Design, Manufacturing, and Testing of a Microwave...
Transcript of Design, Manufacturing, and Testing of a Microwave...
ECE 4600 GROUP DESIGN PROJECT PROPOSAL
Design, Manufacturing, and Testing of a Microwave Imaging System for
Breast Cancer
GROUP 5
GROUP MEMBERS
Rebecca Gole
Cameron MacGregor
Kyle Nemez
Michael Partyka
Bo Woods
DEPARTMENT SUPERVISOR
Dr. Joe LoVetri
CO-SUPERVISORS
Dr. Puyan Mojabi
Dr. Majid Ostadrahimi
September 27, 2013
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GROUP DESIGN PROJECT PROPOSAL PAGE 1 OF 9
1.0 Introduction There are two main methods of breast cancer imaging currently used by the medical
community: mammography and magnetic resonance imaging (MRI). Mammography is widely
used, but due to its harmful ionizing X-rays, the high rate of false positives, and the pain due to
necessary breast compression, an alternative imaging method is desirable. Similarly, MRI has
drawbacks such as high cost and lengthy scan times, making it unreasonable for mass screening.
Microwave imaging (MWI) is a promising alternative to mammography and MRI since it does
not involve ionizing radiation, patient discomfort, a high cost, or a lengthy scanning time [1].
MWI is performed by radiating an object with microwaves and measuring the resulting scattered
waves, which yield a dielectric map of the interior of the object. The difference in dielectric
properties between healthy and cancerous tissues allows for tumour detection.
The Electromagnetic Imaging Lab (EIL) at the University of Manitoba has developed the
necessary systems and software to generate images from measured data, but the lab requires new
prototypes specific to the breast imaging application [2, 3]. The proposed project encompasses
the design of the majority of the hardware components for a new MWI system suitable for breast
cancer imaging. The system architecture has been provided by the EIL along with the necessary
specifications for the hardware to be designed.
The system architecture is as follows. The object to be imaged is placed in a water-filled
chamber consisting of 24 waveguides in a circle. Each waveguide has five inward facing slots
which act as antennas, controlled by a diode probe located in front of each slot. When the probe is
off, the slot acts as a transmitter (Tx). When the probe is on, the slot is inactive. Finally, when
the probe is modulated between on and off, the slot acts as a receiver (Rx). RF energy is delivered
to one transmitting waveguide at a time and is collected by a different waveguide. A control
system selects a pair of waveguides and a single slot on each waveguide to form a Tx/Rx pair.
After a signal is collected by a waveguide, it is conditioned, digitized, and saved. A complete
scan occurs when data is collected for all possible Tx/Rx pairs.
Each designed component will be tested against the existing MWI prototype system in
the lab to verify operation. Accuracy and consistent performance are necessary in the
development of a reliable imaging system. Since the RF signals captured are of a low power level,
accurate detection and low noise amplification are also key design elements. Additionally, patient
safety must be taken into account as exposure to high levels of microwave radiation can cause
heating and damage to tissue [4].
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GROUP DESIGN PROJECT PROPOSAL PAGE 2 OF 9
2.0 Specifications The MWI system incorporates a number of hardware components as described in this
section. Figure 1 shows the general system overview.
FIGURE 1: System overview. Dotted lines indicate components provided by EIL.
2.1 Antennas
The antennas will be composed of two parts: a water-filled waveguide and a printed
circuit board (PCB) with 5 selectable slot antennas affixed to an open face of the water-filled
waveguide. The waveguide will be excited with a quarter-wave perpendicular feed, while the
probe driver circuit will control which of the antenna slots is transmitting/receiving energy, by
controlling the current flow through an RF diode across the center of the antenna slot.
TABLE 1: Antenna Specifications
RF operating frequency Single frequency between 800 MHz and 2 GHz
S11 at operating frequency At least -7 dB
Bandwidth At least 20 MHz
Number of slot antennas per waveguide 5
Operating medium Water
Number of waveguides 24
2.2 Frequency Synthesizer The frequency synthesizer will produce two RF outputs that differ only in power level.
One output will go to the RF switch and its designated waveguide, while the other will drive the
local oscillator (LO) port of the homodyne receiver. The output frequency and power level will be
adjusted by the control system (section 2.6).
