Study of Lower Atmospheric Ducts, Air-Sea Interaction, Turbulence, and Electromagnetic Propagation Using a Phase-Coherent Vertical Array and a Tethered-Drone
Abstract
The previous Lower Atmospheric Propagation (LATPROP) measurement system was built at the Ohio State University, Atmospheric and Oceanographic Electromagnetics and Marine Systems Laboratory using four different grants (two of which were previous DURIPs) of Dr. Yardim and includes:1.LATPROP-UWB: 2-40 GHz ultra-wideband propagation loss measurement system for remote sensing of atmospheric refractivity.2.LATPROP-RADAR: X-band 25 kW commercial off the shelf (COTS) marine radar heavily modified as a software-defined, coherent-on-receive radar with a large, high gain dish antenna for refractivity-from-clutter, sea surface clutter, radar performance studies.3.LATPROP-DRONE: An initial prototype Aero Systems West hexacopter with 50 lbs payload capacity carrying both meteorological and custom built EM receiver payloads for the study and direct/indirect measurement of lower atmospheric conditions for EM propagation. The system can be modified to work from 100 MHz-6 GHz.4.Prototype 4-channel phase-coherent system to be used as a testbed for a large 12-element fully coherent system.Proposed is the upgrade and extension of the LATPROP measurement system that was successfully deployed during the Coupled Air/Sea Processes and Electromagnetic ducting Research (CASPER) East and West Campaigns conducted in 2015 and 2017, in addition to the deployments during the Coastal Land-Air-Sea Interaction (CLASI) Campaign conducted from June-October 2021. The proposed upgrades include 2 new subsystems that will be built based on the lessons learned during previous deployments from the prototype drone and the small 4-channel system.The prototype drone system deployed in 2021 for the first time collected narrowband data at 5.9 GHz from 3 bouy transmitters at different ranges. We were able to collect vertical EM signal variation from 5-250 m altitudes while simultaneously collecting MET data that gives the index of refraction as a function of height. The CLASI deployments proved the drone is acheap, easily-deployed, highly mobile system that can collect unique data from hard-to-reach regions such as up to 250 m high to characterize the lower atmospheric propagation conditions that can previously only be collected via expensive platformssuch as helicopters. Continuous up-down measurements showed that the system was able to measure vertical modified refractivity profile (M-profile) to a high accuracy and simultaneously capture the spatial and temporal variations in ducting conditions. The proposed LATPROP-Tether Drone system will expand the capabilities of the current drone system by removing the flight time and power limitation currently affecting the drone and its payloads. The data can be also sent real time to the ground observer station. With this improvement, the new system will be able to measure for longer periods of time since power will be continuously supplied by the tethering station. Further study of drone propeller effects on the MET data can also be studied in detail.Rapid development and commercialization of software-defined radio based EM receivers allowed for the first time a way to measure phase-coherent EM signals in a cheap, affordable and accurate way in the last decade. Our prototype 4-channel system showed it is possible to measure phase-coherent EMdata accurately and use this for duct estimation and study of lower atmospheric propagation. Current proposal also includes a 12-channel fully phase-coherent EM receiver array capable of measuring signals up to 6 GHz. This will not only enable us to study in detail the problems with coherence when a large number of SDRs are connected to each other but also test improved duct estimation techniques that take advantage of the extra phase information.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 12, 2023
- Source ID
- N000142312220
Entities
People
- Caglar Yardim
Organizations
- Office of Naval Research
- Ohio State University
- United States Navy