Updated September 27, 2021
Defense Primer: Military Use of the Electromagnetic Spectrum
Since the introduction of the two-way radio in the early
ultraviolet ends of the spectrum to dazzle satellite sensors
1900s, militaries have been interested in the
and destroy drones. The majority of military
electromagnetic spectrum (“the spectrum”). The
communications capabilities use radio waves, microwaves,
proliferation of spectrum-dependent systems in all military
and infrared frequencies. Nearly every modern weapons
domains—air, land, sea, space, and cyberspace—along with
system—airplanes, satellites, tanks, ships, and radios—
Department of Defense (DOD) concepts, such as net-centric
depends on the spectrum to function. These applications
warfare and multidomain battle, increases the military’s
can be combined to provide an overall military capability,
dependence on the spectrum.
such as command and control or electronic warfare. The
What Is the Spectrum?
following discussion provides a few examples of spectrum
applications.
The electromagnetic spectrum is a series of frequencies
ranging from radio waves to microwaves, visible light, X-
Communications
rays, and gamma rays. As the wavelength of the
Military commanders have become accustomed to
electromagnetic radiation shortens, the waves have a higher
communicating with their forces near-instantaneously.
frequency—how quickly electromagnetic waves follow
Communication includes a range of options from low
each other—and therefore more energy.
bandwidth options, such as transferring small strings of
text, to high data-intensive applications, such as full motion
Figure 1. The Electromagnetic Spectrum
video and video teleconferencing. Radio frequencies are the
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
Source: https://imagine.gsfc.nasa.gov/science/toolbox/
required to transmit. Ground-based radios are typically used
emspectrum1.html.
at short ranges, limited by the line of sight. These short
Different parts of the spectrum serve different military
ranges span no more than 50 miles. In general, militaries
purposes. Radio transmissions have relatively low data
use satellites to communicate over longer distances.
rates—particularly in the very low frequency range.
Situational Awareness
However, they are able to travel long distances and pass
Another application of the spectrum is using radio or
through solid objects like buildings and trees, and are often
microwave frequencies to develop a picture of the battle
used for communications equipment. Microwaves have
space by providing the location of friendly and enemy
higher throughput—data upload and download rates—than
forces. The most common application is radar, however
radio waves and therefore are able to transmit more data,
recently light detection and ranging (LIDAR) systems are
but are more limited in range and can be disrupted by solid
also used. Both technologies send out a signal that is then
objects. Hence, microwaves are often used for radars and
reflected back to sensors to determine the distance, speed,
satellite communications. Infrared waves, which emit
and potentially altitude of an object. Radars operate on
energy, can be used for intelligence and targeting data
different radio and microwave frequencies, depending on
because they are closely associated with heat sources. X-
their purpose. Lower-band frequencies provide a larger
rays are routinely used for aircraft maintenance to identify
picture of the battle space, although, due to the amount of
cracks in airframes. Finally, gamma rays are high-energy
clutter or radar return (how much radio signal is returned to
radiation and help identify potential nuclear events. The
the radar), these systems are not able to provide target-
following discussion focuses on the DOD’s use of the radio
quality pictures. Higher-band frequencies provide target-
wave, microwave, and infrared aspects of the spectrum.
quality pictures, yet lack the same effective range. Radar
Applications of the Spectrum
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
Signals intelligence (SIGINT) systems primarily collect
using very low frequency radio waves to communicate with
spectrum emissions. These passive systems—systems that
submarines underwater, to microwaves as a continuous
do not emit their own signal—can listen to radio and radar
datalink between aircraft, and to lasers in the infrared and
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Defense Primer: Military Use of the Electromagnetic Spectrum
frequencies or observe heat signatures of personnel,
spectrum sharing applications, to allow commercial uses on
missiles, aircraft, artillery, and vehicles.
traditional military frequencies.
Other Applications
Congress continually passes legislation through the annual
Militaries use the spectrum to target and potentially attack
National Defense Authorization Act (NDAA) affecting the
adversaries. Missiles in general, and anti-air munitions in
military’s use of the spectrum, particularly regarding
particular, use either infrared or radar for terminal guidance
governance, spectrum allocation, and electronic warfare.
(i.e., guiding a missile once it has been launched) to targets.
