Bistatic Sonar Research Articles

Research on Bistatic Sonar Positioning and Its Optimization Algorithm

Research on Bistatic Sonar Positioning and Its Optimization Algorithm

Active Control of the Reflection Coefficient of an Underwater Surface

From a strategic point of view, it is essential to protect underwater vehicles from being detected by opponents. Modern mono- or bistatic sonar systems are capable of precisely determining the position of a watercraft. In order to triangulate the positions of watercrafts, the sonar sends out acoustic signals that are reflected by the vehicles’ surfaces. These deflected sound waves are subsequently detected and evaluated. How well an object can be detected using a sonar can be measured according to the target strength. Through their shape, construction and choice of materials, modern underwater vehicles are optimized in relation to minimizing their radiated and reflected sound waves; in this way, their target strength is minimized. These passive measures are particularly effective in the medium- and high-frequency range down to 1500 Hz. To effectively reduce reflections at lower frequencies, an active system is developed in this study and evaluated in a laboratory test with a water-filled impedance tube. The incident sound waves were measured in front of an active surface and then processed using an adaptive control system based on an FPGA platform. The system operates with a very thin piezoceramic applied to the surface in order to minimize the reflections of the sound waves. The laboratory tests showed the high effectiveness of the system under the influence of sonar-like signals.

Target Tracking Using Time Delay and Doppler Shift With Nonnegligible Motion Effect in Bistatic Sonar

Target Tracking Using Time Delay and Doppler Shift With Nonnegligible Motion Effect in Bistatic Sonar

Ray-Based Analysis of Subcritical Scattering from Buried Target

A ray approach is used to simulate subcritical scattering from a buried target at low-to-high frequencies (100 Hz–15 kHz). A penetrating wave at a subcritical angle decays along the depth at the bottom (i.e., evanescent wave) and propagates horizontally at a subcritical angle-dependent speed lower than the sound speed of the bottom. The corresponding target strength (TS) is distinguished from that of a standard plane wave. Its pattern is asymmetric by the evanescent wave including for symmetric targets and is more complicated owing to the higher wavenumber induced by the lower speed of the evanescent wave. A scattered signal is simulated by considering the features of the penetrating wave with the TS and then verified using the finite element method. In the ray approach, once the TS is computed, a scattered field is efficiently derived with low computational complexity. Strong peaks are observed in the scattered signal via mid-frequency enhancement; however, their amplitudes are less than those yielded by the free-field target owing to the more diminished penetrating waves at higher frequencies. The peaks indicate the possibility of detecting the buried target using a receiver near the target (bistatic sonar) with a broadband source signal that includes low-to-mid frequencies.

GLRT-based detection in bistatic sonar under strong direct blast with multipath propagation

Direct blast, a strong interference in bistatic sonar, is difficult to suppress because of multipath propagation for blasts and signals. A generalized likelihood ratio test (GLRT)-based detection scheme in the frequency domain of the received signals was proposed, and the unknown parameters were estimated using maximum likelihood estimate (MLE) under a multipath environment. The distributions of the test statistic of detectors for known and unknown noise power were given in theory, and the probability of detection was determined. The performance of the detector decreases by 4 dB when the noise power was evaluated using MLEs. Simulations demonstrated the effectiveness of the detector under active detection configuration with a large bistatic angle under a low signal-to-direct blast ratio (SDR). The impact factors, such as the SDR, bandwidth, path number and DFT point number were discussed. The proposed detection scheme was verified with a lake experiment.

A Study of Performance Characteristics for Active Sonar in Korean Shallow Seawater Temperature Structures

It is obvious that understanding the effects of shallow water environment of Korea is very important to guarantee the optimal performance of active sonar such as monostatic and bistatic sonar. For this reason, in this paper, we analyzed the detection performance characteristics for various depth deployments of sonar in summer, winter and water temperature inversion environments, which environments are frequently observed in shallow water of Korea such as the Yellow sea. To analyze only effects of water temperature structures on target detection performance, we applied range independent conditions for bottom, sea surface and water temperature characteristics. To understand the characteristics of detection performance, we conducted transmission loss and signal excess modeling. From the results, we were able to confirm the characteristics of detection performance of active sonar. In addition, we verified that operation depth of transmitter and receiver affects the detection performance. Especially in the water temperature inversion environment, it was confirmed that the shadow zone could be minimized and the detection range could be increased through bistatic operation.

