Effects of cavity ground plane on UWB Archimedean spiral antenna

One of the important properties of Archimedean spiral antenna (ASA) is its unidirectional radiation pattern properties. This property is mainly achieved by using ground plane placed behind the spiral antenna. This paper presents the effects of air cavity ground plane on the design of two arms ASA. The GP is placed at λ/4 for the selected design frequencies. The GP deteriorates the antenna's performance as it is placed near to the antenna. The simulated results of return loss, gain, axial ratio, radiation pattern and radiation efficiency are obtained by using commercial electromagnetic simulator, CST..