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This study considers the detection problem of multiple-input multiple-output (MIMO) radar in the presence of a compound-Gaussian clutter. Two new detectors based on the Rao and Wald criteria are devised under the known covariance matrix. The theoretical expression for the probability of false alarm is developed and constant false alarm (CFA) rate behaviour is remarked on. Furthermore, the fully adaptive approximated Rao and Wald tests are investigated in place of the exact covariance matrix with a suitable estimator using secondary data. Finally, several numerical simulations with typical parameters are provided and discussed. [ABSTRACT FROM AUTHOR]

Compared with other systems with a single transmit antenna, multiple-input multiple-output (MIMO) radar systems have additional degrees of freedom that can enhance space resolution, improve parameter identifiability and enhance flexibility for transmit beam pattern design. The computational complexity for direction of arrival (DOA) estimation using sensor arrays increases very rapidly with the number of channels. The polynomial-rooting version of multiple signal classification algorithm (root-MUSIC) is computationally more efficient than spectral MUSIC. However, this algorithm can only be applied to uniform linear arrays. The manifold separation technique allows arrays of any geometry to be used with fast DOA estimators designed for linear arrays. In this study, a DOA estimation method that uses manifold separation and polynomial rooting technique is presented for monostatic MIMO radar with arbitrary array configuration. The algorithm offers a low computation complexity and an improved resolution capability for closely spaced sources as compared to conventional spectral MUSIC. Moreover, the wavefield modelling for monostatic MIMO radar and the number of mode selection of the proposed method are also analysed in the study. Finally, the simulation results are presented and the performances of the proposed algorithm are investigated and discussed. [ABSTRACT FROM AUTHOR]

Randomisation of element positions in a sparsely populated, non-uniform antenna array is a well-known approach in communication systems for controlling grating lobes and allowing improved spatial resolution for a given number of antenna elements. MIMO array techniques have been applied more recently to radar systems with a view to improving the versatility and performance, particularly angular resolution, of a system with a given number of elements. A sparsely populated, non-uniform MIMO array would therefore seem a logical and attractive combination, though its performance is rather more difficult to predict and less easy to control because of geometrical constraints. This study sets out to examine the spatial sidelobe performance and potential for grating lobe control of a sparsely populated MIMO radar array architecture using antenna position randomisation to suppress grating lobes. [ABSTRACT FROM AUTHOR]

The first modern bistatic radar system, Klein Heidelberg (KH), was developed by the Germans during World War II to exploit the transmissions from the British Chain Home (CH) radars and achieved detection ranges against Allied bombers well behind CH. The small backlobe of the system would also have unavoidably detected German aircraft flying behind KH. After estimating the front-back ratio of the antenna, the detection ranges of these German aircraft were derived, showing that they would have been detected out many tens of kilometres and have been incorrectly plotted as Allied aircraft flying well over South East England. While this study is essentially historical in nature, it is based on data in intelligence reports that were declassified only recently and illustrates the need for designers of such systems to anticipate all unwanted modes of operation. [ABSTRACT FROM AUTHOR]

An X-band power amplifier (PA) is presented for single-chip phased array radar applications. In this work, the choice of optimum circuit topology for X-band PA design is discussed and possible stability issues for high and low frequencies are analysed. The PA features a two-stage cascode architecture that includes both high-speed (low breakdown) and high breakdown (low-speed) SiGe transistors. It consists of two stages providing a 23.2 dBm saturated output power with a 28% power-added efficiency at 9 GHz. The output 1-dB compression point (P1dB) is higher than 20 dBm in a 3 GHz bandwidth and has a maximum value of 22.2 dBm. The small-signal gain is 25.5 dB with a 3-dB bandwidth of 3.2 GHz (7.3-10.5 GHz). The PA has been fabricated using 0.25 µm SiGe BiCMOS process provided by IHP Microelectronics. The PA occupies 1 mm×0.6 mm chip area and consumes 120 mA from a 4 V supply voltage. These results demonstrate comparable or better performance than other reported PAs and suitable performance for single-chip phased array applications. [ABSTRACT FROM AUTHOR]

During the operation of the multifunction radar system, all the tasks related to the functions of the radar must be launched. The key element of the radar responsible for managing all these tasks is the task scheduler. Many scheduling techniques give good results at the expense of too complex and expensive designs. This study presents the results of a model for a radar task scheduler to achieve both a simple design and a good performance. The scheduling process consists of three stages in which the whole scheduling is divided into: task priorisation, scheduling algorithm and temporal planning. A task priority method is established to be applied to the tasks and the scheduling algorithms that have been tested based on this criterion for the priority task queue building. The authors have developed a software platform for testing all scheduling algorithms. The evaluation of the schedulers was made based on a set of features of the radar to measure the system's performance from the timing and the tasks execution. The authors offer a model to test the global radar system focusing on the task scheduler. This way allows us to analyse different scheduling algorithms and policies, and applying specifically scheduling policies that give priority to the most important and critical tasks. [ABSTRACT FROM AUTHOR]

