radio communication

Communication mode of transmitting information in space by using radio electromagnetic wave

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Radio communications is to transmit voice, text, data, images, etc electrical signal Modulation on radio waves From space and ground to each other communication mode , a communication mode that uses wireless electromagnetic waves to transmit information in space.

Chinese name: radio communication
Foreign name: radiocommunications
Interpretation: Electric communication

Relative: Wired electric communication
Disadvantages: Confidentiality difference
Applied discipline: signal communication
Features: Long communication distance

catalog

one brief introduction
two origin
three The inventor of radio communication
four Radio communication related
▪ long-wave communication
▪ medium-wave communication
▪ Shortwave communication
▪ Ultrashort wave communication
▪ microwave communication
five Radio service

brief introduction

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The communication mode of using "electricity" to transmit messages is called Electric communication , telecommunications can generally be divided into two categories: one is called Wired electric communication , one is called radio communication. utilize radio waves The communication mode of transmitting information is called radio communication, which can transmit voice, text data And images, etc. Compared with wired electric communication, it does not need to set up transmission lines, has long communication distance, good mobility and rapid establishment; However, the transmission quality is unstable, and the signal is vulnerable to interference or to intercept , susceptible to natural factors, secrecy Poor performance.

origin

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In 1873, britain Physicist J C. maxwell In his book "Theory of Electricity and Magnetism", he summarized and developed the research results of electromagnetic phenomena in the early 19th century, and theoretically proved that electromagnetic processes propagate at the speed equivalent to light in space, and the essence of light is electromagnetic waves, thus establishing the electromagnetic theory. In 1887, German physicist H R. Hertz discovered the electromagnetic wave in the experiment, which verified Maxwell's electromagnetic theory. The establishment of electromagnetic theory and the discovery of electromagnetic waves have created conditions for the emergence of radio communication. In 1895, Russian physicist A C. Popov and Italian physicist G. Marconi successfully conducted radio communication experiments respectively.

The inventor of radio communication

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Radio communication structure diagram

In Britain, people maxwell Be regarded as radio The founder of electromagnetic wave The exists of.

In the United States, some people believe that De Forrest yes radio Father, because he invented triode , and the triode is radio communication The heart of equipment.

stay Russia , only recognize Popov He is the founder of radio communication.

stay Croatia And all understanding Nikola Tesla Most people admit that Tesla is the father of radio.

In the eyes of western scientists, Italians Marconi He was the inventor of radio communication, so he got Nobel Prize in Physics 。

stay Germany , people believe that hertz Is the pioneer of radio, because he was the first to prove the existence of electromagnetic waves. Vibration of electromagnetic wave frequency His unit is named after him.

Who is it invention What about radio communication? It can be said that the invention of radio is the result of the joint research of many scientists and the product of historical development.

Radio communication related

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The greatest charm of radio communication is that radio waves With the function of wave transmission of information, people can save the trouble of laying wires and realize more free, faster and barrier free information exchange and communication. From the characteristics of radio waves light wave Similarly, radio waves can be reflected, refracted, diffracted and scattered. Due to different radio wave characteristics, some radio waves can propagate on the earth's surface, some can propagate in a straight line in space, some can reflect and propagate from above the atmosphere, and some radio waves can even penetrate the atmosphere and fly to distant space.

The frequency (wavelength) used for radio communication is divided into 12 frequency bands (bands), as shown in Table 1^[1] 。

Figure 1 Radio communication frequency band table

according to frequency and wavelength Radio communication can be roughly divided into long wave Communication Medium wave Communication shortwave Communication ultrashort wave Communication and microwave signal communication.

long-wave communication

long wave Communication (3kHz~30kHz). Long wave mainly propagates along the earth's surface (also called Ground wave ）, or on the ground the ionosphere The propagation distance in the waveguide formed between can reach thousands of kilometers or even tens of thousands of kilometers. Long wave can penetrate sea water and soil, so it is mostly used for communication and navigation services at sea, underwater and underground.

medium-wave communication

Medium wave Communication (30kHz ～ 3MHz). The medium wave is mainly transmitted on the ground during the day, and can be transmitted by the ionosphere Reflection propagation. Medium wave communication is mainly used for radio broadcast and Navigation Business.

Shortwave communication

shortwave Communication (3MHz~30MHz). Short wave mainly depends on the ionosphere Emitting Skywave Propagation can be reflected once or several times by the ionosphere, and the propagation distance can reach thousands of kilometers or even tens of thousands of kilometers. Short wave communication is applicable to emergency, disaster relief and long-distance trans ocean communication.

Ultrashort wave communication

ultrashort wave Communication (30MHz~300MHz). The penetration of ultrashort waves to the ionosphere is strong, mainly in straight lines Sight distance The mode of propagation is more stable than the shortwave skywave propagation mode, and is less affected by seasonal and diurnal changes. Due to the wide frequency band, Ultrashort wave communication Widely used for transmission television 、 FM radio 、 radar 、 Navigation 、 mobile communication Etc.

microwave communication

microwave Communication (300MHz~300GHz). Microwave is mainly based on straight line Line of sight propagation However, it is greatly affected by topography, surface features, rain, snow and fog. Its propagation performance is stable, the transmission bandwidth is wider, and the ground propagation distance is generally tens of kilometers. It can penetrate the ionosphere and travel tens of thousands of kilometers to the air. Microwave communication is mainly used for Trunk line or Branch line Wireless communication mobile communication and satellite communication 。

Radio service

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After more than one hundred years of continuous development, various new radio services are emerging, and the types of radio services are increasing. basis ITU The Radio Rules and the Regulations of the People's Republic of China on Frequency Division define 43 radio services in total. These businesses are:

radio communication Business, fixed business, satellite fixed business Aviation fixed business , inter satellite business, space operation business, mobile business, satellite mobile business, land mobile business, satellite land mobile business, water mobile business, satellite water mobile business, port operation business, ship mobile business, aviation mobile business, aviation mobile business (on route), aviation mobile business (off route), satellite aviation mobile business Satellite aviation mobile service (on route), satellite aviation mobile service (off route) radio broadcast Business Satellite broadcasting Business, radio measurement business, satellite radio measurement business Radio navigation Business, satellite radio navigation business, maritime radio navigation business, satellite maritime radio navigation business, aviation radio navigation business, satellite aviation radio navigation business Radio location Business, satellite radio positioning business, meteorological auxiliary business, satellite earth exploration business, satellite meteorological business, standard frequency and time signal business, satellite standard frequency and time signal business, space research business, amateur business, satellite amateur business, radio astronomy business, security business, special business.

