Rebirth 2010, the best

Chapter 207 What is Technology?

It is still the familiar underground parking lot.

Before getting off the car, Zheng Xiaofan said:

"Luyao, when we get there, don't be nervous. Just tell us what you have to say."

Lu Yao thought to himself, why am I so nervous?

They know this thing is extraordinary and come here to verify it, so they are the ones who should be nervous.

Because once all the models of the RDSS front-end chip are completed and the theoretical verification is passed, it means that its appearance sets a benchmark for all satellite positioning systems in the world. And, most importantly, it also completes the technological gap.

While everyone was still crawling on the ground trying to figure out the new model, the RDSS chip flew straight into the sky.

Its various indicators are epoch-making. They are the product of at least three generations of chip technology, industry and technology after 17 years.

Once it is put into use, people in other countries will have no choice but to catch up. At the same time, the breakthroughs they may have achieved in 17 or 18, the Chinese have already made in 11, a six-year lead... Even if they have 6 pigs, they will have to catch them for a while.

What's more, "we", standing on the shoulders of giants, have been completely ahead for six years.

He is very clear about this concept.

Therefore, he does not need to be nervous because he himself is the creator.

The ones who are nervous are probably the people who came here today.

Or, more accurately, urgent.

It's time to show them what technology is.

However, facing Zheng Xiaofan's kindness, Lu Yao still smiled and nodded:
"Okay, got it. Brother Fan, who are the people coming today?"

"This……"

Zheng Xiaofan thought about it and shook his head:
"It's hard for you to ask, and I can't tell you. But they are definitely people who know a lot about technology."

"Ok."

"Well, let's go."

The two of them entered the elevator and went upstairs. Soon, Zheng Xiaofan brought him to a security door.

"Take off all electronic devices and put them in that box."

"Ok."

"Remember to turn off your phone."

“I just turned off the phone.”

"Ah."

Soon, Lu Yao, who was alone, followed him through the door. Someone immediately came over for security check and let them go after confirming that the two of them did not carry any electronic products. Finally, the two of them came to a door.

Zheng Xiaofan pushed the door open directly, and Lu Yao discovered that there seemed to be a conference room inside.

The conference room is not small. If it is really full, it will probably take 20 to 30 people.

There are already seven or eight people sitting inside.

But it’s hard to tell what they do because they are all wearing very ordinary clothes.

It's just that there is a gap in age.

Some of them looked about the same age as Zheng Xiaofan, and there were also a few who were probably in their forties or fifties.

After the two people appeared, everyone's attention was focused here.

There was also a laptop on each of their desks.

At this time, a middle-aged man sitting at the front spoke:
"Student Lu Yao, right?"

"Yes, hello."

Lu Yao greeted politely.

At this time, Zheng Xiaofan had quietly sat aside.

Lu Yao was the only one standing in the entire conference room.

Following his response, the middle-aged man smiled and nodded:
"Well, I called you here today mainly because of the radio frequency chip you developed. It may take up some of your time. But don't worry, the food in our restaurant is delicious."

"Uh……"

Hearing this, Lu Yao knew that he must be an outsider.

There is no other reason.

He used the term "radio frequency chip" rather than a more specific term such as RDSS, or satellite radio determination service transmit front-end chip, or other terms.

"General" has never been a word that people in the academic field like.

Nor should it be adopted at this moment.

But since this person was the "one in charge", Lu Yao pretended to know nothing and nodded:
"Ok."

No tension.

There is no feeling of being cramped.

Seeing this, the middle-aged man nodded:
"The computer in front of you contains all the information about the chip you designed. The projector is already on. We called you here today because we hope you can systematically explain everything about this chip to us, including its advantages, performance, shortcomings, etc. Finally, we will ask questions and you can answer them truthfully. Is that okay?"

"no problem."

Lu Yao responded and walked to the computer, which looked much thicker than an ordinary laptop and had a base as thick as a brick.

He tapped the space bar, the screen lit up, and the light from the projector also hit the screen next to him.

Lu Yao quickly and skillfully opened various EDA software and found that indeed, everything he knew about this model had been transferred to this computer.

As for what’s next…

In fact, he missed it quite a bit.

Give a report.

So, he took a deep breath, looked at the people who were quickly becoming "dark" because of the projector lighting up, and said directly:
"Then...please allow me to tell you the original intention of designing this model. First of all, our country's Beidou navigation has developed rapidly in recent years, and in 2010, it began to fully iterate the Beidou navigation system. I have read the article that the national plan is to completely complete the comprehensive deployment of Beidou III before 2020. The RF transmission front-end chip is the most important part of the navigation terminal. It is related to the quality of navigation performance, the quality of user information reception and transmission, and the response speed. Therefore, according to the 2010 work report on major national science and technology development matters, the Beidou third-generation navigation front-end transmission chip must be highly integrated, low power consumption, and high linearity, which is of great significance to the entire third-generation navigation system."

He speaks and others listen.

No one interrupted, and no one looked strange.

