What is RF?

An electrical signal converted from sound, whose frequency is the same as the frequency of the sound, between tens of Hz and several kHz, called an audio signal; an electrical signal converted from an image, whose frequency is in the range of a few Hz to several megahertz Between, called the video signal. Audio currents and video currents have poor ability to excite electromagnetic waves in space. They need to be loaded into higher frequency currents to generate electromagnetic waves that are emitted into the sky. This current is called RF current. - [1] "Physics", ninth grade, all volumes, P157.

After reading this paragraph, I understand that it is a frequency called the RF, which is the frequency used to transmit the signal!

Radio Frequency (RF) is an abbreviation of Radio Frequency. It is an electromagnetic wave as a carrier. The higher the frequency, the more information can be transmitted in the same time. Is that the higher the frequency, the better? Let's start with the conclusion, no!

Here we understand that from a few hundred kilohertz to 769 terahertz, it is the range of radio frequency. Why is 769 terahertz? Come, let's review, the shortest wavelength of visible light is violet, taking the shortest wavelength of violet light.

You ask me why not ultraviolet light? Well, this is a problem, you have to talk slowly.

In the radio frequency, we have five major frequencies. The first band is called radio wave, the wavelength is about 1000m to 1m, and the frequency is hundreds of kilohertz to hundreds of megahertz. It is a radio frequency for broadcasting, television and mobile phones. The second is called microwave, the wavelength is about 10m to 1mm, the frequency is about 30MHz to 300GHz; the third one is terahertz wave, the wavelength is about 3mm to 3μm, the frequency is 100GHz to 100THz; the fourth paragraph is infrared The wave has a wavelength of about 1 mm to 760 nm and a frequency of about 300 GHz to 400 THz. The fifth segment is visible light having a wavelength of about 700 nm to 380 nm and a frequency of about 380 THz to 770 THz.

There is a big overlap between the microwave and the terahertz wave. It doesn't matter. We have not used the frequency above 100 GHz extensively. In the terahertz band, the attenuation of electromagnetic waves in the air is very powerful. The attenuation of infrared and visible light is even worse. The paper is attenuated, not to mention the wall. It can only be used for indoor short-range communication. . Ultraviolet light has the highest frequency and can only be used at close range. You are not afraid of being sunburned, and are you not afraid of being exposed to skin cancer?

When we are doing circuit design, we are aiming at a very narrow frequency range design. For example, the RF chip used for 4G communication only needs to work at a center frequency of about 2.4 GHz and has a certain bandwidth. Most circuit designers don't care or care about what is RF, they only need frequency, bandwidth and other metrics. But understanding this concept allows us to understand the nature of a hardware system and guide our design.

Now, do you understand RF?