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A 19‐GHz low‐phase‐noise PLL‐frequency synthesizer is presented in this letter that is intended to be used in a K‐band FMCW radar which requires strict phase noise for detecting a small unmanned aerial vehicle. The 17.9 to 19.5‐GHz PLL includes a Darlington cross‐coupled capacitive‐degeneration VCO which presents higher maximum attainable oscillation frequency (ƒtrans) and larger negative transconductance (gm), thus resulting in low phase noise. Manufactured using the SiGe BiCMOS process, the K‐band synthesizer demonstrates −114 dBc/Hz at 1 MHz offset and −138 dBc/Hz at 10 MHz offset from 19.456 GHz locking carrier frequency. [ABSTRACT FROM AUTHOR]

Inspection of the railway tracks requires relying on a precise positioning system that accurately determines the location of potential failures and deficiencies. Therefore, measuring the speed and precise location of rail vehicles is essential. Many methods and approaches have been proposed, but most of them lack several conditions that do not allow them to be optimal for this task. In this paper, the authors present a novel method for measuring the speed of a train by means of the time correlation approach, by using 2‐mm wave radar sensors. Additionally, it is also an accurate positioning system because the authors prove that the track has a unique profile, sufficiently characteristic and stable over time, that serves as a distinctive signature, which can be used to locate the vehicle at any point on that track. As a result, this new methodology, combined with a laser profilometer device, can be used as an effective inspection system for cracks or deficiencies in the rails, sleepers, fastenings, bolts etc., locating them precisely on the railway track. [ABSTRACT FROM AUTHOR]

This article presents a deep neural network‐based constant false alarm rate (NNB‐CFAR) detector for simulated high‐frequency surface wave radar (HFSWR) data. A deep neural network is trained to identify fluctuation parameters of each cell of a range‐Doppler power spectrum based on the patterns present in the neighbouring cells. The estimated parameters are then used for calculating a detection threshold with a user‐specified probability of false alarm. To train the network, a realistic model of HFSWR echoes is used for generating a large labelled range‐Doppler image dataset, including many possible clutter scenarios and interfering target echoes. Several CFAR windows are extracted from the training range‐Doppler dataset and used as training data. The neural network is trained to replicate the output of a maximum likelihood estimator based on the reference cells of the CFAR window. The NNB‐CFAR algorithm was then compared to traditional CFAR algorithms by identifying targets in the second set of simulated range‐Doppler images. The probability of detection was also experimentally measured in the context of HFSWR for all algorithms. Results show that the technique can significantly improve detection rates amid strong clutter. [ABSTRACT FROM AUTHOR]

In the urban environment, the radar is easily affected by multipath (MP) returns. The problem of detecting point‐like targets in the urban environment with the existence of resolvable MP returns under the background of heterogeneous clutter is addressed. Two adaptive detectors have been devised with a combination of prior information on the environment and echoes of target. The detectors can use the MP echoes in all MP prediction range cells for detection or in some available paths for signal detection by the available path selection algorithm that eliminates the weak signal propagation paths. Remarkably, the proposed decision schemes exhibit the desirable constant false alarm rate property with respect to the unknown parameters of the heterogeneous interference. The performance assessment, conducted on simulated data in terms of detection probability also in comparison with conventional solutions, highlights the effectiveness of the MP exploitation, while the MP signal is strong and shows the detection performance enhancement potential. [ABSTRACT FROM AUTHOR]

In order to improve the recognition accuracy of construction machinery and equipment and materials in low contrast scenes, a construction machinery material recognition algorithm based on multisource sensor information fusion is proposed. In the paper, the millimeter wave radar is fused with the camera considering its strong penetration ability in rainy and foggy days and dim environments. Firstly, the spatial coordinates of radar and camera are unified by establishing a spatial fusion model of millimeter wave and camera; then the target acquired by millimeter wave is projected onto the image and the detection frame intersection and ratio model is used to generate the region of interest of the camera; finally, the improved YOLOv2 algorithm is used to identify the region of interest, and in the improved idea, the low‐level information is first connected with the high‐level information in multilayer depth. At the same time, a multiscale feature pyramid network structure is used to achieve recognition of objects of different scales. This model effectively reduces interference from other feature categories while improving the recognition efficiency of the system. The algorithm can effectively improve the recognition accuracy of mechanical materials in low‐contrast scenes, as demonstrated by the validation of different scenes. [ABSTRACT FROM AUTHOR]

