线波束扫描的新方法。建立了任意拓扑结构的耦合振荡器阵列幅度和相位动力学方程,采用图论的方法分析了稳态相位方程解的唯一存在性和稳定性,通过控制振荡器每个单元的自由振荡频率,对相位进行加权,实现了共形相控阵天线无移相器的波束扫描,最后对圆柱形耦合振荡器阵列天线进行了数值仿真,验证了该方法的可行性。     

The DFTSD: A Sequential Suboptimum Processor for Multiple-Range-Bin Radar Systems

A class of simple and efficient digital sequential detectors is presented, which are particularly suitable for application to radar systems where the antenna dwell time is easily varied. A methematical method, based on the random walk model, is developed to evaluate the DFTSD (digital fixed-thresholds sequential detector) performance. The DFTSD has a loss of 0.2 to 0.3 dB with respect to the digital SPRT (sequential probability ratio test) in the case of a single-range-bin system. Finally, results for the multiple-range-bin case are presented and compared with the performance of a moving-window detector.