Uav signal transmission combination: remote map signal and positioning navigation signal (GPS, Beidou, Glonass)

The remote control signal of the UAV is 2.4GHz/5.8GHz band, which is the signal transmission frequency band between the earth and the sky of the UAV (the aircraft and the PTZ). Say a very common thing, walkie-talkies (some places called pagers) is the use of long-wave signals, the civil effective distance is basically only 3KM (military is another matter), this does not need a third-party relay station transmission method is fast, equipment manufacturers can directly choose the carrier frequency band according to the situation. Disadvantages are also very obvious short distance, strong interference.

Then why does this remote control signal not use our common 4G signal, or use 5G signal?

In theory, 5G signal is certainly possible. However, the current coverage area trend of 5G is relatively small. 4G signal delay is slightly higher, in the complex area demonstration can reach 100mm-200mm, this delay is basically equivalent to you see a house in front of you, in you want to control the plane to avoid obstacles has hit it. Some people say that the plane has an obstacle avoidance function, that is the aerial drone you play, if it is a crossing plane then it is no game. Graph transmission signals are generally in the 5.8GHz frequency band, which is a high bandwidth, that is, our ordinary people generally say that the network speed is fast (see clearly I am not talking about fast speed). Strictly speaking, the fast speed should be a small delay, that is, the signal is sent there, and the signal is received here, and the time difference between the two. Therefore, the relay station can not be used as the transmission mode of the UAV remote control signal. So here comes the point. Since the relay station is unavailable.

The transmission mode of the drone uses two communication combinations:

1. 2.4GHz/5.8GHz band: the drone's own signal is used for remote control and photo transmission.

2, GPS signal (there are also Beidou signal). The core for positioning, navigation, and one-click return.

So this is going to be very detailed.

Case 1: If you just lose the remote control signal, such as occasionally flying a little too far, too far.

Then you start a key return, this time you need to use GPS navigation, GPS signal is a relay satellite, that is to say, as long as the micro can cover the area theoretically you have GPS signals. But you do not be happy too early, because you control the drone, and to achieve extremely accurate rapid positioning, then in theory to be able to achieve more than 8 satellite connection, then you can achieve accurate drone positioning, so as to ensure the most basic navigation guarantee of one-click return. Friends familiar with navigation, with four satellites can achieve basic positioning capabilities, but if the accuracy within 10m is achieved, and the availability reaches more than 95% of the case. More than eight satellites are needed. Therefore, consumer drones, including DJI, use a navigation combination of GPS+ Glonass. To put it bluntly, it is the open code protocol, which can connect to the satellites of different countries. Of course, almost all UAVs now support the Beidou navigation system. Satellites that drones can search in empty areas. Basically, on the square of the city, the number of satellites is more than 10, which can ensure very accurate positioning.
Therefore, the first hard condition is whether the UAV can connect to satellite navigation signals such as GPS after losing the remote control signal, and achieve accurate positioning of more than 8 satellites.

some one said, then where do I know if I can connect to?

This is easy to do, simply say, can not be connected to the satellite navigation signal, and the satellite navigation antenna (GPS antenna) is good or bad, satellite antenna has hundreds of thousands to hundreds of products, this is definitely the difference. In addition, the external environment also has an impact, under normal circumstances, as long as you do not go to the "Valley of Kings" basically does not have much impact. But you have to go. No one here can stop you. In addition, indoor flight, especially in steel plants, will also lose satellite navigation signals.

So with the satnav, you can definitely come back? Is it enough to fly back? Did you set the relative height correctly? Is there a sudden wind, birds, etc.?

These are all important factors in whether the plane comes back or not. Therefore, the loss of the remote control signal, one click back to hope that the plane comes back, is a luck project.

Scenario 2: So if you lose your satnav, is there a chance to come back?

Not to repeat what I said before, simply say, now the drone jammer, is to interfere with remote control signals and satellite navigation, to put it blunter
The civilian version of the suppression. Without satnav, drones are truly unadopted children who will soon crash.

Because the civil GPS signal (or other satellite navigation signal) is fixed, which is the commercial navigation specially allocated frequency band, the civil GPS signal is the frequency of 1575MHz, 2.046MHz bandwidth spread spectrum signal, spread spectrum gain 43dB, Cb/N0 according to 6dB consideration, so in the technology of this parameter, It's actually very easy to build a device for electromagnetic interference. Of course, the military's electronic suppression is more extensive than that.

Basically, it can be summarized as: no signal is basically the loss of the drone, even a manned aircraft, in the state of loss of signal can not return.