History of Radio Communication

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Wireless Communication and Natural Magnet

Beacon tower and wolf smoke

Maybe before the West created the character of God, the industrious and intelligent Chinese people began to enjoy the world of everything God gave them. In 246 BC, the most magnificent building in human history, the Great Wall, appeared on the territory of ancient China. As information Representative buildings delivered—— the Beacon Tower For the first time wireless communication The development path of light and Wolf smoke To people who constantly seek civilization and progress. The beacon tower has lost the role of rapid transmission of war reports, and has become a milestone and witness of the development of ancient civilization.

si'nan

Natural magnet The discovery also became a shining point of profound influence at that time. according to the warring states Guanzi and《 Lu's Spring and Autumn Period 》It is recorded that our ancestors discovered the stone with the magical characteristic of attracting iron tools more than 200 BC, and processed it to make a strange spoon that can indicate the direction—— si'nan 。 This is also the first time that human beings have contacted magnetism This kind of invisible, intangible and miraculous thing works. Later, Sinan was brought to Europe by our ancient envoys, which inspired Europeans to use it to guide navigation.

The discovery of static electricity (1591-1776)

Gilbert (1540-1605)

History doesn't always favor the first comers Europe People on the mainland si'nan On the basis of, he began a more in-depth exploration of the magnet, and beyond the Chinese people to stay in compass On the understanding of. Perhaps the word "coming from behind to get ahead" was created in this way. At the end of the 16th century, when the Chinese were busy participating in the war to defend the Kingdom of Korea invaded by Japan, the Europeans had taken up scientific weapons and started a new journey that was unprecedented.

Cover of On Magnetism

At the end of the 16th century, an English doctor with a scalpel Gilbert (William Gilbert, 1540~1605) physics He became very interested in magnets and static electricity Research started. He spent all his free time in the laboratory, holding various colors of stones and iron pieces to stick, and observed many interesting phenomena. What made him most excited was that the red agate, which had been rubbed against each other, could attract a small piece of paper, making it temporarily free from the attraction of the earth, and avoiding the tragic fate of the apple hitting Newton's head. This is amazing!

He wrote these phenomena in his famous book On magnetism 》And published in London in 1600. In his opinion, electric It is the electrostatic attraction generated by artificial friction materials, and magnetism It is the spirit thing given by God and the natural attraction of natural materials. So he asserts that, electric And magnetism They are two completely different phenomena without any consistency.

His judgment influenced many scientists at that time. It was not until the end of the 18th century that he changed his outlook. Among the scientists who were influenced by him, it is necessary to mention that electromagnetics The founder of, France people Coulomb 。

Tie of Electromagnetic Mechanics (1777-1781)

Coulomb (1736-1806)

In 1777, he was an engineer Coulomb (Charles Augustin de Coulomb, 1736-1806) Mr French Academy of Sciences In order to solve the problem that navigators can't point the compass accurately when they are sailing at sea, the method of hanging a magnetic needle on a small rope to guide is proposed. Mr. Coulomb's brain ran fast, and a flash flashed across his eyes. He tied a hair thin thread to the ceiling beam at one end and a small magnetic needle at the other end. He also brought another small magnetic rod and a small electric rod that can rub out static electricity, and gently swung in front of the suspended small magnetic needle. With this pendulum, the torsion balance and measurement are displayed Electrostatic force And magnetic force Experimental verification method. The romantic Coulomb could hardly restrain his inner excitement and calm down power and magnetic force The great discovery of the relationship between them was written on paper, and in 1785 he deduced the famous electromagnetics Quantitative law—— Coulomb's law 。

Coulomb's law The discovery of electromagnetics The research of the research has risen from qualitative to quantitative scientific level.

The discovery of this law has not yet overturned the previous inference. Coulomb once said, electric And magnetism They are two completely different entities that cannot interact or transform. But this push will electric and magnetism These two "completely different" things pass Dynamics It has established a loose connection.

stay Gilbert Sir to engineer Coulomb start-up electromagnetics In the 170 odd years of basic research, China has completed the ming dynasty reach Qing Dynasty Change of. At the end of the Ming Dynasty, the Western missionaries' insinuation stimulated Chinese intellectuals to pay great attention to and study science. As the basis and potential power of science, Chinese philosophy was far ahead of other countries at that time, almost two hundred years ahead of the West, regardless of materialism or idealism. China's traditional science has begun to experience the process of self innovation, showing unprecedented vitality. Moreover, because intellectuals all over the country are enthusiastic about science and vigorously introduce western advanced technology, China's science is showing an exciting status quo of promoting its strengths and complementing its weaknesses, with a great trend of surpassing the level of western science and technology.

In this critical stage of pupation to butterfly, the ming dynasty China was confronted with the aggression of the Manchu Qing regime, which was still in the stage of barbaric slavery. The social breeding process of scientific civilization evolution was artificially terminated. This cannot but be said to be the sorrow of our nation. and Qing Dynasty Neglect natural science The idea of developing and not absorbing advanced technology eventually led to the collapse of the Qing Dynasty. China lost a very valuable opportunity, but the West emerged in the middle and late 18th century Rousseau 、 Voltaire 、 Montesquieu These three great enlightenment thinkers promoted western science to further surpass itself, leaving the ancient oriental civilization far behind.

