Chapter 723 Matched Filtering
"Boss Gao, I remember now. This method can improve the multi-target processing capability! Once the pulse width is compressed, it means that the echo signals of two adjacent targets can be clearly distinguished. In this way, the original multi-target processing capability is also improved."

Gao Zhendong smiled: "Yeah, yes, it does have this effect."

In fact, this is the root cause of the benefit brought by the improvement of resolution. If the resolution is low, the error will be large, and it will naturally be impossible to distinguish between two adjacent signals, and vice versa.

Mr. Liu's thoughts were deeper than those of his comrades.

"Chief Engineer Gao, can this pulse compression be used to pick out the echo signal from the white noise? Can it greatly improve the system's ability to combat the errors caused by white noise?"

Gao Zhendong nodded, saying, "Right! This is also a very important point. White noise is very uniform, but the amplitude of the compressed signal will greatly exceed that of the white noise, so it will naturally be picked out from the white noise."

There is an interesting thing about radar signals. Sometimes the amplitude of white noise seems to be larger than that of the echo signal, as if they cannot be separated at all. However, with appropriate digital signal processing technology, the echo signal can be extracted from the white noise and processed separately.

In layman's terms, the energy of the echo signal is certain, and the pulse width is compressed, which means that the amplitude is increased and an obvious signal peak will appear, which is easy to handle.

"Yes! This idea is really amazing, and it can have this effect."

"Well, the benefits just mentioned were incidental, but this benefit is separate."

"Pulse compression! Great, I'll do it when I get back."

"..."

I said I would do it when I got back, but how? This question is actually not as simple as the previous one.

There are many solutions that seem good in principle, but once they enter engineering practice, you will find that they are not as simple as you imagined.

"The question is, how to compress it?" Some comrades raised this question, which was like pouring a bucket of cold water on the heads of the comrades who were just in high spirits.

We all know that pulse compression is good, but how to compress pulses?

This thing is not like a ball of cotton that can be compressed into a piece by squeezing it. It is invisible and intangible.

Everyone began to think hard. Although Gao Zhendong looked smiling and confident, and thought he had a solution, everyone still wondered if they could come up with a solution themselves. After all, they couldn't wait to be fed everything, and Chief Engineer Gao had fed them enough.

But they thought about it for a long time and still couldn't come up with a good solution. Use analog devices for compression? Or use digital signal processing? They had no idea.

"Chief Engineer Gao, please tell us about this. We have no idea about this for the moment." Mr. Liu gave up quickly. It was not worth wasting time here.

As everyone expected, Gao Zhendong was indeed confident about this matter.

"For pulse compression, a method called matched filter is used."

After saying that, Gao Zhendong walked to the blackboard and picked up the chalk.

Chief Engineer Gao is going to draw a circuit diagram! Everyone is very excited. What are you doing? Get ready to take notes! Everyone opens their notebooks.

But contrary to everyone's expectations, Gao Zhendong did not draw a circuit diagram, but wrote mathematical formulas on the blackboard, explaining them as he spoke.

"...here, the output signal is composed of two parts: signal and noise..."

"…by Fourier transforming and then convolving the signal in the time domain…"

"...It can be seen that the signal energy is the accumulation of the square of the modulus of the spectrum expression..."

"...according to Schwarz's inequality...we will eventually find that after processing, the signal-to-noise ratio has nothing to do with the waveform, but only with the ratio between the signal energy and the white noise intensity..."

Some comrades were fascinated by what they heard, while others basically did not understand anything.

Although there is not much mathematics involved, after reading this series of things, some people still feel like they are listening to a mystery.

But those comrades who understood it felt like they had found a treasure.

Finally, Gao Zhendong threw away the chalk and said, "Well, that's roughly the principle. This is how matched filtering works. I wonder if you understand it."

Even if comrades don’t understand, they are too embarrassed to say, “Mr. Gao, please explain it again.” How can they be so confident?

Fortunately, there are always some who understand, and some who partially understand. "Mr. Gao, how is the specific circuit design of the matched filter designed?" A comrade was anxious and wanted to know the final result.

Hearing this question, Gao Zhendong was at a loss for words. He just looked at Mr. Liu with a smile and said, "This... is your person, you solve it."

Mr. Liu had a look of disappointment on his face: "Didn't we just finish what we said? What other circuits do you need?"

