SAL, Dept. of ECE 1 MIMO Radar -- Diversity Means Superiority Jian Li Department of Electrical and Computer Engineering University of Florida Gainesville, Florida, USA Petre Stoica Department of Information Technology, Uppsala University, Uppsala, Sweden Collaborators: William Roberts, Yao Xie, Luzhou Xu
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SAL, Dept. of ECE 1
MIMO Radar-- Diversity Means Superiority
Jian Li
Department of Electrical and Computer Engineering University of Florida
Gainesville, Florida, USA
Petre Stoica
Department of Information Technology,
Uppsala University,Uppsala, Sweden
Collaborators: William Roberts, Yao Xie, Luzhou Xu
•M=10, ULA, Half-wavelength spacing•Equal Elemental Power, Total Power = 1•Targets at -40, 0, 40 degrees; Jammer at 25 degrees
SAL, Dept. of ECE 23
Example 3: Resolution
Targets now at -40, 0, 3 degrees Omnidirectional Beampattern Matching
Capon
GLRT
-80 -60 -40 -20 0 20 40 60 800
0.5
1
1.5
Cap
on S
pect
rum
Angle (degree) -80 -60 -40 -20 0 20 40 60 800
0.5
1
1.5
Cap
on S
pect
rum
Angle (degree)
-80 -60 -40 -20 0 20 40 60 800
0.5
1
1.5
GLR
T
Angle (degree)-80 -60 -40 -20 0 20 40 60 80
0
0.5
1
1.5
GLR
TAngle (degree)
SAL, Dept. of ECE 24
Beampattern MatchingMIMO vs. Phased-Array
Phased-Array counterpart no longer convex optimization problemMIMO design is Semi-Definite Relaxation (SDR) of Phased-Array design
Can be used as initial condition of Newton-type search).
Phased-arrayDOF = 9
MIMO DOF = 90
−50 0 500
0.5
1
1.5
2
2.5
3
Angle (degree)
Bea
mp
atte
rn
−50 0 500
0.5
1
1.5
2
2.5
3
Angle (degree)B
eam
pat
tern
•M=10•Equal Elemental Power•Total Power = 1•ULA•Half-wavelength spacing
SAL, Dept. of ECE 25
Minimum Sidelobe BeampatternDesign
Design GoalMinimize peak sidelobe levelAchieve prescribed 3 dB main-
beam widthSubject to either total power or (equal) elemental power constraint
Can be formulated as Semi-Definite Program (SDP)
MIMO Design is SDR of Phased-Array Design
MIMO design is used as initial condition for Newton-type search to obtain phased-array design
SAL, Dept. of ECE 26
Minimum Sidelobe Design Example
M=10 (uniform elemental power constraint, 0.1 per element)Mainbeam pointing at3 dB Mainbeam width = 20 degreesSidelobe regionULA, Half-wavelength spacing
0 0θ =
MIMO Phased-array
−50 0 50−30
−20
−10
0
10
20
Angle (degree)
Bea
mp
atte
rn (
dB
)
−50 0 50−30
−20
−10
0
10
20
Angle (degree)
Bea
mp
atte
rn (
dB
)
90 , 20 20 ,90⎡ ⎤ ⎡ ⎤− − ∪⎣ ⎦ ⎣ ⎦
SAL, Dept. of ECE 27
Minimum Sidelobe Design Example
Relaxed Elemental Power ConstraintWithin 20% of 0.1 for each elemental powerTotal transmitted power = 1
−50 0 50−30
−20
−10
0
10
20
Angle (degree)
Bea
mp
atte
rn (
dB
)
−50 0 50−30
−20
−10
0
10
20
Angle (degree)B
eam
pat
tern
(d
B)
MIMO Phased-array
SAL, Dept. of ECE 28
Applications
Directed Energy System for Homeland Defense
All antennas transmit at their maximum powerLarge apertureSufficient mainbeamwidth since target is movingNo impact on friendly targets
SAL, Dept. of ECE 29
Thermal Therapy
Thermal Therapy System in Medicine
Ultrasound has good penetrationAll transducers transmit at a low power to avoid harming healthy tissueLarge aperture needed to deliver sufficient energySufficient mainbeam width needed
SAL, Dept. of ECE 30
Drowning in Sound
“It’s clear that the ocean is under siege from a lot of different sources.”
[1] Jean Kumagai, “Drowning in Sound,” IEEE Spectrum, April 2006.
Whale stranded during a military sonar exercise near Canary Islands in July 2004 [1]
SAL, Dept. of ECE 31
Reduce Ocean Noise
Distributed Sensor Network?Large Aperture to Deliver Sufficient Energy At Focal PointLow Power Transmitted by Each SensorWaveform Diversity to Achieve Desired Mainbeam Width
Currently, 220 dB pulses generated by active sonar and air-gun arrays [1]