Circularly-Polarized Focused Microstrip Antenna Arrays

This letter presents two different designs of circularly-polarized focused microstrip antenna arrays working at 2.45 GHz. The two antenna arrays are designed by the method of maximizing the power transmission efficiency between an antenna array and a test (receiving) antenna. The procedure yields the optimized excitations for the antenna elements, which can then be realized by feeding networks. Both simulated and measured results are provided to demonstrate the focusing and the circular-polarization performances of the two designs.