Advanced Signal Processing

ISL’s team consists of creative scientists and engineers with both theoretical and experimental expertise in the areas of physics, geophysics, oceanography, signal processing theory and application, nonlinear modeling, electro optics, and optical communications. Current work includes research and development of electric field detection sensor systems, electromagnetic performance prediction modeling, deep underwater gravity technology, modeling of factional network dynamics, modeling and hardware implementation of neurobiologically inspired networks, and long wave infrared chemical sensing technology. Salt Water Test Tank, EMI Screen Room, Prototyping Facilities.


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.

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.

Spiking Neural Networks For Advanced Signal Processing

ISL is pursuing research into alternative massively parallel architectures using coupled nonlinear circuits to bypass fundamental processing speed and power limitations inherent with conventional digital circuitry (e.g. parasitic capacitance and transistor switching rates). Multi-layer networks can be designed to recognize spatial and temporal correlations in analog signals and thereby perform high-speed pattern recognition. The archetype nonlinear circuit is the artificial spiking neuron (or integrate and fire circuit). Multi-layer parallel networks of spiking neurons with inhibitory and excitatory connections are ideal for performing high-speed low power computation. Processing occurs in a hybrid digital/analog environment with the amplitude of spikes represented digitally and the timing of spikes indicating temporal correlations. In this environment, practical spiking neural networks exhibit 3 to 4 orders of magnitude less power consumption than their digital counterparts.

Concepts include spiking neural networks implemented to perform analog to digital conversion (ADC) at high-speed (multiple GHz) with large dynamic ranges (and spurious free dynamic ranges). These advances in ADC technology will enable corresponding performance improvements in modern radar systems including direct sampling of RF signals (bandpass architectures) and detection of reduced signature targets in heavy clutter and electronic counter measure environments.

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.

Fast Time Analysis 

ISL’s FTAS systems incorporate cost-effective, Commercial-Off-The-Shelf (COTS) hardware and software selected for faster data handling and increased storage capacity. They are becoming the standard for affordable, COTS-based, open architecture, post mission analysis systems for NATO and nations with maritime surveillance capabilities.

The FTAS provides the analyst with display and post processing tools for performing detailed analysis of both passive and active acoustic signals recorded from all sonobuoys deployed by operational Maritime Patrol Aircraft or Helicopters. The scalable system is based upon a flexible, high performance single chassis digital signal processor unit interfaced with multiple PC-based display and control workstations over a high speed local area network. The system accepts acoustic data in a variety of digital and analog inputs including STANAG 4283 compliant analog and digital formats.


 With the system’s flexible and intuitive graphical-user interface, including extensive analysis and display tools, tasks can be programmed to work within a number of well-known, commercial operating systems. The operator workload is significantly decreased through the application of massive acoustic data storage capabilities that allows the original data to be replayed once from the original tape or data source and then analyzed many times from memory at a variety of replay speeds. The open system architecture supports expansion and upgrades to accommodate additional or improved signal processing hardware, emerging operator analysis tools, and new requirements of the littoral or open ocean operating areas.

These systems are currently in operation supporting the Maritime Patrol Air (MPA) Navy communities in The Netherlands, France and Germany.

Fast Spectrum Analyzer

ISL has a long history of developing and producing a line of Fast Spectrum Analyzers operated by the Signal Intelligence (SIGINT) community to perform detailed analysis of Radio Frequency (RF) signals. Several thousand of the products have been produced over the years and are integrated into analysis laboratories and field sites operated by government agencies around the world.


The current version of this product operates in the spectrum between 10 Hz and 16 MHz and offers the operator an advanced signal processing, high-resolution display and a full set of advanced analysis features and tools.

Advanced Computing Platforms

ISL has software expertise and tools for exploiting emerging processing technologies such as graphical processing units (GPU) to meet the challenging computing requirements of modern sensor systems and simulations. ISL has demonstrated the use GPUs and other multi-core processors to speed up radar processing algorithms including space-time adaptive processing (STAP). ISL has established test bed hardware and software required for rapid prototyping of computational adjunct concepts.