Target Discrimination Capability Research Articles

Acoustic behaviour in bottlenose dolphins during two different target discrimination tasks

Echolocation is an active sensory system that gives an acoustic representation of the surroundings by the animal emitting clicks, detecting and analysing echoes. However, little is known about dolphin biosonar in moving animals, as well as of the process of controlling click emissions, and the cues used by the animal to discriminate between different targets. We studied how bottlenose dolphins may use their dynamic sound production and hearing abilities, along with head and body movements, to detect and classify objects through echolocation. We designed two different experiments with blindfolded bottlenose dolphins (Tursiups truncatus) swimming freely along the pool and actively discriminating between two targets of three different materials, and a second one to determine the capability to discriminate wall thickness differences in cylindrical targets of the same material. By means of synchronized cameras and hydrophones, we observed clear differences between individuals of the same species in terms of ability to discriminate, but similar performance with the harbor porpoises in relation to the materials chosen with the difficulty of the task. Studying how the dolphins solved a simplified echolocation task, allow a better understanding of the processes behind target detection and discrimination capabilities during natural biosonar circumstances .

INTERFEROMETRIC PROCESSING OF A DEVELOPED MIMO GBSAR FOR DISPLACEMENT MONITORING

Abstract. This study demonstrates the interferometric processing experiments of our developed multiple-input multiple-output ground-based synthetic aperture radar (MIMO GBSAR) system. GBSAR systems are known as precise noncontact instruments for monitoring earth dynamics. In recent years W band MIMO radars have shown interesting potential in this field due to their low cost, compact size, and high phase sensitivity. MIMO capability enables the angular discrimination of multiple targets in the same range as the radar sensor. In our previous works, we developed a high-resolution MIMO GBSAR system based on the combination of MIMO radar and mechanical rail. Accordingly, this study investigates the developed system’s displacement monitoring capability by presenting a controlled experiment, using fixed and moving corner reflectors and gathering 36 time series of data. We compare and discuss the results obtained from MIMO GBSAR and MIMO radar configurations. The results show that our developed system highly agrees with MIMO radar’s interferometric measurements while providing a better target discrimination capability and higher signal noise ratio.

Multitarget Respiration Detection With Adaptive Digital Beamforming Technique Based on SIMO Radar

The Doppler radar has been widely used in respiration detection. However, most of the existing microwave respiration detection works are intended for either a single human subject in front of the radar or multiple subjects with known positions. In this article, a system based on single-input–multiple-output (SIMO) continuous-wave (CW) radar equipped with adaptive digital beamforming (ADBF) technique is presented to detect the respiration of multiple human subjects at unknown positions simultaneously. A solution based on the modified Capon (m-Capon) direction-of-arrival (DOA) estimation and linear constraint minimal variance (LCMV) ADBF is proposed to automatically find the angles of human subjects. By forming spatially distributed beams toward the subjects of interest, human respiration can be remotely obtained. Furthermore, for the detection of each person’s respiration, nulls are also generated at the angles of nearby interfering subjects, which results in high target discrimination capability when multiple human subjects are close to each other. The experimental results show good detection accuracy compared with the reference sensor, which verifies the effectiveness of the developed system for multitarget respiration detection.

How to Specify an Electro-optical Earth Observation Camera? A Review of the Terminologies Used and its Interpretation

Since the launch of Landsat-1 in 1972, several earth observation satellites have been launched by government and private agencies. To select the optimum data for a specific application and for combining data from different sources require good clarity and understanding of various specifications provided by the sensor manufacturers. Many of the sensor parameters are not unambiguously defined in the product data-sheet. The paper reviews how the specifications adopted to describe various performance parameters of earth observation electro-optical camera are understood, and addresses the need for consistency in defining various specifications. The paper also proposes a figure-of-merit to compare various cameras for its target discrimination capability. A possible standard set of specifications are suggested, to be provided by all camera developers which would benefit both developers and users of such instruments.

Adaptive chaotic MIMO radar based on DPMM clustering and Kalman filtering technique.

