RF Spectrum Allocation

Key Takeaways

• The radio spectrum, ranging from 3 Hz to 3,000 GHz, is used extensively in telecommunications. Its usage is strictly regulated to prevent interference.

• The three main regulating bodies for RF spectrum allocation are the International Telecommunication Union (ITU),  the US Institute of Electrical and Electronics Engineers (IEEE), and the EU-NATO-US Electronic Countermeasure.

• The radio spectrum's practical limits are constrained by technological and atmospheric factors, with low frequencies requiring increasingly large antennas and high frequencies being limited by atmospheric absorption.

Visual representation of RF telecommunication tower

The radio spectrum is part of the electromagnetic spectrum, with frequencies from 3 Hz to 3,000 GHz. RF spectrum allocation is regulated by the International Telecommunication Union, the US Institute of Electrical and Electronics Engineers, and the EU-NATO-US Electronic Countermeasure. The radio spectrum's usable range is dictated by technological and atmospheric limitations: lower frequencies require larger antennas, while higher frequencies face atmospheric absorption constraints. As a finite resource under growing demand with RFID technology, the radio spectrum's congestion has inspired innovations in telecommunications to enhance its utilization.

RF Spectrum Allocation by Different Standards 

Different Regulating Bodies for RF Spectrum Allocation 

The International Telecommunication Union (ITU),  the US Institute of Electrical and Electronics Engineers (IEEE), and the EU-NATO-US Electronic Countermeasure divide the RF spectrum into different bands and allocate them for similar services to avoid interference and optimize spectrum use. 

International Telecommunication Union (ITU)

The ITU divides the radio spectrum into 12 main bands and then divides each band into subbands allocated to different services. For each radio band, the ITU has a band plan that dictates how it will be used and shared to avoid interference and to set protocols for the compatibility of transmitters and receivers. 

Components of ITU RF Band Plan

US Institute of Electrical and Electronics Engineers (IEEE)

The IEEE designates the RF spectrum by letters.  The letter designations are consistent with the recommended nomenclature of the International Telecommunications Union (ITU). The main purpose of the radar nomenclature is to subdivide the existing ITU bands in accordance with radar practice.

EU-NATO-US Electronic Countermeasure (EU-NATO-US ECM)

In 2014, the  EU, NATO, and the US signed NATO Joint Civil/Military Frequency Agreement (NJFA) to regulate military access to the radio frequency spectrum in the range of 14 kHz to 100 GHz. In this system, the boundaries of the frequency bands are distributed in a logarithmical fashion and named in alphabetical order. Frequencies higher than 100 GHz, named N and O, are reserved for US Military and Supreme Allied Commander Atlantic (SACLANT) use.

Limits of RF Allocation

The boundary of the RF spectrum is an insurmountable technological limitation. Due to practicality, RF spectrum allocation cannot be expanded to lower or higher frequencies. As a result,  the radio spectrum has become increasingly congested in recent decades, and the need to utilize it more effectively is driving modern telecommunications innovations.

Lower Frequencies Limitations

Radio transmission requires antennas whose size correlates directly with the wavelength and inversely with the frequency. At frequencies below approximately 10 kHz, antenna requirements become impractical, spanning several kilometers in diameter, thus limiting their use in radio systems. Additionally, lower frequencies offer limited bandwidth, restricting data transmission rates. For instance, frequencies under 30 kHz are unsuitable for audio modulation and are limited to slow-speed data communication. 

The lowest frequency utilized, around 80 Hz, is found in Extremely Low Frequency (ELF) communication systems used by some naval forces for underwater submarine communication, utilizing massive ground dipole antennas spanning 20-60 km and powered by megawatts. This frequency transmits data at a very slow pace of roughly 1 bit per minute.

Higher Frequencies Limitations

Atmospheric absorption of microwave energy sets a limit on the highest effective frequencies for radio communication. Beyond 30 GHz, which marks the start of the millimeter wave band, atmospheric gases increasingly absorb radio wave energy, drastically reducing their transmission power over distance. Effective communication at 30 GHz is typically confined to about 1 km, with the reception range diminishing as frequencies rise. Above 300 GHz, in the terahertz band, atmospheric absorption, primarily by ozone, water vapor, and carbon dioxide, is so significant that radio waves are almost completely attenuated within a few meters, making the atmosphere nearly impenetrable to these frequencies.

Applications of Different RF Usage

Different RF bands are reserved for specific applications.

Usage Allocation for the RF Spectrum

Keeping  RF spectrum allocation in mind for RF designs is a critical aspect that must be considered. For your RF designs, consider using Cadence AWR software. This powerful tool empowers designers to navigate the intricacies of designs that utilize the radio spectrum. Utilize Cadence AWR to ensure compliance and foster innovation within the constraints of the radio spectrum, enhancing both antenna design and signal integrity.

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