Foundations of electrogenerated magnetism (1782-1820)

Oster (1777-1851)

We return to the western world, where science and technology are active. since Coulomb After discovering that law, ampere And Biot and other physicists also believe that electric and magnetism There will be no connection. Such recognition was still very common in the middle of the 18th century. However, opportunities always favor those who are prepared. come from Denmark Of Oster (Hans Christian Oersted, 1777-1851) With the help of a special Cupid's arrow, Mr.

Oster He is a versatile scientist. Physics, chemistry and philosophy are his favorites. Because of this, in his mind, scientific research is always more in-depth and firm because of the enlightenment of philosophy. suffer Kant's philosophy With the profound influence of Schelling's natural philosophy, he has always believed that natural forces can be transformed each other, and through his sixth sense, he did not give up the experimental research on the relationship between electricity and magnetism.

I don't know whether he knew the Chinese proverb at that time: "As long as you have deep kung fu, an iron pestle can be ground into a needle", but he made a historic breakthrough in the development of radio. It may be impossible to verify whether Oster has polished the iron pestle in the laboratory, but he has really made himself and himself because of a needle electric And magnetism 。

Oster electromagnetic effect experiment

In April 1820, at the end of a scientific lecture, Auster made a try Current magnetic effect Experiment. He put a very thin platinum wire on a small wire covered with a glass cover magnetic needle At the top, when the power was turned on, the magnetic needle jumped. This jump surprised the intentional Oster and made him fall on the platform. He did not know that at that moment he had become a scientific matchmaker, and the Cupid arrow made of a small magnetic needle closely linked the electricity and magnetism, the strange men and women.

But in that experiment, the deflection angle of the magnetic needle was too small and very irregular, and this jump did not attract the attention of the audience. Since that day, careful Oster spent three months doing many experiments and found that the magnetic needle would deflect around the current. Above and below the wire, the magnetic needle deflects in opposite directions. Non magnetic substances such as wood, glass, water, rosin, etc. placed between the conductor and the magnetic needle will not affect the deflection of the magnetic needle. On July 21, 1820, Oster He wrote this series of experimental results into a paper entitled "On the Current Impact Experiment of Magnetic Needle", and officially announced to the academic community that he had discovered Current magnetic effect 。 So far, electric And magnetism The secret relationship of was revealed through experiments.

Oster's research electromagnetism The secret of is revealed vividly. His scientific achievements have not touched the eastern China. Thirty seven days after the paper was published, China's Emperor Daoguang ascended the throne. The desolate Qing Dynasty's GNP was 1.22 times that of the whole Europe in that year, but it still could not avoid the fate of being invaded by western powers 20 years later. Well, let's review some happy things and see the creation of electromagnetic theory.

Founder of magnetoelectricity (1821-1855)

Faraday (1791-1867)

The next one to come out is from britain Of Faraday (Michael Faraday, 1791-1867). Faraday was from a poor family when he was young. He had no systematic and formal education, but he studied very hard. In particular, from February 1810 to April 1812, under the influence of 16 lectures on natural philosophy and science, he ignited the desire for scientific research.

I read it in 1821 Oster about Current magnetic effect Faraday was deeply attracted by this new field of discipline after his thesis on electric current The conductor of can be wound magnet Rotate. Since then, he has become one of the famous electricians. adopt Oersted experiment He believes that electricity and magnetism are a pair of harmonious symmetrical phenomena. Since electricity can generate magnetism, he firmly believes that magnetism can also generate electricity. After 10 years of exploration and many failures, Auster finally succeeded on August 26, 1831. This experiment is called "voltaic induction" because it is the induced current obtained by a voltaic battery at the moment of energizing (or powering off) a group of metal coils wound like springs in another group of coils. On October 17 of the same year, Faraday completed the experiment of exciting current in the closed coil when the magnet moves relative to the closed coil, which he called "magnetoelectric induction". After a lot of experiments, he finally realized“ Magnetoelectricity ”The long cherished wish of Electric Age The arrival of.

At the same time, Faraday's mind has been pregnant with electromagnetic wave The existence of and light Is a kind of electromagnetism The outstanding thought of vibration, though it still has some fuzziness. For interpretation Electromagnetic induction phenomenon , he compared power line The drawing of“ Magnetic induction line ”This new concept vividly describes the action direction of magnetism. At the same time, he had a strong doubt about the prevailing theory of action at a distance: "One object can act on another object at a distance through vacuum, without the intermediate participation of any kind of thing, just transfer the action and force from one object to another, which is particularly absurd to me. Anyone who has the ability to think in philosophy will never fall into this fallacy ".

In 1833, he summarized a large number of research achievements of predecessors and himself, and confirmed that five different sources of electricity known at that time, namely friction electricity, voltaic electricity, electromagnetic induction electricity, thermoelectric electricity and animal electricity, were actually electric Five little brothers of the family. Four years later, in 1837, he found that dielectric yes static electricity The impact of the process, which is based on the close proximity Electrostatic induction Theory. Soon after, he further discovered Diamagnetism This new phenomenon. On the basis of these research work, Faraday formed the idea that "electric and magnetic effects are transmitted from one object to another through the intermediate medium", medium Yes“ site ”And he officially“ site ”This historic concept was created.

It is not only Faraday who created history, but also the land where he was born and raised. In 1840, when electromagnetic field When the concept of "" has been accepted by people, the western countries have finally opened the door of the ancient oriental countries, sending in artillery and guns instead of science and technology. They gave the Chinese another "field" - the battlefield. Some people said that China was doomed to be invaded at that time, because it abandoned the development of science and naturally carried the huge cost of ignorance. Fortunately, the Chinese are finally beginning to understand that relying on science can make this nation really strong. and electromagnetics The development of Faraday has entered a new historical height because of the handsome Faraday.

just as Albert Einstein Said, introducing site The concept of Isaac Newton The most important discovery since. The space of Newton and other scholars is regarded as the container of objects and charges; Faraday's space is the container of phenomenon, which participates in the phenomenon. So we say that Lardy is electromagnetic field The founder of the theory.

