UAV Navigation Amplifier //GPS Amplifier// 1.1-1.6GHz Amplifier
The frequency range is mainly concentrated in 1100-1700MHz,
GPS L1, L2, L3, L4, L5
GLONASS: L1, L2
BDS: B1, B2, B3, L, S
GALILEO: L1, E5b, E5a
The GPS signal is very weak and below the natural background noise near the ground. Using commonly used passive antennas with 3-6dB gain in open areas, the total reception level can reach up to about -120dBm. The civilian GPS signal is a spread spectrum signal with a frequency of 1575MHz and a bandwidth of 2.046MHz. The spread spectrum gain is 43dB, and Cb/N0 is considered to be 6dB. Although any form of interference can be effective as long as it is high power, the effectiveness of interference in some frequency bands is poor due to the high spread spectrum gain. Among the easy to implement methods, full band noise interference has an advantage, with a bit error rate higher than 10% when the following conditions are met:
(1)The bandwidth of the interference signal is equal to or greater than 2.046MHz, covering the entire frequency band of the GPS signal. (2) After the interference signal is received by the GPS antenna, its total power level should be higher than -83dBm.
The main lobe direction of the GPS antenna on the drone is facing towards the sky, which can provide some isolation from ground interference. The size of isolation depends on the quality of the antenna, installation method, and the structure and materials of the drone itself. If the antenna is installed in the center position of the drone and there is a whole piece of carbon fiber mesh board on the drone to block the ground direction, it can usually provide 30-40 dB of isolation. If the antenna directionality is poor and the installation is not vertical enough, the isolation will be reduced. Assuming the gain of the drone GPS antenna to the ground defender (interference source) is -40dB, and the gain to the sky meets the requirements for normal GPS antenna reception, that is, the total reception level can reach -120dBm. The drone is 100 meters away from the ground, and the antenna gain of the interference transmitter is 0. According to the free space loss formula, the required transmission power is: Pt=Pr+32.45+20logd+20logf-G=-83+32.45-20+64+40=33.45dBm
The above calculation means that if the interference bandwidth is moderate, only 2W of transmission power is needed to kill unmanned aerial vehicle GPS within a range of 100 meters. If the interfering antenna has a 6dB gain, then only 0.5W power is needed. It was found through actual testing that the 0.01W power noise amplitude modulation (1) brand unmanned aerial vehicles extensively use lightweight plastic, resulting in GPS antenna ground isolation being far less than 40dB.
The total received level cannot reach -120dBm (which is close to the theoretical optimal value and is usually considered as -130dBm in engineering).
The cheap receiver despreading scheme is too simplified and does not fully utilize the 43dB spreading gain.
The simplest broadband signal is noise frequency modulation. Of course, stronger correlation interference can also be used to deceive, such as using GPS simulators to generate some false signals. But considering that the interference power is already not large, it seems unnecessary to incur this expense.
The behavior of a drone after losing GPS signals depends on the functionality and settings of the flight control system. For skilled operators, GPS is not necessary. In the era without GPS, pilots of aerial models could still complete their envisioned flight routes through visual inspection or image transmission. However, for inexperienced operators, the consequences of eliminating GPS signals are already quite serious, as the automatic return function of the drone has become ineffective and must rely entirely on manual operation. Based on the defense experience already mastered, this is basically equivalent to not being able to fly back. If you want to avoid the consequences of GPS interference, you can write about the following points:
Combined with the antenna with a gain of 5dB, it can already defeat most brands of drones' GPS within a range of 100 meters. This may be caused by the following reasons:
Hot News2024-08-15
2024-08-15
2024-08-15
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