Military Industry of Great Powers: Build the Strongest Flanker

While Zhao Guoqing was communicating with Ji Hongbo, he also secretly felt that he seemed to have overlooked something.

That’s thinking about the J-6 and J-7. Installing a passive phased array radar in the narrow space of the J-7 requires a lot of black technology.

For example, the oscillation circuit that wants to convert low-frequency current into high-frequency current is a big trouble. You must know that airborne phased array radars use x-waves, which belong to the microwave category. High-frequency current needs to pass through the antenna to emit x-band radar waves.

With current technology, if you want high-frequency current, you need to use low-frequency current to oscillate multiple times to obtain it, which requires a lot of weight and power consumption.

His solution is to use an inverter circuit IGBT (thyristor) to control different conduction angles for frequency modulation, and then use a gallium nitride transistor to amplify the current. A palm-sized circuit can solve the problem of high-frequency current.

There is also the antenna. In order to make the detection distance longer, an antenna with higher sensitivity and emission efficiency is needed. After much deliberation, with the current technology, the x-band Vivaldi antenna array sixteen years later was adopted. By opening the end of the Vivaldi antenna The antenna gain of the feed structure designed as an ultra-wideband micro-to-cps balun circuit can be increased by 272% compared to the quarter-rod antenna that is currently commonly used.

The receiving end uses an X-band profile rabbit-ear triangular lattice array with low coupling effect, and the sensitivity can be increased by 97.6%.

These have been demonstrated through many experiments. Although it is not the most advanced technology, in this era, it is still 20 years ahead of the United States.

Transmitting and receiving antennas, power supply systems, ADC, DAC chips, computing chips, high-frequency oscillation circuits, array layout, pulse...

There are difficulties, but they can be overcome, provided that Tsinghua University's one-micron manufacturing process can pass the test.

Of course, there are some components that may even need to be imported, such as high-tolerance solid capacitors, breakdown-resistant resistors, high-efficiency ferrite inductors...

But in Ji Hongbo's eyes, Zhao Guoqing's words were a bit arrogant.

"National Day, I doubt your ambitions, but I need to remind you. Do you know the current situation in our country? Our manufacturing level, our technical reserves..."

Zhao Guoqing looked at Professor Ji Hongbo and simply said: "Is the 204 radar, including the JL-10 radar currently under development, our highest level of technology now?"

Ji Hongbo nodded and said, "About that. Other research institutes are not much higher, otherwise 204 wouldn't be taking the leading role now. On National Day, you should have seen how much space the J-7 can install radar!"

"Professor Ji, can you see the real thing?"

Ji Hongbo didn't say anything. Of course he could watch the plane. Zhao Guoqing had this authority, but... what he was thinking about was whether the young man in front of him was impulsive or thoughtful.

"National Day, what do you think of the radar's technical specifications?"

Zhao Guoqing didn't even have time to think, and said directly: "X-band, 3cm wavelength, detection range of 100 kilometers, fire control range of 40 kilometers, can track 8 targets at the same time, attack three targets at the same time, and can target medium-range air-to-air within 40 kilometers. Radar to guide!

However, I still don’t know how much performance the specific components can achieve. The scanning frequency of the radar beam cannot meet the requirements, but it can complete the scan within a range of plus or minus 30 degrees of 100 kilometers within two minutes, and it can detect targets outside the visual range. Keep track of. "

Without high-performance chips, high-frequency scanning is impossible. You must know that the farther the detection distance, the larger the area that needs to be detected. The radar beam radiates a limited space at one time, so it will naturally take time to complete all scans.

Moreover, simultaneous multi-beam scanning requires a lot of additional circuits, and it is difficult for the signal processing at the transmitter and receiver to keep up.

These technical indicators are also limited by the current poor workmanship.

Even so, in Ji Hongbo's eyes, these data are enough to defy expectations. You must know that the search distance of both the 204 radar and the JL-7 radar is only 15 kilometers.

"..."

"How is it possible?" Ji Hongbo said: "National Day, why did you choose x-wave instead of the more practical L-wave? The oscillation circuit of x-wave is difficult. The receiver, power supply, heat dissipation, and a power supply line will fill the entire space. Moreover, the X-wave must be detected a hundred kilometers away, and how much radiation power must be reached before the echo can be detected. Have you calculated it on National Day?"

Zhao Guoqing did not speak, but drew a three-dimensional xyz coordinate system on the paper. On the yz plane of the coordinate system, he simply drew a 6x6 planar phased array, and drew the radar wave effect diagram along the x-axis.

"Through the arrangement of the transmitting antenna, the main lobe beam can theoretically be controlled within a small range and the side lobe level be minimized. In this case, it is similar to the focusing effect of a magnifying glass. We can concentrate the energy into a small A surface on which radar waves maintain sufficient intensity.

Scanning the airspace is completed through rapid beam scanning. If a target is found, the target can be continuously scanned under the control of the computer. However, if there are more targets to be tracked, the scanning efficiency will be lower. According to preliminary estimates, 8 targets are tracked. It’s already the limit! "

Ji Hongbo looked at Zhao Guoqing's demonstration. He couldn't express his opinion. He didn't do much research on phased array beams. When demonstrating on a two-dimensional plane, he could draw an approximate beam by drawing the radar wave peaks and troughs, but in three dimensions Completely different.

“Is this model proven?”

Zhao Guoqing nodded, "I have argued it!"

"..."

Thirty years later, using MATLAB simulation software, you can just build a model and input a few parameters, and you can see the distribution of the entire radar wave main lobe and side lobes, the level signals of the main lobe and side lobes, and even simulate the target of the radar wave. Characteristics, but now, it is difficult to explain clearly.

"How to change the scanning direction? There is not much room for antennas inside the J-7!"

Zhao Guoqing still demonstrated on a two-dimensional surface, and he handed the pen to Professor Ji.

"Professor Ji, can you move the radar waves emitted by each antenna of the array by one-third of the phase? By the way, the distance between the radar antennas is 1.5cm, half a wavelength!"

"..."

Ji Hongbo took the pen, looked at Zhao Guoqing, and began to draw the radar wave with hesitation. As the country's top expert on radar, Ji Hongbo's foundation was undoubtedly very solid. The drawing was completed in less than five minutes.

"The beam shifted by 30 degrees? But the level of the main lobe seems to be dispersed a little!"

Zhao Guoqing nodded and said: "The scanning range is about a 120-degree cone. The main lobe features outside 120 degrees are not obvious, and the side-lobe level is too high!"

Ji Hongbo took a breath and said: "This is much better than the 204 radar. Its radiation range is only a cone of 30 degrees up and down, and 60 degrees."

After speaking, Ji Hongbo felt vaguely that this transmitter was worth trying. He looked at Zhao Guoqing with incredible eyes.

"National Day, how come you have such a brain?"

Thanks to brother l599xl for the reward and support.