Chapter 270 Passive Radar Detection
Although Chang Haonan had reduced the length of the message as much as possible, he still ended up writing about two to three thousand words.
And almost every sentence must be carefully considered.
After all, many of the details come from the memories of previous lives, so there is definitely no way to write them down directly.
In order to increase his persuasiveness, he had to say that the maximum takeoff weight of the An-70 is only three-quarters of the IL-76MF, making it an easier reference in the future.
Fortunately, the core of this proposal, namely Antonov's lack of money, is easy to explain.
Just say it’s a guess.
Everyone can guess it anyway.
It's just that Chang Haonan knew very clearly how short of money they were, so he dared to make such a bold plan.
When this operation was completed and the telegram was handed over to the director of the confidential office who had been waiting outside, the entire afternoon had passed, and it happened to be dinner time.
Standing in the cool breeze of early April, the tiredness caused by being bored in the confidential room for an afternoon disappeared in an instant.
Chang Haonan remembered that a few hours ago, he decided to have a good meal.
After hesitating for a moment, I felt that it seemed a bit outrageous to eat alone.
After receiving many high bonuses (by the standards of this era) and eating and drinking without having to spend his own money, he can now be considered a wealthy man.
Finally, we changed direction and prepared to go back and call in the comrades from the 14th Institute who came to Yan Liang on a business trip, and of course Xu Yang.
As for the name, it was just to boost morale and prepare for the next round of electronic warfare pod testing. Anyway, if we count the days, Jinling should also be shipping things over.
But when he pushed open the door of the research room, he found that everyone inside was already beaming with joy, as if they knew in advance that someone was going to treat them tonight.
"Everyone, how about we go out for dinner tonight?"
Although he was a little curious, Chang Haonan, who was in a good mood, decided to talk about the important things first.
Then he received a dozen looks with the same confusion and surprise:
"Chang Gong, didn't you go out in the afternoon?"
"Yes."
Chang Haonan nodded.
"Then how do you know that Guo Gong has thought of a good idea?"
"Yes, Dr. Xu also thinks his idea is okay."
"And we simulated it on the previous circuit, and it is completely feasible."
"..."
Everyone said something to me, and Chang Haonan finally understood what this should be. It's a mistake.
"So, what's the idea?"
He took off the scarf around his neck and hung it next to him, walked to Guo Lin and asked.
Lin Shikuan of Institute 601 had already become an independent digital design engineer under the guidance of him and Yao Mengna. He solved many problems for the aviation industry when Chang Haonan was unable to do anything else.
It would be nice if it could be reproduced in the 14th Institute of Electrical Engineering.
“Ahem——”
Hearing Chang Haonan’s question, Guo Lin instantly became excited.
After so long, it’s finally my turn to show off.
He instantly switched to sitting upright.
Unfortunately, there was no one with enough eyesight to hand over a pen and paper, so I had to take it from the table next to me, which reduced the B level of this set of actions a lot.
"I thought of a way to specifically confirm the opponent's position by detecting the radar signal emitted by the enemy."
"Specific position? Including the distance?"
Chang Haonan became interested instantly.
The technology of passive tracking of radar radiation sources has been used in Suppressed Air Defense Operations (SEAD) since the Vietnam War. However, in fact, until the mid-1990s, this detection could only obtain the target's orientation information, but could not Directly determine the distance between ourselves and the enemy.
Of course, for general anti-radiation missiles and electronic interference, this is not a problem, because even if I don’t know the target distance, as long as I always follow the direction of the radar wave, I will always get it. The signal source can be found. However, with the continuous advancement of air defense technology, the signal detectability of the radar itself is constantly decreasing, and the radar emission source can even work while moving at high speed. This results in the traditional single-station passive positioning being unable to continuously and stably track the signal emitted by the radiation source. As a result, a huge registration deviation occurred, and the efficiency of hard-killing radars through the combination of passive detection and anti-radiation missiles declined sharply in the 1990s.
