Abstract
Parabolic symmetric and offset reflector antennas adaptively illuminated using a novel triple-mode feedhorn (TE11+TM01+TE21) with different mode combinations and impedance and radiation performances are presented. The combination of the radiating modes in a feedhorn with proper amplitude and fixed phase values helps in electronically pointing the main beam of the radiating patterns such as that obtained in a beam-steering antenna with limited beam-scan range. This type of radiation performance virtually creates a displaced phase center location for the feedhorn, which, consequently, adaptively illuminates the reflector antenna surface. Impedance-matching bandwidths are preserved for both reflector antennas similar to the case of feedhorn alone. The copolarization gain and peak cross-polarization levels are far better with the offset reflector antenna than the symmetric reflector antenna. Such reflector antennas find applications in ground moving target indicator (GMTI) and space based radars. The investigation results are solely computed using FEKO full-wave analysis tool.
Highlights
Reflector and feedhorn antenna assemblies have been widely used for various applications requiring high gain and narrow beamwidth radiation patterns such as satellite communications and radar applications [1]
The beam scanning capability directly translates to the change is phase center location of the feedhorn as discussed in [2, 3], we only show phase center for a selected power contents for the mode combination with the fixed phase values
A triple-mode feedhorn was employed as a source to the symmetric and offset reflector antennas
Summary
Reflector and feedhorn antenna assemblies have been widely used for various applications requiring high gain and narrow beamwidth radiation patterns such as satellite communications and radar applications [1]. A dual mode horn as a feed source was investigated for symmetric and offset reflector antennas in [2, 3] where TE11 and TM01 modes were excited to generate horizontal (Phi = 0◦) plane multiple phase centers and reflector antenna radiation performance was presented. This antenna had a targeted application for the GMTI radar. Reflector antenna impedance matching and radiation performance are investigated for both the symmetric and offset reflectors and a comparison is made when only two modes from the feedhorn are excited at a time. While method of moment (MOM) is used for feedhorn analysis, reflector antenna performance is computed using physical optics (PO) method using hybridization technique inbuilt with the FEKO
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