It is an important work to classify the modulation type of the intercepted radar signal for an electronic intelligence (ELINT) receiver in a non-cooperative environment. The authors use the Rihaczek distribution (RD) and the Hough transform (HT) to concentrate the energy in time-frequency plane and derive two new characteristic features, namely the ratio of the minimum to the maximum of the HT and the peak number of the HT of the real part of the RD, to improve the probabilities of successful recognition (PSRs) to recognise the classical low probability of intercept (LPI) radar signals. The first feature is especially suitable for the linear frequency modulation (LFM), whereas the second one is specifically designed for frequency shift keying (FSK). The choice of thresholds and the effects of signal parameters are analysed. Simulations show that the PSRs can reach 90% when the signal-to-noise ratio (SNR) is above -4 dB. The proposed algorithm is better than the previous algorithms by just using ambiguity function. [ABSTRACT FROM AUTHOR]

The article offers world news briefs as of June 2012. Aboitiz Power Corp. is spending 850 million U.S. dollars to build a new power generating plant in Mindanao Islands, Philippines to counter the power shortage. Panasonic Corp. has developed a new radar system that can detect humans and vehicles over a wide range while on the road. Great Britain's Ministry of Defense has announced that the Joint Strike Fighter jets will be short take-off and vertical landing variant.

This study presents an X-band low noise amplifier (LNA) implemented in 0.25 µm SiGe BiCMOS process aiming for phased array radar applications. The LNA is composed of two cascode stages using SiGe heterojunction bipolar transistors to achieve low noise figure, high gain and a better matching to 50 Ω at the input and output, simultaneously. The first stage is designed for low noise performance whereas the second stage is optimised to improve the input third-order intercept point (IIP3). The LNA resulted in a measured gain of 21 dB, a noise figure of 1.52 dB and an IIP3 of -8 dBm at 10 GHz. The active chip area without pads is 620×820 µm2 and the power dissipation is 22 mW from a 2.2 V power supply. These performance parameters collectively constitute the best figure-of-merit value of 101, reported in similar technologies. [ABSTRACT FROM AUTHOR]

In this study, the issue of phase discontinuity in multiple-input-multiple-output (MIMO) radar systems is analysed and described in detail, together with an efficient way for processing MIMO radar data by means of discrete-time Fourier transform (DFT) fast Fourier transform (FFT). In particular, here it is shown that the phase history of a point target illuminated by an MIMO radar shows a number of discontinuities because of the geometry of the antennas. It is also shown that these become negligible in the far range, whereas they represent an issue in the short range if not compensated properly because, in turn, they prevent DFT-based algorithms correctly focusing the received signals. It is shown that data from MIMO radars have to be pre-processed in order to allow an efficient DFT-based focalisation. For this purpose, together with a theoretical description of the problem, a sub-optimal algorithm is presented, discussed and tested against real data gathered by the Joint Research Centre (JRC) MIMO radar system. [ABSTRACT FROM AUTHOR]

In noise radars, measuring the cross-correlation between transmitted and received signals is a common method of signal processing. However, it brings a lot of unwelcome sidelobes that can mask weak echoes of far targets. There are many classical and modern methods of masking effect removal which are based on signal processing in the receiver side. In this study, a method of waveform design is presented and its ability to reduce masking effect is compared with that of radars using purely random waveforms. The method starts with choosing an arbitrary subsequence and continues with attaching new subsequences to the previous ones in a way that the sidelobe levels reduce. In addition, the performance of applying the well-known CLEAN algorithm to a purely random waveform and the presented waveform are considered in detail. Moreover, the waveform randomness is measured and compared with purely random waveforms. By means of computer simulations, it is illustrated that the proposed waveforms can produce smaller correlation sidelobes, while preserving their randomness characteristics. [ABSTRACT FROM AUTHOR]

The authors investigate the feasibility of classifying different human activities using ultra-wide band (UWB) radar. Eight human subjects performing eight different activities are measured using a UWB radar. The eight activities include walking, running, rotating, punching, jumping, transitioning between standing and sitting, crawling and standing still. The dimension of the UWB returns is reduced using principal component analysis (PCA). The time-varying UWB signatures are characterised within a time window through observing the variation of the PCA coefficients. A support vector machine (SVM) is used to classify the activities based on the signatures. A multi-class classification is implemented using a one-versus-one method. Optimal parameters for the SVM are found through a 4-fold cross-validation. The resulting classification accuracy is found to be more than 85%. The potential of classifying human activities with different ground planes and with cluttered environments is also investigated. To extract more information regarding the target motion, human walking style classification with the developed method is also discussed. [ABSTRACT FROM AUTHOR]

