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A Compressed Sensing/Sparse Recovery approach is adopted in this paper for the accurate diagnosis of fault array elements from undersampled data. Experimental validations on a slotted waveguide test array are discussed to demonstrate the effectiveness of the proposed procedure in the failures retrieval from a small set of measurements with respect to the number of radiating elements. Due to the sparsity feature of the proposed formulation, the method is particularly appealing for the diagnostics of large arrays, typically adopted for radar applications. [ABSTRACT FROM AUTHOR]

Polarimetric weather radars significantly enhance the capability to infer the properties of scatterers within a resolution volume. Previous studies have identified several consistently seen polarimetric signatures in supercells observed in the central United States. Nearly all of these studies used data collected by fixed-site S- and C-band radars. Because there are few polarimetric mobile radars, relatively little has been documented in high-resolution polarimetric data from mobile radars. Compared to S and C bands, there has been very limited examination of polarimetric signatures at X band. The primary focus of this paper is on one signature that has not been documented previously and one that has had little documentation at X band. The first signature, seen in at least seven supercell datasets collected by a mobile, X-band, polarimetric radar, consists of a narrow band of locally reduced reflectivity factor ZH and differential reflectivity, typically near the location where the hook echo 'attaches' to the main body of the storm echo. No consistent pattern is seen in radial velocity VR or copolar cross correlation ρHV. The small size of this feature suggests a significant heterogeneity in precipitation microphysics, the cause and impact of which are unknown. The greater resolution and the scattering differences at X band compared to other frequencies may make this feature more apparent. The second signature consists of anomalously low ρHV in areas of high ZH along the left section (relative to storm motion) of the bounded weak-echo region. Examples of other polarimetric signatures at X band are provided. [ABSTRACT FROM AUTHOR]

Range sidelobes, a major shortcoming of radar pulse compression, are often reduced through the use of mismatched filters. The authors propose to blank the remaining sidelobes by using two or more mismatched filters, whose sidelobes are designed to peak at different delays. The authors show how to design such filters and present promising simulation results with two or more mismatched filters. [ABSTRACT FROM AUTHOR]

A multiple-input multiple-output (MIMO) configuration has been studied for communication applications, offering a lot of advantages to mitigate propagation effects because of multipath and fading environments. More recently, MIMO techniques in radar have been proposed. MIMO is discussed in the context of high-frequency surface waves radar (HFSWR). After a short introduction to the MIMO radar technique (a technique which is not new; the RIAS developed by ONERA was probably the first MIMO radar), explores two different applications are explored. The first application aims at improving the resolution and accuracy of a coastal radar, proposed here in a bistatic configuration. Such a radar operates with a wide sparse frequency band and with an equivalent wide aperture, taking advantage of the MIMO configuration. Simulation over a congested area of targets demonstrates the benefit of MIMO over the conventional HFSWR radar, especially in terms of separation of targets. The second application consists in a more practical ship-borne HFWSR configuration compatible with space time adaptive processing (STAP) to improve the detection of slow targets. In this case, a limited number of receiving channels is considered whereas STAP uses the degrees of freedom offered by the transmitting array. The MIMO-STAP is compared with a conventional STAP, showing that theoretical performances should not be affected by the MIMO configuration even if the signals are no longer perfectly orthogonal, because of Doppler shift, once scattered by moving targets. [ABSTRACT FROM AUTHOR]

In this paper, a support vector machine (SVM) classifier was designed to identify tornado vortices based on their characteristics that were determined from the Doppler spectra and eigenvalues that were calculated from the data that were collected in the vicinity of these vortices. To collect these data, weather surveillance radar (WSR-88D) was employed, which is locally operated by the National Severe Storms Laboratory (NSSL) on the north campus of the University of Oklahoma, Norman. This particular radar, which is devoted to experimental research rather than operational weather forecasting, has the unique capability of recording massive volumes of in-phase (I) and quadrature (Q) data over many hours. As such, the received radar echo power and Doppler shift information can be determined from these I and Q complex-valued data, which provides a rich environment for evaluating our new postprocessing algorithms. At the current time, most radar systems, including North America's national network of weather radar systems, process these I and Q data in real time to produce environmental measurements known as "spectral moments," which are the first three statistical moments of the data. These three moments (the reflectivity, the radial velocity, and the spectrum width) are then provided to scientists or forecasters, and the abundance of I and Q data is not preserved to save computer resources. One of the aims of this paper is to show how additional information about the atmosphere can be garnered from the land Q data. To assist this mission, an SVM-based classifier evades the pitfalls of the traditional statistical learning algorithms, such as neural networks, by setting up a convex optimization problem with a single global minimum. In addition, through the use of kernels and a nonlinear mapping to higher dimensional spaces, the SVM classifier is able to effectively handle nonlinear classification problems. The idea behind this transformation is to facilitate the separability of classes by taking the input vectors to a higher dimensional space. The SVM classifier has the added advantage of reducing overfitting by constructing a maximum margin to separate hyperplanes in a higher dimensional feature space to ensure a small generalization error bound. Finally, our practical results are in positive agreement with our theoretical predictions. [ABSTRACT FROM AUTHOR]

