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7/13/2019 Tutorial Saponara Greco V6 17Aprile
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2012 IEEE Radar Conference, May 7-11, Atlanta
TUTORIAL
RF and Digital Components for Highly-IntegratedLow-Power RADAR
Sergio Saponara & Maria S. Greco
Department of Inform at ion Engineering
Univers i ty of Pisa .
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Speakers
Sergio Saponara is Associate Professor of ElectronicsMaria S. Greco is Associate Professor of Telecomunications
both at the
Department of Information Engineering
University of Pisa, via G. Caruso 16, 56122, Pisa, Italy
[email protected], [email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]7/13/2019 Tutorial Saponara Greco V6 17Aprile
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Outline of the tutorial
Scenarios and applications for highly-integrated
low-power RADAR
RADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADCUbiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADARHW-SW implementing platforms for RADAR
digital signal processing
Conclusions
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Outline of the tutorial
Scenarios and applications for highly-integrated
low-power RADAR
RADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADCUbiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADARHW-SW implementing platforms for RADAR
digital signal processing
Conclusions
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The semiconductor components market is growing..
driven by highly integrated digital-basedubiquitous systems realized in standard
Silicon (Si)-based technologies..
Source: iSuppli
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Technology evolution driven by large volumeHW-SW systems addressing societal needs
(health care, energy, security, safety, intelligenttransport..)
Source: World Semiconductor Trade Statistics
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Electronics evolution
Not only nanoscale CMOS but also System-in-Packageintegration of passives, RF & mm-Wave, high voltage,
sensors/actuators (MEMS) ..
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Ubiquitous RADAR applications
Although RADAR development was pushed by military applications in II
world war with high-power, large size and long-distance systems, today the
RADAR is becoming an ubiquitous technology adopted for:
Safer transport systems in automotive (automatic cruise control, urban
traffic warning, parking aid, obstacle detection), railway (crossing
monitoring, obstacle detection), ships
Info-mobility in urban, airport or port scenarios
Civil engineering, (static and dynamic structural health monitoring,
landslide monitoring, ground penetration for detecting pipes, electric
lines,.)
Distributed surveillance systems (smart cities, airports, banks, schools)
mm-wave body scanner for security
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Ubiquitous RADAR applications
Remote bio-signal detection for health care (heart rate, breath rate)
Elderly/infant assistance (fall detection, sudden infant death
syndrome,..)
Civil protection (e.g. detection of buried people in case of earthquakes,
or under the snow after an avalanche or other natural disasters, or even
in war scenarios)Contactless industrial measurements and in harsh environments
Through-wall target detection
RADAR sensing is suited to address societal needs ofsafety, security health-care, intelligent transport
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Ubiquitous highly-integrated low-powerRADAR
RADAR can become ubiquitous adopted as sensing system for large
volume applications?
RADAR as EM sensor can offer big advantages for large volume highly
integrated applications w.r.t. other technologies:
operations in all weather and bad light conditions
contactless sensing and no line of sight sensing
non ionizing radiations
ground penetrating capabilities
multi parameter sensing (target detection, distance, speed, angles)
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With respect to conventional RADARs for defense and civil applications,
with large transmitted-power x antenna aperture product, the realization ofhighly-integrated RADARs with low power consumption, size, weight andcost is needed to enable its ubiquitous adoption in largevolume markets
Transmitted Power < 10-15 dBm
Short wavelength for miniaturization (3.9 mm@77 GHz)
Range from < 1m to < 100-200 m
Detection also with low SNR of 10-20 dB
Cross section from tens of cm2to m2
DSP techniques to improve performance and solve range-speed
ambiguities
Receiver sensitivity down to -100 dBm
Multiple channels may be used for channel diversity gain
Ubiquitous RADAR design needs
43
2
)4( R
GGPP rttr
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Key enabling factor for the success of this scenario is the realization, inSi-based standard technologies, rather than using niche marketdedicated technologies, of integrated transceivers for the RF radar front-end and the implementation of computing intensive RADAR signal
processing algorithms in cost-effective and power-efficient embeddedplatforms
Advanced concepts for System-in-Package integration have to beexplored
Ubiquitous RADAR design needs
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At high frequencies (short wavelengthsof few mm) there is potential for high
miniaturization, even the antennaintegration
thanks to technology scaling Si-basedtechnologies are offering good
characteristics at microwaves and mm-waves
Frequency bands for highly integratedubiquitous RADAR
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Opportunities at mm-waves
Compared with visible light and infrared radar offer lower attenuation in
bad weather and bad light conditions
Due to high attenuation 60 GHz band (V Band) reserved for short
communication
At 77-81 GHz (W band) good opportunities for both LRR and SRR in mm-
wave domain
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Outline of the tutorial
Scenarios and applications for highly-integrated
low-power RADAR
RADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADCUbiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADARHW-SW implementing platforms for RADAR
digital signal processing
Conclusions
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Example architectures for integratedRADAR systems
RADAR as a mixed analog-digital system
Pulsed RADAR with homodyne receiver
Pulsed RADAR with super-heterodyne receiverPulsed RADAR with correlator-type receiver
From analog to digital down-conversion
FMCW RADAR with digital down-conversionDirect digital receiver
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RADAR as a mixed analog-digital signalsystem
DIGITAL
DOMAIN(RX signal
processing, TXwaveform gener, LO
synthesis, userinterface, antenna
switch control)
To the vehicle network
ADC
DAC
ANALOGDOMAIN
(PA, LNA, AGC,FILT, T/RSWITCH,MIXER)
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Pulsed RADAR architecturewith homodyne type receiver
Periodic transmission of a train of short pulses of peak power Pt with fpr
(frequency pulse repetition), transmitted Pavg depends of duty cycle
In integrated systems high peak power can be problematic limit on
duty cycling to achieve acceptable range performance
ToF analysis of the received echo pulses for target detection
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Pulsed RADAR architecture
Easier on-chip integration vs. a heterodyne architecture avoidingselective passive filters at high frequencies
Antenna array used in timed-division for TX and RX (T/R antenna
switch needed, switch needed also for LNA protection from PA out)
A/D and D/A converters (ADC, DAC)To reduce distortions DAC has to be of PAM type rather than PWM
(used in MCU)
ADC can operate at baseband (LO for I and Q down-conversion has
the same radar central frequency) or at IFSignal processing (waveform generation, pulse compression, filtering,
range-speed ambiguities resolutions, CFAR detection, tracking done
in digital domain)
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Heterodyne-receiver alternative
By sharing the conversion requirements among different blocks
operating at different frequencies, RF, IF, baseband better performancecan be achieved
Selective passive filters at high frequencies (e.g. for image frequency
rejection). On-chip or in-package integrated selective filters today
possible
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Trend from analog down-conversion
IF or RF input at the quadrature down-conversion system depending if
homodyne or heterodyne receiver is used
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.. to digital down-conversion
ADC operating at IF with digital based down-conversion (Numeric
Controller Oscillator NCO- needed plus digital decimation)
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FM-CW RADAR
Quartz
Osc
Phase
det.
frefLoop
filter
VCO
PA
77 GHz
Freq. divider
X
LO
LNARF
ampADCFFT &
logic
Modulation
control (B, Tm)
Interface
UserI/O
fbeat
f
t
fbeat
TOF
f
t
R
TOF=2R/c
f
t
TX RX
DSP
Target
Received signal at the ADC
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FM-CW RADAR
Separate antenna used for TX and RX due to continuous wave
Range and relative speed detection from batiment frequency analysis
(with FFT in digital domain)
The FMCW sweep frequency B and the time sweep Tm determine the
achievable range and speed resolution
Stable frequency synthesis based on PLL+VCO in analog domain
used in TX
ADC can operate at baseband or at IF
Signal processing and control (FMCW modulation control, filtering,
FFT, range-speed ambiguities resolutions, CFAR detection, tracking
done in digital domain)
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UWB Pulsed RADAR with correlator-type receiver
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Receiver-type correlation
The received pulse echo signal, amplified by the LNA is multiplied witha delayed replica of the transmitted pulses generated on-chip by a
Shaper circuit and integrated in the analog domain (low-rate ADC
needed) or in the digital one (high-rate ADC needed)
The amplitude of the signal at the output of the multiplier is related to
the target position.
