GPS is related to all aspects of our daily life. The antenna manufacturer mainly introduces the classification, structure and performance of GPS antenna, as well as the matters needing attention in the selection of GPS antenna, and gives some suggestions for purchase.

1、 GPS overview

GPS is a terminal for positioning or navigation by receiving satellite signals. The antenna must be used to receive signals. GPS satellite signals are divided into L1 and L2, with frequencies of 1575.42MHZ and 1228MHZ respectively. L1 is an open civil signal, with circular polarization. The signal strength is about 166-DBM, which is relatively weak. These characteristics decide to prepare special antenna for GPS signal reception.

2、 Classification of GPS antenna

1. In terms of polarization mode, GPS antenna can be divided into vertical polarization and circular polarization. With current technology, the effect of vertical polarization is not as good as that of circular polarization. Therefore, except for special cases, the GPS antenna will adopt circular polarization.

2. GPS antenna is divided into internal antenna and external antenna in terms of placement mode. The assembly position of the antenna is also very important. In the early days, most GPS handsets used an everted antenna. At this time, the antenna was basically isolated from the inside of the whole machine, and EMI hardly affected it. The satellite receiving effect was very good. Now, with the trend of miniaturization, GPS antenna is mostly built in. At this time, the antenna must be above all metal devices, and the shell must be plated and well grounded, away from EMI interference sources, such as CPU, SDRAM, SD card, crystal oscillator, DC/DC.

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

3、 Structure of GPS antenna

At present, the vast majority of GPS antennas are right-handed polarized ceramic media, consisting of ceramic antenna, low-noise signal module, cable and connector. Ceramic antenna is also called passive antenna, dielectric antenna and PATCH, which is the core technology of GPS antenna. The signal receiving ability of a GPS antenna mostly depends on the composition of its ceramic parts.

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