Scheduled System Maintenance:
Some services will be unavailable Sunday, March 29th through Monday, March 30th. We apologize for the inconvenience.
By Topic

Popular Articles (February 2015)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. GSM passive coherent location system: performance prediction and measurement evaluation

    Publication Year: 2014 , Page(s): 94 - 105
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1357 KB)  

    This study describes the processing scheme of the FKIE (Fraunhofer Institute for Communication, Information Processing and Ergonomics) GSM-based passive coherent location (PCL) system, which consists of an antenna and signal processing adapted to the GSM waveform and of target tracking based on multi-hypothesis tracking. To overcome the limitations from a single bistatic transmitter-receiver pair, fusion of the measurements from different geometries is the key component of a GSM PCL system. The authors demonstrate a significant improvement in target position estimation from the tracking process on the basis of real data and theoretical performance bounds. The impact of the transmitter-target-receiver geometry is discussed and the effect of the exploitation of prior context knowledge (e.g. clutter and land maps) on maritime traffic surveillance is shown. View full abstract»

    Open Access
  • 2. Phase-sensitive FMCW radar system for high-precision Antarctic ice shelf profile monitoring

    Publication Year: 2014 , Page(s): 776 - 786
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (870 KB)  

    Ice shelves fringe much of the Antarctic continent, and, despite being up to 2 km thick, are vulnerable to climate change. Owing to their role in helping to control the ice sheet contribution to sea level change there is great interest in measuring the rate at which they are melting into the ocean. This study describes the development and deployment of an ice-penetrating phase-sensitive FMCW radar, sufficiently robust and with sufficiently low-power consumption to be run through the Antarctic winter as a standalone instrument, yet with the stability and mm-precision needed to detect the very slow changes in ice shelf thickness in this exceptionally demanding environment. A number of elegant processing techniques are described to achieve reliable, high-precision performance and results presented on field data obtained from the Larsen-C ice shelf, Antarctica. View full abstract»

    Open Access
  • 3. Performance assessment of pulse blanking mitigation in presence of multiple Distance Measuring Equipment/Tactical Air Navigation interference on Global Navigation Satellite Systems signals

    Publication Year: 2014 , Page(s): 647 - 657
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (851 KB)  

    It is known that the Aeronautical Radio Navigation Systems sharing the Global Navigation Satellite Systems (GNSS) frequency band represent a threat to the satellite-based navigation services. Distance Measuring Equipment (DME) and Tactical Air Navigation (TACAN) systems broadcast strong pulsed ranging signals within the Global Positioning System L5 and Galileo E5a frequency bands where the aviation positioning aids services are allocated. This study provides an experimental assessment of the DME/TACAN interference effect on the GNSS receivers performance in scenarios where the presence of several transmitters in view generates radio-frequency interference hard to mitigate by means of the classical solutions. In detail, analysis in terms of the receiver performance will be presented by showing the effect of the non-ideal pulse blanking on the GNSS signal quality. The optimal set-up of the mitigation process, investigated by means of a software simulation, is provided. View full abstract»

    Open Access
  • 4. Stepped frequency synthetic preprocessing algorithm for inverse synthetic aperture radar imaging in fast moving target echo model

    Publication Year: 2014 , Page(s): 864 - 874
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (827 KB)  

    This paper first introduces an accurate inverse synthetic aperture radar echo model for the fast moving targets. In this model, the target's motion during the time periods of the pulse transmitting, propagating and receiving have been taken into account, and some problems, which have been ignored in the `stop-go' model, may occur, for example, the varied ambiguity numbers and the drifted frequency centre. These problems will cause many difficulties in obtaining a high resolution range profile (HRRP) synthesis. To deal with these problems, a stepped frequency synthetic preprocessing (SFSP) algorithm is presented. The key of the proposed algorithm is synthetic preprocessing, including Doppler ambiguity suppression, echo coherence restoration and frequency centre correction, respectively. By completing the preprocessing, the HRRP can be achieved by a bandwidth synthesis and a well-focused image can be obtained by a keystone transform and an azimuth process, respectively. The simulation results validate the proposed SFSP algorithm by comparing it with the algorithm in the existing extended `stop-go' model. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 5. Analysis of radar micro-Doppler signatures from experimental helicopter and human data

    Publication Year: 2007 , Page(s): 289 - 299
    Cited by:  Papers (47)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1387 KB)  

    This paper highlights the extraction of micro-Doppler (m-D) features from radar signal returns of helicopter and human targets using the wavelet transform method incorporated with time-frequency analysis. In order for the extraction of m-D features to be realised, the time domain radar signal is decomposed into a set of components that are represented at different wavelet scales. The components are then reconstructed by applying the inverse wavelet transform. After the separation of m-D features from the target's original radar return, time-frequency analysis is then used to estimate the target's motion parameters. The autocorrelation of the time sequence data is also used to measure motion parameters such as the vibration/rotation rate. The findings show that the results have higher precision after the m-D extraction rather than before it, since only the vibrational/rotational components are employed. This proposed method of m-D extraction has been successfully applied to helicopter and human data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 6. Bayesian compressive sensing in synthetic aperture radar imaging

    Publication Year: 2012 , Page(s): 2 - 8
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (477 KB)  

    To achieve high-resolution two dimension images, synthetic aperture radar (SAR) with ultra wide-band faces considerably technical challenges such as long data collection time, huge amount of data storage and high hardware complexity. In these years, several imaging modalities based on compressive sensing (CS) have been proposed which can provide high-resolution images using significantly reduced number of samples. However, the CS-based methods are sensitive to noise and clutter. In this study, a new imaging modality based on Bayesian compressive sensing (BCS) is proposed along with a novel compressed sampling scheme. Clutter, which the previous CS-based methods not considered, is also included in this study. This new imaging scheme requires minor change to traditional system and allows both range and azimuth compressed sampling. Also, the Bayesian formalism accounts for additive noise encountered in the compressed measurement process. Experiments are carried out with noisy and cluttered imaging scenes to verify the new imaging scheme. The results indicate that the Bayesian formalism can provide a sharp and sparse image absence of side-lobes, which is the common problem in conventional imaging methods and has fewer artifacts compared with the previous version of CS-based methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 7. Classification of human motions using empirical mode decomposition of human micro-Doppler signatures

