High-Sensitivity Plantar Pressure Antenna Sensor Based on EBG Array for Gait Monitoring

Prolonged use of electronic devices, especially with incorrect sitting and posture, may cause changes in spinal shape. These issues can affect the distribution of pressure on the soles of the feet. As postural diseases continue to rise in prevalence, wearable wireless plantar pressure monitoring is essential. This article proposed a wearable plantar pressure antenna sensor based on electromagnetic bandgap (EBG) array operating in the 2.45-GHz industrial, scientific, and medical (ISM) band. To measure the pressure, the antenna sensor adopts a dual-substrate structure whose gap is filled with foam. Applying pressure to the antenna will cause the gap to shrink, resulting in shifts of the antenna's resonant frequency. By remotely reading the resonant frequency, wireless monitoring of plantar pressure can be achieved. The sensitivity of the antenna sensor to pressure is 1.06 MHz/N. In the two separate h ranges of 4.5-3.25 mm and 3-1.5 mm, the 2x2 EBG array can increase the sensitivity of the antenna sensor by 35.4% and 39.3%, respectively. In addition, the EBG array can also reduce the specific absorption rate (SAR) of the antenna by approximately 95% and increase the gain from -0.8 to 6.6 dB. The simulated and measured results of the antenna sensor produced a good agreement.