Updated May 24, 2019
Defense Primer: Military Use of the Electromagnetic Spectrum
Since the introduction of the two-way radio in the early
and destroy drones. The majority of military
1900s, militaries have been interested in the
communications capabilities use radio waves, microwaves,
electromagnetic spectrum (“the spectrum”). The
and infrared frequencies. Nearly every modern weapons
proliferation of spectrum-dependent systems in all military
system—airplanes, satellites, tanks, ships, and radios—
domains—air, land, sea, space, and cyberspace—along with
depends on the spectrum to function. These applications
Department of Defense (DOD) concepts, such as net-centric
can be combined to provide an overall military capability,
warfare and multidomain battle, increases the military’s
such as command and control or electronic warfare. The
dependence on the spectrum.
following discussion provides a few examples of spectrum
applications.
What Is the Spectrum?
The electromagnetic spectrum is a series of frequencies
Communications
ranging from radio waves to microwaves, visible light, X-
Military commanders have become accustomed to
rays, and gamma rays. As the wavelength of the
communicating with their forces near-instantaneously.
electromagnetic radiation shortens, the waves have a higher
Communication includes a range of options from low
frequency—how quickly electromagnetic waves follow
bandwidth options, such as transferring small strings of
each other—and therefore more energy.
text, to high data-intensive applications, such as full motion
video and video teleconferencing. Radio frequencies are the
Figure 1. The Electromagnetic Spectrum
primary mechanism to transmit this data. These systems can
be located terrestrially (either with ground forces or on
ships), in the air, or in space (i.e., on satellites). In general,
communications systems use radio and microwave
frequencies; however, emerging communications
technologies use lasers—transmitting light, instead of radio
waves, between antennas.
Radios use different frequencies depending on the range
and amount of data they are required to transmit. Ground-
Source: https://imagine.gsfc.nasa.gov/science/toolbox/
based radios are typically used at short ranges, limited by
emspectrum1.html.
the line of sight. These short ranges span no more than 50
Different parts of the spectrum serve different military
miles. In general, militaries use satellites to communicate
purposes. Radio transmissions have relatively low data
over longer distances.
rates—particularly in the very low frequency range.
However, they are able to travel long distances and pass
Situational Awareness
through solid objects like buildings and trees, and are often
Another application of the spectrum is using radio or
used for communications equipment. Microwaves have
microwave frequencies to develop a picture of the battle
higher throughput—data upload and download rates—than
space by providing the location of friendly and enemy
radio waves and therefore are able to transmit more data,
forces. The most common application is radar, however
but are more limited in range and can be disrupted by solid
recently light detection and ranging (LIDAR) systems are
objects. Hence, microwaves are often used for radars and
also used. Both technologies send out a signal that is then
satellite communications. Infrared waves, which emit
reflected back to sensors to determine the distance, speed,
energy, can be used for intelligence and targeting data
and potentially altitude of an object. Radars operate on
because they are closely associated with heat sources. X-
different radio and microwave frequencies, depending on
rays are routinely used for aircraft maintenance to identify
their purpose. Lower-band frequencies provide a larger
cracks in airframes. Finally, gamma rays are high-energy
picture of the battle space, although, due to the amount of
radiation and help identify potential nuclear events. The
clutter or radar return (how much radio signal is returned to
following discussion focuses on the DOD’s use of the radio
the radar), these systems are not able to provide target-
wave, microwave, and infrared aspects of the spectrum.
quality pictures. Higher-band frequencies provide target-
Applications of the Spectrum
quality pictures, yet lack the same effective range. Radar
and LIDAR systems are commonly associated with air
The military uses the entire spectrum to support intelligence
defense, military aviation, artillery, and space systems.
and military operations. These applications range from
using very low frequency radio waves to communicate with
Signals intelligence (SIGINT) systems primarily collect
submarines underwater, to microwaves as a continuous
spectrum emissions. These passive systems—that is, they
datalink between aircraft, and to lasers in the infrared and
do not emit their own signal—can listen to radio and radar
ultraviolet ends of the spectrum to dazzle satellite sensors
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Defense Primer: Military Use of the Electromagnetic Spectrum
frequencies and observe heat signatures of personnel,
would potentially eliminate DOD’s ability to use these
missiles, aircraft, artillery, and vehicles.
systems. DOD could use funds from these auctions, through
the Spectrum Relocation Fund, to develop new technologies
Other Applications
and relocate displaced technologies to a new place on the
Militaries use the spectrum to target and potentially attack
spectrum.
adversaries. Missiles in general, and anti-air munitions in
particular, use either infrared or radar for terminal guidance
Congress has also recently passed legislation impacting the
(i.e., guiding a missile once it has been launched) to targets.
military’s use of the spectrum, particularly in terms of
Electronic jammers are used to deny an adversary access to
spectrum allocation and electronic warfare. Recent
the spectrum. These jammers are primarily used in the radio
congressional actions in the National Defense Authorization
wave and microwave frequencies (and sometimes paired
Acts (NDAAs) include the following:
together), thereby preventing communications (both
terrestrially and space-based) as well as radar coverage.
