Editorial

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Open AccessEditorial

by John E. Ball and Nicolas H. Younan

Electronics 2017, 6(3), 64; https://doi.org/10.3390/electronics6030064 - 01 Sep 2017

Cited by 4 | Viewed by 4212

Radar is a technology used in many aspects of modern life, with many diverse civilian and military applications.[...] Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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Open AccessArticle

Static and Moving Target Imaging Using Harmonic Radar

by Kyle A. Gallagher, Ram M. Narayanan, Gregory J. Mazzaro, Anthony F. Martone and Kelly D. Sherbondy

Electronics 2017, 6(2), 30; https://doi.org/10.3390/electronics6020030 - 04 Apr 2017

Cited by 23 | Viewed by 7889

Abstract

Nonlinear radar exploits the difference in frequency between radar waves that illuminate and are reflected from electromagnetically nonlinear targets. Harmonic radar is a special type of nonlinear radar that transmits one or multiple frequencies and listens for frequencies at or near their harmonics. [...] Read more.

Nonlinear radar exploits the difference in frequency between radar waves that illuminate and are reflected from electromagnetically nonlinear targets. Harmonic radar is a special type of nonlinear radar that transmits one or multiple frequencies and listens for frequencies at or near their harmonics. Nonlinear radar differs from traditional linear radar by offering high clutter rejection and is particularly suited to the detection of devices containing metals and semiconductors. Examples include tags for tracking insects, tags worn by humans for avoiding collisions with vehicles, or for monitoring vital signs. Such tags contain a radio-frequency (RF) nonlinearity, often a Schottky diode, connected to a suitable antenna. Targets with inherent nonlinearities, such as metal contacts, semiconductors, transmission lines, antennas, filters, and ferroelectrics, also respond to nonlinear radar. In this paper, the successful exploitation of harmonic radar for moving target imaging and synthetic aperture imaging of targets, while suppressing clutter signals from linear targets, are presented. Our results demonstrate some unique advantages of harmonic radar over its traditional linear counterpart. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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3884 KiB

Open AccessArticle

Screening Mississippi River Levees Using Texture-Based and Polarimetric-Based Features from Synthetic Aperture Radar Data

by Lalitha Dabbiru, James V. Aanstoos, John E. Ball and Nicolas H. Younan

Electronics 2017, 6(2), 29; https://doi.org/10.3390/electronics6020029 - 31 Mar 2017

Cited by 3 | Viewed by 7246

Abstract

This article reviews the use of synthetic aperture radar remote sensing data for earthen levee mapping with an emphasis on finding the slump slides on the levees. Earthen levees built on the natural levees parallel to the river channel are designed to protect [...] Read more.

This article reviews the use of synthetic aperture radar remote sensing data for earthen levee mapping with an emphasis on finding the slump slides on the levees. Earthen levees built on the natural levees parallel to the river channel are designed to protect large areas of populated and cultivated land in the Unites States from flooding. One of the signs of potential impending levee failure is the appearance of slump slides. On-site inspection of levees is expensive and time-consuming; therefore, a need to develop efficient techniques based on remote sensing technologies is mandatory to prevent failures under flood loading. Analysis of multi-polarized radar data is one of the viable tools for detecting the problem areas on the levees. In this study, we develop methods to detect anomalies on the levee, such as slump slides and give levee managers new tools to prioritize their tasks. This paper presents results of applying the National Aeronautics and Space Administration (NASA) Jet Propulsion Lab (JPL)’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) quad-polarized L-band data to detect slump slides on earthen levees. The study area encompasses a portion of levees of the lower Mississippi River in the United States. In this paper, we investigate the performance of polarimetric and texture features for efficient levee classification. Texture features derived from the gray level co-occurrence (GLCM) matrix and discrete wavelet transform were computed and analyzed for efficient levee classification. The pixel-based polarimetric decomposition features, such as entropy, anisotropy, and scattering angle were also computed and applied to the support vector machine classifier to characterize the radar imagery and compared the results with texture-based classification. Our experimental results showed that inclusion of textural features derived from the SAR data using the discrete wavelet transform (DWT) features and GLCM features provided higher overall classification accuracies compared to the pixel-based polarimetric features. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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1094 KiB

Open AccessFeature PaperArticle

Radar Angle of Arrival System Design Optimization Using a Genetic Algorithm

by Neilson Egger, John E. Ball and John Rogers

Electronics 2017, 6(1), 24; https://doi.org/10.3390/electronics6010024 - 22 Mar 2017

Cited by 3 | Viewed by 6345

Abstract

An approach for using a Genetic Algorithm (GA) to select radar design parameters related to beamforming and angle of arrival estimation is presented in this article. This was accomplished by first developing a simulator that could evaluate the localization performance with a given [...] Read more.