    Publication Year: 2014 , Page(s): 425 - 434
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1051 KB)  

    The ability to identify human movements can serve as an important tool in many different applications such as surveillance, military combat situations, search and rescue operations and patient monitoring in hospitals. This information can provide soldiers, security personnel and search and rescue workers with critical knowledge that can be used to potentially save lives and/or avoid dangerous situations. Most research involving human activity recognition employs the short-time Fourier transform (STFT) as a method of analysing human micro-Doppler signatures. However, the STFT has time-frequency resolution limitations and Fourier transform-based methods are not well-suited for use with non-stationary and non-linear signals. The authors approach uses the empirical mode decomposition to produce a unique feature vector from the human micro-Doppler signals following which a support vector machine is used to classify human motions. This study presents simulations of simple human motions, which are subsequently validated using experimental data obtained from both an S-band radar and a W-band millimetre wave (mm-wave) radar. Very good classification accuracies are obtained at distances of up to 90 m between the human and the radar. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 8. Two-dimensional location of moving targets within local areas using WiFi-based multistatic passive radar

    Publication Year: 2014 , Page(s): 123 - 131
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (587 KB)  

    In this study the authors investigate the two-dimensional target localisation capabilities of a passive radar system based on WiFi transmissions. It is well known that the most straightforward way to achieve the target position estimation in the horizontal plane with a passive radar exploits the measurements either of a single bistatic range plus a direction of arrival (DoA) or of two bistatic ranges collected by two separate receivers. However, for a practical application it is interesting to clearly define which one of the two approaches provides the passive radar target localisation with a higher accuracy and whether combining both multiple bistatic range plus DoA measurements provides a further advantage. A multistatic configuration is considered which allows to collect a set of range/Doppler/angle measurements for a given target. Different target localisation strategies are devised and compared, based on subsets of the available measurements with the aim of understanding the localisation accuracies achievable using the different combinations of measurements. Experimental results are shown based on a passive radar prototype developed and fielded at the DIET Department - Sapienza University of Rome. This will contribute to demonstrate the fruitful application of the passive radar concept for short range surveillance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 9. Direction of arrival estimation with a sparse uniform array of orthogonally oriented and spatially separated dipole-triads

    Publication Year: 2014 , Page(s): 885 - 894
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The problem of multiple incident signals' direction of arrival (DOA) estimation for spatially separated polarisation sensitive array (SS-PSA) is studied. The proposed SS-PSA is a sparse uniform array with orthogonally oriented and spatially separated dipole-triads. The proposed array can reduce the array mutual coupling by using the spatially separated polarised antenna instead of conventional spatially collocated polarised antenna. Moreover, the DOA estimation accuracy can be improved greatly due to the extended aperture offered by sparse array. Computer simulation results verify the effectiveness of the proposed algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 10. Use of sea clutter models in radar design and development

    Publication Year: 2010 , Page(s): 146 - 157
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Radar backscatter from the sea surface has a significant effect on radar systems operating in a maritime environment. This study considers the application of modelling sea clutter to the design and development of such systems, and addresses the sensitivity of the predicted performance to the choice of model. The typical phases of the life-cycle of a radar system are described, along with how models are used to support the radar development. Different types of model are reviewed and some examples are given of the comparison of their effect on predicted performance. The conclusion is that the differences are important and continue to warrant further investigation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 11. Mismatched filter for analogue TV-based passive bistatic radar

    Publication Year: 2011 , Page(s): 573 - 581
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (705 KB)  

    This study examines the problem of solving the range ambiguity in analogue TV (ATV)-based passive bistatic radar (PBR). When matched filter (MF) is applied to ATV-based PBR, a range ambiguity at 19.2 km will be produced because of the 64 s line fly-back time of the ATV signal. The relatively short range and the severity of this ambiguity make application of this type of waveform much more likely to be limited. A novel mismatched filter (MMF) algorithm is developed for solving the problem of range ambiguity. In this new MMF algorithm, the MMF factor is acquired based on minimising the overall impact of the SNR loss (SL) compared to MF and the range sidelobes energy that the authors want to suppress. And a batch version with much computational saving is also introduced. Then the performance of this batch version is studied in detail. Finally, its effectiveness is demonstrated with the application to real data acquired with an experimental PBR system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 12. Joint estimation algorithm for multi-targets' motion parameters

    Publication Year: 2014 , Page(s): 939 - 945
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    When multiple targets are within the same radar antenna beam and cannot be separated in the range dimension, the conventional imaging methods cannot be directly used to obtain a focused radar image. In this study, a new joint estimation algorithm for multi-targets' motion parameters is proposed. In this method, the first-order Keystone transform is first applied to correct the range walk of multiple targets simultaneously, and then the Lv's transform is used to estimate the motion parameters of targets including velocity and acceleration. The signal-to-noise ratio threshold for the proposed method is also given. The proposed method is fast and can obtain the accurate parameter estimation without knowing the number of targets and their motion information. Experimental results demonstrate the performance of the proposed algorithm. Comparisons between the proposed method and other methods, the maximum-likelihood method, fractional Fourier transform and discrete polynomial transform, are performed, which show that the proposed method can efficiently obtain the accurate parameter estimation with low computational burden. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 13. Constrained total least-squares localisation algorithm using time difference of arrival and frequency difference of arrival measurements with sensor location uncertainties

    Publication Year: 2012 , Page(s): 891 - 899
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (566 KB)  

    In this study, a constrained total least-squares (CTLS) algorithm for estimating the position and velocity of a moving source with sensor location uncertainties that uses the time difference of arrival and frequency difference of arrival measurements of a signal received at a number of sensors is proposed. The CTLS method, as a natural extension of LS when noise occurs in all the data and the noise components of the coefficients are linearly dependent, is more appropriate than the LS method for the above problem. By utilising the Lagrange multipliers technique, the known relation between the intermediate variables and the source localisation coordinates has been exploited to constrain the solution. In addition, the Lagrange multipliers can be obtained efficiently and robustly, which can allow real-time implementation as well as ensure global convergence. After a perturbation analysis, the bias and covariance of the proposed CTLS algorithm are also derived, indicating that the proposed CTLS algorithm is an unbiased estimator, and it could achieve the Craméŕ Rao lower bound (CRLB) when the measurement noise and the sensor location errors are sufficiently small. The simulation results show that the proposed estimator achieves remarkably better performance than the TLS and two-step weighted least squares approach, which makes it possible that the CRLB is attained at a sufficiently high noise level before the threshold effect occurs. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 14. Deinterleaving of radar signals and PRF identification algorithms

