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SAR image of natural and man-made targets. The right sub-figure is the zoomed version of the left sub-figure with specific focuses on the fence, light pole, tree, and house.
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A passive bistatic ground-based synthetic aperture radar (PB-GB-SAR) system without a dedicated transmitter has been developed by using commercial-off-the-shelf (COTS) hardware for local-area high-resolution imaging and displacement measurement purposes. Different from the frequency-modulated or frequency-stepped continuous wave signal commonly use...
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... time, the processing time is increased to 4 μs due to the larger detection distance. To focus SAR images, BPA is used instead of RMA, as a lot of zero-padded samples in the azimuth direction make RMA significantly time-consuming while BPA can use a larger grid size to reduce the computational complexity. The resulting image is shown in Fig. 18, where the fence, light pole, tree, and small house can be imaged, as clearly shown in the right sub- figure. Furthermore, the image in the left sub-figure shows two cars located at about 60 m and 65 m in the parking lot, as indicated by the rectangle. By overlaying the SAR image with the aerial picture provided by Google maps, it can ...
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Conventional radar cross section (RCS) measurements require far-field or compact-antennatest-range (CATR) conditions, which have strict restrictions and high implementation costs. By contrast, RCS extrapolation methods in the near zone are more convenient and practical, which become the research emphasis in recent years. This paper presents a novel...
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... Passive bistatic radar (PBR) itself does not emit an electromagnetic signal but uses the third-party non-cooperative emitter as the illuminator of opportunity (IoO) for target detection and tracking [1,2]. Compared with the traditional active radar, it has the following advantages: (1) No need to build transmitter, low cost, and small size; (2) No specific frequency distribution and no electromagnetic pollution; (3) The radiation sources are widely distributed, which is convenient for information fusion, radar networking and multi-station positioning. ...
... Passive bistatic radar (PBR) itself does not emit an electromagnetic signal but uses the third-party non-cooperative emitter as the illuminator of opportunity (IoO) for target detection and tracking [1,2]. Compared with the traditional active radar, it has the following advantages: (1) No need to build transmitter, low cost, and small size; (2) No specific frequency distribution and no electromagnetic pollution; (3) The radiation sources are widely distributed, which is convenient for information fusion, radar networking and multi-station positioning. Therefore, in recent years, PBR has attracted extensive attention [3][4][5][6]. ...
With the development of radio technology, passive bistatic radar (PBR) will suffer from interferences not only from the base station that is used as the illuminator of opportunity (BS-IoO), but also from the base station with co-frequency or adjacent frequency (BS-CF/AF). It is difficult for clutter cancellation algorithm to suppress all the interferences, especially the interferences from BS-CF/AF. The residual interferences will seriously affect target detection and DOA estimation. To solve this problem, a novel target detection and DOA estimation method for PBR based on compressed sensing sparse reconstruction is proposed. Firstly, clutter cancellation algorithm is used to suppress the interferences from BS-IoO. Secondly, the residual interferences and target echo are separated in spatial domain based on the azimuth sparse reconstruction. Finally, target detection and DOA estimation method are given. The proposed method can achieve not only target detection and DOA estimation in the presence of residual interferences, but also better anti-mainlobe interferences and high-resolution DOA estimation performance. Numerical simulation and experimental results verify the effectiveness of the proposed algorithm.
... Ground-based synthetic aperture radar (GB-SAR) systems have been widely used to simulate various satellite/airborne SAR configurations for the next generation as well as its own use for ground imaging and surface change detection. Various interferometric [9][10][11][12] and tomographic SAR [13][14][15][16] have been successfully tested in GB-SAR systems owing to the highly accurate repeatability and versatile system operability. Krysik et al. [17] tested a bistatic GB-SAR configuration as a combination of GB-SAR and satellite. ...
... . (12) Inserting Equation (12) into (11) gives the azimuth resolution as follows. ...
... Multiples can be seen in azimuth direction due to azimuth ambiguity. This happened because we have not imposed the restriction of the coherent integration length due to the beam width, as shown in Equation (12). This was done intentionally to check if the azimuth step interval is small enough to avoid azimuth ambiguity in the image area of interest. ...
