Bidirectional higher-order-mode slot antennas with sidelobe suppression

In this paper, three higher-order-mode slot antennas with high gain and bidirectional radiation characteristics are proposed. Each proposed antenna consists of a folded slot fed by a microstrip line. One antenna operates in the fourth-order resonant mode, whereas the other two operate in the fifth-order resonant mode. In higher-order resonant modes, slot antennas exhibit reversed electric fields, and the equivalent magnetic currents are generated in opposite directions. To suppress the sidelobes, folded slot sections are introduced into regions where the electric field is reversed. The radiation fields from these folded sections undergo destructive interference. This approach effectively suppresses sidelobes and reshapes the radiation pattern. For validation, prototypes of the three antennas were fabricated and measured. The measured results are in excellent agreement with the simulations, verifying the performance of the proposed designs. The measurements show that all three proposed slot antennas achieve stable bidirectional radiation and relatively high realized gains. The peak realized gains are 6.22 dBi, 8.55 dBi, and 6.53 dBi, respectively. The proposed slot antennas hold significant promise for applications in modern wireless communication systems.