Online ISSN
1751-8792
Print ISSN
1751-8784
IET Radar, Sonar & Navigation
Volume 2, Issue 1, February 2008
Volumes & issues:
Volume 2, Issue 1
February 2008
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- Author(s): W.Q. Wang ; C.B. Ding ; X.D. Liang
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 1 –11
- DOI: 10.1049/iet-rsn:20060097
- Type: Article
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Bistatic synthetic aperture radar (BiSAR) operates with distinct transmitter and receiver that are mounted on separate platforms. Such a spatial separation results in problems and special requirements that are either not encountered or encountered in less serious form for monostatic SAR. Directly associated with these requirements one has to solve the problems of highly accurate time and phase synchronisations. The impact of oscillator frequency instability on BiSAR is analysed, and a time and phase synchronisation technique via direct-path signal is proposed. With the proposed technique, the direct-path signal of transmitter is received with one appropriative antenna and divided into two channels, one is passed through an envelope detector and used to synchronise the sampling clock, and the other is down-converted and used to compensate the phase synchronisation errors. Finally, the residual time synchronisation error is compensated with range alignment, and the residual phase synchronisation error is compensated with global positioning system/inertial navigation system/inertial measurement units (GPS/INS/IMU) information; then the focusing of BiSAR image can be achieved. Based on this technique, a prototype linearly frequency modulated BiSAR synchronisation system is constructed.The effectiveness of this proposed technique is verified with simulation data. - Author(s): L.M. Ehrman and A.D. Lanterman
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 12 –16
- DOI: 10.1049/iet-rsn:20070025
- Type: Article
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A coordinated flight model for estimating the orientation of an aircraft under track from velocity measurements into an extended Kalman filter (EKF) framework is placed here. In doing so, it makes two contributions. First, the EKF provides a rigorous framework for addressing this problem, blending modelling error and measurement error. Second, the EKF supplements the estimated orientation with a measure of the uncertainty in that estimate. Such estimates of uncertainty are crucial in a number of applications, including using the orientation estimates to approximate the radar cross section of the aircraft under track, in an attempt to identify targets. The EKF's performance is demonstrated using both a straight-and-level manoeuvre and a complicated manoeuvre recorded on-board a manoeuvring F-15. In both cases, the state estimates of the EKF are similar to the results obtained from a coordinated flight model. The true orientations almost always fall within one standard deviation of the estimates, as determined by the estimated covariance. - Author(s): A. De Maio ; L. Landi ; A. Farina
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 17 –24
- DOI: 10.1049/iet-rsn:20060077
- Type: Article
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The problem of adaptive radar detection in the presence of near-field and mutual coupling effects – two phenomena which may significantly affect the radar performance – is considered. To this end, the generalised likelihood ratio test criterion is used (both one-step and two-step) and adaptive decision rules capable of operating in realistic scenarios are devised, where the far-field hypothesis can be no longer met and the mutual coupling is present. At the analysis stage, the performance of the proposed detectors is evaluated through Montecarlo simulations. The results show that appreciable performance improvements can be obtained if near-field and mutual coupling effects are properly accounted for at the design stage. - Author(s): J.M. Muñoz-Ferreras and F. Pérez-Martínez
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 25 –34
- DOI: 10.1049/iet-rsn:20060170
- Type: Article
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In the current scenario of high-range resolution radars, the rotational motion of the target usually generates migration through resolution cells (MTRC) in the inverse synthetic aperture radar (ISAR) images. A technique to correct the MTRC in the case of uniform rotation rate is proposed. An estimation of the rotation vector of the non-cooperative targets is not required. The approach compensates the rotational motion in two steps: the slant-range rotation compensation (SRRC) and the cross-range rotation compensation (CRRC). CRRC is based on an extension of phase difference (PD) and on a robust method to delete outliers. The technique is verified both with simulated and live data from a millimetre-wave linear frequency-modulated continuous wave radar. A comparison with a minimum entropy-based technique is also made. - Author(s): J.C. Nieto-Borge ; K. Hessner ; P. Jarabo-Amores ; D. de la Mata-Moya
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 35 –41
- DOI: 10.1049/iet-rsn:20070027
- Type: Article
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This work analyses the structure of the different contributions to the image spectrum derived by the three-dimensional Fourier decomposition of sea clutter time series measured by ordinary X-band marine radars. The goal of this investigation is to derive a method to estimate the significant wave height of the ocean wave fields imaged by the radar. The proposed method is an extension of a technique developed for the analysis of ocean wave fields by using synthetic aperture radar systems. The basic idea behind this method is that the significant wave height is linearly dependent on the square root of the signal-to-noise ratio, where the signal is assumed as the radar analysis estimation of the wave spectral energy and the noise is computed as the energy due to the sea surface roughness, which is closely related to the speckle of the radar image. The proposed method to estimate wave heights is validated using data sets of sea clutter images measured by a marine radar and significant wave heights derived from measurements taken by a buoy used as reference sensor. - Author(s): Y. Norouzi ; F. Gini ; M.M. Nayebi