Ionospheric clutter mitigation for high-frequency surface-wave radar using a two-dimensional array and beam space processing is presented here. The new antenna system with both azimuth and elevation angle resolving power is capable of exploiting the difference in both azimuth and elevation angles between wanted target echoes and unwanted ionospheric clutters, giving it an advantage over conventional one-dimensional linear arrays. In addition, the beam space processing can effectively preserve target echo energy during interference cancellation. Measured data from a real high-frequency surface-wave radar system is used to evaluate the performance of the new method. [ABSTRACT FROM AUTHOR]

Polarisation filtering is a valid approach for interference suppression in high-frequency surface wave radar (HFSWR) and other systems. Based on the fundamental principle of the oblique projection and polarised filtering, an oblique projection polarisation filter (OPPF), which can be constructed from the polarisation subspaces of the target signal and those of the interference or directly from experimental data, is proposed in this study. Generalised methods for constructing the OPPF operators (theoretical OPPF and improved OPPF) are provided and the impact on the performance caused by the estimation errors is also discussed. Numerical results from simulation and experimental data demonstrate that the proposed filter is an effective means of interference cancellation. It is proved that OPPF is an extension of the conventional polarised filter, whereas the improved OPPF is more suitable for the situation where the interference is unknown. [ABSTRACT FROM AUTHOR]

In this study, a practically efficient method is proposed to detect range-spread targets of manoeuvring flight in white Gaussian noise. High-resolution range profiles (HRRPs) from multiple consecutive pulses are stacked into a two-dimensional (2D) greyscale range-pulse image along range cells and pulses. Based on the local statistics of the images, a 2D non-linear shrinkage map is designed for reducing noise while preserving target echoes before integration. Then, a geometric average (GA) integrator, operating on filtered HRRPs, is designed for target detection. The GA integration exploits the waveform similarity of the filtered target HRRPs. Finally, the experimental results of raw radar data and comparisons with other detectors are reported, showing that the proposed detector can efficiently detect range-spread targets of manoeuvring flight in white Gaussian noise. [ABSTRACT FROM AUTHOR]

This study is concerned with the performance analysis of detection problem in statistical multiple-input multiple-output radars for Gaussian interference. This subject has been addressed in some publications for such special cases as white Gaussian noise and orthogonal transmission. However, theoretical performance analysis of optimum detector for general case including coloured Gaussian interference and arbitrary transmission signal has not been reported yet. In the present study, after developing the optimum detector for a general case, exact closed-form expressions are derived for the probability of detection and false alarm. As the derived expressions have complicated form, their interpretation is not tractable in the general case. Therefore lower and upper Chernoff bounds are obtained to provide better insight into the detector performance. Furthermore, the effect of various parameters on the detector performance is investigated by Monte-Carlo simulations. Numerical analysis shows a high degree of consistency between the theoretical and Monte-Carlo simulation results. [ABSTRACT FROM AUTHOR]

The authors start by analysing the mean square error (MSE) of target velocity and location estimation in ultrawideband (UWB) multi-input-multi-output (MIMO) noise radar. In the authors' system architecture, transmit antennas are illuminated by UWB-independent noise waveforms to meet the requirement of MIMO spatial diversity. The ambiguity function (AF) formulation is applied to implement the estimations. Since the maximum value of the AF is attained when the time-delay and Doppler stretch of replica signals are exactly matched with the ones corresponding to the reflections, this estimation is also a peak localisation problem. When noise is added, the peak may be located in a different place causing error. In this study, the authors formulate probability density functions (pdfs) to approximate the distributions of coherent and non-coherent ambiguity functions (CAFs and NCAFs) that are then applied to analyse MSE of their estimates. The pdfs are also applied to analyse the detection performance based on different AF approaches. Based on the analyses, the authors demonstrate that the NCAF-based estimation is a better approach in spatial diversity MIMO radars. [ABSTRACT FROM AUTHOR]

The authors present a computationally efficient method for designing practical radar transmit waveforms that maximize the signal-to-interference-plus-noise ratio (SINR) in a known additive coloured Gaussian noise environment. The problem reduces to a non-linear constrained optimisation in which the authors seek the SINR-maximising transmit waveform that has a specified envelope and an acceptable autocorrelation sequence (ACS). The waveform ACS can be constrained either directly or indirectly. The direct approach involves forcing the ACS magnitude below a specified level at each lag. This provides the greatest control over the waveform ACS, but it is too computationally demanding for many realistic problem sizes. Indirect methods of ACS constraint can be computationally less demanding, but they afford only inexact control over the waveform ACS. The leading indirect approach, which relies on the so-called similarity constraint, requires significantly fewer calculations than the direct approach, but it provides significantly less SINR improvement. The indirect approach presented here relies on a parametrisation of the phase perturbations of a linear frequency modulated waveform. This approach requires fewer calculations than the direct approach, and can provide more SINR improvement than the similarity constraint approach. As such, this new approach may be preferable when computation time is limited. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Large sensor arrays are widely used in various applications, such as radar, sonar and so on, to gain predominance in detection range and spatial resolution capability, but the tremendous sensor number casts a significant computational load on the subsequent target location if the super-resolution subspace-based methods are exploited. This study presents a computationally efficient direction-of-arrival (DOA) estimation method for independent stochastic signals using large uniform linear arrays (ULAs). Only simple numerical calculations are included in the proposed method, so it is computationally much more efficient than previous subspace-based methods. The signal power estimates are also available from the proposed method just by solving another over-determined linear equation set. Numerical simulations are carried out to show that the proposed method obtains DOA and signal power estimates in high precision, and it owns robustness against non-uniform and correlated noise. [ABSTRACT FROM AUTHOR]