For example, the AGM88 Hamm could kill almost indiscriminately in 1982, but in 1999, facing the southern army with weaker resistance, the hit rate dropped to a horrific level.
This situation has also given rise to the third generation of electronic warfare aircraft represented by EA18G.
Now Guo Lin said that he could solve this problem, which really shocked Chang Haonan.
“Uh...that’s not possible.”
Guo Lin scratched his head awkwardly:
“But radar signals can be sorted in complex electromagnetic environments. , effectively identifying the most threatening one is at least much better than our existing method, which can only intermittently obtain the target signal."
"Oh..."
This answer slightly dampened Chang Haonan's newly heightened thirst for knowledge.
But it’s okay, at least it’s an improvement:
“Tell me about it.”
“That’s right, a few years ago, someone proposed a method based on The transformation algorithm of harmonic suppression of autocorrelation function can transform the pulse signal TOA from the time domain to the PRI domain, and effectively suppress the harmonics of the real PRI of the pulse signal. That is to say, if we assume that the TOA of each pulse is ideal Unit impact function δ..."
"Wait a minute, wait a minute."
Chang Haonan directly stopped Guo Lin's introduction:
"I know PRI, we can go directly to the next paragraph."
"Uh... okay."
< br>Guo Lin next to him also realized that he was a little carried away and actually tried to introduce this basic knowledge to the other party, so he quickly collected his thoughts and continued:
"In short, the PRI algorithm follows the pulse TOA of the PRI signal jitter. increases, the error of the pulse phase factor will also continue to increase. In addition, the accumulated pulses of the jitter signal will be dispersed into different PRI boxes. ”
"So I thought that this algorithm can be improved in two ways. One is to introduce the concept of a variable time starting point to avoid errors caused by phase factors, and the other is to use overlapping PRI boxes for anti-shake processing... In short, The process I designed probably looks like this.”
He was obviously prepared and took out a beautifully drawn process chart from underneath and handed it to Chang Haonan.
At this time, the latter had forgotten what he was thinking about going to eat on the way. He picked up the piece of paper and lowered his head to think.
After watching motionless for more than ten minutes, Chang Haonan finally raised his head again and looked at Guo Lin next to him:
"The idea is very complete. Can a person think of this level? Pretty good.”
"I'm not the only one. Other comrades have also helped me correct some things these days. Fortunately, judging from the test results, the repeated frequencies of the three groups of signals can be identified simultaneously through an improved PRI transformation calculation, and There are no false PRI peaks, and the processing capabilities for strong jitter signals have been greatly improved.”
Guo Lin was a little embarrassed and smoothed his hair.
He intentionally did not consult Xu Yang and Chang Haonan before this afternoon, just to see if he could figure this idea out at his own level.
“The idea is very good.”
“However, just identifying the target signal or using electronic interference for soft kill may not be enough in the battles facing the new century. .”
"I have a straightforward personality and like to cut grass and roots. It is always a hidden danger if I don't blow up the radar on the opposite side."
Chang Haonan put down the paper in his hand:
"But then again, your idea It inspired me.”
“On the basis of being able to effectively sort radar signals in complex environments, there is no need to focus on anti-radiation operations... We should be able to use some means. Let the aircraft use passive radar to directly have the ability to detect and track targets. I mean, even if the radar is not turned on, of course it would be better if the radar is turned on."
"Ah? ”
Guo Lin's expression became a little stiff.
Chang Haonan also noticed that the other party seemed to be a little bit shocked:
“However, your algorithm still has academic value. If it is published, it may be a bit difficult to publish it in professional journals on control. But there is still hope for journals that intersect aerospace and control disciplines, such as IEEE Transactions, Aerospace and Electronic Systems. "
"Is it really okay to publish this? "
As an employee of the 14th Institute. , this sensitivity is still there.
"No problem. The PRI algorithm itself is not a new thing, and it is quite basic research. Instead of holding it in your own hands, it is better to send it out so that more people can see it."
"Implement it into specific models. The key is the part I just thought of."
"..."
Guo Lin was hit even harder now.
(End of this chapter)