Chapter 722 Pulse Compression
Gao Zhendong said to the comrades from Factory 1274 who came to cooperate with the test: "After the installation is completed, try to carve a batch of 3-micron standard test masks, and then send them to your factory for packaging. The whole process from lithography to packaging must be completed."

The standard test mask has no function, it is just a mask to test whether the 3-micron process is qualified. There is no need for any functional chips now, anyway, it is enough to pass the whole process test to prove that the 3-micron process chip technology already exists.

The comrades from Factory 1274 nodded in agreement to his request, but they didn't care why, as it was not their business.

Gao Zhendong is eager to get started on this matter. Everything is ready except for the right time. He has been waiting for a long time.

However, photolithography experiments take time. We have already waited a lot of time, so we don’t care about this little bit. We cannot eat hot tofu in a hurry.

Gao Zhendong put aside the things here and turned back to the office. The staff from the third factory office came to inform him that someone was looking for him.

When Gao Zhendong arrived at the reception room, he was met with familiar faces, the comrades who were working on PD Radar.

"Chief Engineer Gao, the test of the flat slot antenna you gave us has been completed, and the results are very good! It has high gain, low side lobes, and can perform waveform synthesis to a certain extent!" As soon as General Manager Liu arrived, he brought good news to Gao Zhendong.

Gao Zhendong was very happy. He designed this flat slot antenna based on a paper he found in the system. After thoroughly studying it, he improved and designed it according to the actual radar band we used, and then produced it in the third factory.

Although there was definitely no problem with other people's doctoral thesis, he was still a little worried about whether there would be any problems after his improved design, and he estimated that it would need to be modified.

But he didn't expect it to be so smooth, which made Gao Zhendong feel a little proud. He thought, "Brother, I'm not just a copycat, I have my own things."

The success of the flat slot antenna has enabled our radar hardware conditions to reach the pinnacle of existing radar technology.

The combination of flat slot antenna, traveling wave tube and digital signal processing device will surely shine even brighter.

Mr. Liu obviously felt that he had not gotten enough of the flat slot antenna. This thing was really useful: "We tested it and found that by using the characteristics of the flat slot antenna and using electric scanning in the horizontal direction, it can greatly improve the data refresh rate and multi-target processing capability of our radar! Mr. Gao, you came up with this 'sudden idea', which is really amazing!"

Generally speaking, enemy aircraft groups in a single actual combat are usually distributed in several identical altitude ranges, so when dealing with a certain type of enemy aircraft, their altitudes are generally the same.

In this way, the scanning speed and requirements in the vertical direction are not urgent, but the scanning in the horizontal direction is very important.

So when Mr. Liu realized that this flat slot antenna can really achieve electronic scanning in a certain direction, he chose horizontal electronic scanning and vertical mechanical scanning without hesitation. At the same time, it can also assist mechanical scanning in the horizontal direction. In this way, the scanning capability of the radar wave is brought to the extreme.

"Thank you for your hard work. I had no idea whether my idea could be realized. Your test has put my mind at ease."

Mr. Gao is just too modest. His flat slot antenna, at least when used on airplanes, leaves all other existing antenna forms far behind.

In fact, it’s not just on airplanes. In Gao Zhendong’s previous life, it was also not uncommon to see flat plate gaps on ship radars.

"Mr. Gao, we are really ashamed when you say that." Mr. Liu said with a smile.

Gao Zhendong shook his hand cheerfully: "Yeah, no more, no more, haha. Let's get into the detailed design now, right?"

Gao Zhendong has basically gathered all the necessary peripheral technical conditions, and it seems that we have now entered the detailed design stage of the radar.

"Yes, that's right. We have now reported to the Commission and have completely stopped the copying of the RP-1 radar. All of our technicians are now working on this new pulse Doppler radar."

This is good news. In order to provide a backup for the PD radar, the Defense Work Committee retained the imitation and improvement work of the RP-1 radar.

But now, as Gao Zhendong has come up with one radar technology after another, the imitation and improvement of RP-1 has completely lost its meaning. It has no effect except wasting resources and funds.

Let me put it this way, even if the PD radar is not developed, Gao Zhendong can use the technologies he has come up with to quickly assemble a moving target indication monopulse radar with an inverted antenna, which can crush the RP-1 to the ground.

So after receiving the application from General Liu and his team, the Defense Work Committee immediately followed their advice and decisively stopped the imitation of the RP-1 radar. They really couldn't stand this broken thing anymore.

For the National Defense Work Committee, there are many projects that have been shelved midway, but this kind of shelving is the one that makes them happiest. They do it happily and without any burden.

