Ground penetration radar using free-electron maser
Author(s):
Alastair D. McAulay
Show Abstract
We propose an airborne ground penetration radar that detects small buried objects. Earth electrical characteristics
are discussed. Radar frequency is considered to penetrate 30 cm into typical ground and bandwidth is
selected to achieve 5 cm range resolution in typical ground. A tunable free-electron maser allows adjustment
to cope with earth variability. Frequency is selected to provide narrow enough beams so that clutter no longer
dominates. The effects of clutter is reduced by beamforming with an array along the wing and by using a
synthetic aperture antenna in the flight direction. The wiggler of the free-electron maser is modified to operate
at low enough frequencies to provide adequate earth penetration. Pulse shaping or signal chirp provides the
bandwidth at the frequency selected. We make an approximate prediction of signal to noise to show feasibility.
Finally we discuss post processing to distinguish objects of interest from clutter.
A computer simulation of a long-range CWFM radar showing the tradeoffs of performance as a function of range
Author(s):
Robert S. Gordy;
Severyn Zoledziowski
Show Abstract
This paper describes a study of the operation of a long range CWFM radar using "System
View" software for modeling and simulation. The System View software is currently offered by
Agilent. The models that were studied include: a model illustrating the basic principle of operation
of the CWFM radar, the range resolution of the radar, the effect of long range processing and the
resultant approach with the tradeoff of detected range resolution due to Doppler frequency shift as a
function of range distance. The study was performed as part of the design of an airborne CWFM
radar. The radar can be designed with a single antenna or a dual antenna. The dual antenna
approach is presented in this paper.
Augmented reality using ultra-wideband radar imagery
Author(s):
Lam Nguyen;
Francois Koenig;
Kelly Sherbondy
Show Abstract
The U.S. Army Research Laboratory (ARL) has been investigating the utility of ultra-wideband (UWB) synthetic
aperture radar (SAR) technology for detecting concealed targets in various applications. We have designed and built a
vehicle-based, low-frequency UWB SAR radar for proof-of-concept demonstration in detecting obstacles for
autonomous navigation, detecting concealed targets (mines, etc.), and mapping internal building structures to locate
enemy activity. Although the low-frequency UWB radar technology offers valuable information to complement other
technologies due to its penetration capability, it is very difficult to comprehend the radar imagery and correlate the
detection list from the radar with the objects in the real world.
Using augmented reality (AR) technology, we can superimpose the information from the radar onto the video
image of the real world in real-time. Using this, Soldiers would view the environment and the superimposed graphics
(SAR imagery, detection locations, digital map, etc.) via a standard display or a head-mounted display. The
superimposed information would be constantly changed and adjusted for every perspective and movement of the user.
ARL has been collaborating with ITT Industries to implement an AR system that integrates the video data captured from
the real world and the information from the UWB radar. ARL conducted an experiment and demonstrated the real-time
geo-registration of the two independent data streams. The integration of the AR sub-system into the radar system is
underway. This paper presents the integration of the AR and SAR systems. It shows results that include the real-time
embedding of the SAR imagery and other information into the video data stream.
Human polarimetric micro-doppler
Author(s):
David Tahmoush;
Jerry Silvious
Show Abstract
Modern radars can pick up target motions other than just the principle target Doppler; they pick out the
small micro-Doppler variations as well. These can be used to visually identify both the target type as well
as the target activity. We model and measure some of the micro-Doppler motions that are amenable to
polarimetric measurement.
Understanding the capabilities and limitations of radar systems that utilize micro-Doppler to measure
human characteristics is important for improving the effectiveness of these systems at securing areas. In
security applications one would like to observe humans unobtrusively and without privacy issues, which
make radar an effective approach. In this paper we focus on the characteristics of radar systems designed
for the estimation of human motion for the determination of whether someone is loaded.
Radar can be used to measure the direction, distance, and radial velocity of a walking person as a function
of time. Detailed radar processing can reveal more characteristics of the walking human. The parts of the
human body do not move with constant radial velocity; the small micro-Doppler signatures are timevarying
and therefore analysis techniques can be used to obtain more characteristics. Looking for
modulations of the radar return from arms, legs, and even body sway are being assessed by researchers. We
analyze these techniques and focus on the improved performance that fully polarimetric radar techniques
can add. We perform simulations and fully polarimetric measurements of the varying micro-Doppler
signatures of humans as a function of elevation angle and azimuthal angle in order to try to optimize this
type of system for the detection of arm motion, especially for the determination of whether someone is
carrying something in their arms. The arm is often bent at the elbow, providing a surface similar to a
dihedral. This is distinct from the more planar surfaces of the body and allows us to separate the signals
from the arm (and knee) motion from the rest of the body. The double-bounce can be measured in
polarimetric radar data by measuring the phase difference between HH and VV. Additionally, the cross-pol
and co-pol Doppler signatures are analyzed, showing that the HH polarization may perform better on
dismounts in open grass.
Polarization dynamics and interference analysis for wideband signals
Author(s):
Glafkos Stratis;
Ghassan Maalouli;
David Manzi;
Rafael Ihly
Show Abstract
In this paper we investigate the impact of polarization dynamics in interference analysis in urban areas;
furthermore we connect the polarization dynamics with different scattering environments and frequencies
which introduces more flexibility for diversity schemes and the implementation of concepts such as
polarization MiMO etc. The key idea is that once a non-monochromatic wave impinges upon buildings, the
spectral components of the wave are variably depolarized upon scattering. In wideband signals we show
that polarization dynamics are different in various frequencies and different environments and that
introduces another degree of freedom to reduce interference, to add diversity and therefore improve
capacity.
Phenomenology of fully polarimetric imaging radars
Author(s):
Jorge V. Geaga
Show Abstract
We have previously reported on the analysis of fully polarimetric single look and multilook SIR-C data. We
have reported that the Stokes(Kennaugh) matrices for each pixel have one and only one eigenvector that satisfies
the property of a Stokes Vector. We now report on new analysis of fully polarimetric SIR-C data and ISAR
data from the Submillimeter-Wave Technology Laboratory at the University of Massachussetts Lowell which
shows that the remaining three eigenvectors of the Stokes matrix are quaternions which represent rotations.
Furthermore, the three direction vectors of these quaternions form an orthogonal cartesian set of axes. We also
discuss relationships between the angles of the Stokes Vector with the Euler parameters initially proposed by
Huynen.
Visualizing and displaying radar micro-doppler data
Author(s):
David Tahmoush;
Jerry Silvious
Show Abstract
A time-integrated range-Doppler map shows the micro-Doppler characteristics of targets in radar images
that enable an operator to classify different target types and to classify different activities being done by the
targets. A time-integrated range-Doppler map is a compilation of range-Doppler maps over time that results
in a spectrogram-like characterization of Doppler while maintaining the range information as well. These
are compiled from the range-Doppler maps by taking the maximum value for each pixel over a time range.
The time resolution is overlapped onto the range resolution, which is in effect a rotation of the traditional
spectrogram which compresses range. This type of radar imaging also allows multiple subjects to be
viewed simultaneously and avoids tracking issues in spectrogram creation. The display of range-Doppler
movies or spectrograms with range extent is also demonstrated.
Polarisation transform analysis for detection of shallow buried non-metallic landmines in microwave X-band region
Author(s):
K. C. Tiwari;
D. Singh;
M. Arora
Show Abstract
Alternative approaches and models continue to be investigated and evolved to correctly locate and
identify a buried mine with minimum risk. Though microwave remote sensing based detection of
shallow buried landmines provides such a risk free alternative, it is a highly complex and
computationally intensive task involving several parameters. The present paper deals with the use of
data obtained in multiple polarizations and their transforms approximating rough surface conditions
in sand for landmine detection. Data in both HH and VV polarizations in microwave X-band
frequency (10 GHz, 3cm) was generated using a live landmine (with explosives less fuze) for the
present study under field conditions. Various transforms such as image differencing, image ratioing
and polarization discriminant ratio (PDR) were studied for its effect on landmine detection.
