EEE Department, Imperial College

1
EEE Department, Imperial College

• Imperial College leading Technological Institute
  in UK
• Of 5 Groups in EEE Department, 3 participate in
  ORESTEIA
• Circuits Systems
• Optical Semiconductor Devices
• Control Power

2
Circuits and Systems Group

• Analog Integrated Circuit Design
• Ultra-low power (subthreshold CMOS processing)
• Integrated RF techniques for wireless
• Digital VLSI
• Reconfigurable computing
• Hardware/software co-design
• Thin film processing
• fully-integrated flat panel display drivers

3
Optical and Semiconductor Devices Group

• microsystems technology
• integrated optics
• semiconductor devices
• micro-fabrication techniques

4
Control and Power Group

• The Group brings combines expertise in
• the analysis, modelling and control of large,
  multivariable non-linear systems and
• the technology and policy issues of electrical
  energy delivery.
• Group comprises
• 3 Professors
• 7 Academic Staff
• 16 Ph.D. students
• 8 Research associates

5
Artefact Interconnections

• BlueTooth 2.4GHz
• 100m (up to 1000m), 1 Mb/s,
• 100mW average in 1s sniff mode
• Unlicensed Band 315/413 MHz
• AM
• 100m, typ. 4kHz bandwidth
• 8 mW TX, 1.5mW RX
• FM
• 250m, 9.6kHz bandwidth
• 24mW TX, 25mW RX
• Low Power BlueTooth
• 10m range, 500 MHz carrier, low bit rate
• Possible to achieve 1mW
• Ultra-low Power Wireless Link
• Could we achieve operation at 0.1 mW or less ?

implanted
wearable
mobile
fixed
fixed server
6
Ultra-Low Power Wireless Link

• Consider specifications for low-power link, e.g
  433MHz carrier, 20 kb/s data rate, simple FSK
  modulation scheme, allows us to derive the
  following graph

NF of 20dB allows us to transmit 100m (10-20m
indoors) with just -12.5dBm of power, i.e. less
than 0.06mW!
Transmit Power versus Receiver Noise Figure
7
Circuit Implementation of Micropower Functionality

• If artefacts (level 1 and 2) are to be
  self-powered, ultra-low power consumption is
  necessary. This implies
• low voltage, low current operation
• intelligent power saving operation
• low-power wireless link to higher level artefacts
• Submicron CMOS is the most appropriate process
  technology to meet these goals.

8
Sub-threshold CMOS
One billionth the Power !
9
An Example Micropower Cochlea Implant

• Complete electronics for first fully implantable
  artificial cochlea
• System-on-chip designed and developed at Imperial
  College
• Mixed-signal solution analog processing with
  digital control

Cochlea
Ultra-low power audio processor section
Processor, battery and microphone package
5 mm
Inserted here
Low power digital control and wireless telemetry
section
3 mm
10
Micropower GenerationEnergy sources and
conversion mechanisms
Energy source
Conversion to electricity
Kinetic
e.g. body movement
Magnetic (induction) Piezoelectric Electrostatic
Thermal
e.g. DT between body and surroundings
Thermoelectric (TC) Thermo-electro-mech
Electro- magnetic
Low freq (lt MHz) RF (MHz to GHz) Optical
(IR/visible)
Induction loop Antenna Photodetector
Ultrasonic
Piezoelectric
11
Micropower GenerationElectrostatic Generator

• Resonant devices have scaling problem
• Pout ? Mw3z2 ? low-frequency devices with
  small displacement are inadequate
• IC Approach Non-linear devices can do better,
  e.g.
• Parametric Oscillating Generator

12
Micropower GenerationMajor Issues

• Any small (lt 1 cm3) kinetic generator is likely
  to be limited to mW average power levels

? low duty-cycle operation only

• Much higher power levels possible if we can
  include infrastructure for (wireless)

power delivery

• Trade-off between power budgets for
  communications and feature extraction in

type 12 artefacts needs careful consideration
Power budget
comms
Incr. Feature extraction
13
Micropower GenerationCircuit Design Issues

• Very efficient switch-mode power processing will
  be necessary to recover maximum energy from
  generator. Issues are quite different from
  standard power supplies because of high voltage
  and extremely low current.
• Optimisation of generator and circuit with
  constrains such as breakdown voltage
• Modeling of dynamics of electro-mechanical system
  so that interaction of mechanical design and
  power processing circuit can be assessed.
• Control and synchronisation of power generator