Ultra-high density recording technologies

The Engineering Research Center in Data Storage Systems at Carnegie Mellon University in cooperation with the National Storage Industry Consortium has selected goals of achieving 10 Gbit/sq in. recording density in magnetic and magneto-optic disk recording and 1 terabyte/cubic in. magnetic tape recording technologies. This talk describes the approaches being taken and the status of research leading to these goals

NSSDC Conference on Mass Storage Systems and Technologies for Space and Earth Science Applications, volume 1

Papers and viewgraphs from the conference are presented. This conference served as a broad forum for the discussion of a number of important issues in the field of mass storage systems. Topics include magnetic disk and tape technologies, optical disks and tape, software storage and file management systems, and experiences with the use of a large, distributed storage system. The technical presentations describe, among other things, integrated mass storage systems that are expected to be available commercially. Also included is a series of presentations from Federal Government organizations and research institutions covering their mass storage requirements for the 1990's

Silicon microstructures and microactuators for compact computer disk drives

Advances in VLSI and software technology have been the primary engines for the ongoing information revolution. But the steady stream of technical innovations in magnetic disk recording technology are also important factors contributing to the economic strengths of the computer and information industry. One important technology trend for the disk drive industry has been that of miniaturization. As this trend continues, future disk drives will have the same form factor as VLSIs, storing gigabytes of data. Silicon micromachining technology will play an important role in the fabrication of high-bandwidth servo-controlled microelectromechanical components for future super-compact disk drives. At UCLA and Caltech, for the past two years (1992-94) we have initiated a number of industry-supported joint research projects to develop microstructures and microactuators for future generation super compact magnetic recording rigid disk drives, including one to design and fabricate silicon read/write head microsuspensions with integrated electrical and mechanical interconnects, which target the next generation 30% form factor pico-sliders, and one for electromagnetic piggyback microactuators in super high-track-density applications, both of which utilize state-of-the-art silicon micromachining fabrication techniques

Silicon micromachined SCALED technology

Silicon micromachining technology will play an important role in the fabrication of high-bandwidth servo controlled microelectromechanical (mechatronic) components for super-compact disk drives. At the University of California, Los Angeles, and the California Institute of Technology, for the last three years, we have initiated a number of industry-supported joint research projects to develop the necessary technology building blocks for an integrated drive design of the future. These efforts include a silicon read/write head microgimbal with integrated electrical and mechanical interconnects, which targets the next-generation 30% form factor pico-sliders, and an electromagnetic piggyback microactuator in super-high-track-density applications, both of which utilize state-of-the-art silicon micromachining fabrication techniques

Optical disks become erasable

The topics covered include the following: optical recording; how does it work?; why all the fuss?; state of the industry; sample applications; and future directions

