Coplanar waveguide-fed ultra wideband planar monopole antenna optimisation

This study presents a coplanar waveguide (CPW)-fed planar monopole antenna optimised to achieve low return loss and good transient behaviour for ultra wideband (UWB) applications. Optimisation is performed by maximising the temporal correlation between radiated electric field intensity at different planes and the antenna input waveform. Two different antennas are designed. In the first antenna, only the E-plane correlation factor pattern is considered for optimisation. In the second antenna, the correlation factor patterns of both E-plane and H-plane are considered for optimisation. This entails waveform consistency in more directions. We employ a hybrid optimisation procedure that involves genetic algorithms as a global optimiser, and pattern search method as a local optimiser, using the commercially available CST Microwave Studio software. Simulation results of the second optimised antenna show that the correlation factor for the two-antenna system in the side-by-side and face-to-face scenarios are 0.824 and 0.822, respectively. Furthermore, experimental results demonstrate that the second optimised antenna has a voltage standing wave ratio (VSWR) less than 1.5 in the 2.6-13 GHz frequency band. These results indicate that the optimised antenna has excellent impedance matching and reduced time-domain distortion in comparison with similar existing antennas.