Design, Manufacturing, and Testing of a Microwave …ece.eng.umanitoba.ca/undergraduate/ECE4600/ECE4600/Archive/2013/... · Design, Manufacturing, and Testing of a Microwave Imaging

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

GROUP 5 ECE 4600

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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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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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.

GROUP 5 ECE 4600


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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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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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

GROUP 5 ECE 4600


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 5 ECE 4600


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.

GROUP 5 ECE 4600


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.

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Design, Manufacturing, and Testing of a Microwave …ece.eng.umanitoba.ca/undergraduate/ECE4600/ECE4600/Archive/2013/... · Design, Manufacturing, and Testing of a Microwave Imaging