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Radar, Sonar & Navigation, IET

Issue 1 • Date January 2011

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Displaying Results 1 - 11 of 11
  • Timing accuracy of self-encoded spread spectrum navigation with communication

    Publication Year: 2011 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    The authors present the timing accuracy of self-encoded spread spectrum (SESS) in navigation. SESS eliminates the need for traditional transmit and receive pseudo noise code generators. As the term implies, the spreading code is instead obtained from the random digital information source itself. SESS was shown to improve system performance significantly in fading channels. In this study, the authors investigate the timing accuracy of SESS in comparison to m-sequence and Gold code. SESS can be an excellent candidate for navigation with communication. View full abstract»

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  • Tropospheric refractivity profiling based on refractivity profile model using single ground-based global positioning system

    Publication Year: 2011 , Page(s): 7 - 11
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (305 KB)  

    A retrieval method is developed to obtain atmospheric refractivity profiles based upon the zenith delay of single ground-based global positioning system receivers. It is found that the key parameter in exponential wet refractivity model is the equivalent height of wet term Hw, while the errors between the integral of the wet terms of refractivity and the true values are single-peaked functions of Hw. Therefore the golden section method is utilised to retrieve Hw; moreover, the refractivity profiles are obtained. Meanwhile, the classic Hopfield model is used as the hydrostatic refractivity model. The experimental results with radiosonde data in Shanghai, China, and simulations using data from Qingdao, China, show that this method has demonstrated a good agreement with radiosonde profiles. View full abstract»

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  • Analysing and compensating the effects of range and Doppler frequency migrations in linear frequency modulation pulse compression radar

    Publication Year: 2011 , Page(s): 12 - 22
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1002 KB)  

    The pulse compression and Doppler processing (PCDP) method has been extensively used to detect low-speed and uniform-speed targets in linear frequency modulation (LFM) pulse compression radar. However, the PCDP method is affected by range migration (RM) and Doppler frequency migration (DFM) when detecting high-speed and accelerating targets. In this paper, the authors analyse and quantify these effects, and obtain the relationships of the optimal number of pulses and the threshold number of pulses with RM and DFM. It shows that when the number of pulses equals its optimal value, the maximum output signal-to-noise ratio can be obtained; when the number of pulses is greater than its threshold value, the migrations should be compensated. Then the authors propose a method based on the scaling processing and the fractional Fourier transform to remove the two migrations. In the end, the authors give a target detection experiment to show that the proposed method can effectively compensate these migrations. View full abstract»

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  • Adaptive subspace detector for multi-input multi-output radar in the presence of steering vector mismatch

    Publication Year: 2011 , Page(s): 23 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (633 KB)  

    This study studies the problem of adaptive target detection by multi-input multi-output (MIMO) radar with multiple antennas at each of the receiver sites. MIMO radar has been postulated to have a number of advantages over its monostatic counterpart. However, many previous publications have not necessarily made valid assumptions in assessing performance potential. Here, the authors consider the issue of the overall MIMO radar system steering vector which should be aligned with the desired pointing direction. However, misalignment can occur because of calibration errors, receiver channel imperfections and beam pointing errors. To account for this misalignment, the steering vector is assumed to belong to a known linear subspace. At the design stage, the authors resort to a generalised likelihood ratio principle and Rao test criterion. Subsequently, MIMO versions of the subspace generalised likelihood ratio test (MIMO-SGLRT), the subspace adaptive beam-former orthogonal rejection test (MIMO-SABORT) and the subspace Rao (MIMO-SRao) detector are developed to improve the robustness of MIMO radar detection performance for the case of steering vector mismatch. The constant false alarm rate properties of the three detectors are demonstrated. Finally, the performance of the MIMO-SGLRT, MIMO-SABORT and MIMO-SRao detectors in both the matched and mismatched steering vector cases are numerically evaluated. The results show the robustness of the proposed detectors to steering vector mismatch. View full abstract»

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  • Designing single/multiple sparse frequency waveforms with sidelobe constraint

    Publication Year: 2011 , Page(s): 32 - 38
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (666 KB)  

    Sparse frequency waveform with narrow stopbands sparsely distributed over a wide spectrum band is preferred for many radar and communication systems operating in a highly congested spectrum environment. In this paper, a new method for designing sparse frequency waveform with low range side lobes are proposed. The basic idea is to achieve waveform total performance improvement by minimising a new effective penalty function based on both requirements for the power spectrum density and the range side lobe through an iterative algorithm. The proposed approach is efficient in computation and flexible in designing sparse frequency waveform. Several design examples are also presented to show the validity of the proposed method. An extension to design multiple waveforms for multiple-input multiple-output radar is also presented. View full abstract»

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  • Interferometric inverse synthetic aperture radar experiment using an interferometric linear frequency modulated continuous wave millimetre-wave radar

    Publication Year: 2011 , Page(s): 39 - 47
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (869 KB)  

    An interferometric linear frequency modulated continuous wave (LFMCW) millimetre-wave radar is presented, along with the results of an experiment conducted to study the feasibility of using it in a future millimetre-wave interferometric inverse synthetic aperture radar (InISAR) system. First, a description of the radar is given. Then, the signal processing chain is described, with special attention to the phase unwrapping technique. The interferometric phase is obtained by unwrapping the prominent target's phase in each antenna using a sliding frame processing technique. Cell migration issues in this method are also addressed. Simulations were carried out to illustrate and assess the processing chain and to show the effects of multipath echoes on the height measurement. In the real experiment, the range, speed and height of a moving target were tracked over consecutive inverse synthetic aperture radar (ISAR) image frames, verifying the performance of the whole system. View full abstract»

