Dual frequency planar circularly polarized antenna at S and L bands
Currently, there are many personal mobile satellite (MSS) systems in various stages of concept, design, and operation. One of them is the low earth orbit system (LEO), which requires two frequency operation at S and L band. At present, a planar dual-band antenna at S and L bands has been developed by using a circular patch and a short circuited ring in a stacked configuration. However, a single layer antenna would have the desirable feature of easy fabrication and low cost. In 1995, Salvador et al. developed a dual-band circularly polarized antenna based on the cross patch antenna by adding half-wavelength square patches in the four empty spaces among the arms of the cross. The dual-band antenna has compact structure and operates at two frequencies with a ratio in the range 2.9-3.2. However, in some cases such as handset antenna for mobile LEO satellite system terminals, a dual-band circularly polarized antenna with a frequency ratio of -1.5 is required. In this paper, a single layer dual-band antenna at S and L band has been developed by use a cross patch with four quarter wavelength patches printed in the empty spaces among the arms of the cross. The dual-band antenna, which we have designed, has less mutual coupling between the two bands than Salvador's antenna due to the using of quarter wavelength patches. Parameters of the antenna, including input return loss, mutual coupling, bandwidth are presented and discussed.