Invention
Professor Alex Zeto from Berkeley said that the nano radio they developed was 100 billion times smaller than the first commercial radios. Although the nano radio is currently only set as a radio receiver, it can also be changed to a radio transmitter. He said that nano radios will have a wide range of applications, and the development of nano radios may also lead them to open up new application areas. With only one nanotube, all the functions of an ordinary radio with numerous components can be realized. Because nanotubes are so tiny, they vibrate quickly as soon as they encounter radio signals. Connecting this nano antenna to the peripheral circuit, we can manipulate it to complete channel selection, amplify, separate audio components from other components of radio waves (demodulate), and finally enable us to hear "Beach Boys" or Music by George Frederick Handel.
How it works
The antenna of an ordinary radio receives signals through electromagnetic effects, that is, electromagnetic waves induce current in the antenna, but the antenna itself is always stationary. In the nano-radio, the nanotube is an extremely slender, light-weight charged object, and the incident electromagnetic waves are enough to push it back and forth mechanically. "The nano world is magical and very different from the macro world," Zetel pointed out. "The nanodevices are so small that the effects of gravity and inertia have little influence. On the contrary, the residual electric field plays a major role in these gadgets." Nano The vibration of the tube will change the current flowing from the end of the nanotube to the counter electrode-called field emission current in technical terms. Field-emission (field-emission) is a quantum mechanical phenomenon, that is, a small applied voltage can cause a large electron stream to be emitted from the surface of an object (such as a needle tip). Based on the working principle of field emission, people not only expect nanotubes to act as antennas, but also hope that it can complete signal amplification tasks. A small amount of electromagnetic waves incident on the nanotube will cause the vibrating free end of the nanotube to release a large stream of electrons. This stream of electrons will amplify the incident signal.
The next step is demodulation, which is to extract useful information such as sound or music from the carrier wave transmitted by the radio station. In amplitude modulation (AM) radio broadcasting, this separation is achieved by a rectifier filter circuit. This circuit only reacts to the amplitude of the carrier signal and completely ignores the frequency. Zetel's team speculates that the nanotube radio can also achieve this function: when the nanotube mechanically vibrates with the carrier frequency, it will also respond to the information component encoded in the carrier. Coincidentally, rectification happens to be an inherent characteristic of quantum mechanical field emission. This means that the current flowing out of the nanotube changes only with the code component (that is, the modulated information component) in the signal, and the carrier is rejected. The realization of this function does not require any additional circuits.
Simply put, the arrival of electromagnetic signals will cause the vibration of the nanotubes, and the nanotubes act as antennas in this process. The nanotube vibrating end amplifies the signal, and at the same time relies on the field emission characteristics of the built-in rectifier to separate the carrier from the information component. Then the counter electrode will detect the change of the field emission current, and transmit the broadcast content such as song or news to the speaker, and the speaker will convert the signal into sound wave.
The principle and structure of the radio
The high-frequency signal received from the antenna is detected (demodulated) and restored to an audio signal, which is sent to the earphone or speaker to become a sound wave.
Due to advances in technology, there are many radio waves of different frequencies in the sky. If all these many radio waves are received, the audio signal will be like being in a busy city. Many sounds are mixed together, and as a result, nothing can be heard. In order to try to select the desired program, there is a selective circuit behind the receiving antenna. Its function is to select the required signal (station) and "filter out" the unwanted signal to avoid interference. This is When we listen to the radio, we use the "Select Channel" button. The output of the selective circuit is to select the high-frequency AM signal of a certain radio station. It is impossible to use it to directly push the earphone (electro-acoustic). It must be restored to the original audio signal. This restoration circuit is called demodulation. , Send the demodulated audio signal to the earphone, you can receive the broadcast.