Classification of targets using their micro-Doppler signatures has attracted a growing interest in recent years. In addition to their main bulk translation, targets may exhibit additional motions, such as vibrations and rotations, which generate Doppler modulations in the echo that contain unique target features and thus can be used to perform target recognition. Although target classification by micro-Doppler signatures has been exploited in the radio frequency regime for radar systems, much less work has been done in acoustic. In this work, an ultrasound radar operating at 80 kHz has been developed to gather micro-Doppler signatures of personnel targets performing various actions. The performance of a range of classifiers and feature extraction algorithms in distinguishing between these micro-Doppler signatures is presented. [ABSTRACT FROM AUTHOR]

The scheduling of tracking and surveillance looks for multifunction radar is considered. A technique called the sequential scheduler is proposed, whereby tracking looks and high-priority surveillance looks are scheduled first, and lower-priority surveillance looks are then scheduled to occupy gaps in the radar time line. A method called the two-slope benefit function (TSBF) sub-scheduler is used and requires that each tracking look and high-priority surveillance look has a benefit function, which specifies benefit as a function of start time. This method accounts for both look priority and target dynamics in formulating a look schedule. If the radar is overloaded with tracking look requests, the TSBF sub-scheduler down-selects a set of looks that can be scheduled, using a method that favours higher priority looks. Looks are scheduled to maximise the total benefit, and it is shown that the resulting maximisation is equivalent to a linear program which can be solved efficiently using the simplex method. A technique called the gap-filling sub-scheduler is used to schedule lower-priority surveillance looks. An example is presented which illustrates the properties of the sequential scheduler. [ABSTRACT FROM AUTHOR]

This study presents a new type of compact highly selective ultra wideband (UWB) bandpass filter (BPF) that exhibits a quasi-elliptic function response. By using the quasi-lumped element concept, a broadside coupled resonator is designed to implement a transmission zero at lower stopband, and some shunt resonators are adopted to generate transmission zeros at the upper stopband. Hence, very selective performance with a quasi-elliptic function response is achieved. Two UWB filters are designed for the demonstration. The first filter is designed with a passband from 3.1 to 10.6 GHz for the Federal Communications Commission (FCC)-defined indoor limit application, and the second filter is designed with an even wider passband from 3.0 to 16.2 GHz, showing the flexible wide passband performance of the proposed filters. Experiments are carried out to validate the designs. A low cost multilayer liquid crystal polymer technology is deployed to implement the proposed filters. Small sizes for fabricated filters are achieved, which are 8.8 mm×9.0 mm×0.5 mm and 6.4 mm×5.9 mm×0.2 mm, respectively. All the measured filters have excellent performance, including low insertion losses, flat group delay and high selectivity. The proposed new type of UWB BPF is favourable for practical UWB communication and radar systems. [ABSTRACT FROM AUTHOR]

This study addresses the waveform design problem of high-resolution radar, especially for dense target environments when the detection of small targets in the neighbourhood of large target is more important. Such a practical application demands an ambiguity function with a sharp central spike and large clear area around it, which is free from the sidelobes. This study investigates the sidelobe-pushing property of the Linear Congruence (LC) Codes that can produce the desired sidelobe-free area around the mainlobe. Minimum Sequence Length Criteria for achieving the desired sidelobe-free area are also described. In order to achieve the sharp central mainlobe in the delay-Doppler plane for resolving closely spaced targets, modifications are suggested to the LC codes and such modified sequences are called 'Modified Linear Congruence Codes'. The designed codes are highly suitable in dense target scenarios as well as in multi-radar environments. [ABSTRACT FROM AUTHOR]

Practical problems on target localisation and tracking arise in many military and civilian applications. This study investigates a problem on locating and tracking a manoeuvring target for a multistatic radar system. An approach that combines the interacting multiple model (IMM) method with variants of particle filters is implemented. The IMM method accounts for mode switching, whereas the particle filters account for non-linearity and/or non-Gaussianity in the dynamic system models for the posed problem. The approach consists of a constant velocity model, a constant acceleration model and a coordinated turn model. This work considers six combinations of extended Kalman filters (EKFs), unscented Kalman filters (UKFs) and particle filters for the models. A simulation study is carried out to evaluate the implemented IMM algorithm variants. Based on the test results obtained, IMM variants that use computationally efficient particle filters in the coordinated turn models, with EKFs and/or UKFs in the remaining models possess potential to achieve superior accuracy in state estimation for problems with significant non-linearity and/or non-Gaussianity. [ABSTRACT FROM AUTHOR]

