Chapter 548: Clutter is not impossible to deal with
Apart from the tactics themselves, the Air Force and the National Defense Work Committee are very interested in another matter.
——Move the radar to the sky.
The topic of the seminar gradually shifted from the jump tactics to the Tu-4 special aerial blind filling.
“Dear comrades, in this battle, when the enemy aircraft entered the blank area controlled by the ground radar station, the Tu-4 special aircraft originally used to attack the P-2V played a very good role in filling the blind spot. This method has greatly improved our operational initiative and control of the airspace, so this time, we also want to see if we can make further progress in this regard.”
When everyone heard this, they felt it made sense and spoke one after another.
Especially those comrades who have held several previous relevant meetings with Gao Zhendong have long admired Gao Zhendong's idea of "radar going to the sky" and have started to think more about it.
"Well, this is a good idea. Comrade Gao Zhendong has mentioned this idea before. Let me tell you, not only the radar, but also the commander and so on can go to the sky together."
"Yes, air command post. With a few planes like this, the coast can be tightly controlled, and a few more are deployed inland as a mobile force. No matter where the enemy comes from, there will be no escape."
“But radar is a problem. Do we have such a good radar?”
"We don't have many Tu-4s in total. We are all here to do this, so we won't have heavy bombers available."
"We can consider using the radar imitated by Lao Maozi Connors, 7 meters It is still possible for the Tu-4 to carry the antenna.”
The imitation Konus is the radar that was originally placed on the Tu-4 for early warning aircraft. It can simultaneously measure range, direction, and The height-measuring radar should be the radar with the best comprehensive performance at this stage under the size and weight constraints we have. However, this radar has a weakness.
"There is no need to consider the quantity of Figure-4. The main consideration is whether its performance is sufficient." At this time, the "Sixth Master", which is almost running out of English letters, is already in the process of domestic production. .
And the Tu-4 is more suitable for this mission than the Tu-16, because it has a longer stay in the air under the same conditions. It is obsolete as a bomber, but it is quite useful as an early warning aircraft.
Even if the Tu-16 cannot be taken to work for a short period of time, it is actually not a big problem. In fact, the Tu-4 and Tu-16 are not as good as domestic combat targets in a short period of time.
Especially the Tu-4, which is small in number, flies slowly, has a short range, and has a small bomb load. It is useful as a deterrent. In actual combat, that's about it.
“The imitation of Konus is good, but its ability to deal with ground clutter is limited.” A comrade who should be engaged in radar said in one sentence the biggest shortcoming of imitation of Konus. .
This was also the biggest reason why our first-generation early warning aircraft died in the end. The original scientific researchers tried their best to solve a series of problems caused by modified engines and huge changes in aerodynamic shape, so that This aircraft can carry a radome with a diameter of 7 meters and a thickness of 2 meters and fly smoothly in the sky.
But in the end, the weak anti-ground clutter performance of the imitation Connus radar made all these efforts come to nothing.
"How bad is the ground clutter handling capability of the fake Konus?" asked a comrade in the Air Force.
The comrade thought for a while and replied: "We have never put this radar in the air, but based on theory and experience, it will fail when it is below XXXX meters."
This four-digit failure altitude made comrades in the Air Force instantly lose interest. The days when the P-2V was wreaking havoc have not passed long, and this ground clutter problem is still fresh in their memories.
In fact, radar's reliable "look down and shoot down" capability existed as an advanced function on radar until the 1980s, and the degree of trouble it caused is evident.
Looking at the faces of Air Force comrades, Gao Zhendong raised his hand: "Comrades, I have some opinions on this issue."
Hearing his words, many people immediately cheered up. This comrade always had a target in mind. If he said he had an opinion, it meant that there should be some solutions.
Especially the comrades of the National Defense Work Committee and the Air Force, Gao Zhendong's "views" are too important to them.
Seeing everyone looking at him, Gao Zhendong said: "First of all, I think that even if we can't deal with ground clutter temporarily, it is not meaningless to have radar in the sky. At least for targets attacking from high altitude, we have It is a means of early warning. Generally speaking, the threat from targets coming from high altitudes is very high and very common at this stage."
When the comrades in the Air Force heard this, they thought it made sense. They also considered it, but they still thought about it. Feeling unwilling to do so, other comrades felt that Gao Zhendong's idea of solving solvable problems first was feasible.
"Well, it makes sense to say that. Anyway, low-altitude targets are also invisible to ground radar. At least control the high-altitude ones first."