The validation of the floating potential measurement unit (FPMU) plasma density and temperature measurements is an important step in the process of evaluating International Space Station (ISS) spacecraft charging issues including vehicle arcing and hazards to crew during extravehicular activities. The highest potentials observed on the Space Station are due to the combined Vsp x B effects on a large spacecraft and the collection of ionospheric electron and ion currents by the 160-V U.S. solar array modules. The ionospheric plasma environment is needed for input to the ISS spacecraft charging models used to predict the severity and frequency of occurrence of ISS charging hazards. The validation of these charging models requires the comparison of their predictions with measured FPMU values. The FPMU measurements themselves must also be validated for use in manned flight safety work. This paper presents preliminary results from a comparison of densities and temperatures derived from the FPMU Langmuir probes and plasma impedance probe with the independent density and temperature measurements from a spaceborne ultraviolet imager, a ground-based incoherent scatter radar, and ionosonde sites. [ABSTRACT FROM AUTHOR]

Two years of high temporal- and spatial-resolution radar data is used to quantify the rain-attenuation diversity gain available in 26 GHz fixed wireless access systems having sight of the second transmitter. The service area defined by attenuation contours on the least-faded link is determined; the results show that an expansion of the service area is possible even over short paths. Service area contours with and without diversity are derived from radar observations of rainfall rate. Good agreement is obtained with similar results for a statistical model based on a gamma probability distribution and a negative-exponential spatial correlation function for rain rate (which are shown to fit observed data). For the service area defined by a bit error rate of 10-4 and availability of 4 × 10-5, site diversity expands the service area by up to 20% with a 10 km access point spacing. [ABSTRACT FROM AUTHOR]

A method for scanning of the main beam of phased array antennas in a wide angular range is presented. The method utilizes several smaller flat antenna panels, arranged in an array of panels, each of the panels pointed in the direction of the main beam of overall antenna. The output signal of the overall antenna is summation of the signals from all antenna panels. Investigation of the array performance of such structure with respect to the distance between the panels and sidelobe level of the antenna structure is presented. [ABSTRACT FROM AUTHOR]

The objective of the study is to clarify some physical limitations in the performance of statistical RADAR systems using multiple antennas. In particular, it is shown that the performance of the recently proposed statistical multiple-input multiple-output (MIMO) RADAR is limited by the Number of Degrees of Freedom (NDF) of the scattered field. Furthermore, the true nature of statistical RADAR systems (single-input multiple-output, multiple-input single-output, MIMO) is not related to the number of transmitting/receiving antennas, but to the NDF of the scattered field exploited by the system. [ABSTRACT FROM AUTHOR]

A modified piecewise linear current density recursive convolution (PLCDRC) finite-difference time-domain (FDTD) for anisotropic magnetised plasma is proposed. The method is derived using two recursive conclusion. The electric field is time-shifted in the first convolution and the current density is time-shifted in the second convolution. The computation of the current density and the electric field employ the piecewise linear approximation technique. Like PLCDRC FDTD, the method has more accuracy over CDRC FDTD. Moreover, it is faster in computation velocity than PLCDRC FDTD. The high efficiency and accuracy of the method are confirmed by computing the reflection and transmission through a magnetised plasma layer, with the direction of propagation parallel to the direction of the biasing field. The bistatic radar cross-section of conducting sphere covered with magnetised plasma is also calculated. Then, the numerical dispersion relation of the new PLCDRC FDTD scheme is derived. The numerical dispersion error and dissipation error caused by the new PLCDRC-FDTD method are investigated by comparing the real and imaginary parts of the numerical wave number with those of the analytical wave number. Finally, the stability of the new PLCDRC-FDTD method is discussed. This method can also be used in other frequency dispersion electromagnetic problem if it is modified slightly. [ABSTRACT FROM AUTHOR]

