What do microwave band letters like X, Ku and Ka mean?
IEEE Std 521 defines letter designations for radar-frequency bands: HF 3–30 MHz, VHF 30–300 MHz, UHF 300–1000 MHz, L 1–2 GHz, S 2–4 GHz, C 4–8 GHz, X 8–12 GHz, Ku 12–18 GHz, K 18–27 GHz, Ka 27–40 GHz, V 40–75 GHz, W 75–110 GHz, and mm 110–300 GHz.[1]
What uses each band?
| Band | Range | Typical uses |
|---|---|---|
| L | 1–2 GHz | GNSS, air-traffic surveillance, mobile satellite |
| S | 2–4 GHz | Weather and naval radar, Wi-Fi 2.4 GHz, 5G n78 region |
| C | 4–8 GHz | Satellite TV (older), weather radar, Wi-Fi 5/6 GHz |
| X | 8–12 GHz | Marine and military radar, space communications |
| Ku | 12–18 GHz | Satellite broadcasting and broadband |
| K | 18–27 GHz | Water-vapor absorption region near 22 GHz; 24 GHz sensors |
| Ka | 27–40 GHz | High-throughput satellites, 5G FR2 |
| V | 40–75 GHz | 60 GHz unlicensed, inter-satellite links |
| W | 75–110 GHz | Automotive radar (76–81 GHz), imaging |
Why do K, Ku and Ka have those names?
“Ku” is commonly explained as “K-under” and “Ka” as “K-above”, the sub-bands below and above K, which was split around the 22 GHz water-vapor line.
Are there other letter schemes?
Yes. The NATO/EU ECM band scheme (A through M) uses different letters and ranges, and some industries use their own. Always state frequencies numerically in specifications.[1]
Frequently asked questions
What frequency is X band?
8–12 GHz per IEEE Std 521.
What band is 77 GHz radar?
W band (75–110 GHz).
Is Ka band used for 5G?
Parts of 5G FR2 (e.g., 26–40 GHz) lie in the Ka range.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “IEEE Standard Letter Designations for Radar-Frequency Bands (IEEE Std 521)”. IEEE. 2019 revision.