Design and Analysis of Compact Self-Multiplexing Antenna Based on Half-Mode Substrate-Integrated Circular and Rectangular Cavities

This paper presents the design and analysis of a compact self-multiplexing antenna (SMA) for pentaband applications. The proposed antenna is built using half-mode (HM) substrate-integrated circular and rectangular cavities loaded with slots. The HM circular cavity is excited through three 50Ω microstrip lines, which facilitate three distinct frequency bands. In contrast, the HM rectangular cavity is activated using two 50Ω coaxial probes, yielding two different operating frequencies. Thus, the proposed SMA operates at 3.91 GHz (5 G band), 4.4 GHz (5 G band), 4.99 GHz (5 G band), 5.83 GHz (WLAN/WiMAX), and 6.59 GHz (Extended C -band). The radiation process, operating principle, and frequency tunability are explored in depth. The proposed SMA features a compact footprint area of 0.43 λg2 and attains an isolation level exceeding 24.5 dB. The antenna achieves realized gains of 3.46 dBi, 3.23 dBi, 3.44 dBi, 5.19 dBi, and 4.23 dBi, along with efficiencies exceeding 82%, 87%, 92%, 71%, and 90 % at frequencies of 3.91 GHz, 4.4 GHz, 4.99 GHz, 5.83 GHz, and 6.59 GHz, respectively.