Electromagnetic wave is coming (1855-1888)

Maxwell (1831-1879)

Faraday The profound physical thought like the vast universe strongly attracts the co-existence britain A young man from Britain Scotland Edinburgh maxwell （ James Clerk Maxwell ，James Clerk Maxwell，1831～1879）。 Maxwell believes that, Faraday Of electromagnetic field The theory is more popular than that at that time electrodynamics More reasonable, he broke in with the determination to use strict mathematical language to describe Faraday's theory electromagnetics He has become a great scientist who has made great achievements in electromagnetics after Faraday.

The cover of Dynamic Theory of Electromagnetic Field

Maxwell began to study electromagnetism around 1855. After studying Faraday's new theory and thought on electromagnetism, he firmly believed that Faraday's new theory contained truth. On the basis of the achievements of predecessors, he made a systematic and comprehensive study of the entire electromagnetic phenomenon mathematics Accomplishment and rich imagination successively published three papers on electromagnetic field theory: On Faraday's Lines of Force (December 1855); On Physical Lines of Force (1862); A dynamic theory of the electromagnetic field (December 8, 1864). These three important papers comprehensively summarize the work of predecessors and his own Electromagnetic field theory It is expressed in a concise, symmetrical and perfect mathematical form, and is reorganized and rewritten by later generations Classical electrodynamics Main foundation—— Maxwell's equations 。 Accordingly, in 1865, he predicted electromagnetic wave The exists of. After theoretical deduction, Maxwell believed that the electromagnetic wave could only be a transverse conduction wave, and calculated that the propagation speed of the electromagnetic wave was equal to light speed 。 At the same time, his inspiration prompted him to draw an important conclusion: light yes electromagnetic wave A form of. This reveals the connection between light phenomenon and electromagnetic phenomenon. Maxwell compiled the arguments and conclusions of these theories into a volume, and published a famous scientific book in 1873《 electromagnetics Treatise on Electricity and Magnetism, which systematically, comprehensively and perfectly expounds the theory of electromagnetic field. This theory became Classical physics One of the important pillars of.

Hertz (1857-1894)

This masterpiece was later handed down Germany , deeply touched the heart of a German physicist. He is hertz （ Heinrich Rudolf Hertz ，Heinrich Rudolf Hertz，1857-1894）。 Hertz at University of Berlin When learning physics Helmholtz Encouraged research of maxwell Electromagnetic theory. At that time, the German physics community believed that weber Of power And magnetic force The theory of instantaneous transmission, so Hertz decided to prove it by experiment weber And maxwell Whose theory is correct. In 1888, hertz The experiment is successful, which verifies the existence of electromagnetic waves. and maxwell Therefore, the theory has gained supreme glory.

Hertz pointed out in his experiment that, electromagnetic wave Can be reflex 、 refraction As visible light 、 Thermal wave The same was polarization 。 Through experimental calculation, he found that electromagnetic wave The propagation speed of light speed So as to fully verify the correctness of Maxwell's electromagnetic theory.

In January 1888, Hertz summarized these achievements in On the electric effect of the propagation velocity of moving. After the announcement of the Hertz experiment, the world's scientific community was shocked. from Faraday start, maxwell Only then did the summarized electromagnetic theory achieve a decisive victory. and radio waves It is also named hertz Wave.

In 1888, it became a milestone in the history of modern science. Hertz's discovery has epoch-making significance. It not only confirms the truth of Maxwell's discovery, but also creates radio electronic technique A new era of. From the perspective of the Chinese people, this year is also very historic. Radio, 1888, go! Send! Send!

The departure of radio (1889-1896)

Popov

In 1889, in a famous speech, hertz It is clearly pointed out that light is an electromagnetic phenomenon. So far, radio This concept also gradually came into the vision of scientific research, and his discovery was then applied to the development of human radio industry. This time, God touched his hand to three countries - the United States Italy and Russia Later, Jushang once again confirmed the ancient Chinese maxim.

In 1893, Nikola Tesla of Croatia Missouri, USA St. Louis First public display radio communication 。 However, the historic radio transmission was Russia scientist Popov and Italy Of Marconi Completed.

In 1888, hertz The discovery of Popov （ Alexander Stapanovich Popov ， Александр 　 Степанович 　 Πопов， 1859~1906). In 1889, he repeated Hertz's experiment many times and proposed that "electromagnetic waves can be used to send signals to a distance". In 1894, Popov improved the Hertz experimental device by using the detector The discharge phenomenon in the atmosphere is recorded through the overhead wire. This is the first in the world Radio receiver 。 On May 7, 1895, Popov performed the "thunderstorm indicator" he created at the annual meeting of the Russian Ministry of Physics.

One year later, on March 24, 1896, Popov again University of Petersburg There was a performance between two buildings 250 meters apart radio communication He and his assistant had a formal radio transmit Morse code Performance. Popov Receiver It was placed in the meeting hall of the Physical Society, and his assistant transmitter It is installed in the Forest College. When the time came, the assistant calmly sent out the signal, and the receiver on Popov's side clearly received the signal. At this time, the president of the Russian Physical Society wrote the received letters on the blackboard one by one. Finally, a line of letters appeared on the blackboard: "Heinrich Hertz". This is the first in the world wireless telegraph In memory of Hertz, the discoverer of electromagnetic waves.

Marconi (1874-1937)

Now let's introduce another great person—— Marconi (Guglielmo Marconi, 1874-1937). Marconi was born in Italy A middle-class family in Bologna. Because his family was very rich, his parents specially asked a tutor to guide him in his study.

Marconi's view on physics and electromagnetics Has a strong interest. In 1894, the year when Hertz died, Marconi had just turned 20. He read Hertz's experiment and Lodge's report in the electrical magazine. Since he was young, he liked to play with coils and electric bells, so he went into the study of electromagnetic waves. In his opinion, since Hertz can detect electromagnetic waves several meters away, as long as there is a sufficiently sensitive radio wave detection device—— detector It is also certain that electromagnetic waves can be measured at a farther place. After many failures, he finally took a gratifying first step.