The simplest radio is called direct detector, but the high-frequency radio signal obtained from the receiving antenna is generally very weak. It is not suitable to send it directly to the detector. It is best Insert a high-frequency amplifier between the selection circuit and the detector to amplify the high-frequency signal. Even if a high-frequency amplifier has been added, the output power of the detector is usually only a few milliwatts, which is fine for listening with headphones, but it is too small to use a speaker. Therefore, an audio amplifier is added to drive the speaker after the detector output. High-amplification radios have higher sensitivity and higher power than direct-detection radios, but the selectivity is still poorer and the tuning is more complicated. Amplify the high-frequency signal received from the antenna by hundreds or even tens of thousands of times. Generally, several stages of high-frequency amplification are required. Each stage of the circuit has a resonant circuit. When the received frequency is
When changing, the resonant circuit must be re-adjusted, and the selectivity and passband after each adjustment are difficult to guarantee exactly the same. In order to overcome these shortcomings, almost all radios now use superheterodyne circuits. The characteristic of superheterodyne is that the carrier frequency of the selected high-frequency signal becomes a lower fixed intermediate frequency (465KHz), which is then amplified by an intermediate frequency amplifier to meet the requirements of detection, and then detection is performed. In a superheterodyne receiver, in order to produce a frequency conversion effect, an additional sinusoidal signal is required. This signal is usually called a heterodyne signal. The circuit that generates a heterodyne signal is customarily called a local oscillation. The frequency of the radio local oscillator and the frequency of the received signal are different by an intermediate frequency, so the selection circuit before the mixer and the local oscillator use a unified tuning line, such as using a coaxial double capacitor (PVC) for tuning to make the difference Keep a fixed IF value. Because the intermediate frequency is fixed and the frequency is lower than that of the high-frequency modulated signal, the gain of the intermediate amplifier can be made larger, the work is relatively stable, and the passband characteristics can also be made ideal, so that the detector can obtain a large enough signal. So that the whole machine outputs audio signals with better sound quality.
The commonly used radios are superheterodyne radios, mainly including AM radios, FM radios and FM stereo radios.
The broadcasting station broadcasts a program by first converting the sound into an audio electrical signal through a microphone, and then being amplified by a high-frequency signal (carrier). At this time, a certain parameter of the high-frequency carrier signal follows the audio signal. Make corresponding changes so that the audio signal we want to transmit is contained in the high-frequency carrier signal. The high-frequency signal is amplified again, and then when the high-frequency current flows through the antenna, it forms a radio wave that is emitted outwards, and the propagation speed of the radio wave is 3 ×10 to the 8th power of meters per second, this radio wave is received by the radio antenna, then amplified and demodulated, restored to an audio electric signal, sent to the speaker voice coil, causing the corresponding vibration of the paper cone, and then the sound can be restored. , Which is the process of sound-electric conversion and transmission-electro-acoustic conversion.
The frequency of medium wave (high-frequency carrier frequency) is specified as 525-1605kHz (thousand cycles).
The frequency range of shortwave is 3500-18000kHz.
Principle of superheterodyne radio
Radio
Block diagram of the working principle of AM superheterodyne radio. The high-frequency signal received by the antenna is connected to the radio through the input circuit The oscillation frequency of this machine (the frequency is higher than the external high-frequency signal by a fixed intermediate frequency, and the Chinese intermediate frequency standard stipulates 465KHZ) is sent into the frequency conversion tube and mixed together-frequency conversion, and a new frequency is generated in the load circuit (frequency selection) of the frequency conversion stage and then passed The intermediate frequency generated by the difference frequency, the intermediate frequency only changes the frequency of the carrier, the original audio envelope does not change, the intermediate frequency signal can be better amplified, the intermediate frequency signal is detected and the high frequency signal is filtered out. After low-amplification and power amplification, the speaker is pushed to produce sound.
A brief description of the working principle of this machine. The circuit diagram forms the antenna input loop. VT1, B2, B1, and C form the frequency conversion stage. VT1 is a frequency conversion tube. The primary coil and C form a variable frequency load. C1 and B2 form the local oscillator circuit, C6 is the oscillation coupling circuit, VT2 and VT3 form the intermediate frequency amplifier circuit, 2AP9 is the detection circuit, R9 is the volume potentiometer (with power switch), and C16 is the high-frequency coupling capacitor.
VT4 and VT5 are pre-low frequency amplifier stages, and VT6 and VT7 form a Class B push-pull power amplifier. R16, C21, and C17 are power wave circuits. R1, R2, R3, R4, R5, R6, R7, R12, R10, R11, R13, R17, R18 are the DC bias resistors of each stage.
Major Events
On January 23, 1923, the Americans founded the China Radio Company in Shanghai to broadcast
radio programs and sell radios at the same time. The United States produced the most , One of its types is mineral radio, and the other is tube radio.
In 1953, China developed the first nationally produced radio ("Red Star" tube radio) and put it on the market.
In 1956, China's first germanium alloy transistor was developed.
In 1958, my country's first domestic semiconductor radio was successfully developed.
In 1965, the output of semiconductor radios exceeded the output of tube radios.
About 1980 was the peak period of the development of the radio market.
In 1982, a radio with integrated circuit radio and silicon germanium tube mixed circuit and audio output OTL circuit appeared.
From 1985 to 1989, with the development of TV sets and tape recorders, sales of transistor radios declined year by year, and tube radios tended to be eliminated. The style of the radio changed from a large desktop to a pocket-sized one.
