An Overview of UltraWideband Research at Berkeley

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An Overview of Ultra-Wideband Research at Berkeley

• Ian ODonnell, Mike Chen, Stanley Wang, Bob
  Brodersen
• University of California, Berkeley

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Project Areas

• Integration of UWB transceiver in CMOS
• System simulations
• Complete transceiver design
• Antenna LNA baseband gain Pulser
• A/D
• Digital baseband
• Realtime simulation of UWB systems
• BEE FPGA array
• UWB frontend
• Spatial Channel Measurements

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UWB Integrated Transceiver Project
Targeting Sensor Network Application

• Specifications
• 100kbps over 10m with 10-3 BER
• 1mW total (TXRX) power consumption
• 0-1GHz bandwidth

First All-CMOS Integrated UWB Transceiver Aggressi
ve Low-Power Design Mostly-Digital approach,
simplify analog front-end Provide Flexible
Platform for Further Research
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Flexibility for UWB system design exploration

• Different antennas (with impedance matching to
  the LNA)
• Variable transmit power
• Variable pulse rates
• Digital back-end will contain a programmable
  pulse-matched filter
• Adjustable data recovery/synchronization blocks
• Independent synchronization and data PN sequences
• I/O to send the A/D data directly to an external
  digital backend (i.e. BEE) for more sophisticated
  signal processing.

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UWB Transceiver Prototype
Goal Tape-out Single-Chip Transceiver by end of
Summer
PMF
Data Recovery Synch Detect And Tracking
GAIN and FILTERING
S/H
A/D
CLK GEN
CONTROL
PULSE
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Antenna-LNA Co-design
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UWB Antenna

• UWB antenna for indoor wireless applications
• Broadband
• Omni-directional
• Small size
• Small size -- Narrowband
• Antenna Q (?3)/(antenna size)
• Almost impossible to have 50ohm radiation
  resistance over the whole bandwidth
• Small size -- Omni-directional
• Phase difference on the antenna is small

6cm Dipole Antenna Input Impedance
Resistance
Reactance
Reactance Dominates!
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Small Antenna Modeling
Take small Loop Antenna as an example

• E-fields in all directions are with almost the
  same waveform
• Only one resistor in our model
• By superposition, waveform across Rrad is equal
  to the far-zone E-fields
• Can estimate radiated E-field in SPICE

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RX LNA
Desirable Functionality

• Gain 10 V/V over 1GHz BW
• Noise Figure lt 10dB (Not Critical In an
  Interference Dominated Environment)
• Differential Input
• Handle Multiple Antennas (I.e. Current Loop
  and/or Dipole)
• Switch Bias On/Off within TWINDOW
• Fast Overload Recovery (Track Full- Scale 1GHz
  Sinusoid)

-

-

Implementation
May Build Two Amplifiers and Selectively
Connect/Enable for Experimentation
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Current-Reuse Technique
Shunt-Feedback
Common-Gate

• PMOS are added in as amplifying devices
• No extra DC current
• Gm gmn gmp
• Rin is halved
• Voltage gain is doubled
• NF decreased by 3dB
• BW decreased but OK

Rin 1/(gmngmp) Rin,diff 2/(gmngmp)
Rin 1/(gmngmp) Rin,diff 2/(gmngmp)
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UWB LNA Layout w/o Capacitors
Mb1 Mb2

• ST Microelectronics 0.13um CMOS triple-well
  process
• Layout area
• 59um x 45um
• Common-centroid layout for good transistor
  matching
• Dummy for good resistor matching
• Capacitors off-chip

Mp1
Mp2
Rf2
Mp1
Mp2
Rf1
59um
Mn2
Mn1
Mb3 Mb4
Mn2
Mn1
45um
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CMOS Analog Frontend
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Transceiver Analog Front-End

• Focus
• Low voltage, low power CMOS circuit design with
  few external passives (I.e. crystal)
• Accurate, flexible, controllable pulse
  reception window
• Antenna/circuit co-design
• Status
• Design Nearly Complete
• Some Layout Done
• Tape-out in Summer

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Pulse Reception
Parallel Sampling of Window of Time
time
TSAMPLE
TWINDOW
TPULSE_REP
time
Three Clocking Timescales TSAMPLE (ltns)
TWINDOW (10s ns) TPULSE_REP (100s ns)
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Oscillator Accuracy (Matching)
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Precision Component
0.1 1000 PPM
Crystal
10 PPM
TCXO
Drift lt 25ps Over Symbol
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Oscillator Precision (Jitter)
RMS Jitter lt 25ps Over Symbol
Ring Oscillators
LC Oscillators
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Spectrum Usage
Interferers TV 174-216MHz, 470-806MHz ISM
902-928MHz, 2.4-2.4835GHz, 5.725-5.850GHz Cell
phone824-849MHz, 870-893MHz Pager
929-930MHz PCS 1.85-1.99GHz Microwave Oven
2.45GHz
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A/D Bitwidth
1-bit A/D Is Adequate
Interference Dominates (Noise Figure Not
Critical)
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RX A/D Comparator requirement
1-Sigma VOFFSET for Fixed Tracking BW1GHz
1000
100
VOFFSET (mV)
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VOFFSET 20mV (w/ No Explicit Cancellation) for
CSAMPLE gt 10fF
1
1
1000
100
10
CSAMPLE (fF)
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UWB RX Baseband
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Transceiver Digital Back-End
Process 0.13um (ST Microelectronics) Size 3.3mm
x 3.3mm 245,000 Standard Cells Status In
Place-and-Route Stage
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Processing Gain

• Input Eb/No is -11dB. Results show 1024 chips is
  enough.
• (1) Acquisition mode, 400 chips is enough for
  suppressing the acquisition error below 1e-3.

(2) Data recovery mode, 100 chips could achieve
an uncoded bit error rate of 1e-3.
 
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Parallel v.s. Serial Acquisition

• Assume the worst case using 1024 PN chips, while
  pulse rate is equal to 100 ns. We need to choose
  somewhere in between.

(1) Acquisition Time
(2) Area Cost
Fully Parallel (500 mm2)
Serial (0.1sec)
Fully Parallel (0.1 ms)
Serial (5.8 mm2)
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Operation Mode - Tracking
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Area and power estimation
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Pulse Transmitter
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UWB Pulser/Antenna Co-design

• Large Current Radiator (LCR) as the UWB antenna
• Notch filter for FCC radiation mask

• H-bridge pulser to drive inductive load
• Flexible driving force by parallel structure

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H-bridge Simulation Results

• Doublet is generated
• Pulse-width 1nS
• Smoothed after low-pass filtering at the receiver

• Meet FCCs rule
• EIRP will increase when PRF(Pulse Repetition
  Freq) increases

VRrad
FCC Mask
Vfiltered
EIRP (dBm/MHz)
Time(ns)
Frequency (GHz)
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Driver Circuit Layout

• STMicroelectronics 0.13um CMOS process

• Chip area 0.49mm2
• 1.2V Vdd
• 2 drivers with enables -- Can either drive a
  monopole or dipole
• Each driver with 16 levels of driving capabilities

Driver