Millimeter Wave Imaging for Security Applications (Millimetergolf beeldvorming voor beveiligingstoepassingen)

With the increasing demand for homeland security in recent years, there has beena wide range of system proposals for using millimeter wave band scanners forconcealed object detection. Different systems have evolved during the years whichare not only different in terms of the frequency range they employ, 30-300 GHz, butare also significantly different in terms of system topology and concept of operation.This research focuses on two main streams. Firstly, a system modeling techniquehas been developed that allows the evaluation of different system architectures.This software tool enhances the system selection and component evaluation toa wide extent. Secondly we have tackled the component design and fabrication,with a focus on the detector antenna and circuitry. Regarding the first part of thework we have developed and optimized a fast and accurate method, based on theHuygens wave propagation principle, that provides us the ability to model a fullsystem with given setup dimensions and spacing. It provides a reconstruction ofthe expected image on the detector. It also provides useful information such aspower level and dynamic range of the received signal. Furthermore the methodis used as a design tool to optimize a lens for a given setup. Towards the secondpart of this research, we have designed and fabricated two types of antennas usingdifferent technologies. Performance of patch antennas fabricated on a multi-chipmodule process on high-resistive silicon was improved using bulk vias reducingthe substrate wave leakage. A low cost thin-film wideband antenna has also beenfabricated with promising measurement results. The antenna performance has beenmeasured with a novel measurement setup. We have also tackled a 100 GHz lownoise amplifier design, fabricated using a commercial BiCMOS process. The dualstage LNA uses a novel topology which significantly relaxes the output mForeword i Abstract iii Samenvatting v List of symbols xi List of Figures xix List of Tables xxv 1 Motivation and overview 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation to this work . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Overview of the PhD thesis . . . . . . . . . . . . . . . . . . . . . . 3 2 An introduction to millimeter wave imaging systems 5 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Millimeter wave imaging systems in general . . . . . . . . . . . . . 6 2.3 Active and passive systems . . . . . . . . . . . . . . . . . . . . . . 7 2.3.1 Passive mm-wave imaging . . . . . . . . . . . . . . . . . . . 8 2.3.2 Examples of passive mm-wave imaging systems . . . . . . . 10 2.3.3 Active mm-wave imaging . . . . . . . . . . . . . . . . . . . 12 2.3.4 Examples of active mm-wave imaging systems . . . . . . . . 13 2.4 Beam forming [using lenses, mirrors, or phased array antennas] . . 16 2.5 Millimeter wave detectors . . . . . . . . . . . . . . . . . . . . . . . 20 2.5.1 Microbolometer focal plain arrays . . . . . . . . . . . . . . 20 2.5.2 Direct detection receivers . . . . . . . . . . . . . . . . . . . 21 2.5.3 Superheterodyne receivers . . . . . . . . . . . . . . . . . . . 22 2.6 Interconnects for millimeter wave detectors . . . . . . . . . . . . . 23 2.6.1 Flip-chip vs wire bond attachments . . . . . . . . . . . . . 26 2.7 Antennas for millimeter wave detectors . . . . . . . . . . . . . . . . 27 2.7.1 Printed layer/multilayer antennas . . . . . . . . . . . . . . 28 2.7.2 Antennas on LTCC . . . . . . . . . . . . . . . . . . . . . . . 29 2.7.3 Antennas on MCM . . . . . . . . . . . . . . . . . . . . . . . 31 2.7.4 On-chip antennas . . . . . . . . . . . . . . . . . . . . . . . 31 2.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3 Modeling a millimeter wave imaging system 35 3.1 An introduction to Fourier optics . . . . . . . . . . . . . . . . . . . 35 3.1.1 The Helmholtz equations . . . . . . . . . . . . . . . . . . . 36 3.1.2 Green’s theorem . . . . . . . . . . . . . . . . . . . . . . . . 37 3.1.3 The integral theorem of Helmholtz-Kirchhoff . . . . . . . . 