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Antenna Array Signal Processing for Multistatic Radar Systems

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Antenna Array Signal Processing for Multistatic Radar Systems i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page i | #1 i i i Antenna Array Signal Processing for Multistatic Radar Systems i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page ii | #2 i i i i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page iii | #3 i i i Antenna Array Signal Processing for Multistatic Radar Systems Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof.dr.ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op vrijdag 12 juli 2013 om 10:00 uur door Francesco BELFIORI Laurea Specialistica in Ingegneria delle Telecomunicazioni Universit`adegli studi di Roma \La Sapienza" geboren te Roma, Itali¨e i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page iv | #4 i i i Dit proefschrift is goedgekeurd door de promotor: Prof.ir. P. Hoogeboom Samenstelling promotiecomissie: Rector Magnificus, voorzitter Prof. ir. P. Hoogeboom, Technische Universiteit Delft, promotor Prof. Dr. L. Ferro-Famil, Universit´ede Rennes 1 Prof. Dr. A. Yarovoy, Technische Universiteit Delft Prof. Dr.-Ing. J. Ender, Universit¨atSiegen - Fraunhofer FHR Prof. Dr. F. Le Chevalier, Technische Universiteit Delft - Thales Dr. W. van Rossum, TNO This research was supported by TNO under contract DenV-017. ISBN 978-94-6191-782-9 Antenna Array Signal Processing for Multistatic Radar Systems. Dissertation at Delft University of Technology. Copyright c 2013 by Francesco Belfiori. All rights reserved. No parts of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the author. Author e-mail: [email protected] i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page v | #5 i i i A mia madre i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page vi | #6 i i i i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page vii | #7 i i i Contents 1 Introduction 1 1.1 Passive Coherent Locator (PCL) systems . .4 1.2 The Multiple-Input Multiple-Output radar concept . .5 1.3 Outline of the Thesis . .7 2 Antenna theory and array pattern synthesis 9 2.1 Main antenna parameters . .9 2.1.1 Directivity . 10 2.1.2 Efficiency . 10 2.1.3 Gain . 11 2.2 Antenna array pattern synthesis . 11 2.2.1 Linear array pattern synthesis . 14 2.2.2 Circular array pattern synthesis . 17 2.3 Pattern synthesis in non ideal arrays . 20 2.3.1 Mutual coupling . 20 2.3.2 Illumination errors . 21 2.4 Summary . 22 3 Digital beamforming for PCL 23 3.1 Digital processing scheme . 23 3.2 Mutual coupling compensation . 24 3.2.1 Analytical description . 24 3.2.2 Optimisation approach for the C matrix evaluation . 26 3.3 DBF for circular arrays . 27 3.3.1 Phase modes theory . 27 3.3.2 Proposed algorithm . 29 3.3.3 Array pattern comparisons . 31 3.4 Direct path interference suppression . 34 3.5 Summary . 35 i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page viii | #8 i i i viii Contents 4 PCL radar description and experimental results 37 4.1 Overview of the PCL system . 37 4.2 Antenna array analysis . 39 4.2.1 Array element characterisation . 39 4.2.2 Circular array characterisation . 41 4.3 PCL receiver . 43 4.3.1 Dynamic range analysis . 44 4.3.2 Digital down conversion . 46 4.4 Experimental results . 47 4.4.1 MC compensation . 47 4.4.2 Direct path interference suppression . 49 4.4.3 Range/Doppler processing . 51 4.4.4 CFAR detector and plots extraction . 52 4.5 System future improvements . 54 4.6 Summary . 54 5 Coherent MIMO array theory 57 5.1 Coherent MIMO array pattern synthesis . 57 5.1.1 Fourier-like transform representation of a MIMO array pattern 60 5.2 Waveform diversity/orthogonality concept . 62 5.3 Effect of the illumination errors on the pattern synthesis . 64 5.3.1 Simulated results . 70 5.4 Summary . 72 6 MIMO signal processing: RADOCA test board and experimental results 75 6.1 RADOCA MIMO radar description . 76 6.1.1 Antenna and PCB design . 78 6.2 Board calibration . 80 6.2.1 Experimental results . 82 6.3 Moving target detection in TDM MIMO radars . 84 6.3.1 Doppler speed impact . 86 6.3.2 Multi domain signal analysis . 87 6.3.3 Effect of the random selection of the active transmitter . 91 6.4 High resolution techniques applied to coherent MIMO arrays . 94 6.4.1 The MUltiple SIgnal Classification (MUSIC) method . 94 6.4.2 2D-MUSIC algorithm description . 95 6.4.3 Simulated and Experimental Results . 