A Fully Automatic Autofocusing Algorithm for Post-processing ISAR Imaging based on Image Entropy Minimization

1970 ◽  
Vol 110 (4) ◽  
pp. 125-130
Author(s):  
E. D. Kallitsis ◽  
A. V. Karakasiliotis ◽  
G. E. Boultadakis ◽  
P. V. Frangos
Keyword(s):  
Computational Cost ◽  
Angular Acceleration ◽  
Synthetic Aperture ◽  
Post Processing ◽  
Acceptable Range ◽  
Image Entropy ◽  
Isar Imaging ◽  
Fully Automatic ◽  
Simulation Results ◽  
Stepped Frequency

Autofocus is a technique for improving inverse synthetic aperture radar (ISAR) imaging. In this paper, a novel autofocusing method is developed for high-resolution stepped-frequency ISAR. Non-uniform rotational motion is compensated through the proposed post-processing methodology. In this way, the computational cost of polar reformatting process can be circumvented. The proposed CPI-split autofocusing process results in well-focused ISAR images for high angular acceleration periods. Finally, ISAR image entropy dependencies are thoroughly examined through various simulation results, leading to an acceptable range of entropy values for the autofocusing process. Ill. 7, bibl. 9, tabl. 3 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.110.4.305

Simulation and Effectiveness Analysis of Jamming on Inverse Synthetic Aperture Radar

2013 ◽  
Vol 765-767 ◽  
pp. 2762-2765
Author(s):  
Jun Luan ◽  
Yun Neng Yuan
Keyword(s):  
Synthetic Aperture Radar ◽  
Simulation Model ◽  
Synthetic Aperture ◽  
Imaging Radar ◽  
Effectiveness Analysis ◽  
Isar Imaging ◽  
Military Applications ◽  
Simulation Results ◽  
Jamming Effect ◽  
Aperture Radar

nverse synthetic aperture radar (ISAR) is a kind of imaging radar with high capability. It plays an important role in military applications, such as target classification, recognition, identification and accurate weapon navigation. This paper establishes a simulation model of jamming for ISAR system based on the principle of ISAR imaging. Then, the several typical of noise modulation jamming experiments for ISAR are carried out. The simulation results are analysed through evaluating the jamming effect based on the entropy concept.

The Effect of Track-Seeking Motion on Off-Track Vibrations of the Head Gimbal Assembly in HDDs

2017 ◽  
Author(s):  
Guoqing Zhang ◽  
Hui Li ◽  
Shengnan Shen ◽  
Tan Trinh ◽  
Frank E. Talke ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Angular Acceleration ◽  
Sinusoidal Wave ◽  
Interaction Method ◽  
Square Wave ◽  
Structure Interaction ◽  
Head Gimbal Assembly ◽  
Head Positioning ◽  
Mesh Method ◽  
Simulation Results

The effect of track-seeking on off-track residual vibrations of the head-gimbal assembly (HGA) is investigated for air and helium environments using the so-called “fluid dynamic mesh” method and the “fluid-structure interaction” method. Three different angular acceleration profiles (square wave, triangular wave and sinusoidal wave) are investigated as a function of seek time (10 ms and 5 ms). Results show that smoothening of sharp transitions of the seek profile improves the performance of off-track residual vibrations during track-following and shortens the track-following time of the head positioning servo system. In addition, the effect of lateral flow (windage) on off-track residual vibrations during track-following must be considered for a square wave angular acceleration profile. Simulation results show that helium improves the track-following accuracy compared to air due to the lower windage forces acting on the HGA. We observe that the sinusoidal wave angular acceleration performs best among the three angular acceleration profiles investigated. Furthermore, seek time is found to have only a small effect on off-track residual vibrations during track-following.

scholarly journals An Efficient Signal Reconstruction Algorithm for Stepped Frequency MIMO-SAR in the Spotlight and Sliding Spotlight Modes

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Jiajia Zhang ◽  
Guangcai Sun ◽  
Mengdao Xing ◽  
Zheng Bao ◽  
Fang Zhou
Keyword(s):  
Efficient Algorithm ◽  
Low Cost ◽  
Signal Reconstruction ◽  
Multiple Input Multiple Output ◽  
Reconstruction Algorithm ◽  
Synthetic Aperture ◽  
Two Dimensional ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Stepped Frequency

Multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) using stepped frequency (SF) waveforms enables a high two-dimensional (2D) resolution with wider imaging swath at relatively low cost. However, only the stripmap mode has been discussed for SF MIMO-SAR. This paper presents an efficient algorithm to reconstruct the signal of SF MIMO-SAR in the spotlight and sliding spotlight modes, which includes Doppler ambiguity resolving algorithm based on subaperture division and an improved frequency-domain bandwidth synthesis (FBS) method. Both simulated and constructed data are used to validate the effectiveness of the proposed algorithm.

