DUAL-BAND CIRCULARLY-POLARIZED MICROSTRIP ANTENNAS WITH A SINGLE FEED

The authors present a novel technique for obtaining circularly polaris ed (CP) dual frequency operation by using two spur-line band-stop filt ers within the perimeter of a microchip patch antenna with optimum fee d point location and aspect ratio. This circularly polarised dual freq uency operation can be obtained without increasing either the size or the thickness of the patch. Furthermore, through several experiments t he authors also demonstrate that the location of the feed point establ ishes and controls a trade-off between axial ratio and impedance bandw idth.