(Original title: Radar Life of "Bicycle Academician")
On the campus of Beijing University of Technology, a skinny old man operates an electric wheelchair and commutes home and graduate school between. At the age of 87, he insisted on going to work on time despite having surgery on his leg.
Earlier, he rode to work every day as a unique scenic spot on campus, which was affectionately called "bicycle" by teachers and students academician ”。
He is Mao Erke. From his simple clothes and modest attitude, you can hardly imagine what kind of "treasure" he has created in his life.
22 years old, designed the "First TV Channel in New China"; 30 years old, participated in the design of China's first phased array radar ； 61 years old, elected academician of the Chinese Academy of Engineering; At the age of 75, "Going into the Sea" founded a disciplinary company, which has widely applied cutting-edge technologies in the scientific and technological fields of major national needs
On his way to work for decades, he has written full of ideals, passion and scientific research spirit.
Build top equipment from scratch Research Office
Mao Erke was born in Beijing. As a child, with the change of his father's work, his family moved to Guangzhou, Chongqing and Beijing. In Chongqing, Mao Erke spent most of his youth. In Chongqing private Nankai Middle School, Mao Erke, who was deeply attracted by his father and brother's radio knowledge when he was young, joined the Nankai Branch of China Radio Society. During the Anti Japanese War, many factories moved to Chongqing, the "alternate capital", which also provided more opportunities for radio loving teenagers to "create". They searched for spare parts everywhere, and made things they could use from electronic waste, such as "local telephone", "radio", "campus radio"... The assembled radio works gave young Mao Erke great pleasure and satisfaction.
In 1951, Mao Erke, who was about to graduate from Nankai Middle School, heard that the College of Technology of North China University (the predecessor of Beijing Institute of Technology) would enroll students. Knowing that this school has a major in motor manufacturing, and he is dedicated to learning "electricity related" knowledge, he would like to seize this opportunity. Under the organization of the school, he and four aspiring students went north to participate in the registration and examination.
Mao Er, who successfully passed the exam, can enter the major of motor manufacturing and begin to learn generator and motor design. In 1953, according to the domestic and international situation at that time, the Ministry of Heavy Industry of the People's Republic of China decided to set up the radar specialty in the school to train much-needed scientific, technological and industrial talents for the country. "In this way, I got into radar, and this road will last forever." Looking back, Mao Er said with emotion.
At that time, domestic radar research was still in its infancy.
In 1954, the Department invited Soviet experts to strengthen professional construction. Two years later, under the guidance of Soviet experts, Mao Erke and several students completed their graduation project - the research design of China's first TV test and launch center.
This work was exhibited in the People's Cultural Palace of Beijing in 1957. Although it is only a theoretical and experimental work, the audience can actually see the video signal sent from the main building of Beijing Institute of Technology (the predecessor of Beijing University of Technology) from the screen. This research achievement, known as "the first TV channel in New China", caused quite a stir at that time.
After graduation, Mao Er can stay in school to teach. In 1957, at the suggestion of the competent department, the school began to prepare for the establishment of a radar laboratory. In 1958, Wei Siwen, then the headmaster, applied to the superior for approval of some new radars for the construction of test sites. "At that time, small radars were used in the school experiments, but there was no large model. The superior was very supportive, and approved three large radars at one go. It was amazing, and our radar laboratory became the largest university in China at that time." Mao Erke recalled. These three large radars imported from the Soviet Union were the most important radar equipment used by China at that time.
How can such a complex radar be set up in the school's experimental site? Mao Erke and the experts sent by his superiors undertook the task of assembling and erecting the radar. They compared with the operation guide, kept experimenting and groping, and often worked all day long. In order to save time on the way to and from work, he simply didn't go back to the dormitory and slept in the radar car. After unremitting efforts, Mao Erke and his colleagues finally completed the construction of the radar experimental field. From then on, students can not only learn theoretical knowledge about radar in the classroom, but also have a place to practice.
"Such experimental conditions can be said to be the most advanced configuration in the teaching of domestic universities at that time. Even senior students of Tsinghua University came here to practice and do graduation design."
After 60 years, Mao Erke's face still shows a proud look when talking about the radar laboratory he helped to establish.
National demand is the driving force for research
Mao Er is a prolific inventor in the field of radar research. He could not count the inventions he had made and the awards he had won.
However, he and his students still remember one invention: the new radar "moving target display device" that came out in 1977. What is "moving target display"? Mao Er can explain that in order to use radar to monitor moving objects, it is necessary to distinguish the Doppler frequency of the received radar echo of the monitored object. The Doppler frequency of the moving target is higher, and the faster the movement, the higher the frequency. "After receiving the echo, through the processing of the filter, the objects are distinguished according to their moving speed, and interference objects such as fixed objects are excluded, so that the target flying objects can be 'seen'."
The principle is not difficult to say, but scientists from all countries are struggling to realize it in practice.
