Chapter 619 What magnetron? No need for that
To put it simply, pulse Doppler is a way of transmitting and processing radar signals, but phased array is mainly a way of generating signals, but this generation method can bring many other benefits.
There is no contradiction between pulse Doppler technology and phased array. If pulse Doppler is used, phased array cannot be used.
In fact, all phased array radars can use PD technology.
It’s just that these two methods each represent the biggest characteristics of a generation of radar, so they are used to divide radar generations, nothing more.
But the difference between pulse Doppler and phased array is that it is more specific and detailed, so not as many people know about it as phased array.
To give an inappropriate example, everyone knows "birds", but many people may not know what birds such as "Silly Gugu" or "Xiangxiang Chicken" are.
Even in the 21st century, if you ask a non-military fan what a phased array radar is, they may be able to tell you something, but if you ask a non-military fan what a "pulse Doppler radar" is, I'm afraid most of them can't. come out.
As an advanced radar that even Citigroup is still developing, the first PD radar put into use was the one on the F-4J. It only appeared 5 years later. At this time point, it is natural that Mr. Liu does not know about PD radar for the time being. .
"You don't know about Pulse Doppler (PD) radar?"
"I don't know, Mr. Gao, tell me, tell me."
Mr. Liu was immediately interested. Mr. Gao had a lot of good things here. Maybe he was just thinking about it when he had nothing to do. He had lots of wonderful ideas.
In fact, the principle of this radar is easy to understand. Just look at the name and you will know that it is a pulse radar that uses the Doppler principle for detection. However, the benefits of doing so were not something that Mr. Liu could figure out in a short time.
Gao Zhendong had no choice but to introduce the principles and typical applications of PD radar, which uses Doppler ranging pulse radar because it can easily introduce many digital signal processing technologies and benefit from the strong power of digital signals in various signal processing algorithms. It is adaptable and has strong capabilities for back-end processing of radar signals. Before the emergence of phased array radar, PD was the ultimate answer to fighter radar.
Range measurement, speed measurement, guidance, downward vision, downward shooting... it can solve all problems well and the effect is very good.
The phased array radar mentioned here refers to the active phased array. As for the so-called passive phased array, its relationship with the active phased array is not as close as that with the PD radar. It can be regarded as the PD radar with the ultimate development of antenna.
Of course, this is confusing again. The reason is still the same. PD and phased array are the products of two division methods. There are places where they can be integrated with each other.
Therefore, Gao Zhendong has little interest in airborne passive phased arrays. The cost is too high and the benefits are only average.
Of course, not all active phased arrays are good. For example, the little devil, which can only see 37 kilometers, is not as effective as the entire PD.
After listening to Gao Zhendong's general explanation of the principle, Mr. Liu is worthy of being the top airborne fire control radar expert in the country. He has a general understanding of the principle, and he quickly understood that this thing looks good, but...< br>
"Mr. Gao, this thing looks good, but there are many insurmountable obstacles for our current conditions." Mr. Liu was very calm and objective.
Gao Zhendong nodded: "There should be, please tell me. My specific understanding of the current situation is not as deep as yours, so your opinions and experience are very important. Let's see if the current conditions can support it."
"Let's put aside the specific signal processing technology first. Those things can't be seen or touched, and it's hard to explain for a while. Let's look at the hard conditions first."
Signal processing technology is the biggest reason why we have been working on PD for decades but achieved nothing. We simply don’t know what technology, algorithm, and conditions to use to process these signals.
However, this technique cannot be explained in a few words, and how difficult it is is unknown to today’s comrades. It feels like it can be achieved just by writing and drawing on paper.
"I just listened to your introduction, and I feel that the first thing about this thing is that the signal frequency must be accurate, right? Without this basic condition, it is impossible to use the Doppler frequency shift phenomenon to detect targets. Even the frequency is not accurate. Who knows? How much is the frequency shift of the echo signal? ”
Mr. Liu has a strong ability to find problems and is indeed rich in experience. He told a current situation that Gao Zhendong didn't know.
"But the current situation is that we cannot generate a frequency-stable radar signal at all."
? ? ? ? Gao Zhendong looked confused. He couldn't even do this?
"No, not even this? Can't we just produce stable frequency oscillation, frequency modulation, power amplification, and then output it through the antenna?"
Hey, say you don't know, you know everything, say you know, you really don't know, Mr. Liu complained in his heart.
"That's right, Chief Engineer Gao, the generation of stable and accurate oscillation signals has indeed been solved through the phase-locked loop technology you provided, but there is a problem with power amplification."