Gao Zhendong was also pleased to hear this: "What kind are you planning to do now?"

"After weighing the pros, cons and difficulties of the various PD radars you introduced, we first chose the medium-repetition-frequency PD radar, which has a better balance of effect, cost and difficulty." With the technology in hand and a clear mind, Mr. Liu and his team became more rational in their choice. According to their previous habits, they would probably want to use high-repetition-frequency PD right away.

Gao Zhendong nodded: "Well, this is a good choice, very sensible."

Mr. Liu laughed, "It's mainly because we've evaluated that even with medium-heavy frequencies, the performance after it's done will be unrivaled. So we'll first make one that's easy but definitely has strong enough performance, and leave the better ones for later, hahahaha."

Gao Zhendong also smiled: "Well, this is a good idea. Let's first solve the question of whether there is or not. And even if this question is 'whether there is or not', it is far better than the best of others."

Hearing Gao Zhendong say this, Mr. Liu felt a little embarrassed.

"Mr. Gao, we came here this time because we encountered some problems in the design. We thought about it over and over again, but couldn't find a solution, so we had to trouble you again."

"Well, tell me about it, we'll discuss it together." Gao Zhendong said very modestly, but for him, Mr. Liu and his team have solid basic skills. The advantage of this is that, except for devices like traveling wave tubes and flat slot antennas, he only needs to provide principled solutions to most problems. Mr. Liu and his team will handle the rest very well.

For example, anyone who is engaged in signal processing knows how to use Fourier transform. Mr. Liu and his colleagues also know it, but for the time being, they do not quite understand how to use Fourier transform to solve specific problems.

So for Gao Zhendong, as long as Mr. Liu can raise a problem, he can always find at least a solution in principle. The rest will be much easier for Mr. Liu and his team. After all, they have another powerful weapon in their hands - digital signal processing devices. No matter whether they are board-level or IC-level, having them and not having them will make the difference.

"Here's what happened. In order to increase the transmission power, we increased the pulse width of the pulse signal."

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The transmission power depends on the product of the pulse amplitude and pulse width, but the increase is limited, even with a traveling wave tube. At this time, the simplest way is to increase the pulse width.

Gao Zhendong probably knew what was going on. Without waiting for Mr. Liu to continue, he smiled and asked, "After the pulse width was increased, the accuracy was found to be reduced?"

Mr. Liu slapped his thigh and said, "Yes! Mr. Gao is really proficient in signals. Once the pulse width is widened, the location information represented by the echo becomes blurred, and the error range ranges from hundreds of meters to kilometers. In short, it is impossible to accurately extract the target's location information. We have thought of many ways, but this is a problem at the principle level and we have not found a solution."

The problems caused in principle are quite troublesome, commonly known as "fetal disease". We all know how troublesome congenital diseases are.

What surprised Mr. Liu and the others was that Gao Zhendong basically didn't think about this problem at all. After all, he had actually studied radar signal processing in detail in his previous life, so he didn't even need to search for information.

"This is easy. I'll teach you a method: pulse compression!"

"Pulse compression?" This is a brand new technology, and Mr. Liu and his colleagues have never heard of it.

"Yes, pulse compression. Compress the pulse width of the received signal. For example, compress the pulse width of 10 seconds to 1 second while keeping the center of the signal peak unchanged. This can solve your problem and bring other benefits."

This technology is basically standard on later PD radars and was developed to solve this problem. As for the 10 seconds and 1 second here, Gao Zhendong just said it casually for the sake of example.

Mr. Liu is very familiar with signal processing. After thinking about it briefly, he immediately realized the benefits of this thing.

"Yes! Mr. Gao, your idea is really genius. Use large pulse width to transmit and ensure power. Under the premise of ensuring the center of the signal peak, compress the echo signal pulse width to ensure the accuracy of the target position! Absolutely amazing! Really amazing!"

Mr. Liu's words were not flattery. He really thought that Gao Zhendong's idea was absolutely amazing and it perfectly balanced the issues of power (detection distance) and accuracy.

This thing can even be used to improve single-pulse radar. After all, as long as pulses are used, this problem will exist, and this solution can solve all similar problems well.

Although this radar is a pulse Doppler radar, single-pulse radar is still widely used on missiles. After all, it is cheap.

Gao Zhendong smiled and said, "It can also bring other benefits."

"Mr. Gao, Mr. Gao, please don't say anything yet. Let me think about it. Come on, let's all think about it together." Mr. Liu quickly stopped Gao Zhendong from speaking, not wanting to miss this opportunity to train his troops.

There aren't many opportunities like this for top bosses to lead their troops in training.

(End of this chapter)