This study investigates the use of adaptive radar waveforms in performing a multi‐task operation involving the tracking and classification of a single target. The work applies a previously reported hierarchical fully adaptive radar framework and considers a situation in which the target tracking function is performed using a transmit waveform having adaptive pulse repetition frequency, pulse width, bandwidth, and coherent processing interval parameters, while the classification function can be performed using only a fixed radar waveform. Two alternate strategies for selecting the next waveform are then described. The first strategy is focussed on maintaining fixed measurement performance goals in terms of target range and velocity and classification entropy, while the second approach varies these performance goals depending on the target state. Both approaches are examined for simulated datasets at W‐band representing a moving human target, as well as for laboratory measurements of this scenario. The results for both simulation and experiment show the benefits of including adaptive waveforms in performing multiple radar tasks. [ABSTRACT FROM AUTHOR]

This study focusses on the target detection problem in the distributed multiple‐input multiple‐output (MIMO) radar. The observation environment is assumed to be partially homogeneous in one transmitter‐receiver path and simultaneously non‐homogeneous for different paths. By characterising the disturbance signals with a series of auto‐regressive (AR) processes, two parametric detectors based on the Wald test are developed. The first one utilises an iterative scheme to estimate the unknown parameters that were involved in the derivation, and the second one obtains these estimations sequentially. One of the most attractive features of the two distributed MIMO radar detectors is that they can be used in the presence/absence of the training data. More specifically, they can take advantage of the training data to boost the detection performances effectively even if the training data are very limited. The simulation results of several scenarios demonstrate the remarkable detection performances of authors' proposed methods compared with that of the competitors. Furthermore, the amplitude estimation performances of the two detectors are evaluated via the corresponding Cramér–Rao bound (CRB). [ABSTRACT FROM AUTHOR]

To minimise the noise interference in the radar received echoes and optimise the detection issue for a wideband radar system, a novel wideband radar track‐before‐detect detector via Wiener Filter is proposed. The Wiener Filter can effectively remove the noise mixed in the echoes and make the filtered signal consistent with the original signal. After applying maximum likelihood estimation to the echoes, the authors can reconstruct the desired signal required for Wiener filtering by extracting the range information of each scatterer. Then Wiener Filtering is performed on the echo containing noise with the desired signal to complete the denoising. Subsequently, we exploit the correlation between the adjacent echoes for detection. The effectiveness of the detector can be verified by the numerical simulation results of synthetic and real radar data. The proposed detector is superior to the waveform contrast detector, inter‐period correlation processor and modified correlation matrix detector. [ABSTRACT FROM AUTHOR]

Resource allocation is one of the key problems in radar network. A modified particle swarm optimisation (PSO) algorithm is presented here to improve the performance of resource allocation in radar network with large baseline, where multiple tasks with multiple parameters were considered. First, the resource allocation mathematic model for radar network with large baseline was established. Second, based on modified PSO, the resource allocation algorithm is presented and it can simultaneously deal with both discrete and continuous variables. Finally, the simulation experiment is presented to verify the proposed algorithm. The simulation result suggested that the proposed algorithm is feasible and can satisfy the requirement of resource allocation in the radar network. [ABSTRACT FROM AUTHOR]

A joint target detection and tracking method based on plot-track quality evaluation (PTQE-D&T) is proposed here. The presented method consists of three consecutive steps. First, a set of candidate plots is extracted from the Detector and Plot-Extractor, where the plot quality is calculated simultaneously based on multi-dimensional echoes constituting the plot. Then, a track-before-detect (TBD) processor based on dynamic programming (DP) is utilised to jointly elaborate the observations from multiple scans and outputs potential tracks to be confirmed. Finally, a confirmation strategy is introduced via plot-track quality evaluation. Experimental results are provided to demonstrate the effectiveness of the proposed method, where two data sets collected from a ground-based surface-search radar and a ship borne 3D radar are used. Moreover, the proposed PTQE-D&T structure is totally consistent with conventional radar data processing architecture, meaning that it is promising in engineering applications. [ABSTRACT FROM AUTHOR]

Synchronisation of radar systems can be used to suppress interference and enable communication between radars. In this paper, a generalised Kuramoto model is proposed, which can be used to synchronise pulse repetition frequencies of two radars over‐the‐air. The generalised approach allows the adjustment of a sampling factor which influences the convergence of the two pulse repetition frequencies. Furthermore, sampling criteria are derived, which can be used to estimate whether convergence occurs. Finally, it is shown by means of simulation that the model together with the criteria allows to reliably predict convergence and to perform synchronisation. [ABSTRACT FROM AUTHOR]

Pulse-agile radar systems are becoming more prevalent as the demand for adaptive and cognitive systems increases. This focus is motivated by the need for interference avoidance and spectrum sharing. Pulse agility within a coherent processing interval (CPI) or intra-CPI adaption has been shown to cause distortion, which will negatively impact the radar’s performance. This problem can be framed in the context of image processing such that an ideal range–Doppler image is corrupted by some point spread function. Deconvolution is then applied to remove this distortion and improve radar performance while maintaining the ability to use computationally efficient fast Fourier transform-based processing. [ABSTRACT FROM AUTHOR]

