Browsing by Author "Su, DWF"

Now showing 1 - 3 of 3

A fast algorithm for computing field radiated by an insulated dipole antenna in dissipative medium
(1996-12-01)
Wu, LK
;
Su, DWF
;
Tseng, BC
;
交大名義發表
;
傳播研究所
A fast algorithm for determining the near-field characteristics of an insulated dipole antenna (IDA) embedded in a homogenous dissipative medium is described in this paper. A thin-wire-approximation type of analysis is followed here. In this case, radiation is considered to originate from a filamentary current flowing along the axis of the dipole, which is surrounded immediately hy the ambient dissipative medium, The translational symmetry inherent in the resultant radiation integrals is then exploited to speed up the computation. In one case studied, the basic thin-wire approach that uses no symmetry property is found to yield accurate results in approximately 380 times less CPU time than the traditional King-Casey approach, In another case, use of symmetry property further reduces the CPU time by a factor of 7; additional reduction in CPU time is possible by taking into account the near-field nature of the problem.
Design and analysis of an asymmetrically fed insulated coaxial slot antenna with enhanced tip-heating performance
(2000-08-01)
Wu, LK
;
Su, DWF
;
傳播研究所
;
Institute of Communication Studies
In this paper, a novel use of an asymmetrically fed insulated coaxial slot antenna (ICSA) type of applicator for interstitial microwave hyperthermia that simultaneously exhibits good impedance matching and enhanced tip-heating performances is presented. Theoretical analysis reveals that by making the distal arm much shorter than the other arm of the antenna, charge densities distributed over the distal arm of the antenna increase significantly. This, in turn, can result in the-radial electric-field component becoming the dominant contributor to the specific absorption rate (SAR) over the distal arm side of the heating region and, therefore, the achievement of enhanced tip-heating performance, With the length of the longer arm chosen to be slightly longer than a quarter-wavelength, good impedance matching and enhanced tip-heating performances are achieved when the length of the shorter distal arm is reduced to no more than 25% of that of the longer arm, Good agreements observed between theoretical and measured SAR patterns for two ICSA's designed for operation at 915 and 433 MHz, respectively, confirm the validity of the design method.
Input impedance characteristics of coaxial slot antennas for interstitial microwave hyperthermia
(1999-03-01)
Su, DWF
;
Wu, LK
;
傳播研究所
;
Institute of Communication Studies
In this paper, a transmission-line type of input impedance model originally developed by King ct al. [4] for the insulated dipole antenna embedded in a homogeneous dissipative medium is extended to the case of insulated coaxial slot antenna, Physical construction of the latter indicates the presence of additional current path(s) inside the feed line, which shall lead to the shortening of its resonance length, This effect is taken into account in the impedance model and verified by experiments, Furthermore, a simple strategy for optimizing the applicator's impedance-matching performance is also described and verified. Excellent agreements observed between theoretical and measured S-11 data indicate that these models can be relied upon when designing an efficient applicator for interstitial microwave hyperthermia.