Compact omnidirectional circularly polarized antenna based on twin helix structure
A compact omnidirectional circularly polarized antenna based on twin helix normal-mode was proposed to solve the problem of the asymmetry radiation patterns caused by hybrid normal-mode helical antenna. The antenna was mainly composed of two different-sized helices, two pairs of short metal bars that connecting different-sized helices, and a feed balun. The large and small helices were mainly responsible for the horizontal and vertical polarizations, respectively, thus achieving omnidirectional circular polarization radiation. Compared with the single helix normal-mode antenna, the structure of the twin-helical antenna was more symmetrical, and more uniform omnidirectional radiation pattern was enabled. Additionally, two helices were cascaded using two pairs of short metal bars, making the antenna structure more compact with a lateral dimension of only 0. 15λ. The results show that the antenna has a simulated axial ratio bandwidth of 2. 29-2. 49 GHz, an omnidirectional gain range of 1. 2-2. 2 dBic, and good omnidirectional circular polarization. The antenna was fabricated using metal 3D printing technology. The measured results are in good agreement with the simulation. The measured axial ratio bandwidth is 2. 27-2. 47 GHz, with a maximum gain of 2. 08 dBic. The axial ratio of the horizontal plane is below 3 dB, making it suitable for indoor IoT and other application scenarios.
万方数据
维普
