Few-shot electromagnetic signal classification: A data union augmentation method

Deep learning has been fully verified and accepted in the field of electromagnetic signal classification. However, in many specific scenarios, such as radio resource management for aircraft communications, labeled data are difficult to obtain, which makes the best deep learning methods at present seem almost powerless, because these methods need a large amount of labeled data for training. When the training dataset is small, it is highly possible to fall into overfitting, which causes performance degradation of the deep neural network. For few-shot electromagnetic signal classification, data augmentation is one of the most intuitive countermeasures. In this work, a generative adversarial network based on the data augmentation method is proposed to achieve better classification performance for electromagnetic signals. Based on the similarity principle, a screening mechanism is established to obtain high-quality generated signals. Then, a data union augmentation algorithm is designed by introducing spatiotemporally flipped shapes of the signal. To verify the effectiveness of the proposed data augmentation algorithm, experiments are conducted on the RADIOML 2016.04C dataset and real-world ACARS dataset. The experimental results show that the proposed method significantly improves the performance of few-shot electromagnetic signal classification.     

Potential starter/generator technology for future aerospaceapplication

This paper presents a search and comparative review of the literature available on variable speed constant frequency (VSCF) technologies. In particular, most of the progress made in the past ten years, using power electronics and electric machines for VSCF systems is reported. Two VSCF systems, based on induction and switched reluctance machine technologies, are presented. The research on the singly- and doubly-fed induction machines has focused on VSCF for wind power generation; whereas, that on switched reluctance machines has been directly studied as a VSCF technology in aircraft system. Results obtained so far favor the switched reluctance machine over the induction machine. Based on the foregoing comparative review, it is recommended that the induction machine be fully investigated as a VSCF drive in aircraft system. The findings should then be compared with the counterpart SRM system. Issues of comparison may include fault tolerance and redundancy, power density, torque requirements, overload ratings, temperature range and cooling, efficiency and stability over expected operating speed range     

An output feedback controller for a synchronous generator

A novel approach using eigenstructure assignment is developed for the design of excitation controllers for synchronous generators. The computation procedure for the method is easy to apply, and an exact solution can be obtained without iteration. Controllers designed by the proposed approach can be easily implemented by means of proportional-integral (PI) controllers. Practical considerations in reaching an optimum selection of closed-loop eigenvalues are addressed. Time-domain simulation results are presented to verify the effectiveness of the design method     

Potential starter/generator technologies for future aerospaceapplications

This paper presents a search and comparative review of the literature available on variable speed constant frequency (VSCF) technologies. In particular, most of the progress made in the past ten years, using power electronics and electric machines for VSCF systems, is reported. Two VSCF systems, based on induction and switched reluctance machine technologies are presented. The research on the singly- and doubly-fed induction machines has focused on VSCF for wind power generation, whereas that on switched reluctance machines has been directly studied as a VSCF technology in aircraft systems. Results obtained so far favor the switched reluctance machine over the induction machine. Based on the foregoing comparative review, it is recommended that the induction machine be fully investigated as a VSCF drive for aircraft systems. The findings should then be compared with the counterpart SRM system. Issues of comparison may include fault tolerance and redundancy, power density, torque requirements, overload ratings, temperature range and cooling, efficiency and stability over expected operating speed range     

集成电路测试系统程控直流电源校准技术研究

介绍了集成电路测试系统中程控直流电源的结构、工作原理,分析了影响程控直流电源准确校准的因素,提出采用开尔文连接校准程控直流电源的方法。根据该原理对ASL3000集成电路测试系统进行了校准实验,通过对测量结果的不确定度进行分析,证实了测量结果的准确性和可靠性。     

A new method for finding electromagnetic emitter location

The position of a source of radiation is often obtained from bearing data, taken over an interval of time, and combining it with navigation data. A new method using total least squares (TLS) has been suggested for the accurate estimation of an emitter location when bearing observation errors are random. Further, an iterative two-stage approach involving TLS and Kalman filtering is developed for accurate estimation of the emitter location when bearing observation errors are an algebraic sum of random and systematic errors. The elegance and efficacy of the proposed methods are illustrated through digital computer simulated examples     