In the feedback of radar display, the echo of fixed target is stronger, while the echo of moving target is weaker. "For an immovable mountain and a moving aircraft, the difference between the strength of their feedback echoes can reach more than ten thousand times." How to extract smaller moving targets from the strong clutter interference of fixed objects, and detect their moving speed, the delay line used to extract moving targets is a key device.
In order to find a suitable delay line material, Mao Er and his colleagues repeatedly experimented from the late 1950s to the 1970s. From the mercury delay line used abroad at that time, to the magnetic expansion delay line, to the fused quartz delay line... After more than ten years of efforts, the problem of delay line was finally overcome.
In 1977, the new radar "moving target display device" participated in the electronic countermeasure test organized by the state, showing superior performance and greatly enhancing China's air detection capability. On this basis, the team's project "Analog Digital Hybrid Moving Target Display System" won the second prize of the National Invention Award in 1987. In that year, it was the highest national award in this field.
"The demand of the country is the driving force for our research." To solve practical problems with new technologies and make technological achievements contribute to major areas of national demand is the principle that Mao Zedong has been practicing for decades on the road of scientific research. The development of the "vector miss distance detection system", which successfully solved the major problem of miss distance detection, is the most representative achievement of his practice of this principle.
What is miss distance? Mao Er can explain it in a popular way: when a high-speed flying object collides with the target, it may hit the target, or it may fly past the edge. If it flies over, it needs to know how many angles it deviates and how fast it deviates, so that it can be improved in the subsequent design. "The deviation distance is the miss distance, and the deviation angle is the vector miss distance."
The convergence process of flying objects and fixed targets with a speed of thousands of kilometers per hour can be described as "flash past". How to detect the "deviation" between them at a specific instant is a world-class problem. The West once made a vivid metaphor for miss distance detection, describing it as "finding a needle from a haystack", or locking an "embroidery needle" in the boundless sky.
In the early 1990s, a domestic experimental base proposed the need to study the vector miss distance measurement system, requiring a nearly omnidirectional measurement radar in space, which can measure the direction and distance of the intersection of high-speed moving objects and targets. Mao Er can shoulder the heavy task bravely and lead the team to devote themselves to tackling difficulties.
"One of the key problems encountered in the experiment is to solve the cost problem of the intersection experiment of high-speed moving objects and targets." Limited by objective conditions, it is impossible to use real objects in the early experimental scenes.
How to solve the problem of limited experimental conditions? Mao Erke, a smart man, creatively came up with many "local methods" at that time. For example, the simulation experiment is carried out by means of "hitting slingshot". They made a large slingshot more than one meter wide and launched large steel balls as moving targets for radar tracking experiments. The size of marbles is similar to the hand fitness ball of the elderly, and the speed can reach tens of meters per second, which can not only ensure the experimental effect, but also reduce the experimental cost, so that the project can be carried out smoothly.
In the later stage, in order to make the simulated experimental data more authentic, the team used the experimental rocket with a moving speed of hundreds of meters per second as the moving target for monitoring.
"At that time, the teacher was over 60 years old, and he still insisted on doing experiments with us in the countryside, which would last a day." A student of Mao Erke recalled that whenever the experiment went into a bottleneck and the research progress was difficult, Mr. Mao always encouraged everyone: our principles are OK, and if we stick to them, we will succeed. "The calm and resolute treatment of scientific research has given us all a 'reassurance'."
After 8 years of unremitting efforts, the research group broke through layers of dark clouds and finally completed the radar finalization. Today, this project has been developed into a series of equipment in national key fields. The new radar can make the missile hit the target more accurately and inject new strength into the development of science and technology in national key fields.
Scholars "go to the sea" to feed back scientific research
With the increase of research projects, the scale of radar institute is becoming larger and larger. A series of functions such as material procurement, mechanical and electrical equipment processing, and quality management require more manpower and material resources. "A large number of scientific research tasks have made the team increasingly tense. Like 'firefighters', one project has not been accepted, and another project has been approved." How to solve the operation problem of the radar institute? Mao Erke came up with the idea of establishing a company - to recruit urgently needed talents with the money earned, and to feed back the operation of scientific research projects.
"Our original intention is not to make money, but to solve the urgent talent problem." Mao Erke said that the idea of letting knowledgeable people start companies has caused a great shock in the Institute. Some people support it, some people oppose it, and some people play the "neutral card". Everyone sticks to his or her own point of view and cannot agree on what is right. Once the matter is discussed, it will last for several years.
"If you don't make up your mind, you can't do it, and the talent problem can't be solved." Mao Erke, who is modest and modest, showed extraordinary boldness in starting the company. He strongly rejected the public opinion, and "decided" to take the lead in setting up an enterprise integrated with industry, university and research - Science and Engineering Leke. The research institute is responsible for basic research and principle test. The company realizes engineering and produces formal products.
