Atindra K. Mitra

Low-Cost Position-Adaptive UAV Radar Design with State-of-the-Art COTS Technology

A COTS-based design for a monostatic position-adaptive radar concept is presented. The development and design effort is focused on a test experiment where a onboard radar-based instrumentation system allows a mini-UAV helicopter to hover back and forth in front of two large (side-by-side) “building-type” structures. Under this concept, the “smart” or “robotic” mini-UAV helicopter “position-adaptively” converges to a location between the two “building-type” structures in order to interrogate an object-of-interest that may be located between these “building-type” structures. Design issues with regard to major sub-systems and interfaces between these sub-systems are discussed. Applications for this type of system include intelligence gathering from indoor and outdoor urban environments and underground facilities via deployment a tier of position-adaptive mini-UAV’s.

Ultra-Wideband Signal Propagation Experiments in Liquid Media

Ultra-wideband (UWB) signals exhibit different characteristics upon propagation through matter compared with narrow-band signals. The latter keeps a sinusoidal shape during different forms of signal propagation. The behavior of narrow-band signals does not apply to UWB signals in many cases. Presently, the possibilities for development of UWB signaling technology remain largely unexplored. Few applications have been developed due to strict regulations by the Federal Communications Commission (FCC). In this paper, we describe a series of experiments that have been carried out to determine the behavior of UWB signals and their properties. A transverse electromagnetic (TEM) horn antenna has been made for radiating UWB signals. A procedure for propagating UWB signals through a liquid medium of given salt concentration has been demonstrated, providing a basis for studying UWB signal propagation in biological matter. A new pulsewidth definition was adopted, which is suitable for propagated UWB signals.

Rank-order filters for FOPEN target detection

Issues associated with the radar detection of military targets that are concealed or camouflaged by forest clutter are described. The specific sensor platform can be categorized as an ultrawideband (UWB) foliage penetration (FOPEN) synthetic aperture radar (SAR). The discussion illustrates the fact that many contemporary approaches to FOPEN target detection are computationally intensive and/or require the implementation of elaborate training procedures. Alternative approaches, based the application of a set of simple rank-order filters (alternately known as order statistical or L filters), are presented. Initial results indicate impressive performance levels (in terms of probability of detection as a function of false-alarm rate) with respect to baseline constant false-alarm rate computations. A number of avenues for future investigations are cited.

Collision-avoidance radar for bicyclist and runners

This paper provides a summary of the analysis and design process with respect to the development and prototyping of a Bicycle Radar for a Senior Capstone Project at Wright State University in collaboration with the Air Force Research Laboratory Sensors Directorate. The basic radar technology adopted for this project is a commercial integrated (miniaturized) K-band FMCW Monopulse Module that is recently designed for future Intelligent Automotive Cruise Control Applications. The design documentation, preliminary test outputs, and discussions within the sections of this paper describe a number of novel features of this Bicycle Radar Design including the methodology for overlaying the K-band range-angle data onto streaming video on the iPhone. Additional discussions pertain to radar waveform generation, control, and processing. A section on potential follow-on activities as well as a discussion on technology options and applications of the resulting system concept is also provided.

RF emitter localization with Position-Adaptive MAV platforms

This paper provides a discussion and a summary of the latest results on a novel sensor-node based approach to emitter localization denoted as Position - Adaptive Direction Finding (PADF). PADF is based on the formulation and investigation of iterative path-loss based (i.e. path loss exponent) metrics estimates that are measured across multiple platforms in order to robotically/intelligently positionally adapt (i.e. self-adjust) the location of each platform. We demonstrate that this approach shows potential for accurate emitter localization in challenging embedded multipath environments (i.e. urban environments).

