Generation of OAM Radio Waves Using Circular Filter-Antenna Array

A circular orbital-angular-momentum (OAM) filter-antenna array at radio frequency is presented in this paper. Each element of the proposed antenna array is a three-pole filter antenna which is realized by replacing the third resonator of the filter with a Γ-shaped antenna. A l = + 1 feeding network is designed so that the proposed filter-antenna can generate l = + 1 beam at 2.45 GHz. The simulated results show that the proposed OAM filter-antenna array has a flat antenna gain in the passband, about 5.5dB from 2.23GHz to 2.62GHz, while in the stopband, the gain is less than -15dB, which shows a high suppression. Moreover, the 3-D gain-pattern and the spatial phase distribution demonstrate the proposed design can generate vortex beam with filtering characteristics. The proposed design can not only increases the channel capacity but can also reduces abnormal frequency interference.