GPS is a terminal that receives satellite signals for positioning or navigation. To receive signals, an antenna must be used. GPS satellite signals are divided into L1 and L2, with frequencies of 1575.42MHZ and 1228MHZ respectively. L1 is an open civilian signal with circular polarization. The signal strength is about 166-DBM, which is a relatively weak signal. These characteristics determine that a special antenna must be prepared for the reception of GPS signals.

GPS active antenna

Currently, most GPS antennas are right-hand polarized ceramic dielectrics, and their components are: ceramic antennas, low-noise signal modules, cables, and connectors. Among them, ceramic antennas are also called passive antennas, dielectric antennas, and PCTAH, which are the core technology of GPS antennas. The signal receiving ability of a GPS antenna depends largely on the composition of its ceramic part.

The low-noise signal module, also known as LNA, is the part that amplifies and filters the signal. The selection of its components is also very important, otherwise it will increase the reflection loss of the GPS signal and cause excessive noise. The selection of cables should also be based on reducing reflections to ensure impedance matching.

In terms of polarization, GPS antennas are divided into vertical and circular polarization. With current technology, the effect of vertical polarization is not as good as circular polarization. Therefore, except for special cases, general GPS antennas will use circular polarization.

In terms of placement, GPS antennas are divided into internal antennas and external antennas. The assembly position of the antenna is also very important. Early GPS handheld devices mostly used external antennas. At this time, the antenna was basically isolated from the inside of the whole device, and EMI had almost no effect on it, and the satellite reception effect was very good. Now with the trend of miniaturization, GPS antennas are mostly built-in. At this time, the antenna must be above all metal devices, the shell must be electroplated and well grounded, and away from EMI interference sources, such as CPU, SDRAM, SD card, crystal oscillator, DC/DC.

The application of car GPS will become more and more common. The outer shell of the car, especially the car explosion-proof film, will seriously hinder the GPS signal. An external antenna with a magnet (which can be adsorbed to the roof) is very necessary for car GPS.