WE3.L09 - POLARIMETRIC SAR IMAGE VISUALIZATION AND INTERPRETATION WITH COVARIANCE MATRIX INVARIANTS
WE3.L10.2: COMMUNICATION CODING OF PULSED RADAR SYSTEMS
description
Transcript of 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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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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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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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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Institut für Hochfrequenztechnikund Elektronik IHE
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
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
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