March 27, 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
depend on the spectrum to function. These applications can
Department of Defense (DOD) concepts, such as net-centric
be combined to provide an overall military capability, such
warfare and multi-domain battle, increases the military’s
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—i.e., they do
datalink between aircraft, and to lasers in the infrared and
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,
communications and weather radars. Auctioning this part of
missiles, aircraft, artillery, and vehicles.
the spectrum would potentially eliminate DOD’s ability to
use these systems. DOD could use funds from these
Other Applications
auctions, through the Spectrum Relocation Fund, to develop
Militaries use the spectrum to target and potentially attack
new technologies and relocate displaced technologies to a
adversaries. Missiles in general, and anti-air munitions in
new place on the spectrum.
particular, use either infrared or radar for terminal guidance
(i.e., guiding a missile once it has been launched) to targets.
Congress has also recently passed legislation impacting the
Electronic jammers are used to deny an adversary access to
military’s use of the spectrum, particularly in terms of
the spectrum. These jammers are primarily used in the radio
spectrum allocation and electronic warfare. Recent
wave and microwave frequencies (and sometimes paired
congressional actions in the National Defense Authorization
together), thereby preventing communications (both
Acts (NDAA) include the following:
terrestrially and space-based) as well as radar coverage.
Militaries have also begun using lasers to disable
FY2017 NDAA. Sec. 234 authorized the Secretary of
intelligence collection sensors, provide a potential kinetic
Defense to develop a pilot program to modernize and
kill against small unmanned aerial systems (aka “drones”),
field electromagnetic spectrum warfare systems. Sec.
and communicate with satellites.
240 required DOD to develop an electronic warfare
strategy. Sec. 1044 added protections to certain federal
Types of Spectrum Operations
spectrum operations.
Numerous military operations use the spectrum. One type is
command and control. Command and control uses all of
FY2018 NDAA. Sec. 1697 authorized the Secretary of
these applications to develop a common operating picture
Defense to establish a pilot program to assess the
and communicate the commander’s orders. Command and
viability of mapping DOD’s usage of the spectrum. Sec.
control is resourced according to a unit’s size and mission
1608 required the Secretary of the Air Force to submit a
focus, from a few radios and computers for platoon and
report on the Secretary’s views and plans using
company level operations to specialized satellites and
transaction authority to acquire commercial satellite
aircraft for joint operations such as nuclear command and
bandwidth.
control. Command and control aircraft, such as the E-8C
Joint STARS, uses communications systems and synthetic
FY2019 NDAA. Sec. 255 required DOD to perform an
aperture radars to develop a comprehensive picture of the
independent assessment of current electronic warfare
battlespace to direct ground forces to their most effective
plans and programs. Sec. 1053 directed the Secretary of
positions for countering enemy forces.
Defense to establish process and procedures to
“develop, integrate and enhance electronic warfare
Electronic warfare uses the spectrum to gain and maintain
mission are and the conduct of joint electromagnetic
military access to the spectrum. SIGINT capabilities allow
spectrum operations in all domains across the
military forces to understand where adversary forces are
Department of Defense and ensure that such processes
located as well as what frequencies they use for
and procedures provide for integrated defense-wide
communications and radars. This intelligence, called
strategy, planning, and budgeting with respect to the
electronic support by the military, is then used to develop
conduct of such operations.”
an operational plan to jam (i.e., attack an adversary’s use of
the spectrum) radio frequencies. Using SIGINT capabilities
Relevant Statutes
on its own forces, militaries can develop techniques to
protect themselves from attacks.
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
Other Resources
return, radio emission, and even heat. This can range from
DOD Instruction 4650.01. Policy and Procedures for
reducing a radar signature, to creating narrow radio beams
Management and Use of the Electromagnetic Spectrum.
to reduce the probability of detection or intercept, to
Incorporating Change. 1 Oct 17, 17
reducing spectrum emissions entirely. These design
DOD Instruction 3222.03. DOD Environmental Effects Program
approaches can be used in ships (e.g., Zumwalt-class
Incorporating Change. 2 Oct 10 17
destroyer), aircraft (e.g., the B-2 Spirit and the F-35
Lightning II), and radar systems (e.g., the AN/APG-81
Joint Pub. 6-01 Joint Electromagnetic Spectrum Management
actively electronically scanned array radar).
Operations
Congressional Interest in the Spectrum
Congress has actively supported the deployment of fifth
generation (5G) technologies, identifying spectrum used
John R. Hoehn, Analyst in Military Capabilities and
5G, and amending federal rules and regulations to facilitate
Programs
deployment of 5G infrastructure. The Federal
IF11155
Communications Commission is auctioning spectrum for
5G, which the DOD currently uses for satellite
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Defense Primer: Military Use of the Electromagnetic Spectrum
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