A 3-dB quadrature coupler which combines the advantages of broadside-coupling and coplanar waveguide structure suitable for a single-layer printed circuit board (PCB) circuit design is proposed. Compared to the recently published broadsidecoupled structures, the proposed coupler can easily be realized in a single-layer substrate by using PCB manufacturing processes to eliminate the effects of uncertain factors from a multi-layer substrate. With the operation bandwidth ranging from 2.1 to 2.7 GHz, the measured return loss and isolation are all better than 19 dB, and the insertion losses and relative phase difference between the direct and coupled ports are at 3.2±0.1 dB and 90±0.6°, respectively. The dimension of the coupler is 2.1 cm × 1.9 cm.
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