However, it was found that most of the clutter and noise gets suppressed on using a transform
obtained by subtracting the difference of data in two polarizations from its sum. The surface
roughness conditions have been approximated as available in western parts of India and which are
suitable for application of microwave radar remote sensing for detection of minefields. With the
advent of satellites providing data in various polarizations, it has now become relevant to investigate
methods which can be used for landmine detection using polarization techniques. The proposed
analysis is expected to be useful in future in detection of landmines using multi-polarization satellite
data in microwave X-band in deserts such as those existing in the western borders of India.
Radar cross section statistics of dismounts at Ku-band
Author(s):
Ann Marie Raynal;
Bryan L. Burns;
Tobias J. Verge;
Douglas L. Bickel;
Ralf Dunkel;
Armin W. Doerry
Show Abstract
Knowing the statistical characteristics of a target's radar cross-section (RCS) is crucial to the success of radar target
detection algorithms. A wide range of applications currently exist for dismount (i.e. human body) detection and
monitoring using ground-moving target indication (GMTI) radar systems. Dismounts are particularly challenging to
detect. Their RCS is orders of magnitude lower than traditional GMTI targets, such as vehicles. Their velocity of about 0
to 1.5 m/s is also much slower than vehicular targets. Studies regarding the statistical nature of the RCS of dismounts
focus primarily on simulations or very limited empirical data at specific frequencies. This paper seeks to enhance the
existing body of work on dismount RCS statistics at Ku-band, which is currently lacking, and has become an important
band for such remote sensing applications. We examine the RCS probability distributions of different sized humans in
various stances, across aspect and elevation angle, for horizontal (HH) and vertical (VV) transmit/receive polarizations,
and at diverse resolutions, using experimental data collected at Ku-band. We further fit Swerling target models to the
RCS distributions and suggest appropriate detection thresholds for dismounts in this band.
Radar cross section statistics of ground vehicles at Ku-band
Author(s):
Ann Marie Raynal;
Douglas L. Bickel;
Michael M. Denton;
Wallace J. Bow;
Armin W. Doerry
Show Abstract
Knowing the statistical characteristics of a target's radar cross-section (RCS) is crucial to the success of radar target
detection algorithms. Open literature studies regarding the statistical nature of the RCS of ground vehicles focus
primarily on simulations, scale model chamber measurements, or limited experimental data analysis of specific vehicles
at certain frequencies. This paper seeks to expand the existing body of work on ground vehicle RCS statistics at Ku-band
for ground moving target indication (GMTI) applications. We examine the RCS probability distributions of civilian and
military vehicles, across aspect and elevation angle, for HH and VV polarizations, and at diverse resolutions, using
experimental data collected at Ku-band. We further fit Swerling target models to the distributions and suggest
appropriate detection thresholds for ground vehicles in this band.
Human activity classification using Hilbert-Huang transform analysis of radar Doppler data
Author(s):
Dustin P. Fairchild;
Ram M. Narayanan
Show Abstract
The automatic identification of human activities has become an area of interest in recent years. Identifying
human activities is useful in various applications, such as through-barrier identification of intruders and non-contact
monitoring of patients in hospitals. Numerous methods of human activity classification have been
proposed in the past, including the use of Artificial Neural Networks (ANNs) and Support Vector Machines
(SVMs). Most research in this area thus far has utilized the Short-Time Fourier Transform (STFT) as a method
of obtaining the feature vectors necessary for classification. In this paper, we propose the use of the Empirical
Mode Decomposition (EMD) algorithm as an alternative approach for obtaining feature vectors from human
micro-Doppler signals and utilize an SVM for classification. Since the micro-Doppler signature is unique to
a specific activity, the EMD outputs can be utilized as feature vectors. By utilizing the EMD algorithm in
conjunction with an SVM, binary classification of human activities have shown to yield accurate results. Because
SVMs were originally developed to solve the binary classification problem, additional steps must be taken in order
to extend the problem to identify multiple classes. In this paper, two methods for multi-class classification will
be demonstrated and compared. The first method is the one-against-all approach and the second is a decision
tree based approach. In both cases, a high degree of accuracy is achieved.
Comparison of three radar systems for through-the-wall sensing
Author(s):
X. Wang;
J. Li;
Y. Yang;
C. Lu;
C. Kwan;
B. Ayhan
Show Abstract
In this paper, we summarize our efforts of using three different radars (impulse radar, swept frequency radar,
and continuous-wave radar) for through-the-wall sensing. The purpose is to understand the pros and cons of each
of the three radars. Through extensive experiments, it was found that the radars are complementary and multiple
radars are needed for different scenarios of through-the-wall target detection and tracking.
A fast data acquisition and processing scheme for through-the-wall radar imaging
Author(s):
Francesco Soldovieri;
Raffaele Solimene;
Fauzia Ahmad
Show Abstract
High-resolution through-the-wall radar imaging (TWRI) systems can provide a high degree of situational awareness in
urban sensing applications. However, such systems generate huge amounts of data, owing to the use of wideband signals
and large arrays to achieve high resolutions in range and crossrange. This makes both data acquisition and processing
challenging. In this paper, we present fast data acquisition and processing schemes for TWRI. We use compressive
sensing and novel concepts of microwave tomography to establish a reduced-redundancy spatial and frequency
measurement configuration, which provides clear advantages in terms of measurement time and algorithm complexity.
Performance validation of the proposed strategy is provided using laboratory experiments.
Target localization with a single-antenna monostatic radar via multipath exploitation
Author(s):
Pawan Setlur;
Graeme E. Smith;
Fauzia Ahmad;
Moeness G. Amin
Show Abstract
In urban sensing and through-the-wall radar, the existence of targets in proximity to walls or buildings results in
multipath returns. In this paper, we exploit the multipath from the walls to achieve target localization with a single
sensor. We deal with sparse scenes of single targets. A time-of-arrival wall association algorithm is derived to relate
target multipath returns to the respective walls, followed by a nonlinear least squares optimization to determine the target
location. Simulated and experimental data are used to validate the proposed algorithms.
Real-time subsurface imaging algorithm for intra-wall characterization
Author(s):
Wenji Zhang;
Ahmad Hoorfar;
Christopher Thajudeen
Show Abstract
For through-the-wall radar imaging (TWRI), an accurate characterization of the wall is important for the enhancement of
imaging of the target behind the wall. In this paper we cast the two-dimensional (2D) wall interior structure imaging as a
subsurface imaging problem. The region between the front and back walls is imaged using a novel linear inverse
scattering algorithm for 2D subsurface imaging. The imaging algorithm is based on first order Born approximation and
exploiting halfspace Green's function. The exploding reflection model is employed and then the Green's function is
expanded in the spectral domain to formulate a novel real time intra-wall imaging algorithm. The linearization of the
inversion scheme and the employment of FFT/IFFT in the imaging formula make the imaging algorithm suitable in
several applications concerning the diagnostics of large probed domain and allow real time processing. A numerical
result is presented to show the effectiveness and efficiency of the proposed algorithm for real time intra-wall
characterization.
Wave propagation through complex wall structures
Author(s):
Blake Anderton;
Ryan White;
Eric Williams;
Jonathan Hess;
Steve Manson;
Glafkos Stratis
Show Abstract
Analytical expressions for Fresnel reflection and transmission coefficients have been extensively used in
ray-tracing simulation. Although these tools accurately predict the field for simple homogeneous wall
structures, it is difficult, if not impossible, to extend such an analysis to find reflection and transmission
coefficients for walls composed of dielectric and imperfectly conducting materials or complex,
inhomogeneous structures. In principle, Fresnel theory is considered a high-frequency method, but in
practical problems (such as walls with metallic rebars and similar applications), transmission does not
monotonically decrease with incidence angle, and Fresnel theory does not apply. In this paper, we use
the FDTD method to extend the theoretical Fresnel formulation to certain types of problems where
Fresnel theory does not apply. We find that the presence of rebar affects transmission characteristics
much more significantly than permittivity or wall depth. We initially verify the FDTD method with
simple theoretical applications, and then we go further in more complicated cases; we furthermore
extend our analysis to polarization effects that occur from such inhomogeneities.