Large-scale full-wave simulations are performed to investigate radar wave propagation inside buildings. In principle, a radar system combined with sophisticated numerical methods for inverse problems can be used to determine the internal structure of a building. The composition of the walls (cinder block, rebar) may effect the propagation of the radar waves in a complicated manner. In order to provide a benchmark solution of radar propagation in buildings, including the effects of cinder block and rebar, we performed large-scale full-wave simulations using a finite-element time domain (FETD) method. This particular FETD implementation is tuned for the special case of an orthogonal Cartesian mesh and hence resembles finite-difference time domain (FDTD) in accuracy and efficiency. The method was implemented on a general-purpose massively parallel computer. In this paper we briefly describe the radar propagation problem, the FETD implementation, and we present results of simulations that used over 10-billion elements. [ABSTRACT FROM AUTHOR]

On 8 May 2003, a tornadic supercell tracked through portions of the Oklahoma City, Oklahoma, metropolitan area and produced violent damage along portions of its path. This storm passed through the dense in situ radar network in central Oklahoma and provided close-range operational, prototype polarimetric and terminal Doppler weather radar observations of the storm as it made the transition into the tornadic phase. The time-evolving polarimetric features were scrutinized with regard to storm morphology, particularly as related to the development of a rear-flank downdraft pulse within the storm immediately preceding the long-track tornado event. Two new polarimetric terms are introduced, the Zdr shield and Kdp foot, along with a discussion of the orientation of the Zdr and Kdp columns relative to midlevel rotation signatures. Storm downdraft and gust front characteristics are discussed relative to polarimetric fields and background environment characteristics. Highlighted for this event are a “warm” forward-flank downdraft and a particularly cold rear-flank downdraft. Emphasis is also placed on demonstrating key polarimetric field characteristics relative to traditional features at low and midlevels defined in familiar conceptual models of severe storms. [ABSTRACT FROM AUTHOR]

A three-dimensional radar simulator capable of generating simulated raw time series data for a weather radar has been designed and implemented. The characteristics of the radar signals (amplitude, phase) are derived from the atmospheric fields from a high-resolution numerical weather model, although actual measured fields could be used. A field of thousands of scatterers is populated within the field of view of the virtual radar. Reflectivity characteristics of the targets are determined from well-known parameterization schemes. Doppler characteristics are derived by forcing the discrete scatterers to move with the three-dimensional wind field. Conventional moment-generating radar simulators use atmospheric conditions and a set of weighting functions to produce theoretical moment maps, which allow for the study of radar characteristics and limitations given particular configurations. In contrast to these radar simulators, the algorithm presented here is capable of producing sample-to-sample time series data that are collected by a radar system of virtually any design. Thus, this new radar simulator allows for the test and analysis of advanced topics, such as phased array antennas, clutter mitigation schemes, waveform design studies, and spectral-based methods. Limited examples exemplifying the usefulness and flexibility of the simulator will be provided. [ABSTRACT FROM AUTHOR]

The Precipitation Occurrence Sensor System (POSS) is a small X-band Doppler radar originally developed by the Meteorological Service of Canada for reporting the occurrence, type, and intensity of precipitation from Automated Weather Observing Stations. This study evaluates POSS as a gauge for measuring amounts of both liquid and solid precipitation. Different precipitation rate estimation algorithms are described. The effect of different solid precipitation types on the Doppler velocity spectrum is discussed. Lacking any accepted reference for high temporal resolution rates, the POSS precipitation rate measurements are integrated over time periods ranging from 6 h to one day and validated against international and Canadian reference gauges. Data from a wide range of sites across Canada and for periods of several years are used. The statistical performance of POSS is described in terms of the distribution of ratios of POSS to reference gauge amounts (catch ratios). In liquid precipitation the median of the catch ratio distribution is 82% and the interquartile range was between -12% and 19% about the median. In solid precipitation the median is 90% and the interquartile range is between -17% and 24% about the median. The underestimation in both liquid and solid precipitation is shown to be a function of precipitation rate and phase. The effects of radome wetting, raindrop splashing, wind, and the radar “brightband” effect on the estimation of precipitation rates are discussed. [ABSTRACT FROM AUTHOR]

