Chapter 1196 Chinese Aegis

"maritime?"

Zhu Yongshun brought his head closer and closer:

"Are you going to deploy to an island?"

"That may require some special processing of some radar components..."

As he spoke, he thought about the preparations required to deploy high-precision electronic equipment in an island environment.

Although it is not impossible to use ordinary land-based radar directly at sea, its performance and reliability will be greatly reduced——

In addition to the salt spray issue just mentioned, foundation stability, power supply capacity, and the interference caused by water vapor on radar waves... all need to be taken into consideration.

This is why a lot of equipment that looks the same on the surface has to be made into a separate navy model.

However, before he could figure it out, he saw Li Jianqiang next to him shaking his head:

"I'm afraid... it's not the island."

Zhu Yongshun blurted out almost without thinking:

"If it's not an island, how can it still be on..."

He originally wanted to say, could it still be on the water?

But halfway through his words, he stopped abruptly.

"Is it really on the sea?"

At this time, Li Jianqiang had already pulled up the sea area map around Zhejiang Province from the computer next to him.

In fact, although there are many islands off the coast of eastern Zhejiang, there are only a few familiar ones that can deploy radars and station people there for a long time.

Most of them can only be called "islands" from the perspective of maritime law, but they are essentially rocks that are always exposed to the sea.

As for the location marked by Chang Haonan, the surrounding area is even more vast.

Not even a reef...

"There really isn't any marked land."

Li Jianqiang shook his head:

"Moreover, not only is there no one at that coordinate, there is no one within a radius of dozens or hundreds of kilometers nearby..."

For a moment, the two of them stared at the chart on the computer screen in front of them, somewhat at a loss of ideas.

Although Chang Haonan gave only an example, they still need to make adjustments according to the actual situation.

But there is no land around it, which means that after the adjustment, the result will most likely still be on the water.

"It seems that the plan I just proposed is still difficult to implement..."

Zhu Yongshun couldn't help but feel a little discouraged.

However, Li Jianqiang’s reaction was not so pessimistic:

"Actually... I would say that it is not necessarily impossible to deploy radar at sea..."

"..."

There was another few seconds of silence.

Zhu Yongshun looked at the screen, then at the document on the table, and a solution suddenly popped into his mind:

"You mean...let the early warning aircraft go forward and serve as the second transmitter to coordinate with several other shore-based radar points?"

But after saying that, I immediately felt that it was not appropriate:

"But the speed of the early warning aircraft is too fast. If the moving platform wants to synchronize with the fixed platform, technically..."

"No no no..."

Before he could finish speaking, Li Jianqiang quickly waved his hand:

"Technical issues are secondary. The key is that even if a misfire is unlikely in this situation, it is still a bit too much to send an early warning aircraft out under the threat of a stealth aircraft... Besides, the superiors' plan is to let that aircraft The newly commissioned Air Police 2000A was used as a cover-up method. The L-band radar prevents the other party from actually breaking through the air defense circle, leaving no room for us to use it. "So what I mean is that we can consider letting the comrades of the Navy contribute... The two Chinese Aegis built by Changxing are not. The test has been basically completed. Do you plan to officially enter service before the end of July?”

This has been made completely clear.

Although the shipboard area air defense system with 346 radar as the core is officially called "Sea Star", because it is benchmarked against the US military's Aegis system, even within the military, some people prefer the term "Chinese Aegis". nickname.

Zhu Yongshun immediately understood what Li Jianqiang meant.

Destroyers are large enough and have air defense capabilities, so they are less threatened than early warning aircraft.

Moreover, as a ship, it can be deployed near a specific location for a relatively long period of time like a ground radar, without having to seize the time window like an early warning aircraft.

This is undoubtedly a huge benefit for the defense that needs to take advantage of waiting for work.

However, it is not completely without problems.

Zhu Yongshun suppressed the excitement in his heart and raised the difficulties before him:

"Although the surface ship platform is relatively stable, it is not a completely fixed deployment mode. Moreover, the 346 radar and the model we have are inconsistent in many technical details. If we want to achieve transmission and reception cooperation between the two, there is still a lot to do. There is work to be done…”

Bistatic radars, especially those deployed on different platforms and using different types of hardware, first need to solve the synchronization problems in time, space and phase between the transmitting and receiving ends.

