Chapter 885 Optically Controlled Phased Array Radar
For back-to-back double-sided array "camera scans", the difference between the 120° field of view and the 150° field of view may not be particularly big.
After all, all it takes is moving the plate a little.
But for small and medium-sized early warning aircraft using fixed double-sided arrays, that is, balance beams or T-shaped antennas, the meaning is completely different.
This is equivalent to reducing the detection blind zone to half of its original size.
More importantly, it can reduce the possibility of the AWACS being forced to adjust its route in order to change the detection area.
As a technician, Wang Xiaomo was naturally very happy to find that someone was interested in the field he was researching, so he immediately gave a more detailed explanation:
"You know, the so-called phased array radar is actually an electronically controlled scanning using a phase shifter to control the beam, replacing the mechanical scanning that used a mechanical structure to control the rotation of the antenna array, so it can achieve a very high target refresh rate."
"However, at this point, we have only solved the problem of target refresh rate. If the phased array radar wants to obtain better detection capabilities, it also needs to have a large enough instantaneous bandwidth and scanning angle."
"But these two attributes are contradictory on the same radar. The greater the pointing deviation of the radar, the smaller the available instantaneous bandwidth. Generally speaking, the impact of the instantaneous bandwidth is ±45°, which is within the 90° pointing range. Not big, so shipborne phased array radars that are not sensitive to weight and volume, such as the American Aegis and the Sea Star system we are developing, all use 4-sided arrays to ensure the best detection results. "
“If no wide-angle scanning technology is used, then when the array normal lobe width is 2° and the field of view reaches ±60°, which is a 120° pointing range, the allowed relative signal instantaneous bandwidth is only 1%, and the antenna physics The larger the size, the greater the demand for relative signal instantaneous bandwidth, which is completely unacceptable for high-resolution detection.”
"Therefore, the vast majority of phased array radars put into use use real-time delay lines in each transceiver channel to compensate for the spatial path difference between antenna units."
"The ideal situation is to use a delay line on each unit of the phased array antenna, but this means tens of kilometers of extra cables for a phased array radar with thousands of transmitting units. On the one hand, The cost and size are unacceptable. On the other hand, such high-density cables will also produce very strong interference. "
"So the current common practice is to divide the phased array antenna into a series of sub-arrays, continue to use phase shifters for the units inside the sub-arrays, and use real-time delay lines between sub-arrays."
“However, for large phased array antennas, dividing the sub-arrays will result in many sub-array-level grating lobes in the field of view, causing the antenna side lobes to increase. In short, the final result is the current 120° scanning angle. Single-sided antenna, all aspects of performance are acceptable..."
"..."
After all, he is a senior academician who has been immersed in the field of radar for most of his life, and his explanations are simple and profound.
Even Zhang Hongbiao who was following him felt that he understood everything.
As for Chang Haonan...
In fact, when Wang Xiaomo had just spoken a few sentences, he had already remembered that Huo Penghua had mentioned the same term during a seminar some time ago.
A certain length of wire is also used to compensate for the phase difference between different signals.
But in the end...
Well, it’s not the end yet.
However, at least for now it has been replaced by optical fiber.
Of course, in that laser processing equipment, the main purpose of replacing optical fibers is simply to reduce signal delay.
Compensating the signal phase difference is just a matter of course.
You're already here, let's just put it on together.
But it seems that similar ideas can be introduced to radar——
This time, it's not just about replacing cables with fiber optics.
Instead, a programmable optical delay unit combined with a microwave photon phase shifter is used to form a light beam forming network, which fully realizes phase control of the antenna array elements by photoelectric signals...
Chang Haonan's thinking continued for a long time, until a sudden cold wind interrupted his thoughts.
However, this is enough.
"Comrade Haonan, what new idea did you just...think of?"
Wang Xiaomo asked with concern on his face.
He didn't speculate on the specific technical aspects of the radar. After all, although Chang Haonan had demonstrated a background in signal processing, he had almost never been involved in the research and development of the radar itself.
So I just thought that Chang Haonan had some new ideas about the follow-up development route of the early warning aircraft.
"There is some inspiration, but it's not perfect yet..."
Chang Haonan nodded:
"After I go back this time, I will calculate it on a theoretical level. If the result is more optimistic, I will discuss it with you, Academician Wang."
He can still distinguish the priorities of things.
Wang Xiaomo is an academician of the Academy of Engineering and has basically spent his career solving problems at the engineering application level.
Seeing that tomorrow is the delivery ceremony, telling Wang Xiaomo something that cannot even be called an idea, but can only be regarded as an idea at best, will not bring any real help except making the other party feel like a cat scratching his heart.
It is better to refine the idea and at least come up with a complete theoretical calculation result before discussing this matter.
However, Wang Xiaomo guessed some clues from the words in Chang Haonan's answer.
