《2.4GHz+抛物面天线的高效馈源（中英对照）》.pdf

Efficient Feed for Offset Parabolic Antennas for 2.4 GHz Dragoslav Dobričić, YU1AW 2.4GHz Resume This article examines some of the possible solutions to the problems of efficiently illuminating SAT TV offset parabolic antennas in the use on WLAN frequencies of 2.4 GHz.. Introduction The problems that occur while illuminating shallow offset parabolic dishes, in addition to those related to the efficient use of parabolic dishes generally are additionally aggravated by the specific geometry of the parabolic mirror itself. [2] Feed positioning in the way that its phase center exactly coincides with the focus of the offset parabolic dish and its aiming so that the radiation maximum falls in the geometric center of the elliptic reflector surface are not intuitive at all, as in classic parabolic antennas. Therefore, there is much confusion and many wrongly positioned feeds that do not correctly illuminate offset parabolic dishes, decreasing their efficiency and gain. The optimal feed for some given parabola has to fulfill several important characteristics: 1. The radiation angle of the main beam, between the points in which the gain is -10dB in relation to the maximal value, has to match the subtended angle. The feed radiation angle, both in horizontal and in vertical plane has to be the same, regardless the ellipticity of offset parabola. 2. The phase center of the feed has to be well defined and stable with changes of frequencies within the working range. The change of the phase within the whole angle of illumination has to be as small as possible. 1 November2009 3. The feed characteristics must not change much in the presence of the parabolic reflector and carrier structure. 4. Feed radiation diagram has to be very clean, i.e., with l