Abstract: Objectives To address the fundamental trade-off in naval communication systems where a single antenna struggles to balance wide-band channel capacity with high-gain frequency selectivity, research has been conducted on bandwidth-reconfigurable FP antennas suitable for the complex electromagnetic environment of naval vessels. Methods Based on the Fabry-Perot resonator theory, an FP antenna structure with highly mechanically adjustable resonator height was constructed. The antenna performance was modeled and optimized using the HFSS finite element simulation software. Results Simulation and experimental results demonstrate that this antenna achieves S₁₁ < -15 dB in both shielded and radiated modes. In shielded mode, it exhibits a relative bandwidth of 2.6% with symmetrical E-plane and H-plane patterns. In radiated mode, the relative bandwidth increases to 4.5%, with side lobe levels approximately -12 dB. By adjusting the cavity height via a movable ground plane, stable switching between two operating modes is achieved: narrowband high reliability and wideband high throughput. Conclusions The proposed mechanically tuned FP antenna structure clarifies the regulatory patterns of cavity height on coupling mechanisms and bandwidth characteristics, providing an effective theoretical basis and technical approach for the application of adaptive antennas in complex electromagnetic environments.