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This communication presents the design of a wideband circularly polarized (CP) antenna array based on sequential rotation (SR) technique that is excited by a substrate integrated coaxial line (SICL) with mature and stable processing technology for millimeter-wave (mm-wave) applications. Initially, the influence of the amplitude and phase errors of the feeding network on the axial ratio of the CP array is analyzed, and the detailed design scheme of the wideband CP array based on SR technology is summarized, which can be used to design SR CP array with wide bandwidth and high polarization purity. Then, an SICL-fed $4 \times 4$ CP array working in the mm-wave band that is composed of two substrate layers and a bonding film layer is designed. The radiation element is processed with a larger chamfering, which can realize elliptically polarized radiation in a broadband range, and the impedance bandwidth is significantly expanded relative to the working state of linearly polarized and CP, which has a significant impact on the final array working bandwidth enhancement. The feeding network and radiation elements are directly connected in the same plane. Finally, the proposed antenna is processed and measured to verify the theory and design scheme in this communication. Over the frequency range of 25.0–34.0 GHz, the measured 1.5 dB axial ratio bandwidth of the fabricated prototype is 30.5%, and the return losses are less than −10 dB. The maximum measured peak gain is 16.5 dBi. [ABSTRACT FROM AUTHOR]

This article presents a novel triband dual-polarized shared-aperture antenna with frequency-selective function for sub-6 GHz base station applications. The proposed antenna is composed of a dual-polarized square loop antenna with two parasitic loops for 2G/3G/4G (1710–2690 MHz) and a differentially fed dual-polarized planar antenna for 5G (3300–3600 and 4800–5000 MHz) base station applications. These two antennas are placed coaxially but different altitudes for saving the installation space. In order to achieve good individual performance for these two antennas in the same aperture without interference or blocking, the lower band (LB) antenna is designed as a frequency-selective surface (FSS) for the nether mid/upper bands (M/UBs) antenna. The measured results show that the proposed antenna achieves a high port isolation (>20 dB) between LB and M/UBs and a −10-dB impedance bandwidth of 50.4% (1.60–2.70 GHz), 14.9% (3.28–3.80 GHz), and 8.6% (4.75–5.18 GHz). To further validate the design concept, an antenna array composed of four LB elements and eight M/UBs elements with the corresponding spacing is fabricated and measured, which demonstrates the application of the triband shared-aperture antenna in array form. [ABSTRACT FROM AUTHOR]

This paper presents the design of dual circularly polarized (CP) series-fed arrays based on the sequential rotation (SR) technique with uniform radiation elements. The radiation elements and feeding network used in the array are uniform, which leads to the possibility of dual-CP radiation by series-fed SR arrays. Meanwhile, the elements radiate unequal powers due to this arrangement. The relationship between the axial ratio and four key parameters of the array is derived and thoroughly discussed. Good polarization purity and port isolation can be realized by optimizing these parameters. A dual-CP array working at 10 GHz is designed with the help of the analysis. The experimental results show that the proposed antenna has good properties. [ABSTRACT FROM AUTHOR]