Design of adaptive analog filters for magnetic front-end read channels

Esta tese estuda o projecto e o comportamento de filtros em tempo contínuo de muito-alta-frequência. A motivação deste trabalho foi a investigação de soluções de filtragem para canais de leitura em sistemas de gravação e reprodução de dados em suporte magnético, com custos e consumo (tamanho total inferior a 1 mm2 e consumo inferior a 1mW/polo), inferiores aos circuitos existentes. Nesse sentido, tal como foi feito neste trabalho, o rápido desenvolvimento das tecnologias de microelectrónica suscitou esforços muito significativos a nível mundial com o objectivo de se investigarem novas técnicas de realização de filtros em circuito integrado monolítico, especialmente em tecnologia CMOS (Complementary Metal Oxide Semiconductor). Apresenta-se um estudo comparativo a diversos níveis hierárquicos do projecto, que conduziu à realização e caracterização de soluções com as características desejadas. Num primeiro nível, este estudo aborda a questão conceptual da gravação e transmissão de sinal bem como a escolha de bons modelos matemáticos para o tratamento da informação e a minimização de erro inerente às aproximações na conformidade aos princípios físicos dos dispositivos caracterizados. O trabalho principal da tese é focado nos níveis hierárquicos da arquitectura do canal de leitura e da realização em circuito integrado do seu bloco principal – o bloco de filtragem. Ao nível da arquitectura do canal de leitura, apresenta-se um estudo alargado sobre as metodologias existentes de adaptação de sinal e recuperação de dados em suporte magnético. Este desígnio aparece no âmbito da proposta de uma solução de baixo custo, baixo consumo, baixa tensão de alimentação e baixa complexidade, alicerçada em tecnologia digital CMOS, para a realização de um sistema DFE (Decision Feedback Equalization) com base na igualização de sinal utilizando filtros integrados analógicos em tempo contínuo. Ao nível do projecto de realização do bloco de filtragem e das técnicas de implementação de filtros e dos seus blocos constituintes em circuito integrado, concluiu-se que a técnica baseada em circuitos de transcondutância e condensadores, também conhecida como filtros gm-C (ou transcondutância-C), é a mais adequada para a realização de filtros adaptativos em muito-alta-frequência. Definiram-se neste nível hierárquico mais baixo, dois subníveis de aprofundamento do estudo no âmbito desta tese, nomeadamente: a pesquisa e análise de estruturas ideais no projecto de filtros recorrendo a representações no espaço de estados; e, o estudo de técnicas de realização em tecnologia digital CMOS de circuitos de transcondutância para a implementação de filtros integrados analógicos em tempo contínuo. Na sequência deste estudo, apresentam-se e comparam-se duas estruturas de filtros no espaço de estados, correspondentes a duas soluções alternativas para a realização de um igualador adaptativo realizado por um filtro contínuo passa-tudo de terceira ordem, para utilização num canal de leitura de dados em suporte magnético. Como parte constituinte destes filtros, apresenta-se uma técnica de realização de circuitos de transcondutância, e de realização de condensadores lineares usando matrizes de transístores MOSFET para processamento de sinal em muito-alta-frequência realizada em circuito integrado usando tecnologia digital CMOS submicrométrica. Apresentam-se métodos de adaptação automática capazes de compensar os erros face aos valores nominais dos componentes, devidos às tolerâncias inerentes ao processo de fabrico, para os quais apresentamos os resultados de simulação e de medição experimental obtidos. Na sequência deste estudo, resultou igualmente a apresentação de um circuito passível de constituir uma solução para o controlo de posicionamento da cabeça de leitura em sistemas de gravação/reprodução de dados em suporte magnético. O bloco proposto é um filtro adaptativo de primeira ordem, com base nos mesmos circuitos de transcondutância e técnicas de igualação propostos e utilizados na implementação do filtro adaptativo de igualação do canal de leitura. Este bloco de filtragem foi projectado e incluído num circuito integrado (Jaguar) de controlo de posicionamento da cabeça de leitura realizado para a empresa ATMEL em Colorado Springs, e incluído num produto comercial em parceria com uma empresa escocesa utilizado em discos rígidos amovíveis.This thesis studies the design and behavior of continuous-time very-high-frequency filters. The motivation of this work was the search for filtering solutions for the readchannel in recording and reproduction of data on magnetic media systems, with costs and consumption (total size less than 1 mm2 and consumption under 1mW/pole), lower than the available circuits. Accordingly, as was done in this work, the rapid development of microelectronics technology raised very significant efforts worldwide in order to investigate new techniques for implementing such filters in monolithic integrated circuit, especially in CMOS technology (Complementary Metal Oxide Semiconductor). We present a comparative study on different hierarchical levels of the project, which led to the realization and characterization of solutions with the desired characteristics. In the first level, this study addresses the conceptual question of recording and transmission of signal and the choice of good mathematical models for the processing of information and minimization of error inherent in the approaches and in accordance with the principles of the characterized physical devices. The main work of this thesis is focused on the hierarchical levels of the architecture of the read channel and the integrated circuit implementation of its main block - the filtering block. At the architecture level of the read channel this work presents a comprehensive study on existing methodologies of adaptation and signal recovery of data on magnetic media. This project appears in the sequence of the proposed solution for a lowcost, low consumption, low voltage, low complexity, using CMOS digital technology for the performance of a DFE (Decision Feedback Equalization) based on the equalization of the signal using integrated analog filters in continuous time. At the project level of implementation of the filtering block and techniques for implementing filters and its building components, it was concluded that the technique based on transconductance circuits and capacitors, also known as gm-C filters is the most appropriate for the implementation of very-high-frequency adaptive filters. We defined in this lower level, two sub-levels of depth study for this thesis, namely: research and analysis of optimal structures for the design of state-space filters, and the study of techniques for the design of transconductance cells in digital CMOS circuits for the implementation of continuous time integrated analog filters. Following this study, we present and compare two filtering structures operating in the space of states, corresponding to two alternatives for achieving a realization of an adaptive equalizer by the use of a continuous-time third order allpass filter, as part of a read-channel for magnetic media devices. As a constituent part of these filters, we present a technique for the realization of transconductance circuits and for the implementation of linear capacitors using arrays of MOSFET transistors for signal processing in very-high-frequency integrated circuits using sub-micrometric CMOS technology. We present methods capable of automatic adjustment and compensation for deviation errors in respect to the nominal values of the components inherent to the tolerances of the fabrication process, for which we present the simulation and experimental measurement results obtained. Also as a result of this study, is the presentation of a circuit that provides a solution for the control of the head positioning on recording/playback systems of data on magnetic media. The proposed block is an adaptive first-order filter, based on the same transconductance circuits and equalization techniques proposed and used in the implementation of the adaptive filter for the equalization of the read channel. This filter was designed and included in an integrated circuit (Jaguar) used to control the positioning of the read-head done for ATMEL company in Colorado Springs, and part of a commercial product used in removable hard drives fabricated in partnership with a Scottish company

