4.3 Design of a PIFA for a GNSS Terminal Antenna

CP antennas have been extensively studied recently for GNSS applications. The general limitations of the CP patch antennas are the achievable impedance and axial ratio (AR) bandwidths. Traditionally, the 3 dB AR bandwidth is typically less than 10% for the single-feed cases [19, 20]. PIFAs (Planar Inverted-F Antennas) [21–23] have been widely used in wireless communications, as they have wideband characteristics, good radiation patterns, simple structures and easy integration with other active devices, but they are usually used for linear polarisation. Very few designs are available in the open literature for achieving CP radiation using PIFA structures.

A novel broadband single-feed printed PIFA with broadband circular polarisation is described in [24], consisting of a square ground with a cross-shaped branch at its corner and a modified PIFA structure. By introducing a protruding cross at the ground, wideband circular polarisation is generated, and the modified PIFA structure gives the antenna a broad impedance bandwidth. The antenna has a very compact structure with a dimension of 51 × 13 mm2 on the substrate, which is suitable for handheld GNSS terminal application.