Updated August 21, 2020
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,
and relocate displaced technologies to a new place on the
missiles, aircraft, artillery, and vehicles.
spectrum.
Other Applications
Congress has also recently passed legislation impacting the
Militaries use the spectrum to target and potentially attack
military’s use of the spectrum, particularly in terms of
adversaries. Missiles in general, and anti-air munitions in
spectrum allocation and electronic warfare. Recent
particular, use either infrared or radar for terminal guidance
congressional actions in the National Defense Authorization
(i.e., guiding a missile once it has been launched) to targets.
Acts (NDAAs) include the following:
Electronic jammers are used to deny an adversary access to
the spectrum. These jammers are primarily used in the radio
FY2017 NDAA. Section 234 authorized the Secretary
wave and microwave frequencies (and sometimes paired
of Defense to create a pilot program to modernize and
together), thereby preventing communications (both
field spectrum warfare systems. Section 240 required
terrestrially and space-based) as well as radar coverage.
DOD to develop an electronic warfare strategy. Section
Militaries have also begun using lasers to disable
1044 protected certain federal spectrum operations.
intelligence collection sensors, provide a potential kinetic
kill against small unmanned aerial systems (aka “drones”)
FY2018 NDAA. Section 1697 authorized the Secretary
,
of Defense to establish a pilot program to assess the
and communicate with satellites.
viability of mapping DOD’s usage of the spectrum.
Types of Spectrum Operations
Section 1608 required the Secretary of the Air Force to
submit a report on the plans using transaction authority
Numerous military operations use the spectrum. One type is
to acquire commercial satellite bandwidth.
command and control. Command and control (C2) uses all
of these applications to develop a common operating
FY2019 NDAA. Section 255 required DOD to perform
picture and communicate the commander’s orders. C2 is
an independent assessment of current electronic warfare
resourced according to a unit’s size and mission focus, from
plans and programs. Section 1053 directed the Secretary
a few radios and computers for platoon- and company-level
of Defense to establish process and procedures to
operations to specialized satellites and aircraft for joint
“develop, integrate and enhance electronic warfare
operations such as nuclear C2. C2 aircraft, such as the E-8C
mission area and the conduct of joint electromagnetic
Joint STARS, use communications systems and radars to
spectrum operations in all domains across the
develop a picture of the battlespace to direct forces to their
Department of Defense and ensure that such processes
most effective positions for countering enemy forces.
and procedures provide for integrated defense-wide
strategy, planning, and budgeting with respect to the
Electronic warfare uses the spectrum to gain and maintain
conduct of such operations.”
military access to the spectrum. SIGINT capabilities allow
FY2020 NDAA. Section 254 required DOD to develop
military forces to understand where adversary forces are
a strategy and implementation plan for 5G systems.
located as well as what frequencies they use for
Section 256 required DOD to perform an independent
communications and radars. This intelligence, called
assessment of current electronic warfare plans and
electronic support by the military, is then used to develop
programs, similar to the FY2019 section.
an operational plan to jam (i.e., attack an adversary’s use of
the spectrum) radio frequencies. Militaries can develop
techniques to protect themselves from attacks using
Relevant Statutes
SIGINT capabilities on their own forces.
Title 10, U.S. Code, Armed Forces, Section 488: Management
and review of electromagnetic spectrum
Low observable weapons systems manipulate the spectrum
to reduce their electromagnetic signature—such as radar
CRS Products
return, radio emission, and even heat. This can be achieved
by reducing radar signature, creating narrow radio beams to
CRS In Focus IF11118, Defense Primer: Electronic Warfare, by
reduce the probability of detection, or reducing spectrum
John R. Hoehn
emissions entirely. A few examples of these design
CRS In Focus IF11493, Defense Capabilities: Joint All Domain
approaches include the Zumwalt-class destroyer, the B-2
Command and Control, by Nishawn S. Smagh
Spirit and the F-35 Lightning II, the AN/APG-81 actively
electronically scanned array radar.
Other Resources
Congressional Interest in the Spectrum
DOD Instruction 4650.01. Policy and Procedures for
Management and Use of the Electromagnetic Spectrum.
Congress has actively supported the deployment of fifth
Incorporating Change. 1 Oct 17, 17
generation (5G) technologies, identifying spectrum used for
5G, and amending federal rules and regulations to facilitate
Joint Pub. 6-01 Joint Electromagnetic Spectrum Management
deployment of 5G infrastructure. The Federal
Operations
Communications Commission is auctioning spectrum for
5G, which DOD currently uses for satellite communications
and weather radars. Auctioning this part of the spectrum
would potentially eliminate DOD’s ability to use these
John R. Hoehn, Analyst in Military Capabilities and
systems. DOD could use funds from these auctions, through
Programs
the Spectrum Relocation Fund, to develop new technologies
IF11155
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Defense Primer: Military Use of the Electromagnetic Spectrum
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