Design and Analysis of Input Impedance and Heating Performance of An Insulated Coaxial Slot Antenna in A Two-Layer Catheter for 915MHz Microwave Hyperthermia

• Main Authors: Huang, Jun-Hao, 黃俊皓
• Other Authors: Lin-Kun Wu
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/42321764259501258622

碩士 === 國立交通大學 === 電信工程研究所 === 86 === Insulated coaxial slot antennas (ICSA) and Insulated dipole antennas (IDA) are widely used in interstitial microwavehyperthermia. In this paper, wavenumber and characteristicimpedance models of insulated dipole antenna (IDA) in a single-layer catheter discussed by King et al. [12] are extended to the cases of IDA and ICSA in a two-layer catheter. Openings at both sides of the feed gap between arm one and arm two of theuniform ICSA are used to obtain two access current paths to shorten the physical length of the ICSA when compared with IDA. Moreover, input impedance of the ICSA depends upon the insertion depth, different insertion depths will lead to different return loss (S11). In order to solve the impedance matching problem, a quarter-wavelength choke is also imposed at the feed of the ICSA to prevent the current from flowing backward to the generator. Besides, an efficient and systematic designoptimization method is proposed for the design of ICSA to obtainthe desired current distribution along the axis of the antenna and thespatial specific absorption rate (SAR) pattern under good impedancematching. By the help of the efficient and systematic designoptimization of ICSA, we are capable of controlling the heating volume to fit into the specific shape and size of each individual tumor, and to prevent from corrupting the healthy tissues due to unnecessaryheating. Moreover, an air cooling system [19] can also be applied inthe two-layer catheter to take away the heat on the surface of the antenna and gain more radiation efficiency for the antenna. Of course, it will also reduce the pain of the patient and prevent fromdamaging the antenna caused by the over heating temperature on the antenna surface.