Chapter 207 What is technology?
It is still a familiar basement parking lot.
Before getting off the bus, Zheng Xiaofan said: "Lu Yao, don't be nervous when you get there later. Say whatever you have."
Lu Yao said in his heart Why am I nervous?
They knew this thing was amazing, so they came to verify it, and they should be nervous.
Because once all models of the RDSS front-end chip are completed and the theoretical verification is passed, it means that its appearance has set a benchmark for all satellite positioning systems around the world. And, most importantly, it also completed the technological era.
While everyone was still lying on the ground to explore the new mode, the RDSS chip flew directly into the sky.
Its various indicators are originally epoch-making things, which is the product of at least three generations of chip technology, industry and technology after 17 years.
Once it starts to be put into use, people in other countries can only catch up with them. At the same time, the breakthrough they may have completed in 2017 and 2018 were already made by the Celestials in 2011, and they were leading in 6 years... Even if they were 60,000 pigs, they would have to catch them for a while.
What's more, "we" standing on the shoulders of giants has been completely ahead of the front line for six years.
He knew this concept very well.
So, he doesn't need to be nervous because he is the creator himself.
The nervous ones should be some of the people who came here today.
Or it is more urgent.
It's time for them to see what technology is.
However, facing Zheng Xiaofan's kindness, Lu Yao still smiled and nodded: "Well, I understand. Brother Fan, who are you here today?"
< br>"This..."
Zheng Xiaofan thought for a while and shook his head:
"You are not easy to ask, and I am not easy to say. But they must be people who know very well about technology."
"Okay."
"Well, let's go." >
The two of them entered the elevator and went upstairs. Soon, Zheng Xiaofan took him to a safety door.
"Take all the electronic devices on your body and put them in that box."
"Okay."
"Remember to turn off the phone."
"I just turned off the phone."
"Yeah."
Soon, Lu Yao, who was alone, followed him through the door. Someone came to the security check immediately and confirmed that the two of them did not carry any electronic products and then released them. Finally, the two came to a door.
Zheng Xiaofan pushed open the door directly, and Lu Yao realized that it seemed like a conference room inside.
The conference room is not small, and it is really enough to be full, and it will probably cost twenty or thirty people.
Seven or eight people have sat inside now.
But I can't tell what they do, because they are all wearing very ordinary clothes.
It's just that the age difference is somewhat different.
Some people look similar to Zheng Xiaofan, and some people are estimated to be in their forties or fifties.
After the two appeared, everyone's eyes focused on this side.
Their desks also have a laptop computer.
At this time, a middle-aged man sitting in front of him spoke: "Student Lu Yao, right?"
"Yes, hello."
Lu Yao greeted him politely.
Zheng Xiaofan had quietly sat aside at this time.
Lu Yao stood by himself in the entire conference room.
As he responded, the middle-aged man nodded with a smile:
"Well, I called you today mainly because the RF chip you created may delay you a little time. But don't worry, the food in our restaurant is delicious."
"Uh …”
Hearing this, Lu Yao knew that he should be an outsider.
There is no other reason.
He uses "radio frequency chips" instead of more specific names, such as RDSS, such as satellite radio measurement service transmission front-end chips, or other names.
Generally speaking, it has never been a vocabulary that people in the academic field like.
It should not be adopted at this moment.
But since this person is the "talent", Lu Yao pretended not to know anything and nodded: "Okay."
Not nervous.
There is nothing cramped.
Seeing this, the middle-aged man nodded: "The computer in front of you is all the information about the chip you designed. The projector has been turned on. We call you today. First of all, I hope you can systematically explain everything about this chip to us. It includes advantages, performance, shortcomings, etc. Finally, the people present will ask questions, please answer truthfully. Is that OK?” "No problem." Lu Yao responded and walked to this computer that looked much thicker than an ordinary laptop with a base like a brick.
He knocked on the space, and the screen lit up, and the light from the projector hit the curtain next to him.
Lu Yao quickly and familiarly opened various EDA software and found that everything he had transferred to this computer.
As for the next...
In fact, he misses it quite a bit.
Give a report.
So he took a deep breath, looked at the people who quickly became "dark" because the projector lighted up, and said directly: "Then... please allow me to tell me what I designed this model. Original intention. First of all, our country has developed rapidly in recent years, and began to fully iterate the Beidou navigation system in 2010. I have read the article. The national plan is to completely complete the full deployment of the third generation of Beidou before 2020. And the front end of the RF transmitting Chips are the most important links of navigation terminals. They are related to the quality of navigation performance, the quality of user information transmission and reception, and the speed of response. Therefore, according to the 2010 Work Report on Major National Science and Technology Development Matters, Beidou's third-generation navigation front-end To transmit chips, we must achieve high integration, low power consumption and high linearity, which is of great significance to the entire third-generation navigation system."
He said, others listened.
No one interrupted, and no one showed any strange look.
