GROUP 5 ECE 4600

ECE 4600

FORMAL WRITTEN PROGRESS REPORT

Design of a Microwave Imaging System for Breast Cancer Detection

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

Covering the period of: May 1, 2013 to January 13, 2014

Submitted on: January 13, 2014

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FORMAL WRITTEN PROGRESS REPORT ii

Table of Contents

List of Acronyms………………………………………………..……... iii

1. Introduction………………………………………………………... 1

2. Progress……………………………………………………………. 1

2.1. Antennas…………………………………………………………………... 1

2.2. Frequency Synthesizer…………………………………………………….. 2

2.3. Probe Driver Circuit……………………………………………………….. 2

2.4. Homodyne Receiver……………………………………………………….. 2

2.5. Lock-In Amplifier…………………………………………………………. 3

2.6. Data Acquisition System and Controller………………………………….. 4

2.7. Phantom…………………………………………………………………… 4

3. Future Work………………………………………………………... 5

3.1. Antennas…………………………………………………………………... 5

3.2. Lock-In Amplifier…………………………………………………………. 5

3.3. Data Acquisition System and Controller………………………………….. 5

3.4. Phantom…………………………………………………………………… 5

4. Conclusion……………………………….………………………… 5

Appendix A – Gantt Chart….…………………………………………. 6

Appendix B – Budget..………………………………………………… 8

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FORMAL WRITTEN PROGRESS REPORT iii

List of Acronyms

ADC – Analog-to-Digital Converter

CPLD – Complex Programmable Logic Device

DAQC – Data Acquisition System and Controller

EIL – Electromagnetic Imaging Laboratory

GPIB – General Purpose Interface Bus

LIA – Lock-In Amplifier

LO – Local Oscillator

LPF – Low Pass Filter

MWI – Microwave Imaging

PCB – Printed Circuit Board

RF – Radio Frequency

Rx – Receive or Receiver

Tx – Transmit or Transmitter

VSWR – Voltage Standing Wave Ratio

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FORMAL WRITTEN PROGRESS REPORT PAGE 1 OF 10

1.0 Introduction

The aim of our project is to design and prototype the hardware required for a

novel microwave imaging (MWI) system intended for breast cancer detection. We are

also designing breast phantoms to test our system. Our project includes the design of all

hardware components except for the radio frequency (RF) switch and the low frequency

synthesizer. The functional system will consist of an antenna chamber into which the

phantom will be placed and subsequently illuminated by microwaves, a frequency

synthesizer that generates the microwaves, and a probe driver circuit (PDC) that

controls which waveguide slots act as transmitter (Tx) and receiver (Rx). In addition,

the system includes a homodyne receiver and a lock-in amplifier (LIA); both of which

serve to condition the signal measured at the receiving antenna. Lastly, a data

acquisition system and controller (DAQC) is included that is responsible for sampling

the conditioned signal and controls the scan.

2.0 Progress

Some components of the project are behind schedule, while other parts are ahead

of schedule (refer to Gantt chart, appendix A). Overall, progress has either met or

exceeded expectations in all aspects of the project.

2.1 Antennas

At the heart of the MWI system is the imaging chamber, containing 24 antennas,

which receive and transmit the signals required to generate an image. Each antenna,

designed to operate in water, consists of a waveguide with five selectable /2 slot

antennas on one face. At the onset of the project, Dr. Majid Ostadrahimi completed a

preliminary antenna design that required testing and refinement. Kyle refined the design

by adjusting the waveguide feed length, measuring the H-field distribution along the

waveguide, and measuring switching diode sensitivity. To prevent short-circuiting and

thus ensure adequate operation while submerged, a sprayable rubber compound was

found that could coat the exposed circuitry. Kyle was then responsible for designing the

printed circuit board (PCB) containing the slots once the dimensions and slot positions

were finalized. Manufacturing of the waveguide-based imaging chamber was contracted

out to the Cancer Care machine shop in Winnipeg. The PCBs have been manufactured,

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FORMAL WRITTEN PROGRESS REPORT PAGE 2 OF 10

assembled, coated in the rubber compound, and sent to the Cancer Care machine shop for

final placement in the chamber. The antenna chamber assembly is almost complete. We

expect to receive the completed chamber from Cancer Care within three weeks.