An approach for using a Genetic Algorithm (GA) to select radar design parameters related to beamforming and angle of arrival estimation is presented in this article. This was accomplished by first developing a simulator that could evaluate the localization performance with a given set of design parameters. The simulator output was utilized as part of the GA objective function that searched the solution space for an optimal set of design parameters. Using this approach, the authors were able to more than halve the mean squared error in degrees of the localization algorithm versus a radar design using human-selected design parameters. The results of this study indicate that this kind of approach can be used to aid in the development of an actual radar design. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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1258 KiB

Open AccessArticle

Compressed Sensing ISAR Reconstruction Considering Highly Maneuvering Motion

by Ahmed Shaharyar Khwaja and Mujdat Cetin

Electronics 2017, 6(1), 21; https://doi.org/10.3390/electronics6010021 - 11 Mar 2017

Cited by 10 | Viewed by 5492

Abstract

In this report, we propose compressed sensing inverse synthetic aperture radar (ISAR) imaging in the presence of highly maneuvering motion using a modified orthogonal matching pursuit (OMP) reconstruction algorithm. Unlike existing methods where motion is limited to first- or second-order phase terms, we [...] Read more.

In this report, we propose compressed sensing inverse synthetic aperture radar (ISAR) imaging in the presence of highly maneuvering motion using a modified orthogonal matching pursuit (OMP) reconstruction algorithm. Unlike existing methods where motion is limited to first- or second-order phase terms, we take into account realistic motion of a maneuvering target that can involve a third-order phase term corresponding to the rate of rotational acceleration. In addition, unlike existing fixed dictionary-based methods, which require designing a large dictionary that needs to take into account all of the possible motion parameters, we propose a modified OMP reconstruction method that requires a dictionary only based on the first-order phase term and estimates the secondand third-order phase terms using an optimization algorithm. Simulation examples and comparison with existing methods show the viability of our approach for imaging moving targets consisting of higher order motion. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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899 KiB

Open AccessFeature PaperArticle

Knowledge-Aided Covariance Matrix Estimation in Spiky Radar Clutter Environments

by Jeong H. Bang, William L. Melvin and Aaron D. Lanterman

Electronics 2017, 6(1), 20; https://doi.org/10.3390/electronics6010020 - 09 Mar 2017

Cited by 3 | Viewed by 4882

Abstract

Space-time adaptive processing (STAP) is an important airborne radar technique used to improve target detection in clutter-limited environments. Effective STAP implementation is dependent on accurate space-time covariance matrix estimation. Heterogeneous clutter, including spiky, spatial clutter variation, violates underlying STAP training assumptions and can [...] Read more.

Space-time adaptive processing (STAP) is an important airborne radar technique used to improve target detection in clutter-limited environments. Effective STAP implementation is dependent on accurate space-time covariance matrix estimation. Heterogeneous clutter, including spiky, spatial clutter variation, violates underlying STAP training assumptions and can significantly degrade corresponding detection performance. This paper develops a spiky, space-time clutter model based on the K-distribution, assesses the resulting impact on STAP performance using traditional methods, and then proposes and evaluates the utility of the knowledge-aided parametric covariance matrix estimation (KAPE) method, a model-based scheme that rapidly converges to better represent spatial variation in clutter properties. Via numerical simulation of an airborne radar scenario operating in a spiky clutter environment, we find substantial improvement in probability of detection (

P_{D}

) for a fixed probability of false alarm (

P_{F A}

) for the KAPE method. For example, in the spiky clutter environment considered herein, results indicate a

P_{D}

of 32% for traditional STAP and in excess of 90% for KAPE at a

P_{F A}

of 1E-4, with a corresponding difference of 11.5 dB in threshold observed from exceedance analysis. The proposed K-distributed spiky clutter model, and application and assessment of KAPE as an ameliorating STAP technique, contribute to an improved understanding of radar detection in complex clutter environments. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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Open AccessArticle