In the dim meeting room, everyone was just staring at him.
Including the camera in the corner.
"The model I designed was inspired by a recent unlocked paper on Qualcomm geofilter published by Cheng Yu, a graduate student senior student, inspiring a paper on Qualcomm geofilter published by Cheng Yu, a teacher from the University of Electronics. , adopts CMOS technology to design a front-end chip for satellite radio measurement service transmission. The structure adopts a direct upconversion structure and integrates four submodules: active low-pass filter, modulation mixer, variable gain amplifier and drive amplifier.
In addition, based on the Beidou second-generation navigation transmitter architecture and performance indicators released in 2005, the performance of each module is analyzed to optimize the budget for the transmission link, and four modules are planned. The indicators of the second-order ThomasTow two-stage filter are designed with an active Chebyshev filter, and the Gilbert active dual-balanced mixer is studied , design orthogonal active dual balanced modulation mixer, and use Gilbert unit improved type, namely signal addition type for circuit design, study the implementation method of driving amplifier, select Class AB amplifier for driving amplifier design, and analyze the Two of the most widely used amplifier structures are used to design the design idea of driving the amplifier using a two-stage Cascode structure.
Finally, based on the circuit design and pre-imitation, the layout design of each module of the transmitting front-end chip is carried out and After completion of the imitation work.
The above are my design ideas and research plans. Do you have any questions? ”
"…”
"…”
"…”
No one spoke.
But everyone's expressions were a bit extreme.
For example, the middle-aged man who was talking to him just now, the guy sitting next to the camera, and Zheng Xiaofan...
The expressions of the three of them were like listening to a heavenly book. What...what?
What... structure, what ideas...
Who is practicing Tai Chi? Whose lion roar skills?
I can't understand at all.
What the hell are you talking about?
Especially Zheng Xiaofan, he is really listening to a book of heaven.
The word "全" is known every word that is taken apart.
But when they merged together, he looked at Lu Yao with a look of dazedness.
But some of the other people nodded slightly, while others were unmoved.
But everyone's expressions were very calm.
Obviously, they understand what Lu Yao said.
In other words, even if you didn't understand it before, Lu Yao was already drawn during this May Day holiday before coming. After reading Lu Yao's research, they had already determined his design ideas.
From this point of view, everyone at least recognizes it in theory.
Besides, Lu Yao said something very basic... If they didn't understand, they wouldn't sit here today.
No mistakes, one poem, one post, one content, one in 6, one book, one bar, one read!
So, Lu Yao continued: "So, next I will divide my design into 5 design sections and 15 segmented design sections to explain."
As he said that, he adjusted the design layout in the software and appeared on the curtain behind: "The development of the Beidou system has gone through three stages in total. According to my understanding, every step can be said. It is innovation, and every step is to mature in difficulties. The highlight of the Beidou generation is that it can communicate short messages. Users need to actively send signals to navigation satellites to obtain their own location, that is, the active positioning mechanism. It serves users It is relatively limited and only aimed at the Asia-Pacific region. On the premise of retaining the Beidou first-generation communication technology, the Beidou second-generation has achieved passive positioning, and it can obtain its own positioning information without sending information to navigation satellites.
At present , Our third-generation navigation system, according to the 11th Five-Year Plan, the goal of the third-generation navigation is to complete all deployments around 2018 and increase service objects to global users. Its positioning performance will be further improved, and regional short message service capabilities will be Further enhancement and international search and rescue covering our own country and surrounding areas can be carried out. It is also planned to build a more comprehensive, more integrated and smarter PNT system around the Beidou system by 2035.
< br> Compared with other navigation systems, in addition to providing high-precision positioning and navigation functions, the unique advantage of Beidou satellite navigation system is that it has satellite radio measurement service (RDSS) and can actively report its own location, so the RDSS terminal is a complete one. Transceiver. As an important component of Beidou third-generation satellite navigation terminal, the performance of RF transmitting front-end chip will directly affect the quality of user information transmission and reception.
Next, I will mainly introduce the theoretical basis of transmitting front-end, including chip system , low-pass filter, modulation mixer, variable gain amplifier and driver amplifier design methods, give their respective main performance indicators and basic structures. If you have any questions, you can ask any questions at any time. Because the current domestic RDSS design, I could hardly find any information online, so I could only climb over the wall to go to the external network..."
Speaking of this, suddenly the corner of his mouth twitched.
The eyes were full of embarrassment.
The middle-aged man was also stunned.
At first, he was confused because he couldn't understand what Lu Yao was saying, but immediately noticed something was wrong in his words, and he also showed a speechless look.
However, he still spoke:
"Please continue, Lu Yao."
"This... OK. I can only go to some foreign websites to translate relevant information about RDSS chips by myself... Let me tell you about me first. Designed transmitter model. In simple terms, the transmitter is generally located behind 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 for filtering high frequencies. The weight..."
