DocumentCode :
836047
Title :
Impedance control of microstrip antennas using reactive loading
Author :
Ali-khan, Ajaz ; Richards, William F. ; Long, Stuart A.
Author_Institution :
Dept. of Electr. Eng., Houston Univ., TX, USA
Volume :
37
Issue :
2
fYear :
1989
Firstpage :
247
Lastpage :
251
Abstract :
It is shown that it is possible to change the input impedance of a microstrip antenna over a wide range without affecting its resonant frequency by moving short circuits along prescribed loci. This theory has been verified by experiment; specifically, it is shown that the resonant frequency of the mode is left relatively unchanged by the appropriate placement of the short circuit loads. The experiment also shows that the agreement between the predicted and observed input impedance is quite reasonable in most cases. There was qualitative agreement between theoretical antenna patterns and measured antenna patterns although the measured cross-polarized components in the double-loaded element were higher than expected from the theory. A single load, varying in position, was seen to provide a reasonable range of impedance variation while retaining a very nearly constant resonant frequency, although the resulting asymmetries in the magnetic current distribution caused a high level of cross-polarized fields. The use of two loads, instead, produced an even greater range of possible impedances, with reduced cross-polarization levels as well.<>
Keywords :
antenna radiation patterns; electric impedance; microstrip antennas; antenna patterns; cross-polarized components; double-loaded element; input impedance control; magnetic current distribution; microstrip antenna; reactive loading; resonant frequency; short circuit loads; single load; Antenna accessories; Antenna measurements; Antenna theory; Current distribution; Impedance; Loaded antennas; Magnetic resonance; Microstrip antennas; RLC circuits; Resonant frequency;
fLanguage :
English
Journal_Title :
Antennas and Propagation, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-926X
Type :
jour
DOI :
10.1109/8.18713
Filename :
18713
Link To Document :
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