Novel antennas based upon extraordinary transmission metamaterial lenses
Author(s):
M. Navarro-Cía;
M. Beruete;
F. Falcone;
M. Sorolla
Show Abstract
Novel antennas exhibiting directivity enhancement by using a short focal length plano-concave lens engineered by
stacked subwavelength hole arrays in such a way that an effective negative index of refraction is obtained. An additional
unexpected property of this design is that it opens the possibility to achieve an index close to zero, n → 0, arisen from ε-
and μ-near-zero extreme values. Our original design works with evanescent modes in comparison with the well known
classical metallic lenses operating with propagating modes. In our case, this leads to a negative index of refraction,
whereas metallic lenses exhibit a positive but less than one index of refraction. It is demonstrated by means of a simple
design based on dispersion diagram and ray tracing an easy and correct method for rather accurate results. Also, an
optimization of the hole diameter or longitudinal lattice constant to achieve not only n = -1, but also free space matching
is possible simultaneously. A power enhancement up to 24 dB with cross-polarization below -30 dB with regards to co-polar,
when the lens is applied as antenna radiation beamforming has been measured. For the case of index close to zero,
n → 0, the power enhancement is 27 dB whereas the cross-polarization remains -17 dB with regards to co-polar. New
improvements are under analysis in order to determine if this technology could be competitive with current state of the
art of waveguide lenses and Fresnel zone plate lenses.
Transformation optics compressed rotman lens implemented with complementary metamaterials
Author(s):
John Hunt;
Nathan Kundtz;
Bruce Sun;
David R. Smith
Show Abstract
The solutions to the Rotman lens design equations constrain the minimum size of the device. Here we use
Transformation Optics to compress a transmission line based Rotman lens by 27 percent along the optical axis
while maintaining the beam steering range, gain and side lobe amplitudes over the full frequency range of the
original lens. The transformation applied requires an anisotropic magnetic response, which is achieved in the
transmission line context using complementary electric dipole structures patterned into the top conductor of
the lens. The non-resonant complementary metamaterial elements provide an anisotropic, eective magnetic
permeability with values that can be varied across a spatial region by varying the geometry of each element.
Metamaterial-driven lens optics for new beam forming patterns
Author(s):
Amir I. Zaghloul;
Steven J. Weiss
Show Abstract
This paper discusses the general concept of using metamaterials in microwave lenses. The different optics afforded by
the inclusion of metamaterials in the lens structure produce new features such as reduced size and new beam formations.
The use of negative refractive index materials is discussed in reference to the original concept of the perfect lens, leading
to the Rotman lens and the Luneburg lens. In Rotman lens, negative refractions help reducing the lens size and a
broadband electromagnetic band gap (EBG) surface is used to prevent reflections off the sidewalls. Verification of
negative refraction and simulation of isotropic material performance are presented, as well as an example of broadening
the band of an EBG surface.
Super-resolution technologies for all-weather sense and avoidance (SAA) radar
Author(s):
Yan Rockee Zhang;
Zhengzheng Li;
Shang Wang;
Yu Pan;
Hernan Suarez
Show Abstract
The sense and avoidance (SAA) and due-regard radar systems have strict requirements on size, weight and power (SWaP)
and target localization accuracies. Also, the multi-mission capabilities with both weather and hard targets are critical to
the survivability of unmanned aerial vehicles (UAV) in the next generation national airspace. The aperture limitations of
the aircraft sensor installation, however, have prevented large antennas/arrays to be used. The tradeoffs among
frequencies, resolutions and detection range/accuracies have not been fully addressed. Innovative concepts of
overcoming the aperture limitation by using a special type of super-resolution technology are introduced. The first
technique is based on a combination of thinned antenna array, an extension to the traditional Multiple Signal
Classification (MUSIC) technique, and applying a two-dimensional sidelobe mitigation technique. To overcome the
degradation of MUSIC-type of approach due to coherent radar signals, a special waveform optimization procedure is
used. The techniques for mitigating artifacts due to "thinned" array are also introduced. Simulated results of super-resolution
techniques are discussed and evaluated, and the capability of separating multiple targets within aperture-constrained
beamwidth is demonstrated. Moreover, the potential capabilities of autonomous weather hazard avoidance
are also analyzed.
SAR vibrometry using the pseudo-subspace approach based on the discrete fractional Fourier transform
Author(s):
Qi Wang;
Balu Santhanam;
Matthew Pepin;
Tom Atwood;
Majeed M. Hayat
Show Abstract
In synthetic-aperture radar (SAR), ground-target vibrations introduce a phase modulation in the returned signals,
a phenomenon often referred to as the micro-Doppler effect. Earlier work has shown that the problem of
estimating common ground-target vibrations can be transformed into the problem of successively estimating
chirp parameters of the returned signal in properly sized subapertures. Recently, a method based on the discrete
fractional Fourier transform (DFRFT) was proposed, in conjunction with the subaperture framework, to estimate
target vibrations in the absence of noise. In this paper a pseudo-subspace approach is employed to extend the
applicability of the DFRFT-based vibration-estimation method to signals that are corrupted by white noise.
The new algorithm first calculates the inverse discrete Fourier transform of row and column projections of
the magnitude of the DFRFT spectrum of the SAR returned signal to obtain two vectors. Next, covariance
matrices are estimated from the sample covariance matrices of the two vectors. A pseudo-subspace approach is
then applied to the covariance matrices to yield the pseudo-spectra. The chirp rate of the signal is estimated
by finding the principle frequency component in the corresponding pseudo-spectrum. Monte-Carlo simulations
demonstrate that the proposed method generally offers improved mean-square-error performance in the presence
of noise compared to the direct DFRFT-based method.
Generation of FM signals with quasi-chirp behavior using three-dimensional chaotic flows
Author(s):
Benjamin C. Flores;
Chandra S. Pappu;
Berenice Verdin
Show Abstract
In previous work, we constructed wideband FM signals for high range resolution applications using the non-linear
Lorenz system, which has a set of three state variables and three control parameters. The FM signals were generated
using any one of the three state variables as the instantaneous frequency which was then controlled by adjusting the
values of the parameters in the chaotic regime. We now determine the spectral characteristics of the Lorenz FM signal
and compare the spectral characteristics to those of a similar FM signal based on the Lang-Kobayashi system. We show
that for either chaotic system, the local linearity of the attractor yields an FM signal with a distinct chirp behavior.
Irrespective of the statistical independence of the chaotic flow samples, we show that the chaotic FM signal follows
Woodward's theorem in the sense that the spectrum of the FM signal follows the shape of the probability density
function of the state variable. The chirp rate of the FM signal can be controlled through a time-scale parameter that
compresses or expands the chaotic flow. As the chaotic flow evolves in time, so does the spectrum of the corresponding
FM signal, which experiences changes in center frequency and bandwidth. We show that segments of the signal with a
high chirp rate can be significantly compressed to achieve high range-Doppler resolution. The ability to change the
center frequency and the shape of the spectrum is interpreted as added frequency agility.