Sensor agnostics for networked MAV applications

A number of potential advantages associated with a new concept denoted as Sensor Agnostic Networks are discussed. For this particular paper, the primary focus is on integrated wireless networks that contain one or more MAVs (Micro Unmanned Aerial Vehicle). The development and presentation includes several approaches to analysis and design of Sensor Agnostic Networks based on the assumption of canonically structured architectures that are comprised of lowcost wireless sensor node technologies. A logical development is provided that motivates the potential adaptation of distributed low-cost sensor networks that leverage state-of-the-art wireless technologies and are specifically designed with pre-determined hooks, or facets, in-place that allow for quick and efficient sensor swaps between cost-low RF Sensors, EO Sensors, and Chem/Bio Sensors. All of the sample design synthesis procedures provided within this paper conform to the structural low-cost electronic wireless network architectural constraints adopted for our new approach to generalized sensing applications via the conscious integration of Sensor Agnostic capabilities.

Theoretical radar-doppler models for pivoting mechanical and biological objects-of-interest

A set of approximate theoretical equations for the Doppler response of monostatic radar signals due to slowly pivoting objects are derived. The treatment is based on physical models extracted from the mechanical engineering community. Potential applications include analysis of load-based vehicle classification and detection of biological movements such as human joint rotations. Several example calculations are presented based on the resulting theoretical formulas. These examples include Doppler calculations for notional first-order vehicle suspension models and first-order human joint (arm/leg) rotation models. Each set of example calculations includes two sets of notional radar parameters in order to provide insight into potential Doppler pivot detection capabilities as a function of basic radar parameters such as frequency and PRF (pulse repetition frequency).

Multitone radar design using software radio components

Recent developments in communications and RF technology have enabled system concept formulations and designs for low-cost radar systems using state-of-the-art software radio modules. One of the major benefits of using these RF communications products is the potential for generating frequency-agile waveforms that are re-programmable in real-time and potentially adapt to a scattering environment. In addition, recent simulation results [1] indicate that this type of system enables the development and implementation of multi-function RF systems that yield good performance within embedded shared-spectrum environments. This paper investigates the design and implementation of software radar systems via implementation of commercially available software radio modules. Specifically, the potential for developing alternative multi-tone radar systems that provide significant levels of information with respect to embedded indoor scattering environments is discussed. This approach is developed via the transform domain waveform synthesis/design and implementation of OFDM (Orthogonal Frequency Domain Multiplexing) waveforms and shows good potential for the future development of cooperative multi-function RF systems.

Position-adaptive scatterer localization for radar imaging applications

Position-Adaptive Radar concepts have been formulated and investigated at the AFRL within the past few years. Adopting a position-adaptive approach to the design of distributed radar systems shows potential for the development of future radar systems that function under a variety of new and challenging environments. Specifically, we investigate notional control geometries and trajectories for multi-platform SUAV applications by integrating additional electromagnetic scattering-based metrics within more generic overall objective functions for multi-SUAV controls systems. We show that the formulation of these new categories of objective functions lead to realizations of multiplatform SUAV trajectories that position adaptively converge to a set of RF leakage points. After position-adaptive convergence to a set of leakage points, we show that an embedded scatterer (i.e. a metal cylinder) can be imaged by applying radar processing techniques derived for sparse apertures.

Leakage signal analysis for position-adaptive UAV radar applications

The results of numerical electromagnetic simulation and analysis of a set of positive-adaptive UAV radar signals are presented. These signals are simulated via the modeling of materials that enclose “building-type” structures with a series of connected dielectric materials. For example, windows, walls, and doors are each modeled separately by a combination of suitable material properties. Signals from objects that are embedded within these “building-type” structures are also simulated via the development and application of appropriate geometrical and materials models. Analysis of the resulting simulated “leakage signals” that penetrate the surfaces of these “building-type” structures and are backscattered from embedded objects within the indoor environment back to the simulated outdoor environment are presented. The results of a signal analysis are presented in two categories. The first set of results illustrates signal trends that can be exploited by “position-adaptive” mini-UAVs to isolate effective “leakage points” in “building-type” structures. The second set of results illustrate signal trends from embedded objects after a particular “position-adaptive” mini-UAV has converged to a “leakage point.”