مرکز منطقه ای اطلاع رساني علوم و فناوري - Unidirectional patterns of traveling-wave rectangular antenna

Abstract :

A traveling-wave rectangular antenna, for which the feeding point is placed at the center of a leg and the matching impedance is terminated at the opposite leg, is considered. This antenna has two kinds of quasi-nonsidelobe unidirectional patterns of cardioid shape; one is endfire and the other is backfire. Endfire patterns are obtained for leg lengths comparable with a wavelength, while backfire patterns are obtained when the antenna is small relative to a wavelength. In the former, the unidirectional antenna pattern for leg lengths of $\\lambda$ and $\\lambda /4$ has a beamwidth of about $180\\deg$ and very high front-to-back ratio (FBR). When the antenna lengths change by several percent from the ideal lengths, the variation of the beamwidth is in the range of $40\\deg$ and the FBR is in the range of about 5 (14 dB) to infinity. In the latter, for the rectangular antenna with a leg length of $\\lambda /10$ , the pattern in a plane perpendicular to the antenna has a beamwidth of $160\\deg$ and the pattern in a plane including the antenna has the beamwidth of $124\\deg$ . When the antenna lengths vary by about $\\pm30$ percent, the variation of the beamwidth is in the range of $30\\deg$ and the variation of the sidelobe level is about 4 dB. Although we used a suitable resistance instead of the matching impedance, the experimental results were almost coincidental with the theoretical patterns.