98 6.5 Summary . 101 i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page ix | #9 i i i Contents ix 7 Conclusion and outlook 103 7.1 Conclusions . 104 7.2 Recommendations and future work . 106 A PCL system measurements 109 A.1 Receiver channel gains . 109 A.2 Channel noise figures . 110 A.3 Element patterns . 111 B Illumination error effects on the synthesis of MIMO array pattern 115 C Basic theory of FMCW 121 List of Acronyms and Symbols 123 Bibliography 136 Summary 137 Samenvatting 139 Author's publications 141 About the author 143 Acknowledgements 145 i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page x | #10 i i i x Contents i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page xi | #11 i i i List of Figures 1.1 Sketch of an analog beamformer based on phase shifter components. .2 1.2 Basic digital beamforming scheme. .3 2.1 Generic antenna array geometry. 12 2.2 Linear antenna array geometry scanning on the xOz plane. 14 2.3 Normalised array pattern behaviors along the azimuthal plane (θ = 90o). 17 2.4 Circular antenna array geometry. 18 2.5 3D view of the array factor for an 8-elements UCA (linear scale). 19 2.6 Array factor for an 8-elements UCA along the azimuthal (θ = 90o, left) and the elevation (φ = 0o, right) planes. 19 3.1 Digital signal processing scheme of the PCL radar. 24 3.2 First kind Bessel functions of different orders. 29 3.3 Normalised UCA pattern and mask function fd(φ) of the desired pat- tern behavior. 30 3.4 Results of the proposed side lobe reduction method for a (a) UCA with radius r = 0:48λ, (b) UCA with radius r = 0:36λ............. 31 3.5 Results of the phase modes side lobe reduction method for a (a) UCA with radius r = 0:48λ, (b) UCA with radius r = 0:36λ.......... 32 3.6 Comparison between the phase modes and the proposed DBF tech- nique syntheses of a circular array pattern with radius r = 0:36λ and SLL=−19dB. 33 4.1 Block diagram of the PCL system. 38 4.2 TNO circular array for passive radar applications. 39 4.3 Simulated element pattern gain of a stand alone dipole considered as a single radiating element using CST: (a) 3D plot and (b) cut along the elevation plane (φ = 90◦).......................... 40 i i i i i \Main_Francesco_Thesis" | 2013/6/12 | 14:07 | page xii | #12 i i i xii LIST OF FIGURES 4.4 Simulated element pattern gain of a single dipole in the circular array configuration using CST: (a) 3D plot and (b) cut along the azimuthal plane (θ = 90◦)................................ 40 4.5 Comparison between the measured element patterns for three different array channels and the CST simulated data. 41 4.6 Array construction model used in the CST simulator. 42 4.7 Simulated circular array pattern gain using CST: (a) 3D plot and (b) \blue line": cut along the azimuthal plane (θ = 90◦) \red line": cut along the elevation plane (φ = 90◦). ................... 42 4.8 Rack of the PCL system analog receiver: (a) front view (b) internal view. 43 4.9 Block diagram of a receiving channel. 44 4.10 FM bandwidth input signals measured with the 6-th dipole of the array. 46 4.11 Representation of: a uniformly (a) and a sparsely (b) filled FM band. 47 4.12 (a) Sxx scattering parameters for the 8 channels of the array , (b) S1x scattering parameters with respect to the first element of the array. 48 4.13 (a) Relative (with respect to first array channel) phase shifts after dig- ital conversion, (b) Measured signal amplitudes after digital conversion. 48 4.14 Cartesian reference system comparison between the un-/calibrated and the theoretical patterns in dB scale for (a) transmission point 1 and (b) transmission point 2. 49 4.15 Effect of the DBF nulling procedure on the array pattern behavior. 50 4.16 Matched filter output Range-Doppler map. 52 4.17 GO-CFAR Time vs Range output map (a) and Overlapping of the CFAR detections with the ADSB available tracks data (b). 53 4.18 GO-CFAR Doppler Velocity vs Range output map (a) and Overlapping of the CFAR detections with the ADSB available tracks data (b). 53 5.1 Periodical array configuration of transmitting and receiving elements. 58 5.2 Different MIMO pattern contributions and realised pattern synthesis. 61 2 2 5.3 Error affected array pattern comparisons for (a) ∆ = σδ = 0:01, (b) 2 2 2 2 ∆ = 0:01 and σδ = 0:1, (c) ∆ = σδ = 0:1. 70 5.4 Analysis of the upper bound conditions for the average error patterns 2 2 2 2 for (a) ∆ = σδ = 0:001, (b) ∆ = 0:01 and σδ = 0:1.
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