Averaging a large number of pulses allows us to increase the SNR,
depending of integrator bandwidth and pulse repetition frequency
)log(10intB
fSNR PRimp
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RADAR with direct digital receiver
Aiming at a Software Defined Radio, in wireless communicationindustry there is lot of interest on direct digital receiver where the
ADC is moving towards the antenna.
The dream is that all signal processing (apart antenna impedance
matching and first amplification) is done in the digital domain and is
fully programmable/configurable
Whatsfor RADAR?
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RADAR with direct digital receiver
At least the LNA + RF Filter before the ADC is needed for optimal
impedance antenna matching, receiver Noise Figure, out-of-bandinterference reduction, and to adapt the weak receiver signals to the
dynamic range of the high-speed ADC
The mixer can be removed at UHF, L or S radar bands since Nyquist-
rate ADC exists capable of GS/sThe limit is that high-speed low-power ADC have low dynamic range
(typ 5-6 ENOB) posing a limit to RADAR needing wider bit range to
face clutter
High speed DSP needs high data transfer and storage (large memorysize) and high clock frequency thus increasing power consumption
High speed medium/high dynamic range ADC needs high power
consumption and hence a mixer should be reintroduced
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Main HW RADAR sub-blocks in analogdomain
Low Noise AmplifierAntenna switch
Power Amplifier
Mixer
Adaptive Gain Control (AGC) amplifier
Phase Locked Loop (PLL), Voltage Controlled Oscillator, Quartz
Oscillator, phase detectors, phase shifter, frequency dividers
Baseband amplifiers and filtersIntegrators
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Main HW RADAR sub-blocks in digitaldomain
ADCDAC
Numerical Controller Oscillator (NCO)
Digital delay lines (DLL), Digital clock manager (DCM)
Fast Fourier Transformer
Digital filters
Direct Digital Synthesis (DDS) for waveform generation
Other DSP blocksUser interface
Networking interface
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Radar Architectures bibliography
M. Skolnik, Radar Handbook, 3d Ed, McGraw Hill 2008M. Skolnik, Introduction to radar systems, McGraw Hill
J. Hasch et al., Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHzFrequency Band, IEEE Tran. Micr Theory and Tech, 2012
Y.-A. Li et al., A fully integrated 77 GHz FMCW radar transciever in 65 nm CMOS, technologyIEEE J. Solid-State Circuits 2010
C. Li et al., High-Sensitivity Software-Configurable 5.8-GHz Radar Sensor Receiver Chip in0.13um CMOS for Noncontact Vital Sign Detection, IEEE Tran. Micr. Theory Tech 2010
D. Zito et al., SoC CMOS UWB pulse radar sensor for contactless respiratory rate monitoring,IEEE Tran. Biomedical Circuits and Systems 2011
S. Saponara, B. Neri et al, Integrated 60 GHz Antenna, LNA and Fast ADC Architecture forEmbedded Systems with Wireless Gbit Connectivity, Journal Circuit Systems Computers 2012
B. Neri, S. Saponara, Advances in Technologies, Architectures and Applications of Highly-Integrated Low-power Radars, IEEE Aerospace Electr. Syt. Mag. 2012
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Outline of the tutorial
Scenarios and applications for highly-integrated
low-power RADAR
RADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADCUbiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADAR
HW-SW implementing platforms for RADAR
digital signal processing
Conclusions
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Integration levels and technologies forRADAR transceiver and ADC
Radar integration levels
System-on-board, -in-package, -on-chip
Integrated antennaTechnologies for integrated RADAR
III-V Transceiver
SiGe Transceiver
CMOS Transceiver
ADC
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RADAR integration levels
Different levels of integration are possible for low-power RADARsfrom single-board to single-chip systems with increasing
miniaturization but also increased technology complexity
System-on-a-single-Chip (SoC) where the RADAR is
completely contained in a single chip
System-in-a-Package (SiP) where the RADAR is realized using
multiple chips but embedded in a single package
Single-board RADAR where the system is realized using
multiple integrated circuits mounted on a single board
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Pro/Con of RADAR integration
Pro of Highly Integrated RADAR
Component assembly is minimized thus reducing cost and increasing
reliability and operating lifetime
Small size, small weight, low power consumption
Increased reproducibility and lower cost for large volume production
Con of Highly Integrated RADAR
IC design has high Non Recurring Costs (CAD tools and foundry cost,
design time and team design cost) cost is minimized only for large
volume production
A single technology can not offer optimal performance for all RADAR
subsystems (CMOS optimal for baseband DSP, not for antenna design
or RF power amplifiers or for mm-wave analog design)
Low transmit power limits possible applications to short range ones
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RADAR with high transmit power and large aperture antenna arerealized by assembling multiple electronic boards, each optimized
for a radar subsystem: antenna subsystem with feed, reflectors,
and scanning modules, TWT or Klystron as Power Amplifier
modules, MMIC for TX/RX module, multiple boards for digitization
and radar signal processing, User Interface and networking
The next step, for low-power ubiquitous radar, is assembling
all on the same single printed circuit board (PCB)
RADAR-System-on-a-Board
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RADAR-System-on-a-Board will assembly on the same board- a single chip of a few mm2 integrating the whole TX and RX chains
operating in the RF or mm-wave domain (CMOS or SiGe or MMIC in
III-V technologies)
- Solid-state power amplifier (depending on the transmit power needed)- a single chip for baseband digital signal processing (DSP, FPGA or
custom IC in CMOS tech.): waveform generation, matched-filtered,
pulse compression, range/speed ambiguities resolution, CFAR
- Memory modules (RAM and NV)- ADC/DAC module (if not integrated in the custom IC, CMOS tech.)
- antenna (printed on the PCB board if gain, beam-width are enough..)