He installed a radio transmitting device upstairs and placed it downstairs detector , and let detector Connect with the bell. As soon as he connected the power upstairs, electromagnetic wave And passed through detector , let the downstairs bell ring quickly. In the evening, when his father saw this novel device, his anger and discontent that had been held in his stomach were forgotten, and he was no longer called "unrealistic dreamer". From then on, his father began to give his son financial aid, and let him concentrate on experiments.

Marconi's confidence grew after he first realized the joy of victory. He collects a lot of data and articles. No matter whether the author of these articles is famous or unknown, he will patiently read and carefully analyze the articles that are useful and enlightening to him. He analyzed each family's shortcomings clearly, gathered each person's strengths, and improved his precious machine.

Schematic diagram of Marconi detecting radio waves

In the summer of the next year (1895), Marconi completed another very successful experiment. In autumn, the experiment made great progress. He unfolded a kerosene barrel and turned it into a large iron plate as a transmitting antenna. Hang the antenna of the receiver on a big tree to increase the sensitivity of the received signal. He also found that metal chips can firmly grasp the radio signal in the air through a device, so he also improved Rocky's metal powder detector to make it more outstanding. Marconi added a small amount of silver powder into the glass tube, mixed it with nickel powder, and then discharged the air from the glass tube. In this way, the transmitter increases the power, and the receiver also increases the sensitivity of detecting radio waves. He put transmitter On one side of a hill, Receiver It is placed in the home on the other side of the hill. When sending signals to his assistant companion, he waited nervously for the signal receiver. Suddenly, the bell made a clear sound. The sound was more pleasing to his ears than the moving symphony, and made him almost jump up.

Marconi succeeded!

Marconi is in front of the telegraph

The distance of this experiment reached 2.7 kilometers, which was a historic breakthrough. At that time university of bologna He is only 21 years old. This was an amazing feat at that time, and since then Marconi has embarked on a career path. The good news arrived britain In the ears of William Puls, the chief engineer of the post office, Marconi came to England to develop in the future.

In 1896, Marconi held his humble radio transmitter Came to the center of the industrial revolution—— britain , on London Started his own entrepreneurial career. In June of this year, he used electromagnetic wave Having conducted a radio communication experiment about 14.4 kilometers away, he once again showed his talent. In July 1897, "Marconi Radio Telegraph and Signal Co., Ltd." (later renamed "Marconi Radio Telegraph Co., Ltd.") named after him was founded.

It should be noted that, Marconi and Popov about radio communication All of the inventions were made independently in a short period of five or six years from 1895 to 1901. So it can be said that the door of radio application is Marconi and Popov Simultaneously opened.

Radio application first appeared (1897-1910)

Spark transmitter

Marconi After the establishment of the company, the development of radio has entered a new era. From then on, it is no longer a single fight, but a group of people's thoughts. The spark of wisdom ignited the extension of radio towards a broader scope.

In 1897, Popov Under orders in Russia Baltic Fleet Some of naval vessels Established on radio communication Equipment.

In 1897, transmission without wires Code Our radio communication has been fully recognized by the world. Since then, the distance of radio communication has been increasing.

In 1898, Marconi's wireless telegraph It is used for commercial communication for the first time. In 1898, a successful cross sea test of wireless telegraphy was carried out on both sides of the English Channel, with a communication distance of 45km; In 1899, another communication link with a distance of 106 kilometers was established.

In 1899, Popov radio investment military The application has established a radio communication network of more than 40 kilometers.

In 1900, Marconi officially obtained coil and Variable capacitor Constituent tuning The circuit patent (the famous patent No. 7777), tuning circuit is widely used in all kinds of radio communicators.

In October 1900, Marconi set up a powerful transmitter in Britain, which used a 10 kilowatt sound spark telegraph transmitter. In December 1901, Marconi successfully received the Atlantic The radio telegraph on the other side completed the radio long-distance communication 3600 kilometers across the Atlantic Ocean. Because of his outstanding contribution, in 1909 The nobel prize in physics Italian physicist awarded to Marconi Wireless Telegraph in London, UK Marconi (Guglielmo Marconi, 1874-1937) and Braun (Karl Braun, 1850-1918) to recognize their contributions to the development of wireless telegraphy.

From the United States to Britain in 1903《 The Times 》Deliver news by radio and see the newspaper on the same day. By 1909, wireless telegraphy had already played a great role in the communication industry. Since then, most of the military fortresses and seaports of many countries have been equipped with radio equipment, and wireless telegraphy has become a global cause.

During this period, in 1904, when the British J. A· Fleming (John Ambrose Fleming, 1849-1945) invented the first vacuum diode "Fleming" that can determine whether there is one-way current Vacuum tube ”When, an opportunity for future development appeared.

J. A. Fleming (1849-1945)

In 1906, Lee de Forest (1873-1961) of the United States added a grid grid to the Fleming vacuum tube and made the first triode vacuum tube. Named "Audio" triode detector It is very effective. It can capture the radio waves in the air in front of people with invisible hands voice The form of electromagnetic wave Appears and opens radio It has officially entered a new chapter in the communication world. He was pleased to announce: "I have found an invisible empire in the sky." Mr. Foster was known as the "father of radio" by Americans. Although the debate about who is the real "father of radio" has not stopped, it does not prevent us from paying homage to these pioneering scientists.

Lee de Foster (1873-1961)

In the same year, there was a sound for the first time radio broadcast The voice of female singers, violin playing and story telling added a ray of happiness to the Christmas of that year.

At that time, China was gradually influenced by the West, and published some radio publications, which promoted the start of radio in China. On May 2, 1897《 Current affairs 》Volume 25 publishes an English translation《 wireless telegraph 》Became radio technology The beginning of official introduction into China. Since then, radio technology represented by wireless telegraphy has opened the prelude to spreading to the Chinese people at the end of the Qing Dynasty through periodicals.

Radio, War and Peace (1910-1950)

At that time, people depended on radio letter And expensive Wired telephone In the age of communication, it played a revolutionary role. Since then, people can freely set up radio communication stations to complete communication at any two or more points, which greatly improves the communication space of people, so that the era of horses and messengers delivering orders is gone forever. The wheel of history entered the twentieth century, radio communication It also played an important role in military affairs.

