The military-industrial scientific research system of the academic master.

Seeing this, the rest of the people gathered around the table.

“If the dual-channel signal uses an orthogonal design, it can essentially double the instantaneous bandwidth. Although DRFM has reduced the performance requirements for ADC and RAM compared to single-channel DRFM, it is still not enough. thorough."

“But we can consider giving up the idea of ​​phase-divided sampling or time-divided sampling, and design multiple narrow-band DRFM subsystems, split according to frequency bands, and mix each channel with a voltage-controlled oscillator (VCO) to output a baseband analog signal. It is processed by a narrowband DRFM subsystem, so that the bandwidth requirements for DRFM can be almost completely avoided, and the sampling frequency can be reduced to a fraction of the original."

At this time, the pencil in Chang Haonan's hand seemed to Guo Lin like a magic wand. The intersection between the tip of the pen and the paper continued to produce miracles as the former drew pictures.

The circuit principle this time was more complicated, so Chang Haonan spent a while drawing it before finally completing it.

"This design is indeed feasible in theory, but if so much hardware is added to the project, each new part will bring system errors, and the superimposed noise floor and signal distortion must be very serious."

Compared to Guo Lin, who was still analyzing the schematic diagram, Xu Yang had already begun to think about the feasibility of this idea:

"Among other things, the inconsistency between these channels requires phase level compensation. For dual-channel systems, you can also consider sharing a reference clock to achieve inter-channel coherence. This avoids the need for high-standard ADCs. and RAM, but as the number of channels increases, the requirements for the reference clock will increase, and we still can’t build this thing.”

"The multi-channel technology that uses a reference clock that you are talking about is generally used on oscilloscopes. The DRFM architecture of the jammer is much more complex than that of the oscilloscope. Not to mention us, the Americans probably cannot take this route by relying solely on clock performance. .”

The reason why this idea is considered feasible by the system is naturally because Chang Haonan has already considered this issue.

"So what we have to do next is to compensate for various error factors separately."

"For example, a method of combining calibration and compensation can be used to correct the distortion of the sampled data at the baseband, and suppress the amplitude-frequency characteristics and group delay characteristic errors in each channel, thereby ensuring that the reconstructed signal is close to the original signal."

"What about the phase difference problem?"

"There are not many tricks to the phase difference, but it can be measured, or very accurately estimated, so that corrections can be made in advance."

Chang Haonan explained while writing amid the astonished eyes of those around him:

"Suppose we send a broadband pulse signal with a slope of k through the digital-to-analog converter. The signal reaches the RF input end through the feedback branch. After going through the combiner, band-pass filtering, down-conversion, and low-pass filtering, it is collected by the DAC The signal processor performs STRETCH deskew processing on the original transmitted signal. Due to the delay difference between the two signals, a single frequency output Δf will be obtained. This frequency can basically represent the delay amount in the input-input process. : Δt=Δf/k.”

"It's that simple?"

An engineer next to him was surprised to find that he could understand.

He originally thought that he would be faced with a set of theories that were like a heavenly book, and then he would need to go back and study for a few days to understand it.

"I'm just going to talk about the principle now. It's definitely simple, but later we need to consider the compensation algorithm in detail, and the workload is still quite big."

Chang Haonan put down his pencil and shrugged. Guo Lin next to him had the insight to hand over a cup of tea at the right temperature.

Pass tea to the boss.jpg

"The regular worker has a drink of water."

Chang Haonan picked up the cup and drank it all:

"Of course, even under the most ideal conditions, it is impossible to completely eliminate the errors between multiple frequency bands. Especially for broadband cross-channel signals, the signal distortion generated at the intersection point of the frequency bands must exist in principle. , and the more they are added, the more they are added, so we cannot make it unlimitedly with twenty or thirty channels, otherwise we may not even be able to pass the power-on self-test."

“My current plan is to use the 350Mhz bandwidth DRFM that we can produce and can stably package, and get 10 parallel channels. In this way, even if the bandwidth loss at the frequency band junction is included, we can basically achieve a bandwidth coverage of about 2.5Ghz. "

"That's quite a lot..."

The main business of Institute 14 is radar, so it is naturally sensitive enough to this kind of thing:

"As long as it can cover the frequency range of 6.5-9Ghz, it is enough to handle the C-band and X-band signals used by most air radars."

Although the center point of the X-band is 10Ghz, considering the attenuation problem, in fact most radars will not use too high a frequency. 9Ghz is enough, and in the field of communications, the lower edge of the X-band will extend to 7Ghz. Nearby, the 6.5-9Ghz option can also provide precise directional interference to certain specific satellite communications.

