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Multiferroic Materials for RF Applications

Description:

OBJECTIVE: Demonstrate RF/microwave devices, components, and circuits based on multiferroic composite structures. Design discrete devices for radio and radar with a new tunability feature that adds to the performance over conventional RF/microwave components by leveraging the voltage-tunable frequency response of multiferroics. Demonstrate voltage tunable devices with performance equal to or better than state-of-the-art circuits. DESCRIPTION: Multiferroic composites demonstrate a unique ability to control their ferromagnetic resonance (FMR) by applying an electric field that causes a shift in their FMR frequency. Multiferroic materials consist of strain-coupled ferromagnetic and ferroelectric phases resulting in a magneto-electric coupling between the two materials. This magneto-electric coupling mechanism has an electrostatically-controllable magnetization, a feature that can enable an entirely new family of RF components and circuits where frequency and bandwidth are electrically tunable. RF/microwave multiferroic components such as tunable filters, duplexers, isolators, antennas and phase shifters are just a few examples of drop-in replacements, although entirely new devices, components and architectures are conceivable. Tunability is a feature added to the normal performance of an RF component. Multiferroic components with voltage tunability should perform at least as well as its non-multiferroic counterpart. In this way, tunability becomes a feature added to the RF/microwave designer"s toolbox. Frequency agile devices have been fabricated from many combinations of electrostrictive and magnetostrictive materials. However these devices have tended to be bulky, slow, consume excess energy, and perform within a narrow band of frequencies. For instance, BST-based tunable filters operating in the wireless 1.6-2.0GHz band have published results of 10dB return loss and 4dB insertion loss with a 25% tuning range using a rather large 0-200VDC tuning voltage. X-band (8-10GHz) BST tunable filters have demonstrated 15dB return loss, 8dB insertion loss, and a 23% tuning range using 0-90VDC. By comparison, commercially-available, off-the-shelf filters offer better than 3dB insertion loss and 20dB return loss. Multiferroic device performance must exceed current commercial capabilities to economically viable while providing new capabilities for more demanding Defense applications which may have to deal with countermeasures. Multiferroic solutions having a highly-tunable ferromagnetic resonance frequency should offer>70dB dynamic range in addition to meeting commercial component performance. Multiferroic phase shifters could conceivably have -180 to +180 degrees of phase shift tunable from 900 MHz to 6 GHz with an instantaneous bandwidth of 20 MHz. The availability of such components would dramatically transform the approach towards designing military RF/microwave radios and radars while also advancing the competitiveness of the U.S. electronics industry. Highly innovative and creative approaches, concepts and solutions based on multiferroic composites and their unique features are especially sought. It is highly desirable to develop manufacturing processes that enable commercial adoption of multiferroic devices by commercial vendors. A commercialization plan including adoption by RF/microwave component suppliers is encouraged. Recent advancements in the fabrication of high-quality ferrimagnetic-ferroelectric stacks have made this the time to commercialize multiferroic RF components. PHASE I: Demonstrate a proof-of-concept multiferroic-based voltage tunable device used as the basis of a building block for a radio or radar. The device should be optimized for realistic radio or radar applications (voltage tuning range, frequency tuning range, power handling, quality factor, temperature coefficient, etc.) and should provide maximum tunability in the military frequency band assignments of the communications or radar spectrum. In addition to achieving conventional state-of-the-art performance, the design should provide for frequency tunability using a low-voltage (~12 volt) DC power supply. The physical design and fabrication shall be based on multiferroic composites with accompanying modeling and analysis to design physical layout and prediction of the high-frequency performance. PHASE I deliverables will also include development of an initial concept design and RF models of the key aspects of the device. Elements of the multiferroic design may be bread-boarded and measured as validation of detailed analysis of the predicted RF performance. The project plan should define and develop key technological milestones such as performance modeling and simulation of the device. PHASE II: Fabricate and demonstrate an operating prototype of a multiferroics-based building block used in a radio or radar architecture. For example, the building block may be a tunable filter for a radio, a phase shifter for a radar set, or a similar 50 ohm component. It should build on the device developed in PHASE I, or use as its foundation the materials processing developed in PHASE I. A detailed plan of action to design, fabricate and assemble all the necessary RF components should be provided and followed by testing and characterization of the RF building block. The results of the testing should be used to update the multiferroic design, modeling and simulation tools. The RF performance parameters to be expected from multiferroic materials should be established through experiments performed on the prototype. Circuits of interest include, but are not limited to phase shifters (-180 to +180 degrees, tunable in the band 900 MHz to 6 GHz) and filters with high Dynamic Range and broad tunability (>70 dB dynamic range, 50% of center frequency). Broad band piezoelectric amplifiers (Reference 14) with composite microstructures (reference 15) with efficiency of greater than 60%; and compact B-field antennas are also components of interest for this topic. For devices utilizing the tunable response of multiferroics for other proposed devices/circuits (i.e.: broad band amplifiers and compact antennas) comparable quantitative metrics must be stated. At the conclusion of PHASE II effort, the building block prototype should be at a Technology Readiness Level 5 (TRL-5) or above. PHASE III: Millitary applications of this technology include radios and radar systems. Voltage tunable inductors allow design of frequency agile circuits while maintaining constant impedance. Specific radar applications include ground penetrating applications and low frequency arrays for airborne use. The technology represents radical innovation for the wireless communication industry as well as radar systems. The U.S. commercial electronics community could benefit from a multiferroics fabrication process that is robust enough to be adopted for manufacturing. This would ultimately lead to monolithic integration of multiferroic materials with conventional silicon semiconductor processes. The multiferroic devices, components, circuits, and architectures proposed should have a development path leading to commercial adoption by mainstream RF component suppliers such as Mini- Circuits, Digi-Key, Newark, and similar established distributors. Such a development path would clearly show that multiferroics technology is ready for commercial electronics use.
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