A novel circularly polarized filtering antenna with high out-of-band radiation rejection level

摘要

In this paper, a circularly polarized filtering antenna with high out-of-band radiation rejection level is proposed. The entire design consists of a patch and a filtering feeding network, which are connected by metallic pins. First, a high-selectivity filtering power divider is constructed utilizing two shunted bandpass filter. Next, a 90 degrees phase difference could be realized by adjusting the length of the two outputs of the power divider. The measured transmission coefficient of the feeding network is 6.3 dB at 2GHz. The measured axial ratio is below 3dB within the operating band of the proposed antenna, which represents the effectiveness of the proposed feeding network. In addition, the obvious radiation nulls can be found from the antenna measurement because of the transmission zeros introducing by the filtering power divider. The measured gain is 5.73dB at 2GHz and decreases dramatically in stopband. Specially, the measured gain is -30 and -41 dB at 1.95 and 2.06GHz. The proposed antenna has an excellent filtering characteristic compared with those without the filtering feeding network. To sum up, the proposed antenna and filtering power divider are promising in the modern wireless communication systems.