Ground-based synthetic aperture radar (GB-SAR) is a useful tool to simulate advanced SAR systems with its flexibility on RF system and SAR configuration. This paper reports an indoor experiment of bistatic/multistatic GB-SAR operated in Ku-band with two antennae: one antenna was stationary on the ground and the other was moving along a linear rail. Multiple bistatic GB-SAR images were taken with various stationary antenna positions, and then averaged to simulate a multistatic GB-SAR configuration composed of a moving Tx antenna along a rail and multiple stationary Rx antennae with various viewing angles. This configuration simulates the use of a spaceborne/airborne SAR system as a transmitting antenna and multiple ground-based stationary antennae as receiving antennae to obtain omni-directional scattering images. This SAR geometry with one-stationary and one-moving antennae configuration was analyzed and a time-domain SAR focusing algorithm was adjusted to this geometry. Being stationary for one antenna, the Doppler rate was analyzed to be half of the monostatic case, and the azimuth resolution was doubled. Image quality was enhanced by identifying and reducing azimuth ambiguity. By averaging multiple bistatic images from various stationary antenna positions, a multistatic GB-SAR image was achieved to have better image swath and reduced speckle noise.
... A limited number of papers have reported the use of GB-SAR for bistatic configurations such as the use of a GB-SAR as a passive receiver and a satellite SAR as a trans-2 of 10 mitter [12] and the use of a ground-based transponder to redirect a transmitting signal to obtain the target's two-dimensional displacement vector [13]. ...
... The whole system was controlled by a notebook computer with an in-house data acquisition software. tions such as the use of a GB-SAR as a passive receiver and a satellite SAR as a transmitter [12] and the use of a ground-based transponder to redirect a transmitting signal to obtain the target's two-dimensional displacement vector [13]. ...
... Remote Sens. 2021,13, 63 ...
Recent advancement of satellite synthetic aperture radar (SAR) techniques require more sophisticated system configurations such as the use of bistatic antennas or multi-frequencies. A ground-based experiment is a cost-effective and efficient way to evaluate those new configurations especially in the early stage of the system development. In this paper, a ground-based synthetic aperture radar (GB-SAR) system was constructed and operated in a bistatic mode at Ku-band where a receiving antenna (Rx) follows a transmitting antenna (Tx) separated by a baseline B. A new bistatic GB-SAR focusing algorithm was developed by modifying a conventional range-Doppler algorithm (RDA), and its performance has been evaluated by comparing the results with those from a back-projection algorithm (BPA). The results showed good performance of RDA at far range approaching nominal resolutions of 9.4 cm in range and 4.5 cm in azimuth, but limited quality at near range due to the approximation used in RDA. Signals from three trihedral corner reflectors (CR) reduced with increasing B, showing a typical bidirectional scattering behavior of CR. This GB-SAR system will be a testbed for new SAR imaging configurations with variations in antenna positions and target properties.
Urban infrastructure is an important part of supporting the daily operation of a city. The stability of infrastructure is subject to various deformations related to disasters, engineering activities, and loadings. Regular monitoring of such deformations is critical to identify potential risks to infrastructure and take timely remedial actions. Among the advanced geodetic technologies available, radar interferometry has been widely used for infrastructure stability monitoring due to its extensive coverage, high spatial resolution, and accurate deformation measurements. Specifically, spaceborne InSAR and ground-based radar interferometry have become increasingly utilized in this field. This paper presents a comprehensive review of both technologies for monitoring urban infrastructures. The review begins by introducing the principles and their technical development. Then, a bibliometric analysis and the major advancements and applications of urban infrastructure monitoring are introduced. Finally, the paper identifies several challenges associated with those two radar interferometry technologies for monitoring urban infrastructure. These challenges include the inconsistent in the distribution of selected measurements from different methods, obstacles arising from rapid urbanization and geometric distortion, specialized monitoring techniques for distinct urban features, long-term deformation monitoring, and accurate interpretation of deformation. It is important to carry out further research to tackle these challenges effectively.
Target three-dimensional (3D) high-resolution imaging via multiple-input multiple-output (MIMO) radar may suffer from a heavy sampling burden and complicated radio frequency interferences. Considering a collocated two-dimensional wideband MIMO radar under dynamic wideband interference (WBI), this paper proposes a cognitive method to achieve a 3D high-resolution target image with a reduced sampling cost. Firstly, based on the known knowledge of the target and WBI, provided by previous measurements, optimal sparse sampling in the 3D signal domain is conducted to reduce the number of sub-pulses and transceiving antennas by solving an optimization problem. Then, the detection and removal of the interfered signal components are conducted to provide the WBI information for following measurements and the interference-free signal cube for the target imaging process. Finally, by using the tensor-based smoothed L0 algorithm, the 3D high-resolution image of the target is obtained, providing the target information for the next measurement. Based on these three steps, a cognitive sparse imaging loop is formed for MIMO radar under WBI situations. The simulation and experiment results demonstrate the effectiveness and advantage of the proposed methods.