The maximum cross-correlation (MCC) technique is utilized to estimate the Adriatic Sea surface currents in regions characterized by strong horizontal temperature gradients using sequential pairs of sea surface temperature images from the Advanced Very High Resolution Radiometer data collected between September 2002 and December 2003. A variety of filtering techniques are used to eliminate erroneous MCC-derived currents resulting in velocity and direction estimates that are spatially coherent in most of the thermal features observed. The results are compared quantitatively to the currents measured by surface drifters and high-frequency coastal radars, operating simultaneously in the vicinity of the thermal structures considered. These comparisons show that surface MCC-derived velocities agree with the typical circulation pattern generally observed in the Adriatic basin. The MCC velocity estimates agree well with collocated and cotemporal drifter and radar measurements averaged on the time interval separating the pairs of images. Since the MCC method provides only estimates of surface currents when thermal features exist and are not covered by clouds, it is proposed that this technique be used preferably with other measurements of surface circulation (high-frequency coastal radars, drifters, etc.) to construct more accurate, more frequent, and more extended circulation maps for scientific and operational purposes in marginal seas such as the Adriatic. [ABSTRACT FROM AUTHOR]

In this paper, we present an analytic, filtered backprojection (FBP) type inversion method for bistatic synthetic aperture radar (BISAR). We consider a BISAR system where a scene of interest is illuminated by electromagnetic waves that are transmitted, at known times, from positions along an arbitrary, but known, flight trajectory and the scattered waves are measured from positions along a different flight trajectory which is also arbitrary, but known. We assume a single-scattering model for the radar data, and we assume that the ground topography is known but not necessarily flat. We use microlocal analysis to develop the FBP-type reconstruction method. We analyze the computational complexity of the numerical implementation of the method and present numerical simulations to demonstrate its performance. [ABSTRACT FROM AUTHOR]

The variability of the drop size distribution (DSD) is one of the factors that must be considered in understanding the uncertainties in the retrieval of oceanic precipitation from passive microwave observations. Here, we have used observations from the Precipitation Radar on the Tropical Rainfall Measuring Mission spacecraft to infer the relationship between the DSD and the rain rate and the variability in this relationship. The impact on passive microwave rain rate retrievals varies with frequency and rain rate. The total uncertainty for a given pixel can be slightly larger than 10% at the low end (ca. 10 GHz) of frequencies commonly used for this purpose and smaller at higher frequencies (up to 37 GHz). Since the error is not totally random, averaging many pixels, as in a monthly rainfall total, should roughly halve this uncertainty. The uncertainty may be lower at rain rates less than about 30 mm/h, but the lack of sensitivity of the surface reference technique to low rain rates makes it impossible to tell from the present data set. [ABSTRACT FROM AUTHOR]

The well-known Rayleigh parameter, which characterizes the degree of roughness of a corrugated surface for the case of reflection on a rough surface, is extended to the reflection on a rough layer. An application to the forward radar propagation over oil slicks on sea surfaces, using the Ament model, is given. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2285–2290, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22716 [ABSTRACT FROM AUTHOR]

The design of a rectangular waveguide 95 GHz (W-band) triplexer for ground radar systems is presented. The triplexer comprises three in-line filters with inductive irises as coupling elements and a manifold formed by three T-junctions. In particular, the scheme proposed is aimed at handling large powers and reducing losses. The triplexer was assembled and measured, showing very good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

The noise-like chaotic signal can be generated with very simple nonlinear circuits, and has broad bandwidth and aperiodic properties. These characteristics have drawn considerable attention in the radar community. In the past, the chaotic signal or its modulated version serves as a transmitting signal, and the traditional correlation-type receiver is used for processing. In this sense, the chaotic signal acts as a radar waveform in the noise signal radar, and hence the performance advantages are not distinct. Here, we present a scheme for processing chaotic radar signals. We find a simple relation between the target parameters (range and velocity) and the system parameters of chaos-generating system. With this relation, the measurement of the target parameters is transformed into estimation of the system parameters from the radar return signals. Equipped with high resolution parameter estimation techniques, the proposed principles provide a way to develop high resolution noise signal radars. [ABSTRACT FROM AUTHOR]

