Flexible 2.4 GHz Node for Body Area Networks With a Compact High-Gain Planar Antenna

A flexible 2.4 GHz wireless sensor node with a bespoke single-layer monopole antenna, tuned for on-body operation for wearable applications, is presented. Multiple antenna design approaches for tuning on-body antennas have been investigated. The proposed antennas patch and meandered, designed for operation in the insole, exhibit a simulated realized gain of −3.98 and −1.97 dB, respectively. The antennas were fabricated on a 25 μm flexible polyimide substrate, exhibiting up to 16% lower insertion losses at 20 GHz than FR4 PCBs. The integrated node incorporates a commercial Bluetooth low energy system-on-chip and exhibits 9 dB higher measured gain than commercial modules with reference antenna design. Moreover, through functional radio test, it was confirmed that the designed node passes Bluetooth transmitter certification tests.