Design of Tree-shaped Decoupling Structure Based on Generative Non-adversarial Networks for Antennas in IoT Applications

The miniaturization of Internet of Things (IoT) devices requires multiple antennas in a limited space, which can lead to strong mutual coupling. Traditional decoupling methods usually rely on experience-driven design or application-specific structures, which limits their effectiveness in different antenna configurations. In this article, a generalized tree-shaped structure with high flexibility is proposed for antenna decoupling in terminal devices in Internet of Things (IoT) systems. The specific geometries of the decoupling structure are optimized using generative non-adversarial networks (GNAN) according to different requirements. As the prior knowledge, quarter-wavelength branches are initialized to improve the optimization efficiency. To meet the design requirements with a smaller dataset, an evolutionary method is employed. At the same time, attention mechanism is introduced into the discriminator network, which largely improves the training speed. Following the proposed method, different tree-shaped decoupling structures are optimized and applied to three different multiple-input multiple-output (MIMO) antenna systems, including an ultra-wide band (UWB) antenna array, a narrow-band microstrip patch antenna array and an antenna array with different antenna pairs. As a result, isolations have been proved by 20 dB, 53 dB, and 45 dB, respectively. Hence, the flexible tree-shaped structure is validated to be generally effective for closely placed MIMO antennas in IoT systems. Prototypes of the transparent UWB antenna array have been fabricated and measured, with the measurement results agreeing well with the simulated ones.