Electric Field Detection Sensor Systems
ISL is developing a tactical electric field (E-Field) buoy and fixed bottom mounted E field sensors, both of which detect electromagnetic radiation from potential underwater threat targets. The sensors can be used in both shallow and deep water and are not affected by acoustic noise sources such as reverberation and clutter. Potential applications for the sensor include small area search and localization, as well as harbor security and protection.
Electromagnetic Performance Prediction Modeling
ISL has a suite of proprietary models for the scattering and propagation of electromagnetic fields. The core model is our multi-layer harmonic dipole propagation model. This model allows for the propagation of the electromagnetic fields of any Hertzian dipole (horizontal or vertical, electric or magnetic) in a medium consisting of an arbitrary number of layers of arbitrary conductivity. Thus, it is well suited to handle propagation from the lithosphere through a layered seabed, ocean, and earth-ionosphere waveguide as well as scattering from select targets. The model is readily extensible to linear or areal distributed dipoles. Time-dependent problems are solved by Fourier analysis; the propagation code is used to develop a transfer function and the time series at the sensor is reconstructed from that and the time-dependent source. For more complex environments (beyond plane parallel layers), we use a suite of fully three-dimensional harmonic electromagnetic geophysics codes. These are likewise applied to time-dependent problems using Fourier analysis.
The electromagnetic propagation codes are augmented by several noise models, which together provide a complete testbed for performance analysis. The noise models include two geomagnetic noise models (based on empirical electric and magnetic field data), hydrodynamic noise models for surface and internal waves, and sensor noise models for electric and magnetic field sensors.
Deep Underwater Gravity Technology
The AUV-based Deep Water Gravity program (ADWG), seeks to put a specially modified gravimeter inside an autonomous underwater vehicle (AUV) and run it near the bottom of the ocean, in order to measure gravity as close to the source mass as possible, and obtain higher resolution than equivalent shipboard geophysical measurements.
ISL has teamed with Scripps Institution of Oceanography (SIO) to implement this technology, and test it in a deep-water Bluefin AUV, for a consortium of interested oil exploration companies. The initial sea-test occurred in May of 2008 and demonstrated operational feasibility of the concept. Subsequent laboratory and pool tests have concentrated on identifying and eliminating the various external and internal forces that contaminate the geologic gravitational signal with noise. We are zeroing in on our goal of creating a system with 0.1-mGal rms measurement noise. Once that is achieved, the ADWG system will be a useful and marketable oil exploration technique, particularly in hard-to-access and deep water global frontier regions.
ISL has developed a detailed model to simulate the gravity and tensor gradient components for an arbitrary spatial distribution of density anomalies. In addition, a series of filters has been implemented that allow all other components (including the tensor gradient) to be derived from the vertical gravity component.
Marine Electric Field Sensor System
ISL's innovative electric field sensor system provides an effective means for short range underwater surveillance in shallow water. The system combines proven underwater electrode technology, low-noise amplifiers, and a data acquisition system. The system is not affected by acoustic noise sources. Uses include:
- Underwater marine surveillance
- Harbor defense
- False alarm reduction
- Signature monitoring
- Sensor calibration
- Environmental noise monitoring
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Marine Electric Field Sensor Specification Sheet (205KB) |
Neurobiologically Inspired Networks
ISL has developed a novel, computationally efficient approach enabling the replication of the signal processing and control functions involved in complex neurobiological networks. Processing of sensory information and generation of control commands in the network is done with spikes produced by the neurons interacting through the synapses. The key element of our approach is the use of new phenomenological models of neurons and synapses derived in the form of a simple discrete-time algorithms (map-based models). These models are capable of replicating the important spike pattern characteristics of specific neurons, dynamics of synapses and the spatio-temporal patterns of network activity. We have demonstrated that our approach to the modeling of the lamprey Central Pattern Generator network enables real-time simulations of neuronal activity that controls swimming of biomimetic robot using a commercial floating-point DSP chip.
Long Wave Infrared Chemical Sensing Technology
A hyperspectral imaging system consisting of a rapidly tunable, room temperature quantum cascade laser coupled with a mid-IR camera constitutes an avenue not previously explored. The presence of chemical residues can be determined from the measured reflection spectra and overlaid on a mid-IR image. The system allows for standoff detection and contains signal extraction algorithms that aid in the detection of chemical residues. The system is based on a tunable mid-IR source that can be rapidly tuned to precise wavelengths. Using these sources at wavelengths corresponding to chemical absorption features and synchronized with thermal imaging cameras, chemicals can be detected on various types of surfaces. Using advanced detection algorithms and image processing, the location and type of chemical can be superimposed upon a thermal image enabling efficient detection and identification to occur.
Electro Optics Design and Testing
ISL has extensive experience in systems analysis, optical design, optical prototyping and optical test and evaluation. Previous projects have included non-coherent LIDAR prototype, free space laser communications design and build, x-ray plasma laser driver design and build, x-ray microscope design and prototype, high power diffraction limited DPSS laser design and build, diffraction limited telescope design and build, atomic line filter design and build, LWIR system design and prototype, as well as many custom optical lens designs and builds. The latest design tools such as MATLAB, MathCAD, SolidWorks, and ZEMAX are all used in the performance of these projects.