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 42 –50
- DOI: 10.1049/iet-rsn:20060087
- Type: Article
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Binary integrators are an important part of the receiver in many operating radar systems. The optimisation of a binary integrator is not a simple task, because it requires the solution of a (k×n)-dimensional nonlinear optimisation problem, where n is the number of integrated bits (or the number of sensors in a distributed radar or sensor network) and k is the number of the design parameters of the single-pulse detector. An algorithm that converts the multi-dimensional optimisation problem into a one-dimensional problem, so reducing considerably the computational complexity, is developed. This reduction in computational complexity makes the real-time optimisation possible and practical, so it is very helpful for mobile sites in which the optimisation should be performed continually. The proposed algorithm can be applied when either the ‘AND’ or the ‘OR’ integration rule is adopted. The results are illustrated by means of two study cases. In the first case, the binary integrator of a constant false alarm rate radar detector is optimised; in the second one a decentralised detection system composed by n similar sensors is considered and the decision rules are jointly optimised according to the Neyman–Pearson criterion. - Author(s): D.J. Allerton and H. Jia
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 51 –62
- DOI: 10.1049/iet-rsn:20060159
- Type: Article
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New approaches to the development of data fusion algorithms for inertial network systems are described. The aim of this development is to increase the accuracy of estimates of inertial state vectors in all the network nodes, including the navigation states, and also to improve the fault tolerance of inertial network systems. An analysis of distributed inertial sensing models is presented and new distributed data fusion algorithms are developed for inertial network systems. The distributed data fusion algorithm comprises two steps: inertial measurement fusion and state fusion. The inertial measurement fusion allows each node to assimilate all the inertial measurements from an inertial network system, which can improve the performance of inertial sensor failure detection and isolation algorithms by providing more information. The state fusion further increases the accuracy and enhances the integrity of the local inertial states and navigation state estimates. The simulation results show that the two-step fusion procedure overcomes the disadvantages of traditional inertial sensor alignment procedures. The slave inertial nodes can be accurately aligned to the master node. - Author(s): K.J. Sohn ; H. Li ; B. Himed
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 63 –70
- DOI: 10.1049/iet-rsn:20070075
- Type: Article
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The problem of detecting a multichannel signal in spatially and temporally coloured disturbances is considered. The parametric Rao and parametric generalised likelihood ratio test detectors, recently developed by modelling the disturbance as a multichannel autoregressive (AR) process, have been shown to perform well with limited or even no range training data. These parametric detectors, however, assume that the model order of the multichannel AR process is known a priori to the detector. In practice, the model order has to be estimated by some model order selection technique. Meanwhile, a standard non-recursive implementation of the parametric detectors is computationally intensive since the unknown parameters have to be estimated for all possible model orders before the best one is identified. To address these issues, herein the joint model order selection, parameter estimation and target detection are considered. We present recursive versions of the aforementioned parametric detectors by integrating the multichannel Levinson algorithm, which is employed for recursive and computationally efficient parameter estimation, with a generalised Akaike Information Criterion for model order selection. Numerical results show that the proposed recursive parametric detectors, assuming no knowledge of the model order, yield a detection performance nearly identical to that of their non-recursive counterparts at significantly reduced complexity. - Author(s): R. Tao ; W.-Q. Zhang ; E.-Q. Chen
- Source: IET Radar, Sonar & Navigation, Volume 2, Issue 1, p. 71 –77
- DOI: 10.1049/iet-rsn:20060014
- Type: Article
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The focus of this research is to provide a fast and precise method for joint time delay and Doppler shift estimation. The main procedure is divided into two stages. In the first stage, the pre-weighted Zoom fast Fourier transform and quadratic surface fitting methods are used for fast computing the ambiguity function and the for coarse estimation, respectively. In the second stage, the values near the coarse estimates are calculated and quadratic surface fitting method is used again for fine estimation. The two-stage method reduces the computational load without losing the precision. Simulation and experimental results are used to demonstrate the effectiveness of the proposed method.
Time and phase synchronisation via direct-path signal for bistatic synthetic aperture radar systems
Extended Kalman filter for estimating aircraft orientation from velocity measurements
Adaptive radar detection in the presence of mutual coupling and near-field effects
Uniform rotational motion compensation for inverse synthetic aperture radar with non-cooperative targets
Signal-to-noise ratio analysis to estimate ocean wave heights from X-band marine radar image time series
Optimisation of binary integrators for decentralised detection
Distributed data fusion algorithms for inertial network systems
Recursive parametric tests for multichannel adaptive signal detection
Two-stage method for joint time delay and Doppler shift estimation
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