    Publication Year: 2007 , Page(s): 340 - 347
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (547 KB)  

    Electronic warfare (EW) receivers are passive receivers which receive emissions from other platforms, and do certain analysis on these emissions. Some EW receivers receive radar pulses, measure the parameter of each pulse received and group the pulses that belongs to the same emitter together to determine the radar parameters for each emitter. These parameters are then compared with values stored for known radar types, to identify the emitter type. Two parts are focused, emitters deinterleaving and PRF-type identification. The deinterleaving is done through parameters clustering. Two parameters are selected for clustering direction of arrival and radio frequency. A self-organising neural network called Fuzzy ART is proposed for clustering. This algorithm has a very good clustering quality and can run in real-time applications.The PRF-type identification is done through time-of-arrival (TOA) analysis. Three previously presented algorithms are combined in new scheme to do the TOA analysis (or PRF-type identification). These algorithms are difference TOA histogram, TOA folding histogram and sequence search algorithm. The complete proposed system has been tested using three different tests. These tests are simple PRI test, jittered PRI test and staggered PRI test. The proposed system identifies up to 90 simple emitters, 20 jittered emitters and 20 staggered emitters. In all tests, the data were simulated and generated using software. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 15. Ionospheric effects on synthetic aperture radar (SAR) clutter statistics

    Publication Year: 2013 , Page(s): 1004 - 1011
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Low-frequency space-based synthetic aperture radar (SAR) is an ideal sensor for measuring forest biomass, but can suffer from ionospheric effects. The variation in total electron content (TEC), originating from ionospheric turbulence, causes the along track point spread function (PSF) to degrade in a manner which depends on ionospheric conditions. In this study, the effect of this PSF on the single point statistics (probability density function) and two point statistics (autocorrelation function (ACF)) is derived. It is shown that the K-distribution order parameter is directly proportional to the ionospheric turbulence, as quantified by CkL. The complex ACF is a measure of amplitude scintillation, and the intensity ACF is a measure of both the order parameter and the terrain correlation length. A simulation is performed which clearly shows that measuring the order parameter ratio between ionospherically disturbed and undisturbed images is a measure of CkL. This measure can be used two orders of magnitude below the point where the ionosphere causes defocusing of the SAR image. It is concluded that the usefulness of this new measure can only be verified by experimental data since the temporal stability of the underlying order parameter is unknown. View full abstract»

    Open Access
  • 16. Multiple-element crosseye

    Publication Year: 2007 , Page(s): 67 - 73
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (573 KB)  

    An extension to the traditional two-element array crosseye interferometric electronic jamming technique is investigated. Simulations are performed to obtain excitations for multiple-emitter linear arrays that produce distorted wavefronts over desired regions of space. This results in a greater number of degrees-of-freedom and a better ability to control the desired field pattern. The crosseye effect can be achieved over wider sectors, but only by increasing array power. The technique is extended to two-dimensional arrays and is applicable to multi-function radar antennas. Experimental measurements performed on a four-emitter array demonstrate the feasibility of the technique. Good agreement with predictions is shown View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 17. Unsupervised classification based on non-negative eigenvalue decomposition and Wishart classifier

    Publication Year: 2014 , Page(s): 957 - 964
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2113 KB)  

    In this study, the authors propose an unsupervised terrain and land-use classification algorithm for polarimetric synthetic aperture radar (SAR) image analysis. Under the non-reflection symmetry condition, the non-negative eigenvalue decomposition (NNED) employing Arii volume scattering model is derived. They first apply NNED to divide pixels into three categories of surface, volume and double bounce scatterings. Then the pixels in each category are further divided into several classes based on the scattering characteristic parameter of the dominant scattering component. Utilising the initial classification result as training sets, the complex Wishart classifier can then be performed within each category or beyond categories to refine the final classification result. The effectiveness of this algorithm is demonstrated using the German Aerospace Center's E-SAR polarimetric data acquired over the Oberpfaffenhofen area in Germany. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 18. Sparse representation-based synthetic aperture radar imaging

    Publication Year: 2011 , Page(s): 182 - 193
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (934 KB)  

    There is increasing interest in using synthetic aperture radar (SAR) images in automated target recognition and decision-making tasks. The success of such tasks depends on how well the reconstructed SAR images exhibit certain features of the underlying scene. Based on the observation that typical underlying scenes usually exhibit sparsity in terms of such features, this paper presents an image formation method that formulates the SAR imaging problem as a sparse signal representation problem. For problems of complex-valued nature, such as SAR, a key challenge is how to choose the dictionary and the representation scheme for effective sparse representation. Since features of the SAR reflectivity magnitude are usually of interest, the approach is designed to sparsely represent the magnitude of the complex-valued scattered field. This turns the image reconstruction problem into a joint optimisation problem over the representation of magnitude and phase of the underlying field reflectivities. The authors develop the mathematical framework for this method and propose an iterative solution for the corresponding joint optimisation problem. The experimental results demonstrate the superiority of this method over previous approaches in terms of both producing high-quality SAR images and exhibiting robustness to uncertain or limited data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 19. Improved method for synthetic aperture radar scattered wave deception jamming

    Publication Year: 2014 , Page(s): 971 - 976
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (406 KB)  

    This study presents an improved scattered wave jamming method for synthetic aperture radar (SAR). The jammer adjusts the time-delay and the phase of the intercepted SAR signal. Then, a false scene is created to provide an effective protection for a certain area. It requires a lower jamming power than barrage jamming and has less computational complexity than direct-path deception jamming. Based on the performance analysis of scattered wave jamming, pulse repetition intervals to delay retransmission, and a modulation centre shift are proposed as improvements to enlarge the jamming area. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 20. MIMO-OFDM radar for direction estimation

    Publication Year: 2010 , Page(s): 28 - 36
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (315 KB)  