Inverse synthetic aperture ladar imaging with stepped‐frequency continuous waveform

2017 ◽  
Vol 53 (21) ◽  
pp. 1424-1426
Author(s):  
Guangzuo Li ◽  
Ning Wang ◽  
Di Mo ◽  
Ran Wang ◽  
Zenghui Zhang ◽  
...  
Keyword(s):  
Synthetic Aperture ◽  
Stepped Frequency

scholarly journals Effects of Motion Compensation Residual Error and Polarization Distortion on UAV-Borne PolInSAR

2021 ◽  
Vol 13 (4) ◽  
pp. 618
Author(s):  
Zexin Lv ◽  
Fangfang Li ◽  
Xiaolan Qiu ◽  
Chibiao Ding
Keyword(s):  
Motion Compensation ◽  
Residual Error ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Practical Application ◽  
Aerial Vehicle ◽  
Application Potential ◽  
Large Motion ◽  
Simulation Results ◽  
Interferometric Sar

Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) can improve interferometric coherence and phase quality, which has good application potential. With the development of the Mini-SAR system, Unmanned Aerial Vehicle borne (UAV-borne) PolInSAR systems became a reality. However, UAV-borne PolInSAR is easily affected by air currents and other factors, which may cause large motion errors and polarization distortion inevitably exists. However, there are few pieces of research which are about motion compensation residual error (MCRE) and polarization distortion effects on PolInSAR. Though the effects of MCRE on Interferometric SAR (InSAR) and polarization distortion on PolInSAR were studied, respectively, these two parts are independently modeled and analyzed. In this paper, a model that simultaneously considers the effects of these two kinds of errors is proposed, and simulation results are given to validate the model. Then, a quantitative analysis based on a real Quadcopter UAV PolInSAR system is performed according to the model, which is valuable for system design and practical application of the UAV-borne PolInSAR system.

scholarly journals A Robust Discontinuous Phase Unwrapping Based on Least-Squares Orientation Estimator

Electronics ◽  
2021 ◽  
Vol 10 (22) ◽  
pp. 2871
Author(s):  
Gaoxu Deng ◽  
Shiqian Wu ◽  
Shiyang Zhou ◽  
Bin Chen ◽  
Yucheng Liao
Keyword(s):  
Least Squares ◽  
Weighted Least Squares ◽  
Bilateral Filter ◽  
Phase Unwrapping ◽  
Noise Variance ◽  
Post Processing ◽  
Quadratic Error ◽  
Error Norm ◽  
Discontinuous Phase ◽  
Simulation Results

Weighted least-squares (WLS) phase unwrapping is widely used in optical engineering. However, this technique still has issues in coping with discontinuity as well as noise. In this paper, a new WLS phase unwrapping algorithm based on the least-squares orientation estimator (LSOE) is proposed to improve phase unwrapping robustness. Specifically, the proposed LSOE employs a quadratic error norm to constrain the distance between gradients and orientation vectors. The estimated orientation is then used to indicate the wrapped phase quality, which is in terms of a weight mask. The weight mask is calculated by post-processing, including a bilateral filter, STDS, and numerical relabeling. Simulation results show that the proposed method can work in a scenario in which the noise variance is 1.5. Comparisons with the four WLS phase unwrapping methods indicate that the proposed method provides the best accuracy in terms of segmentation mean error under the noisy patterns.

scholarly journals A HYDRODYNAMIC MODEL FOR COMPUTER AIDED HARBOUR ENGINEERING

1988 ◽  
Vol 1 (21) ◽  
pp. 32
Author(s):  
J.L. Monso ◽  
A.S. Arcilla ◽  
J.P. Sierra
Keyword(s):  
Expert System ◽  
Numerical Model ◽  
Important Application ◽  
Automatic Design ◽  
Post Processing ◽  
Order Accuracy ◽  
Planning And Design ◽  
Computer Aided ◽  
Fully Automatic ◽  
Cad Tool

Coastal hydrodynamic analyses are basic for the planning and assessment of activities in that area. An important application of these•analyses is harbour lay-out and location. In this paper, hydrodynamic results of a numerical model based on Boussinesq-type equations are presented in the issue of Computer Aided Harbour Engineering. This model achleves overall second-order accuracy and has efficient modules of pre- and post-processing of information. The model has been used as a CAD tool for the planning and design of Spanish harbours. Its flexibility and economy of operation allow the model to be used, in the future, as a module of a global expert system for CAD harbour lay-out. This global expert system will provide a fully automatic design process. The output of this system will consist in the final optimized harbour configuration, considering all Imposed constraints and requirements.

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