Polarisation synthesis and beam tilting using a dual port circularly polarised travelling wave antenna array

The paper describes the application of a dual port annular sector radiating line antenna (ANSERLIN) element, designed to provide a radiation bandwidth of 35% (1.7 GHz to 2.4 GHz) for a VSWR <1.5. A four-element array consisting of such elements is shown to provide more than 18degrees of beam tilt without the need for phase shifters. A method to reduce on-axis cross-polarisation in the circularly polarised array is also presented. In addition, it is shown how the array can be used to produce slant 45degrees linear polarisation. The resulting array can operate over the personal communication network (PCN) through universal mobile telecommunication system (UNITS) frequency bands, from 1.7 GHz to 2.2 GHz.