A Compact-Size and High-Efficiency Cage Antenna for 2.4-GHz WLAN Access Points

In this communication, a compact-size and high-efficiency air cavity antenna with a cage-like structure is proposed for 2.4 GHz wireless local area networks (WLAN). The air cavity antenna is constructed with four sides of hybrid metallized vias, including sparsely arranged blind vias and tightly arranged shorting vias. First, the antenna size is significantly reduced by utilizing the shorting vias, which makes the antenna operate at the high-order TM<inline-formula> <tex-math notation="LaTeX">$_{\mathrm {1/2,1/2}}$ </tex-math></inline-formula> mode. Then, by loading the capacitive blind vias at the radiating apertures, the antenna size is further miniaturized. Notably, high radiation efficiency is obtained attributed to the lower dielectric loss of the air-medium structure. Finally, a prototype of the proposed cage antenna has been fabricated and tested with good agreement between simulated and measured results. In such a compact size of <inline-formula> <tex-math notation="LaTeX">$0.128\lambda _{0} \times 0.128 \lambda _{0} \times 0.10 \lambda _{0}$ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the center frequency), the measured total efficiency over 90% is achieved in the WLAN band by the cage structure. Compared with the existing 2.4 GHz antennas, the proposed one is with the ascendency of compact size and high radiating efficiency for WLAN applications.