SBIR-STTR Award

Advances in digital technology have made viable the migration of RF receivers from analog RF circuitry to digital gate arrays, with corresponding improvements in spectral accuracy, stability, reliability, and re-configurability. To realize a cost effective HF digital receiver, the challenges are: implementing computationally efficient digital filters under the constraint of limited hardware resources in Field-Programmable Gate Arrays (FPGA), managing the effects of quantization errors on dynamic range and linearity, designing a cost-effective, low-noise, and high dynamic range analog front-end, and determining optimal bandwidth for narrow band operation while keeping ENOB to at least 24 bits. Visor will adapt its existing UHF digital receiver for HF application by developing new digital down-conversion logical blocks in the FPGA and demonstrating the result on a Virtex-6 prototype board. Visor will also finalize the specification of an HF digital receiver for over-the-horizon radar (OTHR), and complete a detailed design package (schematics, FPGA code, and system wiring diagrams) for a cost-effective digital receiver. We will then assess the risk factors in making prototypes for integration into an operational testbed for Phase II. With extensive radar design experience, including operational digital receivers, Visor will design and demonstrate an optimal digital receiver for OTHR applications.

Benefit:
1. Evaluate and quantify the tradeoffs between performance and cost in HF digital receivers. 2. Identify opportunities for cost reduction in radar systems that use multiple antenna elements in an array. 3. Provide significant cost reductions for RF systems that operate in the HF band which will enable wider acceptance in commercial applications, such as remote sensing products.

Keywords:
Hf, Digital Receiver, Radar, Over The Horizon

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.

Keywords:
Digital Receiver, Software Defined Radio, Over The Horizon Radar, Othr, Hf, High Dynamic Range