A Novel Low-Profile Monopole Antenna With Beam Switching Capabilities

In this paper, a new compact monopole surrounded by four switched parasitic elements having the ability to work in the directional (beam steering) and omnidirectional modes is presented. The antenna is designed to operate over a 6% bandwidth in the both modes. In the directional mode, the beam is steered in the azimuth plane and a front-to-back ratio greater than 10 dB is achieved over the bandwidth of interest. To steer the beam, the parasitic elements surrounding the driven element are connected and disconnected to the ground plane through switches. The performance of the antenna with both ideal and non-ideal switches is discussed based on the simulation and measurement results. To overcome the adverse effect of the non-ideal switch on the antenna radiation pattern and transmission coefficient, a transformer network is used in the switch circuit. It is shown that the accurate design of this transformer network can reduce the adverse effects significantly.