Gao Zhendong then smiled and said, "This matched filter is actually a digital filter at its core. You send the sampled signal to the digital signal processor and calculate it according to the mathematical principles and processing methods mentioned earlier. No special circuit is needed."

This is the amazing thing about digital signal processing technology. As long as it samples the signal with a certain accuracy, the rest is just pure mathematical calculation, and no additional circuits are needed.

Therefore, the weight of the Russian "Flanker" anti-aircraft weapon is almost calculated in tons due to the inadequate digital signal processing technology, but the Citigroup's PD radar of the same period only needs to be calculated in hundreds of kilograms.

The comrade who asked this question was embarrassed, but the other comrades were secretly shocked. Chief Engineer Gao's method was really amazing!

Not only can it solve the problem, but more importantly, it can greatly simplify the system complexity, reduce the system weight, improve the radar adaptability, and it is foreseeable that reliability and maintainability will also be greatly increased.

Mr. Liu asked Gao Zhendong about some of the things he didn't understand when Gao Zhendong explained it just now. After listening, he said cheerfully: "Chief Engineer Gao, we will stop here today. Thank you so much. Your words have completely solved the problem of detection distance and accuracy of our pulse radar. Let's go back and digest it first. If we have any new questions, we will come to ask you again."

For them, the biggest obstacle, the contradiction between detection distance and accuracy, was solved overnight. They have no interest in other problems, or have not encountered them yet. The most urgent task now is to go back and apply the technology given by Gao Zhendong to actual projects. This thing seems to be very simple when Gao Zhendong talks about it, but if they want to use it well, they still need to spend a lot of effort.

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

Gao Zhendong smiled and nodded: "You are welcome to come and communicate anytime."
-
The Gallic rooster, Le Goff, walked towards Mr. Senna's office with a note in his hand and a happy look on his face. This time, the Oriental man's request would probably make Mr. Senna very happy.

"Mr. Senna, the Orientals have made a somewhat special request to us."

After saying that, he handed the note in his hand to Senna.

"What do they want to show off to us again?" Mr. Senna muttered as he took the document.

After opening the document and taking a closer look, Senna's eyes showed joy, just as Le Goff had expected.

"Hahahaha! They finally make some serious demands on us for high-tech products." Senna felt like he was "the emancipated serfs singing."

Apart from some military technologies for exchange, the Orientals seemed to have no interest in the high-tech products provided by their side. Over the past year or so, the other side treated them like farmers, which made Mr. Senna very dissatisfied.

This time, for some unknown reason, the other party seemed to have come to their senses and finally put forward a purchase demand that clearly represented high-tech.

But the situation seemed to be somewhat different from what he had expected.

"Rifamycin? They said it's from Leather Shoe Country? Damn it, they even like things from Leather Shoe Country, why don't they consider buying something from us?"

"Mr. Senna, I have verified that we have a certain influence on rifamycin, or it is reasonable for you to regard it as ours." Le Goff shrugged.

"Oh? My dear Le Goff, tell me in detail." After hearing Le Goff's words, Mr. Senna's expression looked a little better.

"The earliest samples of this antibiotic, which is still under research, came from the soil in our pine forest. Therefore, we can exert a certain influence on the shoemakers with this drug. Although this antibiotic is still in the experimental stage, their patent protection has been completed, so they are very happy to cooperate with the sale of a certain number of samples or experimental drugs. After all, it is a good thing to have someone to experiment with them, and no matter what others use it for, they have to buy it from the shoemakers, and they can make money."

Le Goff was very well prepared, and he even had a pretty good grasp of the shoe guy's attitude.

After hearing what Le Goff said, Senna's expression softened a little. This could barely be considered as something from his own country. After all, it came from the land of Gaul.

"So what do you think the Orientals want to do by taking this kind of thing back?"

"I think it's used to treat some disease. The health situation there is very poor," Le Goff said with a smile.

"Le Goff, your joke is not funny at all. The sanitary conditions here are not that good. We have no right to make fun of others."

The Seine, like the Thames, is famous for its pollution, and the Seine is even more polluted.

"Well... I think you're right, my sir. But do you think this deal can be done?"

"Do it, why not? They can only buy through us. There is money to be made, so why give up? And if you are more straightforward in medicine, I think you can win more favor from Oriental people." Senna's mind was very clear.

(End of this chapter)