Time filter

Source Type

Xu Z.,University of Adelaide | Xu Z.,Radar and Avionics Institute of AVIC | Kaufmann T.,University of Adelaide | Fumeaux C.,University of Adelaide
IEEE Microwave and Wireless Components Letters | Year: 2014

A shielded stripline structure made from textile materials is introduced as a wearable flexible transmission line for broadband operation. The stripline with a total height of 3.2 mm consists of a foam substrate and silver fabric conductors. For shielding purpose, the structure is truncated on its sides at a total width of 20 mm using embroidered via walls made from conductive thread. The impedance bandwidth and propagation characteristics are investigated through simulation and experiment, demonstrating that the textile stripline can work efficiently and reliably from dc to 8 GHz. Moreover, it is shown that the textile stripline is robust in terms of propagation characteristics, as even when bent up to 90° and 180° it can maintain consistent propagation properties in the whole operation band. A further advantage of the structure is the simple fabrication, arising from the low sensitivity of the structure to width and height tolerances, as well as to the accuracy of the feeding method. Finally, it is shown that the low-loss radio frequency foam substrate material can be replaced with low-cost clothing felt without significant detrimental impact on the efficiency. © 2001-2012 IEEE.

Xia L.,Nanjing Southeast University | Xie J.,Radar and Avionics Institute of AVIC | Hua G.,Nanjing Southeast University
IEEE MTT-S International Microwave Workshop Series on Millimeter Wave Wireless Technology and Applications, IMWS 2012 - Proceeding | Year: 2012

A microwave substrate integrated waveguide (SIW) filter with compact and novel configuration is presented. The SIW filter will be used for the integration with a frequency multiplier. The overall size of the filter is 60mm length and 40mm width and can just enough meet to the need of frequency multiplier. Measured results show that the stopband rejection of filter is more than 45dB, the insertion loss is less than -1dB at the passband of 7.1-8GHz. Using small-angle lateral coupling, the new structure keeps a sharp transition characteristic at the lower sideband just like the traditional waveguide filter and the characteristic have improved at the upper sideband. © 2012 IEEE.

Liu M.,Zhejiang University | Zhang S.,Zhejiang University | Fan Z.,Zhejiang University | Zheng S.,Radar and Avionics Institute of AVIC | Sheng W.,Oklahoma State University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2013

In this paper, H∞ synchronization and state estimation problems are considered for different types of chaotic systems. A unified model consisting of a linear dynamic system and a bounded static nonlinear operator is employed to describe these chaotic systems, such as Hopfield neural networks, cellular neural networks, Chua's circuits, unified chaotic systems, Qi systems, chaotic recurrent multilayer perceptrons, etc. Based on the H∞ performance analysis of this unified model using the linear matrix inequality approach, novel state feedback controllers are established not only to guarantee exponentially stable synchronization between two unified models with different initial conditions but also to reduce the effect of external disturbance on the synchronization error to a minimal H∞ norm constraint. The state estimation problem is then studied for the same unified model, where the purpose is to design a state estimator to estimate its states through available output measurements so that the exponential stability of the estimation error dynamic systems is guaranteed and the influence of noise on the estimation error is limited to the lowest level. The parameters of these controllers and filters are obtained by solving the eigenvalue problem. Most chaotic systems can be transformed into this unified model, and H∞ synchronization controllers and state estimators for these systems are designed in a unified way. Three numerical examples are provided to show the usefulness of the proposed H∞ synchronization and state estimation conditions. © 2012 IEEE.

Sun D.,Nanjing Southeast University | Dou W.,Nanjing Southeast University | You L.,Radar and Avionics Institute of AVIC | Yan X.,Radar and Avionics Institute of AVIC | Shen R.,Radar and Avionics Institute of AVIC
IEEE Antennas and Wireless Propagation Letters | Year: 2011

A broadband cavity-backed proximity-coupled stacked microstrip antenna is presented. Due to the interaction of the two stacked patches, two associated resonances are produced. Unlike conventional proximity-coupled or cavity-backed microstrip antennas, the lower patch and the cavity of this antenna produce the coupled resonances. These devised methods make the antenna act as multiple resonances, conducing to a broadband impedance matching. The simulated and the measured results demonstrate a bandwidth over one octave (VSWR<2). In the meantime, stable radiation patterns are obtained across the entire impedance band. The key parameters of the antenna are studied, and a prototype antenna that has a three-dimensional interconnection structure is provided. © 2011 IEEE.

