Differential-fed UWB microstrip antenna with improved radiation patterns

A differential-fed microstrip antenna, which is characterised with an ultra-wideband (UWB) of 120% (3-12 GHz), improved radiation patterns, stable gains and compact size, is proposed. Two symmetrical trapezoid-shaped slots and four triangle-cut corners on the ground are used to improve the impedance matching over the UWB frequency band. To clarify the improved radiation characteristics, the simulated 3D radiation patterns of the proposed antenna are also shown. The measured results show that, in the entire frequency band, the designed antenna exhibits a stable radiation pattern and the gain variation is <; 2.5 dB. Furthermore, the polarisation purity is increased compared with the conventional ones, especially in the high-frequency band.