PADF RF localization criteria for multimodel scattering environments
Author(s):
Miguel Gates;
Christopher Barber;
Rastko Selmic;
Huthaifa Al-Issa;
Raul Ordonez;
Atindra Mitra
Show Abstract
This paper provides a summary of recent results on a novel multi-platform RF emitter localization technique denoted as
Position-Adaptive RF Direction Finding (PADF). This basic PADF formulation is based on the investigation of iterative
path-loss based (i.e. path loss exponent) metrics estimates that are measured across multiple platforms in order to
robotically/intelligently adapt (i.e. self-adjust) the location of each distributed/cooperative platform. Recent results at the
AFRL indicate that this position-adaptive approach shows potential for accurate emitter localization in challenging
embedded multipath environments (i.e., urban environments). As part of a general introductory discussion on PADF
techniques, this paper provides a summary of our recent results on PADF and includes a discussion on the underlying
and enabling concepts that provide potential enhancements in RF localization accuracy in challenging environments.
Also, an outline of recent results that incorporate sample approaches to real-time multi-platform data pruning is included
as part of a discussion on potential approaches to refining a basic PADF technique in order to integrate and perform
distributed self-sensitivity and self-consistency analysis as part of a PADF technique with distributed robotic/intelligent
features. The focus of this paper is on the experimental performance analysis of hardware-simulated PADF
environments that generate multiple simultaneous mode-adaptive scattering trends. We cite approaches to addressing
PADF localization performance challenges in these multi-modal complex laboratory simulated environments via
providing analysis of our multimodal experiment design together with analysis of the resulting hardware-simulated
PADF data.
Clutter locus equation for more general linear array orientation
Author(s):
Douglas L. Bickel
Show Abstract
The clutter locus is an important concept in space-time adaptive processing (STAP) for ground moving target
indicator (GMTI) radar systems. The clutter locus defines the expected ground clutter location in the angle-Doppler
domain. Typically in literature, the clutter locus is presented as a line, or even a set of ellipsoids, under certain
assumptions about the geometry of the array. Most often, the array is assumed to be in the horizontal plane
containing the velocity vector. This paper will give a more general 3-dimensional interpretation of the clutter locus
for a general linear array orientation.
Quick signal detection and dynamic resource allocation scheme for ultra-wideband radar
Author(s):
Xiangming Kong;
Ahmed Mohin
Show Abstract
A new scheme for sampling and detecting as well as reconstructing analog signals residing in a wide spectrum band
through compressive sensing is proposed. By applying compressive sensing techniques, this scheme is able to detect
signals quickly over very wide bandwidth. Unlike existing compressive sensing approaches which carry out the
sampling and detection/reconstruction procedures separately, in this scheme, the sampling process and the
detection/reconstruction process has close interaction. Once a new signal is detected, resources are allocated for
further processing. Previously detected signals are then removed as interference to facilitate new signal detection.
Hence, this scheme can quickly adapt to the variation of the environment. Moreover, it avoids the complex iterative
optimization procedure in reconstruction and instead uses one step detection procedure to reaches real-time handling
of signals. Simulation results show that it can closely track the spectrum change even when the signal is weak.
Adaptive detection of range-spread targets by the generalized detector
Author(s):
Vyacheslav Tuzlukov
Show Abstract
In this paper, we address an adaptive detection of range-spread targets or targets embedded in Gaussian noise with unknown
covariance matrix by the generalized detector (GD) based on the generalized approach to signal processing
(GASP) in noise. We assume that cells or secondary data that are free of signal components are available. Those secondary
data are supposed to process either the same covariance matrix or the same structure of the covariance matrix of the
cells under test. In this context, under designing GD we use a two-step procedure. The criteria lead to receivers ensuring
the constant false alarm rate (CFAR) property with respect to unknown quantities. A thorough performance assessment
of the proposed detection strategies highlights that the two-step design procedure of decision-making rule in accordance
with GASP is to be preferred with respect to the plain one. In fact, the proposed design procedure leads to GD that achieves
significant improvement in detection performance under several situation of practical interest. For estimation purposes,
we resort to a set of secondary data. In addition to the classical homogeneous scenario, we consider the case wherein
the power value of primary and secondary data vectors is not the same. The design of adaptive detection algorithms based
on GASP in the case of mismatch is a problem of primary concern for radar applications. We demonstrate that two-step
design procedure based on GASP ensures minimal loss.
Radar signature acquisition using an indigenously designed noise radar system
Author(s):
A. P. Freundorfer;
J. Y. Siddiqui;
Y. M. M. Antar;
T. Thayaparan
Show Abstract
A new design of a noise radar system is proposed with capabilities to measure and acquire the radar signature of various targets. The proposed system can cover a noise bandwidth of near DC to 30 GHz. The noise radar signature measurements were conducted for selective targets like spheres and carpenter squares with and without dielectric bodies for a noise band of 400MHz-3000MHz. The bandwidth of operation was limited by the multiplier and the antennae used. The measured results of the target signatures were verified with the simulation results.
High-resolution noise radar using slow ADC
Author(s):
Konstantin Lukin;
Pavlo Vyplavin;
Oleg Zemlyanyi;
Sergiy Lukin;
Volodymyr Palamarchuk
Show Abstract
Conventional digital signal processing scheme in noise radars has some limitations related to combination of high
resolution and high dynamic range. Those limitations are caused by a tradeoff in performance of currently available
ADCs: the faster is ADC the smaller is its depth (number of bits) available. Depth of the ADC determines relation
between the smallest and highest observable signals and thus limits its dynamic range. In noise radar with conventional
processing the sounding and reference signals are to be digitized at intermediate frequency band and to be processed
digitally. The power spectrum bandwidth of noise signal which can be digitized with ADC depends on its sampling rate.
The bandwidth of radar signal defines range resolution of any radar: the wider the spectrum the better the resolution.
Actually this is the main bottleneck of high resolution Noise Radars: conventional processing doesn't enable to get both
high range resolution and high dynamic range. In the paper we present a way to go around this drawback by changing
signal processing ideology in noise radar. We present results of our consideration and design of high resolution Noise
Radar which uses slow ADCs. The design is based upon generation of both probing and reference signals digitally and
realization of their cross-correlation in an analog correlator. The output of the correlator is a narrowband signal that
requires rather slow ADC to be sampled which nowadays may give up to 130 dB dynamic range.
Direct digitization of ultra-wideband (UWB) noise signals using frequency band folding
Author(s):
Russell Vela;
Gordon Woodington;
Mark R. Deluca;
Ram M. Narayanan
Show Abstract
Frequency spectrum responses of targets are of importance in UWB radar for target identification and recognition.
As technology's digitization rate of analog sources increases, direct acquisition of wider bandwidths is becoming
possible. Through conversion to the frequency domain, wider bandwidth spectral responses for targets can
be produced. However, to directly digitize higher frequencies with UWB signals directly (i.e., ≥ 4 GHz), the
technology is somewhat limited. This paper will present a technique which utilizes both hardware and software
to produce a lower bandwidth signal (e.g., 1.5 GHz), which contains larger spectral bandwidth information (e.g.,
6 GHz). The technique utilizes a double band folding methodology implemented in hardware, or software, to
translate larger bandwidths into lower bandwidths for direct digitization. The generated lower bandwidth will
have a unique spectral response containing the superimposed amplitudes of the larger bandwidth transmitted
signal. This folded spectrum can then be used in applications such as target recognition and identification.
Simulated and experimental results will be presented to evaluate the advantages and disadvantages of such an
approach.
Cross-correlation analysis of noise radar signals propagating through lossy dispersive media
Author(s):
Sonny Smith;
Ram M. Narayanan
Show Abstract
Correlation detection is an essential ingredient in noise radar. Such detection is achieved via coherent signal
processing, which, conceivably, gives the best enhancement in the signal-to-noise ratio. Over the years, much
research and progress has been made on the use of noise radar systems as means for effective through-wall
detection. Information about a particular target's range and/or velocity are often acquired by comparing and
analyzing both transmit and received waveforms. One of the widely used techniques employed to measure the
degree of similarity between the two signals is correlation. The aforementioned methodology determines to what
extent two waveforms match by multiplying and shifting one signal with respect to a time-lagged version of the
second signal. This feature of correlation is very applicable to radar signals since a received signal from a target
is delayed on the path of return to the receiving antenna. Transmission and reflection impairments will distort
the propagating signals and degrade the correlation. Thus, it is essential that we try to study the effects that
such degradations can have on the signals that will be used in the correlation process. This paper presents some
concepts of a noise radar system, simulation studies, and an analysis of the results ascertained.
