A Compact Dual-band Hat-Shaped Antenna with Band-Specific Behavior Using Harmonic Mixer for Passive Neural Monitoring

This work proposes a hat-shaped dual-band antenna with band-specific behavior using a harmonic mixer for the passive wireless neural monitoring system. The antenna is designed to work in coherence with a harmonic mixer of 2nd order. The antenna covers a volume of 16 x 16 x 1.6 mm3. The performance of the antenna is found to be satisfactory by conducting experiments using both homogeneous and heterogeneous media mimicking human tissue after covering it with a biocompatible PDMS layer. The lower and higher resonant bands extend from 3.75 to 3.9 GHz and 7.05 to 8.2 GHz, respectively, supporting communication at high data rates up to 20 Mbps. A directive gain of 1.29 dB in the lower band and 1.39 dB in the higher band makes it a good choice for implantable medical devices. A six-layer head model was considered for SAR evaluation with a penetration depth of 10 mm for safe operation as per IEEE C95.1-1999 standard. Based on this simulation, the maximum input power that can be fed to the antenna for safe operation is found to be 8.46 mW. The link budget analysis reveals that a satisfactory communication link may potentially be established up to a distance of 7 and 1.5 m between implantable and interrogator antennae with corresponding data rates of 1 Mbps and 20 Mbps, respectively.