Small Form Factor Airborne HF, VHF and UHF RF Direction Finding

ABSTRACT: The objective of this sequential Phase II SBIR is to deliver a Technology Readiness Level 6 (TRL-6) airborne HF, VHF and UHF RF direction finding system that is suitable for integration with SUAS and to demonstrate it in a realistic airborne environment against representative signals. This proposed effort leverages the completed Army Phase I SBIR that demonstrated accurate DF in field tests, and outperformed the incumbent system in all DF performance metrics. The field test scenarios were for man-borne, on-the-go, DF in the HF, VHF and UHF bands and used realistic geometries and radios. The antenna assembly of the ASI system was 1/26th the volume of the incumbent system. The incumbent was only capable of DF on VHF and UHF communications. Tactical RF Sensing at HF, VHF and UHF frequencies to detect, identify, characterize and locate emitters is a technology gap across all services for a broad range of applications. Delivering the objective of this sequential Phase II SBIR demonstrates the closure of that gap and has the potential to drive significant strategic and commercial value. BENEFIT: Airborne RF sensing depends on antennas that can be integrated into aircraft. Airborne antennas for HF, VHF and UH frequencies are a technology portfolio gap due to their size. Traditional antennas are typically 1/4 wavelength long, configured either in arrays or mechanically rotated and must be located outside the metal airframe. At VHF (100MHz) and HF (10MHz) frequencies, typical antennas are 2ft and 20ft. These sizes are challenging to integrate into aircraft and payload structures, particularly for small and/or expendable UAS. At higher frequencies (L, X and K bands) the antennas are smaller and the challenges of integrating them into airframes are substantially relaxed. The objective of this Phase II SBIR is to deliver and demonstrate small form factor HF, VHF and UHF RF DF systems suitable for integration with SUAS (e.g. Puma AE, Silver Fox) to locate RF emitters, including radar and communication equipment. Future roadmap developments can enable this technology to operate on the full spectrum emitters: RF operating bands can be increased to higher frequencies; operating range can be increased from close-in SUAS tactical ranges to stand-off range RF sensing; and, the addition of RF emitter functions can enable radar spoofing. These combinations of features drive significant strategic and commercial value.