HF Digital Receiver

ABSTRACT: In the past, systems such as the Navy"s Relocatable Over the Horizon Radar (ROTHR) used analog HF receivers. Those receivers were expensive to manufacture, and their performance varied over time and temperature. Advances in digital signal processing and integrated-circuit performance have made fully-digital versions of the HF receivers technically viable and cost-effective. The objective of this project is to design and prototype an HF digital receiver (HFDR) for the next generation OTHR. In Phase I, the high level design of the HFDR was completed, and significant progress was made in the detailed design of the digital down converter (DDC) and the analog front end (AFE). A fully-functional HFDR DDC that meets project performance specifications was implemented, and an AFE design with excellent noise figure and dynamic range performance was completed. In Phase II we will design and build high-performance HFDR prototypes that meet the program objectives and that can be easily transitioned to production. Three prototypes will be created: a COTS prototype for quick delivery, a ruggedized prototype for extended field testing, and a final pre-production prototype. Each prototype will provide an opportunity for evaluation and tuning of the technical specifications and interfaces to meet program objectives. BENEFIT: The HF digital receiver proposed in this Phase II project will provide a significant performance benefit to the next generation OTHR system compared to current analog designs. In particular, the HFDR"s high dynamic range will improve the system"s ability to detect targets in the noisy, high clutter HF environment. Also, its simultaneous acquisition of wideband and narrowband data supports multiple channel monitoring and instant channel switching. The same HFDR design is suitable for other HF, VHF, and UHF radar systems that use simultaneous reception from multiple antenna elements, such as phased array or MIMO systems. It also has potential applications in the commercial, amateur radio marketplace, where it can simultaneously monitor multiple, widely spaced frequencies and provide instant frequency switching, a relatively new and desirable feature in that market.