Selected Research Topics

1
Selected Research Topics

• VSEM Virtual Scanning Electron Microscope
• Optwire Free-Space Cellular Optical LAN
• Oakleaf CMOS Optical Transmitter Driver
• High Linearity Mixers for RF Optical
  Communications
• RENIAC Reconfigurable Novel Integrated Analogue
  Computing Cell

2
Virtual SEM

• VSEM - Virtual Scanning Electron Microscope
• Software teaching and training package
• High-performance SEM simulator
• Computer-based encyclopaedia of SEM science
  operating procedures
• Computer-Based Learning (CBL) module to
  teach/assess users
• Founded on mainstream Internet technologies
• Easily distributable
• Platform portable
• Simulator coded using Java.
• Digital filters applied in real-time to captured
  SEM images emulate SEM imaging capabilities
• Encyclopaedia uses Flash and XML
• Allows delivery of information via web
• Demonstrator has shown proof-of-concept of
  simulator encyclopaedia

Screenshot from the VSEM simulator (above)
Screenshot from the VSEM encyclopaedia (below)
For further information about VSEM, e-mail Geoff
Martin at info_at_virtualsem.com Or look at the
VSEM website www.virtualsem.com.
3
Cellular Optical LAN Optwire

• Aims
• Demonstrating compact low cost optical
  transceivers for in-building free space data
  networks.

Receiverarray

• Receiver
• InGaAsP imaging system maps arrival angle at
  detector
• Allows uplink direction to be ascertained
• Segmentation reduces detector capacitance
• CMOS diversity receiver operates up to 1Gb/s

• Transmitter
• Multiple array of RCLED emitters
• Minimises power transmitted
• Allows efficient use of bandwidth
• Integrated 150 Mbit/s CMOS driver

Transmitterdriver
4
CMOS Optical Transmitter Driver

• Pre-distortion lineariser gives enhanced SNR
• CMOS integrated device
• Fabricated using AMS 0.35 mm CMOS technology
• IIP3 improved by 8.9 dB at centre frequency of
  700 MHz
• SFDR3 improvement of 3.6 dB/Hz2/3 at 40 MHz
  system bandwidth

5
Highly Linear CMOS Mixer for Optical and RF
Communication

• Non-linearity is a serious bottleneck in RF
  circuit design

• Mixer a critical component in Communications
  Systems
• Non-linearity potentially affects optical or RF
  network performance
• Mixer should reject harmonics and Intermodulation
  Distortion (IMD)

• Novel approach to linearisation of 2 GHz CMOS
  Gilbert mixer
• Based on Volterra Series Analysis
• Simulations indicate
• Gain 6dB, SNR 12dB
• IIP3 improvement 10dBmcf. standard Gilbert
  mixer
• Target technology UMC 0.18 RF/MM CMOS Process

6
Reconfigurable Novel Integrated Analogue
Computing Cell

• Objective
• Exploit recent developments in standard VLSI
  processes techniques, cheap programmable
  analogue computers can be conceived
• Overall Architecture
• Executes both Sequential Parallel programs
• Basic Blocks are
• Program Control Element (PCE)
• Data Control Element (DCE)
• Arithmetic Processing Unit (APE)
• Differential Processing Unit (DPE)
• Computing Architecture
• Solves mathematical problems by attacking it
  usinga swarm of small and inexpensive computing
  cells.
• Computes using physical analogues instead of
  mathematical algorithms