Transcript libo_20071016.ppt

An Integrated Solution for
Suppressing WLAN Signals in UWB
Receivers
LI BO
Motivation
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UWB system becomes more interested in
Wireless Personal Area Networks (WPAN)
due to its high bandwidth after federal release
the unlicensed spectrum in 3.1-10.6 GHZ
Wireless Local Area Network (WLAN) is
operated in 4.9-5.825 GHZ
Intermodulation products in UWB Band
Suppressing WLAN signal
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Third-order intermodulation
Second order intermodilation
It is a natural idea to suppress WLAN and
other noise to improve performance
Possible solutions
Off-chip pre-filter
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Increase cost due to additional external
component
signal lost
lower speed
Integrate a filter to avoid WLAN interferers
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Increase speed
Low cost
Wide-band filter VS tunable narrowband
filter
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Wide-band
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High order filter
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Need many inductor ( a lot of space)
Impairs gain of receiver
Tunable narrowband filter
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Can be easily implemented through low order filter
Must have tuning due to small band
Tunable narrowband filter receiver
scenario
Low Noise Amplifier (LNA)
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LNA will determine noise figure of receivers
Challenges in design LNA
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Input resistor need to be 50 ohms
Very low noise figure
Gain with high linearity which often measured in
IP3
Maximize output power
Low noise amplifier (LNA)
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L1,C1,L2
C2 use for
matching
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Inductively
degenerated
commonsource
amplifier
Lg is added to give flexibility to design\
Cascode circuit to imporve frequency
response
Notch filter simple example
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At resonant
frequency,
Zf is equal
to zero so
steal all
signals
Notch Filter design
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Two resonant
frequency
Q4 works as a
negative resistor
It is tunable
through varactor
Mixer
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A multiply circuit
R3,L4 are use to
isolate RF signal
L4 is 5 nH, an
area of 70x70
um2
LO input and output buffer
Chips
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Due to Sidewall capacity
of pad
Measured noise figure (NF)
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Parasitic resistance of notch filter
Poor model and layout of the varactor
Measured results
Performance
Conclusion
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Implement tunable filter idea to suppress
WLAN inference in 4.9-5.825 GHZ using
SiGe 0.35um technology
The LNA, Mixer and filter power
consumptions are 25.2,6 and 18 mW.
The NF is not coherent with design which
maybe due to poor model and layout of
varactor