A cost‐efficient joint target location and clock bias estimation technique using multiple time step measurements in mobile bistatic sonar

Active localization of a stationary target is one key issue in applications of bistatic sonar based on bistatic range (BR) measurement. However, the complex underwater environment makes achieving the synchronization between the transmitted station and the received station difficult. For solving the synchronization problem, this study relies on mobile bistatic sonar to acquire measurement information at multiple time steps. After that, the target location and clock bias are jointly estimated by solving a non-linear least square problem. To this end, a recursive scheme is proposed to optimise the measurement cost and reduce the impact of the initial value to achieve accurate estimation by taking full advantage of the redundant measurement information. Orthogonal transformation is used to ensure computational efficiency and numerical reliability. The Cramer–Rao Lower Bound (CRLB) is also derived as a lower bound on the error in estimating the target position and clock bias. Simulation results show that the proposed method achieves the CRLB performance and optimises the measurement cost over the small error region under Gaussian noise.

Comparison of target classification accuracy according to the aspect angle and the bistatic angle in bistatic sonar

Comparison of target classification accuracy according to the aspect angle and the bistatic angle in bistatic sonar

Sparse Reconstruction-Based Inverse Scattering Imaging in a Shallow Water Environment

Bistatic sonar or multistatic sonar system can collect more scattering information of targets than a monostatic sonar system. In this paper, sparse learning via iterative minimization method (SLIM) is introduced to distinguish wave components for time-domain (TD) back-propagation (BP) inverse scattering imaging improvement. Unlike the prevailing high central frequency (>100 kHz) and wideband imaging sonar systems, a relatively low-frequency band (1–10 kHz) is considered here. Due to the low sidelobe output of SLIM, the investigated object’s surface in TD-BP image is much clearer in an ideal two-dimensional free field case. Furthermore, when the environmental information is known, this sparse reconstruction-based channel deconvolution method can be implemented to recognize, categorize the main propagating paths and then rectify their time of arrivals. Compared with the phase conjugation-based channel deconvolution method, the proposed approach’s results have fewer sidelobes and higher signal-to-background ratio in the simulation.

신호처리를 고려한 양상태 소나 시스템의 표적 위치 추정 오차 분석

능동 소나 시스템(Active Sonar System)은 수중의 은밀한 표적을 탐지, 추적, 식별하기 위해 사용되는 시스템으로 최근 송신과 수신 플랫폼이 이격되어 있는 양상태 소나(Bi-Static Sonar System)에 대한 연구가 활발히 이루어지고 있다. S. Coraluppi는 양상태 소나의 기하학적 구조와 다양한 오차를 고려했을 때 나타나는 표적의 위치 추정 오차를 해석적으로 분석하였다. 그러나 이 연구는 오차의 값을 임의로 설정하여 분석하였기 때문에 실제 해상환경이나 신호처리 알고리즘의 영향을 반영하지 못하였다. 본 논문에서는 신호처리 알고리즘의 오차를 분석하고 이를 반영하여 나타나는 표적 위치 오차를 분석하였다. 시뮬레이션 결과 신호처리 알고리즘의 특성이나 배열센서의 특성 등이 표적 위치 추정에 반영되는 보다 실제적인 결과를 얻을 수 있었다.

Converted Measurement Sigma Point Kalman Filter for Bistatic Sonar and Radar Tracking

Tracking with bistatic sonar or radar measurements is challenging due to the fact that the measurements are nonlinear functions of the Cartesian state. The performance of existing approaches, including the extended Kalman filter and sigma point Kalman filters, such as the unscented Kalman filter and cubature Kalman filter, may not be acceptable in terms of mean square error or tracker consistency (i.e., the tracker's state estimation error covariance is not statistically consistent with the actual estimation errors). This paper generalizes the sigma point Kalman filter (SPKF) as a converted measurement SPKF. The resulting converted measurement sigma point Kalman filter is demonstrated to have improved performance over the conventional SPKF when employed in a bistatic tracking scenario.