RADAR-System-on-a-Board
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Thanks to submicron technology scaling CMOS is providing goodperformance also for RF and mm-wave low-power transceivers
The trend for the future is further increasing the miniaturization level
by integrating in a single-chip the radar transceiver plus the A/D and
D/A converters and part of the DSP chain, such as an FFT processorCMOS SOI offers further improved performance at high frequencies
and for the realization also of passive components (inductors,
capacitors, even V/W bands antennas if few dB gain are enough)
Only the power amplifier and the antenna will be off-chip
RADAR-System-on-Chip or in-Package
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RADAR-System-on-a-Chip or in-PackageUnless very low power and low antenna gain are required SiP is a more
viable solution for RADAR than fully SoC
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System-in-Package Technology Options
- Different System-in-Package technology option available or under
research for mm-wave low-power radar or radio applications:
- Integrated substrate and/or Multi Chip Module (MCM), even 3D
Huei Wang , IEEE SIRF 2010
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Integrated antennas
Towards high miniaturized systems the trend is integrating the antenna
- at board level (printed antenna on PCB boards)
- at package level (e.g. using Low Temperature Co-fired Ceramic LTCC
technology to realize multi-layer circuits with integrated passive
components including antenna)
- at chip level using MMIC or Silicon on Insulator technologies
The higher the frequency, the lower the wavelength (e.g for 77 GHz
radar or 60 GHz radio is few mm) and hence realizing an integrated
antenna becomes feasible
However lot of works still to do to achieve the high antenna gain
required by RADAR systems
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Example of a single-package chip andintegrated antenna
mm-Wave transceiver chip
with double-slot antenna
Lots of on-chip antenna designs at 60 GHz for short-range consumer radio (theantenna performance are less stringent than for typical RADAR systems)
Huei Wang , IEEE SIRF 2010
V-band transmitter and receiver with on-chip
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V-band transmitter and receiver with on-chip(MMIC) integrated antennas
Huei Wang , IEEE Microwave Mag. 2009
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RADAR antennas are typically realized off-chip. Long-range Radarautomotive applications (100m-200m) require antennas with high gain
and high directivity which can not be realized on-chip (e.g. up to 20-25
dB in literature with a patch or horn or dish antenna)
For RADARs operating at frequencies below 10 GHz, the wavelengthamounts to several cm and hence it is not convenient to integrate the
antenna due to the high silicon area occupied
Single-chip antennas integrated on MMIC or SOI technology recently
proposed in literature for 60 GHz and 77 GHz (few dB gain)
useful only for short-range applications and/or using special dielectric
lens antenna or smart resonator to improve the characteristics
Integrated antenna for RADAR systems
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Integrated antenna for RADAR systems
FMCW RADARs use separate TX and RX antennasPulsed RADARs can use the same antenna in time-division for TX/RX
By using an antenna array, a RADAR scanning effect can be obtained,
by realizing beam-forming in the analog domain (phase shifters) or in
the digital domain (digital beam-forming)Unlike beam-forming, which presumes a high correlation between
signals either transmitted or received by an array, the Multiple-Input
Multiple-Output (MIMO) concept exploits the independence between
signals at the array elements to improve radar detection performanceIn conventional single-antenna RADAR target scattering is regarded as
a parameter that degrades performance while MIMO RADAR takes the
opposite view capitalizing target scattering to improve performance
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LTCC-integrated antenna example
LTCC-integrated example of CW-radar antenna +transceiver for near-field highaccuracy measures in industrial scenarios (C. Rusch et al., IEEE EuCAP11)
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Example of PCB-integrated antenna for77 GHz automotive RADAR
Based on the FMCW principle, 4 77
GHz single microstrip patch antennas
combined with parasitic elements to
adjust bandwidth and beam-widthAntenna elements tilted by 45deg to
reduce interference from coming cars
The antenna elements serve as feeds
for a further dielectric lens resulting infour narrow beams
RADAR sensor size of 7.4 x 7 x 5.8 cm3 (J. Hasch et al., IEEE Tran. Micr Theory Tech, 2012)
E l hi i t t d t f
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Example on-chip integrated antenna for77 GHz automotive RADAR
On-chip antenna elements based on shorted /4 microstrip lines,formed by the top and bottom metal layers of the chip backend
Most of the radiation dissipated due to conductor and dielectric losses,
resulting in a low antenna efficiency (
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Performance of mm-Wave on-chipintegrated antenna
C. Person,IEEE BCTM 2010
Antenna type
F
(GHz) Tech Gain
BW
(GHz) Feeder Imped.
4 array Dipole 77 SiGe 2 2 Differential 45
Slot Dipole 24 GaAs 2 1.4 CPW 50
Zig zag 24 CMOS 1.5 N/A N/A 30
Aperture
Coupled Patch60 CMOS 7 7.8 Balanced 100
Dipole 60 SiGe 2.35 7 CPS 30
Slot Antenna 60 CMOS 10 5 N/A N/A
Cavity backed
folded dipole60 SiGe 7 18 CPS 50
Folded Dipole 60 SiGe 8 8 CPW 100
Yagi 60 SiGe 7 9.4 N/A 50
Spiral 60CMOS
SOI4.2 15 CPW 50
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Semiconductor material properties
III-V high mobility devices (GaAs, InP, ) suited for high performance
at high frequencies (electrons rather hole carrier-based devices)
Devices (es. GaN) with wide energy-bandgap and breakdown voltage
suited for high voltage high power (e.g. vacuum tube replacement in
high transmitter power radar)
Si devices suited for large volume low-cost since dominate basebandanalog&digital processing for TLC, Computers, Consumer Electronics
FET HBT b i
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FET vs. HBT basics
FET (Field Effect transistors) as MOS (Metal Oxide Semiconductor) or
HEMT (High Electron Mobility transistor) are unipolar devices (single-carrier: electrons in HEMT and NMOS, holes in PMOS) while HBT is bipolar
(holes and electrons)
HBT and FET can act as digital (on/ff) or analog devices (current generator
controlled by an input current HBT or an input voltage FET)HBT has an exponential drive characteristics while for FET is quadratic
HBT has higher transconductance (gain)
HBT has a resistive input impedance while for FET is capacitive FET has
lower power consumption in standby modeFET has lower noise at high freq (but it suffers of 1/f noise at low freq)
HBT are vertical integrated devices (high current density) while low-power
FET are planar devices (higher integration density and easier scaling)
Semiconductor technologies for RADAR
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Semiconductor technologies for RADARtransceivers and ADC
In highly integrated low-power radar vacuum-tube technologies
(Traveling Wave Tube, klystron, or magnetron,..) adopted for high power
high performance RADAR transmitter are completely avoided
Competing technologies are only solid state ones:- Monolithic microwave integrated circuits (MMIC) in compound III-V
semiconductors such as GaAs, In-P using High Electron Mobility FET
Transistors (HEMT)
- For Power amplifier interest on GaNand SiCis increasing- SiGe HBT (hetero-junction bipolar transistor) or BiCMOS (bipolar-
MOS) IC
- Si CMOS (N- and P- MOS) technologies IC
- CMOS SOI (Silicon on Insulator)IC
C i h l i
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Competing technologies
C ti t h l i
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FTGain/NF
ratioCost
Power
ConsumptionSuited for
BJT High High Medium High Analog, RF
CMOS Medium Medium Low Low Digital
BiCMOS High High Medium Medium Analog, RF,mixed-signal
HEMT Very High High High Medium mm-wave
Competing technologies
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State of the art and trends in RADAR design
III-V MMIC (Monolithic Microwave Integrated Circuit) for radio/RADAR at
high frequencies developed since 70s-80s (dedicated US funding
programs for MMIC tech)
MMIC are now a mature technology, offering for analog circuitry (active
and passive components) at microwaves and mm-Waves best in class
performances (max Ft, NF and gain of LNA, gain and Psat of the PA)
MMIC dominates high-end transceivers from tens of GHz to THz
Most of MMIC are in GaAs technology (automotive RADAR front-end at
77/79 GHz, 60 GHz applications, 94 GHz imaging, Ka-, V-, W-Radar)
100-nm HEMT GaAs and 500-nm InP HBT tech. available
III-V MMIC
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State of the art and trends in RADAR design
Limits of poor digital and mixed-signal integration capability not
suited for low-cost, large volume, digital-based applications
Since 2005 III-V HEMT devices with Ft (the frequency at which the short-
circuit current gain is 1) of 700 GHz are available
Today we are in the THz domain
However due to niche market applications, and higher device size, the
cost of ICs with III-V technologies is higher than that of silicon
technologies. While such cost is affordable in military or space
applications, for low-cost low-power civil radar applications silicon
technologies must be used
III-V MMIC
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State of the art and trends in RADAR design
Si-based technology dominate electronic industry for baseband signalprocessing and IF (BB and IF circuitry integrated in the same SoC)
Since 2000 Si-based technologies (SiGe bipolar or CMOS) used for
telecom RF IC (cellular phone transceivers, WLAN, Bluetooth, UHF
wireless sensors)Recent technology scaling proves the potential of CMOS, CMOS SOI or
BICMOS also for mm-Waves. Si-based mm-wave SoC developed in
recent years with commercial technologies for automotive RADAR (24
GHz and now 77/79 GHz) or TLC radio (60-GHz short-range)