2.2 Frequency Synthesizer

The frequency synthesizer generates the RF energy that is radiated by the transmit

antennas and drives the local oscillator (LO) port of the homodyne receiver. Since

commercial frequency synthesizer circuits are available at a lower cost than a new design,

an evaluation board from Analog Devices (ADF4351) was selected. The board was

designed by the manufacturer to be controlled by a computer, and Kyle successfully

modified the board to be controlled by the DAQC. Under initial testing, the 2nd

and 3rd

order harmonics were undesirably large, so a band pass filter was added. Kyle also chose

a power splitter and amplifier to split the filter output and deliver power to both the LO

port of the homodyne receiver and the Tx antenna. Testing and implementation of the

frequency synthesizer is complete.

2.3 Probe Driver Circuit

The probe driver circuit (PDC) allows the DAQC to control which slot transmits

and which slot receives microwaves. Kyle designed a logic circuit to control all 120 slots

with 16 digital control lines. To implement the design, two options were considered: a

number of discrete logic gates and a programmable logic device. A complex

programmable logic device (CPLD) based design was chosen because of its flexibility

and reliability.

To properly control the antenna slots, the logic level signals from the CPLD must

be translated to higher voltage switching signals. Kyle investigated several technologies

that could accomplish this translation. Darlington transistor pairs (ULN2803) were

selected because of their low cost, previous successful use in the lab, and sufficient

performance under our tests. Kyle subsequently designed two PCBs, one to mount the

CPLD and one to mount the translation circuitry. The finalized PCB designs were sent

for manufacturing and assembled upon reception. Work on the PDC is complete.

2.4 Homodyne Receiver

The homodyne receiver down-converts the received RF signal by mixing it with

the transmit signal. Instead of chips on a custom PCB, mounted components with co-

axial connectors were used to reduce cost and shorten implementation time. Kyle and Dr.

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FORMAL WRITTEN PROGRESS REPORT PAGE 3 OF 10

Ostadrahimi established the receiver topology. Kyle chose parts with suitable gain,

voltage standing wave ratio (VSWR), and bandwidth. The machine shop mounted the

parts on a metal plate to create a robust circuit. The receiver was tested with two

prototype antennas, and performed better than required. The design and implementation

of the homodyne receiver is complete.

2.5 Lock-In Amplifier

The LIA conditions the signal from the homodyne receiver for digitization by the

analog-to-digital converter (ADC). The LIA consists of a mixer, a low-pass filter

(LPF), and a comparator. Design of the LIA is nearly complete. Overall, the LIA progress

is on schedule except for the unexpected delay due to the defective mixer. Michael and

Bo are working together to design, test, and implement the LIA.

The mixer produces the locked-in signal with additional high-frequency

harmonics. After evaluating many standalone mixers, hybrid couplers, and phase shifters,

we found an evaluation board (AD8333) containing everything we needed in one package.

We tested the board by applying two frequencies at the inputs of the board. The measured

results we obtained were alarming as the board did not function as we expected. We

suspected that the board was defective, so we returned the board to Digi-Key for further

analysis. Digi-Key has confirmed that the board was defective. A replacement board has

now arrived so we will be able to get back on schedule.

After the mixer, the LPF removes any remaining harmonics or distortion. We

determined that it would be easier and cheaper to build our own active second order

Sallen-Key LPF. By creating our own filter, we can control circuit parameters with

greater ease than with a manufactured filter. We tested our designed filter using a

breadboard, a signal generator, and an oscilloscope. The filter worked exactly as planned

and it has been included in our preliminary PCB design.

The comparator generates a phase-locked square wave from a reference sine wave.

Initially, we tested a number of different operational amplifiers in a bi-stable

multivibrator configuration, which yielded marginally acceptable results consisting of

ringing and distortion in the output waveform. We later discovered that operating an

operational amplifier near the rail voltages typically exhibits non-ideal characteristics.

The solution to these non-ideal characteristics was to use a comparator chip, which was

designed to be driven with high current in order to provide a fast and desirable response.

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FORMAL WRITTEN PROGRESS REPORT PAGE 4 OF 10

The selected comparator chip has been tested and it functions as expected.

