In fact, this method was used when radar just appeared. For example, in 1935, Robert Watson watt used the short wave radio frequency transmitted by NiuGuo broadcasting company to irradiate the "haiford" bomber 10 kilometers away in the single base passive system.
However, the original simple research found that the accuracy of this method was too poor. At most, I knew there was a target there, and then I didn't know anything. It was not very useful at all. Therefore, this method was soon eliminated.
Only now, with the rapid development of computer technology and the realization of various advanced algorithms for discovering targets, this way has been possible.
For example, the famous silent sentry searches for targets through signals transmitted by mobile towers, high-power TV stations, etc.
This is also based on a principle. If there is a target in the electromagnetic field, it will certainly affect the distribution of the electromagnetic field, so that the target can be found.
Of course, if there is only one receiver, it must be impossible to accurately locate. There must be at least three or four receivers. Moreover, it is best to know the original electromagnetic radiation here, so it is the easiest to find the target.
In the homeland air defense, these are easy to do. For example, the transmission towers of various TV stations and various mobile communication towers under construction are releasing electromagnetic waves. Using these electromagnetic waves, we can know the target of breaking into this airspace. Of course, it seems that Qin Guan is still very sci-fi to say this now. When the research project is determined and handed over to 114 institutes or other institutes, Qin Guan can take the corresponding data and speed up the research and development of this project.
Using this passive radar, in addition to finding stealth aircraft, another advantage is that it can find low altitude targets. After all, low altitude targets will also lead to changes in electromagnetic field distribution.
Unless the fighters are all made of titanium alloy, there must be no hiding.
Of course, there are many uncertainties in this. When meter wave radar and passive radar develop and defend together, it can be foolproof.
At this meeting, Qin Guan successively put forward various new views, and the people present were left to digest and understand.
How to conduct territorial air defense in the future war? And now, completely different ah!
Seeing that they were trying to understand the views given by Qin Guan, Qin Guan finally held back: "in the future war, there are new styles. We'd better talk about them tomorrow."
Qin Guan was afraid of too much. They couldn't digest it. However, they were obviously unwilling. Now when they heard Qin Guan's words, general Lin said, "anyway, there is still time now, President Qin, go on. What else is there in the future?"
"Cruise missiles," Qin Guan said, "in addition to stealth aircraft, the second biggest threat to us is cruise missiles, which are often used in the first round of attacks."
As we all know, cruise missiles are weapons for ground attack. However, unlike ballistic missiles, they are not a high throw trajectory, but a cruise route flying at ultra-low altitude, just like a penetrating fighter. However, they are lower than the height of a fighter. If they are flat land like the desert, their flying altitude may be more than ten meters, If it's a mountain, it won't fly more than 100 meters, and it can even drill through the valley. One of its basic principles is that it's still difficult to capture ultra-low altitude targets, which is a worldwide problem. When ultra-low altitude targets are combined with the improvement of stealth technology, it's even more difficult to deal with.
It is precisely because it is relatively hidden. Therefore, in the first round of attack, it is generally cruise missiles and stealth aircraft to knock off those threatening targets, such as long-range radar, etc. the second round will be those ordinary aircraft. In the first round, it is used to knock on the door.
Look at the wars of later generations. In the first round, all kinds of warships of the eagle people's navy and all kinds of bombers of the air force will throw a large number of cruise missiles, often hundreds. In future wars, it will be money.
At present, the threat of cruise missiles has not yet begun, but in the future, it will be a very difficult opponent. Our own side has begun to develop cruise missiles, but it is not very clear how to guard against such missiles.
"Cruise missile is also an ultra-low altitude target. Moreover, it is a missile and the echo of the target is smaller. Therefore, it puts forward more stringent requirements for our air defense." Qin Guan said: "In the first step, the discovery can have a great connection with our current research on how to find ultra-low altitude targets. We can use our research results. After discovery, how to attack cruise missiles still needs further research. Fortunately, cruise missiles are easy to attack as long as they are found."
Cruise missiles also attack targets by stealth and ultra-low altitude. However, they are pilotless and fly according to the established route. In the face of such targets, it is easy to attack them as long as they are found.
There is no need for long-range missiles. For general long-range air defense missiles, the minimum firing height is relatively large, and the target that is too low can not be hit. This kind of ultra-low altitude cruise missile uses medium-range or short-range missiles, and even small caliber rapid fire guns, such as the 730 gun of the Navy, also has a better attack effect.
There are all these technical reserves, but if we don't conduct special research now, we will be in a hurry once we find the threat of this kind of thing.
At present, in order to resist foreign enemies, the army has carried out three attacks and three defenses: "fighting fighters, tanks, airborne, atomic, chemical and biological weapons". However, with the development of the times, this has become obsolete.
Now, with the changes in the international situation, the "new three attacks and three defenses" should be put on the stage: "attack stealth aircraft, cruise missiles and armed helicopters; prevent precision attack, electronic interference and reconnaissance and surveillance." this is a new threat that the army needs to face with the development of technology.
And now? Do you want to formally put forward this new three hit and three defense?
In fact, the threat of armed helicopters is not great, because armed helicopters dare not come out without seizing air control. However, since it is for the sake of foresight, let's put it forward! This can also give today's meeting a profound summary!
Qin Guan said to the crowd, "everyone, now I have a new proposal to change our original three attacks and three defenses. With the development of the times and the progress of technology, what we want to fight and defend has changed."