Chapter 738: Good things are not necessarily expensive
They quickly stood up and began to draw the radar plan on the blackboard.

They were reluctant to erase the coordinate diagram drawn by Gao Zhendong, as it might be useful in the future, so they just drew on the edges and corners, explaining to Gao Zhendong as they drew.

Gao Zhendong roughly understood that this radar was derived from the Zhengxian No. 60 radar, and the principles were similar, but the use of digital signal processing boards and DJS-DJ enhanced the radar signal processing capabilities, and according to Gao Zhendong's guidance, a moving target indication function was added to enhance the ability to resist clutter.

The plan is very conventional, with no major problems, but it also has no major features. It can be regarded as using advanced technology to solve the inherent problem of small caliber. However, judging from the results, the solution is not thorough, mainly because it cannot adapt to the further reduction of sea-skimming flight altitude.

Gao Zhendong looked at their plan and asked, "Can you tell the target capture situation from the radar data?"

Qi Gong thought for a moment and said, "We can see a little bit. The amount of radar data is relatively large, and it is impossible to record the original signal. Only some result process data and important nodes will be recorded."

Gao Zhendong said: "Look at the radar data first. To what extent is the target locked?"

Roughly translated, it means whether the target echo is clear and whether the target status and position are accurate.

Qi Gong nodded: "This can be seen a little bit. When it is locked, the situation at the time of locking will be recorded."

After saying that, he and Su Weihua began to look through the data records, looking for the answer Gao Zhendong wanted.

After they found it, they looked at it for a few seconds, then raised their heads, full of admiration.

"Professor Gao, you already knew that radar lock is unstable? The error range for judging the target's position is relatively large?"

Gao Zhendong nodded: "My guess is that your radar has limited power. The only way to increase the energy of the radar signal and improve the signal-to-noise ratio is to increase the pulse width."

This radar is a single-pulse radar, which is cheap and available in large quantities. It is suitable for use on this missile. The price of PD is incredible.

The total energy of a pulse signal is related to its amplitude and pulse width. When power is limited, it can only be increased by increasing the pulse width.

The reason was known, but the principle was unknown. Su Weihua asked, "Lao Gao, why does increasing the pulse width reduce positioning accuracy?"

"Because the pulse width is large, it means that the time range of the radar echo signal is longer, so the calculation is naturally inaccurate and can only calculate a large range."

Even the initial lock is relatively vague, and when the clutter worsens, the possibility of natural unlocking is high.

Once a problem is found, at least there is a direction to tackle it. Even if Gao Zhendong did not say the solution, it is still very helpful to Qi Gong and others, but things are far from that simple.

"Since you have already used the digital signal processing board, you have the basic conditions for solving this problem. I have a suggestion for you. You should go to XX unit and discuss pulse compression technology with them. It will be helpful for you to solve this problem." Gao Zhendong directly pointed out a way for them.

Gao Zhendong briefly introduced to them the benefits of pulse compression technology. Qi Gong was extremely excited. Every benefit of this technology is aimed at our needs, such as improving accuracy, resolution, and signal-to-noise ratio... I want it so much!

"Ah? Some units are already developing related technologies? But can we get them?" Engineer Qi was both happy and worried. It was not that easy to ask for technology without any evidence.

Gao Zhendong nodded: "I will write a note for you, and you just need to go to the Defense Work Committee to ask for permission. There shouldn't be any problem." This kind of basic technology should be spread as widely as possible in relevant domestic units so that everyone can use it.

When Mr. Li and the others heard what he said, they naturally understood that this pulse compression was definitely related to the man in front of them. In fact, judging from his confidence, the role he played in it was very important.

Su Weihua even felt that he had gone to college for nothing. Did Gao Zhendong secretly study every day while they were sleeping? They were totally not on the same level.

He fell into deep self-doubt, but for Qi Gong, it was good news from heaven. In one word, awesome! ! ! !

Gao Zhendong didn't care how happy he was. In Gao Zhendong's opinion, this radar system had more than one problem, or there was room for improvement.

He pointed to the radar structure diagram on the blackboard and asked, "Are you using a straight-mounted long-focus parabolic antenna for this antenna?"

The parabolic antenna is suitable for use here. This is not the era of the future when phased array radars are flying everywhere and even phased arrays are used for spraying pesticides.

Engineer Qi nodded. "Yes, the parabolic antenna has a reasonable cost, good directivity and sidelobe performance. Overall, it is more suitable than the Cassegrain and inverted Cassegrain antennas. The long-focus parabolic antenna has better electrical performance than the short-focus parabolic antenna, so we finally adopted this solution."

