Description:
OBJECTIVE: Develop a High Frequency (HF) Time Difference of Arrival (TDOA) radio geolocation remote sensor system that uses a physically small antenna. The High Frequency remote sensor system will be capable and effective at providing accurate geolocation coordinates on High Frequency radios using NVIS (Near Vertical Incidence Skywave) communication mode. DESCRIPTION: Geolocation of High Frequency (HF) Radios using Near Vertical Incidence Skywave (NVIS) mode propagation with a remote sensor system using TDOA (Time Difference of Arrival) technique is needed for providing force protection for an area of operations. Innovation is required in developing TDOA processing of HF NVIS signals. There are many challenges to be met and problems to be solved to select and verify the same wave point on the received signal and then accurately time stamp the same point on the wave and then an algorithm to process the time stamped signal to provide a line-of-bearing. Multiple lines-of-bearings must be processed to determine accurately the geolocation of the radio. The processing of the time stamped data must be processed with the uniqueness of the HF ground-wave taken into account. The system must isolate the ground-wave from the direct-wave and sky-wave. Primary requirement of this research task is to provide solutions to these challenges in the form of a low cost remote sensor system that provides persistent surveillance of an area to be monitor for extended periods of time. Research and development efforts have been completed in the past using aircraft as TDOA platforms to provide LOB (lines-of-bearing) on ground based HF emitters on direct-wave propagation. Much work on ground base systems have be completed in the past using very large antenna arrays to do single station location of HF skywave mode communications but these are ineffective and not accurate against NVIS mode communications. Large DF antenna arrays have been used in single station location system but these are too large to be used as a deployable force protection ground based system. None of these approaches satisfy the requirements for deployable force protection and persistent surveillance for imminent threat warnings or detection and geolocation of HF interferers for spectrum management purposes. Capability to get LOB and geolocation of HF radios using NVIS communications links is desired for remote sensors providing force protection over the area of operations. Ground remote sensors are the best solution for area of operation deployable force protection. These remote sensors must be easy to deploy and low cost given the installation in remote locations that makes the sensor vulnerable to be lost. This research effort would use innovative control and data processing of a remote wideband spectrum surveillance receiver system with organic precision time stamping of RF events. The research would involve developing a processing system by means of TDOA technique applicable to HF NVIS communications to process the data collected by the wideband receive system to locate HF transmitters. Ground based remote sensor geolocation of NVIS emitters using a TDOA algorithm is the primary research area. Man power and support is a major factor in the research and design approach of the sensor system. Minimum personnel time to deploy, operate and maintain the system is a key goal for this sensor system. The sensor system must not be dependent on availability of commercial or generator power. It must use renewable power and be compatible with multiple power sources. PHASE I: Will consist of researching past approaches to using TDOA for geolocation of HF transmitters and provide a detailed design of a low cost ground based HF deployable remote sensor system. The sensor system must be easily deployed, use renewable power, data processor system, and software system that can be easily integrated into current geolocation systems. Data format must be compatible with deployable force protection situational awareness database system and other national database systems. The cost to build a demonstration system shall be provided and estimated cost to build six field evaluation systems. PHASE II: Develop a HF TDOA remote sensor demonstration system based on the detailed design presented during Phase I. Identify a test range and setup the demonstration sensor system collecting data needed to determine the accuracy, effectiveness, and viability of the sensor system. An operational field test report is to be provided with data, analysis, and evaluation of the sensor system. The report shall provide lifetime cost analysis of the sensor system and manpower required to deploy and operate the sensor system. PHASE III: Fully develop the low cost, ground based, easily deployable, HF TDOA technique, remote sensor system. U.S. Army, DOD, FAA and FCC Uses: Deployable Force Protection, Persistent Surveillance, Imminent Threat Warnings, Remote Sensor System, Spectrum Management Commercial Uses: Detection and location of HF communications interferers
