Chapter 618 We are PD
Everyone wants good things, which is normal. Since we cannot afford to build large ships, we are still moving towards the path of "air, submarine and fast". This missile solves the problems of "air" and "fast" at once. Both of them have strict requirements on the size and weight of the missile body.

Gao Zhendong himself knew nothing about this matter. He was currently receiving Mr. Liu, who was in charge of the landing work of the "615" fighter radar.

The 615 radar is now being prepared for the Gong-5 multi-purpose model, with the goal of making maximum use of the pointed nose of the multi-purpose fighter.

General Liu had already obtained the data on the size of the radar from the Cidu Aircraft Factory through the Defense Work Committee.

As soon as he got the data, General Liu was glad that he had decisively escaped from the RP-1 "Emerald" radar imitation.

Compared with the cramped RP-1, this space is much more spacious, and there is no antenna in the middle of the air inlet, so the problem of interference from the air inlet lip must be considered.

Similarly, the weight index has also been relaxed a lot, thanks to the improvement of related indicators such as lift-to-drag ratio after the Gong-5 multi-purpose model adopted several suggestions from Gao Zhendong.

This is what it means to make your own thing, and it gives you a great sense of accomplishment. Copying RP-1 is not a pleasant job. Even if the copying is successful, the radar can only be solved to the extent of whether it exists or not.

Thinking of this, Mr. Liu felt a little sorry for the former deputy chief engineer of RP-1's imitation work, and now the chief engineer. Comrade, thank you for your hard work. I will treat you to a meal when you return to the unit.

But this cannot be said of this. For the former deputy chief engineer, it is hard work. Everyone has to work hard these days. Someone has to do the work. It seems to be worth it to be replaced by a chief engineer.

And now, Mr. Liu is in Gao Zhendong's office, discussing the plan he has already thought of with Gao Zhendong.

Overall, the plan has reached the limit of what Mr. Liu can currently control.

The plan does not use single-pulse radar. A defect of single-pulse radar is that while obtaining the target distance, it can obtain the radial motion speed of the target relative to itself, but it cannot obtain its horizontal motion component. As a result, the grasp of the target's motion state is incomplete, which will cause certain problems in the fighter's fire control.

However, the defect of continuous wave radar is that it is difficult to distinguish the relationship between continuous signal echoes, which greatly compresses the ranging distance.

Therefore, the solution chosen by Mr. Liu is a continuous wave radar with continuous frequency modulation, which can solve the problems of ordinary continuous waves through continuous modulation frequency changes, thereby greatly expanding its ranging distance.

At the same time, another advantage of this radar is that it uses continuous wave scanning, which can calculate the true motion state of the target through the different velocity components of two scanning angles during the scanning process.

This solution has nothing to do with digital signal processing, but is a simple calculation after obtaining the before and after states, so there is no requirement for digital signal processing technology.

However, this thing is not without flaws. In addition to not introducing Doppler technology, which leads to increased errors in calculating the speed of high-speed targets, the most fundamental problem lies in the continuous wave.

Under the current circumstances, in order to ensure that there is no radar self-interference, the transmission power of this thing cannot be increased!

Moreover, since the energy of the continuous wave is evenly divided, its energy density is not as high as the pulse signal for the same power, and the actual signal-to-noise ratio is still not high.

There is a reason why PD (pulse Doppler) radar dominated high-performance fighter radars for decades before active phased arrays matured.

Looking at the overall system of the radar, Gao Zhendong frowned.

Mr. Liu was very perceptive: "Chief Engineer Gao, is there a problem with the plan?"

He now has a general idea of ​​Gao Zhendong's style. Chief Engineer Gao has his own set of judgment logic, which makes others seem to him sometimes extremely radical and sometimes very conservative, but it is difficult for others to grasp his way of judgment.

But looking at the final result, he was right every time. We can only say that extraordinary people do extraordinary things.

"Chief Engineer Gao, this plan may be a little radical, but I think it is still feasible. In addition, in order to ensure the downward-looking capability, we plan to add a single-pulse mode to this radar. Using the single-pulse mode and the moving target indication technology you proposed, we can solve the downward-looking problem of the radar."

I only talk about looking down, but not shooting down. There is still a little distance between looking down and shooting down. When you see it, you rush over and use the machine gun.

Gao Zhendong woke up from his deep thoughts and shook his head: "Radical? No, no, this radar is not radical. Let me take another look, let me take another look."

I'll tell you what real radicalism is in a moment.

"Oh, okay, keep watching. If there's anything you need explained, just ask."

"For an F-100 Sabre-sized aircraft, the detection range is no less than 40 kilometers, and the tracking range is no less than 20 kilometers. Is this what the Air Force proposed?"