    Multiple-input-multiple-output (MIMO) radar makes use of orthogonal signals to obtain the phase delay for each transmitting/receiving antenna pair, and thus increasing the accuracy of direction estimation. The previously proposed MIMO radar assumes narrowband signals that guarantee the waveform orthogonality during the signals- transmission, propagation and reception. However, a narrowband system is unstable in target localisation because of the fluctuation of the target-s radar cross section. An MIMO-OFDM radar is proposed for target localisation. It adopts the OFDM technique to simultaneously transmit and receive a set of multiple narrowband orthogonal signals at orthogonal frequencies. A practical model accommodating a physical target is presented to simulate the MIMO-OFDM radar. As an example, a composite target composed of five infinite dielectric cylinders is localised by a four-element uniform linear array. The performance of the MIMO-OFDM radar is investigated by examining the estimation error for different numbers of sub-bands, different signal-to-noise ratios and different target directions. It is demonstrated by simulation that the MIMO-OFDM radar gives more statistically stable estimation by spreading the signal power over a wider spectrum. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 21. Compressive sensing-based ground moving target indication for dual-channel synthetic aperture radar

    Publication Year: 2013 , Page(s): 858 - 866
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    Multi-channel synthetic aperture radar (SAR) system has excellent performance of main-lobe clutter suppression. However, the resulting enormous amount of sampling raw data increases storage and transmission load. To alleviate such payloads, the authors propose a SAR/ground moving target indication (GMTI) method using compressive sensing (CS) with a very limited number of echo samples, based on the fact that the moving targets are usually sparse although clutter scattering centres are non-sparse in most cases. In the proposed method, dual channel SAR data are sampled sparsely in the azimuth direction and jointly processed. Firstly, a transform matrix is constructed to separate the energy support areas of moving targets from that of all scattering centres. Then, the authors can roughly obtain the energy support areas of all scattering centres via CS. Finally, based on the acquired energy support areas above, GMTI is achieved by solving a weighted l1 optimisation problem. Simulated and real data experiments demonstrate that the proposed method performs well with reduced sampled raw data, even if clutter scattering centres have a low-sparse level. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 22. Analysis of detection range of FM-based passive radar

    Publication Year: 2014 , Page(s): 153 - 159
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (615 KB)  

    This study presents an analysis of the detection range of a passive bistatic radar (PBR) by using FM radio transmitters as the illuminators of opportunity and the analysis of a required analogue-front-end dynamic range. Firstly, the theoretical considerations are presented in which the power budget is analysed, by taking into account the specific features of the PBR such as instantaneous reception of the direct illumination signal and weak target echoes and direct path interference removal. In the second part of this study, measurements performed by using an FM-based PBR demonstrator PaRaDe (passive radar demonstrator) are presented. The PaRaDe is a deployable system operating in real time, developed at the Warsaw University of Technology, Poland. The measurements include a scan of a typical spectrum in the range of 88-108 MHz, and the analysis of the long range detection of the air targets. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 23. Ultra wideband indoor navigation system

    Publication Year: 2012 , Page(s): 402 - 411
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (767 KB)  

    Typical indoor environments contain multiple walls and obstacles consisting of different materials. As a result, current narrowband radio frequency (RF) indoor navigation systems cannot satisfy the challenging demands for most indoor applications. The RF ultra wideband (UWB) system is a promising technology for indoor localisation owing to its high bandwidth that permits mitigation of the multipath identification problem. This work proposes a novel UWB navigation system that permits accurate mobile robot (MR) navigation in indoor environments. The navigation system is composed of two sub-systems: the localisation system and the MR control system. The main contributions of this work are focused on estimation algorithm for localisation, digital implementation of transmitter and receiver and integration of both sub-systems that enable autonomous robot navigation. For sub-systems performance evaluation, statics and dynamics experiments were carried out which demonstrated that the proposed system reached an accuracy that outperforms traditional sensors technologies used in robot navigation, such as odometer and sonar. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 24. Iterative least-squares-based wave measurement using X-band nautical radar

    Publication Year: 2014 , Page(s): 853 - 863
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1146 KB)  

    In this study, an existing iterative least-squares (LS) method for determining ocean surface currents from X-band nautical radar images is modified for extracting ocean wave information from the same data. Within each iterative step, the image spectra samples are classified as containing contributions from fundamental, first-order and higher harmonic waves or noise. Based on the classification result, a new scheme is proposed to increase the robustness of current estimation. This involves automatically adjusting the first threshold that is used for obtaining an initial guess of the current velocity in the iterative LS method. The proposed wave algorithm directly uses the classified fundamental and first-order harmonic wave components for wave spectra and parameter retrieval. Unlike previous wave analysis techniques in which a bandpass filter is required to eliminate the non-wave contributions after the current velocity is obtained, the proposed algorithm simplifies the wave retrieval without such a bandpass filter. Algorithm verification is first conducted by using simulated radar images. Subsequently, the method is applied to field radar data and the results are compared with wave-buoy measurements. Wave parameters from both types of data show that the modified wave algorithm produces results that are close to those achieved using traditional algorithms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 25. Performance of the adaptive generalised matched subspace constant false alarm rate detector in non-Gaussian noise: an experimental analysis

    Publication Year: 2009 , Page(s): 195 - 202
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The authors deal with the performance analysis of an adaptive version of the generalised matched subspace detector (GMSD) in compound-Gaussian clutter with unknown covariance matrix. The original GMSD was proposed to detect subspace signals in compound-Gaussian noise with known covariance matrix and ensures the constant false alarm rate (CFAR) property. In real situations, this assumption is unrealistic, which means that the covariance matrix must be estimated from training data. The authors use a robust estimate of the covariance matrix called the fixed-point estimate, recently proposed in the literature. The performance of the obtained adaptive detector, in terms of CFAR behaviour and probability of detection, is evaluated in the presence of real sea clutter data, collected by the McMaster IPIX radar. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 26. Design and performance evaluation of a mature FM/DAB/DVB-T multi-illuminator passive radar system

    Publication Year: 2014 , Page(s): 114 - 122
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1924 KB)  

