A wideband miniaturized 3 dB hybrid coupler for passive beam switching application

This paper proposes a wideband miniaturized 3 dB 90° hybrid coupler for passive beam switching application. The hybrid coupler is usually employed in an antenna array feed network in a butler matrix. For ease of fabrication and measurement, the operating frequency of the hybrid 90° coupler is designed from 700–960 MHz. Hence, an operating bandwidth of around 30% is achieved at the center frequency of 830 MHz. A size reduction of 83% is accomplished along with a fractional bandwidth of 30% by carefully adopting a meander structure with optimized spacing to enhance the capacitance within the structure. The proposed design is fabricated on Rogers 4360 substrate and measured results of the prototype show good agreement with simulated results.