Technologies: SiGe BiCMOS 130 nm, 180 nm; CMOS/CMOS SOI 130
nm, 90 nm, 65 nm, 45 nm, 32 nm, 28 nm; FDSOI at 28 nm and smaller
SiGe BiCMOS 130 nm, 180 nm or CMOS 90 nm, 65 nm used for RADAR
Si-based IC
MOSFET HBT d BiCMOS f RADAR d i
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In RADAR design HBT are more suited for high-frequency analog circuitry
ensuring higher gain and cut-off frequency, lower Noise Figure (NF)
MOSFET are more suited for the base-band DSP due to lower power
consumption, easier device scaling, higher integration levels, lower cost
SiGe BiCMOS (Bipolar Complementary MOS) allows the co-integration of
BJT for high-frequency applications and MOS devices for digital circuitsalthough at higher cost
At the state of the art the SiGe BiCMOS technology, with 130 nm
transistors channel length and an Ft of 230 GHz, offers a good trade-off
between cost and performance for single-chip mm-wave RADARtransceivers. Several transceivers at 24, 77, 90, 120 GHz have been
proposed in literature using SiGe BiCMOS technology
MOSFET, HBT and BiCMOS for RADAR design
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MOS technology dominates DSP
MOS h l d i
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MOS technology dominates memory
Thanks to technology scaling
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Thanks to technology scalingCMOS becomes suitable also for mm-waves
For future, for large volume applications (60 GHz radio, RADAR?) the
trend will be using CMOS also for mm-wave circuits. As an effect of devicescaling a Ft higher than 150 GHz can be obtained
Realizing a mm-wave transceiver in scaled CMOS technology, as baseband
DSP, entails a lower area, higher integration and lower cost for large
volume markets but also lower performance vs. 130nm BiCMOS SiGe tech
Huei Wang , IEEE SIRF 2010
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Technology benchmark - oscillator
Oscillator phase noise (at 1 MHz from the carrier) vs. operating frequency
in mm-wave bands in various technologies
CMOS has comparable performance up to 70 GHz
A. Scavennec et al.,IEEE Microwave Mag. 2009
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Technology benchmark - oscillator
Oscillator output power (0 dBm=1 mW) vs. operating frequency in mm-
wave bands in various technologies
III-V devices have best in class performance, up to several hundreds of
GHz, CMOS realizable within 100 GHz but at lower performance
A. Scavennec et al.,IEEE Microwave Mag. 2009
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Technology benchmark Power amplifier
On-chip mm-wave Power Amplifier is a big issue in CMOS
technology considering that from RADAR equation the range
capability heavily depends on transmitted power levels
A. Scavennec et al.,IEEE Microwave Mag. 2009
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Summary of GaAs vs. Si-based transceivers
i f diff d
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SiGe processes from different vendors
Most offers bipolars and FET and passive components
(J. Hasch et al., IEEE
Tran. Micr Theory Tech, 2012)
i
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SiGe Ft vs. Ic
Technology evolution allows for higher ft at a given current or the same ftfor lower current: this reduces power consumption, power supply andthermal issues reducing size and cost and increasing reliability in harshenvironments
(J. Hasch et al., IEEETran. Micr Theory Tech, 2012)
SiG P A lifi bili
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SiGe Power Amplifier capability
SiGe vs. CMOS vs. III-V technologies
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SiGe vs. CMOS vs. III V technologiesLNA Ft and NF
For applications at mm-Wave bands lower NF expected for SiGe and CMOShence the same performance available with lower transmit power and hencesmall size and lower costs
Source: International technology Roadmap for semiconductors (ITRS)
CMOS bilit LNA (G i )
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CMOS capability- LNA (Gain)
State-of-art designs up to 10-20 GHz in CMOS technology have good
performances: gain higher than 20 dB (L, S, C, X, Ku bands)At higher frequencies the performances start decreasing.Around 77 GHz (W-band) acceptable but non optimal performance areachieved today (gain lower than 20 dB)
10
15
20
25
1 10 100F (GHz)
Gain,dB-CMOSLN
A
CMOS bilit LNA (NF)
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CMOS capability- LNA (NF)
State-of-art designs up to 10-20 GHz (L, S, C, X, Ku bands) in CMOS
technology have optimal performances: NF lower than 4 dBAt higher frequencies the performances start decreasingAround 77 GHz (W band) acceptable but non optimal performance areachieved today (NF higher than 4 dB)
0
2
4
6
8
10
1 10 100F (GHz)
NF,dB-CMOSLN
A
CMOS bilit PA
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CMOS capability- PA
In L and S band an integrated PA up to 1 W peak power is possibleThe peak power of integrated PA decreases with frequencyAt high frequency (77 GHz or higher, W band ) the peak power is < 10 dBm (10 mW)Only short range applications are possible with high duty cycle or external off-chipPA are needed
0
510
15
20
25
30
35
1 10 100 1000F (GHz)
PoutTX,dBm-
CMOSP
A
I i Si b d t i
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Issues in Si-based transceivers
Another issue in Si-based transceivers is the design of low-losses passive
Components such as Coplanar stripline or waveguides (CPS/CPW)
At mm-Wave frequencies due to very short wavelength the antenna
integration is possible but low efficiency and low gain are main concerns
Solutionmigration to SOI technologies
CPW CPS d A t I CMOS SOI
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CPW, CPS and Antenna In CMOS SOI
In SOI technology the high resistivity of the substrate on which n- and
p-MOSFET are created allows dielectric isolation of circuit elements
Junction capacitances are reduced increasing maximum operating freq
Noise coupling between digital and analog parts integrated in the
same chip is reduced
The performances of CPS, CPW or antennas in SOI CMOS are improved
due to a reduced amount of energy loss in the supporting substrate
I t t d t i CMOS SOI
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Incidence of substrate resistivity on achievable radiation efficiency and gain
(bulk 20 /cm, SOI > 1000 /cm)
Integrated antenna in CMOS SOI
F. Gianesello,IEEE SOI 2010
Q lit f t f i d t i CMOS SOI
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Quality factors of inductance in CMOS SOI
F. Gianesello, IEEE SOI 2010
CMOS SOI useful also for high speed digital
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g p gapplications vs. bulk CMOS
P. Simonen, IEEE IMC 2001
Antenna in CMOS SOI
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Single-chip integrated antennas on 65 nm CMOS SOI recently proposed inliterature: a double-slot antenna with CPW feed, tunable to operate indifferent mm-wave frequencies has been proposed with a gain of 4.4 dB (at60 GHz) and an area occupation of 1 mm2
Antenna in CMOS SOI
Antenna in CMOS SOI
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Antenna in CMOS SOI
ADC main cost figures
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ADC main cost figures
The ADC is gaining a key rile in radar system due to trend of digitization
of the signal processing functionalities
Main cost figures of interest are:
Bits (Effective number of bits ENOB- rather than nominal bits)
Sampling frequency, Number of channels
Integral and differential non Linearity (INL, DNL)
Signal-to-Noise and Distortion Ratio (SNDR)
Spurious Free Dynamic Range (SFDR)Aperture uncertainty
Area, power consumption
ADC RADAR requirements
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ADC RADAR requirements
RADAR architectures may require ADC operating at intermediate
frequency and not only at base band frequency hence sampling rates upto hundreds of MS/s can be required in highly digitized radar (in
ubiquitous low-power applications the rate several tens of MS/s)
The number of ADC channels depends of the radar architecture (1 or 2
for I-Q for each of the K radar channels, e.g. 4 in last LRR automotive
Bosch radar)
The bit resolution is typically higher than 10 b, eg. a nominal 14b -16 b
required for 12 b-14 b ENOB (at least 70 dB dynamic range)
Specs on non linearity and aperture uncertainty ta depends, together
with ENOB bits N, also on the target SNR level
Comparing performance of different
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architecture types
L . Bin et al., IEEE Signal Proc. Mag., 2005
Absolute data not updated (see
next slide) but useful relative
architecture comparison
ADC Performance available (2011)
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ADC Performance available (2011)
M. Mishali et al. IEEE Signal Proc. Mag. 2011
ADC Conclusions
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ADC Conclusions
ADC sampling at several GS/s available but too-high power
consumption per channel and too low bit resolution for typical radar
dynamic range and SNR requirements Mixer is needed, full-
digital radar is not convenient
IF ADC can reach the required bit resolution and sampling rate with
good power performance (e.g. 100 MS/s, 16-b nominal at least 14ENOB) with power consumption within hundreds of mW
Pipelines or time-interleaved SAR can be suited architectures
Figure of Merit (FoM) in scaled CMOS technologies can be as low as
fJ to pJ per conversion-step
RADAR Technologies Recent bibliography
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RADAR Technologies Recent bibliographyJ. Hasch et al., Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHzFrequency Band, IEEE Tran. Micr. Theory and Tech, 2012
T. Mitomo et al., A 77 GHz 90 nm CMOS transceiver for FMCW radar applications, IEEE J. Solid-State Circuits 2010
Y.-A. Li et al., A fully integrated 77 GHz FMCW radar transciever in 65 nm CMOS, technology,IEEE J. Solid-State Circuits 2010
W. Menxel et al., Antenna Concepts for Millimeter-Wave Automotive Radar Sensors,Proceedings of the IEEE, 2012
V. Giammello et al., A Transformer-Coupling Current-Reuse SiGe HBT Power Amplifier for 77-GHz Automotive Radar, accepted on IEEE Tran. Micr. Theory and Tech.