    Passive radar (PR) systems use the target illumination by third-party transmitters, for example, from broadcast or cellular base stations, for target detection and localisation. Since PR does not use an own transmitter, it can be installed and operated at low cost and it is hard to detect and jam. These advantages and the increasing maturity of PR technology has led to growing interest in these systems over the last years. However, until now most PR systems have been rather experimental set-ups tailored to a single frequency band or implemented as laboratory test devices. This study in contrast describes the design, implementation and performance evaluation of a multi-band, multi-illuminator PR system developed at near-production stage. Starting out from a FM-broadcast-based approach, the step to DAB-based and DVB-T-based operation has already been made. As a result, a fully mobile FM/DAB/DVB-T multi-band PR system is now available, offering maximum flexibility for measurement campaigns with air, ground and sea targets. Experiments with a great variety of third-party transmitters and arbitrary transmitter-target-receiver geometries have been conducted. The design considerations and the resulting PR system concept are described, and the results of representative measurement campaigns with different types of ground and aerial targets are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 27. Wideswath synthetic aperture radar ground moving targets indication with low data rate based on compressed sensing

    Publication Year: 2013 , Page(s): 1027 - 1034
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Wideswath synthetic aperture radar/ground moving targets indication (SAR/GMTI) system increases severely data transmission and storage load. To mitigate this problem, a wideswath GMTI method based on compressed sensing (CS) is proposed. In this method, CS is utilised to process each SAR data sampled sparsely in the azimuth direction for multiple aperture systems after conventional range compression. Then the wavelet transform matrix is used to construct the sparse matrix. Each SAR image is unambiguously achieved by solving l1 norm optimisation problem in the azimuth. The clutter rejection is performed for all spatial SAR images and then moving targets can be well detected. In this way, the data rate together with storage load is reduced, and then the wideswath GMTI can be efficiently realised. Results of real measured and simulated SAR data processing demonstrate the effectiveness of the CS-based wideswath GMTI. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 28. Adaptive robust Kalman filter for relative navigation using global position system

    Publication Year: 2013 , Page(s): 471 - 479
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    An adaptive robust Kalman filter algorithm is derived to account for both process noise and measurement noise uncertainty. The adaptive algorithm estimates process noise covariance based on the recursive minimisation of the difference between residual covariance matrix given by the filter and that calculated from time-averaging of the residual sequence generated by the filter at each time step. A recursive algorithm is proposed based on both Massachusetts Institute of Technology (MIT) rule and typical non-linear extended Kalman filter equations for minimising the difference. The measurement update using a robust technique to minimise a criterion function originated from Huber filter. The proposed adaptive robust Kalman filter has been successfully implemented in relative navigation using global position system for spacecraft formation flying in low earth orbit, with real-orbit perturbations and non-Gaussian random measurement errors. The numerical simulation results indicate that the proposed adaptive robust filter can provide better relative navigation performance in terms of accuracy and robustness as compared with previous filter algorithms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 29. Advanced range migration algorithm for ultra-high resolution spaceborne synthetic aperture radar

    Publication Year: 2013 , Page(s): 764 - 772
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (559 KB)  

    To achieve ultra-high resolution images, processing algorithm of spaceborne synthetic aperture radar (SAR) faces significant challenges such as the curved orbit, the unneglectable propagation time and the space-variant effective velocity. In the light of imaging requirements of the ultra-high resolution spaceborne SAR, an advanced range migration algorithm (ARMA) is presented in this study. Firstly, a new slant range model is developed by incorporating straight orbit approximation with additional linear, cubic and quartic term. Subsequently, a two-dimensional spectrum is derived by making use of Fourier transform pairs and the approximate azimuth stationary point based on the new range model. Finally, a novel RMA is derived. In this algorithm, the accurate range cell migration correction (RCMC) is done through two steps: the effective velocity dependence RCMC and the bulk RCMC, and the range-variant azimuth filtering is accomplished. Simulations are carried out to verify our proposed algorithm, which indicate that ARMA can keep precise even the resolution is up to decimeter level. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 30. Classification of primary radar tracks using gaussian mixture models

    Publication Year: 2009 , Page(s): 559 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (430 KB)  

    Classification of primary surveillance radar tracks as either aircraft or non-aircraft is critical to a number of emerging applications, including airspace situational awareness and collision avoidance. Substantial research has focused on target classification of pre-processed radar surveillance data. Unfortunately, many non-aircraft tracks still pass through the clutter-reduction processing built into the aviation surveillance radars used by the federal aviation administration. This paper demonstrates an approach to radar track classification that uses only post-processed position reports and does not require features that are typically only available during the pre-processing stage. Gaussian mixture models learned from recorded data are shown to perform well without the use of features that have been traditionally used for target classification, such as radar cross-section measurements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 31. Iterative acquisition method based on Grey code for weak global positioning system signal

    Publication Year: 2014 , Page(s): 220 - 226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    For weak global positioning system signal, long coherent integration can improve the acquisition performance effectively, but the unknown data bits restrict the coherent integration interval within a data bit. Data bits estimation can extend coherent integration interval over multiple data bits with more Doppler frequency search bins. To lighten the calculation burden of data bit combinations searching, an iterative acquisition algorithm is presented based on ordering data bit combinations by Grey code. Modified block-accumulating coherent integration over extended interval (BACIX) algorithm is also presented, which has linear complexity and better performance than BACIX algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 32. Mitigation of stationary clutter in vital-sign-monitoring linear-frequency-modulated continuous-wave radars

    Publication Year: 2015 , Page(s): 138 - 144
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (629 KB)

    Stationary clutter can seriously degrade the performance of radar sensors. In the specific context of vital-sign monitoring, this deterioration can lead to the impossibility of tracking the desired motions. Pure linear-frequency-modulated continuous-wave (LFMCW) radars have arisen as an interesting solution to monitor vital signs, featuring both an increased phase-based range precision and an advantageous range-isolation capability. In this study, the impact of clutter on healthcare LFMCW radars is mathematically analysed and a Doppler high-pass filtering technique is proposed for its suppression. Simulation results are provided to highlight the key aspects of the derived mathematical framework and associated Doppler processing. Real experiments are also conducted to prove the validity of the devised clutter-mitigation procedure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 33. Adaptive beamforming for high-frequency over-the-horizon passive radar

    Publication Year: 2009 , Page(s): 384 - 405
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1465 KB)  