INVESTIGATION INTO SUBMICRON TRACK POSITIONING AND FOLLOWING TECHNOLOGY FOR COMPUTER MAGNETIC DISKS

In the recent past some magnetic heads with submicron trackwidth have been developed in order to increase track density of computer magnetic disks, however a servo control system for a submicron trackwidth head has not been investigated. The main objectives of this work are to investigate and develop a new servo pattern recording model, a new position sensor, actuator, servo controller used for submicron track positioning and following on a computer hard disk with ultrahigh track density, to increase its capacity. In this position sensor study, new modes of reading and writing servo information for longitudinal and perpendicular magnetic recording have been developed. The read/write processes in the model have been studied including the recording trackwidth, the bit length, the length and shape of the transition, the relationship between the length of the MR head and the recording wavelength, and the SIN of readout. lt has also been investigated that the servo patterns are magnetized along the radial direction by a transverse writing head that is aligned at right angles with the normal data head and the servo signals are reproduced by a transverse MR head with its stripe and pole gap tangential to the circumferential direction. lt has been studied how the servo signal amplitude and linearity are affected by the length of the MR sensor and the distance between the shields of the head. Such things as the spacing and length of the servo-pattern elements have been optimised so as to achieve minimum jitter and maximum utilisation of the surface of the disk. The factors (i.e. the skew angle of the head) affecting the SIN of the position sensor have been analysed and demonstrated. As a further development, a buried servo method has been studied which uses a servo layer underneath the data layer, so that a continuous servo signal is obtained. A new piezo-electric bimorph actuator has been demonstrated. This can be used as a fine actuator in hard disk recording. The linearity and delay of its response are improved by designing a circuit and selecting a dimension of the bimorph element. A dual-stage actuator has been developed. A novel integrated fine actuator using a piezo-electric bimorph has also been designed. A new type of construction for a magnetic head and actuator has been studied. A servo controller for a dual-stage actuator has been developed. The wholly digital controller for positioning and following has been designed and its performances have been simulated by the MAL TAB computer program. A submicron servo track writer and a laser system measuring dynamic micro-movement of a magnetic head have been specially developed for this project. Finally, track positioning and following on 0.7 µm tracks with a 7% trackwidth rms runout has been demonstrated using the new servo method when the disk-was rotating at low speed. This is one of the best results in this field in the world