A novel scheme to optimize the adaptive transmit waveform of chaotic multiple-input multiple-output (MIMO) radar is developed. The main objective of this work is to achieve high ability in target discrimination by using a Dirichlet process mixture model (DPMM)-based clustering method based on nonparametric Bayesian theory and to improve the capability of target detection by minimizing the mean square error of radar channel response via Kalman filtering (KF) technique. The two stages are the discrimination of multiple range-extended targets and the optimization of the adaptive chaos-based waveform for transmission. The adaptive chaotic MIMO waveform optimization scheme overcomes the problem of target discrimination and detection in an intelligent transportation system, where there is a need for extracting the feature of target information achieved from vehicle-mounted sensor. As the number of iterations increases, simulation experiments demonstrate better target discrimination capability provided by the proposed DPMM-KF technique as compared with the traditional waveform design method. In addition, the proposed DPMM-KF technique leads to improved target detection probability and receiver operating characteristics in the interference environment.

Improvement of Doppler measurement using multiple-input multiple-output (MIMO) concept in radar-based automotive sensor detecting pedestrians

PurposeThis paper aims to present an approach of utilizing multiple-input multiple-output (MIMO) radar concept to enhance pedestrian classification in automotive sensors. In a practical environment, radar signals reflected from pedestrians and slow-moving vehicles are similar in terms of reflecting angle and Doppler returns, inducing difficulty for target discrimination. An efficient discrimination between the two targets depends on the ability of the sensor to extract unique characteristics from each target, for example, by exploiting Doppler signatures. This study describes the utilization of MIMO radar for Doppler measurement and demonstrates its application to improve pedestrian classification through actual laboratory measurements.Design/methodology/approachMultiple non-modulated sinusoidal signals are transmitted orthogonally over a MIMO array using time division scheme, illuminating human and non-human targets. The reflected signal entering each of the receiving antenna are combined at the radar receiver prior to Doppler processing. Doppler histogram was formulated based on a series of measurements, and the Doppler spread of the targets was determined from the histograms. Results were compared between MIMO and conventional single antenna systems.FindingsMeasurement results indicated that the MIMO configuration provides able to capture more Doppler information compared to conventional single antenna systems, enabling a more precise discrimination between pedestrian and other slow-moving objects on the road.Originality/valueThe study demonstrated the effectiveness of using MIMO configuration in radar-based automotive sensor to enhance the accuracy of Doppler estimation, which is seldom highlighted in literature of MIMO radars. The result also indicated its usefulness in improving target discrimination capability of the radar, through actual measurement.

Snapshot imaging spectrometry with a heterodyned Savart plate interferometer

Imaging spectrometers are frequently used in remote sensing for their increased target discrimination capabilities over conventional imaging. Increasing the spectral resolution of these sensors further enables the system’s ability to discriminate certain targets and adds the potential for monitoring narrow-line spectral features. We describe a high spectral resolution (Δλ=1.1 nm full-width at half maximum) snapshot imaging spectrometer capable of distinguishing two narrowly separated bands in the red-visible spectrum. A theoretical model is provided to detail the first polarization grating-based spatial heterodyning of a Savart plate interferometer. Following this discussion, the experimental conditions of the narrow-line imaging spectrometer (NLIS) are provided. Finally, calibration and target identification methods are applied and quantified. Ultimately it is demonstrated that in a full spectral acquisition the NLIS sensor is capable of less than 3.5% error in reconstruction. Additionally, it is demonstrated that neural networks provide greater than 99% reduction in crosstalk when compared to pseudoinversion and expectation maximization in single target identification.

Non‐coherent adaptive detection in passive radar exploiting polarimetric and frequency diversity

The joint exploitation of polarimetric and frequency diversity is considered in this study as a way to improve the target detection capability in a FM radio-based passive radar. The authors resort to a generalised likelihood ratio test approach and derive a fully adaptive multi-frequency polarimetric detector that optimally combines the signals simultaneously transmitted by a given illuminator of opportunity and received at different carrier frequencies by differently polarised surveillance antennas. The application of the proposed detection scheme to recorded live data demonstrates the effectiveness of the multi-frequency polarimetric operation in typical scenarios, besides the expected improvement due to non-coherent integration of target echoes received on multiple channels. In particular, it is shown to provide remarkable target discrimination capability against interfering sources as well as increased robustness with respect to the time-varying characteristics of the exploited signals of opportunity.

Cognitive chaotic UWB-MIMO radar based on nonparametric Bayesian technique

This work presents a cognitive waveform selection mechanism for chaotic ultra-wideband multiple-input multiple-output (MIMO) radars. It utilizes the target discrimination capability of a Dirichlet process mixture model (DPMM)-based clustering approach to discriminate individual extended targets and applies a mutual information (MI)-based mechanism to select the best transmission waveform. This joint DPMM-MI cognitive mechanism aims at enhancing target discrimination and detection, showing a 3-dB performance gain in achieving 0.9 target detection probability over conventional MIMO radar waveforms.

