What is radio and what is radio

The simplest analogy:

The electricity we use for daily lighting is connected from generators and transformers with wires, and it is wired electricity.

The electrical signal received by the mobile phone is not connected to the machine that generates the signal with a wire, which is a radio.

Electromagnetic waves below infrared rays are called radio waves, or radio for short. In addition, there is a small superposition of infrared rays at the low end and radios at the high end of the high end.

Radio refers to electromagnetic waves that propagate in all free spaces (including air and vacuum), and is one of the finite frequency bands, with the upper frequency at 3thz (terahertz) and the lower frequency at less uniform, in various RF specification books, the common ones are 3kHz 3thz (ITU International Telecommunication Union regulations), 9kHz 3thz, 10kHz 3thz [1].

The inventor of radio is also disputed, with another theory suggesting that Nikola Tesla was the inventor of radio. In the summer of 1893, Tesla elaborated on six basic requirements for radio transmission and reception in his speech. In 1897, Tesla filed a patent on radio, the specifics of which patents are not very clear, which are used for wireless power transmission and which are used for signal communication, at a glance.

Prologue to the dissemination of wireless telegraphy through periodicals. In the early days, wireless telegraphy technology was mainly disseminated in comprehensive journals, mostly articles introducing new things, and then there were scientific and technological articles that introduced the principles, including articles on the latest technologies and inventions. With the development of wireless telegraphy technology, the content disseminated in periodicals also changed, and many legal articles appeared.

Judging from the articles disseminated in journals in the late Qing Dynasty, they have become self-contained, which has laid a theoretical foundation for the emergence of professional journals and the formation of discipline institutions in the future[3].

Principles of radio technology.

Radio refers to electromagnetic waves that propagate in free space, including air and vacuum, while radio technology is the technology that transmits signals through radio waves. The principle of radio technology is based on the theory of electromagnetic waves, that is, the change in the intensity of the current in a conductor produces radio waves. Using this phenomenon, information can be loaded on top of radio waves by modulation.

When the radio wave travels through space to the receiver, the change in the electromagnetic field caused by the radio wave will generate an electric current in the conductor. The purpose of information transmission is achieved by extracting information from current changes through demodulation [5].

Radio frequency.

Radio waves contain a magnetic field that vibrates rapidly. The speed of the vibration is the frequency of the wave, measured in hertz (Hz). 1 hertz is equal to one vibration per second.

One kilohertz (khz) is equal to 1000 hertz. Bands of different frequencies are used to transmit a variety of different information [6].

Radio frequency bands.

Radio is divided into following according to wavelength and frequency:

Long wave: wavelength "1000 meters, frequency below 300kHz;

Medium wave: wavelength 100 meters 1000 meters, frequency 300kHz 3000kHz;

Short wave: wavelength 100 m 10 m, frequency 3MHz 30mhz;

Ultrashort wave: wavelength 1 meter 10 meters, frequency 30MHz 300MHz, also known as very high frequency (VHF) wave, meter wave;

Microwave: wavelength 1 m mm, frequency 300MHz 3thz [6].

Radio principle: Radio technology is through radio waves.

The technology of propagating signals. The principle of radio technology is that a change in the intensity of the current in a conductor produces radio waves.

When an electric wave travels through space to the receiving end, the electromagnetic field caused by the radio wave.

The change, in turn, creates an electric current in the conductor. The purpose of information transmission is achieved by extracting the information from the current change through demodulation.

Radio refers to electromagnetic waves that propagate in all free spaces, including air and vacuum.

It is a limited frequency band in which the lead envy, the upper frequency is at 3thz (terahertz, the lower limit frequency is less uniform, in various radio frequency specification books, the common is 3kHz 3thz (ITU International Telecommunication Union.

stipulated), 9khz 3thz, 10khz 3thz.

The main uses of radio:

1. Communication. Wireless communication occupies an extremely important position in modern communication, and wireless communication is used in almost any field, including commercial, meteorological, financial, military, industrial, civil, etc. We can see that there are many types of wireless communication systems in terms of communication systems, modulation methods, multiple access methods, etc.

2. Navigation. All satellite navigation systems use satellites equipped with precise clocks. Navigation satellites broadcast their position and timing information.

The receiver receives signals from multiple navigation satellites at the same time. The receiver calculates the distance from each satellite by measuring the propagation time of the radio wave, and then calculates its precise position.

3. Radar. Radar calculates the distance to a target by measuring the delay of reflected radio waves. and sensing the type of surface of the target by the polarization and frequency of the reflected wave. Navigation radars use ultra-short waves.

Scan the target area. The general frequency of scans is two to four times per minute, and the terrain is determined by reflected waves. This technology is commonly used on merchant ships and long-haul commercial aircraft.

4. Increase the amount of excitement and heat.

Microwave oven. High-power microwaves are used to heat food. (Note: A common misconception is that microwave ovens use frequencies for water molecules.)

, when in fact the frequency used is about one-tenth of the resonance frequency of water molecules. ）

5. Power transmission.

Japanese scientists have proposed to build large-scale solar power plants in space to convert electrical energy into microwaves and send them back to Earth.

The principle is to use a non-radiative wireless energy transfer method to drive electrical appliances

There is a very typical metaphor that describes this process: when you throw a stone like the surface of a calm lake, the waves of water travel far away.

If these waves can record information, then as the ripples disperse, the information can travel far away. Radio wave.

It can propagate in free space (e.g. air and vacuum), so as long as a human can load the information on a specific frequency of radio waves, then the purpose of transmitting the information can be achieved.

Specifically, this technology works by generating radio waves when the intensity of the current present in the conductor changes.

Radio waves are generated by changes in the intensity of the current in the conductor, and the information can be loaded on the radio waves by modulation. When an electric wave propagating through space reaches the receiver, the electromagnetic field caused by the radio wave at this time.

The change in turn generates an electric current in the conductor, and the information is extracted from the current change through demodulation to achieve information transmission.

Applications of radio

The earliest application of radio was in the field of communications, where people could use radio to transmit information over long distances for the first time.

In the past, in the vast sea, it was difficult to transmit information between ships, but when radio technology came out, it was quickly applied to the field of navigation, and it was used to issue and receive instructions and report situations; Civilian ships will also use it to call for help or to deliver their Senchangta messages.

Mobile** is the most widely used wireless communication device in the current state, as long as the signal coverage area, people can talk freely. In addition, wireless LAN.

Technologies such as Bluetooth use radio technology to transmit data over short distances.