A compact 8-element antenna array for GPS digital beamforming

The low broadcast power of the GPS satellites makes signals particularly susceptible to interference and therefore GPS antennas with capability to mitigate interference are highly desirable [1]. One of the effective approaches against interference can be realised by the use of Controlled Radiation Pattern Antennas (CRPAs) [2]. Existing CRPA GPS arrays typically have a circular aperture with one reference element located at the centre and other auxiliary elements inscribe the circumference of the aperture. These auxiliary elements combine with the central element to form pattern nulls in the direction of interfering signals. These shaped patterns enhance the system robustness in the presence of strong radio frequency sources [3]. A key factor in the array performance is the number of auxiliary elements. More elements meant that a null can be steered in the direction of interference more precisely, thereby improving the overall signal-to-noise ratio (SNR). It also enables more flexibility in placing nulls on interfering sources [4]. For small platforms, the aperture available for the array is limited and therefore it is advantageous to design a compact array. In this paper, an 8-element antenna array for GPS digital beamforming has been proposed and developed.