B. Neri, S. Saponara, Advances in Technologies, Architectures and Applications of Highly-Integrated Low-power Radars, IEEE Aerospace Electr. Syt. Mag. 2012
B. Brannon et al., Analog devices AN-501,Aperture Uncertainty and ADC System Performance
M. Mishali et al., Sub-nyquist sampling, IEEE Signal Proc. Mag. 2011
L . Bin, et al., Analog-to-digital converters, IEEE Signal Proc. Mag., 2005P. Harpe et al., A 7-to-10b 0-to-4MS/s Flexible SAR ADC with 6.5-to-16fJ/conversion-step, IEEEISSCC 2012
Bei Yu et al, A 14-bit 200-MS/s Time-Interleaved ADC with Sample-Time Error Detection andCancelation, IEEE ASSCC 2011
Y. M. Greshishchev, A 40GS/s 6b ADC in 65nm CMOS, IEEE ISSCC 2010
RADAR Technologies Recent bibliography
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RADAR Technologies Recent bibliographyD. Liu et al., Integration of Array Antennas in Chip Package for 60-GHz Radios, Proceedings ofIEEE 2012
F. Gianesello, SOI CMOS Technology for Wireless Applications: Current Trends and Perspectives,IEEE Int. SOI conf. 2010
C. Person, Antennas on Silicon for millimeter-wave applications status and trends, IEEE BCTM2010
A. Scavennec et al., Semiconductor technologies for higher frequencies, IEEE Microwave
Mag. 2009
Huei Wang, Current status and future trends for Si and Compound MMICs in millimeter waveregime and related issues for System on Chip (SoC) and/or System in Package (SiP), IEEE SIRF2010
S. Saponara , B. Neri et al, Feasibility study and on-chip antenna for fully integrated RFID
tag at 60 GHz in 65 nm CMOS SOI, IEEE RFID-TA 2011
S. Saponara, B. Neri et al, Integrated 60 GHz Antenna, LNA and Fast ADC Architecture for
Embedded Systems with Wireless Gbit Connectivity, Journal Circuit Systems Computers 2012Huei Wang et al., MMICs in the millimiter-wave regime, IEEE Microwave Mag. 2009
P. Simonen, Comparison of bulk and SOI CMOS technologies in a DSP processor circuitimplementation, IEEE ICM 2001
C. Rusch et al., W-Band Vivaldi Antenna in LTCC for CW Radar Near field Distance Measurements,IEEE EuCAP 2011
Outline of the tutorial
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Outline of the tutorial
Scenarios and applications for highly-integrated
low-power RADARRADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADCUbiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADAR
HW-SW implementing platforms for RADAR
digital signal processing
Conclusions
Ubiquitous low-power RADAR
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q parchitecture case studies
Why a RADAR as contactless health sensor?
UWB pulsed bio RADAR
Doppler bio RADAR
Why a RADAR for automotive driver assistance?Standards, frequency and technology selection
Automotive RADAR spec and commercial devices
FMCW RADAR architectureSiGe automotive RADAR
CMOS automotive RADAR
Needs for health monitoring
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Needs for health monitoring
Due to aging population and needs of national health system cost
reduction there is high interest in monitoring electronic health devices,
specially for heart or respiratory pathologies (CHF, BPCO)
A low-cost RADAR can be used as contactless sensor for monitoring
heart rate or breath rate in patient with cardiopulmonary illness or to
monitors babies while sleeping against sudden infant death syndrome
Acquired radar data are then processed by an home gateway an send
to Hospital Information Server
Why RADAR for vital signs sensing
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Why RADAR for vital signs sensing
A RADAR can sense the mechanical activity of heart of chest instead
of the electrical one and from that the heart or breath rate can be
detected and estimated
The radar bio sensor can ensure continuous home monitoringavoiding wires, gels, LOS requirement, electrodes of conventional
solutions based on SpO2 measures and multi-lead ECG acquisition
(prone to electrode error positioning when done outside hospital )
Sensor radar requirements are low-power and high miniaturization
for portability/wearability, short-range, low cost for large volume
marketCMOS silicon integrated approach should be followed
No ionizing effect with low-power pulse RADAR
Which RADAR architecture?
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Recent proposals based on Ultra Wide Band pulsed RADAR (within3-10 GHz range) for very low power and low complex short-range
(tens of cm) contactless vital sign detection
Correlator-type receiver (Zito, De Rossi, Neri, architecture 2007-
2010, implementation in 90 nm CMOS 2011-2012), (Ta-Shun Chu etal., 130 nm CMOS implementation in 2011)
Doppler pulse radar based on transmission of un-modulated pulse
train and the analysis of the received echo phase modulated by the
chest/heart movement (Dracourt 2004, several works by J. Li, J. Lin
et al.). Various designs at 450 MHz, 1.6 GHz, 2.4 GHz, 5.8 GHz in
various technologies (250 nm CMOS and BiCMOS, 130 nm CMOS,..)
Which RADAR architecture?
UWB pulse RADAR
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UWB pulse RADAR
Very low power spectral density (-41.3 dBm/MHz from 3.1 to 10 GHz,
14 bands each of 500 MHz) ETSI/FCC regulation
Robust against interference
No ionization effect
Transciever activated only when needed (low power consumption due
to low duty cycling)
UWB pulse RADAR
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p
Due to low power the RADAR is limited to detection of heart/breath
rate of few Hz, at distances of tens of cmSingle TX/RX antenna multiplexed in time
Transmitter: pulse generator in the TX path transmits short pulses,
typically 200-400 ps, towards the human body with a pulse repetition
frequency (fPR) > 1 MHz so that the heart can be considered motion-less between consecutive pulses. The energy level of each pulse
amounts to few pJ
Zito et al., IEEE TBCS, 2011
UWB pulsed RADAR
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p
Low-complex cross correlation receiver architecture (differential path to
improve EMI robustness)
The output signal is modulated by the heart movement, acting as a target
with a cross sections of tens of cm2
After a TOF dependant on the target distance (e.g. few ns for 15-30 cm
distance) the signals reflected by the target is captured by the RX antenna
Radar working in ranging mode (delay varied to span the range of interest
and identify the target) or tracking mode (once detected, the delay is fixed
for target tracking
Vo (t) at multiplier output
Vout (t) at integrator output
Receiver-type correlation
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yp
The signal amplified by the LNA is multiplied with a delayed replica of
the transmitted pulses generated on-chip by a Shaper circuit
The amplitude of the signal at the output of the multiplier is related to
the heart position. Since vital signs vary within a few Hertz, an
integrator 3-dB band (Bint) of 100Hz allows an accurate detection.
