Broadband circularly polarized antenna with a T-type fractal boundary wide-slot and a L-shaped strip

A novel T-type fractal boundary wide-slot broadband circularly polarized printed antenna for L-band applications is proposed. The T-type fractal boundary wide-slot is fed by a L-shaped metal microstrip, and the broadband CP is obtained by co-acting of the L-shaped metal microstrip and the T-type fractal boundary. This antenna is designed by simulations and experiments. And results show that the impedance bandwidth (with the return loss below -10dB from 1.18GHz to 1.65GHz) is 33.2%. The proposed antenna provides the CP gain of 2.3-3.4dBi and the axial ratio of less than 2.5dB within the impedance bandwidth, whilst it radiates in two directions with right-hand/left-hand CP. If adding a metal shield at one side of the antenna, this broadband CP antenna can be a directional radiation one. By simulations and experiments, the size and position of the reflection shield which make the antenna achieve miniaturization are obtained. Then the proposed directional antenna has a CP gain of as large as 5.3dBi. The designed antenna proposes T-type fractal boundary for the first time, which improves the axial ratio bandwidth significantly, and realizes the function of broadband CP. The proposed antenna covers satellites communication band of multi-mode with high gain, and can be applied broadly.