Liu M.,Zhejiang University | Qi D.,Zhejiang University | Zhang S.,Zhejiang University | Qiu M.,University of Kentucky | Zheng S.,Radar and Avionics Institute of AVIC
Neurocomputing | Year: 2011

This paper is concerned with the problem of multi-sensor optimal H∞ fusion filtering for a class of discrete-time stochastic intelligent systems with missing measurements and time delays. This discrete-time intelligent system model, which is composed of a linear dynamic system and a bounded static nonlinear operator, presents a unified description of delayed or non-delayed intelligent systems composed of neural networks and Takagi and Sugeno (T-S) fuzzy models, Lur'e systems, and linear systems. The missing measurements from multi-sensors are described by a binary switching sequence that obeys a conditional probability distribution. We aim to design both centralized and distributed fusion filters such that, for all possible missing observations, the fusion error is globally asymptotically stable in the mean square, and the prescribed H∞ performance constraint is satisfied. By employing the Lyapunov-Krasovskii functional method with the stochastic analysis approach, several delay-independent criteria, which are in the form of linear matrix inequalities (LMIs), are established to ensure the existence of the desired multi-sensor H∞ fusion filters. An optimization problem is subsequently formulated by optimizing the H∞ filtering performances, which is described as the eigenvalue problem (EVP). Finally, simulation examples are provided to illustrate the design procedure and expected performance. © 2011 Elsevier B.V.

Li X.,Xidian University | Feng D.,Xidian University | Liu H.-W.,Xidian University | Luo D.,Radar and Avionics Institute of AVIC
IEEE Transactions on Aerospace and Electronic Systems | Year: 2014

In this paper, we address the dimension-reduced space-time adaptive processing (STAP) techniques for ground clutter suppression in airborne radar from the viewpoint of approximation theory. The weights in the optimum STAP technique can be naturally expressible as the weight matrix. An efficient dimension-reduced space-time adaptive clutter suppression (STACS) algorithm based on lower-rank approximation to weight matrix is established, which finds a set of space-time separable filters to approximate the optimum STAP processor. By exploiting a lower-rank approximation to weight matrix, we make the quadratic cost function used in the classical optimum STAP processor be converted into a biquadratic cost function. To seek a minimum point of the biquadratic cost function, this paper develops an efficient multistage bi-iterative algorithm and the corresponding multistage dimension-reduced technique with a modular structure, where each stage finds an orthogonal component for approximating to the weight matrix. The effectiveness of the STACS algorithm is tested via several experiments. © 1965-2011 IEEE.

Shen J.,Radar and Avionics Institute of AVIC
2010 9th International Symposium on Antennas Propagation and EM Theory, ISAPE 2010 | Year: 2010

Surrounding environment is one of the main factors which significantly affect the far-field antenna measurement system. To analyze the influences of high voltage wires on far-field antenna measurement, a method is provided that the amplitude and phase of transmission data are compared whether there are high voltage wires beside the antenna measurement field or not. The analysis method and the simulation results are given in this paper. ©2010 IEEE.

Luo C.,Radar and Avionics Institute of AVIC | Li X.,Radar and Avionics Institute of AVIC
IET Conference Publications | Year: 2013

Target detection and tracking in jamming environment is the main problem of airborne radar, while frequency agility is one of the effective measures for radar anti-interference. Received echoes of radar can be divided into the interfered part and the un-interfered part in the state of frequency agility. In this work, target is detected from the un-interfered echoes which are integrated. The setting of detection threshold and the loss of integration are emphatically analysed. Finally, the effectiveness of the proposed method has been validated by experiment data.

Luoding J.W.,Radar and Avionics Institute of AVIC
IET Conference Publications | Year: 2013

One kind of CFAR named VI-CA/OS-CFAR and based on variable test statistics is proposed in this paper. By calculating two variable test statistics including normalized square deviation and mean ratio real-timely, current clutter environment is judged automatically and different kinds of CFAR detectors are selected. Theoretical analysis and verification results by flight data shows that this detector has good performance and robustness in homogeneous clutter, multiple jamming targets or clutter edge environment faced by GMTI in actual use.

Sun D.,Radar and Avionics Institute of AVIC | You L.,Radar and Avionics Institute of AVIC
IEEE Transactions on Antennas and Propagation | Year: 2010

In a proximity-coupled microstrip antenna, when a laminate used is too thick for the antenna layer, the coupling will be decreased. And it is hard to achieve broadband impedance matching. The authors present a method to optimize impedance matching through narrow cavity backed configuration. A prototype antenna is designed with this method and fabricated. Simulation and measurement results indicate that the bandwidth of the antenna 40% (VSWR < 2.0). The antenna has a larger effective coupling as compared with the conventional proximity-coupled antenna without the narrow cavity backed configuration. It is easier to enhance the bandwidth with a thicker laminate. Meanwhile, this antenna is benefit for manufacturing and assembling to an array due to its simple configuration. © 2006 IEEE.

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