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We propose an advanced monopole antenna to investigate non‐stationary outdoor wireless channel environments of 5G mobile communications. Our antenna has an omni‐directional beam pattern in the azimuth plane and a wide half‐power beamwidth (HPBW) in the elevation plane, respectively. To minimize blind angles along the axis of the monopole, we intentionally add a metallic annular ring around the monopole, which operates as a secondary source of our antenna. Then, the circumferential field from the secondary source appropriately interferes with the primary field from the monopole to widen the HPBW with a relatively high antenna gain in a far‐field region. An input signal is applied to a standard WR‐28 waveguide, and it is transferred to the monopole antenna through a coaxial waveguide. However, because impedance looking into the monopole and the waveguides are all different, we insert a mode converter between the rectangular and the coaxial waveguides. For better impedance matching, the coaxial waveguide is also used as an impedance transformer between the mode converter and the monopole antenna. Consequently, we can obtain the required omni‐directional radiation pattern with a wide HPBW and a high gain. All measurement data show good agreement with simulations, which proves the validity of our approach.

For the first time, this study demonstrates a reconfigurable antenna with electrical beamforming that is entirely integrated by semiconductor microfabrication technology. In this paper, a vertical structured array of solid‐state plasma which acts as a reconfigurable conducting wall to control the main beam direction of an antenna is proposed. In many conventional works, insufficient electrical conductivity of turned‐on plasma channels at the planar surface of PIN diodes causes an inherent large loss and low radiation efficiency of silicon‐based antennas. However, in this study, the overall performance of the antenna is notably enhanced by adopting the vertical plasma channels which solve the lower electrical conductivity problem of the surface‐type plasma structure. Accordingly, the proposed antenna achieves a high realized gain of more than 5 dBi over a frequency range of 27.5–29.6 GHz, even though it is comprised of lossy silicon with high permittivity. In addition, the low cost and electrically reconfigurable antenna, which benefits from the highly precise semiconductor fabrication process, is applicable to sub‐THz applications with a lightweight and compact sized feature. This work paves the way to make silicon antennas with commercial microfabrication technology a next‐generation antenna.

A reconfigurable antenna with electrical beamforming that is entirely integrated by semiconductor microfabrication technology is reported in article 2000257 by Seok Bong Hyun, Dongho Kim, Yang‐Kyu Choi and co‐workers. Their cover image shows a number of reconfigurable beamforming plasma antennas arrayed on a silicon wafer. Each antenna makes 4 azimuthal beamforming along with 4 directional V‐PINs.

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