Miniature Folded Patch GPS Antenna for Vehicle Communication Devices

A novel miniature folded square patch antenna is proposed and developed for Global Positioning System (GPS) receivers. Four different lengths of meander strips connected to the four edges of the square patch of a single coaxial-feed square patch antenna are folded to obtain a circularly polarized antenna. Properly positioning the coaxial feed on the square patch excites two orthogonal resonant modes with a 90 ^° phase difference and achieves a pure circular polarization. Conventional antennas for roof-mounted vehicle communication devices use commercially available ceramic corner-truncated patches whereas the proposed GPS antenna is designed to use a less expensive and more compact FR4 patch. Experiments also showed that mounting the proposed GPS antenna in different locations on the roof of a vehicle had little effect on circular polarization radiation. The fabricated prototype revealed an impedance bandwidth of 2.1% and a 3-dB axial-ratio bandwidth approximating 0.76% at a GPS frequency of 1575 MHz. Experiments confirmed that the characteristics of the proposed antenna were consistent with the simulation results.