Vertical-Polarized Tri-Band Monopolar Antenna With Controllable and Stackable Notched Frequencies

A new scheme of stacking tri-notched frequencies is introduced to develop a tri-band omnidirectional antenna with vertical polarization. In this scheme, a ground plane and a three-sector M-shaped sheet with a top-loaded patch are excited by a 50 Ω coaxial cable, aiming to achieve excellent impedance and vertical-polarized omnidirectional radiation performance within a broad bandwidth. Subsequently, a three-sector fan-shaped patch with three metal holes, three I-shaped slots and three 1.0λ resonant rings are successively introduced to create two stopbands at 2.75 GHz to 3.25 GHz and 4.25 GHz to 4.37 GHz, thereby dividing the ultra-broad band into three desired bands. In our design, the notched bands can be controlled by altering the sizes of the fan-shaped patch, metal hole, I-shaped slot, and resonant ring. The test results indicate that the proposed antenna has three operating bands at 1.44 GHz to 2.76 GHz, 3.19 GHz to 4.36 GHz, and 4.50 GHz to 4.70 GHz. The tri-band antenna also has good omnidirectivity and a low profile of $0.049\lambda _{\mathrm{m}}$ ($\lambda _{\mathrm{m}}$ stands for the maximum wavelength in the operating band), indicating its suitability for indoor communication in the bands of FDD/DCS/PCS/UMTS, LTE, and 5G NR n77/partial n79.