Broadband printed ring-slot array with circular polarisation

[[abstract]]A novel design of a printed ring-slot antenna with circular polarisation (CP) is first proposed. The CP radiation of the slot antenna is achieved by a series microstrip-line feed configuration. Using the single CP slot antenna as an array element, the 1 2 and 2 2 slot arrays are constructed and measured. To obtain wider CP bandwidth, phase sequential rotation technique is applied to the feed network of these printed slot arrays. The experimental results show that the 2 2 slot array antenna is capable of 15% bandwidth for an axial ratio of less than 3 dB