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Leakage Power Minimization in
Ultra-wideband (UWB)
Communications Circuits
Edgar Wangolo
Presentation Plan
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UWB: concept and applications
Leakage power in sub-micron CMOS
Leakage minimization techniques
Application to PLL’s Prescaler
Project time table
References
UWB - Concept
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FCC: bandwidth is more than 25% of a center
frequency or more than 1.5 GHz
Typically implemented in a carrierless fashion
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Directly modulate an “impulse” with a very sharp
rise and fall time => a waveform that occupies
several GHz
Historically started with radar applications for
military use
UWB Vs. Narrowband
Communications
Narrowband
Communication
Ultrawideband
Communication
Time-domain behavior
1
1
0
Impulse
Modulation
Frequency-domain behavior
time
3
frequency
10 GHz
(FCC Min=500Mhz)
0
1
0
1
Frequency
Modulation
2.4
GHz
Operation Principles (“Spectrum Underlay“)
Narrowband (e.g GSM: +35 dBm/MHz)
Transmit
Power
Spectral
Density
WCDMA (typ. +15 dBm/MHz)
[dBm/MHz]
UWB (e.g – 41 dBm/MHz)
1
Frequency/GHz
10
Bandwidth (GSM : WCDMA : UWB) ~ 1 : 10 : 10000
UWB Spectrum
FCC ruling permits UWB spectrum
overlay
Bluetooth,
802.11b
Cordless Phones
Microwave Ovens
PCS
Emitted
Signal
Power
GPS
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802.11a
“Part 15 Limit”
-41 dBm/Mhz
UWB
Spectrum
1.6 1.9
2.4
3.1
5
Frequency (Ghz)
10.6
UWB Vs. Narrowband
UWB Transceiver
ADC
CLK
DIGITAL
GAIN
TX
ANALOG:
LNA
A/D
MIXER
Q
A/D
F SYNTH
D/A
PA
I
MIXER
D/A
DIGITAL:
Narrowband
Transceiver
UWB: Advantages
High Bandwidth, high data rate
 Low power spectral densities
 Simple, low cost
 Immunity to interference
Challenges:
 Low/Medium Range
 Signal to noise ratio is still an issue
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UWB: Applications
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Accurate positioning (through wall
radar, tracking)
High quality wireless video
Satellite communications
Air traffic control
Medical imaging
Etc.
PLL Block Diagram
30 – 40% of total power
input
PFD
up
down
Charge
Pump
Loop
Filter
%N
VCO
output
40% of total power
Today’s monolithic PLL’s use Phase Frequency Detectors
(PFD), charge pumps, and an optional frequency divider
in the feedback path.
Fin
N-digit Fractional-N Prescaler
Fout
2/3
2/3
2/3
2/3
P0
P1
P2
Pn
N=2n+2n-1Pn-1+2n-2Pn-2+…+2P1+P0
Circuit Power
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Dynamic Power:
determined by circuit
performance requirement.
Short_Circuit Power:
Both PU and PD circuit
partially conduct. Small
percentage. (<10%)
Leakage Power:
Increasingly important, and
many issues dependent,
such as device geometry,
temperature, doping,
processing and data pattern
dependent, etc. It is very
complicated and worthy to
study more to improve it.
Leakage Power Sources
W
I d  eff Cox (m  1)VT e
Leff
Vgs Vth
mVT
(1  e
Vds

VT
)
Sub-threshold
2
 V  Tox / V
I ox  K 2W   e
 Tox 
I pn  J leakage, p  n (e
qV
kT
 1) A
Gate oxide
PN
Leakage control: MTCMOS
Smart Switch Series (Triple-S)
RCSFF: Reduced-Clock Swing
Flip-Flop
Timetable
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Literatures:
Circuit Design:
Simulations:
Presentation:
Report:
March 10
March 16
March 28
April 6
April 20
References
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Hiroshi Kawagushi and Takayasu Sakurai, “A Reduced
Clock-Swing Flip-Flop (RCSFF) for 63% Power reduction”, IEEE
Journal of Solid State Circuits, Vol. 33, N05, May 1998
Tschanz et. Al, “Dynamic Sleep Transistor and body bias for
active leakage power control of microprocessor”, IJSSC, Nov
2003
J. T. Kao and A. Chandrakasan, “ Dual Threshold Voltage
Techniques for Low-Power Digital Circuits”, IEEE Journal of
Solid-State Circuits, July 2000