Ultra Narrowband Optical Filters
Atomic line filters operating at various wavelengths from the near IR to the near UV have been extensively studied, since they are at present the narrowest bandwidth optical filters available. Their narrow bandwidth and relatively high sensitivity make them extremely useful for detecting weak, narrowband radiation embedded in a large continuous background. There are several types ranging from active to passive, wavelength converters, imaging filters, and ionization filters. They have been used extensively in LIDAR systems and other laser applications. ISL personnel have extensive experience designing and implementing atomic line filters in a variety of applications and can perform system analysis, design, prototyping, and test of these novel devices.
Advanced Algorithm Development & Implementation
ISL prototypes advanced signal processing, simulation, and other systems engineering analyses in Matlab® and other environments. This development is conducted in a Matlab toolbox framework complete with configuration management and documentation. The software can be reused between projects or delivered to customers. As a part of the development, functions are implemented in compiled-code languages and used in Matlab via the Matlab External (MEX) interface. These MEX functions provide an environment for continuously testing both the Matlab and compiled-code implementations and facilitates the transition of the software to embedded signal processing applications. Applications include surface, airborne, and space-based sensors.
High Fidelity RF Sensor Modeling and Simulation
ISL provides a wide range of simulation and modeling services for analyzing RF sensors including radar and ELINT. ISL’s expertise and modeling tools are used to provide our customers with a cost-effective means of predicting real-world system performance without the need for costly hardware prototyping and data collection campaigns.
ISL's tools accurately model the effects of site-specific terrain, land cover, background/civilian targets, sensor-platform interactions and errors in the receive chain, and sensor motion (flexing, vibration, etc.). Thus, they are capable of providing the rigorous physics-based characterization of all the real-world effects that must be considered when designing and testing sensor signal processing algorithms.
The Splatter, Clutter, and Target Signal (SCATS) model is the main RF phenomenology engine that drives ISL's simulation tools. SCATS has been developed under a number of DARPA, Army, Navy, and Air force programs since 1989. It was one of the earliest site-specific radio frequency (RF) phenomenology analysis tools to provide an accurate characterization of complex RF environments. Uses of the model include system analysis, test planning, high-fidelity synthetic data generation, and signal processing algorithm development. The model provides characterization of target returns, direct path signal, ground scattered signal (clutter for radar), direct path signals from interferers, and ground scattered interference signals (hot clutter, splatter, or terrain-scattered interference).
Under the Knowledge-Aided Sensor Signal Processing and Expert Reasoning (KASSPER) program ISL used the SCATS model to deliver high-fidelity simulated radar data sets to support the needs of our DARPA/AFRL customer. The data sets were used by government and industry organizations to develop and validate advanced adaptive processing algorithms that improve GMTI radar performance in stressing environments. Numerous non-ISL open literature papers have reported results using these data sets.
Designing RF systems for military operations in urban terrain (MOUT) requires site-specific models of built-up areas. ISL has used the Wireless Insite REMCOM model together with ISL’s own high-fidelity modeling tools for urban sensing and geolocation applications. This model, extensively use by the cellular phone community for urban coverage analysis, incorporates ray tracing and uniform theory of diffraction and a site-specific city data base to make predictions of fast and slow fading, delay spread of signal multipath as well as specific calculations of individual multipath signals. Since future DoD RF Systems will likely have requirements driven by military operations in urban terrain (MOUT), such a modeling capability is an essential component of advanced RF system design and analysis.
Knowledge-Aided Signal & Data Processing
ISL has developed techniques and software that allow RF sensors to perform better by integrating databases of prior knowledge about the sensor operating environment. This includes databases of terrain heights, land cover type, descriptions of man-made structures, and ownship sensor data collected on previous passes. ISL’s techniques provide significantly improved data products relative to traditional statistical signal processing algorithms for sensors operating in challenging clutter environments.
Under the DARPA/AFRL KASSPER program, ISL developed a knowledge-aided signal processing technique termed "colored loading." It is based on a rigorous mathematical formulation that exploits environmental knowledge when processing the raw radar data and also offers a path for real-time implementation. It has been demonstrated to reduce false alarms by at least a factor of ten. The technique is applicable to ground, air, and space-based radar systems.
Passive RF Sensing
ISL maintains a Passive Coherent Location System (PCLS) test facility at our San Diego laboratory location. The facility is comprised of a rooftop antenna array, analog signal conditioning, and digital processing. The system is modular, configurable and programmable to satisfy customer target tracking objectives and the local radio frequency broadcast environment. Instead of using its own transmitter, this passive detection and tracking system processes common broadcast transmissions such as FM radio and television. The system is designed to track missile launches and has the capability to track aircraft and, in some cases, ground or sea-based moving targets. Our high fidelity simulation forecasts system performance, assists system configuration, supports development of novel radar modes, and assists in the data interpretation. The system has military, homeland defense, and commercial applications.
