SBIR-STTR Award

Today, overwater emitter localization is performed using a combination of direction finding and/or multilateration. Both techniques inherently require multiple, well-separated receivers determine 3D emitter locations. The lensing effects of atmospheric ducting and surface reflections can potentially produce near-field phenomena whereby the electric fields received from an emitter is sensitive to the range to that emitter as well as the azimuth and elevation angles. The purposes of this Phase 1 proposal are (1) quantify the 3D location accuracies that may be possible in various propagation environments, including variable sea surfaces, a variety of weather, sea-states, and ducting conditions, various transmitter and receiver positions and for different configurations of receiver array element geometries and (2) make recommendations for a Phase II data collection architecture and overwater testing campaign with the potential of demonstrating the effectiveness of this approach.

During Phase I of this SBIR, Synoptic Engineering showed via analysis and simulation that accurate range, elevation and azimuth bearing estimation of non-stationary emitters is possible overwater from a single passive receiver. We propose to develop a receiver architecture prototype capable of implementing the localization methodology we have been developing under Phase I and to conduct an overwater evaluation using this prototype. The Synoptic Engineering team made significant progress towards the goals of the program during Phase I of the SBIR. The Phase II effort we are proposing attempts to minimize the risks associated with completing these goals and transitioning the technology to military applications and commercial capabilities\.

Applications:
We investigated propagation in evaporative ducts and surface ducts and formulated passive situational awareness and surface vessel tracking applications enabled by these conditions. LOCALIZATION METHODOLOGY: We developed a localization methodology that combines well-studied environmental models and sophisticated parabolic wave equation (PWE) propagation code with Bayesian estimation and supervised learning techniques and uses particle filters to track sequences of location estimates. RECEIVER ARCHITECTURE: Our proposed receiver architecture will provide the data collection requirements for the Phase II overwater evaluation of emitter localization. Our design features a novel shuttered slotted waveguide design which constructs subarrays out of waveguide segments with electronically shuttered radiator slots. This allows both polarization components of the electric field across the entire filled aperture to be scanned in microseconds. Precision manufacturing, a rigid antenna manifold and loopback calibration ensure the experimental control and data fidelity needed for conclusive overwater evaluation of emitter localization. We have carefully considered transition and commercialization in the design which uses low-cost waveguide and PCB components, is easily ruggedized and highly modular, allowing the number of subarrays and length of each subarray to be configured for a particular application. OVERWATER EVALUATION: Our proposed overwater evaluation will take place near San Diego in the spring and summer of 2022 where a rich variety of weather, ducting, and surface conditions will be encountered. We are proposing: (1) an initial non-stationary emitter test, (2) a three-month stationary emitter test between a fixed emitter on San Clemente Island and a stationary receiver on the coast near San Diego, (3) a second non-stationary emitter test, and (4) a final evaluation event with a GFE emitter. The multiple testing opportunities and extended fixed-site collection will allow us to observe variable surfaces, weather, sea-states and ducting conditions. Many weeks co-collecting NWP, local meteorological data and RF samples will provide a rich corpus of data for use with supervised learning.