In this article, a low-cost double-layer microstrip structure with a gap space between the two substrate layers is used to develop a microstrip coupled-line directional coupler with high directivity. The proposed design shows a high directivity (more than 20 dB) over a wide frequency bandwidth (more than 2 GHz). The double-layer directional coupler, designed on FR4 substrate material at 2.4 GHz provides more than 30 dB isolation. The simulation and measurement results are in good agreement. By applying a simple and low-cost fabrication process and design, the directivity of the directional coupler is enhanced by more than 10 dB compared with a microstrip structure.