WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS

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Universität Karlsruhe (TH) Research University•founded 1825 in der Helmholtz - Gemeinschaft Forschungszentrum Karlsruhe “RadCom” The Intelligent Radar Signal Communication Coding of Pulsed Radar Systems “RadCom” The Intelligent Radar Signal Communication Coding of Pulsed Radar Systems by Werner Wiesbeck by Werner Wiesbeck

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Transcript of WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS

Page 1: WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS

Universität Karlsruhe (TH) Research University•founded 1825in der Helmholtz - Gemeinschaft

Forschungszentrum Karlsruhe

“RadCom”The Intelligent Radar Signal

Communication Coding ofPulsed Radar Systems

“RadCom”The Intelligent Radar Signal

Communication Coding ofPulsed Radar Systems

by Werner Wiesbeckby Werner Wiesbeck

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Institut für Hochfrequenztechnikund Elektronik IHE

State of the Art Coherent Pulsed Radar Modulation

State of the Art Radars areStupid!

State of the Art Radars areStupid!

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Institut für Hochfrequenztechnikund Elektronik IHE

State of the Art Coherent Pulsed Radar ModulationRadar type Time domain Frequency domain

Pulsed-CWt

A Tτp

f

A

FM-Chirpt

A

t

fTx

t

fTx

Frequency Codedf

A

Stagger ...

t

A

f

A

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Institut für Hochfrequenztechnikund Elektronik IHE

Motivation – Basic Idea

RadCom

Radar targetsCommunication

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Institut für Hochfrequenztechnikund Elektronik IHE

Basic Idea

•range•speed

•azimuth

by digital beam-forming

2D Radar Imaging

Intelligent Transportation

System (ITS)

Driver AssistanceCongestion AvoidanceDynamic Route PlanningPreCrash Detection

communication

interferer

Car equipped withRadCom system

RadCom Txsignal

targets

reflected signal

Interferencesignal

Communications

Diversity, MIMO

•traffic information•road condition

•C2C communication

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Radar and Communication Ranges

Radar equation:

!

PRxRadar =PTx " GTx " GRx R " #

2 " $(4% )3 " R4

Com. range:

!

PRxCom =PTx " GTx " GRx C " #

2

(4$ )2 " R2

!

PRxCom = PRxRadar "4#" R2

$

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Institut für Hochfrequenztechnikund Elektronik IHE

Coding of Radar Signals

Well known Radar coding for EW purposes:Pulse RadarLinear FM ChirpFMCWM-SequenceMulticarrier Signals......

Coding in communications:Single carrier BPSK, QPSKOFDMCDMADSSS......

Example:

OFDM

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OFDM Signal Spectrum

OFDM pulse shape:

rectangular(-13dB first ordersidelobes for singlesub-carrier)

N sub-carriers,

e.g. 16

complex orthog.sampling in FD

OFDM spectrum

sub-carrier

rel.

pow

er s

pect

ral d

ensi

ty in

dB

0

-10

-20

-30

-10

0 0.5 1-0.5-1normalized frequency

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Institut für Hochfrequenztechnikund Elektronik IHE

OFDM Transmit Signal

t

f

x(t,f)

Δf

B

....

......

TOFDM

symbo

ls

µ=0

Nsym-1

....

....carriern=

0

Nc-

1

envelopes

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OFDM Multi Carrier Transmit Scheme

Orthogonal(FDM) scheme as a digital multi-carrier method

Dividing datainto parallel data

streams

Each sub-carrier ismodulated at a low

symbol rate

Total data rates similar tosingle-carrier schemes

1:N IFFT N:1 signalformation

cyclic prefixpilots

guards

Nsymbolsstream

OFDMsymbols

Frequency Domain Time Domain

datasource

QAMmodulator

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Joint Radar and Communication System Concept

Advantages of OFDM signals:high data rate for payload data (no spreading required)high processing gainlow range side lobespossibility of Doppler processing (orthogonal to range)Beam-forming capability

communicationpartner

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OFDM System Parameters for 24 GHz ISM Band

Symbols Parameter Value fc Carrier frequency 24 GHz

Nc Number of subcarriers 1024

f Subcarrier spacing 90.909 kHz

TOFDM Elementary OFDM symbol duration 11 µs

TG Cyclic prefix length 1.375 µs

B Total signal bandwidth 93.1 MHz

R Radar range resolution 1.61 m

Rmax Unambiguous range 1650 m

vrel,max Unambiguous velocity ± 284 m/s

Nsym Number of evaluated symbols 256

∆vrel Velocity resolution 2.22 m/s

GP Processing Gain 54.2 dB

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OFDM Coded Radar System Simulation

OFDM-RxRadarprocessing

Binary dataRadar image

OFDM-Tx channel

Targets: {X,Y}, v, RCSPropagation: ray-tracing

Signal: OFDM coded BPSK

Tx: G, PTx, Nsym

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OFDM Radar Processing

Standard approach:Cross-correlation Tx-Rx Signals

!

src (" ) = y(t)x(t # ")$ dt

dependent on signal (data) unpredictable correlations high computational effort

New, dedicated approach:Complex division of symbols

!