Both Cassegrain and inverted Cassegrain antennas will suffer from sidelobe rise and gain reduction due to the shielding problem of the secondary reflector, which is much worse than parabolic antennas for solid anti-ship missiles that are already short of total energy and have to deal with severe sea clutter. Another reason is that the Zhengxian No. 1 radar is a straight-mounted long-focus parabolic antenna.

Gao Zhendong also approved of his overall choice, but he had some suggestions on the specific plan.

"Well, the parabola is indeed a good choice here, but regarding the specific plan of the parabola antenna, I do have a suggestion. We should use a long-focus offset parabola antenna instead."

"Offset parabola?" Qi Gong is not familiar with the most advanced radars, so he is not very clear about this thing.

Gao Zhendong nodded and explained the offset parabola to him. It is actually very simple. The upright parabola places the feed source at the central focus in front of the parabola, while the offset parabola cuts off a part of the parabola antenna, and the feed source is still placed at the focus of the complete parabola to which the part belongs. In this way, it looks like the feed source is on one side of the antenna, and there will be no center obstruction.

Gao Zhendong roughly drew a picture, and Qi Gong took a look at it. He intuitively thought that this method was interesting and brilliant!

"Professor Gao, your idea is great. It looks like a simple deflection, but it solves the problem of the feed and feed bracket blocking the signal field, reduces the sidelobe level, and increases the signal gain."

This is a typical example of the conflict between theory and practice. In theory, the performance of the upright feed is the best, but in reality, due to the obstruction of the feed itself and the bracket, it will have a considerable impact on the radar signal.

Because the actual feed source is not a point in theoretical analysis, but a real entity. As for the bracket, it does not exist at all during the analysis, but in fact it cannot be avoided.

This is just like the "point mass" in mechanical analysis, which does not exist in reality.

Gao Zhendong smiled and said, "You have to pay attention to this. The maximum receiving direction of the feed source must be pointed to the center of the offset reflector. In this way, basically all the advantages are obtained, and the disadvantages are not increased much."

Read the error-free version at 69shuba! 6=9+shu_ba is the first to publish this novel.

Qi Gong and Su Weihua were full of admiration for Gao Zhendong. This simple offset looked simple, but the most essential part of it, "cutting off a part of the parabola and using its original focus to achieve the offset effect", was beyond their imagination.

"Thank you so much, Professor Gao. Your skills are truly amazing." Engineer Qi became more confident in solving the radar problem. With a better antenna and better signal processing technology, he didn't believe that this problem could not be solved!

Gao Zhendong added: "You guys try this antenna first. If it still doesn't work, we'll think of other ways. This is the cheapest way."

What? You have another solution? Just because this is the cheapest, you let us try this first?

Qi Gong suddenly remembered a common character in martial arts novels - Bai Xiaosheng.

Gao Zhendong really has a solution. The antenna can actually be a flat slot antenna, which has better performance than these, but the only problem is that it is expensive!

Gao Zhendong did not have the idea of ​​putting all the new technologies into production at once. The most important thing for tactical missiles such as anti-ship missiles is that they are sufficient and usable, and that they are cheap and simple enough to be mass-produced.

The problem of the dropped bullet has basically been solved. At least in the opinion of Mr. Li and his team, there is no other evidence to support any other problems. They are extremely satisfied with the results of this trip to Beijing. Professor Gao is really reliable!

Seeing this, Mr. Li also asked something else: "Professor Gao, do you have any other suggestions for this missile?"

Gao Zhendong thought about it and made a suggestion that was not really a suggestion.

"You all know C6108, right?"

"I know, I know." They all knew very well that this thing was another masterpiece of the person in front of them.

"I suggest you replace the DJS-60DJ with a computer based on the C6108. In fact, the entire C6108 system is much cheaper than the DJS-60DJ, and it can save a lot of volume and weight. The C6108 can be specially selected as a military-grade reinforced version."

The DJS-60D itself is not too heavy, but after military reinforcement, the weight goes up quickly, to several dozen kilograms. The motherboard area is only about one-eighth of that of the C6108. Taking reinforcement into account, the cost and weight savings are really a world of difference.

Li and Qi were both surprised and delighted by the news.

They don't want to use C6108? They dream of it. It's lighter and smaller, and the computing speed is at least 2.5 times faster. If they don't want to use it, they are stupid.

But I can’t afford it. Such a good thing must be very expensive, right?
I didn't expect to learn from Gao Zhendong that this thing is actually cheaper than DJS-60DJ? Why don't you buy it now?
"Is this true? Thank you so much, Professor Gao." Mr. Li thanked him repeatedly. The benefits that could be gained from this thing would go beyond just Qi Gong's guidance subsystem.

(End of this chapter)