One may describe the effect of a radar or sonar target on an incoming signal as a filter that produces a scattered signal. Chaotic signals are very sensitive to the effect of filters, and so a radar or sonar target imposes a unique signature on a scattered chaotic signal. In this study the authors describe a method that uses the concept of phase space dimension to create a reference from a scattered chaotic signal. This reference becomes part of a library, and comparing an unknown scattered signal to this library can reveal which target caused a particular scattered signal. As the authors are not imaging the target, this method can use signal with low-range resolution. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) geometry of extended objects is modelled as a discrete constellation of a small number of scattering centres. Each scattering centre is characterised by its 2D location and extension, as well as by its observability from aspect angles spanning a wide angular interval. The considered input information of the modelling consists of high range resolution (HRR) data sets, which are measured by a network of scanning surveillance radars from a limited set of aspect angles of the object. During the short time-on-target of the antennas within each radar scan, inverse synthetic aperture radar (ISAR) imaging is performed. The Expectation-Maximisation (ER) algorithm is applied in order to fit each ISAR image to a Gaussian mixture model (GMM), pertaining to the aspect angle applicable to the respective radar. A merging algorithm for clustering all the partial GMMs into a unique 2D model of the extended object is designed. Cluster validation criteria are applied for correct alignment of the multi-radar multi-scan object model estimates. A Mixture of Gaussians classifier (MOGC), which is based on representation of each object by the estimated 2D model, is discussed. Results from application of the algorithms to two measured HRR radar data sets are presented. [ABSTRACT FROM AUTHOR]

In diversity multiple-input multiple-output (MIMO) radar system, the mutual correlation of target echo signals in its diversity channels is an important concern for designing signal processing algorithms. The target temporal, spatial and frequency correlation characteristic is studied at the background of a diversity MIMO radar with multiple widely separated radar sites all capable of working at multiple carrier frequencies. With a two-dimensional round-shaped scatterers centre target model, the correlation coefficient of target echo signals in any type of diversity channel pair (DCP) is proved to be a function of the target size and the equivalent frequency interval. The theoretical correlation coefficient is verified by numerical experiments. The correlation coefficient of target echo signals often depends on the target location, which is shown for two typical DCP types. [ABSTRACT FROM AUTHOR]

For a non-coherent multiple-input multiple-output radar system, the minimum mean square error (MMSE) estimator and maximum a posteriori (MAP) estimator of the target location and velocity, considered random unknown parameters, are formulated and the corresponding posterior Cramér-Rao lower bound (PCRLB) is derived. Moreover, numerical solutions for the proposed MMSE estimator and the PCRLB are obtained by using Monte-Carlo methods because of the absence of closed-form solutions. The numerical results show that the mean square errors (MSEs) of the MMSE estimate and the MAP estimate converge to the corresponding PCRLB as the signal-to-noise ratio (SNR) increases when the number of transmit and receive antennas is sufficiently large. A linear approximation can be used to simplify the MMSE estimation. It is shown in some simulations that the linear approximation of the MMSE estimate is accurate at high SNR values and the SNR needed for accurate approximation can be reduced by increasing the number of antennas employed. [ABSTRACT FROM AUTHOR]

A modified matrix pencil method (MPM) inspired by interpolated arrays is proposed for the problem of parameter estimation in dispersive media obeying a frequency power law. A direct consequence of the arising dispersive signal model is that the Hankel prediction matrix can no longer be expressed using the Vandermonde decomposition, which hinders the direct application of all matrix-shifting techniques including the MPM. This is remedied by restoring the Vandermonde structure of the mode vectors via two different interpolation procedures. The first procedure is two dimensional, whereas the second one is one dimensional and iterative. The two versions of the interpolated algorithm are tested on simulated data representing radar acquisitions over a stratified dispersive medium, and their performance is assessed against the Cramér-Rao lower bound. The obtained results indicate that the iterative interpolation procedure affords the optimal performance of its two-dimensional counterpart at a reduced computational burden. [ABSTRACT FROM AUTHOR]

