The faces of the other people standing behind Guo Lin were also very exciting.

Intuitively, they don't believe that anyone can directly determine the design principle of a circuit in such a short period of time.

The main thing is that it's too fast.

Those who can enter the 14th Institute of Electrical Engineering have some ability in circuit design.

But when you get a board that you've never touched before, that is already broken, and that has a lot of new components, it will take you a few days to analyze it anyway.

If you are facing this kind of military circuit board with a lot of non-standard parts and electromagnetic shielding packaging, you may have to collect some materials.

After all, in this era, the transmission of information is really not smooth.

And Chang Haonan's performance gave them the first feeling as if it was ......

I'm looking at a circuit board that's already familiar.

In this way, many intermediate processes can be omitted, and as long as some typical characteristics are found, they can be directly judged.

But how is this possible?

This pod should have been secretly produced by Raytheon, and from the time it was seized to the time it was secretly transported back to Jinling, the number of people in the know was also controlled within a very limited range.

Chang Haonan, who only arrived at the 14th Institute today, even if he heard Guo Lin say some words before, he never had the opportunity to see the real thing.

But on the other hand, the person who said this was Chang Haonan after all.

And Xu Yang next to him did not object.

If it were someone else who was so critical of his judgment, it would definitely be considered a verbal statement.

But the situation is not the same for the two.

Although algorithm theory, software programs, and circuit hardware can be regarded as three different fields, they are all under the category of control engineering.

After all, they wrote papers that were on the cover of IEEE Transactions on Automatic Control.

In short...... It's quite tangled.

It should be said that these people did not guess wrong.

Chang Haonan can use a microscope to see the working principle of the jamming device, naturally not because he has a writing wheel eye, but because he has guessed before, and now it is just a verification.

Or more precisely, it's just to add some rationality to your own judgment, otherwise it will be difficult for others to believe it if you just glance at it and say the result directly.

In fact, he also took advantage of the times.

In later generations, this kind of DDS could be integrated into an integrated circuit with a side length of no more than two centimeters, rather than such a palm-sized circuit board in front of it, which is by no means something that can be seen with an ordinary optical microscope.

Of course, it still seems that it is a bit beyond Guo Lin's ability to accept now.

But it doesn't matter, it can be explained.

Just now he just relied on words to describe it, it was really not intuitive enough, and everyone else was not mentally prepared, I'm afraid they didn't listen to it completely, and it was normal to be skeptical.

"In fact, although this board looks very complicated, the core principle is not difficult to understand, you are just frightened by the origin and packaging specifications of this thing."

Chang Haonan took the circuit board off the stage of the microscope and gently put it back in place:

"Is there a blackboard, I'll draw the schematic, and it's easy to understand."

Guo Lin is the most convinced of Chang Haonan among the people except Xu Yang, and he has just listened to the judgment given by the latter in full, but because the speed of speech is too fast, he still doesn't fully understand, and now he naturally wants to seize this opportunity.

"Yes, yes, right next door."

More than a dozen people swooped into a small conference room next to it.

Only Xu Yang didn't follow immediately.

After explaining to Chang Haonan in a whisper, she picked up a few other pieces of circuit board and observed them alone.

……

Sometimes Chang Haonan wonders whether the blackboards used by the enterprises under the system of the Science and Technology Commission are centrally purchased.

In short, this room, this blackboard and this chalk made him dream back to 601.

"Although this direct digital frequency synthesis may seem like a bluffing new concept, we should all be able to understand the workflow."

Chang Haonan said and drew a simple block diagram on the blackboard:

"This is what I look like after removing all the non-core components on that board."

He didn't even need to repeat his previous instructions, and the 14 engineers gathered around the blackboard looked aware.

That's where peeling back the cocoons comes in.

Just like some math problems, I couldn't find the idea when I did it for the first time, but after reading the answer or listening to the teacher explain it once, I thought it was very simple.

"So the purpose of this thing is to do a more efficient carrier frequency shift?"

It didn't take long for someone to figure out some of the important links.

"That's right, the DDS (Direct Digital Synthesizer) itself is just one part of a field-programmable gate array (FPGA)."

"Perhaps due to the issue of electromagnetic compatibility and stability, this FPGA is designed to be very large, and even three layers of circuit boards are stacked to achieve full functionality."

Chang Haonan picked up the chalk again, added a dotted box around the diagram he had just drawn, wrote the three letters DDS in it, and then drew a few other components on the blackboard and connected them into a larger range of circuits.

"I see!"

Zhou Lin, who was standing closest to the blackboard, was particularly excited:

"The input radar RF signal is mixed with the system local oscillator, and downconverted to an intermediate frequency signal through bandpass filtering (BPF); After the intermediate frequency analog signal is mixed with accurate local oscillator frequency and low-pass filtering (LPF), the baseband analog signal is obtained. Under the control of the sampling clock, the ADC realizes analog-to-digital conversion, and the output digital signal is stored in RAM. In the forwarding process, the readout data is filtered by DAC and low-pass and then reconstructed into a baseband analog signal. After the reconstructed signal is mixed with the local oscillator of the system, the upconversion is a radio frequency interference signal ......"

“……”

At the beginning, Guo Lin's analysis was still very smooth, but later, he realized that there seemed to be something wrong:

"Feeling...... Feel like there's a module that isn't working? ”

Chang Haonan nodded:

"Hmm...... This should be a conversion module used as an orthogonal downconversion processing, which is used to convert one intermediate frequency signal into two quadrature components, as for the specific algorithm, and the ultimate purpose of doing so, it still has to wait for Dr. Xu to analyze it, but if I have to guess, it may be to increase the bandwidth in the case of low sampling rate and ensure the interference effect of low-frequency radar......"

As soon as the words fell, Xu Yang, who was wearing a lab coat and hadn't even taken off his goggles, pushed the door in from the outside and came to Chang Haonan:

"This should be an orthogonal dual-channel DRFM that can handle two quadrature components at the same time, and the homeopathic bandwidth can be doubled with the same sampling rate......"

As soon as she finished speaking, she noticed that the room full of people were looking at her side with a strange gaze.

Or more accurately, look at the little blackboard behind you.

So Xu Yang subconsciously turned around:

"Yo, so you've seen it too?"

"Not really."

Chang Haonan waved his hand and put the chalk on the table next to him:

"I reasoned it."

An understatement made the whole room quiet for a moment.

"Okay."

After a few seconds, Xu Yang nodded with a complicated mentality:

"Anyway, there's one thing I don't understand."

"According to this schematic, there is no need for the pod to be designed to be so bulky, it can be about 6 meters long, so that some ordinary tactical aircraft can also be mounted normally."

(End of chapter)