In this study, the design and analysis of a seven-port radar duplexer for tracking a target in X-band operation are presented. The S-parameters of the structure are calculated and compared with experimental results. The simulations and experimental results are in good agreement. This device enables radars to calculate the horizontal difference, vertical difference, and sum of four beams of a monopulse antenna based on amplitude discriminator. Three magic-Ts and one Tjunction are used, four input ports are connected to a monopulse antenna and three other ports are output ports. The output data give three equations between input signals that allow the radar to track a target. Results show that the S-parameters of this device are affected by magic-Ts and the T-junction structure, and an optimum structure for the magic-Ts and T-junction is proposed. A comprehensive study has been carried out for determination and comparison of properties of the structure in theory, simulation, and experimental results. This device is useful in radar tracking systems. [ABSTRACT FROM AUTHOR]

Nyquist folding receiver (NYFR) can realize the wideband receiving with a small amount of equipment. As a tradeoff between the amount of equipment and the complexity of the signal processing, the NYFR output is usually a hybrid modulated signal. Therefore, it is necessary to investigate the parameter estimation method of the signal intercepted by the NYFR. Binary phase shift keying (BPSK) signal is a typical low probability of intercept radar signal and the authors focus on the parameter estimation of the BPSK radar signal intercepted by the NYFR. Firstly, matching component function is proposed to obtain Nyquist zone (NZ) index. Then, the Hankel-singular value decomposition (SVD) method is introduced to estimate the code rate of the BPSK signal. The efficacy of the Hankel-SVD method is proved in a mathematical way. Several numerical simulations demonstrate the merits of the proposed approach and finally, a brief investigation for case of the multiple BPSK signals intercepted by the NYFR is given. For NZ index estimation, the computational complexity of the matching component function is low and it has no need to use squaring process. In addition, the code rate estimation using the Hankel-SVD method is more accurate compared with the wavelet transform. [ABSTRACT FROM AUTHOR]

Classical stretch processing (SP) obtains high range resolution by compressing large bandwidth signals with narrowband receivers using lower rate analogue-to-digital converters. SP achieves the resolution of the large bandwidth signal by focusing into a limited range window, and by deramping in the analogue domain. SP offers moderate data rate for signal processing for high bandwidth waveforms. Furthermore, if the scene in the examined window is sparse, compressive sensing (CS)-based techniques have the potential to further decrease the required number of measurements. However, CS-based reconstructions are highly affected by model mismatches such as targets that are off-the-grid. This study proposes a sparsitybased iterative parameter perturbation technique for SP that is robust to targets off-the-grid in range or Doppler. The error between reconstructed and actual scenes is measured using Earth mover's distance metric. Performance analyses of the proposed technique are compared with classical CS and SP techniques in terms of data rate, resolution and signal-to-noise ratio. It is shown through simulations that the proposed technique offers robust and high-resolution reconstructions for the same data rate compared with both classical SP- and CS-based techniques. [ABSTRACT FROM AUTHOR]

Performance bounds on range resolution and range sidelobe level are built for waveforms with spectral notches. In this study, the authors use the integrated mainlobe energy (IME) and integrated sidelobe energy (ISE) of the autocorrelation function to assess the performance of range resolution and range sidelobe level, respectively. By considering the minimisation of the weighted sum of IME and ISE under given spectral constraints, they derive the optimal power spectrum density condition and subsequently calculate the best achievable IME and ISE. With this study, the radar system can (i) analyse the trade-off relationship between range resolution and range sidelobe level and thus better balance them in designing the transmit waveform; (ii) assess the fitness of potential working bands and thus select the best one to use. [ABSTRACT FROM AUTHOR]

This study investigates the effects of antenna rotation on range, radial velocity, and azimuth estimation during coherent integration in linear frequency-modulated continuous wave (LFMCW) radars. When antenna scans during the coherent integration time, theoretical analysis indicates that the angle sensing with the traditional sum-difference amplitude-comparison (SDAC) monopulse method and the range, radial velocity estimation with interpolation method are different from that in staring mode. Simulation demonstrates that the estimation performance is heavily impaired by the antenna rotation. In this study, a generalised mathematical model of coherent integration for LFMCW radar is established. Furthermore, a high-precision estimation method, which consists of generalised SDAC monopulse method, radial velocity estimator with modified interpolation curves, and range estimator refined by Doppler frequency, is proposed. A complete signal-processing scheme is proposed for the accurate estimation of the target parameter in mechanical scanning LFMCW radar. A sub-optimal method is provided for practical implementation. Experimental and simulation results show that the proposed method achieves high accuracy and robustness. [ABSTRACT FROM AUTHOR]

