How radio waves work

Electronic devices transmit information via radio waves, optical fiber and infrared rays. Among them, radio waves are used for 5G communication. This page explains how radio waves are used to transmit information.

Radio waves

Radio waves are waves of electrical energy that travel through space. As you know, you can't see them with your eyes or feel them on your skin.

Radio waves have similar properties to sound. For example, just as sound comes out of speakers, radio waves have a source, and the further away you are from them, the weaker they become. They can also go through and bounce off objects.

The speed at which radio waves travel is incomparable to that of sound. Radio waves travel at the same speed as light, about 300,000 km/s. (Sound is about 0.3 km/s)

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Just like there are high pitches and low pitches, radio waves also have high and low, too. This is called "Frequency" and it is expressed in Hz (Hertz), which is the number of waves in a radio wave per second. Frequency is not limited to radio waves, but is also used to represent the "number of waves" in sound waves, and many other areas.

For example, if there are 3 waves per second, it is described as "3 Hz", and if there are 6 waves per second, it is described as "6 Hz".

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Radio waves have different features depending on the frequency.

When the frequency is low
  • Reaches far and wide
  • Easy to go through obstacles
When the frequency is high
  • Small range
  • Easily absorbed by obstacles

As you can see, radio waves have different characteristics depending on the frequency, so the frequency to be used is set for each usage. In addition, the frequency of radio waves is determined by law depending on the purpose of use. Violation of the law will result in a penalty of up to one year in prison or a fine of up to 500,000 yen.

Remember, frequency is mentioned several times throughout this site.

A system for transmitting information

In mobile communications, all data is represented by 0s and 1s. As we saw on the Previous, the data is 0s and 1s all the way from the data center to your phone. So how do the 0s and 1s get on the radio waves at the base station?

Putting 0 and 1 data over the airwaves is called "Modulation" .There are various modulation methods, but this section explains the modulation method called PSK, which is widely used in mobile communications and other applications.

In the PSK system, radio waves are transmitted by assigning 0s and 1s to each pattern of radio wave shape. When a mobile phone receives a radio wave, it reads the 0s and 1s one after the other, depending on the waveform of the radio wave, and receives the data.

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This diagram was created by a member.

In actual communication, more information is assigned to more patterns of waveforms than this to achieve higher communication speeds. However, the basic method of this modulation remains the same for both 4G and 5G.