    Target detection and tracking systems using emitters of opportunity have received significant interest recently, especially those which exploit VHF and UHF broadcasts as signal sources in so-called passive radar systems. Here, the authors discuss an experimental system in the high-frequency (HF) band, where due to long-distance ionospheric propagation of radio waves in the 3-30-MHz spectrum, the illuminator may be located well beyond the line-of-sight. In this study, live data was recorded by a high dynamic range multi-channel digital receiver connected to a two-dimensional (L-shaped) antenna array, and signals from an uncooperative HF over-the-horizon (OTH) radar transmitter have been captured and analysed. As a preliminary step towards the development of a general HF-OTH passive radar system, the scope of this work is to compare the performance of conventional and adaptive spatial processing techniques in terms of their ability to cancel direct-wave interference and protect useful signal echoes to detect a small cooperative aircraft target. In particular, an alternative adaptive beamforming method specifically tailored to this application is proposed, and its practical performance is compared with classical and standard adaptive beamforming approaches. GPS data measured on-board the cooperative aircraft provided accurate ground truth of the flight path, enabling target profiles in bi-static range, Doppler frequency and direction-of-arrival (azimuth/elevation) to be calculated as a function of time. This information permitted the different processing schemes to be evaluated with a high degree of confidence. The experimental system and live data analysed are exclusively from the HF Radar program of the Defence Science and Technology Organisation (DSTO), Australia. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 34. Detection of high-speed and accelerated target based on the linear frequency modulation radar

    Publication Year: 2014 , Page(s): 37 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    The high-speed movement of a target may cause range migration and Doppler frequency migration of the radar echo, which has a serious impact on the detection performance of the radar. To resolve the problem of detecting a high-speed target in linear frequency modulation radar, this study analyses the effect on the integration gain caused by range migration and Doppler frequency migration, and proposes a corresponding compensation method according to the different input signal-to-noise ratios (SNRs) of the echo signal. To compensate for range migration in high SNRs, two-dimensional median filtering and constant false alarm rate technology are combined to estimate the speed. For low SNRs, based on coarse valuations, the authors use the discrete Fourier transformation (DFT) to realise the fractional delay cell to improve speed accuracy. Furthermore, to compensate for Doppler frequency migration, an instantaneous cross-correlation method is proposed for high SNRs, which is combined with the fractional Fourier transform method to estimate the acceleration for low SNRs. The input SNR threshold for the different algorithms is then analysed using simulation data, and the theoretical reference value is shown. Finally, the study verifies the effectiveness of the proposed methods through simulation and measured data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 35. Space-time adaptive processing for phased-multiple-input–multiple-output radar in the non-homogeneous clutter environment

    Publication Year: 2014 , Page(s): 585 - 596
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1147 KB)  

    This study presents some new methods for space-time adaptive processing for airborne multiple-input-multiple-output (MIMO) radar with co-located antennas in the non-homogeneous environment. The presented signal model is a general model for airborne phased-MIMO radar which can easily switch between conventional phased-array radar and MIMO radar to enjoy the advantages of the MIMO radar without sacrificing the main advantage of the phased-array radar which is the coherent processing gain at the transmitting side. In the non-homogeneous environment, the training data with the same statistical interference characteristics is not available to estimate interference covariance matrix, the authors present two space-time adaptive processing (STAP) approaches. The first one is based on the orthogonal projection on the clutter subspace which is applicable for known clutter signature scenarios. The matrix which describes the signature of ground clutter for airborne phased-MIMO radar is derived. For unknown clutter subspace, they propose the deterministic phased-MIMO STAP (also known as direct data domain approach) which suppresses the interference signal without the requirement for an interference covariance matrix. The parameters of deterministic phased-MIMO STAP are determined to maximise the degree of freedoms. Simulations are provided to demonstrate the performance of the proposed STAP approaches in the non-homogeneous environments. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 36. Ionospheric effects on three-dimensional imaging of L-band geosynchronous circular synthetic aperture radar

    Publication Year: 2014 , Page(s): 875 - 884
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    Circular synthetic aperture radar (SAR) imaging on the geosynchronous orbit has many potential advantages, such as high-resolution three-dimensional (3D) imaging and continuous surveillance of broad area. The mission considered is an L-band geosynchronous circular SAR (GEOCSAR) with full aperture measurement. Since the integration time of GEOCSAR can be as long as 24 h, the orbit altitude is about 36 000 km and the coverage may reach 1/3 of the Earth's surface. The spatial and temporal variation of the ionosphere may impose significant effects on 3D imaging performance of GEOCSAR. The effects of ionospheric spatial variation including vertical and horizontal structure, the ionospheric turbulence and the ionospheric temporal variation are discussed. The analysis shows that the temporal variation of the ionospheric electron content during the synthetic aperture and the ionospheric turbulence may severely affect the GEOCSAR focusing performance on the XY plane. The vertical and horizontal structure of the ionosphere will cause image shift, and the dispersion effect is negligible. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 37. Adaptive fractional fourier transform-based detection algorithm for moving target in heavy sea clutter

    Publication Year: 2012 , Page(s): 389 - 401
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1015 KB)  

    Attention has been focused on the moving target detection in heavy sea clutter. On the basis of detection model of moving target with fluctuant amplitudes, a novel adaptive algorithm in fractional Fourier transform (FRFT) domain is proposed, which combines statistic-based and FRFT-based detection method. FRFT has good energy concentration property on linear frequency modulation (LFM) signal with the optimal transform angle, which is determined by calculating spectral kurtosis (SK) in FRFT domain. Grading iterative search method is used for good accuracy of parameter estimation and fast calculation speed. A novel adaptive line enhancer (ALE) in FRFT domain is proposed to suppress sea clutter and improve signal-to-clutter ratio (SCR), which provides less error and faster convergence. Leakage factor is introduced into the update equation of weight vector to reduce `memory effect` and step size is normalised by the power of input signal with better convergence characteristic. In the end, both X-band and S-band real sea clutter is used for verification and the results present that the proposed algorithm has good convergence property and small mean square error (MSE). Weak moving target in low SCR environment (SCR = -6 dB) can be well detected and estimated, which indicates the effectiveness of the algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 38. Compressive high-range-resolution radar imaging using dynamic dictionaries

    Publication Year: 2013 , Page(s): 497 - 507
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1134 KB)  

