a fully integrated mimo multiband direct conversion cmos...
TRANSCRIPT
A Fully Integrated MIMO Multiband
Direct Conversion CMOS Transceiver
for WLAN Applications (802.11n)
Reviewed by Yu-Shan Wang
Arya Behzad et al. (Broadcom Corporation)
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 42, NO. 12,
DECEMBER 2007
Outline
• Introduction of 802.11n and MIMO
• Transceiver architecture
- TX,RX,PLL
• Calibration techniques
- LOFT, IQ mismatch
• Measurement Summary
• Conclusion
Comparison of WLAN standards
• IEEE 802.11n highlights:
– Spatial division multiplexing (SDM) through
the use of MIMO–OFDM
– Transmit beam forming
– Bandwidth expansion (40MHz)
– Advanced backend processing
802.11a 802.11b 802.11g 802.11n
Freq.
band(Hz)
5G 2.4G 2.4G 2.4G/5G
Data rate(bps) 6-54M 5.5-11M 1-54M >100M
Modulation OFDM CCK DSSS/CCK/O
FDM
OFDM
Why MIMO?
• Spatial multiplexing can increase the
channel capacity dramatically
• CSISO = BW log2(1 + SNR)
• CMIMO = min(n, m) BW log2(1 + SNR)
Transceiver
Receiver architecture
•Fully differential Direct conversion receiver
•HPVGA programmable gain of 0 to 30dB in 3dB steps
•4th order Butterworth LPF bandwidth 5,10,20MHz
• RX gain >100dB
•RX IIP3 of -12dBm @ high gain
•RX NF of 4dB @ maximum gain
Transmitter
•Direct conversion
•Driving 50 ohm load through a balun and internally matched to 100 ohm differential
•LOFT and IQ calibration
•OIP3 of +14dBm in the A-band while OIP3 of +16dBm in the G-band
•EVM <- 40dB for both bands
TX Mixer transconductor
PA
PLL
•Very low noise regulator
LO generation and distribution
•To avoid pulling effects : VCO operates at 2/3 the channel frequency for 11a
VCO operates at 3/4 the channel frequency for 11b/g
Calibration Techniquies
• LOFT @ TX
• IQ mismatch @ TX/RX
• LPF/HPF corner
• VCO
• Temperature sensor
Sources of LOFT in a direct-
conversion transmitter
• BB_LOFT: device offsets
• RF_LOFT: direct-coupling
Sources IQ imbalance in a direct-
conversion transmitter
•BB_IQ: Device mismatch,bias, mismatch
•RF_IQ: LO IQ inbalances and mixer IQ mismatch
Simplified block diagram of LOFT
and IQ imbalance estimation
circuitry
Gain control independent LOFT cancellation Algorithm
RX IQ calibration
Same core method:
image rejection is -35dBc
Same core method:
image rejection is -50dBc
Measurement results
Die
•Die area: 18mm2 ( compare to 11a: 12mm2)•Package: 165 ball fpBGA
Conclusion
• The highest performance, lowest power, smallest
area, multiband draft 802.11n transceiver published
to date has been implemented.
• 1.8V supply, 0.18um CMOS
• PHY rates > 270Mbps
• Effective throughput >190Mbps
• Can utilized in a multi-transceiver configuration to
build a larger MIMO system (4X4)
Questions?
Thank you