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High Power Microwave (HPM) Solid State Amplifier Topologies


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Directed Energy (DE); Microelectronics The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop a radio frequency (RF) Solid State Power Amplifier (SSPA) topology specific to high power microwave (HPM) applications for use either as a stand-alone source or in an array, capable of generating a variety of waveforms while exploring the trade-off between power and bandwidth. Proposed solutions could cover pulse widths ranging from nanosecond to microseconds. Frequency interests span L, S, C, and X band SSPA topologies. DESCRIPTION: Commercially available solid state RF power amplifiers (PAs) are designed to meet the widest breadth of application and primary market needs. This involves a tradeoff between power, duty factor, efficiency, cooling requirements, lifetime, and band width. Potential consequences of this tradeoff are connector loss, higher than necessary parasitics, poor volumetric power density, and very low or high instantaneous bandwidth. A PA topology optimized for HPM applications would first optimize power coupled to a radiated antenna while maintaining the best possible values for other characteristic parameters. Thus, the goal of this SBIR topic is to consider design tradeoffs associated with maximizing power. A possible approach might be to sacrifice linearity to maximize power. Harmonic generation is of less importance as long as the total energy consumed by harmonics is less than 10% of the total output power. Noise figure is not important as long as total noise power is not a significant fraction of power out. What are the tradeoffs involved with PA input/output and source/ load impedances (determined by stability and power/efficiency requirements) on maximizing power out? While efficiency, duty factor, and lifetime are ultimately important for HPM applications, it is likely that they are not as severe as the requirements levied by most Commercial-off-the-Shelf (COTS) applications. The goal of this SBIR topic is to develop a new amplifier topology, suitable for HPM applications, that will be built and tested, informed by all the tradeoffs discussed above. Since this SBIR topic is examining solid state amplifier for both stand alone and array concepts, the tradeoff between maximizing power out and minimizing jitter and phase noise is also of interest. Instantaneous bandwidth is at the discretion of the proposer. Two possible realizations are of interest: First, a very narrow but tunable instantaneous bandwidth for single or swept frequency applications. Second a very wide instantaneous bandwidth for extremely short pulses or multiple simultaneous frequencies. Both may be applicable to frequency hopping applications. The tuning time for the center frequency of the narrow instantaneous bandwidth systems should be at or better than state-of-the-art. The wide instantaneous bandwidth system should have a minimum bandwidth of 1 GHz. It is also desirable to be able to tune the center frequency of the wide band system. While modifications of existing power amplifier class types are acceptable, new amplifier class types and/or die level design, specific to HPM amplifier needs, are also acceptable for consideration. Key Performance Metrics/Goals: The performance goals listed below define the outer edge of the desired outcome and are shown as an example specific to a nominal 2GHz center frequency; however, areas of interest span L, S, C, and X band SSPA topologies, which are encouraged. It is not expected that the topologies will meet all the design criteria. The topology’s ability to meet the performance characteristics should be shown on a radar chart, and will be judged based on how many of the performance parameters are met and what/how tradeoffs are made to achieve those parameters. 1. Saturated power out: 5 kw at 2 GHz 2. Volumetric power density: should be at least 2x better than the COTS equivalent 3. Narrow instantaneous bandwidth tuning: at or better than state-of-the-art for both speed and frequency span 4. Wideband bandwidth: greater than 1 GHz 5. Harmonic generation: less than 10% of total output power 6. Duty cycle: greater than 50% 7. Power Added Efficiency: greater than 70% 8. Output impedance: 45 to 55 ohms Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence Security Agency (DCSA), formerly the Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DCSA and ONR in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract. PHASE I: Conduct a feasibility study via simulation to assess the art-of-the-possible that balances the tradeoffs specified in the Description section. The feasibility study should investigate all known options that meet or exceed the minimum performance parameters suggested in the Description. The study should also address the tradeoffs and risks, in accordance with the level of innovation. Prepare a report to ONR on designs, simulations, and a Phase II testing plan. PHASE II: Develop scaled operational prototypes that demonstrate the concept(s) determined to be most feasible from the Phase I study. Provide an amplifier prototype; a report containing designs and testing results; and a Phase III plan for prototype evaluation. It is probable that the work under this effort will be classified under Phase II (see Description section for details). PHASE III DUAL USE APPLICATIONS: The prototype amplifiers will be incorporated into stand-alone HPM systems. Demonstrate amplifier lifetime operating into a matched load. Deliver an amplifier prototype and report containing designs and testing data. Detailed mission descriptions and effectiveness requirements will be addressed at a higher level of classification. REFERENCES: 1. R. S. Pengelly, S. M. Wood, J. W. Milligan, S. T. Sheppard and W. L. Pribble, "A Review of GaN on SiC High Electron-Mobility Power Transistors and MMICs," in IEEE Transactions on Microwave Theory and Techniques, vol. 60, no. 6, pp. 1764-1783, June 2012, doi: 10.1109/TMTT.2012.2187535 2. Browne, Jack. “Solid-State Amplifiers “Amp” Up the Power.” Microwaves & RF, Sept 10, 2018 3. “Multi-octave practical power amplifier realization using GaN on SiC.” IMS Montreal 2012. 4. Knowles, John and Holt, Ollie. “Technology survey, A sampling of power amplifiers for Electromagnetic attack applications.” Journal of Electromagnetic Dominance, June 2022. 5. Moore, Andrew and Reese, Elias. “RF Applications of GaN For Dummies.” John Wiley & Sons, Inc., Hoboken, NJ, 2015. KEYWORDS: High Power Microwaves, solid state, amplifiers, High Power Microwave, HPM, Solid State Power Amplifier, SSPA, radio frequency, RF
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