In the dim conference room, everyone just stared at him.

Including the camera in the corner.

"The model I designed was inspired by a recent paper on high-pass ground filter published by Cheng Yu, a graduate student from the University of Electronic Science and Technology, in 04. I used CMOS technology to design a satellite radio determination service transmission front-end chip. The structure adopts a direct up-conversion structure and integrates four sub-modules: active low-pass filter, modulation mixer, variable gain amplifier and driver amplifier.

In addition, based on the BeiDou-2005 navigation transmitter architecture and performance indicators published in , we analyzed the contribution of each module’s performance to the overall system performance, optimized the transmission link budget, planned the indicators of the four modules, and carried out optimization, upgrading, and use.

The current design idea is to design an active Chebyshev filter with the cascade structure of a second-order Thomas Tow two-stage filter, study the Gilbert active double-balanced mixer, design an orthogonal active double-balanced modulation mixer, and use the improved Gilbert unit, namely the signal addition type, for circuit design. The implementation method of the driver amplifier is studied, and a class AB amplifier is selected for the design of the driver amplifier. At the same time, the two most widely used amplifier structures are analyzed, and the design idea of ​​the driver amplifier is designed using a two-stage Cascode structure.

Finally, after completing the circuit design and pre-simulation, the layout design of each module of the transmitting front-end chip was carried out and the post-simulation work was completed.

The above is my design idea and research plan. Do you have any questions? "

"..."

"..."

"..."

No one spoke.

But everyone's expressions were a bit extreme.

For example, the middle-aged man who just spoke, the guy sitting next to the camera, and Zheng Xiaofan...

The three of them looked as if they were listening to a foreign language. What… what the hell?
What... structure, what idea...

Who is doing Tai Chi? Who is doing Lion's Roar?
I can't understand it at all.

what are you talking about?
Especially Zheng Xiaofan, he really felt like he was listening to a divine book.

I can recognize each character when they are broken down.

But when put together, the look in his eyes when he looked at Lu Yao was even a little dazed.

But among the others, some nodded slightly, while others remained unmoved.

But everyone looked calm.

Obviously, they understood what Lu Yao said.

In other words, even if they did not understand it before, they had been called out during the May Day holiday before Lu Yao came. After reading Lu Yao's research, they had already determined his design ideas.

From this point of view, everyone at least agrees with it in theory.

Besides, what Lu Yao said were all very basic things... If they didn't understand, they wouldn't be sitting here today.

So, Lu Yao continued:
"Well, next I will divide my design into 5 major design sections and 15 sub-design sections for explanation."

As he spoke, he adjusted the design layout in the software and it appeared on the screen behind him:
"The development of the BeiDou system has gone through three stages. In my opinion, each step can be said to be innovative, and each step is a journey towards maturity amidst difficulties. The highlight of BeiDou-1 is that it can carry out short message communication. Users need to actively send signals to navigation satellites to obtain their own positions, that is, active positioning mechanism. Its service users are relatively limited, only for the Asia-Pacific region. On the premise of retaining BeiDou-1 communication technology, BeiDou-2 has realized passive positioning, which means that it can obtain its own positioning information without sending information to navigation satellites.

At present, according to the 2018th Five-Year Plan, the goal of our third-generation navigation system is to complete all deployments around and expand the service objects to global users. Its positioning performance will be further improved, the regional short message service capability will be further enhanced, and international search and rescue covering our own country and surrounding areas can be carried out. And it is planned to build a more comprehensive, more integrated and more intelligent PNT system around the Beidou system by .

Compared with other navigation systems, in addition to providing high-precision positioning and navigation functions, the unique advantage of the Beidou satellite navigation system is that it has a satellite radio determination service (RDSS), which can actively report its own position, so the RDSS terminal is a complete transceiver. As an important component of the Beidou third-generation satellite navigation terminal, the performance of the RF transmission front-end chip will directly affect the quality of user information transmission and reception.

Next, I will mainly introduce the theoretical basis of the transmission front end, including the design methods of chip system, low-pass filter, modulation mixer, variable gain amplifier and driver amplifier, and give their main performance indicators and basic structures. If you have any questions, you can ask them at any time. Because I can hardly find any information on the current domestic RDSS design on the Internet, I can only go to the Internet over the firewall..."

Having said this, the corner of his mouth suddenly twitched.

Full of embarrassment.

The middle-aged man was also stunned.

At first, he was confused because he didn't understand what Lu Yao was saying, but after he immediately realized that there was something wrong in his words, he also showed a speechless look.

However, he still said:
"Please continue, Lu Yao."

"Well... okay. I can only translate the relevant information about the RDSS chip from some foreign websites... Let me first tell you about the transmitter model I designed. To put it in simple terms, the transmitter is usually located after the digital-to-analog conversion circuit and before the transmitting antenna. The transmitter is generally composed of two parts. The analog baseband circuit is mainly a low-pass filter used to filter out high-frequency components..."

