1 / 26

Design of a 3D Microwave Imaging System

Design of a 3D Microwave Imaging System. Drew Jaworski Advisor: Dr. Yong Zhou Fall 2011 – Senior Design I. Why Microwave Imaging?. Electromagnetic Imaging Systems Vision Nature doesn’t always know best! X-Ray Ionizing radiation Infrared (“thermal”) Limited to surfaces

mikasi
Download Presentation

Design of a 3D Microwave Imaging System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Design of a 3D Microwave Imaging System Drew Jaworski Advisor: Dr. Yong Zhou Fall 2011 – Senior Design I

  2. Why Microwave Imaging? • Electromagnetic Imaging Systems • Vision • Nature doesn’t always know best! • X-Ray • Ionizing radiation • Infrared (“thermal”) • Limited to surfaces • MRI (quantum mechanics) • Expensive • Microwave • Non-ionizing, penetrating, less expensive! • Applications • Medical imaging (cancerous tumors, etc) • Industrial scanning (forging defects, etc)

  3. Project Specifications • Design of a 3-dimensional microwave imaging system • Vector network analyzer signal analysis • Automated data acquirement and processing • Biomedical focus, but adaptable for other imaging applications • Multiplexed antenna array

  4. Project Constraints • Size • Entire system less than 1[m]*1[m]*1[m] • Budget • $300 from department + personal funds • FCC Regulations • Medical device band: 3.1[GHz]–10.6 [GHz] • Many others related to trying to manage the above constraints

  5. Electromagnetic Overview • Plane-wave approximation • Imaging subject located in far-field of antenna array, perpendicular to propagation of waves • Simplifies analysis at expense of system size • Scattering through media • A result of multiple layers of diffraction and refraction, in the case of the complex human body. Images courtesy of: http://en.wikipedia.org/wiki/File:Linear.Polarization.Linearly.Polarized.Light_plane.wave.svg http://commons.wikimedia.org/wiki/File:Huygens_brechung.png

  6. Vector Network Analyzer • Measures a Two Port Network • Returns S-Parameters (Scattering Parameters) • S11 – Return Loss • S21 – Insertion Loss • Parallel antennas connected to VNA ports • Calibrate response • Place object between antennas • Result is how the object affected the electromagnetic radiation between the two antennas • Results can be manipulated with software algorithms to give dielectric properties of the object!

  7. Inverse Scattering Solution • Repeat with multiple antennas (4x4 array, in this case) • Rotate object between antenna arrays • Result is a set of matrixes of scattering parameters for a 32-port network (for a range of frequencies!) • Can be manipulated to produce a discretized graphical representation of the dielectric properties in different regions between antenna arrays • Inverse Scattering Problem – Microwave Tomography • We know the forward transmitted radiation (aka Incident Fields) • We have information about the received fields (aka Scattered Fields) • Now we want to know what made them change! • Very complex calculations that are demanding of computing resources • Fortunately, much research has been published that has mathematically and/or computationally simplified the solution process (relatively)

  8. Automated Data Analysis • Labview • Automate collection of data • Several colleagues have worked out the details • Rotation mechanism – Juan Nava, Miguel Rivera • TTL communication (for multiplexer) – Julio Vasquez • Matlab • Process data • Numerous published algorithms can be implemented and tested

  9. Frequency Selection • Often limited by hardware technology (switch/antenna bandwidth) • Biomedical focus – human tissues • Estimates vary, best to come up with your own and justify accordingly • Begin with what spectrum is available • FCC • “Medical Systems: These devices must be operated in the frequency band 3.1-10.6 GHz. A medical imaging system may be used for a variety of health applications to “see” inside the body of a person or animal. Operation must be at the direction of, or under the supervision of, a licensed health care practitioner.” • http://transition.fcc.gov/Bureaus/Engineering_Technology/Orders/2002/fcc02048.pdf • Begin with properties of human body • Database of dielectric properties of numerous types of tissue available from Italian National Research Council site: • http://niremf.ifac.cnr.it/tissprop/

  10. Dielectric Properties Database • Skin (wet and Dry), Muscle, Fat, and Bone • Major constituents most body parts Highest λ Highest alpha Lowest λ Lowest alpha intersection intersection

  11. Antenna Array Multiplexer • Julio Vasquez’s RF multiplexer design intended for this project • Overlapping semesters meant his prototype was not yet completed and could not be used immediately • Microstrip antenna array with integrated multiplexer switch hierarchy • Avoids requirement of numerous expensive and tangled SMA patch cables • Integrates network of SPDT switches into antenna array • 4x4 microstrip antenna array • 1 SMA connector (patched to VNA) • 15 SPDT RF switches (operating up to 8[GHz]) • 16 microstrip patch antennas • 8 TTL-level (5V) control lines

  12. Antenna Array with Multiplexer

  13. RF Layout Guidelines • Line Widths • 3.08[mm] • 50Ω impedance • Curves • Ideally smooth curves • radius >= 3*lineWidth • Ground fills • Not completely necessary • Relatively noise-free environment • Noise reducing padding around experiment setup • Not feasible for hand-produced prototype • Tapered impedance tranformers • Linear (“triangular”) is best for wideband operation (Pozar) • λ/4 ~ λ used in design (as long as could be reasonably fit)

  14. Multiplexer versus Switch Network • Fully featured DC-12[GHz] multiplexer • $700 ~ $1700 • Single SPDT RF switch IC • $1 ~ $3 • M/A-COM technology solutions • MASW-007107 • Pros • Large variety of models available • Distributed by Mouser • Cons • Small package size (GaAs DIE ~ 4[mm]*4[mm]

  15. MASW-007107 Obtained from IC Datasheet: http://www.macomtech.com/DataSheets/MASW-007107.pdf

  16. MASW-007107 (continued)

  17. Switch Network Hierarchy

  18. UWB Microstrip Antenna • Two-port network theory (one-port input network, in this case) • S11 measures “return-loss” [dB] • Lower is better, -10[dB] indicates half of the input power is lost in the network • Return Loss is power radiated from antenna (hopefully) and other losses. • Bandwidth is measured where S11 crosses the -10[dB] point • Design is UWB when (BW / Fcenter) >= 25%

  19. UWB Microstrip Antenna (continued) • There are many published designs for UWB microstrip antennas • Most use complex ground geometries • Usually explain it as something to keep the phase response level across the useable band • After trying several designs, I began modifying the geometries in an attempt to find something new

  20. UWB Microstrip Antenna (continued) • BW = 979[MHz] • Fcenter = 5.595[GHz] • -10[dB] BW => 17.52% (close, but not UWB)

  21. UWB Microstrip Antenna (continued) • Fractal and/or self-symmetry based designs • Intended to induce multiple resonance frequencies Inspired by: Miniaturized UWB Monopole Microstrip Antenna Design by the Combination of Guisepe Peano and Sierpinksi Carpet Fractals, IEEE AWPL, 2011

  22. Budget (proposed) • Double-sided FR-4 boards (2x) • $12.66 + shipping <Parts Express> • MASW007107 RF Switches (50x) • $37.50 + shipping <Mouser Electronics> • Commercially Manufactured PCBs • $150 <Dorkbot PDX PCB group order> • All other supplies already in possession

  23. Gantt Chart – SD1

  24. Gantt Chart – SD2 (proposed)

  25. Future Work • Finalize UWB antenna candidate design • RF Layout of antenna array • Produce a prototype (using materials on hand) • Export Gerber file and have it manufactured commercially • $1 per square inch (min. 150 square inch order) • Develop mathematics of Imaging System • Microwave Imaging (2011), Matteo Pastorino • Begin making microwave images!

More Related