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 18° 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 45° linear polarisation. The resulting array can operate over the personal communication network (PCN) through Universal Mobile Telecommunication System (UMTS) frequency bands, from 1.7 GHz to 2.2 GHz