RF FrequencySynthesizer
2 to 24 PortRF Switch
Antennas(Arranged in
Chamber)
Probe DriverCircuit
HomodyneReceiver
Lock InAmplifier
Data Acquisition
System&
Controller
UserInterface
Low FreqSynthesizer
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GROUP DESIGN PROJECT PROPOSAL PAGE 3 OF 9
TABLE 2: Frequency Synthesizer Specifications
RF frequency range 800 MHz – 2 GHz
Output 1 minimum power range -3 dBm to 0 dBm
Output 2 power At least 10 dBm
2.3 Probe Driver Circuit (PDC) The PDC will accept logic level signals from the control system. These signals address
which antenna slot should be Rx and which slot should be Tx. The PDC will switch the probes
between three states: slot inactive (20 mA current), slot transmitting (0 mA current), and slot
receiving (square wave with peak current of 20 mA).
TABLE 3: Probe Driver Circuit Specifications
Number of probes to drive 120
Peak current per probe 20 mA
Maximum modulation frequency to be handled 1 MHz
2.4 Homodyne Receiver The homodyne receiver will accept the signal picked up by the selected Rx antenna and
down-convert it from the RF frequency band to a signal centered at the modulation frequency. It
must mix the input signal with the in-phase (I) carrier and a 90° out-of-phase quadrature (Q)
carrier so that the amplitude and phase of the original signal can be determined.
TABLE 4: Homodyne Receiver Specifications
RF frequency range (LO & RF) 800 MHz – 2 GHz
Gain At least 15 dB
Isolation (LO to RF) At least -60 dB
Outputs In-phase (I) and quadrature (Q) of down-converted input
Minimum LO drive range -3 dBm to 0 dBm
2.5 Lock-In Amplifier (LIA) The LIA will mix each input signal from the homodyne receiver with a phase-locked in-
phase and quadrature-phase sine wave, producing four DC signals that are digitized. These four
signals are necessary to calculate the amplitude and phase of the received signal. Additionally, the
LIA provides a phase-locked square wave to the PDC at the modulation frequency.
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GROUP DESIGN PROJECT PROPOSAL PAGE 4 OF 9
TABLE 5: Lock-In Amplifier Specifications
Minimum operating frequency range 0 Hz (DC) - 1 MHz
Number of bits (A/D) At least 16
Minimum sampling rate (A/D) 20 kHz
Number of outputs 4 (I and Q for both inputs)
Square wave output Unipolar (0V – 5V), phase-locked to input sine wave
2.6 Data Acquisition System and Controller (DAQC) A control system is required to execute the breast scan. Under the direction of a
previously developed user interface, the control system will (1) set the RF frequency generated by
the frequency synthesizer; (2) direct the 2 to 24 port RF switch to switch between waveguides; (3)
direct the PDC to set each probe to one of the three states; and (4) save the measured electric field
data as outputted by the A/D converter of the LIA.
TABLE 6: Data Acquisition System and Controller Specifications
Minimum waveguide switching rate 33.3 Hz
Minimum probe switching rate 5 kHz
Maximum scan time 5 minutes
Minimum data acquired per scan 120 kB
2.7 Phantom A breast phantom (a model that simulates dielectric properties of the breast) will be
developed and used to test the imaging system. Recipes for desired breast tissue types
(fibroglandular, adipose, and cancerous tissue) will be fabricated and tested with a dielectric
probe [5]. These recipes consist of chemicals and other materials that are placed in a mold to
gelatinize, and the resulting phantom maintains its dielectric properties for approximately one
week. Once recipes for each tissue type are found, full breast phantoms will be fabricated as
necessary.
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GROUP DESIGN PROJECT PROPOSAL PAGE 5 OF 9
3.0 Tasks and Milestones 3.1 Project Phases
The project is divided into four phases to ensure that each part of the project is
progressing in a timely manner without limiting other components of the project.
Phase 1: Research, Design, and Parts Acquisition
During this phase of the project, team members will first become familiar with the
existing systems and methods used in the EIL. Next, each team member will begin designing
their respective components and chosen parts will be ordered.
Phase 2: Assembly and Component Testing
Once parts have been acquired, each component will be assembled and tested against the
intended specifications. If performance is not sufficient, replacement of components and/or
modification of design will be done iteratively until the specifications are met.
Phase 3: Component Interfacing
After independently testing system components and verifying operation, the necessary
interfacing between components will take place.
Phase 4: System Assembly and Testing
The final stage of the design process will be to assemble the system as a whole and run
calibration tests and scans of phantoms.
3.2 Task Assignments The project tasks are summarized in Table 7. Some tasks were completed between May
and August of 2013 and are not listed.