On the Advantage of B-Field Sensor Arrays in TEM: From Minerals to UXO and Back Again

EM receiver systems which measure magnetic field (B-field detectors), not time rate of change of magnetic field, are in frequent use in mineral exploration, and are subject of a current development for detection of unexploded ordnance (UXO). The advantages of B-field detectors stem from both logistical and target discrimination capabilities. This paper quantifies the advantages of the B-field measurement using simple mathematical models for the response of highly-conductive mineral targets in a conducting earth, and for unexploded large-calibre steel munitions in the presence of scrap metal. The small size of B-field detectors greatly facilitates the use of arrays of sensors. A series of model studies was conducted to establish what improvement in target orientation/shape information could be achieved with single or multiple B-field sensors compared with conventional moving-loop surveys conducted using single-component single-sensor in-loop systems. The model studies show that when the target size is known (as may be the case in munitions search), the use of a single vector sensor delivers an order of magnitude greater accuracy in location in 3D space and orientation of the target, compared with the use of vertical-component only data in conventional metal detectors. When the target size is unknown, a single vector sensor can produce accurate location, but is likely to produce unstable orientation/shape estimates. We conclude that an array of receiver sensors is preferable. Comparison of a single vector sensor versus an array of three vector sensors in model studies shows that the array of three vector sensors has the advantage of delivering accurate and stable estimates of both location and orientation/shape of the target. These finding are currently being implemented in a new design of metal detector designed for location and discrimination of unexploded munitions. The results are equally applicable to the design of multiple-receiver arrays for moving-loop EM surveys in mineral exploration.

Detection and classification of underwater targets by echolocating dolphins

Many experiments have been performed with echolocating dolphins to determine their target detection and discrimination capabilities. Target detection experiments have been performed in a naturally noisy environment, with masking noise and with both phantom echoes and masking noise, and in reverberation. The echo energy to rms noise spectral density for the Atlantic bottlenose dolphin (Tursiops truncatus) at the 75% correct response threshold is approximately 7.5 dB whereas for the beluga whale (Delphinapterus leucas) the threshold is approximately 1 dB. The dolphin’s detection threshold in reverberation is approximately 2.5 dB vs 2 dB for the beluga. The difference in performance between species can probably be ascribed to differences in how both species perceived the task. The bottlenose dolphin may be performing a combination detection/discrimination task whereas the beluga may be performing a simple detection task. Echolocating dolphins also have the capability to make fine discriminate of target properties such as wall thickness difference of water-filled cylinders and material differences in metallic plates. The high resolution property of the animal’s echolocation signals and the high dynamic range of its auditory system are important factors in their outstanding discrimination capabilities.

Multifractional correlation

Multifractional correlation is proposed that is based on a new generalized fractional Fourier transform to which we refer as a multifractional Fourier transform. The multifractional correlation yields remarkable improvements in the correlation output peak intensity, peak sharpness, and light efficiency compared with convention correlation, which uses matched and phase-only filters, and still maintains better target discrimination capability and a reasonable robustness to noise. An optoelectronic hybrid system that can implement the multifractional correlation is also suggested.

The effects of noise on dolphin echolocation

The echolocation capabilities of dolphins can be seriously affected by natural ambient and man‐made noise. Many echolocation experiments have been conducted at our facility to study the effects of noise on the echolocation behavior and capabilities of dolphins. When a beluga was transported from San Diego Bay, California to Kaneohe Bay, Hawaii, the whale adjusted its sonar emissions to compensate for the louder ambient noise environment in Kaneohe Bay. It emitted higher intensity signals which had peak frequencies that were approximately one octave higher than in San Diego. Experiments with echo‐locating dolphins have shown that their target detection and discrimination capabilities can be severely degraded by the introduction of masking noise. In most situations, the dolphins compensated for the presence of masking noise by emitting more clicks per scan and by increasing their signal intensity. The response latency defined as the time between the cessation of the last click in a click train and the touching of a response paddle also increased as the masking noise level increased. However, the effects of noise emanating from a specific location can be minimized by a dolphin utilizing the directional property of its auditory system.