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High Density Capacitors for Compact Transmit and Receive Modules


TECHNOLOGY AREA(S): Sensors, Electronics, Battlespace 

OBJECTIVE: Develop high-density capacitors that are robust, reliable, and highly compact for power conversion energy storage and filtering to reduce the size, weight, and manufacturing cost of transmit and receive modules. 

DESCRIPTION: Modern radar and electronic warfare (EW) transmitters are based on transmit and receive (T/R) modules as the fundamental building block. These T/R modules contain the radio frequency (RF) solid-state transmitter and receiver circuitry as well as control circuits and power converters. For example, future surface ship radars will contain thousands of these identical units, all housed in tightly packed racks, right behind the antenna array “ that is, high in the deck house where space and weight is at a premium. Even more significantly, the hundreds of thousands of T/R modules to be purchased over the life of Navy systems account for the majority of that systems acquisition cost, even when economies of scale and automated manufacturing practices are taken into account. Radar and EW systems place unprecedented requirements on power supply stability, noise, and reliability. Consequently, a considerable amount of space in the T/R module is occupied by capacitors that are integral to the power conversion units. This contributes greatly to the size and weight of the T/R module. A significant fraction of the T/R module footprint is dedicated to dozens (perhaps scores) of capacitors. Furthermore, even with pick and place (robotic) manufacturing, power conversion components account for considerable cost in assembly, stocking, and handling. Finally, the space occupied by so many capacitors restricts future modification to the T/R module design. That is, precious circuit board space could be better used for future design upgrades that enhance performance. Consequently, reducing the capacitor count and/or footprint by developing higher energy density capacitors has multiple benefits for future T/R module based systems. This topic therefore serves to reduce life-cycle cost by directly reducing the cost of acquisition - both initial acquisition cost and the cost of future spares. Acquisition cost is reduced by reduction in parts count and the cost of assembly, specifically by reducing the number of capacitors needed in the power conversion circuitry. Capacitors are fundamental electrical components found in virtually every electronic device. The commercial capacitor industry is well established and produces a wide range of standardized as well as specialized parts. Research in the field is typically driven by the commercial market. Military applications benefit from consumer market growth and the demands of new commercial applications. However, capacitor usage in military systems, vast though it may be, is still a minority market, insufficient to drive research trends. For example, recent trends in energy storage and electric motor control for hybrid vehicles and public transit have stimulated research in super capacitors. However, super capacitors are generally intended to augment battery storage systems and have unacceptably high internal impedance, low intrinsic voltage rating, and suffer accelerated degradation as temperature increases. Other applications drive capacitor technology towards smaller scales for integration at the microcircuit level. The research that has been devoted to conventional capacitor development has typically concentrated on new and, yet, unproven materials. In order to enable future compact, affordable, and higher-performance T/R modules, the Navy seeks to develop advanced, high-density capacitor technology for power conversion circuits. The desired technology would achieve at least a two-times increase in energy storage density without compromising performance parameters such as internal impedance, voltage rating, leakage current, temperature stability and, above all, reliability. In addition, when manufactured in quantity, the per-unit cost must have a viable path to a pricing point comparable to existing capacitors of similar ratings and application. For example, a capacitor technology with twice the energy storage, such that the number of capacitors per T/R module could be approximately halved, yet costing only 20% more, would be a desirable solution. In addition, the proposed technology cannot contain inordinately toxic or hazardous material, as end-of-life disposal of military equipment presents a real and tangible cost. The technology desired is essentially an improved conventional capacitor suitable for application in switched-mode power converters (DC-DC or AC-DC) with output voltages in the range of 5 to 150 Volts DC and switching frequencies in the tens to hundreds of kilohertz regime. 

PHASE I: The company will define and develop a concept for high-density capacitors meeting the technical objectives and consistent with the application stated in the topic description. The company will demonstrate the feasibility of their concept in meeting Navy needs and will establish that their concept can be feasibly and affordably produced. Feasibility will be established by some combination of initial (and perhaps scaled) prototype testing, analysis or modeling. Affordability will be established by analysis of the proposed materials and processes and by comparison to existing and established capacitor technologies. The Phase I Option, if awarded, will include the initial design specifications and capabilities description to build a prototype in Phase II. 

PHASE II: Based on the Phase I results and the Phase II Statement of Work (SOW), the company will produce and deliver prototype high-density capacitors for evaluation. The prototype capacitors will be evaluated to determine their capability in meeting Navy requirements of energy storage density, voltage rating, leakage current, internal impedance, temperature stability, reliability and other parameters that define their suitability in the intended application. Evaluation will primarily be accomplished by electrical testing of multiple prototype capacitors (at least ten samples in each voltage and capacitance rating) accompanied by appropriate data analysis and modeling. A subset of prototype capacitors will be demonstrated in a representative DC-DC and/or AC-DC switching-mode power converter to prove suitability for the intended application. Testing, evaluation, and demonstration are the responsibility of the company and should therefore be included in the Phase II proposal. Affordability will be addressed by refining the affordability analysis performed in Phase I to reflect the knowledge gained in Phase II execution. The affordability analysis will propose best-practice manufacturing methods to prepare the capacitor technology for Phase III transition. The company will prepare a Phase III development plan to transition the technology for Navy and potential commercial use. 

PHASE III: The company will be expected to support the Navy in transitioning the technology to Navy use. The company will further refine high-density capacitors according to the Phase III development plan for evaluation to determine its effectiveness and reliability in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify initial production components for Navy use. The final product will be produced by the company (or under license) and transitioned to the Government either through its prime contractors or directly to the Government in the course of technology upgrades for use in Navy systems such as SPY-6, SEWIP Block 3, and the future EASR and AMDR-X radars. Private Sector Commercial Potential: Capacitors are one of the most common parts found in consumer, industrial, and military electronics. Any advances made in this area will undoubtedly find other applications. This is a basic need. 


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KEYWORDS: Power Conversion Circuits; High-Density Capacitor; Super Capacitor; Energy Storage; Power Converter; Transmit And Receive Module 

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