Super-resolution techniques for velocity estimation using UWB random noise radar signals
Author(s):
Muhammad Dawood;
Nafish Quraishi;
Ana V. Alejos
Show Abstract
The Doppler spread pertaining to the ultrawideband (UWB) radar signals from moving target is directly proportional to
the bandwidth of the transmitted signal and the target velocity. Using typical FFT-based methods, the estimation of true
velocities pertaining to two targets moving with relatively close velocities within a radar range bin is problematic. In this
paper, we extend the Multiple Signal Classification (MUSIC) algorithm to resolve targets moving velocities closer to
each other within a given range bin for UWB random noise radar waveforms. Simulated and experimental results are
compared for various target velocities using both narrowband (200MHz) and wideband (1GHz) noise radar signals,
clearly establishing the unbiased and unambiguous velocity estimations using the MUSIC algorithm.
A technique for the generation of customizable ultra-wideband pseudo-noise waveforms
Author(s):
Russell Vela;
David Erisman;
Ram M. Narayanan
Show Abstract
Noise excitation sources in radar systems have become increasingly useful in applications requiring wideband
spectral responses and covertness. However, in applications requiring spectral controllability, traditional analog
noise sources prove troublesome and require additional hardware such as sets of digital filters whose own spectral
characteristics must also be accounted for. In an effort to reduce these issues and increase the applications of
noise waveforms, a technique for generating a fully controllable pseudo-noise waveform is presented. This pseudo-noise
waveform will be generated through the use of a multi-tone waveform. By randomizing the phase angles
and setting the appropriate amplitudes to the individual tones, the result is a waveform whose temporal pattern
resembles noise and frequency response is broadband. The capabilities of this digitally produced pseudo-noise
multi-tone waveform is presented by optimization via a water-filling technique, thereby producing a flat spectral
response for a user defined amplitude, effectively removing the spectral effects of the radar components. This
optimized waveform is used to present methods for increasing signal to noise ratio (SNR) of cross-correlated
responses of the waveform through the application of window functions to the waveform. As a whole, this paper
showcases the ability to use this pseudo-noise multi-tone waveform for complete ultra-wideband (UWB) spectral
control through water-filling and a method for increasing SNR of the cross correlated response of the transmitted
and received radar waveform for a bandwidth of 2.5 GHz ranging from 2 to 4.5 GHz.
Brillouin precursor waveforms pertaining to UWB noise radar signals propagating through dispersive media
Author(s):
M. Dawood;
A. V. Alejos
Show Abstract
The electromagnetic (EM) waves propagating through causal, linear, and lossy dispersive media (soil, foliage, plasma,
water, biological tissue, etc.), experience frequency-dependent attenuation and phase distortion. This has assumed
significant importance for systems operating with ultrawideband (UWB) spectrum. This paper analyzes the dynamical
evolution of UWB noise radar signals through dispersive media. The effects on the signal propagation due to the
evolution of the Brillouin precursor through dispersive media are discussed. The evolving waveforms are then compared
with the Brillouin precursor due to rectangular sine-modulated deterministic signals. The advantages of random noise
waveforms through dispersive media are also discussed.
A technique for the extraction of ultra-wideband (UWB) signals concealed in frequency band folded responses
Author(s):
Russell Vela;
Ram M. Narayanan;
David Erisman
Show Abstract
Ultra-wideband (UWB) excitation sources in radar systems have allowed for enhancement in capabilities such as
target spectral response, clutter suppression, and range resolution. While generation of generic UWB signals has
become easily achievable, direct acquisition, or digitization, of these bandwidths (≥ 4 GHz) is not. To account for
this, many UWB radar systems implement a single or multi-stage band folding technique in the receiver hardware
chain which allows for the direct digitization of the UWB waveform at a smaller bandwidth (e.g., 4 GHz into
1 GHz). While the lower bandwidth allows for larger than narrowband capabilities, it reduces desired features
such as range resolution (e.g., 3.75 cm to 15 cm). In an effort to address this problem, and allow for utilization of
full bandwidth of an UWB waveform, this paper presents a signal processing technique which utilizes hardware
band folding to wrap a spectrally unique UWB multi-tone waveform into a lower frequency, lower bandwidth
signal allowing for both direct digitization and conservation of UWB features. The signal processing technique
utilizes the multi-tone waveform to generate an UWB signal composed of sections whose separate spectral peaks
fold into the inner ΔF regions of the previous band. It will be shown, that through reassignment of these peaks,
as well as the phase, to the individual frequencies, the intended UWB capabilities can be restored.
SAR imagery using chaotic carrier frequency agility pulses
Author(s):
Xiaojian Xu;
Xiangzhi Feng
Show Abstract
Synthetic aperture radar (SAR) systems are getting more and more applications in both civilian and military remote
sensing missions. With the increasing deployment of electronic countermeasures (ECM) on modern battlefields, SAR
encounters more and more interference jamming signals. The ECM jamming signals cause the SAR system to receive
and process erroneous information which results in severe degradations in the output SAR images and/or formation of
phony images of nonexistent targets. As a consequence, development of the electronic counter-countermeasures (ECCM)
capability becomes one of the key problems in SAR system design. This paper develops radar signaling strategies and
algorithms that enhance the ability of synthetic aperture radar to image targets under conditions of electronic jamming.
The concept of SAR using chaotic carrier frequency agility pulses (CCFAP-SAR) is first proposed. Then the imaging
procedure for CCFAP-SAR is discussed in detail. The ECCM performance of CCFAP-SAR for both depressive noise
jamming and deceptive repeat jamming is analyzed. The impact of the carrier frequency agility range on the image
quality of CCFAP-SAR is also studied. Simulation results demonstrate that, with adequate agility range of the carrier
frequency, the proposed CCFAP-SAR performs as well as conventional radar with linear frequency modulation (LFM)
waveform in image quality and slightly better in anti-noise depressive jamming; while performs very well in anti-deception
jamming which cannot be rejected by LFM-SAR.
Target discrimination technique utilizing noise waveforms
Author(s):
Gordon Woodington;
Mark DeLuca;
Richard Moro;
Daniel Lemus;
Russell Vela;
Ram Narayanan
Show Abstract
Noise waveforms generated using low cost diodes are a simple way for radars to transmit a wideband (> 4 GHz) multi-bit
pseudorandom code for use in a cross correlation receiver. This type of waveform also has the advantage of being
difficult to intercept and is less prone to interfere with adjacent systems. Radar designed to operate over this wide
frequency range can take advantage of unique target Radar Cross Section (RCS) ripple versus frequency for objects of
different materials and sizes. Specifically the periodicity and amplitude of the ripple is dependent on the shape and size
of a target. Since background clutter does not display this variation, RCS variation determines whether a known target is
present in a return. This paper will present the radar hardware and signal processing techniques used to maximize a
target's unique spectral response against a cluttered background. The system operates CW over a 4-8 GHz bandwidth
requiring the need to address issues regarding range resolution and far out undesired returns. Lessons learned from field
observations and mitigation techniques incorporated in the system are included. This paper also deals with the signal
processing technique used for detection, then discrimination. Detection thresholds are set and triggered by a simple
correlation peak level. Discrimination involves inspection of the spectral return. A comparison performed in real time to
a stored library value determines the presence of known objects. Measured data provided demonstrates the ability of the
radar to discriminate multiple targets against multiple backgrounds.
