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All-Dielectric MMW Systems

K. Brakora, A. Buerkle, and K. Sarabandi

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Fig. 1.  A uniform slab of a subwavelength periodic structure constructed from Al2O3� and produced using ceramic stereolithography.  The structure has an effective refractive index of 1.8 when the periodicity is less than 1/5th the free-space wavelength.

This study is motivated by the need for low-cost, high-performance, compact, integrated, and reliable MMW systems for variety of military and scientific applications such as multifunctional passive front-ends for radar and communication, beam-formers, high-power radars, high data-rate MMW local area networks, and low noise figure antennas and filters.

The proposed research applies developments in Ceramic Stereolithography (CSL) to fabricate very complicated MMW subsystems that include passive components such as waveguides, filters, resonators, power dividers, beam-formers, individual antennas, lens antennas, etc., monolithically without the need for components assembly. Designs will use sub-wavelength and bandgap periodic structures to construct complete operational MMW RF front-end subsystems. Electromagnetic functionality is achieved by proper distribution of extremely low-loss ceramic materials in 3D space. In addition to the ease of fabrication, the proposed all-ceramic design offers enhanced electromagnetic functionality in terms of component efficiency and power handling capabilities.

The objectives of this study are threefold. The first objective is to build a catalog of production-ready MMW components and subsystems, each scalable in frequency and tailored the constraints and tolerances of the fabrication process. The second objective is to optimize existing CSL technology to fabricate operational Ku-, V-, and W-band components and subsystems in a manor expandable to small-scale manufacturing. The third objective is to demonstrate the applicability of emerging micro-Ceramic Stereolithography (mCSL) technologies to W-, F-, and D-band components and subsystems with a capability of extending functionality into terahertz frequencies. Success in these objectives would result in easily transferable Ku-, V-, and W-band technologies that could be put into small-scale production in as little as two years and would pave the way for future commercialization of low-loss F- and D-band subsystems.

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Fig. 2.  The 30GHz monolithic Luneberg lens.  A Luneberg lens is a quasi-optical antenna whose index of refraction decreases radially outward from the center.  This first-of-its-kind device uses variable periodic structures to create the desired dielectric profile.  (Left) a picture of the monolithic Luneberg Lens, and (right) the measured radiation pattern of the Luneberg lens.

The proposed effort is an enabling technology. Low-loss and low-cost ceramic MMW subsystems have immediate application in automotive, nautical, and aerospace radar due the material’s natural resistance to corrosion and ability to tolerate extreme temperatures and pressures without significant degradation of performance. Owing to the fact that some ceramics, such as alumina and silica, are among the few materials which maintain nearly constant low-loss dielectric properties well into terahertz frequencies, future terahertz systems will rely upon advances in design and fabrication of ceramic systems.

Fig.3: Eight by eight array of dielectric resonator antennas at 20 GHz fabricated by CSL technology and its measured radiation pattern.
Fig.3: Eight by eight array of dielectric resonator antennas at 20 GHz fabricated by CSL technology and its measured radiation pattern.