Radio History
January 23, 1923
The American Osborne and the Chinese Zeng Jun founded the China Radio Corporation through a self-built radio station It broadcasts radio programs in Shanghai for the first time, and sells radios at the same time. There are more than 500 radios in the city to receive the radio program, which is the first batch of radios to appear in the Shanghai area. Later, with the continuous establishment of radio stations, radios gradually emerged in the Shanghai area. They are all imported products, with the most produced in the United States. One type is mineral radios and the other is tube radios. The citizens prefer to use mineral radios.
August 1924
The Ministry of Transportation of the Beiyang Government announced the provisional regulations for the installation of broadcast radio receivers, allowing citizens to install radios. Among the citizens, those who install radios are gradually rising, and their methods are mostly regenerative line connections. In August of the same year, Yan Jingyan of the Shanghai Jiande Savings Association successfully installed the radio using the superheterodyne line connection method. In October of the following year, Asian American Radio Co., Ltd. successfully tested and assembled the mineral radio and tube radio in the Songjiang Library. It not only received radio waves from Shanghai Radio, but also received music programs broadcast by Japanese radio.
October 1933
America Radio Co., Ltd. produced No. 1001 crystal radio, which is small and beautiful in appearance, low in price, and good in radio. It is welcomed by the public. In October 1935, the company produced the first 1651 superheterodyne five-lamp radio. In addition to electron tubes and carbon resistors, the high-cycle and mid-cycle transformers, power transformers and coils used in this machine are all designed and manufactured by ourselves. Since then, a number of radio manufacturers have produced radios one after another. Among them, Zhongyong Radio Equipment Factory has a larger scale, second only to Asian American Radio Co., Ltd. In 1936, it produced standard three-circuit one-lamp radios and DC three-lamp radios. In addition, there are Huachang Radio Equipment Factory and Yaer Electrical Co., Ltd., which have produced radios with one to five lamps. Although the production methods are relatively backward and the number of products is small, these products occupy a certain position in the domestic radio manufacturing industry.
In 1936
With the development of the radio station business, radios were gradually popularized throughout the city, with a total of about 100,000 or more, but almost all of them were foreign products, making domestic national radio manufacturing The industry is developing slowly. In July 1937, when the Anti-Japanese War broke out, Shanghai's radio manufacturing industry was further hit. In 1942, the Japanese invaders banned citizens from using radios with more than seven lights, and forced citizens to remove the short-wave coils of the radios. Under the rule of the Japanese and puppets, the production of radio manufacturers was at a standstill.
In 1945
After the victory of the War of Resistance Against Japan, Shanghai's national radio manufacturing industry was restored, and a number of new radio manufacturers were also developed. At the end of 1947, there were 590 companies in Shanghai's electrical industry and commerce, of which 235 were in the radio industry and commerce. In the same year, the National Government Resources Committee established a research institute in Shanghai, which produced a high-end radio station of the resource brand desktop and floor-standing eight lamps. However, bureaucratic capital enterprises imported large quantities of radio parts from abroad and sold assembled radios at low prices, which brought new blows to the national radio manufacturing industry. On the eve of the liberation of Shanghai, more than 30% of the factories in Shanghai Telecommunications Industry were in shutdown or semi-stop status, and only 7 factories and workshops engaged in the manufacture of radios and parts were left with a total of 113 employees.
By the way, Yamei and Zhongyong were the leaders of the radio industry in Shanghai and even the whole country, and Yar’s light bulbs were absolutely famous brands at the time.
The history of the development of world radios
Mineral radios
Today, we are accustomed to refer to those radios that do not use a power source and have only one semiconductor component in the circuit are collectively referred to as "stone radios". ". Mineral radio refers to a passive radio without amplifying circuit composed of antenna, ground wire, basic tuning circuit and ore as a detector. It is the simplest radio receiving device and is mainly used for the reception of medium wave public radio broadcasts. In 1910, American scientists Dunwoody and Picard used ore as a detector, hence the name.
Because the mineral radio does not require a power source and has a simple structure, it is very popular among radio enthusiasts. There are still many enthusiasts who like to DIY and research by themselves. However, it can only be listened to by one person, and the reception performance is relatively poor, which objectively restricted the popularization and development of radio broadcasting at that time.
On January 23, 1923, the Americans founded the China Radio Company in Shanghai to broadcast radio programs and sell radios. The United States produced the most. The first type is mineral radio and the other is tube radio.
Tube Radio
In 1904, the world's first electronic tube was born under the hands of British physicist Fleming. The birth of the first electronic tube of mankind marked the beginning of the electronic age of the world.