TABLE 7: Tasks Assignments
Component Task Task Owner PHASE 1: Research, Design, and Parts Acquisition Antennas Test antennas in free space KN & MO Antennas Design final antenna PCB KN & MO Antennas Manufacture PCB KN & MO Antennas Outsource waveguide fabrication KN & MO PDC Test and finalize CPLD choice KN PDC Design schematic KN PDC Design PCB layout KN PDC Order PCB and parts KN LIA Research LIAs and square-wave generation MP & BW LIA A/D converter design MP & BW
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GROUP DESIGN PROJECT PROPOSAL PAGE 6 OF 9
LIA Low-pass filter design MP & BW LIA Mixer design MP & BW LIA Square wave design MP & BW DAQC Research control system platforms and electrical interfaces RG & CM DAQC Select a control system platform RG & CM DAQC Select and design interface components RG & CM DAQC Purchase control system and interface components RG & CM DAQC Use existing µC to develop a scaled-down control system RG & CM Phantom Research phantom recipes RG Phantom Assemble required materials RG PHASE 2: Assembly and Component Testing Antennas Test antennas in water KN & MO Freq Synth Test design performance KN PDC Assemble & test KN Receiver Test design performance KN LIA Test ordered components against EIL LIA MP & BW LIA Assemble LIA components MP & BW DAQC Individually test interface components RG & CM DAQC Transfer phase 1 code from µC to new control platform RG & CM Phantom Try recipes and verify with dielectric probe RG Phantom Select recipes for all tissue types RG Phantom Fabricate phantom and scan with existing EIL system RG PHASE 3: Component Interfacing DAQC Finish control system code RG & CM All Interface all components All PHASE 4: System Assembly and Testing Antennas Form waveguides into chamber KN & MO DAQC Test control system and revise code as necessary RG & CM DAQC Perform final system integration and testing RG & CM Phantom Fabricate phantoms as necessary RG All Last minute modifications All All Final project submission All OTHER ITEMS Proposal All Informal progress report All Formal written progress report All Oral progress report All Final report All Final presentation All
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GROUP DESIGN PROJECT PROPOSAL PAGE 7 OF 9
4.0 Gantt Chart The project timeline is encapsulated in the Gantt chart, including tasks and milestones.
Tasks are grouped by project phases and specific components of the MWI system.
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GROUP DESIGN PROJECT PROPOSAL PAGE 8 OF 9
5.0 Budget The budget was compiled based on research of standard components (see Table 8). Taxes
and brokerage fees are included in the estimated costs.
TABLE 8: Budget
System Element Component Estimated Cost
RF Signal Generator Frequency synthesizer with evaluation board $190.00 Band-pass filter $88.00
Homodyne Receiver
Power amplifier $280.00 Power divider $35.00 Low noise amplifier $85.00 Matched 50 ohm loads $25.00 I/Q mixer $200.00
Antenna Chamber Aluminum tubing $47.00 Antenna printed circuit boards $120.00 Resistors, capacitors, LEDs, diodes $100.00
Probe Driver Circuit Complex programmable logic device $35.00 Other circuit elements $230.00 Custom printed circuit board $120.00
Lock-In Amplifier
4 x A/D converter $200.00 4 x Mixer $40.00 4 x Low-pass filter $100.00 Other circuit elements $20.00 Evaluation boards, PCBs $500.00
Data Acquisition System and Controller
Control system platform $140.00 Interface components $30.00
Phantom All materials provided by EIL $0.00 Shipping Costs $281.00
GRAND TOTAL $2,866.00
Note: Additional funding will be provided by the EIL to supplement the base budget allocated by
the department.
6.0 Conclusion In conclusion, MWI holds promise for improved breast cancer imaging. The necessary
research has been conducted and the appropriate tasks have been outlined in order to accomplish
the proposed project.
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GROUP DESIGN PROJECT PROPOSAL PAGE 9 OF 9
7.0 References
[1] N. K. Nikolova. (2011, Nov.). “Microwave imaging for breast cancer.” IEEE Microwave
Magazine. [Online]. 12(7), pp. 78-94. Available:
http://dx.doi.org/10.1109/MMM.2011.942702 [Sept. 19, 2013].
[2] C. Gilmore. “Towards an Improved Microwave Tomography System.” Ph.D. thesis,
University of Manitoba, Canada, 2009.
[3] M. Ostadrahimi. “Near-Field Microwave Tomography Systems and the Use of a Scatterer
Probe Technique.” Ph.D. thesis, University of Manitoba, Canada, 2011.
[4] IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency
Electromagnetic Fields, 3 KHz to 300 GHz, IEEE Standard C95.1, 2005.
[5] A. Trehan. “Numerical and Physical Models for Microwave Breast Imaging.” M.S. thesis,
McMaster University, Canada, 2009.