Pattern Diversity Antenna With Odd and Even Modes for Intelligent Wi-Fi Applications

A compact planar pattern diversity antenna with an omnidirectional pattern and four unidirectional beams is proposed. The antenna combines a center-fed polarization diversity patch and a zeroth-order resonant mushroom structure, which are equivalent to a reconfigurable odd mode and a vertically polarized even mode, respectively. The quasi-endfire patterns are generated by the superposition of the odd and even modes with in-phase excitations controlled by a single port and four p-i-n diodes instead of multiple ports and phase shifters. By introducing four diodes, the polarization of the circular patch antenna is controlled in four states, and the diversity beams covering the whole azimuthal plane in four directions are obtained. The antenna with a low profile and compact size of π × 0.29λ ₀ × 0.29λ ₀ × 0.033λ ₀ (λ ₀ represents the free-space wavelength at 2.45 GHz) was fabricated. Measured results show good agreement with the simulation. The impendence bandwidth of four directional patterns achieves 7.3% [(2.39 to 2.57) GHz], which covers the wireless local area network (WLAN) band [(2.40 to 2.48) GHz], and the gain of the directional radiation is greater than 3.60 dBi in the operating bandwidth. The proposed antenna is well suitable for intelligent Wi-Fi systems.