Only then did he remember that the problem of generating stable and accurate signals had to be solved by others. No wonder they looked like "Why is this so difficult?" Maybe in other people's minds, this was not a big deal.
Thinking of this, Mr. Liu's heart became warm. A stable signal is of great benefit everywhere, even if you don't build a PD radar. Maybe Mr. Gao can help?
"Power amplification?" There are many methods or devices for signal power amplification. These methods or devices are rising alternately and developing in a spiral, and we are now at a special node among them.
"Yes, zoom in, we are using magnetrons now, and they are imported magnetrons."
The magnetron was a commonly used signal amplifier device in early radars. In fact, everyone has used this thing. One of its civilian branches is called a microwave oven.
Mr. Liu's words fully illustrate the seriousness of the problem. We cannot produce this thing ourselves, but this is not the most serious thing.
"There is a problem with the magnetron. The frequency is not accurate, and due to the existence of the resonant cavity, the frequency is low and the bandwidth is small, making it difficult to output high-power signals in the form of pulses." This problem, Mr. Liu said, is the biggest.
This is equivalent to exhausting the two basic principles of PD radar: pulse and Doppler frequency shift. None of these things can be achieved.
In other words, it can't be done now. The magnetron itself is also developing in a spiral. Later, some special types of magnetrons were able to do it, and advanced ship-based passive phased arrays were also used. But that is another It's a story, that thing can't be expected in a short time.
As an expert in the field of radar, Mr. Liu's analysis is still very accurate and in place, and he has considered it well. This is indeed the first obstacle to PD at this stage. There is not even a signal, so it is completely impossible to do it.
Gao Zhendong listened and said with a confused look: "Oh, magnetron, I know. But we don't use magnetrons, we use traveling wave tubes."
Now Mr. Liu was confused.
"What is a traveling wave tube?"
"The traveling wave tube is..." Gao Zhendong was about to say that it was a power amplifier device developed by Citigroup in the late 1950s and early 1960s, but suddenly he remembered something wrong.
Fuck! This cannot be said. This news is not known in the country. It is still unclear whether Lubyanka knows about it. Otherwise, Lao Maozi's current fighter radar will not be like that.
Now Lao Maozi's most advanced Sapphire-21 is still a weakling. In addition to the fact that the radar system is still single pulse, it is also inseparable from the power. If the power is not good, it means that the power amplifier device is naturally not good.
Well, I just have to laugh about it. As for the name of that thing called Citigroup, it’s none of my business. The translation is very similar, which shows that everyone has the same vision. Good design always leads to the same goal by different routes.
Nothing wrong!
Gao Zhendong, who quickly completed his mental construction, wrote the words "traveling wave tube" on the paper and said with a smile: "The traveling wave tube is a new type of signal amplification device I just designed. The basic performance can be summarized in four words : Large gain, accurate frequency, high frequency, wide bandwidth! ”
A traveling wave tube is a device that emits a high-energy electron beam into a signal electromagnetic field and transfers energy to the electromagnetic field through the electron beam, thereby amplifying the signal power.
This thing perfectly meets all the requirements of PD radar for power amplifier devices under existing conditions.
Mr. Liu and his party, who didn't know that Gao Zhendong had already made eight hundred turns in his mind, were filled with surprises when they heard this.
What's surprising is that Chief Engineer Gao can actually do this? Never heard of it before.
Fortunately, there is certainly hope for new devices. Even if we don't engage in PD, this thing will be of great use.
The greater the gain, the greater the transmit power.
Accurate frequency is very helpful for signal processing, even if it is processed by analog circuits.
A high frequency means more accurate ranging, even if the pulse time-difference method is used.
The same goes for high bandwidth, which is great for accuracy.
As for Gao Zhendong's bragging, it is not within their scope of consideration. What kind of joke are you kidding me? How dare you lie to me?
Even if it takes a process from design to implementation, there will be no problems in principle. Such top experts are shameful. If there are small problems, it is better to correct them than not seeing the road.
I want to ask why Mr. Gao hesitated just now. It was probably due to the need for confidentiality, and he decided to reveal a little bit to us after weighing the balance.
No wonder people haven't considered the magnetron at all. This problem doesn't exist there!
It turns out that this is the highest state of knowledge - what's the problem? No problem, I don't know about this problem because I have already crossed over this problem.
"Mr. Gao, that would be great! Let's put this issue aside for now." Now we need Mr. Gao to take out this thing called the traveling wave tube. That means there is something wrong with the skull. Anyway, this subject is not three. If it can be completed in two days and two months, it will be enough if we have the technical resources.
(End of chapter)