High Gain SMA Male RG174 1575.42mhz GPS Antenna

GPS Active Antenna SMA Male RG174 GPS External Antenna 1575.42mhz GPS Antenna

Product introduction

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

Parameters:

Classification

⒈ From the polarization mode, GPS antenna is divided into vertical polarization and circular polarization.

With current technology, the effect of vertical polarization is not as good as circular polarization. Therefore, except for special cases, GPS antennas will use circular polarization and linear polarization.

⒉ GPS antennas are divided into internal antennas and external antennas in terms of placement.

The mounting position of the antenna is also very important. Earlier GPS handhelds mostly used eversion antennas. At this time, the antennas were basically isolated from the whole machine, and EMI hardly affected them, and the satellite reception effect was very good. 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 plated and well grounded, away from EMI interference sources, such as CPU, SDRAM, SD card, crystal, DC / DC.

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

3. From the aspect of power supply, it is divided into active and passive.

The external GPS is an active antenna. For example, the Gamma GPS external antenna is basically an active antenna. The passive antenna does not contain the LNA amplifier, just the antenna body.

The main factors affecting the performance of the GPS antenna are the following aspects

1. Ceramic sheet: The quality of ceramic powder and the sintering process directly affect its performance. The ceramic chips currently on the market are mainly 25 × 25, 18 × 18, 15 × 15, 12 × 12. The larger the area of ​​the ceramic sheet, the greater the dielectric constant and the higher the resonance frequency, the better the acceptance effect. The ceramic pieces are mostly of square design, in order to ensure that the resonance in the XY direction is basically the same, so as to achieve the effect of evenly collecting stars.

2. Silver layer: The silver layer on the surface of the ceramic antenna can affect the antenna resonance frequency. The ideal GPS ceramic chip frequency accurately falls at 1575.42MHz, but the antenna frequency is very susceptible to the surrounding environment. Especially when it is installed in the whole machine, the frequency of the silver coating must be adjusted to adjust it to 1575.42MHz . Therefore, when GPS antenna manufacturers purchase antennas, they must cooperate with antenna manufacturers and provide samples for testing.

3. Feed point: The ceramic antenna collects the resonance signal through the feed point and sends it to the back end. Due to the impedance matching of the antenna, the feed point is generally not at the center of the antenna, but to make small adjustments in the XY direction. Such an impedance matching method is simple and does not increase cost. Moving only in the direction of a single axis is called a single-bias antenna, and moving in both axes is called a double-bias.

4. Amplifying circuit: PCB shape and area carrying ceramic antenna. Due to the ground-rebound characteristics of GPS, when the background is 7cm × 7cm uninterrupted ground, the effectiveness of the patch antenna can be maximized. Although it is restricted by factors such as appearance structure, it should try to maintain a considerable area and a uniform shape. The gain of the amplifier circuit must be matched with the back-end LNA gain. Sirf's GSC3F requires that the total gain before signal input should not exceed 29dB, otherwise the signal oversaturation will produce self-excitation.