Coaxial cavity waveguide antennas excited by stacked circularmicrostrip patches for use as prime-focus reflector feeds

摘要

A coaxial cavity antenna excited by a stacked circular microstrip antenna is investigatedas a feed for prime-focus parabolic reflector antennas. The radiation pattern ofthe proposed cavity-backed antenna is saddle shaped, which widens the 210 dBbeamwidths and increases the reflector efficiency especially for deep reflectors withsmall focal length-to-diameter ratios. With a single-probe feed, the co-polar radiationpattern is slightly asymmetric in the E-plane, but is made symmetric by a differentialfeeding technique, using two probes. The impedance bandwidth of the proposed feedantenna is 20%. The antenna was fabricated and tested, and it exhibited good agreementbetween simulation and measurement results. The gain factor of the feed wasalso studied with a circular-symmetric reflector and provided a gain factor of 79% atf/D50.375. This type of feed can be used as an alternative to conventional horn orwaveguide feeds, where reduced size and light-weight are desirable with addedadvantage of easy integration with electronics.