The GPS satellite timing and positioning system has been widely applied in various fields. In the traditional GPS satellite timing and positioning process, under the general conditions, the receiver needs to have a more open receiving environment, at least 4 or more than 4 satellites can be observed at the same time. However, in the areas of bad GPS signal, such as the urban core area, the interior and underground parking lots, because the GPS signal is obstructed, the intensity is weakened and the multipath effect is affected, the receiver can not lock the signal or locate, and the result is quite deviant, which is difficult to meet the positioning requirements. The GPS signal transponder technology uses the existing GPS signals to improve the positioning ability. The use of these new technologies can still provide reliable location results when the receiver works in the bad GPS signal area.

GPS/ Beidou signal transponder is applied in the exhibition hall (indoor). If indoors do not take any measures, the Beidou customer terminal is almost unable to detect the satellite effective signal. The signal transponder is that when the indoor GPS or Beidou signal is needed, the signal will be received through the outdoor antenna, and the circuit of the host will be amplified again, then the antenna will be sent out to make the room. The receiving terminal can also be successfully positioned in closed rooms.

The multipath effect of GPS signal is limited in indoor positioning. Under the condition of visibility, the generation of standing waves can also cause signal attenuation. Each transponder is transmitting GPS signals. Each transponder uses a preset frequency, and multiple frequencies generate multiple standing wave modes. The receiver will process the signal with lower delay by interpreting the C/A code, minimizing the influence of multipath effect on the location result. The problem to be noticed in the measurement is the time synchronization between the transponders.

The SYN2308 GNSS satellite signal transponder is mainly composed of three parts: the satellite receiving antenna, the low loss radio frequency cable and the transponder main engine.

The radio frequency signal is amplified and filtered by the receiving antenna, then sent to the transponder host to complete the signal extension and demodulation, and realize the positioning function check of the navigation signal. At the same time, the code stream and message information are re modulated and upconverted to get the radio frequency signal, and sent to the transmitting antenna through the RF port of the transponder main engine.

Main functions and technical indicators

The GPS transponder has two main functions, one is satellite signal enhancement and two is self location check. The transponder receives the navigation signal of the BD/GPS, demodulates the stream and message information, and re modulates and upconversion to get the RF signal, and completes the signal forwarding function, and the output signal level can be adjusted according to the actual demand.

When the SYN2308 type GNSS satellite signal transponder is actually used, the receiving antenna is usually installed on the top of the experimental building, the transponder host, the GNSS transmitting antenna and the test equipment are placed in the laboratory, and the two are linked by 30 meter radio frequency cable. Because the satellite navigation signals in the air are extremely weak, in order to avoid the deterioration of the signal, the receiving antenna needs the design of the low noise active antenna. The frequency cable should be designed with low loss, and the signal controller will receive and forward the signal to improve the spectrum quality of the transmitted signal.

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