Novel high‐isolation circuit for multiple antennas integrated in small IoT modules

Abstract

The increasing use of Wi‐Fi and Bluetooth in compact Internet of Things (IoT) modules leads to severe mutual coupling between coexisting antennas, resulting in interference and performance degradation. In this study, a novel antenna design methodology is developed based on characteristic mode analysis for small IoT modules. A decoupling loop structure is introduced to effectively suppress mutual coupling while maintaining compact size. The fabricated module achieves isolation levels better than −20 dB across the 2.4‐GHz band. The measured total radiation efficiencies are 59.2% and 61.3% for Wi‐Fi and 62.7% for Bluetooth at 2.4 GHz and 52.0% and 50.8% for Wi‐Fi at 5.5 GHz. Active performance evaluation shows an average total radiated power (TRP) exceeding 12.1 dBm at 2.4 GHz and 7.7 dBm at 5 GHz with corresponding total isotropic sensitivity (TIS) values of approximately −68 and −57 dBm. The average TRP and TIS outcomes for Bluetooth are better than 7.4 and −77.9 dBm, respectively. The results confirm the effectiveness of the proposed design, particularly when integrated into television environments.