Averaging a large number of pulses allows us to increase the SNR (e.g.
the SNR improvement is 40 dB with Bint=100 Hz and fPR=1 MHz)
)log(10intB
fSNR PRimp
Flicker noise issue at receiver
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At the low frequency (DC-100 Hz) of the baseband bio-signal the MOS
transistors used for RADAR-on-chip integration suffer 1/f flicker noise,much higher than thermal noise (KTB term)
The total NF of a multi-stage RX path is
To have NFtot~NFLNAa gain of at least 20 dB is required for the LNA stageprovided that NF2
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Pulse generator based on triangular pulse generation and shaping networks:two triangular pulsed (delayed by a pulse periods) generated and shaped bya CMOS differential pair
Performance of state of art UWB radars
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fPR in the range 1-10 MHz, pulses of 300-400 ps and 7-8 pJ energy
The baseband digital processing can be realized with a simple MCU
since low-speed ADC is required (12bit ADC in ISSCC11), low data rate
serial connection, only control tasks to be implemented
Whole chip by Zito et al. in 90 nm CMOS has
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pp
In DR for noncontact vital sign detection an un-modulated pulse
signal is transmitted toward the human body, where it is phase
modulated by the physiological movement, then reflected and
captured by the radar receiver (h and r are heart and respiratory
rate respectively)
C. Li et al., IEEE TIM 2010
Doppler Bio RADAR
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pp
Using the same un-modulated TX signal as the RX LO signal, the
receiver down-converts the received signal into baseband with no
frequency offset. Here it is digitized and the physiological movement
(i.e., heartbeat and respiration) can be identified by DSP (FFT or
wavelet proposed in literature)
C. Li et al., IEEE Tran. Micr. Theory Tech. 2010
Doppler Bio RADAR
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pp
A pulse doppler RADAR with 5.8 GHz central frequency and 1 GHz
bandwidth has been realized in 130 nm CMOS technology powered
by 1.5V batteries and using direct conversion quadrature architecture
The LNA has 2.56 dB NF and 24 dB gain
The system is sized to ensure 10-20 dB SNR, using a baseband
sampling rate of 20 Hz (ADC is sized for 1 kHz)
The whole RX chain has min 37 dB gain, -32 dBm P1dB and a
sensitivity of -101 dBm
Off-chip 2x2 patch antennas (separate for TX and RX) were used
With 7 dBm output power detection up to 3 m can be done
The received power is from -37 dBm to -61 dBm when the target
distance increases from 50 cm to 2 m
Vital Signs Detection RADAR Bibliography
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D. Dracourt et al., Range Correlation and I/Q Performance Benefits in Single-Chip Silicon DopplerRadars for Noncontact Cardiopulmonary Monitoring, IEEE Tran. Micr. Theory Tech 2004
D. Zito et al., SoC CMOS UWB pulse radar sensor for contactless respiratory rate monitoring, IEEE
Tran. Biomedical Circuits and Systems 2011C. Li et al., Accurate doppler radar noncontact vital sign detection using the RELAX algorithm, IEEETran. Instr. and Measur. 2010
C. Li et al., Radar Remote Monitoring of Vital Signs, IEEE Microwave Mag. 2009
D. Zito et al., A 90nm CMOS SoC UWB pulse radar for respiratory rate monitoring, IEEE ISSCC11
Ta Shun Chu et al., A short-range UWB impulse-radio CMOS sensor for human feature detection,
IEEE ISSCC11G. Reyes et al., VitalTrack: a doppler radar sensor platform for monitoring activity levels, IEEEBioWireleSS 2012
M. Mercuri et al, SFCW microwave radar for in-door fall detection, IEEE BioWireleSS 2012
Tariq et al., Vital signs detection using Doppler radar and continuous wavelet transform, IEEEEuCAP 2011
A. Lazaro et al., Vital signs monitoring using Impulse Based UWB Signal, IEEE EuMA 2011
G. Blumrosen et al., Noncontact tremor characterization using low-power wideband radartechnology, IEEE Tran. Biomedical Eng. 20120
C. Li et al., High-Sensitivity Software-Configurable 5.8-GHz Radar Sensor Receiver Chip in 0.13umCMOS for Noncontact Vital Sign Detection, IEEE Tran. Micr. Theory Tech 2010
C. GU et al., Instrument-based noncontact doppler radar vital sign detection system using
heterodyne digital quadrature demodulation architecture, IEEE Tran. Instr. and Measur. 2010
Automotive RADAR Why?
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y
Automotive RADARs as core sensor (range, speed) of driver assistance
systems: long range (LRR) for Adaptive Cruise Control, medium range(MRR) for cross traffic alert and lane change assist, short-range (SRR)
for parking aid, obstacle/pedestrian detection
W.r.t. to other sensing technology RADAR is robust in harsh
environments (bad light, bad weather, extreme temperatures)Multiple RADAR channels required for additional angular information
Data fusion in the digital domain with other on-board sensors
Automotive RADAR a bit of Story
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First tentative for mm-wave automotive RADAR since 70s (but
integrated-unfriendly technologies lead to large size, high cost)Since 1998-1999 first generation of radar sensors (Daimler, Toyota)
Since 2000 MMIC GaAs-based radar in premium cars
Last generation based on 180/130 nm SiGe chipset and advanced
packaging with integrated antenna commercially available (e.g. Bosch)Radar CMOS transceivers recent announced in 65 nm and 90nm
High RADAR frequency (small ) allows small size and weight, highly
integration with SiGe and future CMOS tech. will reduce assembly and
testing costs and hence final user cost much below US$1000Market expanding at 40%/year and is expected increasing with all
premium/middle cars having a RADAR in next years (7% of all vehicles
sold world-wide, mainly in Europe, Japan and US, will have RADARs)
Automotive RADAR Regulation
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24 GHz and 77 GHz are the dominant bands for automotive
77-81 GHz is promising since offers 4 GHz bandwidth
Automotive RADAR 24 vs. 77 GHz
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77 GHz is more challenging for designers: given the same technology
node performance (gain, NF, ..) at 24 GHz are better but 77 GHz RADARreduce size, volume, weight and hence cost
77 GHz offers more opportunity for high performance RADAR design:
is 3 times smaller (few mm) smaller antenna size for a given beam-
width spec and/or better angular separability for the same sizeCombination of high transmit power and high bandwidth available at 77
GHz for long range operation and fine distance separability
Due to SiGe and CMOS technologies evolution 77 GHz is affordable
77-81 GHz (under regulation worldwide) offers 4 GHz Bandwidth withEIRP max PSD of - 3dBm/MHz (-9 dBm/MHz outside the vehicle)
Automotive RADAR Technical spec
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(J. Hasch et al., IEEETran. Micr Theory Tech, 2012)
Automotive commercial RADARs
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Product size is in the order of 7 cm per side in LRR, 5 cm per side or lower
in MRR and SRR
Products exist with mechanical (slowly, increased size) or electronic beamforming (increased electronic complexity affordable in new tech nodes)
Multi channel transceivers required
All use FMCW RADAR technique
(J. Hasch et al., IEEETran. Micr Theory Tech, 2012)
FMCW Automotive RADAR principle
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Received signal at the ADC
Quartz
Osc
Phase
det.