    Compressive sensing theory suggests that accurate reconstruction of a signal can be achieved using its highly undersampled measurements, provided that the signal is sparse in an a priori known dictionary. For the range imaging problem in wideband radar, this dictionary is typically taken to be a DFT basis. However, since practical target scatterers do not lie exactly in the frequency lattice of the discrete Fourier transform (DFT) basis, there is always mismatch between the assumed DFT basis and the actual dictionary for sparsity. To address this, the authors consider the radar echo sparsifying dictionary as refinable and develop a compressive imaging approach using dynamic dictionaries. The approach treats the frequency gridding points as adjustable parameters of the sparsifying Fourier dictionary and achieves dynamical dictionary refinement via iterative optimisation of these parameters. To achieve joint image formation and dictionary refinement, the approach utilises the variational expectation-maximisation algorithm to iteratively perform a two-step process, that is, estimating sparse backscattering coefficients given a dictionary and then updating the dictionary to better fit the data sparsity model. The experimental results based on both synthetic and anechoic chamber data demonstrate that the approach improves the precision in range estimation and suppresses spurious spikes in the constructed profiles. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 39. New method for generating site-specific clutter map for land-based radar by using multimodal remote-sensing images and digital terrain data

    Publication Year: 2011 , Page(s): 374 - 388
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1508 KB)  

    By using multimodal remote-sensing images and digital terrain data of the environment, this study presents a new method for generating the clutter map specific to the selected land radar site and the radar's operating parameters. In the proposed method, the estimation of backscattering from the environment involves extrapolation of the airborne radar remote-sensing image to provide the baseline values, classification of multispectral remote-sensing satellite images to provide a detailed description of terrain types, use of digital terrain elevation data with the land radar position and height to provide local grazing angles and a terrain visibility map and use of the digital topographic map to provide the geometric reference for all data sets. Using actual remote-sensing images and digital terrain data acquired from a real environment with various terrain features, the clutter map generated by the proposed method for land-based radar is compared with that generated by the competitive modelling method. The accuracy of the proposed method is demonstrated based on the differences with respect to the actual clutter measurements using a different airborne radar-sensing configuration. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 40. Cramer–Rao bound of parameters estimation and coherence performance for next generation radar

    Publication Year: 2013 , Page(s): 553 - 567
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    In this study, a general signal-processing architecture is proposed for next generation radar (NGR). When the NGR works in MIMO mode, we derive the closed-form Cramer–Rao bound of the estimation of coherent-processing parameters, which include the time-delay differences and phase synchronisation errors among different apertures. When the NGR turns to work in fully coherent mode, assuming the time-delay differences are ideally compensated, the authors present the closedform signal-to-noise ratio (SNR) gain and analyse the SNR gain loss of the NGR because of inaccurate phase synchronisation errors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 41. Error model estimation for airborne beacon-based surveillance

    Publication Year: 2014 , Page(s): 667 - 675
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    A next-generation aircraft collision avoidance system under development is designed to reduce unnecessary alerts while reducing the risk of mid-air collision. Current and future collision avoidance systems rely upon range, bearing and altitude information from airborne, beacon-based surveillance. Realistic models of surveillance error characteristics are needed in order to develop and certify the safety and performance of these systems. Prior models of bearing measurements assumed uncorrelated Gaussian noise. This study explains how hidden Markov models can be used to capture the time-correlated error characteristics exhibited by recorded surveillance data. Simulations show the impact of this higher-fidelity model on predicted collision avoidance performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 42. Estimating building dimensions from synthetic aperture radar image sequences

    Publication Year: 2008 , Page(s): 189 - 199
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (705 KB)  

    The problem of automatically extracting building dimensions from synthetic aperture radar (SAR) image sequences of urban scenes is considered. An algorithm based on the delineation of shadows using active contours constrained by a simple wire-frame building model has been developed and demonstrated using SAR imagery of a village on Salisbury plain. The core of the algorithm is a novel technique for target delineation involving multiple active contours evolving simultaneously. In particular, a technique referred to as multiple hypothesis delineation, in which contours can be in several states simultaneously, is developed and shown to lead to considerable improvement in convergence time and delineation accuracy when used to delineate multiple targets in close proximity. The technique is applied to the automatic estimation of building dimensions by delineation of shadows in a sequence of SAR images of an urban scene. The estimation of building dimensions is automatic; user interaction is limited identifying a building of interest and a region of background clutter close to the building. Results are presented for six different buildings, in each case two SAR images were used in the estimation process separated in illumination angle by either 28deg or 90deg. The estimates of building dimensions are compared with the actual building dimensions obtained from architectural drawings. The algorithm was found to perform robustly and provide reasonably accurate estimates of the building dimensions, typically within ~10% of the true values. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 43. Clutter cancellation in passive radar using GSM broadcast channels

    Publication Year: 2014 , Page(s): 787 - 796
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (679 KB)  

    This study focuses on passive coherent location using global system for mobile communications base stations transmitting mainly dummy bursts in idle mode. The authors present adaptive delay line canceller techniques to suppress the zero-Doppler direct path and its clutter almost down to the receiver noise level. The proposed approaches offer the following two advantages compared with the other clutter cancellation techniques: they are fail-safe with respect to the errors in the reference signal extraction simply because they do not require any knowledge of the reference signal and they even work in severely non-stationary clutter conditions. The effectiveness of the approaches is demonstrated by means of measurements recorded with an experimental passive bistatic radar system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 44. High-speed multi-target detection with narrowband radar

    Publication Year: 2010 , Page(s): 595 - 603
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    High-speed multi-target detection is a challenging problem in radar applications. Typically, targets with high speed go through several range cells in the observation period, which makes it more difficult to obtain each target's power coherently accumulated for target detection. In this study, novel multi-target detection with a narrowband radar system is proposed. In order to remove range migration and obtain coherent integration of the target energy, the Keystone transform is applied to the moving targets. However, because of the high target velocity and the low radar pulse repetition frequency phase ambiguity will occur, so the range migration will not be corrected properly. Then the phase ambiguity function of the kth target is compensated, and the envelope of the kth target concentrates in a certain range cell. Following by frequency modulation rate search a quadratic phase term is compensated, and the signal energy is finally coherently accumulated by FT analysis. The target is detected if the ratio of peak value to noise is higher than a predetermined threshold. For target detection in low signal-to-noise ratio (SNR), the Clean technique is applied. The proposed algorithm is verified by simulation and raw radar data results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 45. Compressed sensing parallel factor analysis-based joint angle and Doppler frequency estimation for monostatic multiple-input–multiple-output radar

