A planar dual fed UWB monopole antenna with polarization diversity for cognitive radio sensing

A dual fed compact ultra-wideband microstrip monopole antenna with reconfigurable polarisation capability is presented. By having two feeds to excite the patch from two different locations, the polarisation can be changed from vertical to horizontal. The level of coupling between the input ports can be significantly reduced if the two 50 Ω feed lines are from different transmission line technology (e.g. One is coplanar waveguide -CPW and the other is Microstrip -MS). The RF switches used for simulating the switching mechanism are currently copper bridges, for proof of concept. Simulation results of refelction coefficient for each port, transmission coefficient between the two ports, radiation patterns, and peak gain are all presented featuring very good performance. The proposed antenna can be very helpful in cognitive radio (CR) systems by decreasing the potential for signals to be undetected due to polarisation blindness when sensing the surrounding RF environment.