FY2017 NDAA. Section 234 authorized the Secretary
Militaries have also begun using lasers to disable
of Defense to develop a pilot program to modernize and
intelligence collection sensors, provide a potential kinetic
field electromagnetic spectrum warfare systems. Section
kill against small unmanned aerial systems (aka “drones”),
240 required DOD to develop an electronic warfare
and communicate with satellites.
strategy. Section 1044 added protections to certain
federal spectrum operations.
Types of Spectrum Operations
Numerous military operations use the spectrum. One type is
FY2018 NDAA. Section 1697 authorized the Secretary
command and control. Command and control uses all of
of Defense to establish a pilot program to assess the
these applications to develop a common operating picture
viability of mapping DOD’s usage of the spectrum.
and communicate the commander’s orders. Command and
Section 1608 required the Secretary of the Air Force to
control is resourced according to a unit’s size and mission
submit a report on the Secretary’s views and plans using
focus, from a few radios and computers for platoon- and
transaction authority to acquire commercial satellite
company-level operations to specialized satellites and
bandwidth.
aircraft for joint operations such as nuclear command and
control. Command and control aircraft, such as the E-8C
FY2019 NDAA. Section 255 required DOD to perform
Joint STARS, use communications systems and synthetic
an independent assessment of current electronic warfare
aperture radars to develop a comprehensive picture of the
plans and programs. Section 1053 directed the Secretary
battlespace to direct ground forces to their most effective
of Defense to establish process and procedures to
positions for countering enemy forces.
“develop, integrate and enhance electronic warfare
mission area and the conduct of joint electromagnetic
Electronic warfare uses the spectrum to gain and maintain
spectrum operations in all domains across the
military access to the spectrum. SIGINT capabilities allow
Department of Defense and ensure that such processes
military forces to understand where adversary forces are
and procedures provide for integrated defense-wide
located as well as what frequencies they use for
strategy, planning, and budgeting with respect to the
communications and radars. This intelligence, called
conduct of such operations.”
electronic support by the military, is then used to develop
an operational plan to jam (i.e., attack an adversary’s use of
Relevant Statutes
the spectrum) radio frequencies. Using SIGINT capabilities
on their own forces, militaries can develop techniques to
Title 10, U.S. Code, Armed Forces, Section 488: Management
protect themselves from attacks.
and review of electromagnetic spectrum
Low observable weapons systems manipulate the spectrum
CRS Products
to reduce their electromagnetic signature—such as radar
CRS In Focus IF11118, Defense Primer: Electronic Warfare, by
return, radio emission, and even heat. This can range from
John R. Hoehn
reducing a radar signature, to creating narrow radio beams
to reduce the probability of detection or intercept, to
Other Resources
reducing spectrum emissions entirely. These design
approaches can be used in ships (e.g., Zumwalt-class
DOD Instruction 4650.01. Policy and Procedures for
destroyer), aircraft (e.g., the B-2 Spirit and the F-35
Management and Use of the Electromagnetic Spectrum.
Lightning II), and radar systems (e.g., the AN/APG-81
Incorporating Change. 1 Oct 17, 17
actively electronically scanned array radar).
DOD Instruction 3222.03. DOD Environmental Effects Program
Incorporating Change. 2 Oct 10 17
Congressional Interest in the Spectrum
Joint Pub. 6-01 Joint Electromagnetic Spectrum Management
Congress has actively supported the deployment of fifth
Operations
generation (5G) technologies, identifying spectrum used for
5G, and amending federal rules and regulations to facilitate
deployment of 5G infrastructure. The Federal
Communications Commission is auctioning spectrum for
John R. Hoehn, Analyst in Military Capabilities and
5G, which DOD currently uses for satellite communications
and weather radars. Auctioning this part of the spectrum
Programs
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Defense Primer: Military Use of the Electromagnetic Spectrum
IF11155
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