General Liu smiled: "No, no, this is what we proposed. It hasn't been formally submitted yet. We'll just mention it this way first. The distance is more than double that of RP-1. I don't think the Air Force will have any objection." The detection range of the RP-1 radar is only a dozen kilometers, and the ranging distance is only a pitiful few kilometers. This is the biggest reason why Gao Zhendong has no interest in imitating this radar.

This broken thing is not as good as eyes if we don't consider the visibility issue. However, a pair of eyes is free, but a radar weighs several hundred pounds.

"Well... a little small, a little small." Gao Zhendong's idea was actually much higher than this.

"Too small? Chief Engineer Gao, this is already a very optimistic and radical idea." Mr. Liu still wants to talk about science, but unfortunately users will not talk about science with you.

For example, the radar that was later used to equip the Type 8 was developed in 196s, and the technology was still extremely backward at that time. However, the Air Force required double three and 100km detection distance from the very beginning, but they failed to achieve it after decades of work.

If the double three mainly depends on the aircraft, then the detection distance of 100km was something that we, the first generation of radar engineers, tried our best but failed to achieve.

Gao Zhendong thought about it and put forward his own opinion.

"Boss Liu, my suggestion for this thing is to have an upward detection range of 50 and 30 kilometers, a downward detection range of no less than 30 kilometers, and the ability to provide illumination for semi-active radar bombs. Otherwise, the air-mounted side will be the first to be unhappy."

Considering that the radar antenna caliber of the Gong-5 multi-purpose fighter is 0.6~0.7 meters, it is still possible to achieve this indicator if we think of a way.

The AN/APG-4 of the American F-59J is larger than this one and entered service in 1966, but its head-on detection range for the MiG-21 is about 80 kilometers, and its downward detection range is about 60 kilometers.

Mr. Liu and his entourage were so confused when they heard this. No wonder he said the plan was not radical. It turned out that he was the most radical one.

"Chief Engineer Gao, isn't this a bit too high? I'm afraid we are not capable of it." Chief Liu, who had never dared to consider a number above 50, decided to argue for it, otherwise the comrades below would be under too much pressure.

Gao Zhendong thought about it and agreed. It would be bad if he scared away the comrades who were doing the specific work. He nodded and said, "How about this, we will report it according to what you set first, but our real goal is not this indicator. We must at least achieve what I said."

Gao Zhendong wanted to talk about the multi-target tracking and attack capabilities, but then he thought that this was too scary. If he told them about it, they would probably run away and leave. So he decided to leave it alone. When it was realized according to his idea, they would remember it themselves.

Chief Engineer Liu had no objection to Gao Zhendong's idea. To publicly set small goals and internally set big goals was a common "keeping a hand" approach in scientific research. It provided less pressure. It seemed that Chief Engineer Gao was very particular.

"Well, I have no objection to this. We can do this. But the power of continuous wave radar cannot be increased, and the signal processing requirements are too high."

When white noise cannot be eliminated and there is no technology to obtain sufficient information under low signal-to-noise ratio conditions, the most fundamental means to improve detection performance is to increase the transmission power and increase the signal-to-noise ratio.

"Continuous wave? If we don't make continuous wave, it will just be a transitional technology. I don't think it will have much future in fighter radars for at least a few decades. Let's just make pulse radar."

Gao Zhendong shook his head in disdain. The continuous wave radar had been used on fighter jets for a very short time. Only a few aircraft, such as the early Sparrow's supporting radar, had used it, such as the F-4E. It was soon replaced by the PD.

"Pulse? Well, a single pulse is not a bad idea. We can just open up a branch for the continuous illumination of the semi-active radar projectile. As for the others, if there is no horizontal motion component data, it is not unacceptable."

"Not a monopulse. This thing has limited downward-looking capabilities, and is not very useful for guidance and fire control."

Mr. Liu was going crazy. This didn't work, and that didn't work. So what on earth were you going to do? You couldn't do a phased array, could you?

"Hiss~~~~~~ Chief Engineer Gao, do you want to make a phased array?"

Contrary to what many people subconsciously believe, we wanted to develop phased array radars very early on, including on fighter jet fire control radars, but the results were quite mediocre in the early days.

So it's not that Mr. Liu doesn't know about the phased array, but he is very clear that this thing is very unreliable, at least not at this stage. Let's not talk about whether it can be developed or not, just the head alone is probably not big enough to be installed on a fighter jet.

Chief Engineer Gao's move can't be described as nonsense, it's like he's tearing the person in half!
However, Gao Zhendong quickly resolved his doubts: "Mr. Liu, let's develop a pulse Doppler radar."

Pulse Doppler radar?
To Gao Zhendong's surprise, Mr. Liu was not as familiar with pulse Doppler radar as he was with phased array.

Although both are ways of classifying radar generations, strictly speaking, these two technologies follow two different definition modes.

(End of this chapter)