Planar Quarter-Wavelength Patch Antenna Array Integrated with Capacitor-Based Butler Matrix for Compact Switched-Beam Systems

This work presents the design of a compact switched-beam system (SBS) for advanced wireless communication networks. To achieve a compact design, a capacitor-based Butler matrix (BM) and quarter-wavelength patch antennas arranged in a planar array are selected as beamforming network and antenna elements. While to gain a reduced size, a two-layer design technique is adopted. Hence, a compact SBS with circuit dimensions of 0.44λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>×0.44λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> can be achieved. When the input ports are excited, four radiated beams are steered at 15° and ±45° at the frequency of 2.4 GHz. The proposed SBS ±has a 280 MHz (11.67%) 10 dB reflection coefficient bandwidth from the frequency of 2.26 GHz to 2.54 GHz.