It is also one of the biggest obstacles to the large-scale application of this technology.

But Li Jianqiang was very optimistic at this moment:

"The 346 radar is a four-sided array with a shared back-end control system. It is a 360° omnidirectional detection. There is no need to consider spatial synchronization issues from the beginning..."

As he spoke, he pulled over a piece of paper and drew a simple diagram on it:

"As for time synchronization... between the ground and the water surface, it is definitely not possible to directly use cables to transmit the transmitter's RF encoding and frequency reference signal to the receiver. Fortunately, both radars can use linear frequency modulation to interrupt the continuous wave signal, that is, The constant-temperature crystal oscillator provides time, frequency and phase reference signals to the transmitter and receiver respectively.”

"Thanks to the comrades in the aerospace system, our Beidou system is equipped with its own spaceborne atomic clock. It can first use the timing module of the satellite positioning system to generate world standard time and synchronized second pulses, thereby ensuring that every frame of the radar system transmits signals and local The vibration signals are generated at the same time and have the same timing.”

"Then, a phase-locked loop chip is used to tame the local constant-temperature voltage-controlled crystal oscillator to realize two clock sources of the same frequency and phase, which can be used as the reference clock of the direct digital frequency synthesis module that internally generates the transmit signal and the local oscillator signal. In this way, , each frame transmission after synchronization can be strictly aligned with the frame start pulse edge of the local oscillator signal..."

"..."

Ten minutes later, with Zhu Yongshun's slightly surprised expression, the content on the paper had changed from the initial sketch into a complete technical schematic diagram:

"In short, although the current first-generation atomic clock on the Beidou system is not as accurate as GPS, when reflected on our radar system, the error between the sending and receiving ends will not be greater than the microsecond level, and this is only a temporary emergency after all. , there is no need to consider the issue of cumulative error, and it is definitely sufficient for remote warning missions.”

Hearing this, Zhu Yongshun also slapped his thigh suddenly:

"Then the principle of phase synchronization is almost the same as that of time synchronization. As long as the frequency and phase coherent reference signals are provided through the constant-temperature crystal oscillators set up on the transmitter and receiver respectively, can the phase coherence on both sides be guaranteed?"

"You're right."

Li Jianqiang directly closed the document in front of him and glanced at the title written on the cover:

"Spatial-temporal synchronization and phase calibration technology of bistatic radar"

Then he continued:

"In addition, Academician Chang specifically reminded us that because the control voltage range of the voltage-controlled crystal oscillator is greater than the output voltage range of the CP terminal of the phase detector, an active loop filter circuit must be used to amplify the voltage range of the CP terminal of the phase detector, and An active filter model of the in-phase topology is also given to eliminate ripple interference and spurious components caused by the phase detection frequency.”

"The only drawback is that compared to the direct synchronization method, the frequency agility of this brief scheme is relatively poor. Especially this time, there are six sets of receivers and transmitters in total. I am afraid that the frequency conversion information even needs to be advanced in advance. By default, there is really no resistance to continuous sampling and forwarding interference, which is a pity..."

Although he said that, there was no look of regret on Li Jianqiang's face.

As for Zhu Yongshun, he is already eager to try:

"This active filter circuit needs to be designed separately, but fortunately it can be connected to the existing radar receiver through an external module. It is not a strenuous upgrade... Do you want to contact the Navy and the Electronic Technology Group immediately to start? Start making targeted modifications to the equipment?”

Li Jianqiang almost subconsciously wanted to nod.

But I still got it under control midway:

"The destroyer has not been officially delivered yet, and the ownership may be more complicated... Besides, as the Air Force Equipment Research Institute, it is not convenient for us to directly contact other services."

After thinking for a few seconds, he made a slightly compromised decision:

"In this case, you are responsible for contacting the Electronic Technology Group and asking them to cooperate with us in modifying the radar hardware... I will report to my superiors immediately and request the cooperation of the surface ship force..."