Bistatic sonobuoy deployment strategies for detecting stationary and mobile underwater targets

The problem of determining effective allocation schemes of underwater sensors for surveillance, search, detection, and tracking purposes is a fundamental research area in military operations research. Among the various sensor types, multistatic sonobuoy systems are a promising development in submerged target detection systems. These systems consist of sources (active sensors) and receivers (passive sensors), which need not be collocated. A multistatic sonobuoy system consisting of a single source and receiver is called a bistatic system. The sensing zone of this fundamental system is defined by Cassini ovals. The unique properties and unusual geometrical profile of these ovals distinguish the bistatic sensor allocation problem from conventional sonar placement problems. This study is aimed at supporting decision makers in making the best use of bistatic sonobuoys to detect stationary and mobile targets transiting through an area of interest. We use integral geometry and geometric probability concepts to derive analytic expressions for the optimal source and receiver separation distances to maximize the detection probability of a submerged target. We corroborate our analytic results using Monte Carlo simulation. Our approach constitutes a valuable “back of the envelope” method for the important and difficult problem of analyzing bistatic sonar performance.

Modeling on Distance Error of Bistatic Sonar Detection

Based on the principle of bistatic sonar orientation, we build the model of estimation on distance error considering the measured error of time, direction and acoustic velocity, and detailedly analyse the mean square error influenced by centrifugal rate of ellipse and orientation. The outcome of simulation indicate that the orientation and position of the targets apart from the sender and receiver impact the estimated precision of distance. On the condition of the distance of sender and receiver fixed, the position more apart from the sender and receiver, the distance estimation lower effect influenced by the orientation of targets, and the value of mean square error of distance keeps in a lower scope. According to the model of estimation presented by this paper, deploy the bistatic sonar reasonably can realized high precision and detected targets in a long distance.

Robust localization using geographic information in bistatic sonar

This article proposes a robust localization algorithm by improving the accuracy of the source position, receiver position, and sound speed using the known position of an object in the sea. The accuracy of those three types of information greatly influences the performance of the target localization in bistatic sonar. Although the locations of the source and receiver can be obtained using the global positioning system, there are still some position errors due to the limitations of global positioning system–based positioning systems and tidal current. In addition, the speed of the sound in the sea changes with temperature. The target estimation error was analyzed mathematically in terms of the mentioned errors. An improved localization is proposed using the accurate positions of objects in the sea, which can compensate for the errors in the source position, receiver position, and sound speed. The proposed algorithm is compared with the conventional algorithm through computer simulations.

Passive and active acoustical studies of ocean surface waves

This paper reviews previous work with Professor David Farmer, on the use of acoustical techniques to observe and measure ocean surface waves. In passive acoustics, breaking surface waves in the open ocean were observed with a hydrophone array deployed close to the surface to track individual breaking events. The spatial and temporal statistics of braking events, such as velocity and breaking probability, were determined and compared with simultaneously measured directional wave spectra. The comparisons suggest that wave breaking occurs at multiple scales and that the mean scale of breaking is substantially smaller than the associated with the dominant wind wave component. In an active acoustical study, an incoherent bistatic sonar mounted on the seafloor was used to measure currents close to the ocean surface and within the crests of large, steep waves. Individual estimates of the currents at, and close to, the surface were made with sufficient temporal resolution to identify kinematics in the crests of large waves. Observations acquired in the North Sea are examined to evaluate both the potential merits and limitations of the measurement approach. The observations lead to some conclusions regarding wave kinematics during a storm in which the wind speed reached ∼17 m s−1.