A novel monolithic CMOS radio frequency (RF) direct-down converter architecture is described, that comprises three miniature quadrature couplers (QCs), three miniature baluns and two sub-harmonic mixers (SHMs) for direct-down conversion. The SHMs in conjunction with the QCs and baluns are used to eliminate local oscillator (LO) self-mixing. The circuit was fabricated in a standard 0.18 µm CMOS process for 24 GHz applications. At an RF of 24 GHz and intermediate frequency (IF) of 100 MHz, the RF direct-down converter exhibits an amplitude mismatch of only 0.6 dB, a phase mismatch of only 3.53°, a voltage gain of 1.5 dB, and an third-order input intercept point (IIP3) of 6.5 dBm while dissipating 10.05 mW from a 1.5 V supply. In addition, excellent isolations were also achieved. The corresponding LO-to-IF, RF-to-IF, LO-to-RF and 2LO-to-RF isolations are 45.7, 46.5, 61.1 and 60 dB, respectively, at 24 GHz. The chip area was only 1.017×0.717 mm2, that is, 0.729 mm2, excluding the test pads. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) radars have attracted considerable attention for their ability to transmit multiple waveforms. These waveforms affect the range, Doppler and spatial performance. Recently, the concept of ambiguity function, which is an important mathematical tool for analysing and designing radar signals, has been extended to the MIMO radar case. In this study, the authors investigate the range and spatial properties of colocated MIMO radar based on range-spatial ambiguity function. Owing to spatial dependence of the matched filter output of MIMO radar, the spatial detection region is divided into multiple sections by spatial resolution. A new algorithm for designing orthogonal frequency-hopping waveforms according to the spatial section where the target may appear is proposed. This algorithm improves the peak sidelobe level of the matched filter output. [ABSTRACT FROM AUTHOR]

In wideband radar imaging, it is necessary to increase the target observation angle, that is, the imaging time to obtain high azimuth resolution. For wide-angle targets, however, migration through resolution cell will occur and the Doppler information of the scatterers will be time varying, which can lead to image defocusing in both the range and azimuth domain if the range-Doppler (RD) method is applied. Aimed at this problem, this study builds up the imaging model for steadily moving targets with a constant rotation axis. Then it compares the RD algorithm, the Keystone algorithm and the polar format algorithm with theoretical analysis and deduces the maximum observation angles that fit for these methods, respectively. Additionally, this study proposes a new algorithm for imaging of targets with large observation angles based on the complex inverse Radon transform. Instead of applying the Taylor's series approximation, this method strictly follows the signal model for scatterers with a wide observation angle and utilises curvilinear integral with phase information for image formation. Therefore it is valid in wide-angle scenarios. Finally, imaging results for both the simulated and measured data are given to analyse the performance of the available algorithms and to prove the validity of the proposed algorithm. [ABSTRACT FROM AUTHOR]

High-frequency surface wave radar (HFSWR) has been widely adopted as a useful remote-sensing tool for sea-state monitoring. There are limitations to the performance because of various unwanted clutters and interferences that contaminate radar signals. Among all types of unwanted signals, radio frequency interference (RFI) is dominant since the frequency bands 3-30 MHz, the operation range of HFSWR, are shared by many radio services. If RFI occupies the areas in the Doppler spectrum that are essential for the estimation of oceanographic parameters, for example, wind speed, current speed, wave height etc., it will significantly reduce the quality of the data. The characteristics of RFI in time, space and Doppler domains are analysed for sea-state monitoring, and a robust and general signal processing method consisting of image recognition, segmentation processing and subspace projection for cancellation of RFI is proposed. The effectiveness of this approach is validated using data obtained with the Pisces HF radar, which is a high-performance radar developed for long-range wave measurement, operating in the lower half of the HF band (5-10 MHz). [ABSTRACT FROM AUTHOR]

This study deals with the problem of Pareto-optimal waveform design in the presence of coloured Gaussian noise, under a similarity and an energy constraint. At the design stage, the authors, determine the optimal radar code according the following criterion: constrained maximisation of the detection performance and constrained minimisation of the Cramer-Rao lower bound (CRLB) on the Doppler estimation accuracy. This is tantamount to jointly maximising two quadratic forms under two quadratic constraints, so that the problem can be formulated in terms of a non-convex multi-objective optimisation problem. In order to solve it, the authors resort to the scalarisation technique, which reduces the vectorial problem into a scalar one using a Pareto weight defining the relative importance of the two objective functions. At the analysis stage, the authors assess the performance of the proposed waveform design scheme in terms of detection performance, region of achievable Doppler estimation accuracy and ambiguity function. In particular, the authors analyse the role of the Pareto weight in the optimisation process. [ABSTRACT FROM AUTHOR]

In this study, a geometric transition radar absorbing material loaded with a binary frequency selective surface (FSS) is presented. The FSS is designed to improve the absorber's reflectivity at low frequencies. A genetic algorithm (GA) was used to optimise the binary FSS pattern and its position within the absorber. The binary FSS loaded absorber was optimised for performance for both single- and dual-polarisation schemes and was subsequently evaluated against a previously published square conductive loop FSS loaded absorber. An image processing technique was utilised to assess the sensitivity of the FSS design to variations of small geometric features. [ABSTRACT FROM AUTHOR]