In this paper, the effect of ship angular motions on the radar cross section is addressed. To this end, a set of measurements for different ships were conducted from a shore-based instrumental radar. The targets execute oblique straight trajectories with respect to the radar line of sight with induced roll. The analysis of the dependence between target reflectivity and the roll angle shows that, for conventional vessels, the maximum response at low grazing angles is achieved in steady conditions, and it varies significantly according to the sign of the roll angle referred to the radar location. This result is confirmed by the comparison of measurements of a ship performing turning circles at several speeds, thus inducing different roll angles. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2237–2241, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21932 [ABSTRACT FROM AUTHOR]

We present a (suboptimal) filtering algorithm for tracking a highly maneuvering target in a cluttered environment using multiple sensors. The filtering algorithm is developed by applying the basic interacting multiple model (IMM) approach and the probabilistic data association (FDA) technique to a two sensor (radar and infrared, for instance) problem for state estimation for the target. A simultaneous measurement update approach is followed where the raw sensor measurements are passed to a central processor and fed directly to the target tracker. A multisensor FDA filter is developed for parallel sensor processing for target tracking under clutter. A past approach using parallel sensor processing has ignored certain data association probabilities leading to an inaccurate implementation. Another existing approach applies only to nonmaneuvering targets. The algorithm is illustrated via a highly maneuvering target tracking simulation example where two sensors, a radar and an infrared sensor, are used. Compared with an existing IMMIPDA filtering algorithm with sequential sensor processing, the proposed algorithm achieves significant improvement in the accuracy of track estimation. [ABSTRACT FROM AUTHOR]

Sidelobe blanking (SLB) devices are used in connection with the radar system to reduce the number of false alarms due to impulsive interference. This paper presents analytical expressions for the probability of blanking a sidelobe jammer interference via an SLB device for two statistical models of interference amplitude, namely, the Swerling Chi and shadowed Rice models. Performance curves are presented and the role of the different jammer parameters thoroughly investigated. [ABSTRACT FROM AUTHOR]

A mode-expansion method that needs less than 6% the number of unknowns required by conventional method of moments is introduced in calculating two-dimensional electromagnetic wave scattering from perfectly conducting objects on rough ocean surfaces. Modes are selected for dominant propagation waves so that the number of unknowns in the matrix equation are minimized. In the numerical examples, ocean surfaces, are modeled as perfectly conducting rough surfaces described by the Pierson-Moskowitz power spectrum. Bistatic radar cross-sections (RCS) of various objects, such as ship-like and low-observable targets, are calculated for a 1-GHz incident plane wave and are validated for accuracy against an iterative MoM solution. [ABSTRACT FROM AUTHOR]

OSMAR2003 high frequency surface wave radar (HFSWR) system became operational in the autumn of 2003. Apart from providing surveillance of over 40000 square kilometres of the sea environment such as surface current and sea state, the radar facility has the potential of detecting and tracking ships in all weather. Susceptibility of HFSWR to external co-channel interference (CCI) may degrade performance significantly. In the paper, the characteristics of co-channel interference are described, and the authors present a comparative analysis of spatial domain and temporal domain interference mitigation algorithms for target detection. Experimental results confirm that adaptive spatial domain interference suppression using subarrays and temporal domain interference suppression based on classical Weiner prediction filters are both helpful techniques for target detection in a small-scale antenna array when the incident interference and the target signal have different incoming directions, but the spatial domain technique is likely to distort the angular response of the target signal simultaneously. Alternatively, when the incident interference and the backscattering target signal have the same incoming direction, the adaptive spatial domain algorithm will simultaneously degrade the target signal while providing effective interference mitigation, but the temporal domain technique can work well on target detection while maintaining distortionless output of the target signal. [ABSTRACT FROM AUTHOR]

Coherent sidelobe cancellation (CSLC) based on subarrays has emerged as a key technology for improving the performance of radar systems required to operate in the presence of severe interference which generally includes clutter as well as jamming. While the theory of CSLC is well known, practical issues such as how to set up the subarrays and how to avoid diminishing the desired signal when the clutter is rejected need to be addressed when it comes to implementing CSLC in operational radar systems. A new adaptive ionospheric clutter suppression algorithm based on subarrays for monostatic HF surface wave radar (HFSWR) is introduced and analysed. Detailed comparisons between the proposed algorithm and conventional CSLC are performed. Simulation and real data results confirm that the general and robust algorithm can achieve effective ionospheric clutter suppression, while not decreasing the strength of the first-order sea echo using the data recorded by the OSMAR2003 (Ocean State Monitor and Analysis Radar, manufactured in 2003), located near Zhoushan in Zhejiang, China. [ABSTRACT FROM AUTHOR]

