19 research outputs found
Performance analysis of pre-equalized multilevel partial response schemes
In order to achieve high speed on electrical interconnects, channel attenuation at high frequencies must be dealt with by proper transceiver design. In this paper we investigate finite-complexity MMSE pre-equalization under an average transmit power constraint, to compensate for channel distortion in the case of both full-response and precoded partial response signaling with L-PAM mapping, and consider the resulting error performance for symbol-by-symbol detection and sequence detection. For a representative electrical interconnect, we point out that the constellation size (2-PAM or 4-PAM), the type of signaling (full response or partial response), the detection method (symbol-by-symbol detection or sequence detection) and the number of pre-equalizer taps should be carefully selected in order to achieve satisfactory error performance at high data rates. For several scenarios, precoded duobinary 4-PAM is found to yield the best error performance for given average transmit power
Fast-OFDM transmission with duobinary 3-PSK modulation
This paper investigates duobinary signals and their applications in non-orthogonal multi-carrier systems to enhance spectral efficiency. In duobinary transmission schemes, the signal spectrum is reshaped by introducing controlled correlation, which can be eliminated at the duobinary decoder. For the first time, we propose the idea of combining duobinary transmission technique and the fast orthogonal frequency division multiplexing (Fast-OFDM) system with three subcarriers, with experimental results presented. The proposed system is capable of achieving three times the data rate of single-carrier ASK scheme with the same bandwidth. Results show that bit error rate (BER) performance of the proposed duobinary-based Fast-OFDM system is slightly worse than the ASK system. In addition, we also tested various 3-PSK constellation patterns designed for the duobinary signal to achieve performance improvement
Building up low-complexity spectrally-efficient Terabit superchannels by receiver-side duobinary shaping
Recently, an increasing interest has been put on spectrally-efficient multi-carrier superchannels for beyond 100G. Apart from orthogonal frequency-division multiplexing (OFDM) and Nyquist wavelength-division multiplexing (WDM), another low-complexity WDM approach based on transmitter-side pre-filtering and receiver-side duobinary shaping is proposed to build up multi-carrier superchannels. This approach is referred to as receiver-side duobinary-shaped WDM (RS-DBS-WDM). Generation and transmission of a 1.232-Tbit/s 11-carrier superchannel is experimentally demonstrated. The superchannel signal can be well fit inside the passband of multiple 300-GHz reconfigurable optical add and drop multiplexers (ROADMs). In the superchannel scenario, the proposed RS-DBS-WDM is qualitatively compared with OFDM and Nyquist-WDM in terms of implementation complexity. In sum, the proposed RS-DBS-WDM approach features high transceiver analog-bandwidth efficiency, high spectral-efficiency, the absence of specific spectral manipulation, compatibility with conventional WDM technologies and coherent detection algorithms, and comparable implementation penalty
Available Techniques for Magnetic Hard Disk Drive Read Channel Equalization
This paper presents an extensive, non-exhaustive, study of available hard disk drive read channel equalization techniques used in the storage and readback of magnetically stored information. The physical elements and basic principles of the storage processes are introduced together with the basic theoretical definitions and models. Both read and write processes in magnetic storage are explained along with the definition of simple key concepts such as user bit density, intersymbol interference, linear and areal density, read head pulse response models, and coding algorithm
Investigation into PRS-precoded, constant-envelope, continuous-phase digital modulation schemes
Bibliography: leaves 78-79.Partial response signaling ( PRS) has been used successfully to improve the spectral properties of Pulse Amplitude Modulated (PAM) digital transmission systems. This thesis investigation studied the effect of PRS on frequency- and phase-modulated carrier systems, in particular on their spectral performance and their maintenance of constant envelope
An investigation into a DSP implementation of partial response signaling for 4800 bits per second full-duplex data communications over M.1020 telephone lines
Includes bibliographical references.This thesis investigates high-speed digital transmission over a conditioned, voice-grade telephone circuit (M.1020), using a technique known as partial response signaling, or PRS. In particular, the case where 4800 bps, full-duplex transmission is required in a CCI'PT V. 22 type format is investigated. The main v.22 criterion to be adhered to, is that frequency-division multiplexing (FDM) is to be used as the means of separating thetransmit and receive channels. The carrier frequencies should be 1200 Hz and 2400 Hz respectively. The investigation concerns the modulation and demodulation sections only
Design of adaptive analog filters for magnetic front-end read channels
Esta tese estuda o projecto e o comportamento de filtros em tempo contÃnuo 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 nÃvel mundial com o objectivo de se investigarem novas técnicas
de realização de filtros em circuito integrado monolÃtico, especialmente em tecnologia
CMOS (Complementary Metal Oxide Semiconductor). Apresenta-se um estudo comparativo
a diversos nÃveis hierárquicos do projecto, que conduziu à realização e caracterização
de soluções com as caracterÃsticas desejadas.
Num primeiro nÃvel, 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 à s aproximações na conformidade aos princÃpios
fÃsicos dos dispositivos caracterizados.
O trabalho principal da tese é focado nos nÃveis hierárquicos da arquitectura do
canal de leitura e da realização em circuito integrado do seu bloco principal – o bloco de
filtragem. Ao nÃvel 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 desÃgnio 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
contÃnuo.
Ao nÃvel 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 nÃvel hierárquico mais baixo,
dois subnÃveis 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 contÃnuo.
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 contÃnuo 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 transÃstores 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 passÃvel
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 incluÃdo num circuito integrado (Jaguar) de
controlo de posicionamento da cabeça de leitura realizado para a empresa ATMEL em
Colorado Springs, e incluÃdo num produto comercial em parceria com uma empresa escocesa
utilizado em discos rÃgidos amovÃveis.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