Chapter 549 Let's copy homework together
To be honest, the MTI method has great problems in reliably guiding missiles to strike targets such as fighter jets. Since the knowledge of the target's flight status is extremely vague or even nonexistent, it is still quite difficult to guide the missile.

The effect is roughly equivalent to knowing that there is someone in a room, but having no idea who this person is, whether he or she is sitting, lying, walking, or whether he or she is male or female, old or young.

But as an early warning aircraft, it is actually enough to know that there is a high-speed moving target at a certain distance and direction, because what it needs to guide is not missiles or other brainless things, but the fighter jet with a pilot on board!
Call the fighter jets over to take a look. As long as a certain data refresh rate can be guaranteed, the command effect can be basically guaranteed.

Moreover, given this effect, comrades working on radar were completely helpless in the past.

To be honest, if this technology had been available earlier, the P-2V would have been shot down long ago, and there would have been no need to wait for the appearance of the Tu-4T.

"Chief Engineer Gao, this is a great effect. As long as we can achieve this effect, our fighter jets at various frontline airports will have a greater role to play. It can be said that the low-altitude blind spot and ground clutter problems of ground-based radars have been solved to a large extent."

Another comrade who worked on radar also said with a smile: "Mr. Gao, you may be standing high and seeing far, and you think this method is not perfect enough, but at this stage, this is enough for us."

Gao Zhendong also realized that he was still carving a boat to look for a sword, and he was carving a boat decades later to look for a sword decades ago, which was really too abstract.

He smiled and said, "Okay, to be honest, I'm not an expert in radar, so this is probably all I can provide. The rest may depend on you guys to figure out a solution."

"Mr. Gao, please don't say that. You are more professional in radar than us, especially in the principles and general directions, which are the key to solving major problems."

"Don't worry. What we lack is this kind of theoretical guidance that can get to the point and clear the fog. Once we clear this fog, we will always be able to find a way to achieve it, at least partially."

Chief Engineer Gao, it's pointless to be too modest. If you keep saying that, we will lose face.

Then Gao Zhendong proved with practical actions that he was really being humble, at least that was the case in their eyes.

"Although I can't help you much, I can help you a little with phase and frequency detection if you don't have any ideas for the time being."

These words reminded several comrades working on radar that they had never come into contact with things like phase detectors, or had not studied them in depth. They could copy others, but it was beyond their ability to come up with a new and targeted thing.

"Ah? You've also done research on this? That's great, Mr. Gao. I hope you can give me some advice on this as well."

Speaking of this, Gao Zhendong is no longer sleepy, because this was the content of his major in his previous life. Although he studied automation, he has a deep background in communications and has dealt with signals many times.

"There is a circuit called an analog multiplier. Have you ever come across one? If you have, then this circuit can be used in this matter. If not, let's have a discussion now."

Gao Zhendong didn't know how well they had mastered the analog multiplier, an important circuit used for analog signal processing, but he estimated that the situation might not be optimistic. Otherwise, in his previous life, he would not have seen the first-generation early warning aircraft, which had been in development for so many years, helpless in the face of the clutter problem and thus discontinued.

In short, this era lacks everything in terms of technology, so it is not surprising that this is also lacking.

An analog multiplier, a circuit composed of amplifying devices such as triodes, can directly complete the multiplication operation of two analog quantities, which may be voltage or current.

In the signal processing process, amplitude modulation, detection, mixing, frequency multiplication, frequency detection, phase detection and other processes are actually the multiplication of two signals or the process containing multiplication operations.

The analog multiplier that Gao Zhendong used in his previous life was already an integrated circuit device, but this does not mean that it cannot be built using transistors. Before this circuit was integrated, it was actually built with transistors. Gao Zhendong built it himself when doing experiments and projects.

"Multiplier? Mr. Gao, I've read the latest textbooks on computers. Even computers now only have adders. Multiplication is achieved through addition, and it's a digital circuit. Isn't this different from the type of signal we have now? And digitizing radar signals is inherently a rather troublesome task."

This is the current technological environment. Everything is lacking and everything is relatively primitive. The entire process of radar signal processing is basically analog. However, the multiplier that Gao Zhendong proposed to them is exactly analog, which just meets the current situation.

What this comrade said is probably the content of the general computer architecture that Gao Zhendong himself came up with. It’s true that they are really not behind in learning, but the content of this book and what Gao Zhendong said are two different things.

