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Low Power Multi-Channel RF and Digital GPS Anti-Jam ASIC


OBJECTIVE: Develop and demonstrate a very small low power integrated multi-channel RF and digital anti-jam (AJ) ASIC for integration within SWaP constrained military GPS receivers and capable of being interfaced to a small multi-element antenna array. DESCRIPTION: Military global positioning systems (GPS) receivers require protection against all forms of interference, intentional and unintentional. Controlled Reception Pattern Antennas (CRPAs) and associated Antenna Electronics (AE) have been used successfully on numerous platforms to form nulls in the direction of interference signals while maintaining enough gain toward satellite signals to support GPS navigation. Nulling and beam steering electronics are in use today to interface CRPA/AEs to military GPS receivers and provide improved signal reception in an interference environment. Although these electronics provide excellent performance, they do so at a significantly increased size, weight, power and cost (SWaP-C) to the GPS integration on the platform. Advances in RF and digital packaging technologies as well as the continued advance of Field Programmable Gate Arrays (FPGAs) to support rapid prototyping and development are enabling various components to be combined onto a single Application Specific Integrated Circuit (ASIC). The goal of this program is to integrate multi-channel RF front-end and Digital AJ processing circuitry onto a single ASIC and interface this device with next generation military GPS receivers. The ASIC must accept signals directly from CRPA, amplify, down convert and filter the RF antenna signals, perform A/D conversion, and apply digital signal processing algorithms to simultaneously reduce or eliminate interference signals in the 24 MHz bandwidths centered at the L1 (1575.42 MHz) and L2 (1227.60 MHz) while still passing GPS signals in the L1 and L2 24 MHz bandwidths to support acquisition, tracking and navigation. Basic objectives for the ASIC include:size suitable for integration within a SWaP-constrained GPS receiver (e.g., handheld), accept RF inputs from a minimum 2-element (Objective: 4-element) CRPA simultaneously at L1 and L2 GPS frequencies, provide at least 30dB of anti-jam protection for up to 2 (Objective: 3) 24MHz wide gaussian noise interference sources (assume well matched CRPA RF antenna outputs), successfully pass GPS M-code signals that can be used by modernized GPS receiver for navigation, and consume a total power of 1 Watt or less. Approach encourages technology development practices that eventually result in improved performance and lower cost and size for commercial products. The Government will provide a full set of antenna array data to support the development. PHASE I: Review of AJ GPS requirements, assess CRPA data, identify GPS receiver interface requirements. Trade study of potential RF design and AJ processing algorithms as well as a recommended solution. Preliminary multi-channel RF-Digital architecture including RF downconversion, filtering, A/D conversion and AJ signal processing. Preliminary simulation and verification of design in prep of final design. PHASE II: Objective is to fabricate an ASIC and test fixture capable of demonstrating performance. Finalize ASIC design and layout, and demonstrate performance through simulation and/or prototyping. Develop a test plan to verify standalone performance and when interfaced to a GPS receiver. Test and evaluate the ASIC to show basic functionality. Deliver the ASIC and test fixture for additional government test and evaluation. Document design and test results in a final report. PHASE III: Technology developed will expand current application of GPS AJ technology. Use of state of the art technologies that shrink the SWaP-C may help control cost of future civilian and military GPS receivers operating in interference environments. REFERENCES: 1. Siferd, R.,"Ultra-low SWAP Anti-Jam GPS Receiver Technology", JNC 2011. 2. Jarmale, N. B.,"Next Generation SWAP-Optimized Secure Military GPS Receivers", JNC 2011. 3. Jarmale, N. B.,"Integrated SWAP-Optimized High-Performance Anti-Jam SAASM GPS Receiver", JNC 2011. 4. Author unknown,"How the Army Uses Embedded GPS for Combat Service Support in the Movement Tracking System (MTS)", Pathfinder Newsletter, Volume 14, Issue 3, July, 2007.
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