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  • Target detection in high-resolution sea clutter via block-adaptive clutter suppression

    Publication Year: 2011 , Page(s): 48 - 57
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (593 KB)  

    Attentions have been focused on the moving target detection in a high-resolution sea clutter. This study commences with a proposal of median-based estimator to estimate the power spectrum of high-resolution sea clutter by the time series observed in adjacent range cells and time intervals. The estimator provides a robust estimation when just a few aberrant time series happen in observation. Based on the estimator, a block-adaptive clutter suppression filter (BACSF) is designed to suppress the clutter prior to the pulse integration. Then, the residual clutter, the output of the BACSF, is modelled as spherically invariant random vector. Upon applying an adaptive normalised matched filter (ANMF) to the residual clutter, a residual clutter's ANMF detector is derived. Moreover, in high-resolution radar background, considering that the approximately stationary intervals of sea clutter and residual clutter are much shorter than the coherent processing interval, another heuristic block-ANMF detector is proposed. It can integrate more pulses and can achieve better performance than the ANMF detector does. This study concludes with the experiments of simulated target against the real sea clutter. The experimental results demonstrate that, when target's Doppler frequency is beyond strong clutter region, the ANMF detector and block-ANMF detector perform better in the residual clutter than in the clutter. View full abstract»

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  • Combining pyramid representation and AdaBoost for urban scene classification using high-resolution synthetic aperture radar images

    Publication Year: 2011 , Page(s): 58 - 64
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    This study presents a new algorithm called pyramid representation (PR)-AdaBoost, which combines PR and AdaBoost for urban area classification using high-resolution synthetic aperture radar (SAR) images. PR is used to hierarchically represent local feature sets and AdaBoost is used to choose proper features from the PR vector and effectively discriminate categories. The authors evaluate the proposed algorithm on a data set consisting of high-resolution SAR images of five different categories of scene and on a real TerraSAR-X image. The experimental results have shown that PR-AdaBoost can achieve higher classification accuracy than AdaBoost based on global representation or local representation such as bag-of-features. It also outperforms classical classifiers such as nearest neighbour, boosted distance and support vector machine based on the same representation. View full abstract»

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  • Track-before-detect procedures for low pulse repetition frequency surveillance radars

    Publication Year: 2011 , Page(s): 65 - 73
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (595 KB)  

    In this study, the authors present a dynamic programming (DP)-based tracking-before-detect (DP TBD) procedure with reference to a low pulse repetition frequency (PRF) surveillance radar framework. In order to avoid non-linear transformation and meanwhile exploit the ambiguous Doppler information, which is eliminated in most of the literature, the authors model the target dynamics in the measurement coordinates defined by range and apparent Doppler. The target state evolutions in the range-apparent Doppler domain are considered as a hybrid system with the ambiguous number deemed as mode variable. Ambiguity number (or mode) transitions are modelled as state dependent. The authors present a DP TBD method for joint maximum a posteriori (MAP) estimation of the target trajectory in the range-apparent Doppler maps and the corresponding ambiguity sequence, both assumptions of known and unknown nuisance parameters (target power and noise variance) are considered. The detection and tracking performance of the proposed procedure are investigated under several system settings. The effect of the prior uncertainty of the nuisance parameters on the performance is also studied. View full abstract»

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  • Enhanced monopulse tracking radar using optimum fractional Fourier transform

    Publication Year: 2011 , Page(s): 74 - 82
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (956 KB)  

    Conventional monopulse radar processors are used to track a target that appears in the look direction beam width. The distortion produced when additional targets appear in the look direction beam width can cause severe erroneous outcomes from the monopulse processor. This leads to errors in the target tracking angles that may cause target mistracking. A new signal processing algorithm is presented in this study which offers a solution to this problem. The technique is based on the use of optimal fractional Fourier transform (FrFT) filtering. The relative performance of the new filtering method over traditional-based methods is assessed using standard deviation angle estimation error (STDAE) for a range of simulated environments. The proposed system configuration succeeds in significantly cancelling additional target signals appearing in the look direction beam width even if these targets have the same Doppler frequency. View full abstract»

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  • Target localisation for distributed multiple-input multiple-output radar and its performance analysis

    Publication Year: 2011 , Page(s): 83 - 91
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    This study considers the problem of target localisation with a coherent processing technique for distributed multiple-input multiple-output radar systems. To enable the coherent processing technique, dual-frequency transmitters are employed to eliminate the stochastic phases of complex fading coefficients, which are caused by target angular fluctuations. And then a two-step procedure is introduced to accomplish the target localisation. In the first step, the amplitudes of the complex fading coefficients are estimated. In the second step, the target position is obtained using the MUSIC algorithm with modified target steering vector. With the amplitudes estimated, the target localisation performance is improved. The Cramér-Rao bound (CRB) for target localisation accuracy is derived with precise knowledge of radar positions. The CRB is shown to be inversely proportional to the frequency difference between the transmitted signals. With the radar positions uncertainty, the average asymptotic performance of the proposed method is given. Finally, numerical examples are given to validate the proposed method and the theoretical analyses. View full abstract»

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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.

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