A Compact Hepta-Band Mode-Composite Antenna for Sub (6, 28, and 38) GHz Applications

Abstract

A codesigned hepta-band antenna with a large frequency ratio is presented by using a mode-composite method. The method is based on an idea that apart from a quasi-TE10 mode transmitting in a substrate integrated waveguide (SIW) structure at millimeter-wave frequencies, additional radiation modes of the wire antennas can be excited simultaneously on the outer surface of a well-designed SIW structure at the microwave frequencies much lower than its cut-off frequency. In this design, a combination of a meander SIW section and an L-shaped SIW section that are connected with a metallic ground plane constructs the mode-composite structure. Two slot antenna arrays with a size of $2\times4$ are implemented in the SIW sections for the radiation in the 28 GHz and 38 GHz bands. Unidirectional features with low backward radiation can be achieved with the aid of parasitic dipole elements close to the slots. A T-shaped probe operating as a coupled feed is applied to excite five radiation modes existing on the outer surface of the mode-composite structure, which can cover five sub-6 GHz bands for the LTE and 5G mobile communications and the WLAN applications. Stable radiation characteristics are maintained at the microwave frequencies. The work paves a new means to design the compact multiband antenna with a large frequency ratio, which would be attractive for future portable devices operating in both microwave and millimeter-wave bands.