Design and implementation of random noise radar with spectral-domain correlation for moving target detection
Author(s):
Jeong Phill Kim;
Chi Hyun Jeong;
Cheol Hoo Kim
Show Abstract
A correlation processing algorithm in the spectral domain is proposed for detecting moving targets with random
noise radar. AD converted reference and Rx signals are passed through FFT block, and they are multiplied after
the reference signal is complex conjugated. Now inverse FFT yields the sub-correlation results, and range and
velocity information can be accurately extracted by an additional FFT processing. In this design procedure,
specific considerations have to be made for correlation length, averaging number, and number of sub-correlation
data for Doppler processing. The proposed algorithm was verified by Simulink (Mathworks) simulation, and its
logic was implemented with Xilinx FPGA device (Vertex5 series) by System Generator block sets (Xilinx) in the
Simulink environment. A CW X-band random-FM noise radar prototype with an instantaneous bandwidth of
100 MHz was designed and implemented, and laboratory and field tests were conducted to detect moving targets,
and the observed results showed the validity of the proposed algorithm and the operation of implemented FPGA
logics.
Passive radar imaging of moving targets using distributed apertures
Author(s):
Ling Wang;
Birsen Yazici
Show Abstract
We present a novel passive radar imaging method for moving targets using distributed apertures. We develop a
passive measurement model that relates measurements at a given receiver to measurements at other receivers.
We formulate the passive imaging problem as a Generalized likelihood ratio test (GLRT) for a hypothetical
target located at an unknown position, moving with an unknown velocity. We design a linear discriminant
functional by maximizing the signal-to-noise ratio (SNR) of the test-statistic, and use the resulting position- and
velocity-resolved test-statistic to form an image of the scene of interest. We present numerical experiments to
demonstrate the performance of our imaging method.
Concept for low-cost chaos radar using coherent reception
Author(s):
Jonathan N. Blakely;
Ned J. Corron
Show Abstract
We describe a new approach to random-signal radar based on the recent discovery of analytically solvable chaotic
oscillators. These surprising nonlinear systems generate random, aperiodic waveforms that offer an exact analytic
representation, allowing the implementation of simple matched filters and coherent reception. Notably, this approach
enables nearly optimal detection of noise-like waveforms without need for expensive variable delay lines to store
wideband waveforms for correlation. Mathematically, the waveform is expressed as a linear convolution of a bit
sequence with a fixed basis function. We realize a simple matched filter for the waveform using a linear filter whose
impulse response function is the time reverse of the basis function. Importantly, linear filters matched to finite bit
sequences can be defined, enabling pulse compression and spread spectrum radar. We present an example oscillator, its
matched filter, and simulation results demonstrating the pulse compression radar concept.
Nonlinear dynamics method for target identification
Author(s):
Thomas L. Carroll;
Frederic J. Rachford
Show Abstract
One may describe the effect of a radar or sonar target on an incoming signal as a filter which produces a
scattered signal. Chaotic signals are very sensitive to the effect of filters, so a radar or sonar target imposes
a unique signature on a scattered chaotic signal. In this paper we describe a method that uses the concept of
phase space dimension to create a reference from a scattered chaotic signal. This reference becomes part of a
library, and comparing an unknown scattered signal to this library can reveal which target caused a particular
scattered signal. Because we are not imaging the target, this method can use signal with low range resolution.
ECCM performance analysis of chaotic coded orthogonal frequency division multiplexing (COFDM) SAR
Author(s):
Xiangzhi Feng;
Xiaojian Xu
Show Abstract
Conventional linear frequency modulation (LFM) synthetic aperture radar (SAR) is incapable of countering deceptive
repeat jamming. In this paper, a new SAR signal based on chaotic coded orthogonal frequency division multiplexing
(COFDM) is studied. The fact that chaotic codes are sensitive to the initial values allows generating a large number of
different chaotic sequences to form SAR transmitting waveforms, where all the signal sequences are orthogonal to each
other, enabling COFDM-SAR countering not only active noise but also deceptive repeat jamming. The procedures for
COFDM waveform generation and SAR anti-jamming processing are discussed. Comparative studies of the electronic
counter-countermeasure performance (ECCM) between COFDM-SAR and conventional LFM-SAR are made.
Simulation results are presented to demonstrate the superior performance of COFDM-SAR in countering repeat
deception as well as active noise jamming.
Noise radar with broadband microwave ring correlator
Author(s):
Waldemar Susek;
Bronislaw Stec
Show Abstract
A principle of quadrature correlation detection of noise signals using an analog broadband microwave correlator is
presented in the paper. Measurement results for the correlation function of noise signals are shown and application of
such solution in the noise radar for precise determination of distance changes and velocity of these changes is also
presented. Results for short range noise radar operation are presented both for static and moving objects. Experimental
results using 2,6 - 3,6 GHz noise like waveform for the signal from a breathing human is presented. Conclusions and
future plans for applications of presented detection technique in broadband noise radars bring the paper to an end.
Interference suppression in noise radar systems
Author(s):
Slobodan Djukanović;
Miloš Daković;
Thayananthan Thayaparan;
Ljubiša Stanković
Show Abstract
This paper addresses the issue of interference
suppression in noise radars. The proposed methods can
be divided into non-parametric and parametric ones. The
considered non-parametric methods are based on linear
time-frequency (TF) tools, namely the short-time Fourier
transform (STFT) and local polynomial Fourier transform
(LPFT). The STFT is the simplest TF method, but, due to
the resolution problem, it performs poorly with highly nonstationary
interferences. The LPFT resolves the resolution
problem, however at the cost of increased complexity. In
parametric methods, the phase of interference is locally
approximated by a polynomial, which is motivated by the
Weierstrass's theorem. Using the phase approximation, the
corrupted received signal is demodulated and successively
filtered. Two methods for polynomial phase approximation
are considered, the high-order ambiguity function (HAF)
and product high-order ambiguity function (PHAF). The
method based on the HAF is computationally efficient;
however, it suffers from the identifiability problem when
multicomponent signals are considered. The identifiability
problem can be resolved using the PHAF.
Detection and identification of concealed weapons using matrix pencil
Author(s):
Raviraj S. Adve;
Thayananthan Thayaparan
Show Abstract
The detection and identification of concealed weapons is an extremely hard problem due to the weak signature
of the target buried within the much stronger signal from the human body. This paper furthers the automatic
detection and identification of concealed weapons by proposing the use of an effective approach to obtain
the resonant frequencies in a measurement. The technique, based on Matrix Pencil, a scheme for model
based parameter estimation also provides amplitude information, hence providing a level of confidence in
the results. Of specific interest is the fact that Matrix Pencil is based on a singular value decomposition,
making the scheme robust against noise.
Through-the-wall detection of human activity
Author(s):
Tommy Johansson;
Jonas Rahm;
Jan Gustavsson;
Stefan Nilsson;
Ain Sume;
Anders Örbom
Show Abstract
An approach toward real-time for radar through-the-wall (TTW) sensing is presented. The aim is to detect and classify
human motions behind walls. In the future a system could support an operator with information on the activity in a
closed room, e.g., in a hostage situation.
To meet this objective, radar TTW measurements have been performed on moving person(s) inside a closed room and an
MTI-based signal processing algorithm, using coherent subtraction between different frequency sweeps, has been
developed.
The radar was equipped with ridge horn antennas which were directed toward an outer door. For each measurement the
radar frequency was swept between 5 and 10 GHz 1893 times, with a sweep sampling rate of ~94 Hz.
A crucial algorithm parameter is the time distance between two subtracting sweeps, or the sweep difference. Fast and
slow motions are captured by using separate sweep differences.
Applying the algorithm to the TTW data, we find that human motions behind a door can be detected with the background
well suppressed. Even a person who is standing still without breathing is fairly easy to detect. The results are promising
with low false alarm rates and fast signal processing rates, enabling real-time operation capability.