37 3.1.4 The Kirchhoff formulation of diffraction by a plane screen . 39 3.1.5 The Rayleigh-Sommerfeld solutions . . . . . . . . . . . . . . 41 3.2 2 . 5 D analysis based on Huygens’ principle . . . . . . . . . . . . . 45 3.2.1 The modeling method . . . . . . . . . . . . . . . . . . . . . 45 3.2.2 Speckles and the Hadamard technique . . . . . . . . . . . . 48 3.2.3 The effect of the lens dimensions . . . . . . . . . . . . . . . 51 3.2.4 Calculation of the power levels . . . . . . . . . . . . . . . . 51 3.3 Resource efficient calculations using FFT . . . . . . . . . . . . . . 55 3.3.1 The FFT based evaluation of the electrical field . . . . . . . 55 3.3.2 Case studies of the FFT method . . . . . . . . . . . . . . . 56 3.4 Lens models and new designs . . . . . . . . . . . . . . . . . . . . . 58 3.4.1 Spherical cross-section lens . . . . . . . . . . . . . . . . . . 59 3.4.2 Focally optimized lens . . . . . . . . . . . . . . . . . . . . . 63 3.4.3 Image optimized lens . . . . . . . . . . . . . . . . . . . . . . 64 3.4.4 Frequency dependencies . . . . . . . . . . . . . . . . . . . . 68 3.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4 Antennas for millimeter wave imaging 69 4.1 An introduction to antenna parameters and analysis . . . . . . . . 69 4.1.1 Radiation intensity . . . . . . . . . . . . . . . . . . . . . . 71 4.1.2 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4.1.3 Radiation patterns . . . . . . . . . . . . . . . . . . . . . . 74 4.1.4 Directivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.1.5 Antenna return loss and efficiency . . . . . . . . . . . . . . 76 4.1.6 Antenna gain . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.1.7 Antenna bandwidth . . . . . . . . . . . . . . . . . . . . . . 77 4.2 A reminder on antenna analysis . . . . . . . . . . . . . . . . . . . . 78 4.2.1 Far-field evaluations based on vector potentials . . . . . . . 78 4.2.2 Example of the far-fields of an open aperture . . . . . . . . 81 4.3 The microstrip patch antenna . . . . . . . . . . . . . . . . . . . . 84 4.3.1 The transmission line model for a patch antenna . . . . . . 84 4.3.2 The cavity model for a patch antenna . . . . . . . . . . . . 89 4.3.3 Design procedure . . . . . . . . . . . . . . . . . . . . . . . 95 4.4 Patch antennas for mm-wave applications . . . . . . . . . . . . . . 95 4.4.1 Microstrip patch antennas fabricated using the MCM-D process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 4.4.2 Patch antenna measurements and radiation patterns . . . . 99 4.4.3 Patch antenna efficiency . . . . . . . . . . . . . . . . . . . 102 4.5 Biconical dipole and bow-tie antennas . . . . . . . . . . . . . . . . 105 4.5.1 Biconical dipole . . . . . . . . . . . . . . . . . . . . . . . . 105 4.5.2 Bow-tie and slot bow-tie antennas . . . . . . . . . . . . . . 108 4.6 Slot bow-tie antenna for mm-wave applications . . . . . . . . . . . 110 4.6.1 Slot bow-tie antenna design . . . . . . . . . . . . . . . . . 110 4.6.2 Slot bow-tie antenna measurements and radiation patterns 112 4.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 5 Low noise amplifier design for millimeter wave applications 117 5.1 Basics of low noise amplifiers . . . . . . . . . . . . . . . . . . . . . 118 5.1.1 Stability and gain of RF amplifiers . . . . . . . . . . . . . . 118 5.1.2 Low noise amplifiers based on GA design . . . . . . . . . . 122 5.2 Case study of a low noise amplifier design at 100 GHz . . . . . . . 127 5.2.1 The process overview . . . . . . . . . . . . . . . . . . . . . 127 5.2.2 De-embedding and transmission line characterization . . . 128 5.2.3 Interconnections and bias networks . . . . . . . . . . . . . . 131 5.2.4 Design topology . . . . . . . . . . . . . . . . . . . . . . . . 136 5.2.5 Design flow . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 5.2.6 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . 140 5.2.7 Post fabrication simulations . . . . . . . . . . . . . . . . . 141 5.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 6 Conclusions 147 Bibliography 151 List of publications 159 Curriculum vitae 163nrpages: 163status: publishe