Planar monopole antenna with Archimedean spiral slot for WiFi/Bluetooth and LTE applications

This paper presents a novel miniaturised microstrip-fed planar monopole antenna with Archimedean spiral slot to cover WiFi, Bluetooth and LTE standards. The base of the proposed antenna is a circular patch that operates in high frequency range, targeting compact circuit dimension. To create a multi-band antenna, Archimedean spiral slots, acting as resonance paths, have been integrated with the circular patch antenna. Analysis of the current distribution on the antenna reveals that at low frequencies the additional of the slots create new circular current paths, which form a wideband low-frequency response. Different shapes of Archimedean spiral slots have been investigated and compared. The miniaturised and optimised antenna exhibits a bandwidth of 2.2GHz to 2.9GHz to cover WiFi, Bluetooth (2.45GHz) and LTE (2.6GHz) mobile applications. The proposed antenna achieves low return loss, large gain, high efficiency and stable omnidirectional radiation pattern across all the relevant bands. The antenna is implemented and fabricated on an FR4 substrate. Reflection coefficient measurement results closely correlate with those obtained during design simulations. The presented antenna can be particularly applied to commercial multiband communication systems.