Today, the enterprise system of integration of production, teaching and research has been popularized in many colleges and universities across the country, and is increasingly mature. But at that time, the people who "went into the sea" to set up companies were still brave "to eat crabs" in colleges and universities across the country. The enterprise led by Mao Erke not only successfully solved the problem of shortage of scientific research talents and unreasonable allocation, but also became a typical case of transformation of scientific and technological achievements in Zhongguancun and even the well-known universities in China.
Walking into the exhibition hall of REC in the National Defense Science and Technology Park of Beijing University of Technology, a number of science and technology projects in different fields show the proud achievements of cutting-edge science and technology transformation and implementation. The airport bird detection and early warning radar, airport runway foreign body detection system, slope deformation monitoring radar... many products based on the transformation of scientific and technological research achievements in national key fields of Mao Erke's team have found more application fields and become important applications closely related to people's life.
Liu Feng is the chairman of Science and Technology Leike, and also a student of Mao Erke. He once won the second prize of the National Invention Award. Since the establishment of the company in December 2009, he has shouldered the leadership responsibility of the company for 11 years.
"The airport bird detection and early warning radar in front of us not only uses the scientific research technology of Mr. Mao's team, but also has all parts designed by Mr. Mao." Liu Feng said that before this technology, the airport generally used manual or physical means to drive away birds, "It is not only a waste of manpower, but also not comprehensive enough. After all, human vision can only see two or three hundred meters away." This radar detected bird situation early warning system can not only identify the distance, position, height, speed and other information of birds, but also alarm the size, species, arrival time and threat of birds, thus reducing the risk of aircraft being hit by birds. "Birds the size of pigeons can be clearly seen within ten kilometers."
In the design process of this detection radar system, Mao Er played an important role in guiding the team. "In 2019, I accompanied Mr. Mao on a business trip. In more than two hours of flying, I reported the design idea of this bird detection radar to Mr. Mao in detail. At that time, Mr. Mao listened very carefully." Liu Feng recalled that after returning to Beijing on a business trip, Mao Erke called him to his office. "He said that after listening to my plan, he seriously thought about it for two days, adjusted and optimized many places, and then came up with a full set of optimization plans."
Liu Feng said that today's radar system, from its appearance to its content, deeply embodies Mao Erke's design concept. For example, according to Mao Erke's suggestion, the system uses the synthetic broadband Doppler principle that he has studied deeply in recent years to identify the characteristics of micro motion. "The characteristic of this kind of micro motion is reflected in the frequency of birds flapping their wings." Liu Feng further explained that for high-speed aircraft, the movement of birds is small, and it is difficult for ordinary radar to identify. By using the principle of synthetic broadband Doppler, the type of birds can be identified by the frequency and characteristics of wings. The system will be popularized and applied in major airports across the country.
The other side slope deformation monitoring radar can monitor the displacement of mountains and mine stockpiles in real time, find the signs of collapse and landslide risks in time, and improve safety assurance. "In the process of this project test, Mr. Mao, who is over 80 years old, has personally visited Xilinhot open-pit mining area in Inner Mongolia, Chongqing Three Gorges Dam Area and other places in remote and difficult conditions for many times." Liu Feng introduced that today, the system has been widely used in many mines, reservoirs, bridges, tunnels, railways and urban buildings in China, and has successfully warned landslide in many places for many times, It is also applied to the long-term monitoring project of Jiuzhaigou scenic spot ecological restoration.
In August 2019, Mao Erke, 85 years old, accidentally fell down on his way to work by bike and had a replacement operation for the femoral joint. However, the elderly academician did not stop his scientific research. Teachers and students of the University of Science and Technology can still see the thin old man who drives an electric wheelchair to work in the Institute on time every day.
"Mr. Mao's persistence in scientific research has inspired our generations of 'radar people'," said Liu Feng.
But Mao Erke said that it is the duty of every scientific and technological worker to do a good job in scientific research conscientiously.
Classification of linked radars
There are many kinds of radar, and the classification method is also very complex. According to the classification of radar signal forms, there are pulse radar, continuous wave radar, pulse compression radar and frequency agile radar; According to the angle tracking mode, there are monopulse radar, conical scanning radar and concealed conical scanning radar; According to the parameter classification of target measurement, there are height finding radar, two coordinate radar, three coordinate radar, friend or foe radar, multi station radar, etc; According to the technology and signal processing method adopted by radar, there are coherent integration and non coherent integration, moving target display, moving target detection, pulse Doppler radar, synthetic aperture radar, tracking while scanning radar, etc; According to the antenna scanning mode, it can be divided into mechanical scanning radar, phased array radar, etc; According to radar frequency band, it can be divided into over the horizon radar, microwave radar, millimeter wave radar and laser radar.
At present, the main research directions and fields of Mao Erke's innovative team include: radar system and signal processing, new system radar, image processing, real-time signal processing, aerospace remote sensing, satellite navigation, etc. The team has won 6 national science and technology achievement awards, more than 20 provincial and ministerial awards, more than 170 national invention patents, and published more than 800 papers included in SCI and EI.
The pictures in this page are provided by Beijing University of Technology
