Abstract:
Beam-steerable antennas play a crucial role in various standards and applications,
particularly gaining significance in millimeter-wave bands. Their adaptability to adjust the
radiation pattern direction, flexibility, reconfigurability, and operation across a broad frequency
range position them as an important component in diverse applications, such as 5G communication
systems, radar systems, satellite communication, and biomedical applications. Multiple
techniques, including mechanical and electronic beam steering, as well as the use of lenses,
reflectors, crystals, metamaterials, and beamforming circuits, are employed to achieve beam
steering, each with its unique advantages and disadvantages. Introducing a novel concept, this
thesis explores the utilization of fluidics in microwave circuits, specifically incorporating a liquid based reconfigurable beamforming circuit for beam steering. The proposed approach involves
designing a 4x4 Butler matrix and a 4-element patch antenna at a frequency of 2.0 GHz.
Reconfigurability is achieved by incorporating liquid (water in this case) through a PLA based
structure using the loading component method. Fifteen liquid channels, distributed on both upper
and lower sides, are filled in various combinations to manipulate the progressive phase shift of
Butler Matrix output ports. This results in achieving beam steering of 16 degrees at each port,
significantly enhancing spatial coverage to more than ±53 degrees over a hemispherical plane,
while maintaining a -10dB impedance bandwidth from 1.8 GHz to 2.2 GHz (400MHz). To validate
the proposed concept, two designs are fabricated: a 4x4 Butler matrix and a 4x4 Butler Matrix with
a 4-element patch antenna array. Comparisons between simulated and fabricated designs reveal
closely matched measured results with simulated data. Notably, the proposed approach
distinguishes itself from other reconfigurability methods by offering a low-profile, cost-effective,
and compact solution, making it highly suitable for applications in radar, wireless communication,
and other tunable devices in the S-band.