fref Loopfilter
VCO
PA
77 GHz
Freq. divider
X
LO
LNARF
ampADCFFT &
logic
Modulation
control (B, Tm)
Interface
UserI/O
fbeat
f
t
fbeat TOF
f
t
R
TOF=2R/c
f
t
TX RX
DSP
Target
FMCW Automotive RADAR equations
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43
2
)4( R
GGPP rttr
FFT
r
BWNFTK
PSNR
r
dvf 2
2)(
2
ffB
cTR cpi
2
)(
2
fff
cvc
R
Receiver power and SNR (min 10 dB required)
Range and relative speed detection from batiment frequency analysis
(with FFT in digital domain)
The FMCW sweep frequency B and the time sweep determine the
achievable range resolution and speed resolution
Automotive RADAR Technology Selection
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Automotive RADAR based on GaAs MMIC in production, multiple chips
and boards needed thus increasing assembly and testing costLast generation based on SiGe chipset (HBT or BiCMOS): less ICs thus
reducing cost, already mature technology for 77 GHz, 2 boards (1 for
radar transciever and 1 for radar baseband processing)
W.r.t CMOS SiGe today offers higher fmax, up to 200-300 GHz (at least20% reduction is expected at extreme temperature), higher output
power (Psat of 15-16 dBm available) and is mature for mass production
CMOS transceivers in 90 nm and 65 nm for 77 GHz already published,
some improvements needed for automotive mass production but has
higher integrating potential (transceivers and baseband DSP)
Today SiGe-based RADAR, tomorrow CMOS-based expected given
technology evolution and trend towards more digital RADAR
Automotive RADAR with SiGe mm-Wave T/R
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Commercially available from Bosch
based on SiGe Infineon Chipset
2 PCB boards
FCMW modulation
LRR 7dBm Pout, 4 channels (2 TX/RX,
2 RX only), dielectric lens antenna
provides high gain for Rmax 250m
Alternative versions with PCB or on-
chip Integrated antennas
B. Fleming, IEEE Vehicular Tech. Mag. 2012
Block diagrams of automotive RADAR withSiGe mm-Wave T/R
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SiGe mm Wave T/R
(J. Hasch et al., IEEETran. Micr Theory Tech, 2012)
Performance of transceivers in CMOStechnology
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JSSC2010 JSSC2010 IEEEAESM 2012
Technology65 nm
CMOS
90nm
CMOS
guidelines
Power
consumption243 mW 517 mw N/A
Area 1 mm2 6.8 mm2 N/A
Carrier frequency 77 GHz 77 GHz 77 GHz
Resolution N/A 100m with off-chip 24
dB antenna,
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J. Hasch et al., Millimeter-Wave Technology for Automotive Radar Sensors in the 77 GHz
Frequency Band, IEEE Tran. Micr Theory and Tech, 2012T. Mitomo et al., A 77 GHz 90 nm CMOS transceiver for FMCW radar applications, IEEE J. Solid-State Circuits 2010
Y. Kawano et al., A 77 GHz transceiver in 90 nm CMOS,IEEE ISSCC 2009
Y.-A. Li et al., A fully integrated 77 GHz FMCW radar transciever in 65 nm CMOS, technology,IEEE J. Solid-State Circuits 2010
R. Stevenson, A driverssixth sense, IEEE Spectrum 2011S. Trotta et al., An RCP Packaged Transceiver Chipset fo Automotive LRR and SRR Systems inSiGe BiCMOS Technology, IEEE Tran. Micr- theory and tech, 2012
B. Fleming, Recent Advancement in Automotive Radar Systems, IEEE Vehicular Tech. Mag. 2012
W. Menxel et al., Antenna Concepts for Millimeter-Wave Automotive Radar Sensors,Proceedings of the IEEE, 2012
V. Giammello et al., ATransformer-Coupling Current-Reuse SiGe HBT Power Amplifier for 77-GHz Automotive Radar,accepted on IEEE Tran. Micr Theory and Tech
B. Neri, S. Saponara, Advances in Technologies, Architectures and Applications of Highly-Integrated Low-power Radars, IEEE Aerosp. Eelectr. Syst. Mag. 2012
Outline of the tutorial
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Scenarios and applications for highly-integrated
low-power RADARRADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADC
Ubiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADAR
HW-SW implementing platforms for RADAR
digital signal processing
Conclusions
Main signal processing functions in
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classical RADARs:
Digital range compression
Single and multi beamforming
Space-time adaptive processing
CFAR techniques
Direction of arrival (DOA) estimation
Tracking
Digital pulse compression
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Frequency of phase modulated long signals are transmitted and
compressed in reception for improving range resolution.
The receiver is a matched filter/correlator. The correlation can be done intime or frequency domain. The most common is the frequency domainthrough FFT. Many pulses are then integrated for target detection.
Digital pulse compression
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The FFT/IFFT is the core of the digital pulse compression
8-point, Radix-2 FFT
Digital pulse compression
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Single and multi beamforming
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To form a beam in a particular direction, each element of the array needs
to be followed by a time delay such that when all the outputs are summedthey add up coherently to form a beam
Analog beamforming Digital beamforming
Figures from Skolnik book
Single and multi beamforming
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Analog beamforming used to implement subarrays, followed by digitalreceivers and digital phase shifter. In digital domain, the beamfomers areFIR filters with complex weigths
Analog/digital beamforming
Figure from Skolnik book
Space-Time Adaptive Processing
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STAP is an advanced signal processing technique used in airborne radarapplications to suppress interferences by performing jointly data-adaptivebeamforming (space domain) and Doppler processing (time domain)
Space-Time Adaptive Processing
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STAP: data cube
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Optimum STAP
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Optimum STAP
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The core of the STAP is the inversion of the disturbance covariance matrix,adaptively estimated both in time and space domains using secondaryvectors.Direct computation of the weight vector wby inverting is not practicalfor STAP due to the huge dimension of itself. Generally the STAP systemtry to solve the equivalent linear system
through the QR decomposition after covariance matrix estimation.The number of RFLOPs with QR decomposition is of order of (NM)3.QR decomposition can be applied directly to secondary vectors avoiding
the matrix estimation. With Lsecondary vectors the number of RFLOPs is
kRw v
2 3
8 2.67L MN MN
R
R
Reduced dimension STAP
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Incoherent CFAR detector
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(only amplitude information is used)
Incoherent CFAR detectors
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CA-CFAR : Z=mean(X1, X2,. XN)
GO-CFAR: Z1=mean(X1, X2,. XN/2)
Z2=mean(XN/2+1, XN/2+2,. XN)
Z=max(Z1,Z2)
SO-CFAR: Z1=mean(X1, X2,. XN/2)
Z2=mean(XN/2+1, XN/2+2,. XN)
Z=min(Z1,Z2)
OS-CFAR: Y=sort(X1, X2,. XN)Z=YK
Depending on the adaptive thresholdZwe have different CFAR techniques
Coherent adaptive CFAR detectors(b h I d Q d)
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(both I and Q components are used)
For Gaussian target in Gaussian clutter we have:
1
0
1
0
1
0
21
1
21
1
1
2
11
1
>( ) : ( ) : ( ) ( ) : 1
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It needs two beams for each angular coordinate
Sum and difference patterns are used
It can use single or multiple pulses
H. Rohling, Automotive Radar tutorial, 2008
DOA estimation - Monopulse
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-1
-0.5
0
0.5
1
-8 -6 -4 -2 0 2 4 6 8
azimuth (degrees)
N
ormalizedantennapatte
rn
Ideally, without noise
Example, with Gaussianantenna pattern and-3dB beamwidth=3o
Tracking - Linear Kalman filter
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1
* *
k k kK P P R
Object parametersSensor
Measurement LinearKalman
Filter
Track estimate
Prediction
xk
yk
k
xk
yk
t
t
v
v
y
*
*
*
*
xk
ykk
xk
yk
t
tv
v
y
xk
yk
k
xk
yk
t
t
v
v
y
xk
yk
kxk
yk
t
t
v
v
y
1
1
1
1
1 0 0
0 1 0
0 0 1 0
0 0 0 1
k k
k k
k k
k k
x x
y y
x x
y y
t tT
t tT
v v
v v
Linear model1k ky Ay
H. Rohling, Automotive Radar tutorial, 2008
Linear Kalman filter
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Prediction step:
- Prediction estimation based on Process matrix A:
- Prediction accuracy estimation based on tracking accuracy and process noise:
*
1
k ky Ay
*
1
T
k k P AP A Q
Track estimation step
- Track estimation:
- Tracking accuracy estimation:
1
* *
k k kK P P R
* * k k k k k y y K y y
*k k kP I K P
Kalman gain based prediction
accuracy and measurement noise
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Some
