A Miniaturized Wideband 3 dB Rat-Race Coupler Utilizing Meander Lines

This paper proposes a wideband miniaturized 3 dB 180° rat-race coupler. For ease of fabrication and measurement, the operating frequency of the 180° 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 95% is accomplished along with a fractional bandwidth of 30%. A meander line configuration is adopted and gaps between the lines are optimized to enhance the capacitance of the structure. The proposed design is fabricated on Rogers 4360 substrate and measured results of the prototype show good agreement with simulated results.