A fixed-receiver mobile-transmitter passive bistatic synthetic aperture radar (MF-PB-SAR) system, which uses the Sentinel-1 SAR satellite as its non-cooperative emitting source, has been developed by using embedded software-defined radio (SDR) hardware for high-resolution imaging of the targets in a local area in this study. Firstly, Sentinel-1 and the designed system are introduced. Then, signal model, signal pre-processing methods, and effective target imaging methods are presented. At last, various experiment results of target imaging obtained at different locations are shown to validate the developed system and the proposed methods. It was found that targets in a range of several kilometers can be well imaged.
This paper explores novel architectures for fast backprojection based video synthetic aperture radar (BP-VISAR) with multiple GPUs. The video SAR frame rate is analyzed for non-overlapped and overlapped aperture modes. For the parallelization of the backprojection process, a processing data unit is defined as the phase history data or range profile data from partial synthetic-apertures divided from the full resolution target data. Considering whether full-aperture processing is performed and range compression or backprojection are parallelized on a GPU basis, we propose six distinct architectures, each having a single-stream pipeline with a single GPU. The performance of these architectures is evaluated in both non-overlapped and overlapped modes. The efficiency of the BP-VISAR architecture with sub-aperture processing in the overlapped mode is accelerated further by filling the processing gap from the idling GPU resources with multi-stream based backprojection on multiple GPUs. The frame rate of the proposed BP-VISAR architecture with sub-aperture processing is scalable with the number of GPU devices for large pixel resolution. It can generate 4096 × 4096 video SAR frames of 0.5 m cross-range resolution in 23.0 Hz on a single GPU and 73.5 Hz on quad GPUs.
Artificial Intelligent based smart Internet of Things(AI-based IoTs) refers to a network that has sensing data analysis function and network automatic management functions such as self-diagnosis and self-healing function. Among them, self-healing function is a critical problem in an AI-based Passive Bistatic Radar Sensor Network(PBRSN). Much different from active bistatic radar, transmitters in PBRSN are not deployed by network designer and may be out of work due to some irresistible reasons, then the coverage quality of a protected region cannot be satisfied. Therefore, how to localize barrier gap accurately and mend barrier gap quickly are the most important issues in a PBRSN. In this paper, we study the problem of how to automatically localize barrier gap and compute the locations of new receivers for coverage quality improvement in a PBRSN with an AI-based smart node, where the network was providing
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barriers coverage for a protected region by adopting receivers optimal deployment strategy. First, we design an algorithm to localize all barrier gaps, and then an algorithm called Deployment Line between Sub-barriers Algorithm (DLSA) is designed to compute the locations of new receivers inside gap region with the objective of minimizing the total number of new receivers. Finally, extensive simulations are conducted to validate the correctness and effectiveness of our proposed algorithms. The simulation results show that our gap finding algorithm can localize all barrier gaps accurately. While the DLSA can mend a barrier gap with fewer receivers if there is at least one working transmitter in this barrier.
In this work we present an overview of ground-based radar interferometry applications, using both real and synthetic aperture configurations, to measure deformations and vibration frequencies of infrastructures and terrain displacement due to geological phenomena. A short introduction to the basic principles of ground-based radar interferometry and the concept of interferometric coherence is provided. The interferometric processing of radar data provides the measurement of the Line-of-Sight (LoS) displacement with a sub-millimeter precision. In this paper we show results obtained in the monitoring of landslides, piers, dams, towers and bridges. Results have been obtained by means of a ground-based radar sensor working in the Ku-band with a range resolution of 0.75 m. Furthermore, we provide a review of literature on ground-based radar applications to volcano and glacier monitoring and measurement of vibration frequencies telecommunication and wind towers. The issues of measurement precision and artifacts due to propagation in the atmosphere are also discussed.
Passive synthetic aperture radar (SAR) using Global Navigation Satellite System (GNSS) signals as the illuminators of opportunity has a relative coarse range resolution due to the narrow bandwidth of the navigation signals and the bi-static acquisition geometry, limiting its application for high-resolution requirement. In this paper, an image formation algorithm for range resolution improvement is investigated. A modified second order differentiation based method is applied on the range compressed signal of reference channel and surveillance channel, improving range resolution and keeping side-lobes at a lower level simultaneously, and the phase of processed signal is preserved by phase multiplication compensation for the following azimuth compression processing. To validate the effectiveness and benefits of the proposed algorithm in terms of range resolution and targets side-lobes, point targets simulation under different situations and real field experiment with strong scatters are conducted and discussed. Compared with the traditional GNSS-based passive SAR imaging algorithm, the results of the proposed method show that the imaging performance can be improved for better range resolution and lower side-lobes, benefitting for better distinguishing nearby targets and recognizing weak targets.
