An article to understand the naming of electromagnetic wave bands

We, the engineers working in communications, deal with electromagnetic waves every day, and often see names such as C-band, L-band, Ku-band, and Ka-band.

Have you ever wondered where these band names come from?

In other words, C-band, L-band, Ku-band, Ka-band , etc., all belong to what we often call microwave bands. Microwaves are part of the entire electromagnetic wave.

The earliest record of naming the microwave band can be traced back to World War II.

As we all know, after the Germans occupied the European continent, they wanted to use air blitzkrieg to force Britain to surrender. In order to counter the German air raids, Britain built a large number of radar stations.

British radar during World War II

Radar is the transliteration of the English word Radar, which is derived from the abbreviation of radio detection and ranging, meaning "radio detection and ranging".

The earliest radar used for search purposes had an electromagnetic wave wavelength of 23cm (later changed to 22cm), which the British defined as the L band. L is the first letter of the English word "Long". The L band is also known as the long wave band.

Later, engineers developed a radar with a wavelength of 10 cm, which was defined as the S band. S stands for "short". Yes, the S band is short wave, which is "shorter" than the long wave.

Later, 3cm wavelength radar appeared. This radar is specially used for fire control aiming, so it is called X-band. X comes from the "crosshair" of the sight, and also represents a certain point on the coordinates.

S-band and X-band radars are widely used on warships. S-band radars are generally used as medium-range warning radars and tracking radars. X-band radars are generally used as short-range fire control radars.

Radar system on the US Iowa-class warship during World War II

SG Radar, which works in the S band

In order to combine the characteristics of X-band and S-band radars, researchers developed a radar with a wavelength of 5 cm, which is called C-band. C is the first letter of the word Compromise, which means "combine".

Seeing how powerful the British radar was, the Germans also began to independently develop their own radar.

They chose 1.5 cm as the central wavelength of their radar. This wavelength of electromagnetic waves is called the K band (K = Kurtz, which means "short" in German).

Unfortunately, the Germans discovered that K-band electromagnetic waves are easily absorbed by water vapor, so they cannot be used in rainy or foggy weather.

To avoid this problem, the Germans began to use electromagnetic waves longer or shorter than the K band as radar working waves.

The wavelength slightly longer than the K-band is called the Ku-band (Ku is the abbreviation of K-under in English, meaning below the K-band). The wavelength slightly shorter than the K-band is called the Ka-band (Ka is the abbreviation of K-above in English, meaning above the K-band).

I almost forgot that the earliest radars also made extensive use of meter waves, which was called the P band (P is the abbreviation of Previous, the first letter of the English word "previous").

Later, these band names derived from radar were further extended to satellite, microwave, radio and television and other communication fields, becoming the common names in the industry .

Based on these band names, IEEE (Institute of Electrical and Electronics Engineers) has standardized them as follows:

A more complete version of the microwave band specification:

Because this naming method mixes multiple systems, it is very cumbersome and confusing, so European and American countries represented by NATO have redesigned a new naming system in alphabetical order to replace it.

The correspondence between the new system and the old system is as follows:

The following figure can make it clearer:

Please turn your phone to watch

Image from Wikipedia

Nowadays, people still have different habits in naming bands, depending on the country and region. Some people prefer the old-fashioned names, while others prefer the new ones. Moreover, there are also differences in the definition of specific numerical ranges.

However, I believe that as time goes by, these names and definitions will gradually become unified.

Well, the above is the origin of the naming of electromagnetic wave bands. Do you all understand it?