"If the reconstructed signal compensation algorithm is good enough, there should be potential in this range."

Xu Yang can still keep up with Chang Haonan's thinking in his field of expertise.

"The biggest problem now is that the size and weight of the equipment will be larger than the dual-channel orthogonal design, and it is also difficult to control the heat and power consumption. It is difficult to make a self-defense pod like L005 that does not occupy heavy-load mounting points. No need to think about it, fortunately, the performance of our thing is much better than the L005. If one aircraft in a formation has two, it can basically cover the entire fleet."

Chang Haonan casually drew a flat and long pod on the paper, and then drew a small fan-like thing on the head:

"However, we are still using it on airplanes anyway. Adding an impact generator on the head can solve some of the power supply problems. As for heat dissipation, it can also be solved by introducing low-temperature air conditioning into the air."

As he spoke, he drew an outline similar to an airplane on the paper, but his drawing skills were so average that people couldn't tell whether it was a J-8C or a J-H-7.

"In this case, do we have our own EA6B or EF111?"

Looking at the concept drawing on paper, an engineer standing behind Guo Lin suddenly said, his tone full of joy.

It can be said that since the Gulf War a few years ago, for radar researchers like them, the above two types of dedicated electronic warfare aircraft have become the big devils that they think about day and night and hope to defeat.

Although they still haven't completely figured out how to defeat the enemy, but now...

Can it be considered as creating your own big devil?

"Hmm... Speaking of our pod alone, forwarding frequency shift interference is the current mainstream technology route, and it is not bad in terms of functionality."

Chang Haonan looked at the outline drawing on the draft paper in front of him and replied:

"But if you really want a dedicated electronic warfare aircraft, you will need to make major changes to the aircraft platform itself. Just hanging two pods on an ordinary fighter aircraft is almost meaningless."

"However, on the bright side, our imaginary enemy does not pay much attention to the construction of air defense systems due to its confidence in its air force. Therefore, the intensity of air defense suppression operations faced by our army is not as high as that of EA6B."

In fact, having two such pods mounted on the J-8C or J-H-7 is closer to the effect of the F16CJ Wild Weasel in the US military.

Of course, even this is enough to keep Institute 14 happy for a long time.

Although he has been reborn for nearly a year, Chang Haonan is still subconsciously accustomed to directly comparing the things he creates with powerful enemies on the other side of the ocean.

But for most people such as Guo Lin, this is something no one dares to think about even if they are optimistic.

To be able to achieve "the enemy is strong and we have it" instead of "the enemy has it and we have nothing" is already a dream that many people hope to realize throughout their lives.

But there are not exceptions.

As a person of this era, Xu Yang's thinking is much broader:

"It's a pity that this set of tools has only limited flexibility in processing broadband signals. It can only allocate resources equally to each channel. It cannot flexibly allocate frequencies to a specific narrowband frequency band based on the characteristics of the detected radar signal..."

Chang Haonan next to him said to himself, "You dare to think about it. This is a function that was only implemented in the later third-generation electronic jammers such as EA6B and EF18G."

However, he did not want to make the comrades of the 14th Institute think that the role of more advanced components could be replaced by architectural upgrades alone because of his operation, so he followed the trend and continued:

"No way, this is determined by the level of hardware manufacturing. The difficulty of creating a batch of 100% consistent components is no lower than building a high-resolution and high-sampling rate ADC, so in order to compensate for the distortion, some functionality must be paid. The price, in the final analysis, is that we still have to find a way to re-develop our own semiconductor industry, and relying solely on opportunism will definitely hit the ceiling in advance."

Everyone who heard this sentence looked at each other.

This is not a problem that their Electrical Engineering Department 14 can solve.

"It doesn't matter, this kind of thing doesn't happen overnight."

Chang Haonan also understands that things must be done step by step.

Just like the previous layout of the civil aviation industry, if you want to influence this large-scale industry, the core is to find a starting point.

If you directly say that I want to engage in the XX industry, there will definitely be no future.

"Let's not think about things that far away. Since the principle works, we should be able to get an engineering prototype for testing next?"

It can be seen that Guo Lin is already hungry for the thing drawn on Chang Haonan's picture——

When he first realized that high-standard components had to be used and that China was embargoed and could not import them, he thought that the project he had high hopes for was going to fail.

But now it is possible to use domestic components with relatively backward technical indicators to achieve the system indicators of high-end products.

Definitely an unexpected surprise.

"Engineering prototypes must be made, and two of them must be made at the same time."

Chang Haonan glanced at the broken pod remains on the long table not far away:

"Make a compact version according to our own design, and then reproduce an American oversized pod in its original size. I want to see what's fishy in it..."