applications
Automotive RADARs
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Functionalities:Autonomous cruise control (ACC)
ACC support with Stop&Go functionality
Pre-crash sensing
Collision mitigation and avoidance
Parking aid (forward and reverse)
Lane change assistant
Rear crash collision warning
Goals:Simultaneous measurement of obstacle range,
radial velocity and angle
Long Range Radar (LRR)
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Requirements for LRR RADAR
Functionalities: Autonomous Cruise Control (ACC)Collision warning
Observation area
LRR for vehicular applications
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Transmitted signals
Some special waveforms must be used to fulfill the requirements of
simultaneous range and radial velocity measurement:
Pulse Doppler
FMCW with (at least) up- and down-chirp signals
Frequency Shift Keying (FSK) CW
MFSK CW
LRR for vehicular applications
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Parameters for an LRR radars24 GHz or 77 GHz
Single channel scheme2
( ) cos 22
swT T
CPI
B ts t f t
T
( )R Ts t s t t
,1
22 swB D r
CPI
Bf f f v R
cT
,2
22sw
B D r
CPI
Bf f f v R
cT
H. Rohling, Automotive Radar tutorial, 2008
LRR for vehicular applications
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FFT: applied on each segment (up and down chirp)
frequency and range estimation accuracy depends on the number of FFT
points. Typical values: 128-4096 points
up chirp down chirp
,1Bf ,2BfH. Rohling, Automotive Radar tutorial, 2008
LRR for vehicular applications
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With only one up and down chirp , two targets are ambiguous. With
four chirps two targets can be easily resolved
H. Rohling, Automotive Radar tutorial, 2008
LRR for vehicular applications
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Signal processing
CFAR techniques for detection
Most common: 1D-CA-CFAR applied onFFT output (frequency domain)
Tracking techniques after detection
Most common: linear KF
DOA estimation
Most common: Monopulsewith two antennas
UWB radarsChacteristics:
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Low power consumption
Low cost circuitry
Low probability of detection
Different materials and environments distort pulses differently
Chacteristics:
Vehicular radar (Short range)
Ground Penetrating Radar (GPR)
Trough-the-wall imaging
Medical radars
Applications:
UWB RADAR definitionThe amount of spectrum occupied by a signal transmitted by a UWB-radar (i e
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The amount of spectrum occupied by a signal transmitted by a UWB radar (i.e.the bandwidth of the UWB signal) is at least 25% of the center frequency. Thus, aUWB signal centered at 2 GHz would have a minimum bandwidth of 500 MHzand the minimum bandwidth of a UWB signal centered at 4 GHz would be1 GHz. Often the absolute bandwidth is bigger than 1 GHz.
narrowband
UWBnoise
UWB RADAR for medical applications
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DS
P
static signal cancellation
FFT and frequency estimation
How does it work?
D
S
P
UWB RADAR for medical applications
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UWB RADAR for medical applications
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Frequency band: 3.1 -10.6 GHz, typical bandwidth: 2 GHz
UWB RADAR for medical applications
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Chest movements for breathing and heart beat: the time delay of thereference signal in the correlator is fixed to the position of the target, thenany movement will change the output amplitude at the receiver.
The relationship between the target distance and the output amplitude isalmost linear around the correlation maximum, then a distance change canbe directly seen through the amplitude of the output signal
Measured sensor output for abreathing person and a breath hold ofabout 12 sTransmitted pulse: 1stderivative
Gaussian pulseDistance fixed to the skin-air boundary
Heart beat
UWB RADAR for medical applications
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static signal cancellation Xs
=mean(X)
Y=X-Xs
FFT and frequency estimation
Undesired harmonic terms andintermodulations other than thesinusoids of interestThe third and forth- order harmonics
of respiration signal are very close tothe frequency of heart beat,complicating the output spectrumNeed for frequency super-resolutionmethods (like RELAX or MUSIC)
UWB RADAR for medical applications
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Predicted attenuation of pulse-echo traveling from the transmitting antennato the receiving antenna. Each step accounts for echo at the boundary.
Decreasing of the curve accounts for linear attenuation in the tissue
RCS of the heart @5GHz: 0.001 m2
Doppler Bio RADAR
How does it work?
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The transmitter generates a CW signalThe phase shift of the reflected signal is proportional to the time-varyingchest positionSpectral analysis through FFT or super-resolution method estimate beat andbreath frequencies
C. Li et al., IEEE TIM 2010
How does it work?
Conclusions
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Automotive applications: in the future a network of small
radars will be used to improve the performance in terms of
angular, frequency and range accuracy and in terms of
number of tracked targets
Biomedical applications: use of MIMO radars techniquesto mitigate the noise caused by other body motion artifacts
References
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M. A. Richards, Fundamentalsof Radar Signal Processing,McGraw-Hill, 2005, ISBN 0-07-144474-2.
S. Lal, R. Muscedere, S. Chowdhury, An FPGA-Based Signal Processing System for a 77 GHz MEMS Tri-ModeAutomotive Radar,2011 22nd IEEE International Symposium on Rapid System Prototyping, 2011 , pp. 2 - 8.
S. Venkatesh, C.R. Anderson, N.V. Rivera, R.M. Buehrer, "Implementation and analysis of respiration-rate estimationusing impulse-based UWB", IEEE MILCOM 2005, 2005, pp. 3314-3320, Vol. 5
M. Leib, W. Menzel, B. Schleicher, H. Schumacher, " Vital signs monitoring with a UWB radar based on a correlationreceiver", Fourth European Conference on Antennas and Propagation (EuCAP),2010, pp. 1 - 5
H. Dominik "Short Range Radar - Status of UWB Sensors and their Applications", 4thEuropean Radar Conference,2007, pp. 251-254.
J. J. Alter, J.O. Coleman, RadarDigital Signal Processing", Ch. 25 in Introduction to Radar Systems, ed M. Skolnik,McGraw Hill.
R.H. Hosking, "FPGA Cores Enhance Radar Pulse Compression", COTS Journal, October 2003, pp. 32-35.
H. Rohling, "Radar Sensors for Automotive Applications", tutorial2008 IEEE Radar Conference, Rome
R. Klemm, J. Ward, "Space-Time Adaptive Processing Architectures and Algorithms", tutorial 2008 IEEE RadarConference, Rome
Outline of the tutorial
Scenarios and applications for highly integrated
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Scenarios and applications for highly-integrated
low-power RADARRADAR architecture and analog-digital
partitioning
RF/mm-Wave RADAR transceivers and ADC
Ubiquitous low-power RADAR case studies:
vital sign detection, automotive driver assistance
Digital signal processing for RADAR
HW-SW implementing platforms for RADARdigital signal processing
Conclusions
HW-SW implementing platforms forRADAR digital signal processing
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Overview of implementing platforms for RADARDSP
Custom SoC
MCU (Microcontroller Unit)
GPP (General Purpose Processor)
DSP (Digital Signal Processor) and GPU
(Graphical Processing Unit)
High-end FPGA (Field Programmable Gate Array)
Cost-effective FPGA
Implementing platforms for RADAR DSP
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Ubiquitous integrated RADAR applications (automotive, bio,..) needs low-
power consumption (reduced power supply and thermal issues andincreased portability) but can require high computational capabilities and
large data transfer rate and memory storage size
Energy-flexibility trade-off to be found betweenSoftware-oriented platforms (GPP, DSP, GPU, Microcontroller)
and Hardware-oriented platforms (custom IC-SoC or MPSoC, FPGA)
Note: apart Custom SoC designs or microcontrollers, external ADC and
DAC are required since only digital interfaces are provided
Implementing platforms for RADAR DSP
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Main performance metrics to be considered:
- Computational capabilities: GOPS (giga operations pre second) and if
there are DSP-dedicated instructions (e.g. Multiply, MAC, )
- Operand bit-width and arithmetic type (Fixed, Floating or Block Floating
Point Operations)
- Memory: access frequency, size and hierarchy levels
- Flexibility: level of re-programmability or re-configurability
- Energy efficiency (GOPS/MHz)
- On-chip available I/O interfaces (type, data-r