Car microstrip GPS antenna

GPS is very widely used by the civil users who want to obtain location positioning, for scientific purposes and by the satellite navigation services. The antenna that provides continuous connection between a satellite transmitter and receiver is one of the most important components of the GPS. Today's GPS is using two carrier frequencies, namely L1 = 1575 GHz, L2 = 1227 GHz. The GPS antennas used by the Europe-wide eCall system and the American On-Star service intended for quick automatic notification about road accidents interact with the antennas of mobile phones of the drivers who have had an accident and need immediate assistance. The system allows the driver both to deliver information and to request the car positioning at the same time. The article presents a designed, constructed and tested model of GPS antenna fabricated using microstrip technique. The mobile GPS antenna model has been designed using the microstrip technique as a printed antenna with a rectangular radiator with undercuts to provide rotating polarization. In order to design the antenna transmission line model and CST simulation environment based on FTDT methodology were used. A 1.5 mm thick technoService FR-4 laminate metal-plated on both sides with dielectric permittivity εr = 4.6 was used in the design. The laminate is coated with 0.07 mm thick copper layer, whereas the loss tangent amounts to 0.02. Using the computer simulation method the following was determined: directional characteristics, input impedance, standing wave ratio, scattering matrix ratio S11, as well as polarization ellipse. The paper also provides the results of laboratory measurements of antenna parameters carried out in the anechoic chamber. A comparative analysis of the GPS antenna parameters obtained by means of the computer simulation method and laboratory measurements is presented. The antenna described has the right-hand rotating polarization. Due to its small dimensions the antenna model is perfect for applications in the motor-car sector. In terms of dimensions the antenna perfectly fits into its designated place, i.e. the car windshield. The impact of windshield parameters was also taken into account during the antenna designing process. The antenna may also be integrated with the single in-line package with other car antennas.