KEYWORDS: Radar, Signal to noise ratio, Standoff detection, X band, Explosives, Acoustics, Unattended ground sensors, Ground penetrating radar, Improvised explosive device detection, General packet radio service
AKELA Inc. is a small company located in California that specializes in developing unique radar systems for the DoD and other government customers. Most of our research is focused on standoff through the wall (STTW) sensing and ground penetrating radar (GPR) over an ultra wide frequency range. Our systems range in size from a briefcase up to a truck-mounted antenna array. While many of the systems are monostatic, AKELA has also built distributed systems for perimeter monitoring and bistatic RCS measurements. This presentation will give an overview of AKELA’s current and past research programs in the STTW and GPR fields.
Proc. SPIE. 9456, Sensors, and Command, Control, Communications, and Intelligence (C3I) Technologies for Homeland Security, Defense, and Law Enforcement XIV
KEYWORDS: Target detection, Radar, Signal to noise ratio, Digital signal processing, Homeland security, Detection and tracking algorithms, Calibration, Signal processing, Ka band, Environmental sensing
Footprint and human trail detection in rugged all-weather environments is an important and challenging problem for perimeter security, passive surveillance and reconnaissance. To address this challenge a low-cost, wideband, frequency-modulated continuous wave (FMCW) radar operating at 33.4GHz – 35.5GHz is being developed through a Department of Homeland Security Science and Technology Directorate Phase I SBIR and has been experimentally demonstrated to be capable of detecting footprints and footprint trails on unimproved roads in an experimental setting. It uses a low-cost digital signal processor (DSP) that makes important operating parameters reconfigurable and allows for frequency sweep linearization, a key technique developed to increase footprint signal-to-noise ratio (SNR). This paper discusses the design, DSP implementation and experimental results of a low-cost FMCW radar for mobile footprint detection. A technique for wideband sweep linearization is detailed along with system performance metrics and experimental results showing receive-SNR from footprint trails in sand and on unimproved dirt roads. Results from a second stepped frequency CW (SFCW) Ka-band system are also shown, verifying the ability of both systems to detect footprints and footprint trails in an experimental setting. The results show that there is sufficient receive-SNR to detect even shallow footprints (~1cm) using a radar based detection system in Ka-band. Field experimental results focus on system proof of concept from a static position with mobile results also presented highlighting necessary improvements to both systems.
Interest in methods for obtaining surveillance information through walls has been increasing for both domestic and military security applications. While our previous through wall sensor development activities have demonstrated acceptable imaging performance by synthesizing a large antenna aperture from a portable, collapsible antenna array, these operational constraints have driven AKELA to a concept of operation where images are created by a distributed array of individual sensors. Each sensor is a high range resolution radar that can be either fixed in place or carried by an individual. The sensors are connected with a wireless communication network that distributes timing and control information, receives data, determines sensor location, and fuses the data from each sensor to generate imaging and motion detection information.
We have developed a frequency agile radar operating between 500 MHz and 2 GHz that is the sensor element in our networked concept. Its performance has been tested on a variety of wall materials. Results of these tests show that this new radar has the capability to detect the breathing response of a stationary individual through a reinforced concrete wall at a distance of 6.5 meters.
With sponsorship from the National Institute of Justice and the Air Force Research Laboratory, AKELA developed a brassboard imaging radar suitable for portable, fixed in place operation with a maximum range of 100 meters. Experiments demonstrated that the radar detects an individual at a range of 12 meters through three internal walls, at 40 meters through dense foliage, and forms images through reinforced concrete walls. We found, however, that to be operationally practical, it would be necessary to increase the speed of the radar and display processing, and to develop a more robust imaging antenna array.
A second generation radar imaging system is currently under development. The radar is frequency agile operating between 500 MHz and 2 GHz, has a maximum range of 250 meters, forms images at 10 frames per second, and uses a random array of antennas to improve image resolution and reduce ghosts.
Both concealed weapons detection and through the wall surveillance are significant problems for both law enforcement and military personnel. While on the surface it would appear that these two problems are unrelated technologically, they do, in fact, share some common ground. A concealed weapon acts as resonant object, exhibiting electromagnetic resonance peaks at frequencies characteristic of the weapon's major dimensions. For handguns the frequency range of interest lies approximately between 450 MHz and 2 GHz. As it turns out, this is also a region over which many common building materials are largely transparent. As part of grant 97-IJ-CX-K013 from the National Institute of Justice, AKELA, Inc. has developed a stepped-frequency, CW radar that covers this frequency range. The radar is digitally synthesized and controlled and has a range resolution of approximately 4'. Digital waveform control gives the radar the ability to avoid interference with other electronic devices, to tailor data collection for signal processing requirements, and to change its sweep time in response to operational requirements. AKELA has developed a brassboard concealed weapons detector that uses this radar. A through the wall imaging system that uses the radar is currently in development under AFRL Contract F30602-00-C-0205.
Concealed weapons pose a significant threat to both law enforcement and security agency personnel. The uncontrolled environments associated with peacekeeping and the move toward relaxation of concealed weapons laws here in the U.S. provide a strong motivation for developing weapons detection technologies which are noninvasive and can function noncooperatively. Existing weapons detection systems are primarily oriented to detecting metal and require the cooperation of the person being searched. The new generation of detectors under development that focuses primarily on imaging methods, faces problems associated with privacy issues. There remains a need for a weapons detector which is portable, detects weapons remotely, avoids the issues associated with privacy rights, can tell the difference between car keys and a knife, and is affordable enough that one can be issued to every peacekeeper and law enforcement officer. AKELA is developing a concealed weapons detector that uses wideband radar techniques to excite natural electromagnetic resonances that characterize the size, shape, and material composition of an object. Neural network processing is used to classify the difference between weapons and nuisance objects. We have constructed both time and frequency domain test systems and used them to gather experimental data on a variety of armed and unarmed individuals. These experiments have been performed in an environment similar to the operational environment. Preliminary results from these experiments show that it is possible to detect a weapon being carried by an individual from a distance of 10 to 15 feet, and to detect a weapon being concealed behind the back. The power required is about 100 milliwatts. A breadboard system is being fabricated and will be used by AKELA and our law enforcement partner to gather data in operationally realistic situations. While a laptop computer will control the breadboard system, the wideband radar electronics will fit in a box the size of a CD ROM drive of a computer.
AKELA has developed a software tool which uses a systems analytic approach to model the critical processes which support the acquisition of biological and chemical weapons by terrorist organizations. This tool has four major components. The first is a procedural expert system which describes the weapon acquisition process. It shows the relationship between the stages a group goes through to acquire and use a weapon, and the activities in each stage required to be successful. It applies to both state sponsored and small group acquisition. An important part of this expert system is an analysis of the acquisition process which is embodied in a list of observables of weapon acquisition activity. These observables are cues for intelligence collection The second component is a detailed glossary of technical terms which helps analysts with a non- technical background understand the potential relevance of collected information. The third component is a linking capability which shows where technical terms apply to the parts of the acquisition process. The final component is a simple, intuitive user interface which shows a picture of the entire process at a glance and lets the user move quickly to get more detailed information. This paper explains e each of these five model components.