A system of designating the different microwave and later mmWave bands was developed to quickly identify which area of the spectrum a radar system would use.
The system was adopted for many other applications that utilised the microwave and mmWave bands and accordingly these band names and terminology are widely used.
Terms like X-band, L-band, Ku-band, Ka-band and many others are often used when talking about the different bands used by various systems.
It is worth mentioning that there are several different naming systems for the microwave and millimetre wave bands. There are different bands that have the same letter designation, so it is necessary to be careful when using these radar microwave and millimetre wave band naming schemes.
History & development of the radar band designations
The system of band designations for radar dates back to WW2. As it was intended to restrict the understanding of which bands were used, especially keeping it from the enemy, a system of nomenclature was developed.
This system is often referred to as the old system, but despite this, it is still probably the most widely used classification or designation for the various microwave bands.
Traditional radar microwave band designations
Even thought the traditional radar bands have been in use since WW2, there are still differences between different users.
Some industry sectors tend to have slightly different interpretations, so it is always best to double check if the exact frequencies are of importance - often though they are used as a general indication of the broad frequency band used.
The traditional microwave band designations have been adopted by the IEEE, but even so different sectors tend to use slightly different frequency limits on the bands.
These band designations were traditionally used for radar applications, but they have also been adopted for applications including satellite communications, navigation, aviation and now even 5G mmWave mobile communications and even occasionally other wireless communications applications like wireless LANs.
| Traditional / IEEE Band Designations for Microwave & mmWave Bands
|Band Designation||Frequency Range||Details|
|L||1 - 2 GHz||L designates Long wave, which it is in terms of the radar frequencies|
|S||2 - 4 GHz||Short wave|
|C||4 - 8 GHz||Compromise between S and X bands|
|X||8 - 12 GHz|
|Ku||12 - 18 GHz||Sometimes known as J band|
|K||18 - 27 GHz|
|Ka||27 - 40 GHz||Sometimes known as Q band|
|U||35 - 50 GHz, others use limits as 40 - 60 GHz GHz|
|V||50 - 75 GHz|
|E or O||60 - 90 GHz|
|W||75 - 110 GHz|
It will be noticed that there are a number of bands that overlap or letters that are used by different companies and other organisations. This amply demonstrates the wide variety between the different users of these band designations.
Although typically used for radar applications, other users including satellite communications, point to point microwave radio communications, 5G mmWave links and the like may all use these frequencies.
Modern / Eu, NATO & US ECM band designators
Although the old WW2 microwave and mmWave band designations were widely used, it was felt that a more up to date and more encompassing system would be more suitable.
The old designator system was not always as user friendly as many would like and it did not always differentiate between the bands that were used more recently.
Accordingly a new microwave and mmWave band designator system was devices.
| Modern Band Designations for Microwave & mmWave Bands
|Band Designation||Frequency Range|
|A||0 - 250 MHz|
|B||250 - 500 MHz|
|C||500 - 1000 MHz|
|D||1 - 2 GHz|
|E||2 - 3 GHz|
|F||3 - 4 GHz|
|G||4 - 6 GHz|
|H||6 - 8 GHz|
|I||8 - 10 GHz|
|J||10 - 20 GHz|
|K||20 - 40 GHz|
|L||40 - 60 GHz|
|M||60 - 140 GHz|
It will be noticed that there can be a clash between the letter used for the traditional system and the new one. Care needs to be taken to ensure it is understood which system is being used.
Waveguide bands & designations
Often when referring to waveguides, another set of slightly different designations can be used. These have some similarities with the traditional waveguide bands, but they are rather different in other aspects.
This shows why care is needed when using the various band designations.
Waveguides are a form of feeder where the signal is encased in a hollow metal conductor which is typically either rectangular or circular, but this does not include a central conductor as in the case of a coaxial feeder. The most common forms of waveguide tend to be rectangular.
Note on Waveguide:
Waveguide is a form of feeder used at microwave an mmWave frequencies. It consists of an outer conductor that confines and enables the signal to propagate along its length. Waveguides offer low levels of loss, but they are expensive and tend not to be flexible.
Read more about Waveguide.
A summary of the designations often used with waveguides is give below:
| Band designator system sometimes used for waveguides
|Band Designation||Frequency Range (GHz)|
|R||1.70 - 2.60|
|D||2.20 - 3.30|
|S||2.60 - 3.95|
|E||3.30 - 4.90|
|G||3.95 - 5.85|
|F||4.90 - 7.05|
|C||5.85 - 8.20|
|H||7.05 - 10.10|
|X||8.2 - 12.4|
|Ku||12.4 - 18 GHz|
|K||18.0 - 26.5z|
|Ka||26.4 - 40|
|Q||33 - 50|
|U||40 - 60|
|V||50 - 75|
|E||60 - 90|
|W||75 - 110|
The reason that the bands are slightly different to the traditional band designations is that waveguides can operate over a particular bandwidth. Although intended for use in the a particular band designation, they will be tailer to a particular use within that band region. Sometimes the waveguide bandwidth may fall outside the traditional band, other times it may not fully cover either or both ends of the band.
Waveguides tend to be used for larger microwave and mmWave installations as they are quite expensive. They tend not to be used for commercial applications like 5G mmWave, general wireless communications and other applications that are now starting to use these areas of the radio spectrum.
With the latest Wi-Fi and wireless LAN applications now staring to use the microwave portion of the spectrum, lower cost solutions and techniques tend to be used. Accordingly the waveguide designations tend not be used in these situations.
Although the microwave and mmWave band designations are widely used in many areas, care needs to be taken when using them. D band for one system does not correspond to D band for another. So great care must be taken when using them, checking that the frequencies correct for the particular situation: radar, satellite communications 5G mmWave, wireless LANs, etc.
Nevertheless the naming schemes are in widespread use, so it is often helpful to have an understanding of the different schemes and also the pitfalls.
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