Tri-Frequency Wearable Antenna Loaded with Artificial Magnetic Conductors

ObjectiveThe rapid advancement of 5G communication technology has expanded the use of antennas in aviation, radar, medical, and other wireless systems. Wearable antennas have gained attention because of their conformability. Loading an Artificial Magnetic Conductor (AMC) is an effective way to enhance wearable antenna performance. This method increases gain, improves the Front-to-Back Ratio (FBR), and provides radiation isolation between the antenna and the human body. This study presents a tri-band wearable antenna loaded with an AMC for the ISM band and 5G frequency bands.MethodsA trident-structured tri-band monopole antenna operating at 2.5 GHz, 3.5 GHz, and 5.8 GHz is designed together with a ring-shaped tri-band AMC tuned to the same frequency bands. Both structures use semi-flexible Rogers 4003 substrate. A 4×5 AMC array is placed on the back of the antenna to form a wearable integrated antenna. Simulation, physical measurement, and human safety assessment are performed.Results and DiscussionsThe integrated antenna shows simulated operating bands of 2.40$ \sim $2.50 GHz, 3.15$ \sim $3.80 GHz, and 5.56$ \sim $6.02 GHz, and measured bands of 2.38$ \sim $2.52 GHz, 3.30$ \sim $3.86 GHz, and 5.54$ \sim $7.86 GHz (Fig. 4). These bands cover the ISM scientific band (2.40$ \sim $2.4835 GHz), the 5G-n78 band (3.3$ \sim $3.8 GHz), and the 5G-WiFi 5.8 GHz band (5.725$ \sim $5.875 GHz). Measured gains at 2.5 GHz, 3.5 GHz, and 5.8 GHz increase by 5.3 dB, 4.6 dB, and 2.2 dB compared with the unloaded state (Fig. 15). The FBR values reach 20.8 dB, 18.0 dB, and 18.8 dB, corresponding to improvements of 19.8 dB, 16.7 dB, and 12.4 dB relative to the unloaded AMC (Table 4). The AMC reflector reduces the Specific Absorption Rate (SAR), and all integrated antennas show SAR values below 0.025 W/kg/g (Table 6), well below the FCC and ETSI limits. Performance is also measured when the antenna is placed on the chest, back, and thigh (Fig. 16), confirming safe and flexible on-body use.ConclusionsA tri-band wearable antenna incorporating an AMC array is developed using semi-flexible Rogers 4003 substrate. With a 4×5 AMC array integrated behind the antenna, the measured operating bands cover the ISM scientific band (2.40$ \sim $2.483 5 GHz), the 5G-n78 band (3.3$ \sim $3.8 GHz), and the 5G-WiFi 5.8 GHz band (5.725$ \sim $5.875 GHz). The results confirm high gain, high FBR, and stable wearable performance suitable for human-worn devices.