PicoRadio RF Transmitter

1
PicoRadio RF Transmitter Group Update

• Yuen Hui Chee
• Prof. Jan Rabaey
• University of California, Berkeley
• BWRC Winter Retreat
• 13 Jan 2005

2
PicoRadio RF Quartet

• Brian Otis
• Ultra-low power receiver architectures
• RF MEMS/CMOS co-design techniques

• Yuen-Hui Chee
• Ultra-low power transmitter architectures
• Antenna techniques

• Nathan Pletcher
• Reactive Radio architectures
• Low voltage RF design

• Simone Gambini
• Ultra-low power A/D converters

3
Wireless Sensor Networks (WSN) A New Radio
Environment

• Dense network of nodes over an area
• 100s to 1000s of nodes
• Distance between nodes 10m1
• Ad-hoc communication
• Multi-hops
• Peer to peer communications
• Low data throughput
• Small packet size
• Low data rate
• Bursty traffic

1 IEEE 802.15.4-2003 std
4
Challenges
System Integration
1S. Roundy, Energy Scavenging for Wireless Sensor
Networks, Kluwer Academic Publishers,
2003 2Chipcon datasheets
5
Current-State-of-the-Art Transmitter
MICROS1 Transmitter

• Issues
• Circuit power gtgt Radiated power
• High overhead
• Power hungry frequency synthesizer
• Inefficient power amplification

Traditional transmitter architecture NOT suitable
for PicoRadio because it has excessive energy
overhead.
1P. Choi et. al, ISSCC 2003
6
Direct Modulation Transmitter

• Direct Modulation
• Eliminates I/Q channels ? less overhead power
• No power hungry mixers
• RF MEMS based oscillator
• Provides a low power frequency reference
• Fast startup time
• Simple modulation schemes
• On-off keying

Lean transmitter is suitable for low power, low
data rate applications
7
Sub-100?W Ultra-Low Power Oscillator

• Ultra-Low Power 1.9GHz FBAR Oscillator
• Consumes a minimal power of 89?W
• Low Power Design Techniques
• Use high Q FBAR resonator
• Sub-threshold operation
• Low supply voltage
• Complementary devices to share bias current
• Good phase noise performance
• 120dBc/Hz at 100kHz offset

FBAR
CMOS
8
Transmitter Implementation
Transmitter Performance Summary
More details (including Rx) will be presented in
ISSCC 2005
9
Perspective
Radiated Power
1W
Radiated Power gtgt Circuit Power Wireless LAN,
Cellular High Complexity Transmitter PA Efficiency
100mW
10mW
1mW
100uW
Data Rate / Spectral Efficiency
Design Principles of Low Power Energy Efficient
Transmitter Simplicity and Co-design
10
Whats Next Towards sub-100µW Transceiver
Active Antenna Transmitter
ST 0.13?m CMOS
11
Whats Next Towards sub-100µW Transceiver
Ultra-low power digital controlled oscillator
(DCO)

• Nominal power 100µW with 0.5V supply
• Bondwire inductor or on-chip inductor
• 200MHz tuning range _at_ 500kHz resolution using 9
  bits capacitive bank
• Utilize this low power DCO in a reactive radio
  receiver

N. Pletcher
12
Whats Next Towards sub-100µW Transceiver
Integrated Silicon Clocks

• 16MHz micromachined resonators SiGe structural
  layer, low temp processing

1µW Low Power Osc
100µW Low Phase Noise Osc
B. Otis, N. Pletcher, E. Quévy
13
Thank You