"Well, high-altitude and high-speed penetration is the main penetration method now. It is actually good to be able to solve this problem."
"But with the popularization of terrain radar, the penetration method has now shifted to low-altitude penetration. Changed."
"Yes, our attack-5 is just for low-altitude penetration, and we don't even hesitate to sacrifice the combat radius for it." Seeing that everyone has their own ideas, Gao Zhendong added. The second half of his sentence came up.
“Besides, in fact, ground clutter is not completely impossible to deal with.”
Comrades immediately exploded. This problem will not be solved in China, let alone now, even in the next 10 or 20 years. We can’t even come up with theoretical ideas, let alone solve it in practical projects. .
Therefore, Gao Zhendong’s words were fine by those outside the radar industry, but comrades in the radar industry just pinched Gao Zhendong’s neck and shouted, “Speak quickly, speak quickly.”
The same goes for comrades in the Air Force. They are not engaged in radar, but they use radar. They know very well what this sentence means.
Don't talk about them. If Lao Maozi hears Gao Zhendong's words, he will have to imprison Gao Zhendong. It was time for them to truly solve the problem of ground clutter on fighter radars with the MiG-23. Before that, it was just that.
Thinking about it again, Gao Zhendong was the first person to advocate "radar going to the sky". Maybe he had some ideas before he made this suggestion.
Everyone stared at Gao Zhendong with sharp eyes, but the leader of the National Defense Working Committee poured cold water on everyone's heads with just one sentence. Want to hear it? That scores points.
“Comrade Zhendong, you and the comrades working on the radar, go to a branch room nearby and we will discuss other issues here first.”
It is not appropriate to have multiple branch rooms in the seminar. It's rare, but it's very rare to open a temporary branch venue.
Gao Zhendong and the anxious radar-related comrades, led by the conference staff, came to another small conference room. Looking at the helpless comrades, Gao Zhendong continued what he had just left unfinished.
“I have analyzed the radar signal characteristics and feel that we can use phase detection to indicate moving targets.”
Moving target indication (MTI) and moving target detection (MTD) are typical ground clutter processing technologies.
The latter is more effective, but the technical requirements are higher, and it is still a little early to put it out now.
As for MTI, it works.
“Due to the Doppler effect of moving targets, the radar echo reflected by the moving target will be shifted in phase, while the radar echo from fixed targets such as the ground, hills, and buildings will not There is this kind of phase change.”
This principle made several comrades present stupid. At that time, they really didn’t understand it, even if they knew about the Doppler effect, which was more than 100 years ago. , and I don’t know how to use it.
For the Doppler effect, most explanations directly see a shift in frequency, but what is included is a shift in phase.
"Then how to use this phase shift?" I can't think of it, I can't think of it at all.
“Using the latter signal and subtracting the previous signal, the stationary ground object signals will be filtered out, and the changing moving target signals will be retained. This is its basic principle. Although there are many It has flaws, but at least it can basically solve the problem of ground clutter within a certain range.”
Knowing that the comrades still didn’t know the specific operation of this thing, Gao Zhendong drew a delay line cancellation filter on the blackboard. block diagram.
To put it simply, the last radar signal is input into a delayer, and after it is delayed for a period of time, it is subtracted from the next signal.
Using a delayer actually plays the role of storing the last radar echo signal, but the delayer costs much less than waveform storage. This is a very clever design.
When Gao Zhendong said this, the comrades working on the radar immediately understood, this is okay!
"Mr. Gao, your idea is great!"
"Doppler effect, delay cancellation filtering! I really can't think of it."
Although I am not a radar Professional, but the time domain and frequency domain analysis of signals was a professional basic course in Gao Zhendong’s previous life. With this foundation, plus the basic knowledge of downward-looking downward-shooting radar that was found during network alignment, it is no problem to explain an MTI clearly. .
"However, the flaws of this method are also very obvious. The target distance is clear, but the target's motion status is very vague. To a certain extent, it can only indicate whether the moving target exists, but it has nothing to do with the status of the moving target. You know, that's why I call it moving target indication - it can only indicate. Of course, there are some flaws that are limited by other boundary conditions, such as the slower the target, the harder it is to detect."
MTI has many shortcomings, but it has one advantage: the technical requirements are much lower than MTD. It can be done without a computer and without in-depth involvement in digital signal processing, which is not the case with MTD.
By the way, the MiG-23 uses MTI.
For Gao Zhendong, MTI is not good enough, but for comrades who work on radar, this thing is very good!
This is not enough, you want to go to heaven, Mr. Gao!
(End of this chapter)