Since the latter mentioned "theoretical calculation", it is obvious that the inspiration just mentioned is not a big thing like the development route of the early warning aircraft.
It is related to specific technology.
As for what specific technology it is...
Wang Xiaomo certainly doesn't know yet.
However, since Chang Haonan didn't say it directly, he didn't intend to force the question.
Sometimes, it might be better to retain some curiosity...
The two who predicted each other's prediction looked at each other tacitly, then temporarily ended the topic and walked forward side by side.
Only Zhang Hongbiao and Liang Shaoxiu, who were confused, were left in the cold wind...
...
The next day.
March 25, 9 am.
The delivery ceremony started on time.
As for the process, it was naturally the same as before.
First, several leaders including Zhang Hongbiao spoke.
Then the R&D personnel and pilot representatives expressed their opinions.
Then the plane with the big red flower was dragged from a little further away to the vicinity of the ceremony site for a group photo.
Done.
The person who led the team to pick up the plane was even an old acquaintance of Chang Haonan.
Shen Tao.
However, this was not very surprising.
The 4th Regiment of the 2nd Division of the Naval Aviation is still the only full-time special aircraft unit in the entire Naval Aviation and even the entire army, and it is also the unit with the most experience in serving the three types of Y-8 platforms.
Because the range of the airtight Y-8 is really amazing, the genuine transport aircraft units do not need these later improved models, and most of the production capacity has become a special aircraft platform.
"Deputy Division Commander Shen."
Chang Haonan had noticed him when he was on the stage just now. After the ceremony, he immediately walked up and said hello:
"Long time no see."
The last time they met was at the 50th anniversary National Day military parade.
A year and a half later, Shen Tao already had a star on his shoulder.
His position was also promoted from the head of the 4th Regiment of the Naval Aviation to the deputy commander of the 2nd Division.
However, due to the loose age limit for large aircraft pilots, he still served as the captain in the 4th Regiment.
Shen Tao was concentrating on the KJ-200, but after hearing Chang Haonan's voice, he realized that there was someone behind him, so he turned around.
"Mr. Chang?"
I don't know if it was Chang Haonan's illusion, but Shen Tao's tone didn't seem to be too excited about receiving the new model:
"Hello, hello..."
"I feel that Deputy Commander Shen is not very interested..."
Chang Haonan said half-jokingly, thinking that the other party was a little tired after working for too long.
This situation also occurs after he works for a long time.
He has no interest in anything.
However, Shen Tao's reaction was to pull the corners of his mouth slightly, trying to put on an excited expression.
The result failed.
So he had to sigh:
"It's just some trivial matters at the organizational level of the HNA, no need to mention it..."
Hearing the other party say this, Chang Haonan suddenly remembered something -
In 2003 in the previous life, the unified naval aviation command had been abolished.
From then until 2016, the naval aviation divisions were simultaneously under the jurisdiction of the Aviation Department under the Navy Command, the Aviation Technical Support Department under the Navy Equipment Department, and the three major fleets.
From the perspective of hindsight, this has had a very negative impact on the organizational construction and equipment training level of the naval aviation.
And it is normal for such a big move to be leaked one or two years in advance.
Shen Tao is probably worried about this matter.
However, this kind of issue involving the construction of the military system is quite sensitive, and Chang Haonan knows that he can't intervene directly.
So, he had to prepare to talk to the other party about something else.
But before he could speak, Shen Tao took the initiative to change the topic:
"Anyway, I still have to thank your aviation technology department for providing more advanced equipment."
"If we had these things at this time five years ago, I'm afraid... it's not completely impossible to rewrite history."
In the 1996 sea and air exercise, Shen Tao, then deputy commander of the 4th Regiment, naturally participated.
However, the main equipment of the 4th Regiment at that time was only a few Y-8Xs used for maritime mapping and patrolling. They could only wander around the periphery for a few rounds and look at the tense core exercise area helplessly.
Shen Tao still remembers the feeling of being in the dark and anxious.
Now the first early warning aircraft has finally been installed. Although it was only a transitional model for "backup to regular operation" at that time, it at least gave the special aircraft unit the ability to directly participate in sea and air confrontation.
"Let the past be the past."
Chang Haonan patted the other party's shoulder:
"If I have to say, it was because of the stimulation of that incident that made me determined to work hard..."
This sentence is not wrong, but it is not completely right.
It is true that he did work hard back then, but human ability has its limits after all.
What really changed everything was that wave of rebirth with memory and experience, and of course the system.
However, this is something that Chang Haonan cannot tell anyone...
"Is there such a thing?"
Shen Tao naturally didn't know the twists and turns, but just glanced at Chang Haonan next to him with a little surprise, and finally had a smile in his tone:
"So if you calculate it this way, the Americans are actually at a big loss..."