A compact LTE band antenna with defected ground structure for IoT application

A compact antenna based on tight coupling and defected ground structure (DGS) is proposed in this research for Narrowband Internet of Things (NB-IoT) applications. The antenna features a metallic coating printed on an FR4 substrate, with a geometry size of 20 × 46 mm2 (0.05λ × 0.12λ) that operates in the low-frequency band from 680 MHz to 920 MHz and a high-frequency band from 1660 MHz to 3130 MHz. A novel approach using metallic layers on both sides of the substrate with tight coupling is introduced to achieve dual-band radiation. A bent radiation arm is employed, which lowers its natural resonance frequency to the extent of the working frequency band. Additionally, a unique DGS is integrated into the low-frequency IoT antenna and is tightly coupled with the high-frequency antenna to extend the working bands.