The coherent radar detection against a background of compound-Gaussian clutter with inverse gamma texture is studied and three detectors: One-step generalised likelihood ratio test (1S-GLRT), maximum a posteriori GLRT (MAP-GLRT) and two-step GLRT (2S-GLRT) are proposed. The detectors have the same structure with their test statistics and modified thresholds, respectively, related to the scale and the shape parameters of the texture, which can also be formulated in a matched filter (MF) form. Subsequently, the performance assessments are given by their probability of detection and probability of false alarm. The authors find that the probability of false alarm is dependent on the shape parameter, meaning the detectors have no CFAR property. When the shape parameter and the number of the integrated radar pulses satisfy certain condition, it has no relation with the shape parameter and then the detectors have CFAR property. Finally, simulation results show that: (i) 1S-GLRT and MAP-GLRT have the same performance for fixed probability of false alarm and 2S-GLRT bears slightly bad performance; (ii) the performance of 1S-GLRT is much closer to the adaptive coherence estimator (ACE) and is better than that of the Kelly GLRT and (iii) the 1S-GLRT is robust when parameter estimation errors exist. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Time-correlated clutter simulation based on the zero memory non-linearity transformation (ZMNL) and spherically invariant process (SIRP) suffers from spectrum expansion, and spatial-correlated clutter simulations may suffer from calculation complexity. To overcome these drawbacks, a new method of modelling and simulation of temporal-spatial-correlated clutter is proposed, based on the weighted norm in discrete complex linear space and a simple matrix transformation. Time-correlated clutter sequences with exact spectra can be generated by this algorithm through solving the minimum discrete weighted norm; whereas the spatial-correlated clutter can be generated by simple linear matrix transformations without complex calculations. It is shown that temporal-spatial-correlated clutter can be exactly and simply generated by the proposed method. Numerical simulation results show the feasibility and accuracy of this method. [ABSTRACT FROM AUTHOR]

This study discusses the fusion of radar frequency (RF) data and electro-optical (EO) data for tracking and characterisation of dismounts (i.e. humans). Each of these sensor modalities provides unique information about the location, structure and movement of a dismount. The person's location is tracked on the 2D ground plane using RF data for range measurements and EO data for angle measurements. Using this information, measurements are made on the structure and dynamic motion (gait) of the person. An imaging approach is used to create spatio-temporal activity maps along with a three-dimensional reconstruction of the dismount. [ABSTRACT FROM AUTHOR]

In high-resolution radars or at low gazing angles, the clutter is more satisfied in the compound-Gaussian model. Meanwhile, the polarisation diversity can be exploited to enhance the detection performance. Motivated by extending the detection problem of multiple-input multiple-output radar to such cases, this study mainly addresses the adaptive detectors design with an unknown covariance matrix based on Rao and Wald criterions. The two-step design strategy is adopted. Three estimation strategies of covariance with secondary data, such as sampled covariance matrix (SCM), normalised sampled covariance matrix (NSCM) and fixed point estimation (FPE) matrix, are introduced to make derived receivers fully adaptive. A thorough performance assessment is given by several numerical examples, the results of which show that Rao and Wald tests can provide good detection performance in even spikier clutter, and the polarimetric diversity can also be exploited to improve the detection performance. Meanwhile, the FPE strategy is more suitable to implement the adaptive detection algorithms, and the adaptive loss is completely acceptable in practical applications. [ABSTRACT FROM AUTHOR]

This study focuses on the narrow-band radar imaging for high-speed spinning targets. Based on the time–frequency characteristic of the echoed signal, a novel coherent spectrogram redistribution method, coherent single range Doppler interferometry (CSRDI), is proposed, which is capable of generating high-resolution imagery by applying a phase matched processing. Furthermore, the approach performs well at low signal-to-noise ratio. The spinning rate error is also taken into consideration and an estimation approach based on the focal entropy is proposed. The validity is confirmed by real data and numerical simulations. [ABSTRACT FROM AUTHOR]

One of the origins of error in the angle of arrival estimation of a signal is the response of the ground to the reflected waves from the target. In low-height target situations, this phenomenon can be so harrowing that it may result in much more error than thermal noise. In this article, two methods of fixed beam and double null are used as preliminary techniques to overcome the problem of low-altitude target angle estimation, and the optimum weights for beam-forming array radar are proposed. These beam-forming methods enable the radar to estimate the target angle precisely without the exact knowledge of the surface slope, whereas they are robust against diffuse and specular ground reflection components. [ABSTRACT FROM AUTHOR]

A littoral clutter modelling approach that derives three-dimensional refractivity profiles from mesoscale numerical weather prediction (MSNWP), applies them to parabolic equation (PE) propagation models, and combines them with empirical surface clutter reflectivity models to generate a more realistic model of surface clutter, is described. The MSNWP model is COAMPS®, coupled atmospheric mesoscale numerical prediction system. This study updates a paper for the IEEE Radar Conference in 2008: overwater discrete clutter, oil rigs, have been added to the model; new model comparisons with recorded data have been executed; and an evaporative duct model was appended below the refractivity profiles Burk et al. developed the approach presented here (i.e. COAMPS® provides atmospheric data for propagation models, which in turn provide data for clutter models). The current work advances this technology into the littorals. It has been tested over many cases of atmospheric conditions in several geographic areas. This synthesis of MSNWP and radar clutter models can provide clutter and propagation forecasts for military planners, retroactive prediction of propagation for clutter test data analysis and realistic models for radar system design and performance analysis. [ABSTRACT FROM AUTHOR]

