Antenna design using speaker wire for a Bluetooth ear set

In this article, an antenna design using an audio wire is proposed for a compact Bluetooth ear set. The length of the audio wire is less than a quarter of a wavelength in Bluetooth ear sets. Therefore, an appropriate feed structure needs to be designed to utilize the wire as an antenna. The antenna has been tuned using an inductor and impedance matching is accomplished by a loop-type feeding structure with lumped capacitors. The feeding structure can be used to tune various lengths of the antenna. Full wave simulations are conducted to observe the effectiveness of the proposed technique. The measured and simulated bandwidths of the antenna are in good agreement. The measured bandwidth and average efficiency of the antenna were 116 MHz and 54.74%, whereas the average total isotropic sensitivity was 80.12 dBm that comply with the desired criteria for operation of the Bluetooth ear set.