The electron tube is an electronic device that generates current conduction in an airtight closed container (usually a glass tube), and uses the effect of an electric field on the electron flow in the vacuum to obtain signal amplification or oscillation. The electronic tube is the originator of the electronic age. After the invention of the electronic tube, the circuit and receiving performance of the radio have been revolutionized and improved.
Before 1930, almost all tube radios were powered by two sets of DC power supplies, one set for filament power supply, and one set for anode power supply, and the power consumption was relatively large, so it would not take a long time. Replace the battery, so the use cost of the radio is higher. Around 1930, radios using AC power were successfully developed, and tube radios entered people's homes on a large scale. However, due to the large size, high power consumption, high heat generation, short lifespan, low power utilization efficiency, fragile structure, and the need for high-voltage power supply shortcomings, most of its uses have been basically replaced by solid-state device transistors.
Transistor radio
Transistor is a solid semiconductor device that can be used for detection, rectification, amplification, switching, voltage stabilization, signal modulation and many other functions (gold, silver, copper, iron, etc.) Metals have good electrical conductivity and are called conductors. Wood, glass, ceramics, mica, etc. are not easy to conduct electricity and are called insulators. Substances with conductivity between conductors and insulators are called semiconductors. Transistors are made of semiconductor materials. The most common types of materials are germanium and silicon). On December 23, 1947, the first transistor was born at Bell Labs in the United States. This was a major invention in the 20th century and a precursor to the microelectronics revolution. Since then, mankind has entered a rapidly developing electronic age.
Transistor radio is a small transistor-based radio receiver. On October 18, 1954, the world's first transistor radio was put on the market, containing only 4 germanium transistors. After the advent of transistors, radios began to really become popular. my country also began to develop transistor radios in the late 1950s, and a production climax was formed in the 1970s. Old radios of famous brands such as Gent, Japan, Sony, Philip of the Netherlands, and domestically produced red lights, peony, panda and other famous brands are evidence of this history. In 1958, my country's first domestic semiconductor radio was successfully developed.
Transistor radios have won the people’s love for their low power consumption, no AC power supply, compact size, and convenient use. They have gradually taken a leading position in the market and become the most popular and cheap electronic products.
The transistor is one of the greatest inventions in modern history. After the invention of the transistor, electronics has made rapid progress. Especially the emergence of PN junction transistors opened up a new era of electronic devices and caused a revolution in electronic technology.
Integrated Circuit Radio
On September 12, 1958, Kilby developed the world's first integrated circuit. Since then, integrated circuits have gradually replaced transistors, making the emergence of microprocessors possible, laying the foundation of modern microelectronics technology, and laying the foundation for modern information technology, creating a new era in the history of electronic technology, making us accustomed to everything now. The emergence of electronic products becomes possible.
On an extremely tiny semiconductor chip of a few square millimeters, thousands of transistors, resistors, capacitors, including connecting wires are made together, and used as a device with a certain circuit function. The components are called "integrated circuits". Integrated circuits have the advantages of small size, light weight, few lead wires and soldering points, long life, high reliability, and good performance. At the same time, they have low cost and are convenient for mass production. Essentially, integrated circuits are the most advanced transistors. Integrated circuits have made electronic components a big step towards miniaturization, low power consumption and high reliability. The use of integrated circuits to assemble electronic equipment can increase the assembly density by tens to thousands of times compared with transistors, and the stable working time of the equipment can also be greatly improved.
In 1982, integrated circuit radios appeared in our country.
DSP radio
DSP technology radio means that the radio analog signal is received by the antenna, amplified in the same chip, and then converted into a digital signal, and then the digital signal is processed, and then Restored to a new type of radio with analog audio signal output. The essence of DSP technology is to use "software radio" instead of "hardware radio", which greatly reduces the threshold of radio manufacturing.
In 2006, Silicon Labs first developed a DSP technology radio chip. In the same year, the world’s largest radio manufacturer: Shenzhen Kailong Electronics Co., Ltd. cooperated with Silicon Labs to develop the world’s The first DSP radio: KK-D48L. In 2007, Shenzhen Kailong Electronics Co., Ltd. established DSP technology research and development laboratories in Shenzhen and Shanghai. In 2009, the middle and low-end performance DSP radio chip with independent intellectual property rights was born. Since then, the DSP technology radio has entered the era of popularization. Shenzhen Kailong Electronics Co., Ltd. also won the national high-tech enterprise award.
The advent of DSP technology radios indicates that traditional analog radios will gradually withdraw from the stage of history. The digital age of radio has arrived.