Search

Rock-fall incidents have the characteristics of multiple, sudden and random, which threaten the surrounding buildings and traffic lines. This paper studied the monitoring and prediction of rock falls with a new synthetic aperture radar (SAR) technology. One of the most important factors in rock-fall target detection is the signal-to-clutter-plus noise ratio (SCNR) after clutter suppression, which should be maximized before rock-fall target detection. Through analysing the remainder characteristics of rock-fall targets after clutter suppression, a method of removing the quadratic frequency-modulated (FM) component associated with the azimuth velocity and along-track velocity of a rock-fall target is proposed. After removing the quadratic FM component using dechirp technology, focus is placed on the remainder signal of a rock-fall target in a Doppler domain image, and the SCNR of the signal is maximized. This method provides effective rock-fall target detection. To resolve the contradiction between the computational accuracy and the accuracy of the along-track velocity, this paper adopts gradual approach technology. Finally, by analysing the focused signal characteristics, a method of rock-fall target parameter estimation is proposed. The effectiveness of the presented method is demonstrated by both theoretic analysis and simulations. [ABSTRACT FROM AUTHOR]

Foreign body intrusion will cause interruption of road transportation and bring great threat to operation safety. Detection of foreign body intrusion is a key step for efficient recognition, location, and tracking of foreign body intrusion. Current detection approaches of foreign body intrusion are available, but can only detect in a certain range. As an active remote sensing technique, synthetic aperture radar (SAR) can monitor wide areas of the earth, and thus provides a viable way to detect road foreign body intrusion in a wide range. Firstly, because of large data, the SAR data in the azimuth is sparsely sampled to reduce data sampling. Then, before detection of foreign body intrusion, compressed sensing (CS) theory is utilized to reconstruct the sparsely sampled data. At last, Kalman filtering is adopted to detect foreign body intrusion. The simulated results and real data processing results both validate the proposed method. [ABSTRACT FROM AUTHOR]

Ground moving target indication (GMTI) is an important application of future multi-channel high-resolution wide-swath (MC-HRWS) synthetic aperture radar (SAR) system. This paper improves the extended displaced-phase-center antenna (EDPCA) method for efficient GMTI with a MC-HRWS SAR System. This processing method called improved EDPCA is derived in this paper and is applied to simulated data and real data in order to validate the theory. Compared with EDPCA, the improved EDPCA can decrease the degrees of freedom (DOFs) required by GMTI processing and the false alarm rate induced by the ambiguous image of moving target. In addition, signal-to-noise ratio (SNR) loss of moving target caused by linear range cell migration (RCM) can be avoided without a priori knowledge of the radial velocity. [ABSTRACT FROM AUTHOR]

Rockfalls influence the safety of the surrounding infrastructure and the normal operation of transportation lines. The application of synthetic aperture radar (SAR) technology is a new method of rock-fall monitoring and disaster prediction. This paper proposes a new method of dynamic monitoring and parameter estimation for rockfalls based on a multichannel airborne SAR system. First, the signal model of the multichannel airborne SAR system is derived. Then, to improve performance, the traditional displaced phase centre antenna (DPCA) method is extended to three or more receiver channels. This method can be effectively applied for rock-fall target detection, as well as to precisely estimate rock-fall target parameters and resolve the ambiguity issues associated with the estimation of rock-fall target parameters. Finally, simulation results are used to validate the proposed approach. [ABSTRACT FROM AUTHOR]

For synthetic aperture radar (SAR), a system impulse response with low sidelobes is very important because sidelobes may interfere with the nearby scatterers and contribute to multiplicative noise. It is well known that a nonlinear frequency-modulation (NLFM) chirp waveform can shape the signal's power spectral density and provide a radar matched filter output with lower sidelobes without loss of the signal-to-noise ratio when compared with the linear frequency-modulation chirp. These advantages make the NLFM waveform to be a promising candidate to improve the imaging quality for SAR. However, so far, to our knowledge, there is no real application of NLFM waveforms for SAR. This letter, for the first time, demonstrates the airborne SAR experiment using an NLFM waveform. In the underlying experiment, the construction of the NLFM signal is investigated and a modified range migration algorithm (RMA) is developed to adapt it for focusing the NLFM SAR data. Both simulation and experimental results exhibit the promising power of the NLFM chirp and show the accuracy of the proposed modified RMA. [ABSTRACT FROM PUBLISHER]

Multiple-input multiple-output synthetic aperture radar (MIMO-SAR) is of great potential for future high-resolution and wide swath imaging. However, its development is limited as the condition of orthogonality among the multiple waveforms received simultaneously is hard to satisfy. In this paper, a class of linear frequency modulation-based MIMO waveforms is introduced to settle this problem and correspondingly an effective processing scheme is proposed based on digital beam forming in elevation. In this scheme, for separating the mixed signals, null steering technique is employed to extract one waveform from the others. The main advantages of the proposed scheme include transmitting simultaneously, good inter-orthogonality between different waveforms with identical frequency range, separating them with mutual interference cancellation and good imaging quality. The main procedure of this scheme is derived and described in detail in the paper. Furthermore, an example MIMO-SAR system is provided for numerical simulation and the simulation results are obtained to validate the proposed scheme. [ABSTRACT FROM PUBLISHER]