scispace - formally typeset
Search or ask a question
Author

Rao Tummala

Other affiliations: Qualcomm, IBM, AVX Corporation  ...read more
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.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, low-loss small microvias in build-up layers for the next-generation high-density high-performance fifth-generation (5G) millimeter-wave (mm-wave) antenna-integrated packages are presented.
Abstract: This article presents, for the first time, low-loss small microvias in build-up layers for the next-generation high-density high-performance fifth-generation (5G) millimeter-wave (mm-wave) antenna-integrated packages. As the operating frequency increases, the signal losses in antenna packages become more critical and need to be mitigated to obtain desired performance in beamforming and massive multi-input multi-output. As electrical wavelengths in mm-wave spectra are short, the signal losses caused by microvias dominate the loss budget. To minimize the signal losses and identify the required microvia diameter in build-up layers, this article first focuses on the modeling of small microvias for impedance matching. Based on the models and simulated characteristic impedance, test vehicles with daisy chains are fabricated in build-up layers on a core package substrate. Ultraviolet (UV) laser is utilized to drill microvias, and targeted microvia diameters are obtained through a semiadditive patterning process. High-frequency measurements are also performed to correlate with the models and simulated results in the 28-GHz band. The characterization results exhibit good model-to-hardware correlation and indicate that small microvias (20 $\mu \text{m}$ ) provide impedance closer to $50~\Omega $ compared with the larger microvias. This matched microvia impedance lowers reflection and insertion loss, resulting in a 10% reduction in the signal losses caused by microvias in the 5G New-Radio n257 band around 28 GHz.

13 citations

Proceedings ArticleDOI
10 Dec 2003
TL;DR: In this article, the design of a wafer level package on board for 5GHz data transmission has been discussed based on the 2005 node of the International Technology Roadmap on Semiconductors (ITRS).
Abstract: This paper discusses the design of a wafer level package on board for 5GHz data transmission. The design is based on the 2005 node of the International Technology Roadmap on Semiconductors (ITRS) that predicts a clock frequency of 5GHz, power of 170W and an operating voltage of 0.9V for high-end microprocessors. The goal of this paper is to demonstrate the ability to support global interconnections on the board at a speed comparable to the clock frequency and supply adequate power to the chip. This requires careful design of the topology of the interconnections, control of the eddy current losses in Silicon, control of the conductor and dielectric losses in the board and design of the transition between the chip and the board. The electrical design process is discussed in detail using a test vehicle, in this paper. The test vehicle consists of Co-planar waveguide (CPW) lines on high resistivity Silicon Substrate connected to CPW lines on low k, low loss board. The transition between the chip and board is completed through solder bumps with 50 /spl mu/m diameter and 100 /spl mu/m pitch. Both the Silicon and Board transmission lines have been characterized using TDR measurements. In addition, the inductance of the solder bumps have been extracted. Using synthesized models extracted from measurements, the eye diagrams for 5GHz data transmission has been simulated to show the importance of losses for 1mm long Silicon lines connected to 5cm long board lines through low inductance solder bumps. In addition, the effect of underfill and curing on signal propagation have been quantified.

13 citations

Journal ArticleDOI
Rao Tummala1
TL;DR: In this paper, the development of lowexpansion and low-temperature solder glass composites by the formation of Perovskite lead titanate was studied by the use of differential thermal analysis and thermal expansion measurements techniques.
Abstract: The development of low-expansion and low-temperature solder glass composites by the formation of Perovskite lead titanate was studied by the use of differential thermal analysis and thermal expansion measurements techniques. The thermal expansion coefficients of these composites containing Perovskite lead titanate of highly negative thermal expansion coefficient are predictable, at least in simple systems, by the existing theories of thermoelasticity.

13 citations

Patent
08 May 2006
TL;DR: In this paper, the authors have discussed composite RF devices having low temperature coefficient of permittivity (TCP) and methods for fabricating same, including thin and thick film capacitors and antennas, which may be formed on or within an organic layer, silicon material, ceramic material, or ceramic composite material or insulating material.
Abstract: Disclosed are composite RF devices having low temperature coefficient of permittivity (TCP) and methods for fabricating same. The RF devices comprise first and second conductive electrodes with a composite dielectric material disposed there between that comprises a polymer material having positive or negative TCP and one or more ceramic filler materials having corresponding negative or positive temperature coefficients of permittivity. The composite dielectric material may also comprise a blend of positive and negative TCP ceramic filler materials. The composite dielectric material may also have a bimodal distribution of positive and negative TCP filler materials to vary the packing density of the dielectric material. Various devices may be fabricated including thin and thick film capacitors and antennas, which may be formed on or within an organic layer, silicon material, ceramic material, ceramic composite material or insulating material.

13 citations

Journal ArticleDOI
TL;DR: In this paper, a low-loss substrate-integrated waveguides (SIWs) in fused silica and borosilicate glass and a comparison of their performance with various organic-based lowloss substrates for millimeter-wave applications are presented.
Abstract: This letter, for the first time, presents low-loss substrate-integrated waveguides (SIWs) in fused silica and borosilicate glass and a comparison of their performance with various organic-based low-loss substrates for millimeter-wave applications. Utilizing ring resonators designed for frequencies in the 5G New Radio (NR) n257 band (26.5–29.5 GHz), this letter begins with the determination of the dielectric constant of fused silica to model SIWs. This letter also introduces the designs of SIWs that are fed by conductor-backed coplanar waveguides and discusses the fabrication and measurement results with deembedding analysis. In addition to the excellent correlation between simulations and measurements, the characterization results show more than $2\times $ reduction in the insertion loss compared to those of low-loss organic-based SIWs at the 28-GHz frequency band.

13 citations


Cited by
More filters
Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
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 …

33,785 citations

Journal ArticleDOI
TL;DR: Shape-memory polymers as discussed by the authors are an emerging class of active polymers that can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus.

1,575 citations

Journal ArticleDOI
14 Feb 2008-Nature
TL;DR: This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics and presents a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres.
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.

1,473 citations

Journal ArticleDOI
TL;DR: This work demonstrates the vertical and lateral integration of ZnO nanowires into arrays that are capable of producing sufficient power to operate real devices and uses the vertically integrated nanogenerator to power a nanowire pH sensor and a Nanowire UV sensor, thus demonstrating a self-powered system composed entirely of nanowiring.
Abstract: The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.

1,465 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the important role and challenges of high-k polymer-matrix composites (PMC) in new technologies and discuss potential applications of highk PMC.

1,412 citations