A set of theoretical techniques to prevent a radar from being used by a bistatic radar receiver as a non-cooperative illuminator are analysed. This works by radiating in addition to the radar signal waveform, a `masking signal' waveform which is orthogonal to the radar signal waveform, both in the coding domain and the spatial domain. A number of different coding schemes are analysed. Two spatial coding methods are presented and analysed: the first uses a pair of interferometer elements at the extremities of the radar antenna array; the second uses a Butler matrix to generate a set of orthogonal beams. System-level calculations are presented to show the level of masking of the radar signal received by a bistatic radar receiver, and the suppression of the masking signal in the host radar echo. Some ideas for further work are presented. [ABSTRACT FROM AUTHOR]

The relative motion between radar and targets in large time-bandwidth product synthetic aperture radar (SAR) induces serious dilation in the received signal. To process the received signal with serious dilation, a new technique called dilation dependent matched filtering (DDMF) is proposed to combine with the two-dimensional space frequency interpolation wavefront reconstruction (SFIWR) method. The DDMF-SFIWR method can effectively eliminate the Impact of dilation when the illuminated area is relatively small, as verified by simulations and acoustic experiments. [ABSTRACT FROM AUTHOR]

An analysis of radar signals is provided with details appropriate in the design of short range long dwell time radar systems, e.g. missile warning radar. It considers nonuniform amplitude return details from target range translation during long dwell times and provides an expression for dwell time that optimizes signal-to-noise ratio (SNR). [ABSTRACT FROM AUTHOR]

Ground-based frequency-modulated continuous wave (FMCW) radar measurements made throughout the 200203 NASA Cold Lands Processes (CLPX) mission in Colorado, USA, were designed to study the major electromagnetic transitions within the alpine snowpack over a wide range of conditions, and their effect on measurements made with different active radar measurement parameters. Measurements during 2002 determined that measurements at C-, X-, and Ku-band frequencies were necessary to retrieve the most snowpack information in a wide range of conditions. Measurements at four different incidence angles indicated that the snowpack layering was still visible at 15 but that the rough surface scattering of the snowground interface dominated the signal above 30 incidence. Measurements during 2003 were focused on characterizing the microwave response at C-, X-, and Ku-band frequencies at four different sites with different snowpack conditions, indicating that the optimal measurement parameters vary with snowpack conditions. Measurements at different bandwidths illustrate the effect of bandwidth on vertical resolution. This ground-truth data will help interpretation of air- and space-borne active and passive microwave radar measurements that were made coincident with this study. In addition, this work may help guide future researchers when choosing FMCW radar measurement parameters, depending on the type of snowpack information their study requires. Copyright 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The paper presents results for spectral and textural analysis of the rock units in Landsat Thematic Mapper (TM) images, dual-band (L and C) and dual-polarization (HH and HV) Shuttle Imaging Radar (SIR)-C images, and C-band HH polarization Standard Beam 4 and Extended High Incidence Beam 3 Radarsat images from a study area between California and Arizona, USA. Fractal dimension, lacunarity and grey-level co-occurrence matrix (GLCM) textural feature images were created from the SIR-C and Radarsat images. Fractal dimensions were calculated using a differential box counting method and lacunarity measures were obtained using a new grey-scale lacunarity estimation method for 36 sample images extracted from the SIR-C and Radarsat images. The fractal dimension and lacunarity curves and class signature separability analysis show that, for rock unit discrimination using image textural features in the study area, the SIR-C L-HH image is more suitable than other SIR-C images and Radarsat images, and that co-polarization (HH) generally provides more textural information than cross-polarization (HV) in the study area. The study also shows that lacunarity measures can reveal the scaling properties of radar image textures for rock units. The combination of spectral information from Landsat TM images and textural information from radar images improves the image classification accuracy of rock units in the study area. [ABSTRACT FROM AUTHOR]