Recent NDAA actions include the following:
Electronic jammers are used to deny an adversary access to
FY2018 NDAA. Section 1697 authorized the Secretary
the spectrum. These jammers are primarily used in the radio
of Defense to establish a pilot program to assess the
and microwave frequencies (and sometimes paired
viability of mapping DOD’s usage of the spectrum.
together), preventing communications (both terrestrially
Section 1608 required the Secretary of the Air Force to
and space-based) as well as radar coverage. Militaries have
submit a report on the plans using transaction authority
also begun using lasers to disable intelligence collection
to acquire commercial satellite bandwidth.
sensors, destroy small unmanned aerial systems (aka
FY2019 NDAA. Section 255 required DOD to perform
“drones”), and communicate with satellites.
an independent assessment of current electronic warfare
Types of Spectrum Operations
plans and programs. Section 1053 directed the Secretary
Numerous military operations use the spectrum. One type is
of Defense to establish process and procedures to
command and control. Command and control (C2) uses all
“develop, integrate and enhance electronic warfare
of these applications to develop a common operating
mission area and the conduct of joint electromagnetic
picture and communicate the commander’s orders. C2 is
spectrum operations in all domains across the
resourced according to a unit’s size and mission focus, from
Department of Defense and ensure that such processes
a few radios and computers for platoon- and company-level
and procedures provide for integrated defense-wide
operations to specialized satellites and aircraft for joint
strategy, planning, and budgeting with respect to the
operations such as nuclear C2. Aircraft like the E-8C Joint
conduct of such operations.”
STARS, use communications systems and radars to develop
FY2020 NDAA. Section 254 required DOD to develop
a picture of the battlespace to direct forces to their most
a strategy and implementation plan for 5G systems.
effective positions for countering enemy forces.
Section 265 required DOD to perform an independent
assessment of current electronic warfare plans and
Electronic warfare uses the spectrum to gain and maintain
programs, similar to the FY2019 section.
military access to the spectrum. SIGINT capabilities allow
military forces to understand where adversary forces are
FY2021 NDAA. Section 152 transferred the
located as well as what frequencies they use for
responsibilities of electromagnetic spectrum operations
communications and radars. This intelligence, called
(EMSO) from Commander, United States Strategic
electronic support by the military, is then used to develop
Command to a responsible entity. Sections 1661-1664
an operational plan to jam (i.e., attack an adversary’s use of
prevent funding and direct an independent assessment of
the spectrum) radio frequencies. Militaries can develop
5G use in the 1550 MHz band, potentially affecting the
techniques to protect themselves from attacks using
Global Positioning System.
SIGINT capabilities on their own forces.
CRS Products
Low observable weapons systems manipulate the spectrum
CRS Report R46564, Overview of Department of Defense Use of
the Electromagnetic Spectrum, by John R. Hoehn, Jil C. Gal agher,
to reduce their electromagnetic signature—such as radar
and Kel ey M. Sayler
return, radio emission, and even heat. This can be achieved
CRS In Focus IF11118, Defense Primer: Electronic Warfare, by
by reducing radar signature, creating narrow radio beams to
John R. Hoehn
reduce the probability of detection, or reducing spectrum
emissions entirely. A few examples of these design
Other Resources
approaches include the Zumwalt-class destroyer, the B-2
DOD. Electromagnetic Spectrum Superiority Strategy
Spirit and the F-35 Lightning II, the AN/APG-81 actively
DOD Directive 3610.01. Electromagnetic Spectrum Enterprise
electronically scanned array radar.
Policy
Congressional Interest in the Spectrum
Joint Pub. 3-85 Joint Electromagnetic Spectrum Management
Congress has actively supported the deployment of fifth
Operations
generation (5G) technologies, identifying spectrum used for
GAO-21-64, DOD Needs to Address Governance and Oversight
5G, and amending federal rules and regulations to facilitate
Issues to Help Ensure Superiority
deployment of infrastructure. The Federal Communications
GAO-21-440T, DOD Needs to Take Action to Help Ensure
Commission is auctioning spectrum for 5G, which DOD
Superiority
currently uses for satellite communications and weather
radars; these auctions would potentially eliminate DOD’s
ability to use these systems. DOD could use funds from
John R. Hoehn, Analyst in Military Capabilities and
these auctions, through the Spectrum Relocation Fund, to
Programs
develop new technologies and relocate displaced
technologies to new frequencies. DOD is investigating
IF11155
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Defense Primer: Military Use of the Electromagnetic Spectrum
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