design of an airborne multi-input multi-output radar emulator testbed for ground moving target ...

73 Pages·2012·1.62 MB·English

DESIGN OF AN AIRBORNE MULTI-INPUT
MULTI-OUTPUT RADAR EMULATOR TESTBED FOR
GROUND MOVING TARGET IDENTIFICATION
APPLICATIONS
THESIS
Presented in Partial Fulfillment of the Requirements for the Degree Master of
Science in the Graduate School of the Ohio State University
By
Evgeny Yankevich, BS
Graduate Program in Electrical and Computer Science
The Ohio State University
2012
Master’s Examination Committee:
Prof. Emre Ertin, Advisor
Prof. Lee Potter
(cid:13)c Copyright by
Evgeny Yankevich
2012
ABSTRACT
Multi input multi output (MIMO) radar is a radar system with multiple receive
and transmit antennas, that can transmit independent waveforms on each transmit
elements. Although many traditional multi-antenna radar concepts such as phased-
array, receive beamforming, synthetic aperture radar (SAR), polarimetry, and inter-
ferometry can be seen as special cases of MIMO radar, the distinct advantage of a
multi-antenna radar system with independent transmit waveforms is the increased
number of degrees of freedom leading to improved resolution and performance in
detection and parameter estimation tasks.
A promising application of MIMO radar is the identification of slowly moving
targets using airborne MIMO radar platforms. The advantage of using MIMO in this
configuration is its ability to synthesize a larger virtual array with relatively fewer
antennas. This allows higher spatial resolution and better separation of returns from
ground clutter and targets. The space-time adaptive processing (STAP) methods
originally developed for Single-input, Multiple-output (SIMO) radar are applicable
to MIMO radar systems after proper pre-processing of the received signals. The
performance of STAP algorithm critically hinges on the structure of the clutter co-
variancematrix; therefore, MIMOSTAPmethodswillbenefitgreatlyfromtheoretical
and empirical study of the clutter statistics.
The contribution of this work can be summarized in three parts. First, we present
ii
a design of a rooftop MIMO radar testbed that emulates a MIMO GMTI system
mounted on airborne platform. Second, we give results of a simulation study of
ground clutter for the testbed rooftop geometry, highlighting potential issues with the
relatively close range. Third, we extend previous results on clutter covariance matrix
rank for MIMO systems with orthogonal waveforms to the case of MIMO systems
employingnonorthogonalwaveforms. Relationshipbetweenrankofcovariancematrix
of orthogonal and nonorthogonal waveforms was established.
iii
To my family: my wife Uliana and sons Tamir and Tal;
and my parents who supported and motivated me so much during this time.
iv
ACKNOWLEDGMENTS
IwouldlikeexpressmygratitudetomyadvisorProf. EmreErtinforhissupportive
position and help during entire program period. He open the world of radars for me
and taught the proper way and methodology of conducting research. I appreciate his
way of intuitive and formal explanations of very complicated issues in radar signal
processing and system design.
I would like to thank Siddharth Baskar for his help in implementation of the MIMO
GMTI emulator design.
v
VITA
1968 .................................. Born in Tashkent, Uzbekistan
1991 .................................. BSinElectricalEngineeringfromMoscow
InstituteofElectronicTechnologies(MIET)
1993-2008 ............................. Research Engineer at Qualcomm Israel,
Infineon Technologies, Zoran Microelec-
tronics.
2010-2012 ............................. Graduate Research Assistant and Fellow
in the Department of Electrical and Com-
puterEngineeringatTheOhioStateUni-
versity
FIELDS OF STUDY
Major Field: Electrical and Computer Engineering
Specialization: Signal Processing and Communication
vi
TABLE OF CONTENTS
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Vita . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
CHAPTER PAGE
1 MIMO Radar Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Notations and Glossary . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Review of GMTI and STAP Processing . . . . . . . . . . . . . . . . . . 8
2.1 Doppler Phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Processing for Ground Moving Target Indication . . . . . . . . . . 12
3 MIMO Model for GMTI . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1 Orthogonal Waveforms Case . . . . . . . . . . . . . . . . . . . . . 19
3.1.1 Virtual Array Concept . . . . . . . . . . . . . . . . . . . . 20
3.1.2 Uniform Linear Array . . . . . . . . . . . . . . . . . . . . . 22
3.2 Nonorthogonal Waveforms Case . . . . . . . . . . . . . . . . . . . 25
3.3 Rank of Clutter Covariance Matrix . . . . . . . . . . . . . . . . . . 27
3.3.1 Orthogonal waveforms case . . . . . . . . . . . . . . . . . . 28
3.3.2 Nonorthogonal waveforms case . . . . . . . . . . . . . . . . 31
4 MIMO GMTI: TestBed Description . . . . . . . . . . . . . . . . . . . . 33
4.1 Reliable Detection Range . . . . . . . . . . . . . . . . . . . . . . . 34
4.2 Antenna Array Requirements . . . . . . . . . . . . . . . . . . . . . 36
4.3 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.4 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.4.1 Noise Figure . . . . . . . . . . . . . . . . . . . . . . . . . . 42
vii
4.4.2 Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.4.3 VGA gain and Tx / Rx isolation . . . . . . . . . . . . . . 44
4.4.4 RF switches . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.4.5 BPF bandwidth and aliasing . . . . . . . . . . . . . . . . . 45
4.4.6 Local oscillator synchronization and the digitizer reference
clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.5 Micro Controller Board . . . . . . . . . . . . . . . . . . . . . . . . 47
5 MIMO GMTI: Matlab Simulation . . . . . . . . . . . . . . . . . . . . . 49
6 Further Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
CHAPTER PAGE
A Matched Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
B Receiver Link Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
C Amplifier Nonlinearity . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
C.1 1-dB Compression Point . . . . . . . . . . . . . . . . . . . . . . . . 61
C.2 IP3 Intermodulation Point . . . . . . . . . . . . . . . . . . . . . . 61
viii
LIST OF FIGURES
FIGURE PAGE
2.1 Doppler for moving platform . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Data cube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 Clutter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Side-looking radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.2 Virtual antenna rray due to spatial convolution . . . . . . . . . . . . 21
3.3 Equivalent SIMO array with one Tx and NM Rx antennas . . . . . . 22
3.4 Relative speed of the radar platform and a target . . . . . . . . . . . 23
3.5 Plane wave striking antenna array . . . . . . . . . . . . . . . . . . . 24
4.1 Block Diagram of the Emulator . . . . . . . . . . . . . . . . . . . . . 34
4.2 Tx and Rx antenna arrays . . . . . . . . . . . . . . . . . . . . . . . . 35
4.3 SNR calcution. Ouptut power 30 dBm (1W), signal bandwifth 125
MHz; Integration time 1, 64 pulses . . . . . . . . . . . . . . . . . . . 37
4.4 Transmitter Block Diagram. One channel. . . . . . . . . . . . . . . . 40
4.5 Receiver Block Diagram. One channel. . . . . . . . . . . . . . . . . . 41
4.6 Noise figure with low isolation . . . . . . . . . . . . . . . . . . . . . . 42
4.7 Noise figure with high isolation . . . . . . . . . . . . . . . . . . . . . 43
4.8 Saturation Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.9 BPF as antialising filter . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.10 BPF as antialising filter . . . . . . . . . . . . . . . . . . . . . . . . . 46
ix