In high-resolution radar systems, stretch processing technique is generally used to process the returned signals of a range-spread target. Consequently, this results in mixer outputs that consist of several linear frequency modulation components with a small frequency rate (FR). The authors define an FR function to transform a signal from the time domain into the FR domain and discuss the FR range of a discrete signal. Then an interesting phenomenon is found in the FR domain, that is, the mixer output is concentrated in a low FR region, while the Gaussian noise spreads over the entire FR region. Therefore, a range-spread target detector has been proposed that regards the integration of the values in a vicinity of zero FR as the test statistic. This detector uses a single mixer output and thus has the ability to detect the target with a high velocity. Finally, the proposed detector is evaluated by recorded radar data. Experimental results show that the proposed detector outperforms the detectors using the high-resolution range profile. [ABSTRACT FROM AUTHOR]

The adaptive integral method (AIM) in conjunction with the low-rank compression method is developed to calculate the monostatic radar cross-section (RCS) of arbitrarily shaped three-dimensional perfectly electric conducting objects. For backscattering problems, the excitation matrix is usually highly rank-deficient and can be compressed via low-rank techniques without explicitly assembling the original matrix beforehand. Therefore, only the matrix equations corresponding to the linearly independent excitation vectors need to be solved, whose number is much less than that of incident angles. As a result, fast monostatic RCS calculation over a widely angular range can be achieved. To facilitate the analysis of electrical large problems, the AIM is applied to accelerate the matrix-vector product and reduce the memory usage. Numerical examples are presented to demonstrate the validity and efficiency of the method. [ABSTRACT FROM AUTHOR]

Describes a vehicle-mounted radar for dual-purpose monitoring of birds. Use and efficacy of radar monitoring with commercially available marine surveillance radar; System components; Construction and installation.

A new computationally efficient algorithm-based propagator method for two-dimensional (2-D) direction of- arrival (DOA) estimation is proposed, which uses two parallel uniform linear arrays. The algorithm takes advantage of the special structure of the array which enables 2-D DOA estimation without pair matching. Simulation results show that the proposed algorithm achieves very accurate estimation at a computational cost 4 dB lower than that of standard methods. [ABSTRACT FROM AUTHOR]

The Inmarsat Broadband Global Area Network (BGAN) L-band downlink signal from a radar viewpoint is studied. The signal is modelled and its ambiguity function (AF) is analysed and the AF is compared with that of the real recorded signal. It is shown that the AF of a single Inmarsat channel has an interference floor of -40 dB for 80 ms integration time. The AF of the Inmarsat BGAN signal is improved by combining multiple frequency channels with channel overlap. [ABSTRACT FROM AUTHOR]

A new design concept of a wideband radar absorbing structure consisting of load-bearing glass/MWCNT added epoxy composite and having low density/lightweight characteristics for C- to X-band and X- to Kuband radar is presented. The proposed radar absorbing structures have triple layers which are the low density and light weight layer to reduce the total weight, covering layers to protect the foam layer from humidity absorption, and a load-bearing layer as the actual structural layer. The proposed designs satisfied -10 dB absorption in the C-band to X-band and X-band to Ku-band using only two different materials. Moreover, from a practical point of view, since thickness control of absorbing structures is an important factor for the absorbing performance, the proposed structures could minimise fabrication errors (precise thickness controls) by employing multiple layers for wideband absorbing performance. [ABSTRACT FROM AUTHOR]

Since the terrain slope cannot be neglected for forest height inversion with polarimetric synthetic aperture radar interferometry (PolInSAR), a sloped random volume over ground (S-RVoG) model is proposed to correct the terrain distortion for forest parameters estimation. A significant model complexity reduction is achieved by aligning the reference frame along the local terrain slope and changing the corresponding radar geometrical configuration. The proposed S-RVoG model inversion promises to provide much more accurate estimation of forest parameters and is validated with L-band PolInSAR data produced by PolSARpro software developed by the European Space Agency (ESA). [ABSTRACT FROM AUTHOR]

The problem of signal detection for cognitive radar (CR) is considered, and a closed-loop detection system is proposed to detect the extended target in the presence of signal-dependent interference. In the system, the estimator of target impulse response (TIR) and waveform design are used to improve the detection performance of CR, and the estimate of TIR is also used for designing the matched waveform. In addition, in order to improve the reliability of detection, the two-step process which is called estimation before detection is proposed. Simulation results indicate that the proposed system performs better than the traditional radar system which used the fixed waveform. [ABSTRACT FROM AUTHOR]

The classical incoherent integrator is an important detection scheme in radar signal processing, owing to its simplicity and ease of implementation. In the context of compound Gaussian clutter, a new expression for the probability of detection is derived. This is applied to analyse the detector's performance in Pareto intensity clutter. [ABSTRACT FROM AUTHOR]