Metamaterial conical beam antenna with dual band filtering response

A novel conical beam antenna with dual band filtering response is proposed by utilizing a metamaterial (MTM). The dual band filtering characteristics are inherently derived from the MTM and achieved through the coaxial feed and the probe coupling. Meanwhile, the conical beam is realized by using the cylindrical probe within the antenna aperture. Notably, the antenna exhibits remarkable compactness: firstly, the transverse size of the MTM is only ~ λ₁/7 or ~ λ₂/5, where λ₁ and λ₂ are the free space wavelength of central frequencies of the MTM's two modes, respectively. Secondly, extra filters are circumvented owing to the filtering performance of the MTM. To substantiate the aforementioned characteristics, the proposed MTM antenna is designed, fabricated, and measured. The measured results show a good agreement with the simulated ones, indicating that the proposed conical beam antenna has two operating bands around 3 GHz and 4.3 GHz, respectively. Additionally, the excellent filtering performance is confirmed by the out-of-band gain suppression level of ~ 30 dB outside the two passbands. It is feasible to use the MTM to develop the dual band filtering antenna with conical radiation.