Early military radio

In 1914, the First World War When it broke out, radio immediately became the new favorite of generals. It enables the troops in the field to communicate quickly, so as to speed up the movement of war and take the initiative. However, wireless information is encryption After passing Morse code When transmitted in the form of radio waves, each password carried message They all leak out, which enables the enemy to intercept a large amount of continuous war report information. On August 5, divers on the British ship "Talgonia" cut off the German cable under the North Atlantic Ocean. This prompted the German side to switch a lot of communication from cable to radio. Germany became a victim of the war because of the role of careless radio, which leaked key information.

the Second World War Before the beginning, radio had developed to a certain extent, and smart Britons and Americans played an important role. They invented the early television and radar And then it can transmit encrypted intelligence and find out the enemy situation during World War II. Occurred on December 7, 1941 Pearl Harbor The attack made the United States suddenly enter a state of war. At that time, about 60000 Americans owned Radio station License. About 90% of them are serving their war or related military industry or teaching. This laid the foundation for the victory of the United States.

During the two world wars, radio enthusiasts in various countries never gave up their careers Amateur radio Communication is booming. In 1945, the war ended and the development of radio ushered in a period of peaceful development. Another application worth mentioning is radio broadcast 。

In 1910, one of the "father of radio" mentioned just now, Foster rebroadcast Enrico Caruso's singing performance from the Metropolitan Opera in New York. Then he broadcast important news in the newspaper and became the first broadcast newsletter. For a while, the "voice of the air" caused a wide range of interesting conversations.

The first radio station of the Red Army of China

August 31, 1920, United States Detroit Establish a pilot radio station , broadcast the governor's election news, known as the first broadcast news. On November 2 of the same year, American amateur radio enthusiast Frank Conrad built the world's first broadcasting station 。 Since then, France, Britain, Germany, Italy and Japan have established their own broadcasting station 。 You can still hear several familiar names: bbc BBC 、 Japan Broadcasting Association NHK , etc.

Not long after, China, India, Canada, Australia and other countries radio broadcast They also came out one after another. Especially in China, after a short period of Republic of China In the long and bitter process of war and chaos radio station The Chinese people are increasingly inseparable from the radio as a friend. broadcasting station and radio Even become a member of the Communist Party to pass on secrets intelligence As shown in the spy film Latent, the tools of. It can be said that in such an era, whether in war or peace, the new thing of radio has been recognized and entered a period of rapid development^[2] 。

Radio Development (1950-1980)

Satellite relay communication

After World War II, the role of radio has been fully accepted by people. Therefore, we have to mention an international organization—— international telecommunications union （International Telecommunication Union）。 ITU We will not go back to the history of radio, but since its establishment on May 17, 1865, it has been playing an important role in international coordination and sharing of radio. On October 15, 1947, the International Telecommunication Union became the United Nations A specialized agency of Geneva , has not moved until now. Since then, the development of radio has put on wings, flying higher and farther.

The early people Electronic components 20 kHz to 30 MHz shortwave The frequency completes radio communication. However, since the 1960s, people have expanded the frequency to 150MHz and 400MHz, and the quality of radio transmission has become increasingly high. At the same time, technological progress—— transistor The emergence of mobile radio has made a great progress towards miniaturization, and the effect has also been significantly improved. The coverage of the network makes radio have to adopt relay Communication to ensure that radio receivers thousands of kilometers away can enjoy the same signal quality as radio transmitters. Therefore, relay communication, which took shape in 1939, began to shine 11 years later in 1950 and spread in the United States like popular songs. With the relay system running through the whole country, a new revolution is going on quietly. Let's sincerely thank the radio lovers in Canada for leading this new revolution. This is the group they created in 1978 Data exchange Communication technology experiment. This also benefits from digital computer Invention of.

In March 1980, the United States began to use a convenient method to convert people's text symbols into computer symbols ASCII code 。 And then personal computer It became popular in the United States. The combination of personal computer and radio has ignited people's interest in packet data exchange communication and other data communication The passionate pursuit of.

At this point, Integrated circuit Technology Microcomputer and microprocessor The rapid development of, and Bell Lab Launched honeycomb The concept of the system and the application of its theory in practice have led to the development of land mobile phone systems in the United States, Japan and other countries. It can be said that the radio at this time Mobile communication system It has really entered the personal field: the representative ones are American AMPS (Advanced Mobile Phone System) system, British TACS System, Nordic (Denmark, Norway, Sweden, Finland) NMT System, Japan's NAMTS system, etc.

Because radio can mobile communication These systems have been put into commercial use. In the United States, Japan, the United Kingdom, West Germany and other countries began to use car public wireless phones. Special mobile wireless telephone systems have also sprung up, widely used in public security, fire protection, taxi, news, scheduling and other aspects. At this time, mobile communication Gradually into the daily life of the public, people have seen the future Personal mobile communication The dawn of. At this time, mobile communication began to develop rapidly towards miniaturization, convenience and personalization. After the reform and opening up in 1979, China began to build a national microwave Trunk trunk transmission network is used to serve the economic construction tide of reform and opening up. Radio applications have also shifted from military applications to civilian applications.

Digital Survival (1980-2010)

U.S.A Massachusetts Institute of Technology Being Digital, written by Professor Negroponte in 1995, described the 20th century information technology And the development of ideas Digital era The is coming. radio Of course, the development of has become one of the pioneers of digital development. because simulation Radio communication can not be as regular as grid arrangement in signal transmission and data processing, which increases the difficulty of information processing and reduces communication efficiency, thus restricting the development of radio. But it doesn't matter. We still have a trump card—— digitization signal communication 。

Great mathematicians have proved that if you cut a continuous analog signal like diced meat, you can cut it from birth to retirement, but only cut it from the beginning. What a sad thing it would be. It's really a cup. Therefore, we can cut the simulated radio signal in a limited way as long as we grasp its most typical characteristics. This has two advantages. First, we have grasped the key points to ensure limited quality reduction; Second, limited radio signals can be used to store more content. At the same time, digital radio has unique advantages in security and other aspects. This is why countries are developing radio communication in the direction of digitalization.

