某型飞机改装虚警隔离后报“CO”虚警故障分析

某型飞机在外场飞行、维护和内场调试过程中,多次发生因虚警报"СО"(转速急降)故障,检查发现发动机及相关附件并无故障,而是由于改装虚警隔离相关电缆线路中所出现了故障而产生告警信号。针对这一故障现象,对改装虚警隔离装置的工作原理和线路故障进行分析,找出"СО"虚警故障的原因以及电缆故障的原因,提出修理和维护的方法和建议,为相关从业者提供借鉴。     

Minimal-Order Models for False-Alarm Calculations on Sliding Windows

A procedure is developed to obtain practical numerical results in connection with the m-out-of-n sliding-window detection problem. This effort was motivated by difficulties with previous approaches involving approximation, Markov models, and Monte Carlo simulation. Generating-function methods were found to be unsatisfactory for window lengths greater than 6 due to their complexity. Instead, a Markov model is described that is then constructively reduced to the minimum number of state variables. The results are derived for binary strings with intersymbol correlation. Computational aids are discussed for obtaining design information, such as quantiles, from the minimal-order Markov models. Numerical results are given comparing the methods of the paper with a "jumping" window approximation for an 8/10 problem.     

Constrained Improvement MTI Radar Processors

A new class of staggered PRF MTI radar processors is developed in this paper. These processors are constrained to achieve a specified value of MTI improvement and, subject to this constraint, minimize variations in processor response as a function of target Doppler frequency. The selection of both filter weights and PRF stagger sequences is discussed and a number of representative designs are presented.     

Performance of Likelihood Ratio Processors

Summarized by its ROC curve, the performance of a Bayes optimal detector is a function of two joint a priori probability density functions on the uncertain parameters involved. An investigation is made to determine at what point in the generation of an ROC curve for a given pair of priors sufficient information is retained for the calculation of a new ROC based on a different pair of priors.     

Constant-False-Alarm-Rate Processors for Locally Nonstationary Clutter

A technique for designing normalizing processors for locally non-stationary clutter is discussed. The design procedure assumes the logarithm of the clutter power varies as a polynomial with range. When the actual environment matches the design environment, the false-alarm rate is a constant that is independent of the polynomial coefficients. A measure of the relative target detection capability as a function of the number of normalization cells and the degree of the design-environment polynomial is given. The applicability of the processors to non-Rayleigh clutter is discussed.     

Phase-Coded Interrupted CW Signals and Processors

High resolution radars require signals with large time-bandwidth product such as CW signal and coherent pulse train (CPT). We discuss a phase-coded interrupted CW (ICW) signal which is the combination of CW signal and CPT. Phase codes used here are with perfect periodic autocorrelation. The periodic ambiguity function of ICW signals is studied including single-carrier signal and multi-carrier signal. It is interesting that the gate function has different effects on two signals and contributes to a multi-carrier ICW signal which yields nearly perfect autocorrelation. Meanwhile we also suggest an efficient receiver approach to ICW signals, which can reduce the computational burden of the processor and utilize the good properties of P3 and P4 codes.     

A Sequential Implementation of Optimal Array Processors

A sequential implementation of the likelihood ratio for doubly composite hypothesis array processing problems is presented in which the likelihood ratio is realized by an appropriate combination ion of single frequency components. The array processos decomposed in such a way that the actual a priori parameter knowledge dge need not be introduced until after a significant portion of the data processing has taken place.     

Constant-False-Alarm-Rate Signal Processors for Several Types of Interference

Distribution-free methods and maximum-likelihood estimation technique have been previously suggested for constant-false-alarm-rate (CFAR) processors. The first technique assumes no a priori environmental knowledge and the second assumes almost complete environmental knowledge. Several intermediate environmental assumptions are considered. The performance of single-pulse transmission signal processors that produce CFAR for the different environments is analyzed. Probability of target detection is evaluated for Rayleigh interference and Swerling I target. It is shown that adaptive threshold techniques implemented by logarithmic amplifiers, instead of linear amplifiers, can attain better false-alarm-rate control with only small loss in target detectability.     

Distribution-Free Processors Based on the Theory of Runs

This correspondence describes distribution-free processors based on the theory of runs. No assumption about either the functional form of the distribution of noise or the nature of its distribution is made. Hence the processors described are expected to yield constant false alarm (CFA) irrespective of the nature of noise encountered in the system.     

Error Analysis of the Optimal Antenna Array Processors

The optimal weights of an antenna array processor, which maximizes the output signal-to-noise ratio (SNR) in the absence of errors, are computed using the noise-alone matrix inverse (NAMI) and the steering vector in the look direction or the signal-plus-noise matrix inverse (SPNMI) and the steering vector. In practice the estimated steering vector as well as the estimated optimal weights are corrupted by random errors. This paper has analyzed the effects of these errors on the performance of the NAMI processor and the SPNMI processor by deriving analytic expressions for the output signal power, output noise power, output SNR, and the array gain as a function of the error variance. The treatment is for a general array configuration and no assumption about a particular array geometry is made.     

