This Small Business Technology Transfer (STTR) Phase I project aims to develop novel technology for Vacuum Electron Devices (VED) such as Traveling Wave Tubes (TWT) for the next generation high spectral efficiency, high data rate civilian and military communication systems. VED amplifier performance be greatly improved by employing frequency selective interaction structures (IS) with high gain in the operating band and negligible spurious output in the neighboring bands for achieving high spectral efficiency. This project aims to develop a novel TWT with a metamaterial (MTM) IS. MTMs can be engineered to simultaneously have large negative values of permittivity (å) and permeability (ì) which cause left handed propagation of electromagnetic waves with high coupling to the electron beam. Also, such structures allow co-propagation of an electron beam in the medium of the IS, permitting the choice of a spatially distributed high current electron beam to achieve higher gain and output power. As a result of the proposed research an MTM IS for a 10 GHz TWT will be designed, tested and characterized. A proof-of-concept TWT design will be developed which will have potential to advance the state-of-the-art in high data rate communication systems.
The broader impact/commercial potential of this project includes advances in novel designs of passive components such as waveguides, filters, duplexers, power combiners and channel drop filters. Advances in the performance of these components are crucial to advancing system-level performance of the next generation communication systems. The design methodology developed under this work will also be applicable to other microwave and terahertz sources such as VED based gyrotrons and semiconductor based Terahertz sources such as Quantum Cascade Lasers (QCL) by using an MTM structure to improve confinement of desired modes and filtering the unwanted modes. Also, further development of MTMs will create new technology for the manipulation and transportation of light which is the basic building block for optical computing. The development of the concept of using MTMs for solving problems in both active and passive microwave and terahertz devices will contribute to the understanding of the basic physics of MTMs and advance the field of microwave engineering.
Under this Phase I STTR grant we presented a novel design for a component of a high power amplifier system called a Traveling Wave Tube (TWT) which is used in terrestrial wireless and satellite communication systems. We improved the performance of the TWT by incorporating a Metamaterial (MTM) structure to suppress spurious noise and improve signal purity. MTMs are periodic arrangement of metallic or dielectric elements that have very unique frequency discrimination properties. In addition they can also act as artificial media with unique electrical properties that are not found in common materials. These properties can be harnessed for suppressing noise emanating from TWT amplifiers and allow more efficient use of the electromagnetic spectrum for communication. During the course of this Phase I work we designed, built and measured the parameters of such a MTM structure for use in a TWT. We found very good agreement between our theoretical design and experimental results. We also developed the design of a 70-80 GHz TWT for use in high-speed wireless communication radio systems. A major part of this work was done in collaboration with Tufts University where graduate students worked on this research project. This provided a good opportunity for students to gain experience in working with colleagues in industry and participate in product development based on cutting-edge research.
