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]


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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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low-power RADAR


partitioning





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


7/1862012 IEEE Radar Conference, May 7-11, Atlanta

Electronics evolution

Not only nanoscale CMOS but also System-in-Packageintegration of passives, RF & mm-Wave, high voltage,

sensors/actuators (MEMS) ..



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



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



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)



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

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GGPP rttr



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



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



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





low-power RADAR


partitioning





Conclusions



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



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)



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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low-power RADAR


partitioning



Digital signal processing for RADAR

HW-SW implementing platforms for RADAR


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)


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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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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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



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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



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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



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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



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low-power RADARRADAR architecture and analog-digital

partitioning






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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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


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


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



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partitioning

RF/mm-Wave RADAR transceivers and ADC

Ubiquitous low-power RADAR case studies:





Conclusions

Main signal processing functions in


117/186


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.



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The FFT/IFFT is the core of the digital pulse compression

8-point, Radix-2 FFT



120/186




121/186


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



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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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2012 IEEE Radar Conference, May 7-11, AtlantaR. Klemm, J. Ward, STAP tutorial, 2008

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


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



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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




141/186


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



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With only one up and down chirp , two targets are ambiguous. With

four chirps two targets can be easily resolved




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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:


144/186


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



147/186




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Frequency band: 3.1 -10.6 GHz, typical bandwidth: 2 GHz



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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



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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)



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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


Scenarios and applications for highly integrated


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partitioning

RF/mm-Wave RADAR transceivers and ADC

Ubiquitous low-power RADAR case studies:



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

Tutorial Saponara Greco V6 17Aprile

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