When MTI (Moving Target Indicators) and AMTI (Adaptive MTI) are used in the pulse radar for searching, the staggered trigger scheme that transmits pulses at nonequal intervals in order to reduce the blind speed region is often used. As a clutter suppression process when the staggered trigger scheme is used, a method using the time variable coefficient filter is commonly chosen. However, in this method, a higher-order time-varying filter is needed in order to suppress several different clutters received at the same time. As a result, the computational effort to derive the filter coefficients for the desired characteristics increases, making real-time processing difficult. As a solution to this problem, this paper proposes a method of realizing a clutter suppression filter by means of a cascade connection of several low-order time-varying filters with their zero frequencies adjusted by zero frequency offset. First, the frequency characteristics of this filter are analyzed. It is made clear that the zero multiplicity cannot be obtained, so that the clutter suppression performance is degraded in the case of a configuration consisting of a cascade connection of several time-varying filters with the same zero frequencies. The effectiveness of zero frequency offset is presented. Next, it is shown by computer simulation that a time-varying AMTI that provides the desired clutter suppression performance can be realized by means of the proposed method, while the computation effort can be reduced. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(9): 75–86, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10153 [ABSTRACT FROM AUTHOR]

The paper presents a new approach to multiple sensor bias estimation. It is applied to a practical example: correcting radar biases for ATC applications. A novel procedure to organise and process measurements is proposed and compared with classical approaches, which are shown to achieve inferior performance. It is shown how the exploitation of all available information allowed by the proposed data arrangement improves the accuracy of estimates. Besides, efficient implementations are developed and a cost-benefit analysis of the main alternatives for this problem is presented in the results. [ABSTRACT FROM AUTHOR]

Since the autocorrelation function of radar clutter between cells usually attenuates rapidly compared to that of the signal, the waveform after detection has larger changes in the clutter than the signal. Improving the signal-to-clutter ratio (SCR) in conventional radar relies on the integration effect of the amplitude, but here we tried to use the differences in the frequency components of the waveforms. We compared the output after detection obtained from aircraft flying over the ocean by asynchronous detection shipborne radar to the waveform that used Daubechies wavelet, and verified the effect. Next, we defined the signal area and the SCR and quantitatively calculated the improvement. Although we were able to verify an improvement of several decibels for a nearby target, the effect could not be obtained for a distant target. We could provide nearly the same improvement for all of the targets by changing the filter that varies the cutoff frequency with distance. In experiments, we were able to demonstrate a similar improvement by using wavelets in the detected output of the experimental Airport Surface Detection Equipment set up at Sendai Airport. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(10): 23–32, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1128 [ABSTRACT FROM AUTHOR]

The proposed phased array breaks the nexus between the surveillance and tracking functions of a radar system completely, and meets the modern challenges imposed by a dense multitarget environment where clutter, rain, or chaff are present. Compared to a conventional phased array, the novel array yields an order magnitude improvement in the time available to perform the above radar functions, and further improvements are easily attainable. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 189–192, 1998. [ABSTRACT FROM AUTHOR]

Compact-range radar backscatter measurements are taken of aircraft scale models. In addition, computer software is used to predict the RCS of the aircraft. Synthetic down-range profiles formed from the two sources of backscatter data are compared and visualized in an innovative manner. Similar discrimination rates between the two aircraft are obtained on data from both sources. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 207–213, 1998. [ABSTRACT FROM AUTHOR]

When a flying object tracks a target, the location and velocity of the target are estimated based on a target detection process using radar. In general, the constant false alarm rate (CFAR) is used in the target detection process. However, if a high power interference wave is received in addition to the object signal, the target cannot be detected, so that tracking fails. This is caused by an uncontrolled increase in the threshold level at the time of target detection due to the interference component mixed in the reference cells. After the CFAR process, tracking of the target is possible by the use of a tracking filter as long as the existing target signal component is detected, even if the interference wave is evaluated as the target signal component. In this paper, an interference adaptive CFAR is discussed in which the CFAR process is carried out and the interference component mixed in the reference cell is detected and eliminated. The relationship between the threshold coefficient and the false alarm probability and a computation method for the CFAR loss are formulated in this paper. By means of the derived relationships, several case studies are carried out and the nature of the interference adaptive CFAR is discussed. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(10): 29–37, 1997 [ABSTRACT FROM AUTHOR]

