E band (waveguide)

Lore & Background

At these high frequencies, the short wavelengths give the radiation a very directional quality, similar to visible light. Many molecules possess rotational and vibrational states excited by very specific wavelengths in this band, thus atmospheric gases such as oxygen, water vapor, carbon dioxide and nitrogen can absorb and be excited, causing variable beam attenuation effects dependent on meteorological and atmospheric conditions.

In October 2003, the Federal Communications Commission (FCC) ruled that spectrum at 71 to 76 GHz, 81 to 86 GHz and 92 to 95 GHz was available for high-density fixed wireless services in the United States. The Radio Regulations of the International Telecommunication Union allow amateur radio and amateur satellite operations in the frequency range 76.000 GHz to 81.000 GHz, known as the 4-millimeter band.

In June 2020, SpaceX applied for use of the E-Band in the Starlink Gen2 constellation. Generation 2 Starlink Gen2 satellites will include 71–79 GHz and 81–86 GHz operational frequencies. This was approved by the Federal Communications Commission (FCC) on March 8, 2024.

Reader's Guide

The E band's significance lies in its allocation for high-density fixed wireless services, enabling point-to-point and point-to-multipoint communication links with high data capacity. The directional nature of the radiation, akin to visible light, allows for tightly focused beams that reduce interference and support dense deployment. The FCC's 2003 ruling opened key sub-bands for commercial use, while the ITU's amateur allocation at 76–81 GHz supports experimental and hobbyist operations. The band's legacy is further cemented by its adoption in SpaceX's Starlink Gen2 constellation, approved in 2024, which will use 71–79 GHz and 81–86 GHz to provide broadband connectivity. Atmospheric absorption, particularly by oxygen and water vapor, imposes range limitations but also offers inherent security against long-range interception. The E band thus serves as a critical resource for modern high-capacity wireless networks, bridging the gap between microwave and optical communication techniques.

Did You Know?

• The E band corresponds to the recommended frequency band of operation of WR12 waveguides.
• Atmospheric gases such as oxygen and water vapor can absorb E-band radiation, causing variable beam attenuation.
• The FCC approved SpaceX's use of 71–79 GHz and 81–86 GHz for Starlink Gen2 on March 8, 2024.
• Amateur radio and amateur satellite operations are allowed in the 76.000–81.000 GHz range, known as the 4-millimeter band.

Defining the E Band and Its Physical Properties

The E band represents a specific slice of the electromagnetic spectrum, encompassing radio frequencies that range from 60 gigahertz up to 90 gigahertz. This band sits firmly within the Extremely High Frequency, or EHF, classification of the radio spectrum. From an engineering standpoint, the E band is the designated operating range for WR12 waveguides, the standardized metallic conduits through which these high-frequency signals are transmitted. The wavelengths corresponding to this frequency range measure between 5 millimeters at the low end and roughly 3.333 millimeters at the high end. One of the most notable physical characteristics of E band radiation is its extreme directionality. Because the wavelengths are so short, the beams behave in a manner strikingly similar to visible light, traveling in tight, focused paths rather than spreading broadly. This property makes the band well suited for precise, point-to-point communication links, though it also introduces vulnerabilities to atmospheric absorption that significantly affect signal integrity over distance.

Atmospheric Attenuation and Molecular Interactions

Operating at the upper end of the radio spectrum introduces a significant practical challenge: the atmosphere itself becomes an active participant in signal propagation. At E band frequencies, many common atmospheric molecules possess rotational and vibrational energy states that can be excited by very specific wavelengths within the 60-to-90 GHz window. Oxygen, water vapor, carbon dioxide, and nitrogen all exhibit this behavior, meaning that as an E band beam passes through the atmosphere, these gases can absorb energy from the signal and become excited in the process. The result is variable beam attenuation that is not constant but rather shifts depending on prevailing meteorological and atmospheric conditions. Humidity levels, temperature, and the concentration of various gases all influence how much signal is lost. This makes E band links particularly sensitive to weather, and engineers must account for these fluctuating losses when designing reliable high-frequency communication systems.

Regulatory Framework and Terrestrial Spectrum Allocation

The allocation of E band spectrum for terrestrial use has been shaped by regulatory decisions at both national and international levels. In the United States, the Federal Communications Commission issued a ruling in October 2003 designating specific sub-bands within the E range for high-density fixed wireless services. The frequencies opened up by that decision span 71 to 76 GHz, 81 to 86 GHz, and 92 to 95 GHz, providing operators with substantial blocks for building dense wireless infrastructure. On the international stage, the Radio Regulations maintained by the International Telecommunication Union carve out a different portion of the E band for the amateur radio community. The range from 76.000 GHz to 81.000 GHz is specifically set aside for amateur radio and amateur satellite operations, and within the ham radio community this segment is commonly referred to as the 4-millimeter band, a nod to the approximate wavelength of signals operating in that range.

E Band in the Starlink Satellite Era

The E band has found a powerful new application in satellite-based internet connectivity. In June 2020, SpaceX applied for use of the E band within its Starlink Gen2 constellation. The second-generation Starlink satellites are designed to include operational frequencies in two distinct windows: 71 to 79 GHz and 81 to 86 GHz. After a period of regulatory review, the Federal Communications Commission approved SpaceX's E band usage on March 8, 2024, clearing the path for the company to integrate these high-frequency links into its expanding satellite network. This development marks a notable shift in how the E band is deployed, extending its reach beyond traditional point-to-point terrestrial links into the broader domain of global satellite communications. The approval also highlights the growing importance of EHF spectrum in next-generation broadband infrastructure, as major operators seek to harness the unique directional properties of these short wavelengths for large-scale satellite networks.

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