research in mixed-signal vlsi & signal processingdpwe/linked/eerschday-2008-09/... · 2008. 9....
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Research in Mixed-Signal VLSI & Signal Processing
Yannis Tsividis
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Why mixed-signal?
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Analog makes possible the communication of digital with the physical world:
Physicalworld
Digitalprocessor
Analoginterface
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As a result, digital has carried analog into new areas, e.g.
– Cellular telephony– Wireless LANs– “Digital” music systems – Automobile
Thus, systems in such areas are “mixed signal”.
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Today virtually every system is mixed-signal.
(But the users don’t know it.)
Analog Digital
Real World:
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• Novel signal processing techniques• Baseband and RF microelectronic filters• Low-power, low-voltage circuits• Hybrid computation
Recent research in our group
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Some examples of our recent work
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Project 1: Hybrid ComputerPh.D. student: G. Cowan
User interface (Matlab & Simulink)
Analog computer /math co-processor
Data acquisition
card
Test equipment
Computationalprograms
Signal sources
Digital computer
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Analog computer chip
• CMOS, 0.25 µm • 100 mm2 , 300mW• 106 transistors• Current mode• 80 integrators• 80 VGA / multipliers• 16 log blocks• 16 exp blocks• 64 programmable blocks
(sign, sat, abs, ramp, min, max, >, <, chop, T/H, S/H).
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Project 2: Wireless Receiver Front EndPh.D. student: N. Stanic
Project 3: Data Conversion and Digital Signal Processing Without Sampling
Ph.D. Students: Bob Schell, Maria Kurchuk,
Colin Weltin-Wu
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Continuous-timebinary waveforms
)(1 tbN−
)(2 tbN−
tt
t
)(tbN
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000
0 01
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)(txiw)(tw
tit
R∈it
∑=
−=N
nn
n tbtw1
)(2)((1)
Convert input to continuous-time digital form:
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Continuous-time DSP
NO CLOCK
Cont. time digital multipliers
Cont. time DAC
Cont. timeADC
D
D
1a
Ka
D
D
1a
Ka
T
T
0a0a
0a
1a
Ka
Cont. time single-bit digital delays
Cont. time weighted digital adder
Cont. time bits
IN
OUT
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Test chip (B. Schell, ISSCC 2008)
UMC 90nm 1P9M CMOS
Die area:1.3 mm x 1.3 mm
Active area: 0.64 mm2
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Total Power Consumption - Speech Input
Externally Linear (But Internally Nonlinear)
Systems
Ph.D. students: A. Klein, C. Vezyrtzis
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ADC DSP DAC
Classical system:
The new system is:•Externally linear•Internally nonlinear.
Our system:
g g/1ADC DSP DAC
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CLASSICAL SYSTEM:
OUR SYSTEM:
INPUT = 400 Hz SINUSOID WITH AMPLITUDE 30 dB BELOW FULL SCALE
MEASURED RESULTS FROM FPGAAT OUTPUT OF 8-BIT FIXED POINT REVERBERATOR
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Conclusions
• Analog will continue to thrive – thanks to digital technology:
– Digital will keep entering new applications, carrying analog along with it.
– Digital will keep making possible increasingly sophisticated auto-calibration of analog circuits.
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Future research in mixed-signal chips will be fueled by:
• Ubiquitous computing.• Ubiquitous communications.• Energy conservation.• Environmental needs.• New sensors and actuators.• Micromechanics.• Biology and medicine.• Nanoelectronics.