HHO-Optimized Dual-Band Patch Antenna for 5G Wireless Systems

Sub-6 GHz$\mathbf{5 G}$wireless systems require antennas that are compact, economical, and efficient, while remaining easy to integrate into user equipment and small-cell platforms. Dualband microstrip patch radiators are well suited for this role, yet their design must balance footprint, impedance bandwidth, and radiation characteristics, particularly when realized on lossy substrates such as FR-4. Many existing designs rely on manual parameter sweeps or conventional metaheuristic algorithms, which often converge slowly, favour larger electrical dimensions, and provide only moderate bandwidth, especially when dualband performance is considered. In addition, several reported optimization studies concentrate on a single operating band or do not explicitly improve both impedance matching and gain at the two resonant frequencies. This work introduces an Improved Harris Hawks Optimization (HHO) scheme for the synthesis of a dual-band microstrip patch antenna designed to operate at 3.50 GHz and 4.90 GHz on a$30 \times 30 ~\text{mm}^{2}$FR-4 substrate. The optimizer adjusts six key geometrical variables associated with the patch, slots, and parasitic stubs using a dual-frequency fitness function that minimizes the combined reflection coefficient at the two target bands. A large set of candidate geometries is evaluated through full-wave electromagnetic simulations across the sub- 6 GHz region, which effectively generates a design dataset capturing the nonlinear relationship between structural parameters and antenna responses. This dataset serves to benchmark the Improved HHO against recent nature-inspired optimizers, including SMA, AO, MPA, and GBO, under identical stopping conditions. The optimized antenna achieves$S_{11}$levels below$-24 \mathbf{~ d B}$, with$-10 \mathbf{~ d B}$bandwidths of$\mathbf{1 2. 0 \%}$and 7.3%, realized gains of 5.12 dBi and 6.05 dBi, and radiation efficiencies above 83 % in both bands. These results indicate that the Improved HHO framework yields a compact, high-performance dual-band antenna suitable for 5 G applications and can be adapted to the design of more complex multi-band or array configurations.