Frequency Spectrum Ku-Band to D-Band
Ku-band to D-band refers to a range of radio frequencies between roughly 12 and 170 gigahertz, used for satellites, microwave links, and fast mobile connections. The higher the frequency, the more data fits through the connection – and the more sensitive it becomes to rain and obstacles.
Radio transmits data as electromagnetic waves through the air. These waves oscillate at different speeds, and the number of oscillations per second is called frequency. It is measured in hertz, where one gigahertz means one billion oscillations per second. So that nobody interferes with anybody else, the usable range has been divided into named segments, so-called bands. Ku-band to D-band is the chain of these segments between approximately 12 and 170 gigahertz. In between, in ascending order, lie Ka-band, Q-band, V-band, E-band, and W-band.
Why the race keeps moving upward
A radio link can carry more data per second the wider the frequency segment it is allowed to occupy. In the lower part of the radio spectrum, practically everything is already allocated: radio, television, mobile networks, military use, air traffic control. Further up, however, there is still plenty of free space. That’s why technology has been moving step by step into higher bands for years.
The difference is substantial. In the Ku-band, one works with segments a few hundred megahertz wide. In the E-band, several gigahertz are available at once – a multiple of that. This makes microwave links with ten or more gigabits per second possible – speeds otherwise only delivered by fiber-optic cables.
Economically, a great deal depends on this. Satellite operators such as Starlink, Amazon's Project Kuiper, or Eutelsat compete for usage rights to these bands. Data centers for artificial intelligence also require enormous amounts of data between their sites. Where cables cannot be laid fast enough, microwave links in the high bands step in.
What rain does to the connection
The advantage of high frequencies comes at a price. The faster a wave oscillates, the shorter it is. In the D-band, the wavelength is only about two millimeters. Such waves are strongly absorbed by water droplets, leaves, and house walls. Experts speak of rain attenuation.
An example makes this tangible. A Ku-band satellite dish continues to function without problems in light rain. A Ka-band connection can briefly fail during a heavy thunderstorm. In the E- or D-band, a distance of just a few hundred meters is enough, and heavy rain can almost completely wipe out the signal.
That’s why the signal in high bands is bundled into a narrow beam, similar to a flashlight rather than a room lamp. Transmitter and receiver must therefore be aligned very precisely with each other. In addition, modern systems automatically adjust their transmission power and transmission method when the weather worsens. They then become slower, but do not drop out.
From TV satellites to the 6G debate
The Ku-band is the classic. Almost every satellite dish on a rooftop receives television through it. In-flight Wi-Fi also frequently runs over Ku-band. Newer satellite networks use the Ka-band for fast internet in regions without cable access.
E-band and W-band are encountered less visibly, but constantly indirectly. Mobile phone towers are often connected to the network via microwave links in these bands when no fiber optic cable is available. Small rectangular or round antennas on towers are usually exactly such links. In the W-band, many distance radars in cars also operate.
The D-band is currently mainly a research topic. In discussions about the future mobile standard 6G, it regularly comes up as a candidate. A common misconception is that higher frequencies automatically bring better reception. The opposite is true: they bring more speed over short distances, but less range. Practically usable networks therefore always combine several bands.