Zheng Xiaofan rolled his eyes obscurely.
Yes.
What you said is really popular.
It's so popular that I can't understand a word at all.
At this time, some people from the ideology suddenly spoke: "I think you chose a direct up-converter transmitter? What is the principle? What is your design idea based on?"
Lu Yao was stunned.
After looking at him, nodded:
"The design idea is to consider the chip area, and the advantages of direct upconverting transmitter are obvious. Its structure is relatively simple, its power consumption is smaller, and theoretically it does not have interference from the mirror signal, because this structure directly converts the analog baseband signal to frequency. To the radio frequency signal, there is no intermediate-level intermediate frequency signal..."
"But its disadvantages are equally obvious."
"Yes."
There is finally a Lu Yao was a little excited when he was able to communicate with him and said directly: "The thing we should pay attention to is that it is a frequency conversion, so the input local oscillator signal of the upconverter is The output RF signal frequency is too close, so after the adjusted 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 it Advantages outweigh the disadvantages. After all, it is the most widely cited transmitter architecture at present. Please see the picture...
It is not difficult to find that, as I said, the simpler the structure of a transmitter, the wider its applicability, and wider it means that it is irreplaceable. Beidou Navigation’s goal is to deploy globally, and we can certainly use superheterodyne transmitter architecture for satellite navigation terminal launch front-end chip design.
First, its modulation frequency conversion function is completed in two times. The first modulation is performed on an intermediate frequency with low frequency, so the positive traffic channel has a good match, and the mismatch effect is greatly reduced.
Secondly, because it is a secondary frequency conversion, the output radio frequency signal has a large difference in the frequencies of the two compared to the local oscillator signal, so there is no problem with the direct upconversion architecture, that is, the local oscillator will be generated traction, so that the local oscillator port has a higher isolation from the PA.
However, the superheterodyne transmitter also has a disadvantage, which has a relatively complex structure because its modulation and frequency conversion function is completed in two times. Secondly, the RF signal after the second frequency conversion contains a mirror frequency component. To filter this signal, a high Q value filter outside the chip is needed, resulting in low integration. At the same time, the cost is greatly increased and the circuit area increases accordingly. It is large, so it is generally not used to use superheterodyne transmitter architecture for satellite navigation terminal transmission front-end chip design.
So, this is the reason why I chose to directly upconvert the transmitter. ”
Outsiders don't understand.
But several other skilled people showed thoughtful expressions after hearing Lu Yao's explanation.
Finally, the middle-aged man who asked the question just now gave his point of view:
"Well, I agree with your thinking design."
"Okay. ”
Lu Yao didn't say anything thanks or anything like that.
Not needed at all.
Why should I thank others for my own design?
That's not the researcher's style.
"So let me talk about the various indicators of the front-end chip that I have obtained so far. Some of these indicators are handed over by our school's graduate student Bai Yao to graduate supervisor Professor Sun Liqiang for high calculations for the pre-imitation data obtained by high calculations by our school's graduate student Bai Yao to graduate supervisor Professor Sun Liqiang for high calculations. …”
He mentioned it on purpose.
The reason is also very simple.
Since the senior sister and Professor Sun have helped, they should be rewarded.
The most time, I got a "footnote" with the name when I completed the paper I published with my own chip design.
Of course, this is a joke.
Just by relying on this high-calculation simulation data, a separate paragraph must be listed in the paper to thank these two people for their contributions.
In the following time, for other people who don’t understand technology, it has completely turned into a boring long-term sitting.
Just as Lu Yao said, this time he had 5 big chapters and 15 small chapters to say, or... ask for help.
Because from the beginning of entering the theoretical explanation, the transmission front-end chip system design includes the transmitter architecture, the theoretical chip performance indicators and system module decomposition methods. And, performance indicators of high and low pass filters, structure, closed-loop VGA of variable gain amplifier, load variable VGA, transconductance variable VGA, etc., etc.
Lu Yao didn't know where these people came from, but he welcomed anyone who could help him complete the successful follow-up work of the model.
So, he wanted to explain to these people very clearly so that they could understand what kind of RF chip this is.
Only in this way can he not be a hard-working project researcher and have dominated this project from the very beginning.
So, time became longer.
After 5 o'clock.
After 6 o'clock.
It's past 7 o'clock.
A bottle of water.
Two bottles of water.
Three bottles of water.
For more than three hours, in Zheng Xiaofan's "Stop thinking of Master" who was about to roll his eyes, Lu Yao finished all his current work progress.
After drinking the last sip of water, he nodded: "The above is the progress of the entire work of this RF chip design. Thank you everyone." Zheng Xiaofan looked happy.
It's finally over?
He subconsciously looked around.
But I didn't see everyone in my imagination showing a sigh of relief that "it's finally over".
On the contrary, seeing these big shots from various research institutes frowned.
What's going on?
(This chapter ends)