The signal model of digital television terrestrial broadcasting (DTTB) is introduced and its ambiguity function is analysed here. In order to suppress the direct-path (and multipath) interference generated by single frequency network in DTTB-based passive radar, the corresponding spatial filtering methods are designed according to the feature of each channel. In the echo channel, the interference is suppressed by discarding the signal-subspace. The noise-subspace can be estimated from the power of the covariance matrix to avoid the eigen-decomposition and to eliminate the need to obtain the corresponding dimension. In the reference channel, the transmitting signal of a certain transmitter is regarded as the desired signal. The desired signal will be cancelled by conventional spatial filtering algorithms for the high signal-to-noise ratio case, which will also result in a distorted pattern and high side-lobes. To solve this problem, an improved general side-lobe canceller structure is proposed to realise the adaptive beamformer. To improve the robustness of the proposed methods and suppress the distributed clutter, the ‘broad null’ algorithm is combined with the beamformer. The simulation results show that the proposed methods are effective to suppress the interference in DTTB-based passive radar. [ABSTRACT FROM AUTHOR]

A high-resolution ultra-wideband (UWB) impulse radar has been developed in order to realise high-resolution object imaging in a ground-penetrating radar (GPR) for landmine detection. The UWB impulse radar is based on an electrical-optical hybrid pulse generation scheme such that a clean, short pulse train with small, short ringing can be generated. The generated UWB impulse train has a pulse duration of approximately 200 ps and a repetition rate of less than 1 GHz. Its estimated equivalent isotropically radiated power was well matched with a spectral mask for GPRs, as defined by the Federal Communications Commission of the USA. From an experimental demonstration, it was observed that the developed high-resolution UWB impulse radar was able to resolve a relative positional change of an object with a resolution of less than 10 mm, resulting in accurate imaging of a complex three-dimensional object. [ABSTRACT FROM AUTHOR]

Phased arrays have been required to operate over wide bandwidths and wide scan angle to support multifunction operation in both telecommunication and radar. In response to that need, this study firstly analyses the performance of the connected planar tapered slot antenna array and finds that the mutual coupling is essential and has good effect in wideband antenna array design. Then the authors design a wideband widescan planar tapered slot antenna array system with novel dual-parabola tapered slot antenna elements and feed network. This array can operate from 1.6 to 9 GHz and scan angle up to 45°. Both simulation and measurement results are shown to certificate the performance of the proposed antenna array. [ABSTRACT FROM AUTHOR]

Through statistical estimation by a non-parametric model, a fused polarimetric and resonant return from the radar target is modelled as a function of the target aspect angle. The outcome of this type of modelling is a set of non-parametric density estimates, which are then used to represent this target in a multi-dimensional probability space. These densities within this probability space can be well separated and therefore utilised to make decision rules to identify targets of interest. The return set to be modelled is the average power set associated with spectral bands centred on the target natural resonant frequencies. This return set is mapped into density set using a Gaussian kernel function; subsequently, the density set will be considered as the target radar feature set of interest. To decrease density overlapping between respective densities of different targets, a criterion based on the Bayesian error is employed; first, to bisect the aspect global range into smaller sectors, and second, to select discriminative features that can minimise the average probability of error between the targets respective features. The results show that two targets with similar resonant frequencies can be separated by the Bayesian error criterion based on the proposed features. A simple likelihood ratio test had more than 80% success down to 20 dB of signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) image formation implicitly assumes that the backscattered returns arise from stationary isotropic targets. When objects move during the SAR integration time, signal anomalies appear that distort, displace and smear moving targets in the image. Although these anomalies degrade the image, they provide the information that allows analysis of the underlying target motion. Joint time–frequency analysis (JTFA) exploits these signal anomalies to estimate the motion of typical point targets. However, the weak, transient returns from water surface scatterers complicate standard JTFA estimates of water surface speeds. A time–frequency representation is applied based on the Capon's spectral estimation technique that allows joint analysis of multiple azimuth lines, thereby increasing the signal-to-clutter ratio of weak scatterers. The authors compare the time–frequency estimate, employing single-phase-centre SAR data, to along-track interferometric SAR estimates of the same flow and show that both the methods produce comparable results. The authors derive the JTFA equations and estimate water surface speed for data collected at a specific imaging geometry. This study highlights the feasibility of using a single-phase-centre SAR system to determine the motion of slow moving distributed targets representative of water flow. [ABSTRACT FROM AUTHOR]