2.6 Data Acquisition System and Controller

The DAQC controls the various sub-components of the system. Prior to a scan,

the DAQC accepts the scan settings from the user and configures the frequency

synthesizer according to the scan settings. During a scan, the DAQC periodically

switches the PDC and RF switch in a timed manner according to the scan settings,

acquires the digitized microwave measurements from the ADCs, and transmits these

measurements to an external computer. To date, we have selected an embedded

computing system to implement the DAQC, designed and tested the electrical and

software interfaces to the PDC and frequency synthesizer, and programmed the main scan

control sequence. Overall, the DAQC is on schedule, except for a delay due to interfacing

with the RF switch. Cameron and Rebecca are working together to design, test, and

implement the DAQC.

Our first task was to select an embedded computing system for the DAQC that

would best help us meet the project specifications. We researched various embedded

systems, and selected the Stellaris LaunchPad since it has superior coding and debugging

options compared to other embedded systems.

We have designed the electrical and software interfaces to the four ADCs, the

PDC, and the frequency synthesizer. Cameron designed an interface that allows the

digitized microwave measurements to be read from the four ADCs in parallel. He also

designed and tested the interface to the PDC. Rebecca designed and tested the interface to

the frequency synthesizer. She determined an algorithm to compute the necessary register

values to set the output frequency and signal power, as well as mute the output signal.

Connecting the LaunchPad to the general purpose interface bus (GPIB) on the

mechanical RF switch has proven to be difficult to implement. Originally, we were

expecting to implement a simple serial interface to a new RF switch designed by another

member of the Electromagnetic Imaging Laboratory (EIL). The new switch, however,

may not be ready within the timeline of this project, so the existing mechanical switch,

with a GPIB interface, must be used.

2.7 Phantom

A breast phantom, which mimics the dielectric properties of breast tissues, will be

fabricated to test the MWI system. Rebecca and Cameron Kaye, a member of the EIL, are

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FORMAL WRITTEN PROGRESS REPORT PAGE 5 OF 10

responsible for phantom design. We found recipes, which consist of water mixed with

hardening agents such as alginate, to represent tumour tissue and fibroglandular tissue.

Next, we created samples and determined their longevity by observing how their

dielectric properties changed over time, as the samples dried out. We also found a recipe

to simulate adipose tissue, but have yet to create samples to verify this recipe.

3.0 Future Work

Work continues on the antennas, LIA, DAQC, and phantom.

3.1 Antennas

When chamber assembly is complete, testing and calibration will be performed.

3.2 Lock-In Amplifier

Once the new mixer has been tested, which will occur in the coming weeks, the

LIA will be back on schedule. Future work for the LIA involves finishing the PCB design,

ordering the PCB (refer to budget, appendix B), and testing the entire LIA.

3.3 Data Acquisition System and Controller

We will determine and implement the method of interfacing with the RF switch

within three weeks. We also need to verify that the interface to the four ADCs works as

designed. Next, we will merge the code for the various components and test the program

to verify the DAQC meets the specifications.

3.4 Phantom

The recipe for an adipose tissue phantom needs to be verified by creating an

adipose phantom and measuring the dielectric properties. Then, we will make a phantom

consisting of all three tissue types. Additionally, we must find the best option to seal the

phantom from the water used in the antenna chamber.

4.0 Conclusion

We have shown major progress in all areas of our project. Design, implementation,

and testing of the frequency synthesizer, PDC, and homodyne receiver are complete.

Work is almost finished on the antenna chamber, LIA, DAQC, and phantom. Though we

have faced unexpected problems in designing the DAQC and LIA, progress has been

excellent. We expect to have a functional system at our final presentation.

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Appendix A – Gantt Chart

Please refer to the Gantt chart in Figure A-1 for an overview of the project. The

Gantt chart has changed compared to the Gantt chart in our proposal. We now show dates

for tasks that started in the summer of 2013 and we have organized the tasks by each

separate component, which was further broken down into four colour-coded phases. The

Gantt chart also has been modified to reflect the delay due to the defective mixer for the

LIA.

Note that Kyle has contributed more time to this project because he was working

full-time in the EIL throughout the summer on MWI system design. A large proportion of

his work was found to be immediately applicable to this project, and was thus absorbed

by this project.

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FORMAL WRITTEN PROGRESS REPORT PAGE 7 OF 10

FIGURE A-1: Gantt chart.