An LMI-based decoupling control for electromagnetic formation flight

Electromagnetic formation flight(EMFF) leverages electromagnetic force to control the relative position of satellites. EMFF offers a promising alternative to traditional propellant-based spacecraft flight formation. This novel strategy is very attractive since it does not consume fuel. Due to the highly coupled nonlinearity of electromagnetic force, it is difficult to individually design a controller for one satellite without considering others, which poses challenges to communications.This paper is devoted to decoupling control of EMFF, including regulations, constraints and controller design. A learning-based adaptive sliding mode decoupling controller is analyzed to illustrate the problem of existing results, and input rate saturation is introduced to guarantee the validity of frequency division technique. Through transformation, the imposed input rate saturation is converted to state and input constraints. A linear matrix inequalities(LMI)-based robust optimal control method can then be used and improved to solve the transformed problem. Simulation results are presented to demonstrate the effectiveness of the proposed decoupling control.     

GNSS receiver for GLONASS signal reception

This paper deals with the latest version of Experimental GNSS receiver built at the Czech Technical University and describes integration of GLONASS signal processing to the receiver. The new FPGA platform Virtex-D Pro by Xilinx is used and enables integration of whole digital signal processing of GNSS receiver into the single chip. The RE unit of the receiver is capable of processing all GLONASS frequency of the Li and L2 bands in two independent RE channels; each channel can process one band. The frequency selection of the appropriate satellite is accomplished in a digital correlator. The development flow of the GLONASS correlator is discussed herein. The complexity of the GLONASS correlator with complexity of GPS correlator is compared. The developed GLONASS correlator was tested in Simuelink tool during development. The next test was carried out using GLONASS simulator and real GLONASS satellite signal.     

A computing model and its experimental testing for an evaluation of electromagnetic interferences created by interfering circuits on transmission or high-voltage lines above a dissipative ground

In this paper we present useful calculations for a prediction of the electromagnetic field created by interfering circuits on a linear horizontal transmission line over an imperfectly conducting ground. The interfering circuits are assimilated to antennas and treated by using the dipole-radiation theory. The current distribution is determinated by the transmission-line theory. We present here the computational procedure allowing a fast and accurate calculation of the electromagnetic fields components of a series of dipoles. We give the linear characteristics Z, Y of the transmission line by incorporating the ground effects. The response of a terminated one-wire transmission line set over the ground and excited by a non-uniform field is given. A comparison between computed results given by the model and experimental measurements is provided.     

湿式多片电磁离合器的应用

首先介绍了湿式多片电磁离合器的结构原理及特点，并根据实际应用情况重点介绍了整体和分轴两种安装形式，以及其在使用过程中的润滑和控制电路，最后总结了应用效果和使用中的注意事项。     

Switched Ethernet testing for avionics applications

Switched Ethernet is being implemented as an avionics communication architecture. A commercial standard (ARINC-664) and an aircraft vendor-specific implementation known as avionics full duplex switched Ethernet (AFDX) have been developed that defines the topology and use of switched Ethernet in an avionics application. In avionics applications, the movement of data between devices must take place in a deterministic fashion and must be delivered reliably. All aircraft flight hardware must be tested to be sure that it will communicate information properly in the switched Ethernet network. The airframe manufacture must test the integrated network to verify that all flight hardware is communicating properly. Testing and maintenance testing is required to perform data communication level testing of switched Ethernet architectures for avionics applications to insure that all communication is deterministic and reliable. This paper provides an overview of a switched Ethernet avionics network and identifies the testing challenges associated with a switched Ethernet avionics application. A practical implementation performing the required tests is discussed.     

Model-based robustness testing for avionics-embedded software

Robustness testing for safety-critical embedded software is still a challenge in its nascent stages. In this paper, we propose a practical methodology and implement an environment by employing model-based robustness testing for embedded software systems. It is a system-level black-box testing approach in which the fault behaviors of embedded software is triggered with the aid of modelbased fault injection by the support of an executable model-driven hardware-in-loop (HIL) testing environment. The prototype implementation of the robustness testing environment based on the proposed approach is experimentally discussed and illustrated by industrial case studies based on several avionics-embedded software systems. The results show that our proposed and implemented robustness testing method and environment are effective to find more bugs, and reduce burdens of testing engineers to enhance efficiency of testing tasks, especially for testing complex embedded systems.     