Since the mid-1980s, Digital Revolution Here we go. from shortwave reach ultrashort wave , as long as it can be added to a certain part of wireless communication computer or digital signal processing , then this part becomes the practice place of digital radio.

In 1983, Owen Garriott, a digital radio enthusiast, took people's dream to astronaut I'm seated space shuttle , soaring into the sky. stay Space Owen used a 2-meter equipment to carry out nearly 300 times of shortwave Digital radio communication. It's exciting.

In 1991, Third generation mobile communication system （ 3G , 3rd Generations)“ mobile phone ”Call in front of the mobile operator. They have begun to prepare for the establishment of more advanced wireless communication systems. This time, although it started as a simulation idea, after continuous discussion, we finally reached an agreement to move towards digital.

beeper

At that time, it was 20 years later than that of western developed countries beeper It has sprung up in China. Then came“ mobile phone ”。 This telephone is big and heavy, and it is not cheap to use, but people at that time took it as a symbol of identity, and still remember it. This is Mobile communication system For the first time, it is widely used in China. Although it follows foreign standards, at least the Chinese people have begun to accept the world's most advanced technology as their ancestors 400 years ago.

In May 2000, ITU Announced 3G Standard, but only WCDMA and CDMA2000 Our radio workers are still working hard to catch up with the world trend day and night TD-SCDMA Also included international standard ranks. This is a great action concerning national dignity. It can only succeed, not fail. In 2003, the efforts of the Chinese people were recognized, and ITU published this standard. In August 2008, 3G networks began to operate in China. Until now, we can still see that this process is in progress.

In the past 20 years, digital radio communication has also shown its talents in other fields. In the fields of broadcasting, transportation and culture, all of them are leaping forward at an unprecedented speed because of the new air brought by the digital revolution. When you take the 350km/h high-speed train, you can call your relatives and friends on the train and watch the mobile base station Of Beijing Olympic Games When the opening ceremony was broadcast live, you were fully integrated into this new world.

Radio enters China

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The application of radio technology in China has a history of more than one hundred years. As early as 1897（ Guangxu reign period Twenty three years), by Huang Zunxian 、 Liang Qichao Journals founded by《 Current affairs 》Then publish the translation -《 wireless telegraph 》, this article introduces the year 1896 Marconi The word "wireless telegraph" came into being in China after the experiment of wireless telegraph communication. From the end of Qing Dynasty to Republic of China Period, wireless telegraph 、 radio broadcast The time when radio services entered China basically kept pace with the international community.

☆ At the beginning of 1899, Qing government Bought several Marconi Quenching spark radio, installed in Guangzhou, Guangdong and Guangxi Governor's Office It is also used for long-distance military command in the fortresses such as Makou and Weiyuan, as well as in the ships of the Nanyang Fleet. This is the first use of wireless telegraph service in China.

☆ In 1906, due to the interruption of submarine cables in Qiongzhou, Guangdong, the Qing government set up radio machines in Qiongzhou and Xuwen, and opened civil wireless telegraph communications. This is the beginning of China's civil radio communication.

☆ In 1919, the government of the Republic of China established Beijing Radio and Telegraph Bureau, and used Radio receiver Receiving from European and American countries radio broadcast Journalism.

☆ In October 1926, radio expert Liu Han founded the first radio station run by the Chinese themselves—— Harbin Radio stations.

☆ In March 1927, Shanghai Xinxin Company opened the first business in China Radio station 。 Since then, Tianjin and Beijing have also established radio stations.

☆ Before and after 1933, several big cities such as Shanghai, Hangzhou, Jinan, Tianjin, etc. appeared one after another Amateur radio station 。 Chinese Amateur radio This is where the activity starts.

Red Communication During the Revolutionary War

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overview

The radio industry in New China was established by Agrarian revolution The "half of the radio stations" in the period started and continued to grow. From the arduous the Red Army Period Counter-Japanese War Period to magnificent War of Liberation During the period, the red communication soldiers under the leadership and command of the CPC Central Committee have repeatedly made outstanding achievements. Looking back on those hard times, some precious Radio station , one after another across the sky Red radio wave And played a vital role in the victory of the Chinese revolution for our party and army.

During the anti "encirclement and suppression" period, half of the radio stations started

After 1927, the Communist Party of China in Jiangxi Jinggang Mountains The first rural revolutionary base was established. But in the early days the Red Army From the very beginning, they were surrounded by the enemy on all sides, and the contact between the base areas mainly depended on very inconvenient underground transportation.

At the end of 1930, the Red Army won a big battle against the first "encirclement and suppression" in Longgang, Yongfeng, Jiangxi Province. It not only captured Zhang Huizan, the commander of the enemy's 18th division, but also obtained half of the radio stations that can only receive letters but not send them. Mao Zedong 、 Zhu De He attached great importance to the captured radio stations and decided to make use of this half of the radio stations to start his own business, which was founded in mid January 1931 Red Front Army The first radio team of the headquarters is composed of Wang Zheng Serve as team leader. During several counter campaigns against "encirclement and suppression", all front armies of the Red Army captured dozens more the kuomintang Military radio station, established for the Red Army CPC Central Committee The radio communication network has laid the foundation.

The establishment of the radio communication network has enabled our party and army to open and close at any time, winning the initiative in the military struggle. In January 1931, Mao Zedong and Zhu De clearly pointed out that "radio work is more important than any local technical work."

Helping the Red Army out of the tight encirclement during the Long March

"Hengduanshan is a difficult place to travel... Soldiers walk around the world with both feet and cross the Chishui River four times to produce strange soldiers... Chairman Mao's use of troops is like a god." The Song of the Long March vividly shows that The Long March of the Red Army During this period, the mobile and flexible fighting style and Mao Zedong's commanding art of using arms like gods. During the Long March, the reason why the Red Army broke through the encirclement repeatedly in the face of the enemy's encirclement and interception was that radio communication and Radio reconnaissance Work is inseparable.