Some comments on GMTI false alarm rate
Author(s):
A. W. Doerry
Show Abstract
A typical Ground Moving Target Indicator (GMTI) radar specification includes the parameters Probability of Detection
(PD) - typically on the order of 0.85, and False Alarm Rate (FAR) - typically on the order of 0.1 Hz. The PD is
normally associated with a particular target 'size', such as Radar Cross Section (RCS) with perhaps some statistical
description (e.g. Swerling number). However, the concept of FAR is embodied at a fundamental level in the detection
process, which traditionally employs a Constant-FAR (CFAR) detector to set thresholds for initial decisions on whether
a target is present or not. While useful, such a metric for radar specification and system comparison is not without some
serious shortcomings. In particular, when comparing FAR across various radar systems, some degree of normalization
needs to occur to account for perhaps swath width and scan rates. This in turn suggests some useful testing strategies.
Optimal antenna beamwidth for stripmap SAR
Author(s):
A. W. Doerry
Show Abstract
The classical rule-of-thumb for Synthetic Aperture Radar (SAR) is that a uniformly illuminated antenna aperture may
allow continuous stripmap imaging to a resolution of half its azimuth dimension. This is applied to classical line-by-line
processing as well as mosaicked image patches, that is, a stripmap formed from mosaicked spotlight images; often the
more efficient technique often used in real-time systems. However, as with all rules-of-thumb, a close inspection
reveals some flaws. In particular, with mosaicked patches there is significant Signal to Noise ratio (SNR) degradation at
the edges of the patches due to antenna beam roll-off. We present in this paper a calculation for the optimum antenna
beamwidth as a function of resolution that maximizes SNR at patch edges. This leads to a wider desired beamwidth
than the classical calculation.
Synthetic aperture radar for disaster monitoring
Author(s):
R. Dunkel;
R. Saddler;
A. W. Doerry
Show Abstract
Synthetic Aperture Radar (SAR) is well known to afford imaging in darkness and through clouds, smoke, and other
obscurants. As such, it is particularly useful for mapping and monitoring a variety of natural and man-made disasters.
A portfolio of SAR image examples has been collected using General Atomics Aeronautical Systems, Inc.'s (GA-ASI's)
Lynx® family of Ku-Band SAR systems, flown on both operational and test-bed aircraft. Images are provided that
include scenes of flooding, ice jams in North Dakota, agricultural field fires in southern California, and ocean oil slicks
from seeps off the coast of southern California.
Design and implementation of a digital impulse generator for a 24GHz UWB radar
Author(s):
Sang-Dong Kim;
Jong-Hun Lee
Show Abstract
In this paper, we design and implement a digital impulse generator using a DCM block and an OSERDES block for a
24GHz UWB impulse-Doppler radar. The Federal Communications Commission (FCC) has confirmed the spectrum
from 22 to 29GHz for UWB radar with a limit power of -41.3dBm/MHz. UWB signal possesses an absolute bandwidth
larger than 500MHz or a relative bandwidth up to 20%. The vehicle radar is the key technology with the inherent
advantage detected the distance and the velocity regardless of weather. Radar has a role to measure the distance and the
velocity of long-distance vehicle. But, the radar with 1m resolution is difficult to satisfy the detection performance in the
blind spot zone because the blind spot zone needs high resolution. So, UWB impulse-Doppler radar with 30cm
resolution is suitable for the blind spot zone. The designed impulse generator has a 2ns pulse width and 100us PRI. We
perform simulations through Xilinx ISE; experiments use a spectrum analyzer and a digital oscilloscope. For UWB
radar, we use an AD9779 DAC module with a 1Gsps maximum sampling rate. For equipment, we use a TDS5104B
oscilloscope of Tektronix with 3dB bandwidth at 1GHz for the analysis of the time domain and an E4448A spectrum
analyzer of Agilent with a 50GHz spectrum for the analysis of the frequency domain. The results of the digital impulse
measurement show a 2ns pulse width in the time domain, a 500MHz bandwidth, and a 10KHz spectrum peak in the
frequency domain.
DC-offset effect cancelation method using mean-padding FFT for automotive UWB radar sensor
Author(s):
Yeonghwan Ju;
Sang-Dong Kim;
Jong-Hun Lee
Show Abstract
To improve road safety and realize intelligent transportation, Ultra-Wideband (UWB) radars sensor in the 24 GHz
domain are currently under development for many automotive applications. Automotive UWB radar sensor must be
small, require low power and inexpensive. By employing a direct conversion receiver, automotive UWB radar sensor is
able to meet size and cost reduction requirements. We developed Automotive UWB radar sensor for automotive
applications. The developed receiver of the automotive radar sensor is direct conversion architecture. Direct conversion
architecture poses a dc-offset problem. In automotive UWB radar, Doppler frequency is used to extract velocity. The
Doppler frequency of a vehicle can be detected using zero-padding Fast Fourier Transform (FFT). However, a zero-padding
FFT error is occurs due to DC-offset problem in automotive UWB radar sensor using a direct conversion
receiver. Therefore, dc-offset problem corrupts velocity ambiguity. In this paper we proposed a mean-padding method to
reduce zero-padding FFT error due to DC-offset in automotive UWB radar using direct conversion receiver, and verify
our proposed method with computer simulation and experiment using developed automotive UWB radar sensor. We
present the simulation results and experiment result to compare velocity measurement probability of the zero-padding
FFT and the mean-padding FFT. The proposed algorithm simulated using Matlab and experimented using designed the
automotive UWB radar sensor in a real road environment. The proposed method improved velocity measurement
probability.
Integrated radar-camera security system: experimental results
Author(s):
M. Zyczkowski;
N. Palka;
T. Trzcinski;
R. Dulski;
M. Kastek;
P. Trzaskawka
Show Abstract
The nature of the recent military conflicts and terrorist attacks along with the necessity to protect bases, convoys and
patrols have made a serious impact on the development of more effective security systems. Current widely-used
perimeter protection systems with zone sensors will soon be replaced with multi-sensor systems. Multi-sensor systems
can utilize day/night cameras, IR uncooled thermal cameras, and millimeter-wave radars which detect radiation reflected
from targets. Ranges of detection, recognition and identification for all targets depend on the parameters of the sensors
used and of the observed scene itself. In this paper two essential issues connected with multispectral systems are
described. We will focus on describing the autonomous method of the system regarding object detection, tracking,
identification, localization and alarm notifications. We will also present the possibility of configuring the system as a
stationary, mobile or portable device as in our experimental results.
Resolution analysis of bistatic SAR
Author(s):
Guillermo Garza;
Zhijun Qiao
Show Abstract
In this paper, we analyze the resolution of bistatic synthetic aperture radar (BISAR) imaging for stationary objects.
In particular, we analyze the resolution of images reconstructed by the method of a filtered backprojection
inversion, an inversion method which is derived from a scalar wave equation model. In this context we are able
to account for the effects of antenna beam patterns and arbitrary flight trajectories. The analysis is done by
examining the data collection manifold for different experiment geometries and system parameters.
Side-looking image formation with a maneuvering vehicle-mounted antenna array
Author(s):
Kenneth Ranney;
Lam Nguyen;
Francois Koenig;
Getachew Kirose;
Anthony Martone;
Gregory Mazzaro;
Kelly Sherbondy;
Chi Tran;
Karl Kappra
Show Abstract
Researchers at the U.S. Army Research Laboratory (ARL) designed and fabricated the Synchronous Impulse
REconstruction (SIRE) radar system in an effort to address fundamental questions about the utilization of low
frequency, ultrawideband (UWB) radar. The SIRE system includes a receive array comprising 16 receive channels,
and it is capable of operating in either a forward-looking or a side-looking mode. When operated in side-looking
mode, it is capable of producing high-resolution Synthetic Aperture Radar (SAR) data. The SAR imaging
algorithms, however, initially operated under the assumption that the vehicle followed a nearly linear trajectory
throughout the data collection. Under this assumption, the introduction of vehicle path nonlinearities distorted the
processed SAR imagery. In an effort to mitigate these effects, we first incorporated segmentation routines to
eliminate highly non-linear portions of the path. We then enhanced the image formation algorithm, enabling it to
process data collected from a non-linear vehicle trajectory.