Typical problems for subsurface radar sensing are the existence of strong surface clutter and the difficulty in detection of deep targets due to the attenuation of electromagnetic waves underground. This paper proposes a method of enhancing deep target echo strength for FM-CW radar so that the radar sensitivity is proportional to the range. This technique is similar to the time sensitivity control circuits used for pulse radar, and is based on the differentiation property of the beat signal with respect to time. First, we show that this amplitude compensation approach is feasible both theoretically and experimentally in free space. Next, the validity of this method is confirmed by a subsurface target detection experiment using sandy ground. Finally, a hardware implementation in the FM-CW radar is described. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(6): 1–7, 1997 [ABSTRACT FROM AUTHOR]

The necessity for a multiple sidelobe canceller (MSLC) that suppresses several interference waves incident corresponding to complex radio environment is increasing. In the MSLC, there exists interference incident directions for which the suppression capability is degraded substantially, depending on the arrangement of auxiliary antennas. In this paper, the problem of degradation of the suppression capability of several interference waves depending on the direction of incidence is studied in the case where the two interference waves are suppressed by the MSLC with two auxiliary antennas. The relationship of the suppression capability to the receiving phase difference between the auxiliary antennas for each interference wave is discussed. Further, based on the results, an arrangement method of the auxiliary antennas minimizing the suppression capability degradation is presented. It is shown by numerical calculations that the suppression capability degradation can be improved by means of the configuration of the auxiliary antennas obtained by this method. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (1): 100–111, 1997 [ABSTRACT FROM AUTHOR]

In the frequency agility radar in which the transmit frequency of the radar can be changed at an ultrahigh speed, not only is excellent electronic counter counter-measure (ECCM) performance obtained but also improvement of the detection probability of the object with a fluctuating reflection cross section is expected. However, in the conventional-type radar, the frequency is modified at a high speed so as to change the entire pulse. However, the standard Doppler process is not possible. In this paper, in order to add a Doppler processing function to a frequency agility radar, the clutter is suppressed with one pulse and the obtained object signal is integrated coherently. The method and the simulation results are presented. [ABSTRACT FROM AUTHOR]

Surveillance of a region is conducted by using a search system to detect targets and a tracking system or force to follow them. After the search system detects a target, the tracking force will attempt to gain contact, usually by a local search. Before the tracking force detects the target, and thereby completes transfer, contact may be lost by the search system. If recontact is made by the search system, the new contact will be used by the tracking force to localize its search for the target. As the local search by the tracking force proceeds, contact by the search system may be lost and regained a number of times. The probability of transfer is obtained under the assumption that the transfer rate decreases as the time since last contact by the search system increases. The particular problem considered is that of sea surveillance for submarines, in which the search system is a fixed field of sensors and the tracking force consists of mobile units, such as ships, aircraft, and helicopters. However, the model can be adapted to other transfer problems, such as the transfer of a contact by a search radar to contact by a tracking radar. [ABSTRACT FROM AUTHOR]

Experimental verification is provided of the radar absorbing properties of an ultra-thin radar absorber. The absorber uses a commercially available conductive textile material uniformly coated with doped conducting polymer. The material is placed at a height of 0.12λ above a 4.6 GHz artificial magnetic ground plane. It is shown that with this arrangement better than -18 dB reflection loss can be obtained at 4.42 GHz. [ABSTRACT FROM AUTHOR]

A surface acoustic wave (SAW) and a leaky shear horizontal SAW (SH-SAW) have been simultaneously excited along A12O3[1 ... 00] on an A1N(0001)=A12O3(11 ... 0) structure. Both modes are highly sensitive to surface mass loading. The measured mass sensitivities are in good agreement with theoretical prediction, and are comparable or higher than those reported on other SAW devices. [ABSTRACT FROM AUTHOR]

By exploiting the approximate linear relation of the absolute Doppler centroid against the slant range, a novel approach is proposed for resolving synthetic aperture radar (SAR) pulse repetition frequency (PRF)-ambiguity with high computational efficiency. Accuracy analysis and the experimental results with real data both demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This article focuses on 7600 series of 2 Gsamples/s sampling downconverters from Picosecond Pulse Labs Inc. (PSPL). Replacing traditional mixers with the PSPL downconversion solution greatly reduces the complexity of current broadband radar system architectures. These new downconverter modules have high dynamic range, wide bandwidth, and large LO tuning range.

The design and performance of an MMIC burst oscillator that oscillates only while the driving pulse is applied are described. Since it does not generate carrier leak, a UWB radar using this oscillator may effectively mitigate interference with services using the restricted frequency band by locating its spectrum sufficiently far from the band. [ABSTRACT FROM AUTHOR]