Sudoku Inspired Designs for Radar Waveforms and Antenna Arrays

by Travis D. Bufler, Ram M. Narayanan and Kelly D. Sherbondy

Electronics 2017, 6(1), 13; https://doi.org/10.3390/electronics6010013 - 08 Feb 2017

Cited by 8 | Viewed by 6603

Abstract

Sudoku puzzles, often seen in magazines and newspapers, are logic-based challenges where each entry within the puzzle is comprised of symbols adhering to row, column and box constraints. Previously, we had investigated their potential in frequency-hopped waveforms to achieve desirable radar ambiguity functions [...] Read more.

Sudoku puzzles, often seen in magazines and newspapers, are logic-based challenges where each entry within the puzzle is comprised of symbols adhering to row, column and box constraints. Previously, we had investigated their potential in frequency-hopped waveforms to achieve desirable radar ambiguity functions and compared them with random, as well as the more familiar Costas sequences. This paper further examines the properties of Sudoku codes in more detail through computational search and analysis. We examine the co-hit and cross-hit arrays, defined as the correlation between two sequences, to quickly and efficiently evaluate numerous Sudoku puzzles. Additionally, we investigate the use of Sudoku puzzles for antenna applications, including array interleaving, array thinning and random element spacing. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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4259 KiB

Open AccessArticle

Ground-Based 3D Radar Imaging of Trees Using a 2D Synthetic Aperture

by Justin F. Penner and David G. Long

Electronics 2017, 6(1), 11; https://doi.org/10.3390/electronics6010011 - 23 Jan 2017

Cited by 12 | Viewed by 8853

Abstract

Motivated by the desire to gain insight into the details of conventional airborne synthetic aperture radar (SAR) imaging of trees, a ground-based SAR system designed for short-range three-dimensional (3D) radar imaging is developed using a two-dimensional (2D) synthetic aperture. The heart of the [...] Read more.

Motivated by the desire to gain insight into the details of conventional airborne synthetic aperture radar (SAR) imaging of trees, a ground-based SAR system designed for short-range three-dimensional (3D) radar imaging is developed using a two-dimensional (2D) synthetic aperture. The heart of the system is a compact linear frequency modulation-continuous wave (LFM-CW) radar, a custom two-dimensional scan mechanism, and a three-dimensional time-domain backprojection algorithm that generates three-dimensional backscatter images at an over-sampled resolution of 10 cm by 10 cm by 10 cm. The backprojection algorithm is formulated directly in spatial coordinates. A new method for estimating and compensating for signal attenuation within the canopy is used that exploits the backprojection image formation approach. Several three-dimensional C-band backscatter images of different individual trees of multiple species are generated from data collected for trees both in isolation and near buildings. The trees imaged in this study are about 10 m in height. The transformation of the three-dimensional images to airborne SAR images is described and a sample result provided. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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322 KiB

Open AccessArticle

A Compressive-Sensing Inspired Alternate Projection Algorithm for Sparse Array Synthesis

by Daniele Pinchera, Marco Donald Migliore, Mario Lucido, Fulvio Schettino and Gaetano Panariello

Electronics 2017, 6(1), 3; https://doi.org/10.3390/electronics6010003 - 28 Dec 2016

Cited by 22 | Viewed by 5639

Abstract

In this paper, we propose a simple approach for sparse array synthesis. We employ a modified generalized alternate projection algorithm using

ℓ_{1}

-norm constrained minimization in order to achieve the excitation and the position of the elements of a sparse array. The [...] Read more.

In this paper, we propose a simple approach for sparse array synthesis. We employ a modified generalized alternate projection algorithm using

ℓ_{1}

-norm constrained minimization in order to achieve the excitation and the position of the elements of a sparse array. The proposed approach is very flexible, since it deals with power pattern masks and allows the inclusion of the effects of element pattern and mutual coupling. Its implementation is relatively simple, thanks to the possibility to use well-known convex programming techniques. The presented method is particularly suitable for the synthesis of patterns commonly employed in radar systems; the numerical results provided show good performances with respect to concurrent methods available in open literature. Full article

(This article belongs to the Special Issue Radio and Radar Signal Processing)

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