RF Band Identifier & Spectrum Lookup

1. The Necessity of Overlapping Spectrum Standards

In modern RF, microwave, and telecommunications engineering, a single operational frequency is frequently designated under three or four different regulatory labels simultaneously. For example, an engineer developing an active electronically scanned array (AESA) radar operating at $10.0\text{ GHz}$ will refer to it as an X-band radar (under IEEE Standard 521), a Super High Frequency (SHF) transmitter (under the International Telecommunication Union's Radio Regulations), and a Band I/J system (under NATO military specifications).

These overlapping nomenclatures are not arbitrary redundancies; each framework was constructed to solve distinct engineering, tactical, or international policy challenges:

• International Telecommunication Union (ITU-R): Provides legally binding, decade-based global treaties that prevent inter-service electromagnetic interference across national borders and space communications.
• IEEE Radar Standard 521: Groups spectrum according to atmospheric propagation physics, rain attenuation curves, and microwave aperture hardware dimensions (such as waveguides, horns, and parabolic dishes).
• NATO / Military Electronic Warfare (EW): Establishes standardized radar jamming, signal intercept, and battlefield reconnaissance communication channels across allied armed forces.
• 3GPP Cellular Specifications: Dictates precise channel rasters (ARFCN/NR-ARFCN), channel bandwidths (5 MHz to 100 MHz in FR1; 50 MHz to 400 MHz in FR2), and duplex separation schemes (FDD, TDD, SDL, SUL).

2. International Telecommunication Union (ITU-R) Decade Framework

Established under Article 2 of the ITU Radio Regulations (RR), the official ITU radio bands divide the electromagnetic spectrum into strictly logarithmic, base-10 decade bands designated by integers ranging from Band 4 (VLF) through Band 12 (THF):

Each ITU band corresponds to a precise power-of-ten spatial dimension:

• Band 7 — HF (High Frequency, 3 to 30 MHz): Decametric waves ($\lambda = 100\text{ m}$ to $10\text{ m}$). Dominated by ionospheric F-layer skywave refraction, enabling intercontinental over-the-horizon transmission.
• Band 8 — VHF (Very High Frequency, 30 to 300 MHz): Metric waves ($\lambda = 10\text{ m}$ to $1\text{ m}$). Line-of-sight propagation, FM commercial broadcast, and air-to-ground voice communications.
• Band 9 — UHF (Ultra High Frequency, 300 to 3000 MHz): Decimetric waves ($\lambda = 1\text{ m}$ to $10\text{ cm}$). The cornerstone of terrestrial cellular telephony (LTE, 5G low-bands), Wi-Fi, and broadcast television.
• Band 10 — SHF (Super High Frequency, 3 to 30 GHz): Centimetric waves ($\lambda = 10\text{ cm}$ to $1\text{ cm}$). Microwave links, satellite downlinks, and precision fire-control radar.
• Band 11 — EHF (Extremely High Frequency, 30 to 300 GHz): Millimetric waves ($\lambda = 10\text{ mm}$ to $1\text{ mm}$). 5G mmWave FR2, automotive radar, and molecular absorption spectroscopy.

3. IEEE Standard 521 Radar Letter Bands: History and Modern Usage

The familiar letter bands used in radar and satellite communications originated in British and American World War II military laboratories. To preserve operational security, arbitrary single-letter designations were assigned to secret radar projects:

• P Band (Previous): VHF radar bands operating below 300 MHz.
• L Band (Long): 1.0 to 2.0 GHz ($15\text{ cm}$ to $30\text{ cm}$ wavelength). Characterized by minimal rain attenuation, ideal for long-range air route surveillance radars (ARSR) and GPS/Galileo navigation constellations.
• S Band (Short): 2.0 to 4.0 GHz ($7.5\text{ cm}$ to $15\text{ cm}$). Medium-range airport surveillance radar (ASR), weather radar (NEXRAD), and 2.4 GHz ISM Wi-Fi.
• C Band (Compromise): 4.0 to 8.0 GHz. A compromise between the generous aperture gain of X-band and the low atmospheric attenuation of S-band. Heavily deployed in satellite transponders (4 GHz downlink / 6 GHz uplink) and 5 GHz Wi-Fi.
• X Band: 8.0 to 12.0 GHz ($2.5\text{ cm}$ to $3.75\text{ cm}$). Originally selected because the crosshairs ('X') of fire-control targeting scopes demanded high angular tracking resolution with compact antenna apertures. Today widely used in marine navigation, synthetic aperture radar (SAR), and defense.
• K Band (Kurz / Short): Centered around 24 GHz (from the German word kurz, meaning short). Post-war measurements revealed severe attenuation at 22.24 GHz caused by the molecular resonance of water vapor ($\text{H}_2\text{O}$), forcing the band to be bifurcated into Ku-band (Kurz-under, 12 to 18 GHz) and Ka-band (Kurz-above, 27 to 40 GHz).

4. 3GPP NR Cellular Operating Bands: FR1 vs. FR2

Under 3GPP specifications (TS 38.101-1 and TS 38.101-2), fifth-generation (5G) New Radio (NR) spectrum is classified into two overarching physical Frequency Ranges:

• Frequency Range 1 (FR1 — Sub-7.125 GHz): Originally labeled "Sub-6 GHz", Release 16 expanded FR1 from $410\text{ MHz}$ up to $7125\text{ MHz}$ to encompass the 6 GHz unlicensed Wi-Fi 6E/7 and cellular band (n96). FR1 forms the coverage backbone of global 5G networks, featuring Time-Division Duplexing (TDD) bands such as n77 (3.3 – 4.2 GHz), n78 (3.3 – 3.8 GHz), and n79 (4.4 – 5.0 GHz).
• Frequency Range 2 (FR2 — 24.25 GHz to 71.0 GHz): Millimeter-wave spectrum offering multi-gigabit throughput via wide aggregated channels (100 MHz to 400 MHz). Key allocations include n257 (26.5 – 29.5 GHz), n258 (24.25 – 27.5 GHz), n260 (37.0 – 40.0 GHz), and n261 (27.5 – 28.35 GHz). FR2 systems rely heavily on massive MIMO beamforming to overcome atmospheric absorption and diffraction shadowing.

5. Unlicensed ISM Bands under ITU-R RR 5.150

Under ITU-R Radio Regulations Footnote 5.150, certain spectrum segments are globally designated for Industrial, Scientific, and Medical (ISM) applications. Radiators in these bands—including domestic microwave ovens, industrial RF welders, and medical diathermy machines—are permitted to operate without individual user licensing, but telecommunication devices (such as IEEE 802.11 Wi-Fi, Bluetooth, and Zigbee) must accept any interference caused by ISM equipment. Prominent allocations include:

• 13.553 – 13.567 MHz (Center: 13.56 MHz): Near Field Communication (NFC), ISO 14443 / ISO 15693 smart cards.
• 433.05 – 434.79 MHz (Center: 433.92 MHz): European Short Range Device (SRD) telemetry and remote keyless entry (RKE).
• 902 – 928 MHz (Center: 915 MHz): US FCC Part 15 ISM band, LoRaWAN, smart utility metering.
• 2400 – 2500 MHz (Center: 2450 MHz): 2.4 GHz Wi-Fi, Bluetooth, Zigbee, microwave ovens.
• 5725 – 5875 MHz (Center: 5800 MHz): 5.8 GHz UNII-3 Wi-Fi, wireless video transmission.
• 24.00 – 24.25 GHz (Center: 24.125 GHz): K-Band automotive collision sensors, speed radar guns.
• 61.0 – 61.5 GHz: V-Band short-range sensor systems and gesture detection (e.g., radar micro-Doppler).