Transcript CMOS Transmitter Design for Low-Power Low Data

Ultra-Wideband
communication technology
for sensor network
applications
Julien Ryckaert
IMEC
[email protected]
The vision of
“Ambient Intelligence”
“An environment where technology is
embedded, hidden in the background”
Fred Boekhorst
Philips Research, ISSCC ‘02
Health Care of the Future
Fitness for you!
Increase Productivity
Home of the Future
This vision requires the massive
deployment of sensor nodes
Scavenger
Storage
Analog
& A/D
DC-DC
conversion
XTAL
Com.
Digital
Baseband
DSP
D/A
A/D
Sensor
Memory
Radio
Scavenger
Analog
& A/D
Storage
DC-DC
conversion
DSP
XTAL
Com.
Digital
Baseband
D/A
A/D
Sensor
Memory
Radio
Scavenger
Analog
& A/D
Scavenger
DC-DC
conversion
Storage
Storage
DC-DC
conversion
DSP
D/A
XTAL
XTAL
Com.
Digital
Baseband
A/D
Sensor
Memory
Radio
Com.
Digital
Baseband
DSP
D/A
Network
Analog
& A/D
A/D
Sensor
Memory
Radio
Scavenger
Analog
& A/D
Storage
DC-DC
conversion
DSP
XTAL
Com.
Digital
Baseband
D/A
A/D
Sensor
Memory
Radio
Scavenger
Analog
& A/D
Scavenger
DC-DC
conversion
Storage
Storage
DC-DC
conversion
DSP
D/A
XTAL
XTAL
Com.
Digital
Baseband
A/D
Sensor
Memory
Radio
Analog
& A/D
DSP
Com.
Digital
Baseband
D/A
A/D
Sensor
Memory
Radio
Scavenger
Scavenger
Storage
DC-DC
conversion
DSP
Com.
Digital
Baseband
D/A
Storage
DC-DC
conversion
XTAL
XTAL
Analog
& A/D
Analog
& A/D
A/D
DSP
Com.
Digital
Baseband
D/A
A/D
Sensor
Memory
Radio
Sensor
Memory
Radio
Point d’accès
A sensor node is a completely
autonomous device
clock
Communication
Processing
Sensing
Energy
Three major challenges in the
communication module
✗ Ultra-low power
✗ Ultra-small size
✗ Ultra-low cost
: >2 years autonomy
: non-invasive
: disposable
clock
Communication
Processing
Sensing
Energy
 Low communication performance : <100kbps
POWER CONSUMPTION
?
PERFORMANCE
In reality, the total Energy
consumption must be minimized
What does it cost to transfer a bit of
information?
Power consumption (Energy/time)
Data rate (bits/time)
but…
= Energy/bit
Power

Energy/bit
Data rate

Energy/bit
How does it look like today?
After CEA-LETI
Energy / bit (nJ/bit)
10E4
10E3
10E2
10E1
10E
0
50 Mbps
1Mbps
250kbps
10 to 150 kbps
Increasing data rate
The active time of the radio must be minimized!!!
POWER CONSUMPTION
UWB
?
PERFORMANCE
Traditional Communication
systems use continuous waves
NarrowBand Communication
time
frequency
Each user/application has its own
spectrum band
Impulse Radio UWB uses short
pulses
Pulse-based Ultra WideBand communication
time
Emitted power must be low
enough to avoid jamming
frequency
Activate the radio only when
needed
Power
Active
Active
Sleep
The active time of the radio is reduced:
“Radio duty-cycling”
FCC: UWB communication must be
done in the 3.1-10GHz band
-41dBm/MHz
FCC
1
3.1
10.6
Full-7GHz Band
-41dBm/MHz
1
3.1
F [GHz]
…
10.6
F [GHz]
Minimum 500MHz band
More users
IEEE standard for low data-rate
sensor networks
1s
1s
Burst
3% Active!
97% Inactive
Activate the transmitter only when
needed to achieve low-power
The standard imposes some
constraints on the signals
• Pulses are BPSK modulated
1
0
• Pulse repetition frequency multiple of
carrier frequency
Fcarrier = N x Fpulse
Overall transmitter architecture
Chip
31.2MHz
Div 16
499.2MHz
Programmable
Divider (DIV)
7:20
E-L
Detector
Digitally
Controlled
Oscillator (DCO)
RF LO
3-10GHz
DCO register
E/L
4
Burst Code
Trigger
Clock
31.2MHz
499.2MHz chip rate
Digital
Modulator
(DMO)
RFout
Data
DCO fine frequency
configuration bits
Enable
Control loop
CONTROL
LOOP
FPGA
Data
(ISSCC 07)
Time-domain measurement of
the output signal
1 0 0 1 1 1 0 1 1 1 0 0 1 1 0 1
Same energy efficiency as first transmitter!
Correlation can be done either
in Analog or in Digital domain
ADC
Decision
Analog
Correlation
Very precise timing  Power Hungry
ADC
Digital
Correlation
(Matched Filter)
High Sampling rate  Power Hungry
Decision
Full system block diagram
Analog Output
CAL
ADC
I/O bus
I
RFin
LNA
LO
Timing circuit
Q
Digital
Controller
(System
Configuration
and
Interfacing)
Serial/Par
Out
ADC
CAL
DL
DL
Clk/Rst
Clk
DL
DL
(ISSCC 06)
What about power consumption?
• State-of-art narrowband solutions (Zigbee):
– TX: 10mW
– RX: 2mW
• UWB solutions:
– TX: 0.5-1mW
– RX: 0.3mW
/ 10
UWB has other advantages
• Positioning by measuring the time of
arrival
DL
TX
RX
TX
DT
• Security: UWB power spectrum below the
background noise
Background noise (kT)
Other impulse Radio
implementations exist
• Example: MIT (US) proposes a similar concept:
But uses a proprietary UWB communication interface
Therefore the question: should
sensor networks be standardized?
• Pros:
– Interoperability (add nodes in the network)
– Market pressure decreases cost
• Cons:
– Solution biased by the “big ones”
– Security
– Less interferences (?)
Sandardization aspect is an old controversial
debate for healthcare wireless systems
Conclusions
• UWB offers today a 10x improvement on
power consumption.
• UWB has other interesting advantages in
the context of sensor networks: security,
positionning,…
• An IEEE standard exists today (IEEE
802.15.4a), but its use in wireless
healthcare systems is still a debate.