Fluid-Based Reconfigurable Antenna for Frequency and Pattern Control in S-Band

초록

This paper presents a fluid-controlled reconfigurable antenna for S-band wireless applications. The antenna employs a monopole radiator on a partial ground plane optimized for 2.4 GHz operation with an omnidirectional radiation pattern. Two distilled-water fluidic channels are integrated into the ground plane to enable both frequency and pattern reconfiguration. Unlike conventional electronic tuning limited to discrete states, varying the fluid volume allows the resonant frequency to be tuned continuously and precisely from 2.02 GHz to 2.52 GHz. More importantly, asymmetric fluid filling enables pattern reconfiguration and beam steering; selectively injecting fluid into one channel focuses the radiated energy in the opposite direction, thereby achieving directional steering along with gain enhancement. Furthermore, by maintaining a constant total fluid volume and adjusting only the volume ratio between the channels, a bidirectional beam steering of up to +/- 4 degrees is successfully realized while completely preserving a stable center frequency. Simulated and measured results demonstrate consistent impedance matching, a peak gain of 4.28 dBi, and radiation efficiency exceeding 98% across all configurations. The high efficiency is attributed to the low-loss dielectric nature of distilled water, which minimizes conductive and dielectric losses during reconfiguration. These characteristics, particularly the independent, continuous control of frequency and pattern alongside high efficiency, make the proposed antenna a strong candidate for adaptive S-band systems such as IoT devices, sensor networks, and software-defined radios.

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