GPS is a terminal device that receives communication satellite signals for positioning or navigation. To receive the signal, an antenna must be used. GPS communication satellite signals are divided into L1 and L2, the operating frequencies are 1575.42MHZ and 1228MHZ respectively, among which L1 is an open civilian signal, and the signal is circularly polarized. The signal strength is around -166dBW, which are relatively weak signals. This feature depends on the preparation of a dedicated antenna for GPS signal reception.
(Beitian Beitian External Antenna BN-143TJ)
1. There are several types of GPS antenna interfaces
1. In terms of polarization, GPS antennas are divided into vertical polarization and circular polarization . Vertical polarization is not as effective as circular polarization. Therefore, except for emergencies, the GPS antenna will use circular polarization and linear polarization.
2. In terms of placement, GPS antennas are divided into built-in antennas and external antennas . The installation position of the antenna is also very critical. Most of the initial GPS handheld terminals use an outwardly tilted antenna. At this time, the antenna and the internal structure of the entire device are basically protected, and EMI is basically not affected by it, and the satellite reception effect is good. With the fashion trend of miniaturization, most GPS antennas are built-in. At this time, the antenna must be on the top of all metal components, and the shell must be electroplated and maintain a good grounding device to avoid EMI interference signals, such as CPU, SDRAM, SD card, crystal oscillator circuit, DC/DC. The use of car GPS will become more and more popular. The vehicle shell, especially the explosion-proof membrane of the car, seriously blocks the GPS signal. An external antenna with a magnet (that can be glued to the roof) is necessary for a car GPS.
3. From the power supply system level, it is divided into active and passive. The external GPS is an active antenna. The passive antenna is that there is no LNA amplifier, just the antenna itself.
2. Types of GPS signal antenna interface
The interface of GPS equipment can be divided into data information interface, switching power supply interface and microwave radio frequency interface. The actual specifications of various interfaces are as follows: data information/switching power supply interface: national standard 20-pin (2×10) power plug, RTCM104/RS-232, NMEA0183; microwave radio frequency interface: OSX (or MCX type, pocket type, snap-on).