Optimization of Microstrip Patch Antenna Array
for Hyperthermic Treatment of Superficial Disease

Daniel George Neuman 2

San Francisco, California
December, 2000

Abstract: This thesis concerns the use of physical principles and engineering methods to optimize the design and performance of a new microwave antenna structure for use in cancer therapy. The arrays of microstrip patch antennas studied here were constructed from thin and flexible printed circuit board material for heating large areas of superficial tissue for applications such as Hyperthermic treatment of chestwall recurrence of breast carcinoma. Previous designs ignored certain microwave engineering considerations, leading to low efficiencies and excessive heating of the microstrip lines. This thesis concerns the optimization of these patch antenna arrays. Following the principles of microwave engineering and using modern test and diagnostic equipment, a microstrip-based matching network was designed to deliver microwave energy to the patch more efficiently.

Results of these design improvements demonstrate a quantitative improvement in efficiency of power transfer to the treatment volume and reduction of feedline heating. Parameters such as return loss and voltage standing wave ratio (VSWR) improved by up to a factor of two. It is hoped that this design optimization and consequent increase in efficiency will facilitate the widespread clinical use of the microstrip antenna arrays as hyperthermia applicators.

 

Indroduction

History and Motivation

Facts about Cancer

Hyperthermia as Cancer Treatment

Heating Mechanisms

Equipment and Techniques For Producing Hyperthermia in Superficial Tissues

Objectives

Microwave Theory

Impedance Mismatches

Quarter-Wave Transformer
Junctions
Source-microstrip transition

Materials and Methods

The Antenna Array

Network Analyzer

Network Analyzer Calibration Method
Time Domain Reflectometry
Gating
Standard Measurement Procedure
Network Analyzer Measurements
Finding the Edge Impedance
Microwave Network Parameters
Feedline Network Design

Electric Field/SAR Scans

Results and Analysis

Network Analyzer Data

Data From Non-Optimized Antenna Arrays
Data from Optimized Antenna Array
Representative Analyzer Results
Power Measurements

Power Balance Results

Electric Field - SAR Data

Conclusions

References



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