A Multi-band Flexible Wearable Antenna Based on Split Ring Resonators

In this paper, a multi-band flexible wearable antenna based on split ring resonator is proposed based on the theory of microstrip antenna and the concept of metamaterial. In order to realize the flexible wearable and multi-band characteristics of the antenna, NF-30 flexible material is used as the substrate and the initial loop monopole antenna is deformed and designed. While introducing L-shaped branches on the ground plane, a coupling rectangular structure is introduced on the back of the antenna to enhance its radiation performance through proper adjustment of dimensions. The introduction of the split ring resonators alters the surface current distribution and radiation characteristics of the antenna. This has led to the emergence of two new operating frequency bands, reducing the antenna size and assisting in achieving miniaturization. The antenna can be operated in 6 bands: 2.07-2.65GHz, 3.71-3.98GHz, 4.21-4.33GHz, 5.48-6.33GHz, 7.58-8.19GHz and 8.63-9.67GHz. The bands above cover ISM, 3GPP, WI-MAX, Bluetooth, WIFI, WLAN (2.45GHz/5.8GHz), X-band, etc., and all have good impedance matching and radiation directionality. At the same time, the size of the antenna is only 50*50*1 mm³. In addition, the bending characteristics of the antenna and the influence of different parts of the human body on the antenna have been simulated and analyzed, and the return loss of the antenna and the conformal on the surface of human tissue are tested using a vector network analyzer. The test results are in good agreement with the simulation results, confirming its engineering significance and practicality.