Transcript 60 GHz wirless receiver frontend on 90 nm CMOS

A 1.2V, 60-GHz radio receiver
with on-chip transformers and
inductors in 90-nm CMOS
28th IEEE Compound
Semiconductor Symposium
David Alldred
Brian Cousins
Sorin Voinigescu
University of Toronto
Overview
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Motivation
Circuit blocks and schematics
Passive element design
Layout and fabrication
Measurement results
Conclusion
Motivation
Why 60-GHz radio?
• Enough bandwidth for 2+Gb/s data transmission
• Simpler radio architecture
• Smaller die (lower cost?) than at 2-10 GHz.
Why CMOS?
• 90-nm MOSFETs have fMAX > 200 GHz at 1V supply and 0.2mW/mm
• 90-nm n-MOSFETs have similar NFMIN as 200-GHz SiGe HBTs
• For large volume applications CMOS can be the lowest cost solution
ISCAS-07
Goal
RFIC-06
CSICS-06
Wireless Transceiver System
• Design and test receiver subsystem in digital CMOS
• Operating frequencies: RF: 60GHz, LO: 55GHz, IF:5 GHz
• Maximize Receiver Figure of Merit:
f * G * IIP3
FoM 
( F  1) * P
Downconverter Block Diagram
• Fully differential core except mm-wave interfaces
• Two on-chip 60-GHz baluns for SE-Diff. conversion
Circuit Blocks: LNA
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Two-stage cascode with middle inductor for NFMIN, S21
Biasing at 0.15 mA/mm ensures minimum noise in LNA
LVT devices to ensure operation from 1.2 V supply
Ported from 1.5V design in 90nm RF CMOS by T.Yao et
al. RFIC-2006
Circuit Blocks: Mixer
• Double-balanced Gilbert
cell for LO-RF leakage
• Design strategy:
minimize noise,
maximize linearity
• CM inductor for noise
and headroom
• Middle inductors
increase gain and
reduce noise
• Interdigitated diff-pair
layout sharing well
Circuit Blocks: LO buffer, IF buffer
LO Buffer
Output Buffer
• Differential CS topology for simplicity
• LO buffer designed as CML gate for fast switching
• IF buffer @ 0.3mA/mm for maximum linearity (determines
receiver linearity and drives 50-Ohm loads)
Passive Element Design
Inductors
2π inductor model
Vertically-stacked inductor
• Y-parameters from field solver (ASITIC)
• Broadband 2π-model extracted from simulated Y-params
• Skin effect included for 55GHz and 60GHz inductors
Passive Element Design
Balanced single-to-differential converter
Balun model schematic
Layout of verticallycoupled, two-layer balun
• Balun model adapted from
inductor π-model
• Mutual capacitances distributed
for balanced operation
Fabrication
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90nm GP CMOS (STM)
7M digital back-end
LVT transistors
fT/fMAX = 125/240 GHz
600x475 μm including all pads
Receiver Measurement Results
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RF = 60 GHz, IF = 5 GHz
VGS for min. NF50 is slightly below peak gain (fMAX) bias
Confirms Jopt =0.15 - 0.2 mA/mm even at 60 GHz
IF bandwidth is > 2 GHz centered at 4.5 GHz
Conversion Gain, S11 vs. RF freq.
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Peak gain of 21 dB at 52 GHz
Coincides with center frequency of S11
Input LNA inductor LG was 10% too high
Re(Zin) = 50 W @ 60 GHz.
Supply variation and LO power
• Operation verified over 1.1V to 1.5V range
• Noise Figure and Gain saturate for LO power > 2dBm
Linearity and LO-RF leakage
Performance Summary
Simulation Results
Parameter
Measured
Simulated
Frequency
60 GHz
60 GHz
Power Gain
16-20 dB
21 dB
NFMIN
5.5-7 dB
7.4 dB
P1dB
-21 dBm
-20 dBm
IIP3
-
-11.3 dB
Pdiss
60 mW
62.5 mW
Isolation (LO-RF)
< -94 dB
-120 dB
Area
0.6x0.48 mm2
0.6x0.48 mm2
• Results are very close to simulated value
• 6 dB lower NF than similar design in 150GHz SiGe
BiCMOS [M. Gordon, SiRF-06] but no on-chip VCO
Conclusion
• 60 GHz wireless receiver is feasible in 90 nm GP CMOS
• LVT devices critical for low-voltage/low-power
• Thick copper back-end was NOT critical
• Similar NF and P1dB to SiGe HBT technology but lower power
• Mixer and LNA consume only 20 mA (24 mW)
• Power could be further reduced with integration (buffers)
• Ultra small area of 0.28mm2 because of inductors
Acknowledgments
• CMC for fabrication and CAD tools
• Keith Tang and KenYau for help with
measurements
• OIT, CFI and ECTI for equipment
Thank you for your time.