Steerable miniaturised printed quadrifilar helical array antenna using digital phase shifters for BGAN/GPS applications

A novel electronically steerable phased array antenna is developed for global positioning system/broadband global area network (GPS/BGAN) navigation applications. The array is composed of 2 × 2 printed quadrifilar helical antennas (PQHAs) integrated with digital phase shifters for beam steering over the transmit/receive bands. The feed network of each PQHA is based on a sequential rotation to achieve wideband circular polarisation (CP). An elegant control network with the embedded microcontroller is designed to provide driving bits to the phase shifters with reduced phase error. The meandered line design maintains high-performance CP radiation up to ±60° off-axis, within 1525 to 1660 MHz, and its size is 44% of the design with straight lines. The array gain is positive over 1450-1800 MHz beyond the BGAN band, with better than 13 dB return loss and <;2.2 dB axial ratio. The measured broadside gain of the array exceeds 8.5 dBi at 1600 MHz, and has a wide beam steering of ~±80° over the BGAN band. The developed antenna represents a significant technical advance to the design and manufacturing of PQHA array, it has a compact size, low cost and lightweight with a relatively large bandwidth and almost hemispherical coverage with excellent right-hand circularly polarized radiation.