As for digital hardware multipliers, they actually exist in the future, but they are rare in general-purpose computers. In another type of device, they are the core.

Gao Zhendong smiled and said, "That's OK. This multiplier circuit is originally used to process analog signals, so it can save the process of digital-to-analog conversion."

Gao Zhendong didn't say a word - guess why I specifically mentioned this to you?
Several comrades were surprised. There is such a good thing? Gao Zhendong first introduced the general situation and use of the analog multiplier. After listening to Gao Zhendong's introduction, a group of comrades exclaimed that they had found a treasure.

This thing is not only used in this place, with the current radar and signal processing, it can be used in many places.

A group of people stared at Gao Zhendong with sparkling eyes - where is the picture? There should be a picture here!

As a mature instructor, Gao Zhendong had already learned to draw the pictures himself. He took out a pen and paper and started drawing.

The circuit schematic of the analog multiplier is not too complicated, but it is not simple either. It took Gao Zhendong some time to finish drawing it.

A group of comrades working on radar copied without saying a word!

Although they are all engaged in radar, they are the best from different units, otherwise they would not be invited to this seminar. Since they are from different units, it is not convenient for anyone to take Gao Zhendong's paper away, and others will not allow them to do so. Well, copy it!

"Don't block it, don't block it..."

"Tilt your head a little, it's blocking the picture..."

"Don't pick it, it's too far away and I can't see clearly..."

Gao Zhendong poured a glass of water and happily watched his comrades copying the homework meticulously. On this kind of schematic diagram, the sizes of resistors, capacitors, inductors and other components are basically not marked, and they are drawn relatively casually. If you are not careful, you may make mistakes in copying.

In his previous life, any one of these people in front of him would have been someone he looked up to. Now, looking at them piled up together to copy his homework, Gao Zhendong felt quite happy.

When the copying was almost done, one of the comrades exclaimed: "Ah, I seem to have seen a similar circuit before. In the Russian radar, in a large circuit, there should be a similar small piece, but we don't know what this thing is used for, and we can't even clearly define its boundaries."

It should be said that this comrade is also very remarkable. He is familiar with the entire radar back-end processing circuit.

Another comrade was also in a very good mood and joked: "Before, I knew the facts, but I didn't even know what it was used for, let alone changing it. Now I know why it is used and can really use it."

This is the difference between imitation and research. When imitating, you don’t know why, you just copy it, as long as you get the result in the end. But if you want to improve, it will be very difficult, and research is another matter.

Gao Zhendong explained to the comrades the principle of the circuit, device selection, function of each component, etc., based on the circuit diagram. While listening, several comrades praised it highly, using words such as "good", "wonderful", and "excellent".

When Gao Zhendong finished speaking, several comrades looked at each other and said to Gao Zhendong solemnly: "Thank you, Chief Engineer Gao!"

Gao Zhendong shook his head and said, "I should thank you." Only he understood what he meant by this.

Several comrades reviewed what they had just learned. Gao Zhendong had taught them everything he could, from ideas, principles, system structure to core components. It would be too unreasonable if they could not come up with something that could achieve dynamic target indication.

Some comrades have already started to think about how to implement this problem in a specific way.

Someone who thought faster suddenly realized: "Hey, this circuit can also multiply the frequency?"

Radar signals require a high-precision signal source, which means that the frequency of the electromagnetic wave cannot float around, and parameters such as duty cycle must also be very well controlled. Otherwise, if it itself is not accurate, then the subsequent ones will also be biased, or even deteriorate to the point of being unusable.

To give a similar example, the reason why the accuracy of an electronic watch that costs a few dollars can far surpass all mechanical watches regardless of their price is that its crystal oscillator has a high frequency and good stability. No matter how precise a mechanical watch is, a swing frequency of 5Hz is considered very high, and 8Hz is top-notch. An electronic watch that costs a few dollars basically starts at 32kHz, and that's not even considering the stability issue. Otherwise, a mechanical watch would be even more embarrassing.

As for a high-precision signal source, before the electromagnetic wave is amplified, it must first have an oscillator device with good enough accuracy and high enough frequency.

High-frequency signals are generally obtained by multiplying low-frequency signals. This thing seems simple in later generations, with frequencies of several G and it is very cheap. But for us today, it is still not simple.

(End of this chapter)