Doughnut and Tilted Beam Generation Using a Single Printed Star Antenna

A novel printed star antenna is presented for generating both doughnut shaped and tilted beam radiation patterns. These patterns can be switched to scan the space in front of the antenna. The star is printed on finite-size stacked dielectric substrates backed by a finite size conducting ground plane. The radiation pattern depends on the feed position. The star antenna with a feeding point at the centre gives a doughnut pattern similar to that of a top loaded monopole antenna with a similar directivity of around 5 dBi. When the star is fed at any of its four corners, it has a tilted beam and depending on the star flare angle, it can provide a maximum directivity of 7.9 dBi. Hence, feeding the star at the four corners will generate four tilted beams in the four respective quadrants. Thus, by selecting an appropriate feed individually, a total of five distinct radiation patterns can be generated by just one single printed star antenna. A prototype star antenna with a flare angle of 10deg is fabricated. The characteristics of the antenna are predicted using electromagnetic modeling software and are verified by measurements using a multi-probe antenna test facility.