We describe the incorporated segmentation approaches and compare the imagery created before and after their
incorporation. Next, we describe the modified image formation algorithm and present examples of output imagery
produced by it. Finally, we compare imagery produced by the initial segmentation algorithm to imagery produced by
the modified image-formation algorithm, highlighting the effects of segmentation parameter variation on the final
SAR image.
Wideband fiber optic vector modulator using 8-tap all-optical Hilbert transformer
Author(s):
Ryand Tucker;
Sergio C. Granieri;
Azad Siahmakoun
Show Abstract
A wideband photonic RF vector modulator with novel architecture is presented and demonstrated with capability of
continuous amplitude modulation and 0°-360° phase shifting. In-phase and quadrature-phase components of the output
signal are used to produce 360° continuous phase shifting and optical attenuation is used to control the signal amplitude.
A novel 8-tap all-optical transverse-filter implementing a Hilbert transform is proposed and demonstrated to produce 90° quadrature phase-shift for the broadband RF signal. Experimental apparatus and results for continuous vector modulation
will be presented for the frequency range of 1-6 GHz.
Stereo matching: performance study of two global algorithms
Author(s):
Sarala Arunagiri;
Victor J. Jordan;
Patricia J. Teller;
Joseph C. Deroba;
Dale R. Shires;
Song J. Park;
Lam H. Nguyen
Show Abstract
Techniques such as clinometry, stereoscopy, interferometry, and polarimetry are used for Digital Elevation Model
(DEM) generation from Synthetic Aperture Radar (SAR) images. The choice of technique depends on the SAR
configuration, the means used for image acquisition, and the relief type. The most popular techniques are interferometry
for regions of high coherence and stereoscopy for regions such as steep forested mountain slopes. Stereo matching,
which is finds the disparity map or correspondence points between two images acquired from different sensor positions,
is a core process in stereoscopy. Additionally, automatic stereo processing, which involves stereo matching, is an
important process in other applications including vision-based obstacle avoidance for unmanned air vehicles (UAVs),
extraction of weak targets in clutter, and automatic target detection. Due to its high computational complexity, stereo
matching has traditionally been, and continues to be, one of the most heavily investigated topics in computer vision. A
stereo matching algorithm performs a subset of the following four steps: cost computation, cost (support) aggregation,
disparity computation/optimization, and disparity refinement. Based on the method used for cost computation, the
algorithms are classified into feature-, phase-, and area-based algorithms; and they are classified as local or global based
on how they perform disparity computation/optimization. We present a comparative performance study of two pairs, i.e.,
four versions, of global stereo matching codes. Each pair uses a different minimization technique: a simulated annealing
or graph cut algorithm. And, the codes of a pair differ in terms of the employed global cost function: absolute difference
(AD) or a variation of normalized cross correlation (NCC). The performance comparison is in terms of execution time,
the global minimum cost achieved, power and energy consumption, and the quality of generated output. The results of
this preliminary study provide insights into the suitability and relative merits of these algorithms and cost functions for
execution on field-deployable and on-board computer systems with size, weight, and power (SWaP) constraints. The
results show that for 12 out of 14 instances the graph cut codes, compared to their simulated annealing counterparts
provided a 35-85% improvement in energy consumption and, therefore, are promising candidates for use in field-deployable
and on-board systems.
On the use of the Shark antenna for radar detection techniques
Author(s):
L. Desrumaux;
M. Lalande;
J. Andrieu;
V. Bertrand;
B. Jecko
Show Abstract
This paper proposes two studies on a Shark antenna array, working in the frequency band [800MHz - 8GHz],
in a configuration including N generators and N antennas. The first study deals with the evaluation of the
performances of the array from the analyze of the transient performances of the elementary system "generator +
antenna". The second study concerns the comparison of two arrays having the same surface area, but a different
number of antennas thanks to a scaling method on the dimensions of the elementary antenna.
Attenuation of front-end reflections in an impulse radar using high-speed switching
Author(s):
Gregory J. Mazzaro;
Marc A. Ressler;
Gregory D. Smith
Show Abstract
Pulse reflection between front-end components is a common problem for impulse radar systems. Such reflections arise
because radio frequency components are rarely impedance-matched over an ultra-wide bandwidth. Any mismatch
between components causes a portion of the impulse to reflect within the radar front-end. If the reflection couples into
the transmit antenna, the radar emits an unintended, delayed and distorted replica of the intended radar transmission.
These undesired transmissions reflect from the radar environment, produce echoes in the radar image, and generate false
alarms in the vicinity of actual targets.
The proposed solution for eliminating these echoes, without redesigning the transmit antenna, is to dissipate pulse
reflections in a matched load before they are emitted. A high-speed switch directs the desired pulse to the antenna and
redirects the undesired reflection from the antenna to a matched load.
The Synchronous Impulse Reconstruction (SIRE) radar developed by the Army Research Laboratory (ARL) is the
case-study. This paper reviews the current front-end design, provides a recent radar image which displays the
aforementioned echoes, and describes the switch-cable-load circuit solution for eliminating the echoes. The
consequences of inserting each portion of the new hardware into the radar front-end are explained. Measurements on the
front-end with the high-speed switch show an attenuation of the undesired pulse transmissions of more than 18 dB and
an attenuation in the desired pulse transmission of less than 3 dB.
Exploiting spatial diversity in MIMO radars with collocated antennas
Author(s):
Ghassan Maalouli;
Daniel Rosser;
Glafkos Stratis
Show Abstract
MIMO systems have revolutionized wireless communications resulting in unprecedented channel capacity. This
breakthrough led researchers in radar as well as wireless communications communities to investigate the applicability of
MIMO systems to radar. Preliminary research is showing that the full benefits of MIMO technology is realized when
antenna spacing results in a decorrelated target scattering matrix. This requires antenna placement such that each
receiver is observing an independent view of the target. Research is also showing that suboptimal improvements can be
attained when the scattering matrix is partially correlated. This situation arises when antennas are collocated. In this
work, we investigate the feasibility of MIMO Radar technology when antenna placement is quite restricted, such as in
phased-array antennas. We extend the theoretical results for the correlation coefficients derived for statistical MIMO
radar. We apply these results to assess the degree of decorrelation that can be achieved with Phase-Array antennas. We
quantify our results as a function of antenna element spacing, frequency band and target RCS. In addition, we quantify
the degree of decorrelation that is achievable by antennas that are typical in a tactical missile environment. Our results
show that even when the antennas are quite small, it is possible to achieve a significant degree of decorrelation for a
certain class of targets and certain frequency bands.
Sidelobe minimization in MTI processing
Author(s):
Kenneth Ranney;
Anthony Martone;
Roberto Innocenti;
Lam Nguyen
Show Abstract
Moving target indication (MTI) algorithms often operate within a relatively narrow frequency band
relying on Doppler processing to detect moving targets at long standoff ranges. At these standoff ranges,
received wavefronts impinging on a linear array can be considered planar, enabling implementation of a
variety of phase-based beam-forming techniques. At near ranges, however, the plane-wave assumption no
longer holds. We describe enhancements to an impulse-based, low-frequency, ultra-wideband, moving-target
imaging system for near-range, through-the-wall MTI. All MTI image processing is performed in
the time domain using a change detection (CD) paradigm. We discuss how MTI image quality can be
increased through the introduction of randomized linear arrays. After describing the process in detail, we
present results obtained using data collected by an impulse-based, low frequency, ultra-wideband system.