Zheng Xiaofan rolled his eyes implicitly.

Ok.

What you said is really simple.

It was so simple that I couldn't understand a word of it.

At this time, one of the knowledgeable guys suddenly spoke up:
"I see you chose a direct up-conversion transmitter? How does it work? What is your design idea based on?"

Lu Yao was stunned.

After looking at him, he nodded:

"The design idea is to take the chip area into consideration. The advantages of the direct up-conversion transmitter are obvious. Its structure is relatively simple, the power consumption is smaller, and in theory, there is no interference from the image signal, because the structure directly converts the analog baseband signal to the RF signal, and there is no intermediate intermediate frequency signal..."

“But its shortcomings are equally obvious.”

"Yes."

Finally, there was someone with whom he could have technical exchanges. Lu Yao was a little excited and said directly:

"The most important point to note is that because it is a single frequency conversion, the input local oscillator signal of the up-converter is too close to the frequency of the output RF signal. After the modulated signal is amplified by the power amplifier, this strong signal will in turn act on the local oscillator signal generation circuit, interfere with the local oscillator signal, and pull the local oscillator frequency. However, I think its advantages outweigh its disadvantages. After all, it is the most widely used transmitter architecture at present. Please see the figure...

It is not difficult to find that, as I said, the simpler the structure of the transmitter, the wider its applicability, and the wider, the more irreplaceable it is. The goal of Beidou navigation is to be deployed globally, and we can certainly use the superheterodyne transmitter architecture for the satellite navigation terminal transmission front-end chip design.

First of all, its modulation and frequency conversion function is completed twice. The first modulation is performed on a low intermediate frequency, so the orthogonal channels have a better matching degree and the mismatch effect is greatly reduced.

Secondly, because it is a secondary frequency conversion, the frequency of the output RF signal is significantly different from that of the local oscillator signal, so there is no problem with the direct up-conversion architecture, which is that local oscillator pulling will occur, so that the local oscillator port and PA have a higher degree of isolation.

However, the superheterodyne transmitter also has defects. The transmitter has a more complex structure because its modulation and frequency conversion function is completed twice. Secondly, the RF signal after the second frequency conversion contains an image frequency component. To filter out this signal, an external high-Q filter is required, resulting in low integration, greatly increased costs, and increased circuit area. Therefore, the superheterodyne transmitter architecture is generally not used for satellite navigation terminal transmission front-end chip design.

So, that’s why I chose a direct up-conversion transmitter.”

Outsiders can't understand.

But after hearing Lu Yao's explanation, the other people who were familiar with technology all looked thoughtful.

Finally, the middle-aged man who asked the question just now gave his own opinion:
"Well, I approve of your design."

"Ok."

Lu Yao didn't say anything like thank you.

No need at all.

I designed something myself, why should I be grateful for other people’s recognition?
That's not the researcher's style.

"Then let me talk about the various indicators of the front-end chip that I have obtained so far. Some of these indicators are pre-simulation data obtained by our school's graduate student Bai Yao who gave them to his graduate supervisor Professor Sun Liqiang for high-level calculations..."

He mentioned it on purpose.

The reason is also very simple.

Since the senior student and Professor Sun have helped, they deserve to be rewarded.

At the very least, you would get a "footnote" with your name on the paper you published on the chip design you completed.

Of course, this is a joke.

Just based on this high-computing simulation data, it is necessary to list a separate paragraph in the paper to thank these two people for their contributions.

As for other people who don’t understand technology, the following time has completely turned into a boring sitting.

Just as Lu Yao said, this time he had 5 major chapters and 15 minor chapters to talk about his ideas, or in other words... he needed help.

Because from the beginning of the theoretical explanation, the design of the transmitter front-end chip system includes the transmitter architecture, the theoretically achievable chip performance indicators, the system module decomposition method, as well as the performance indicators and structure of the high-pass and low-pass filters, the closed-loop VGA of the variable gain amplifier, the load variable VGA, the transconductance variable VGA, and so on.

Lu Yao was not sure where these people came from, but he welcomed anyone who could help him complete the follow-up work for the success of the model.

Therefore, he had to explain it very clearly to these people so that they could understand what kind of RF chip this was.

Only in this way can he avoid being a hard-working project researcher and take a leading role in the project from the very beginning.

So, time became longer.

It's around 5 o'clock.

It's around 6 o'clock.

It's around 7 o'clock.

Bottle of water.

Two bottles of water.

Three bottles of water.

For more than three hours, while Zheng Xiaofan was about to roll his eyes and said, "Master, stop talking," Lu Yao finished telling him all about his current work progress.

After drinking the last sip of water, he nodded:

"The above is the complete progress of the design of this RF chip. Thank you everyone."

Zheng Xiaofan looked delighted.

Is it finally over?
He looked around subconsciously.

But I didn’t see everyone sighing with relief as I had imagined, saying “it’s finally over”.

Instead, they all frowned when they saw the bigwigs from various research institutes.

What's going on?
(End of this chapter)