    Publication Year: 2014 , Page(s): 597 - 606
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    In this study, the authors discuss the topic of joint angle and Doppler frequency estimation in a monostatic multiple-input-multiple-output radar and a compressed sensing parallel factor (CS-PARAFAC) analysis-based algorithm is proposed. In this algorithm, the joint estimation problem is firstly linked to the compressed sensing trilinear model, then the estimated compressed matrix can be derived through trilinear alternating least square method and the angle and Doppler frequency are jointly estimated with sparsity from the compressed matrices. The proposed CS-PARAFAC algorithm, which can obtain automatically paired angle and Doppler frequency estimation, has very close estimation performance to the conventional parallel factor analysis algorithm. When compared to the conventional subspace-based algorithm, such as estimation of signal parameters via rotational invariance techniques, it can achieve much better joint angle and Doppler frequency estimation performance. As the compression, the proposed algorithm has much lower computational complexity and smaller memory capacity meanwhile. Numerical simulations verify the efficiency and illustrate performance improvement of the proposed algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 46. Double phase estimator: new unambiguous binary offset carrier tracking algorithm

    Publication Year: 2014 , Page(s): 729 - 741
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (954 KB)  

    Several new global navigation satellite system modulations adopt a binary offset carrier (BOC) subcarrier to shape the signal spectrum, increase the frequency separation and improve the tracking performance. BOC modulated signals are, however, characterised by ambiguous multi-peaked correlation functions and several techniques have been proposed in the literature to solve the problem of locking into secondary peaks. In this study, a novel unambiguous BOC tracking technique, the double phase estimator (DPE), is designed to account for the effect of signal bandlimiting. The DPE is an effective alternative to the double estimator (DE) tracking technique where the subcarrier lock loop is replaced by a subcarrier phase lock loop. In the presence of signal bandlimiting, the DPE is able to generate local signal replicas matched in a better manner to the input components, outperforming the DE. The performance of the DPE is thoroughly characterised and the processing of real wideband BOC signals is used to demonstrate the effectiveness of the algorithm proposed. In addition to this, the DPE requires a lower computational load than the DE and thus should be adopted for the processing of wideband BOC signals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 47. Effects of K distributed sea clutter and multipath on radar detection of low altitude sea surface targets

    Publication Year: 2014 , Page(s): 757 - 766
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Sea clutter and multipath scattering affect the detection performance of sea surveillance radar simultaneously when the radar detects low altitude target over the sea. In this study, the effects of K distributed sea clutter and multipath on radar detection performance for low altitude sea surface targets are analysed. First, the probability density function of the multipath power propagation factor is derived by taking specular and diffuse reflections into account. Based on this, mathematical expressions of radar detection and false alarm probabilities in K distributed sea clutter and multipath are further derived. The radar detection performances in various K distributed sea clutter and multipath circumstances by simulation are presented, and the impacts of K distributed clutter and multipath on radar detection performance are analysed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 48. Non-cooperative target recognition in multistatic radar systems

    Publication Year: 2014 , Page(s): 396 - 405
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    The ability to recognise quickly and reliably non-cooperative targets is a primary issue in modern radar systems. The use of multistatic radars has already been demonstrated to improve sensibly the recognition capacity of a radar system, through the exploitation of its inherent spatial diversity, given by the presence of multiple observation channels. This calls for the development of suitable fusion strategies for efficiently combining the signals arising from multiple channels of the network. In this study, the authors define a multistatic classification algorithm where the information on the target class is provided by the sensors of the system and the final decision is made using a fusion rule that combines the decisions coming from each channel of the radar network. A suitable selection is made to favour the channels with better performance. The numerical analysis demonstrates the superior performance of the proposed algorithm over the classical fusion rule, that takes into account only the effect of the energy path loss, in terms of probability of correct classification. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 49. Cram??r-Rao lower bound with Pd < 1 for target localisation accuracy in multistatic passive radar

    Publication Year: 2014 , Page(s): 767 - 775
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    By exploiting the sources of opportunity not designed for radar applications, the passive radar system often operates with a Pd in the range from 60 to 85% for acceptable false alarm rates. Multistatic radar networks can be used to both increase detection capability and localisation accuracy. The standard Cramér-Rao lower bound (CRLB) cannot be used for a realistic assessment of the target localisation accuracy in a surveillance area since it provides optimistic predictions. In this study, the authors derive the CRLB with missing observations, namely for Pd <; 1, for the multisensory case. The results are illustrated for the case study of a multistatic passive radar exploiting FM radio transmissions where each bistatic pair within the network is assigned with a detection probability for each target position in the surveillance area. The obtained CRLB with Pd <; 1 is then employed to compare the localisation performance achievable by a multistatic passive radar when using different sets of measurements: (A) only range measurements, (B) range and Doppler frequency measurements and (C) Doppler frequency measurements only. The reported results show that the proposed CRLB with Pd <; 1 yields a more reliable prediction of the achievable performance thus allowing a fair comparison of the above different strategies for target localisation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 50. Fifty years of instantaneous frequency measurement

    Publication Year: 2012 , Page(s): 112 - 122
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1021 KB)  

    Quadrature phase discriminators, the core of wideband instantaneous frequency measurement (IFM) receivers and multiple base-line interferometry for accurate direction finding (DF), were invented in 1957, by S.J. Robinson of Mullard Research Laboratories (MRL). Digital instantaneous frequency measurement (DIFM) receivers have been universally used operationally for wideband monitoring of radar environments in naval, airborne and ground-based electronic support measures (ESM) systems all over the world for over 50 years. Their importance is such that many countries have developed their own IFM manufacturing capability with just minor architectural changes to the original design. This study describes the invention sequence, the development history, IFM design and performance principles, its general use and limitations in modern electronic warfare (EW) systems and ends with a projection for the future. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IET Radar, Sonar & Navigation covers the theory and practice of systems involving the processing of signals for radar, radiolocation, radionavigation and surveillance purposes.

Full Aims & Scope

Meet Our Editors

Publisher
IET Research Journals
iet_rsn@theiet.org