In October 1932, after the start of the Long March of the Red Army, the major strategic decisions of the CPC Central Committee and the Central Revolutionary Military Commission were almost all communicated to the troops in time through radio communication. CPC Central Committee and Central Red Army leave Zunyi Later, Zeng Crossing Chishui for four times River Skilled crossing Jinsha River , get rid of hundreds of thousands the kuomintang The reason why the Red Army encircles and intercepts the enemy is that telegraph And fully mastered the enemy's force deployment and whereabouts. Because of this, the Red Army can always find a gap in the encirclement set up by the Kuomintang army and successfully get out of the predicament during the ten thousand mile journey.

After the Red Army's Long March ended, Mao Zedong spoke highly of and praised the Second Bureau of the Military Commission in charge of radio technology reconnaissance, saying, "Without the Second Bureau, the Red Army's Long March would be unimaginable. With the Second Bureau, we would walk at night with a lantern."

During the Anti Japanese War, the Red Communication Network was woven

On July 7, 1937, Lugouqiao Incident After occurrence, China From then on, the curtain of the War of National Liberation against Japan began. During the Anti Japanese War, our party and army further accelerated the construction of the red communication network according to the development of the situation and the evolution of the war situation.

By 1940, there were more than 160 radio stations in the war zones in North China, and nearly 60 radio stations in the armed forces in Central China and Jiangnan Yan'an A number of special radio networks and radio communication networks at all levels centered around Yan'an have been initially established to communicate with the party, government and army, radiate all forces, bases and guerrilla areas throughout the country, and complete the establishment of the CMC's strategic command and communication system. At the same time, hundreds of cadres who are proficient in telegraph business have been selected to Kuomintang controlled area and Daily occupation area The Party's secret radio stations in major cities helped carry out the work and effectively cooperated with the armed struggle in the front anti Japanese battlefield.

In view of the important mission and role of radio communication, on October 10, 1941, Mao Zedong wrote an inscription for "Communication Soldier": "You are a scientific clairvoyant."

During the War of Liberation, telegrams spread the overall situation

War of Liberation During this period, whether the CPC Central Committee moved to northern Shaanxi or implemented the decisive three famous battles before foundation of People's Republic of China Radio communication has played a vital role and become the killer weapon of the CPC Central Committee in planning strategies and controlling the national war situation.

In the difficult period of moving to northern Shaanxi, radio became the only communication tool for the CPC Central Committee and the Central Military Commission to command the front line. Under the dangerous situation, once the central authorities were stationed, Mao Zedong immediately commanded the front line through radio and telegraph.

In the decisive stage of the victory of the Chinese revolution, Mao Zedong was in Pingshan County, Hebei Province Xibaipo In an old residential building in Beijing, with telegrams, we coordinated and directed the interlaced progress of Liaoshen Beiping and Tianjin and Huaihai The three major campaigns created the miracle of wiping out 1.54 million enemies in 142 days. According to statistics, there were 408 telegrams written and dictated by Mao Zedong in Xibaipo that year, and thousands of front line telegrams read. Only on Liaoshen Campaign During this period, Mao Zedong planned a total of 77 telegrams, including more than 50 telegrams directing the battle of Jinzhou. Therefore, Zhou Enlai Zeng said with emotion: "In Xibaipo, we don't send guns, food or people, just send messages every day!"

Introduction to EW

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Electronic countermeasure refers to the electromagnetic spectrum struggle between the two sides using electronic equipment and materials. Electronic countermeasures are also called "electronic warfare" or "electronic warfare". Operational actions conducted by hostile parties using electronic technology. The purpose is to weaken and destroy the use efficiency of the enemy's electronic equipment, so as to protect the effectiveness of our own electronic equipment to be brought into full play. Including radar countermeasures, radio communication countermeasures Photoelectric countermeasure Etc. Basic contents include electronic warfare reconnaissance , electronic interference and electronic defense. Electronic countermeasure is an important means of modern warfare.

With the development of science and technology, the electronization of the military has been rapidly improved. The aircraft, ships, satellites, and those used to destroy radar and other devices are specially used for electronic countermeasures Antiradiation missile The successive emergence has greatly improved the status and role of electronic warfare, and electronic warfare has gradually become active on the stage of modern warfare as a combat means directly used for attack and defense. The traditional land, sea and air warfare has developed into the "multi-dimensional three-dimensional warfare" of Canada, space and electricity. The new warfare method characterized by "soft killing" of electronic warfare runs through the whole process of war.

Electronic counter measures (ECM) are called "electronic warfare" by the United States and NATO countries, and "electronic warfare" by Russia. Electronic countermeasure technology It mainly refers to the use of special electronic equipment, instruments and electronic strike weapon systems to reduce or destroy the working efficiency of the enemy's electronic equipment, while protecting the normal performance of its own electronic equipment. electronic countermeasure

Its basic means are electronic reconnaissance and anti reconnaissance, electronic jamming and anti jamming, anti radiation destruction and anti destruction. The main contents of electronic countermeasures include electronic reconnaissance, electronic attack and electronic defense. The essence of electronic warfare is the struggle between the enemy and us for the control of electromagnetic spectrum (that is, electromagnetic control). Electromagnetic power, like air power and sea power, refers to the control over the electromagnetic spectrum within a certain space-time range. Seizing the power of electromagnetic control means that one can use the electromagnetic spectrum freely without being threatened by the other party; At the same time, it deprived the other party of the right to use the electromagnetic spectrum freely. The electromagnetic power has its space-time characteristics. In general, the party at a relative disadvantage is not helpless. If scientific command and reasonable concentration of forces are made, it can seize local electromagnetic control power in a certain time domain or region.

The scope of electronic countermeasures includes three fields in the frequency domain: acoustic countermeasures, radio frequency countermeasures and optical countermeasures (photoelectric countermeasures). From space, it can be divided into ground, sea, air, space and underwater. In terms of equipment used, it can be divided into radio Communication countermeasure , radar countermeasure, photoelectric countermeasure, C3I system electronic countermeasure and other technologies^[2] 。

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