Rao Tummala

Bio: Rao Tummala is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Interposer & Capacitor. The author has an hindex of 43, co-authored 623 publications receiving 11663 citations. Previous affiliations of Rao Tummala include Qualcomm & IBM.

Gigabit wireless: system-on-a-package technology

Abstract: The system-on-a-package (SOP) concept is considered as the solution of future communication modules, where more functionality, better performance, low cost, and more integrity is needed. We demonstrate how SOP technology can address the integration platform for future communication systems, especially gigabit wireless communications. After the introduction of the SOP concept, we introduce the critical design building blocks which are required in a viable SOP technology: integrated passives, embedded RF functions, including high-performance filters and baluns, and integrated antenna technologies. Second, we review how the three-dimensional deployment of core elements, such as baluns, lumped inductors, capacitors, and resistors, as well as IF or low-pass filters, enables RF-SOP module development. We demonstrate how advanced radio architectures, including direct conversion, antenna diversity, and collaborative signal processing, are enabled using the SOP technology format. Various ceramic and organic material based multilayer packaging technologies have been used for building such integrated modules as well as circuit blocks. The critical issues and challenges for developing advanced communication platforms using the SOP approach are discussed.

Moore's law meets its match (system-on-package)

Abstract: This paper describes the system-on-package (SOP) approach to miniaturization developed at the Microsystems Packaging Research Center at the Georgia Institute of Technology. Representing a radically different approach to systems, SOP combines IC with micrometer-scale thin film versions of discrete components, and it embeds everything in a new type of package so small that eventually handhelds will become anything from multi- to megafunction devices. It shrinks bulky circuit boards with their many components and makes them nearly disappear. Thus, SOP technology yields far more in system miniaturization than can be expected from Moore's law, which deals only with transistors in ICs

Polymer-ceramic nanocomposite capacitors for system-on-package (SOP) applications

Abstract: This work focuses on optimizing the dispersion of nanosized ceramic particles for achieving higher dielectric constant, thereby higher capacitance density in polymer/ceramic nanocomposites. It has been observed that high solids loading leads to entrapment of porosity in the microstructure which lowers the effective dielectric constant of the films. The amount of solvent in the suspension and the speed at which spin coating was performed were found to impact the dielectric constant of high filler content nanocomposites. The interplay between the rheological properties of the suspension and processing parameters such as solvent content and coating speeds and its impact on the dielectric properties of the film are discussed. Porosity of thin film composites was measured for the first time to study the impact of these processing parameters. Powders of different particle sizes were mixed to obtain bimodal particle size distribution in order to increase the packing density of the composite. Packing density was improved by modifying the dispersion methodology. A nanocomposite with dielectric constant as high as 135 was obtained for the first time in the low-cost printed wiring board compatible epoxy system. A capacitance densities of /spl sim/35 nF/cm/sup 2/ on a nominal 3.5 micrometer films was achieved on PWB substrates with high yield. The manufacturability of these formulated nanocomposites and their applications as decoupling capacitors have been tested using a large area (300 mm /spl times/ 300 mm) system-on-package (SOP) chip-to-chip communication test vehicle.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Microfibre–nanowire hybrid structure for energy scavenging

Abstract: Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

Self-powered nanowire devices.

Abstract: The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.