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Appendix B – Budget

Please refer to Table B-1 for the costs incurred by the project thus far. Some items

have cost more than expected, while others have cost much less. The initial projected cost

of the project was $2866, consisting of $500 in funding from the ECE department and

$2366 in extra funding provided by our supervisor. We estimate that we will be below

our original budget by $139.80.

TABLE B-1: Budget

Component Component

Element Part Number Supplier Quantity Total

Cost

Antennas

Rectangular

Aluminum

Tubing

6365 Online

Metals 20 ft $47

Antenna PCBs N/A RayPCB 36 $120

220Ω Resistor P220ADCT-ND Digi-Key 100 $8.15

220pF Capacitor 720-1330-1-ND Digi-Key 100 $72.50

Red LED VLMS1300-

GS08CT-ND Digi-Key 50 $14.54

RF Diodes BAR 64-02V

H6327TR-ND Digi-Key 50 $5.24

Pin Headers N/A Tech Shop 24 $0.00

Freq.

Synth.

Frequency

Synthesizer

Board

ADF4351EB1Z Digi-Key 1 $188.7

9

Band Pass Filter N/A eBay 1 $88

Power Splitter ZX10-2-252-S+ Minicircuits 1 $31.95

Power Amplifier ZFL-2500VH+ Minicircuits 1 $264.9

5

PDC CPLD XCR3256XL-

12PQ208C

Avnet

Express 2 $33.90

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FORMAL WRITTEN PROGRESS REPORT PAGE 9 OF 10

Voltage

Regulator

LM317MDTGOS

-ND Digi-Key 1 $0.79

220Ω Resistor P220FCT-ND Digi-Key 4 $0.48

360Ω Resistor P360FCT-ND Digi-Key 4 $0.48

1uF Capacitor 399-3678-1-ND Digi-Key 4 $1.52

0.1uF Capacitor 399-3676-1-ND Digi-Key 4 $1.68

Bussed 10kΩ

Resistors

4605X-101-

103LF Digi-Key 1 $0.32

CPLD PCB N/A RayPCB 2 $100

3.3V to 5V

Logic Converter

MC74HCT245A

DWGOS-ND Digi-Key 20 $12.10

Darlington

Transistor Chip

ULN2803AFWG

(CELHACT-ND) Digi-Key 20 $16.20

220Ω Chip

Resistor

SOMC220HCT-

ND Digi-Key 20 $22.00

BNC Connectors A101972-ND Digi-Key 5 $20.75

56pF Capacitors 490-3580-1-ND Digi-Key 100 $41.00

10uF Capacitors 490-3897-1-ND Digi-Key 100 $4.00

Probe Driver

PCB N/A RayPCB 1 $120

Ribbon Cable

Ends 2-1658527-0 Digi-Key 50

$126.7

3

12 Pin Ribbon

Cable N/A Tech Shop 144 ft $0.00

Pin Headers N/A Tech Shop N/A $0.00

Homodyne

Receiver

Low Noise

Amplifier ZX60-33LN-S+ Minicircuits 1 $79.95

I/Q Mixer ADL5382 Digi-Key 1 $215.7

7

LIA A/D Converter AD977A Digi-Key 5 $250

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FORMAL WRITTEN PROGRESS REPORT PAGE 10 OF 10

Operational

Amplifier AD8004 Digi-Key 2 $40

Operational

Amplifier AD8042 Digi-Key 1 $6.52

Operational

Amplifier LT1363CN8 Digi-Key 2 $10.04

Operational

Amplifier OP284EP Digi-Key 3 $40.00

Comparator AD8561 Digi-Key 2 $5.00

I/Q Mixer AD8333 Digi-Key 1 $400

Resistors, caps,

etc. N/A Digi-Key N/A $30.00

Frequency

Synthesizer AD9833 Digi-Key 1 $80.00

SMB to SMA

Adapater 931-1104-ND Digi-Key 1 $10.00

DAQC Stellaris

Launchpad LM4F120 Digi-Key 1 $14.99

8-Bit Shift

Register SN74HC595N Digi-Key 2 $0.70

USB to UART

Bridge UB232R Digi-Key 1 $20.14

Phantom All components

provided by EIL N/A EIL N/A $0.00

Shipping Various

Shipping Costs N/A N/A 1 $60

Total Incurred Expenses: $2606.20

Projected Future Expenses: $120 (1 custom PCB $120)

Total Projected Project Cost: $2726.20