Radio Band Ka Frequency

Ka-band: 27-40 GHz high-throughput satellite

The Ka-band runs from 27-40 GHz, which puts the wavelength (λ = c / f) at roughly 7.5-11 mm. It sits at the top of the satellite bands in regular use, and it is what makes today's High-Throughput Satellites (HTS) possible. Those reach terabit-per-second capacities by reusing the same spectrum across dozens of narrow spot beams.

Shorter wavelengths buy you narrower beams and smaller antennas at the same gain. The downside is rain, and it bites hard here. A strong thunderstorm can tack on around 10 dB of fade, well past anything Ku-band has to deal with. Operators push back with adaptive coding and modulation plus uplink power control.

Applications

Inmarsat Global Xpress, ViaSat-3, Hughes Jupiter and the SpaceX Starlink V2 downlinks all run on Ka-band. Down on the ground, 5G FR2 (eMBB millimeter wave, 24-40 GHz) overlaps the lower stretch of Ka and hands cells multi-gigabit capacity over short distances. Defense systems like WGS and Syracuse lean on Ka too, as do NASA's deep-space links, mostly for the bandwidth it opens up.

FAQ

Why move to Ka if rain attenuates more? There is a lot more room up there, and far less competition for it. You can run carriers wider than 1 GHz and pack in dense spot-beam reuse, and that adds up to much higher total throughput per satellite.

How is rain fade mitigated? When the fade hits, Adaptive Coding and Modulation (ACM) steps down to a sturdier MODCOD, giving up bitrate to keep the link alive. Spot beams help as well, since they aim power right where it is needed.

Is 5G mmWave the same as Ka satellite? They share some frequencies, but they are not the same thing. 5G FR2 runs on terrestrial cells that reach only a short distance, whereas Ka satellites blanket whole regions with spot beams sent down from orbit.