Model-based multifrequency array signal processing for low-angletracking

Tracking low-altitude targets over the sea is problematic because of interference between the direct and reflected signal. Standard monopulse trackers can experience large errors because of multipath maximum likelihood estimation (MLE) has been used to more accurately estimate the target height in the presence of multipath MLE is a model-fitting technique where the model parameters are chosen to maximize the likelihood function. It is shown that the type of observation model has a large effect on performance. Tracking performance is compared using three different observation models employing varying amounts of a priori information. Results are presented for different array sizes: eight and 32-element arrays and two-element subarrays typical of phase monopulse. Performance is compared with that of standard techniques such as Fourier beamforming and phase monopulse     

Best practices for large-scale signal conditioning systems

Sensor and high-voltage measurements are a vital part of many test systems. What makes these measurements different from typical voltage or current measurements is that a special type of conditioning is required to bring these signals into a measurable range. Some of the common examples of signal conditioning include filtering to eliminate 50 or 60 Hz noise, bridge completion to amplify small signals, isolation of hazardous voltages or attenuating high-voltage signals.     

混沌掩盖的同步通信技术

混沌信号具有类随机的性质,这就使得混沌信号越来越广泛的应用于保密通信系统中.介绍了通过采用LMI（Linear Matrix Inequation）设计反馈系数的方法,实现同步通信信息的保密性,并通过MATLAB仿真证明了结论的正确性.在信号传输过程中,当混沌系统达到同步以后,在其接收端能恢复出原始信息,从而实现混沌系统的保密通信.     

406 MHz ELT signal spectra for SARSAT

The signal format and spectral properties of the 406-MHz emergency locator transmitter (ELT) used in the search and rescue satellite aided tracking (SARSAT) system are examined. The ELT improves location estimate accuracies and can relay information about the particular aircraft and its problem, by means of the digitally modulated message fields. It is shown that due to the RF signal frequency characteristics and the Doppler shift, processing must be performed over a frequency band of approximately 25 kHz. Through the use of the fast Fourier transformation (FFT), the frequency spectrum of the ELT is analyzed, taking account of effects due to noise, multiple simultaneously received signals, and Doppler shift. It is demonstrated that the FFT provides an effective means for detecting and recognizing the presence of one or more ELT signals over this 25-kHz frequency band. Some recommendations are made to improve the spectral characteristics and the performance of the ELT     

CVI反应器气体流动可视化发烟系统

CVI反应器内气体的输运对基体的沉积速度与沉积质量有重要的影响.本文介绍了一种基于TiCl4与H2O反应产生TiO2烟雾而设计的发烟系统,能使模拟CVI反应器内复杂的与不可观察的气体流动现象可视化.该系统结构简单,可操作性强,形成的烟流总流量与密度可调且长时间可视、均匀.流场照片表明其发烟效果很好,能满足CVI反应器内气体流场的显示研究.     

Family of constrained signal detectors for hyperspectral imagery

Generalized likelihood ratio tests (GLRTs) are derived for the problem of detecting targets in hyperspectral images. These detectors are derived under the assumptions that the signals from the materials in the image mix linearly and that the noise in the system is Gaussian. It is also assumed that the abundances of the signals from the various materials in a pixel must sum to one. This constraint models the fact that the material abundances in a pixel are just the fraction of the pixel that they occupy. Under these assumptions, detectors are derived which outperform the detectors derived without the sum-to-one constraint.     

Advances in signal processing technology for electronic warfare

The denial of effective communications by enemy forces during hostile military operations has been a primary concern for military commanders since the inception of radio communications on the battlefield before World War II. Since then, the electromagnetic environment has been in a constant state of evolution toward more sophisticated jam-resistant and convert forms of modulation. For example, exotic modulation techniques employing spread spectrum (SS) signaling are routinely used by our adversaries to provide their communication links an advantage over US and Allied jammers. These same spread spectrum modulation techniques are being refined to provide convert, low probability-of-intercept (LPI) features to the unintended interceptor. The thrust of this paper focuses on developments in the theory and algorithms for detection, characterization, and exploitation of advanced waveforms using new mathematical signal processing tools. Specifically, quadratic time-frequency signal representations, wavelet transforms, and cyclostationary signal processing are introduced. This overview demonstrates the importance of these advanced techniques in a clear and concise manner. Applications and future research activities are described