Experimental Characterization of Miniaturized Meander Line-Based 4x4 Butler Matrix

In this paper, an experimental characterization is performed to verify the concept of miniaturized 4x4 Butler matrix design using meander line technique. A meander line-based 4x4 Butler matrix prototype is designed and fabricated on an FR4 epoxy dielectric substrate with the thickness of 0.8 mm. Some key parameters of Butler matrix including the magnitude and phase responses are characterized and investigated through several measurements. The characterization results demonstrate that the meander line-based 4x4 Butler matrix takes the size of 57.5 mm by 136.4 mm shows good magnitude and phase performances. The measured -10 dB reflection coefficient fractional bandwidth of 16.25% could be attained at the frequency range of 2.15 GHz to 2.54 GHz. Meanwhile, at the operating frequency of 2.4 GHz the measured average phase difference between the adjacent output ports of 41.49 degrees was achieved. Here, the use of meander line technique could exhibit a size miniaturization of 34.29% to the footprint of conventional 4x4 Butler matrix.