Reconfigurable microstrip antenna with pattern and polarisation diversities

A microstrip antenna with the functions of switchable pattern and polarisation is presented. The antenna is composed of a square-ring radiating patch and four shorting walls. The shorting walls are connected to each edge of the square-ring patch through one pin diode. By controlling the states of the pin diodes, the square-ring microstrip antenna can radiate two complementary patterns (conical and broadside); moreover, dual orthogonal linear polarisations are provided for the broadside radiation. These diversity functions are operated at the same frequency band. An antenna prototype has been implemented and the results obtained are given.