RADIATION-PATTERNS OF DUAL CONCENTRIC CONDUCTOR MICROSTRIP ANTENNAS FOR SUPERFICIAL HYPERTHERMIA

The finite difference time domain (FDTD) method has been used to calcu late electromagnetic radiation patterns from 915-MHz dual concentric c onductor (DCC) microwave antennas that are constructed from thin and f lexible printed circuit board (PCB) materials. Radiated field distribu tions are calculated in homogeneous lossy muscle tissue loads located under variable thickness coupling bolus layers. This effort extends th e results of previous investigations to consider more realistic applic ator configurations with smaller 2-cm square apertures and different c oupling bolus materials and thicknesses, as well as various spacings o f multiple-element arrays. Results are given for practical applicator designs with microstrip feedlines etched on the backside of the PCB an tenna array instead of previously tested bulky coaxial-cable feedline connections to each radiating aperture. The results demonstrate that f or an optimum coupling bolus thickness of 2.5-5 mm, the thin, flexible , and lightweight DCC antennas produce effective heating to the periph ery of each aperture to a depth of approximately 1 cm, and may be comb ined into arrays for uniform heating of large area superficial tissue regions with the 50% power deposition contour conforming closely to th e outer perimeter of the array.