음원과 수신기 사이에 교차 산란단면적을 이용한 양상태 잔향음 모의

소나 운용에서 잔향음은 수중 표적 탐지의 제한요소이기 때문에 정확한 예측이 중요하다. 최근에는 단상태소나 연구에서 공간적으로 송수신기의 위치가 다른 양상태 소나에 대한 연구로 확장되고 있는 추세이다. 양상태 잔향음을 모의하기 위해서는 양상태 음파전달, 양상태 산란강도 및 산란단면적 등에서 단상태와 다른 복잡한 계산이 요구된다. 전 세계적으로 양상태 잔향음에 대한 연구가 활발하게 진행되고 있지만 잔향음을 예측하는데 중요한 요소인 양상태 산란단면적을 정확하게 계산하는 방법에 대한 연구는 미비하다. 본 논문에서는 거리 독립 환경의 양상태 잔향음모의에서 두 원의 교차되는 면적을 응용하는 새로운 산란단면적 계산 방법을 제안한다. 최종적으로 본 논문의 양상태 산란단면적 계산 방법으로 모의된 잔향음 준위는 기존에 제안되었던 방법들의 예측값과 비교되며 2013년 5월에 수행된 해상 실험의 측정값과 비교를 수행하였다. It is important to predict accurately reverberation level, which is a limiting factor in underwater target detection. Recently, the studies have been expanded from monostatic sonar to bistatic sonar in which source and receivers are separated. To simulate the bistatic reverberation level, the computation processes for propagation, scattering strength, and scattering cross section are different from those in monostatic case and more complex computation processes are required. Although there have been many researches for bistatic reverberation, few studies have assessed the bistatic scattering cross section which is a key factor in simulate reverberation level. In this paper, a new method to estimate the bistatic scattering cross section is suggested, which uses the area of intersection between two circles. Finally, the reverberation levels simulated with the scattering cross section estimated using the method suggested in this paper are compared with those estimated using the methods previously suggested and those measured from an acoustic measurements conducted in May 2013.

An Improved of Extended Kalman Filtering Method on Tracking Accuracy of Bistatic Sonar System

The Extended Kalman Filter methods were widely used in the estimation of tracing situation in military fields. In this paper, we proposed a method of using multiple iteration of the observation and covariance matrix in the measuring equations during the tracking process in bistatic sonar system. Therefore the iterating extended kalman filtering (IEKF) algorithm was emerged at this situation. The simulation results show that the proposed tracing algorithm exhibits higher accuracy compared with the EKF algorithm. This new method can take full application of the measured information to improved the tracing accuracy in the whole controlled area. Keywords: bistatic sonar; tracing accuracy; IEKF algorithm; target moving analysis

An Algorithm of Improving Least-Square Method on Tracing Accuracy of Bistatic Sonar System

The least square algorithms were widely used in the estimation of localizing and tracing situation in military fields. In this paper, we proposed a method of using a full rank matrix instead of using singular value decomposition to solving the non-full rank matrix. Therefore the improving least square (ILS) algorithm was emerged at this situation. The simulation results show that the proposed tracing algorithm exhibits higher accuracy compared with the least square algorithm. This new method can take full application of the measured information to improved the tracing accuracy in the whole controlled area.

The Bistatic MIMO Imaging Algorithm Based on Waveform Diversity

Due to the large distance between transmitting array and receiving array in bistatic MIMO, The bistatic MIMO is unable to use the waveform diversity technology base on the monostatic MIMO to improve the resolution of the detection. And bistatic MIMO angle estimation algorithm based on the spatial spectral estimation is unable to get coherent gain from beamforming. In this paper, position calculating of the bistatic sonar is used to get the relationship among DOD DOA and propagation distance. The array manifold of virtual array is constructed in each scan position in 2-d imaging. The improved waveform diversity technology is used in the imaging of bistatic MIMO to improve the resolution of the detection.

A Research of Improving Data Fusing Algorithm Localization in Multistaic Sonar

For the purpose of improving the localization accuracy of bistatic sonar in baseline districts and side districts, the most effective method is to increase the number of transmitting and receiving stations, which forms a multistatic sonar system. The mature algorithm of multistatic sonar system which contains three distance measurements volume in one subset, calls the multistatic time-only localization (TOL) algorithm. This paper proposes a new algorithm which merges the TOL algorithm and IBOL algorithm. of improving the bearing-only localization algorithm. The simulation results show that the proposed localization algorithm exhibits higher accuracy compared with the TOL algorithm and IBOL algorithm. This new method can take full application of the measured information to improved the localization accuracy in the whole controlled area.