A Chip Antenna for Bluetooth Earphones with Cross-Head Interference Tested from Received-Signal Sensing

Area of Science:

• Electrical Engineering
• Electromagnetics
• Materials Science

Background:

• Bluetooth (BLT) earphones require compact, efficient antennas for reliable wireless connectivity.
• Existing antenna solutions may face challenges with miniaturization and interference in earphone applications.

Purpose of the Study:

• To present a novel, compact metamaterial chip antenna for BLT earphones.
• To evaluate the antenna's performance in a realistic earphone use-case, including head-related interference.

Main Methods:

• Design and simulation of a sub-wavelength (<λ/8) metamaterial chip antenna.
• Integration of the antenna onto a printed circuit board (PCB) within earphone enclosure constraints.
• Electromagnetic simulation and experimental verification, including measurements with a human head-ear phantom.

Main Results:

• The proposed chip antenna measures 4.9 × 13.0 × 2.0 mm³, fitting within BLT earphone enclosures.
• Antenna resonance (S11 < −10 dB) is maintained when mounted on a realistic PCB.
• Received signal strength indications of -67.5 dBm and -70 dBm were achieved without and with the head-ear phantom, respectively, exceeding the detection limit of -120 dBm.

Conclusions:

• The novel metamaterial chip antenna offers a viable solution for robust wireless connectivity in BLT earphones.
• The antenna demonstrates invulnerability to cross-head interference, ensuring reliable communication between paired earphones.
• The compact size and performance characteristics make it suitable for integration into miniaturized earphone designs.