A Compact UHF Antenna Based on Complementary Fractal Technique

A compact and wideband ultra-high-frequency antenna is developed in this paper. By applying the Minkowski fractal geometry into both the lateral boundaries of monopole and the upper boundary of ground plane and loading the asymmetric strips at the top of monopole simultaneously, the miniaturization is realized; by means of adjusting the fractal direction to produce a complementary structure and cutting the triangular notch on the ground plane, the impedance bandwidth is enhanced. The influences of critical parameters on the impedance bandwidth are determined through the sensitivity analysis. Furthermore, to validate the performance of the proposed antenna, the return loss, radiation patterns, transfer function, and fidelity factors are measured; the electrical dimension and ratio bandwidth are compared with those of the existing antennas. It shows that the antenna with size of 0.28\lambda _{L} \times 0.28\lambda _{L} can cover the frequency ranging from 700 MHz to 4.71 GHz and has an average gain of 3.93 dBi along with strong pulse handling capability. The results demonstrate the superiority of the complementary fractal technique.