航空电子系统中应用多核处理器的挑战分析

作为嵌入式计算的一种,航空电子系统中的处理器具有强实时性、高确定性、高安全性的特征。因此,同其他嵌入式系统相比,在航空电子系统中应用多核处理器面临更多的挑战。针对多核处理器基本的软硬件架构,对挑战产生的原因进行了简要的分析,指出了在航空电子系统中应用多核处理器需要解决的问题。     

Signal Processors and Accuracy of Three-Beam Monopulse Tracking Radar

The problem of implementing a monopulse tracking radar is considered when three beams are used rather than the customary four. Signal processors are developed for both amplitude and phase comparison radar cases and the functional form is given for the general case (a combination or hybrid case). Accuracy is investigated by applying the Cramer-Rao inequality. General results are given for the maximum theoretical accuracy of estimating target amplitude, phase, and position angles when the radar is of the amplitude comparison type. Equations sufficient for obtaining accuracies in the phase comparison and combination cases are included.     

一种嵌入式处理器间SPI总线通信优化方法

SPI(Serial Peripheral Interface,串行外设接口)作为一种全双工的同步通信总线,常用于嵌入式处理器间的通信.提出一种在P2020处理器与基于Xilinx K7 FPGA芯片的软核处理器间的SPI总线通信优化方法.利用SPI总线双向同步传输的特点,提出一种简易且有效的通信协议保证通信质量;根据SPI总线两端处理器的时钟频率,设置SPI总线波特率,提升数据传输速率;同时,考虑SPI总线两端处理器的处理频率的差异,设置合理数据传输延迟,保证数据传输的正确性和稳定性.实验结果表示,该SPI总线通信方法在上述平台中能够达到750KB/S的通信速率,能够满足多种嵌入式平台的数据传输需求.     

An Improved Two-Element Almost Omnidirectional Receiver

The sum of received power has been suggested as a method for providing improved signal detectability from a plurality of sensors while retaining omnidirectionality. This paper describes an alternative procedure for the two-element case that, while not quite omnidirectional, offers a decided advantage in detection performance over the power sum scheme. It involves taking the logical union of the thresholded power of the sum of the sensor outputs and the thresholded power of the difference of the sensor outputs. A comparison of the two systems is presented and it is shown that the latter scheme is almost always better than the former.     

Analysis of Some Modified Cell-Averaging CFAR Processors in Multiple-Target Situations

A serious degradation of detection probability (Pd) in a cellaverging constant false alarm rate (CA-CFAR) detector is known to be caused by the presence of an interfering target in the set of reference cells. A technique which is often used to prevent excessive false alarms at clutter ?edges? is a ?greatest of? (GO) selection between the leading and lagging sets of cells (GO-CFAR). However, it is demonstrated for a Rayleigh target that the abovementioned suppression effect is more acute in the GO-CFAR. Practically, detection of closely separated targets is almost inhibited. Selection of the ?smallest of? (SO) the means for the adaptive threshold has been proposed to alleviate this problem. An analytic expression for Pd of this detector is also derived, and it is shown that though it does prevent the suppression effect, a large sensitivity loss is introduced unless the number of reference cells is sufficiently large. A modified CO-CFAR detector, combining a ?censoring? circuit, is proposed for automatic detection in a complex nonhomogeneous environment.     

Performance Compparison of Optimum and Conventional MTI and Doppler Processors

The performance of an optimum radar signal processor and more conventional techniques (such as MTI, adaptive MTI, and cqherent integration) are compared. A mathematical method is suggested and applied to several cases of practical interest. A number of operative conditions are discovered in which the conventional processing techniques give very poor performance and the optimum radar processor becomes necessary.     

Almost instant time inference for hybrid partially dynamic Bayesian networks

A Bayesian network (BN) is a compact representation for probabilistic models and inference. They have been used successfully for many military and civilian applications. It is well known that, in general, the inference algorithms to compute the exact a posterior probability of a target node given observed evidence are either computationally infeasible for dense networks or impossible for general hybrid networks. In those cases, one either computes the approximate results using stochastic simulation methods or approximates the model using discretization or a Gaussian mixture model before applying an exact inference algorithm. This paper combines the concept of simulation and model approximation to propose an efficient algorithm for those cases. The main contribution here is a unified treatment of arbitrary (nonlinear non-Gaussian) hybrid (discrete and continuous) BN inference having both computation and accuracy scalability. The key idea is to precompile the high-dimensional hybrid distribution using a hypercube representation and apply it for both static and dynamic BN inference. Since the inference process essentially becomes a combination of table look-up and some simple operations, the method is shown to be extremely efficient. It can also he scaled to achieve any desirable accuracy given sufficient preprocessing time and memory for the cases where exact inference is not possible     

基于VPX标准的双路“龙芯”3A计算机模块设计

VPX是一种开放的总线形式,与国产化CPU（中央处理器）结合实现VPX计算机模块是一种新的应用需求.针对这种需求对VPX总线标准及国产的“龙芯”3A芯片进行研究,从原理上结合二者特点,再利用高速高密度布线方式,以欧卡6U的标准设计完成了基于VPX的国产化计算机模块.对模块的功能和性能分别进行测试,分析可得,模块化方式的计算机和普通计算机在主板的性能和功能上表现一致,而且可直接用于具有抗震加固特性的机箱,更适用于未来的军事应用.