An On-Film AMC Antenna Insert-Molded in Earbuds with Enhancement in In-Ear and In Situ Received-Signal Sensing

Area of Science:

• Electromagnetics
• Wireless Communication
• Materials Science

Background:

• Earbud antenna design faces challenges due to size constraints, curved surfaces, and proximity to metallic components.
• Conventional antenna techniques are often thick, costly, and susceptible to performance degradation from human tissue.
• Existing methods struggle with impedance matching and radiation efficiency in compact wireless devices.

Purpose of the Study:

• To propose a novel thin and flexible antenna for earbuds.
• To enhance wireless signal-sensing capability using a film-based artificial magnetic conductor (AMC) structure.
• To overcome limitations of conventional antennas in small, curved wireless devices.

Main Methods:

• Designed and fabricated a metal pattern on a film antenna with an additional film layer as the AMC.
• Embedded the antenna in earbud mockups for 2.4 GHz Bluetooth RF link testing.
• Verified antenna functions through RF and antenna measurements, including tests with an ear phantom and a realistic sensing environment.

Main Results:

• Achieved 10 dB improvement in input reflection coefficient and 9% better antenna efficiency compared to other methods.
• Demonstrated robustness against human tissue interference, crucial for wearable devices.
• Observed a 20-30 dB enhancement in Received Signal Strength Indicator (RSSI) in realistic sensing scenarios.

Conclusions:

• The on-film AMC antenna (OFAA) effectively mitigates problems associated with antenna integration in small, curved wireless devices.
• OFAA offers superior impedance matching and radiation performance over conventional schemes.
• The proposed antenna design provides significant improvements in wireless performance and reliability for earbud applications.