N132-129 TITLE: Compact, Repetitive Pulsed Power Driver Design for Emerging High Power Radio Frequency Sources

TECHNOLOGY AREAS: Sensors, Electronics, Weapons

ACQUISITION PROGRAM: ONR Code 352: High Power Radio Frequency (HPRF) Basic Research

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop a high voltage, solid state, compact, repetitive pulsed power driver optimized for emerging high power radio frequency sources capable of high repetition rates, 10-100 kHz and above.

DESCRIPTION: A variety of high power radio frequency (HPRF) sources have been developed recently, including several novel, solid-state, compact sources that produce very high peak power levels (10s of MW with potential to GW). These HPRF sources have the potential to enable solutions for applications of interest to the U.S. Navy such as small vessel mounted and man-portable directed energy weapons. Substantial progress has been made to reduce the size, weight, and power requirements of these HPRF sources. However, less attention has been given to the pulse conditioning driver components crucial for operation of these devices. Pulsed power drivers are oftentimes significantly larger than the RF source itself. The current state of the art is primarily based on spark gap technology, which has inherent repetition rate limitations, and common topologies such as Blumleins, Marx generators or pulse forming networks which tend to be large and/or bulky. Additionally, these standard voltage multiplying circuits typically produce an output pulse with limited flexibility due to the inherent RC time constants of the fixed circuit elements such as capacitors and inductors. Advanced switching technologies can dramatically reduce the size of the driver elements, increase overall efficiency and improve performance parameters such as jitter which is critical in an arrayed system. For HPRF systems to become viable for more challenging employment options, pulsed power drivers must be developed that are just as compact as the RF sources they support. The goal of this research initiative is the development of a compact pulsed power driver (includes prime power, pulse conditioning driver, thermal management if required, and controls) for HPRF sources capable of 10�s of kHz repetition rates in burst mode for one minute or less, a prime power requirement of 5-25 kW, a volume of less than a half cubic meter, weighing less than 100 pounds, with an output power of 10�s of megawatts for a pulse of peak amplitude of 40-50 kV and pulse-width of 5-500 ns. Given the ongoing development of these HPRF sources, driver flexibility will also be a key factor as more flexible driving pulses may significantly improve the RF output from the source. This flexibility could take the form of, for example, variable output characteristics or modularity for driving multiple HPRF source arrays. The pulsed power driver therefore needs to provide a high voltage pulse with varying rise time, pulse width and peak amplitude to allow full exploration of the capabilities of the RF sources of interest. This pulse waveform shaping flexibility is difficult to achieve with standard lumped element capacitive discharge circuits, so a novel pulse conditioning driver design will likely be required.

PHASE I: Conceptualize, design, and model key elements for an innovative compact, repetitive, pulsed power driver for HPRF sources. The design should establish realizable technological solutions for a device capable of producing 5 to 50 nanoseconds pulses at 30 to 50 kV of varying shapes, repetition rates of 10�s of kHz in burst mode for up to 1 minute, and a minimum peak output power greater than 5 kW contained in a one cubic meter volume weighing 250 lbs or less with a predicted lifetime of 10^7 shots. The proposed design should be an 80% complete solution. The design should include circuit modeling and analysis of various driver output waveforms and how those waveforms could impact or improve RF source output and/or efficiency. Additional modeling and simulation should be performed to determine the driver efficiency, prime power and thermal management requirements. An overview of the current state of the art for each of the key driver elements along with manufacturer information should also be provided, focusing on solid state switching components required for this application. Cost analysis as well as material development should be included so as to ascertain critical needs not yet fully developed or readily available given current technology.

PHASE II: Construct and demonstrate the operation of a laboratory scale, breadboard HPRF pulsed power driver prototype based on Phase I work. The prototype does not have to explicitly meet the size or weight requirements, but should meet the other performance specifications, while being as compact as possible. The driver should also be capable of operating in a dry outdoor environment and be environmentally enclosed. Data packages on all critical components will be submitted throughout the prototype development cycle and test results will be provided for regular review of progress. The prototype should have the flexibility to produce various output waveforms and analysis of RF source (or dummy RF source) response to these waveforms should be conducted to help establish optimal waveform parameters (i.e. rise and fall time, pulse width). The use of actual hardware and empirical data collection is expected for this analysis. A refined design package should also be submitted that meets the objective size of half a cubic meter and weight of 100 lbs. or less and be capable of 10s to 100�s of kHz operation in burst mode for up to one minute and provide output pulses of a minimum of 20 kV with a goal of 50 kV.

PHASE III: Finalize the design from Phase II and construct and demonstrate a brassboard HPRF driver prototype optimized for a specific RF source. The final design should be based on the RF response and waveform analysis data collected during Phase II. The RF source for which the driver is to be optimized for may be designed/built by the company and/or provided by a sub-contractor. If the company does not have information on the candidate RF source technology, government furnished information will be provided. The subsequent prototype should represent a complete solution and will be tested to ensure it meets all performance specifications. Data packages on all critical components and subcomponents will be submitted throughout the development cycle and test results will be submitted for regular review of progress. The prototype should be ruggedized for, at a minimum, testing in a shipboard environment across a temperature range of 0 to > 70 degrees, MIL-STD shock and vibration and be environmentally enclosed.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Potential commercial applications include a variety of communications, sensor and medical applications requiring compact, high power RF systems.

REFERENCES:
1. J. Gaudet, E. Schamiloglu, J.O. Rossi, C. J. Buchenauer, and C. Frost, "Nonlinear Transmission Lines for High Power Microwave Applications � A Survey," IEEE Proc. IPMHVC 2008, pp. 131-138.

2. J. W. Braxton Bragg, J. Dickens, and A. Neuber, "Investigation Into the Temperature Dependence of Ferrimagnetic Nonlinear Transmission Lines," IEEE Transactions on Plasma Science, Vol. 40, No. 10, pp. 2457-2461.

KEYWORDS: Pulsed power driver, pulse forming line, solid-state, high power radio frequency / microwave, directed energy weapons

** TOPIC AUTHOR (TPOC) **

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