In near field communication (NFC), the operational range is typically constrained by the antenna dimensions and coil design. This paper introduces an innovative dual-coil NFC antenna system designed to increase this range to ensure more robust communication over increased distances and for wearable sensors applications. For the purpose, two in-phase circular coils are positioned on opposite sides of the same substrate, connected in series through appropriate via hole. This arrangement effectively increases both the coil length and turn count saving the substrate footprint. The outer diameter of each coil is 30mm and they are connected in series by a via hole in a 0.05mm thick commercial flexible substrate polyimide. The use of thin flexible substrate is aimed to ensure the availability of profile NFC antenna structure for various near field applications (cellular NFC-based communications and wearable real-time monitoring system of critical physiological parameters). Comprehensive design optimization has been conducted using ANSYS Electronics Desktop, accompanied by mutual positional (sliding and vertical) analyses to compare the field ranges achievable with dual-coil versus single-coil configurations.