Idiv (n) =IRx (n)ITx (n)

, src (") = IFFT Idiv (n)[ ]

completely independentfrom signal (data)

low computational effort

!

x(t)

!

y(t)!

ITx (n)

!

IRx (n)

!

fc~

Tx

Rx

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OFDM-Radar Range-Doppler Processing

1. Step: complex division of symbols )(

)()(nInI

nITx

Rxdiv =

3. Step: Inverse Fourier trans-formation in frequency direction

k=0k=1

k=N-1.

ν=0 ν=M-1. . .

Doppler

dist

ance

2. Step: Fourier transformation in time direction

n=0n=1

n=N-1.

ν=0 ν=M-1. . .

Doppler

frequ

ency

µ=M-1n=0n=1

n=N-1.

µ=0 . . .

time

frequ

ency .............

.............

FFT .............

.............

......

......

.

......

......

.IFFT

Processing gain: Nc·Nsym

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Range and Doppler Resolution for 3 Targets

Dis

tanc

e R

in m

Relative velocity v in m/s

Unambiguous andindependentresolution for

distance and Dopplerfor an arbitrary

number of objects

Target Range R in m Speed v in m/sz1 33,2 10z2 33,2 14z3 35 10

B = 93.1 MHzTsym = 12.375 µsNsym = 128fc = 24 GHz

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Universität Karlsruhe (TH) Research University•founded 1825in der Helmholtz - Gemeinschaft

Forschungszentrum Karlsruhe

“RadCom”Verification by Measurements

“RadCom”Verification by Measurements

by Christian Sturm and Werner by Christian Sturm and Werner WiesbeckWiesbeck

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OFDMSignal

Ethernet HUB

Measurement System Setup at 24 GHz ISM Band

(((

(((

GRx = 22 dBi

GTx = 22 dBiPTx = 22 dBm

cable losses ≈ 3.5 dB

frequency

Mixer creates two sidebands

Only upper sideband isevaluated at the receiver

Reference+ Trigger

Mixer SMR40@ 23.85 GHz

FSQ26@ 24.05 GHz

SMJ 100A@ 200 MHz

amp

A(f)

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Measurement on Street

Radar image in dB

8.1 dBm²v = -14.2 km/h

13.3 dBm²

Velocity ≈ 15.7 m/s = 56.7 km/h

Normalization to RCS = 1 m² in 10 m distance

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Universität Karlsruhe (TH) Research University•founded 1825in der Helmholtz - Gemeinschaft

Forschungszentrum Karlsruhe

Digital Beam-formingfor

Azimuth Processing

Digital Beam-formingfor

Azimuth Processing

by Christian Sturm and Werner Wiesbeckby Christian Sturm and Werner Wiesbeck

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Multi-beam DBF Radar Signal Processing

!

src,1(")src,2(")src,3(")src,4 (")

#

$

% % % %

&

'

( ( ( (

=! s rc (")

Receive array signal vector

Azimuth Processing byDigital Beamforming

KKF

Sendesignal x(t)

Rx signal y1(t)

KKF

Sendesignal x(t)

Rx signal y2(t)

KKF

Sendesignal x(t)

Rx signal y3(t)

Corr

Tx signal x(t)

Rx signal y4(t)

!

d/λ d/ λ d/λ

234 1τ

!

src,4 (")

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Digital Beam-Forming for Multiple Targets

transmit beam

DBF processed multiple receive beams

⇔multiple receive beamscoverage Tx = coverage RxCoverage unprocessed:

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Radar und Communication with Digital Beam-forming

Multiple antenna systems and coded signals for Super Resolution?

V2V communication by codes

range compression by correlation (PN-Codes, PPM, OFDM, MPSK...)

angular compression by Digital Beam-forming or by

Super-Resolution?

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Music Processing in OFDM Radar

{X,Y}V

RCSAWGN

OFDM-RxChannel

RadarPerformance

Binary DATATGPow N_sym OFDM-Tx

Image Data

.... sn

ap sh

ots ....

time

!

! s c1(n,m)

MUSIC

azim

uth

proc

essi

ng

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Virtual Drive with Ray-Tracing DBF and Super Resolution

Ray-Tracing KanalmodellRadar Transmitter

Ray-tracing(BPSK Modulation)

AzimuthArray Processing

RangeCorrelation

DBF with Super Resolution

Radar Receiver

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Summary Virtual Drive

RadCom

Radio detectionand ranging

Mobile Communications

one transmissionone spectrumone code