Antennas are an increasingly important part of military tactical communications and
information warfare applications, including signals intelligence (SIGINT), direction-finding
(DF) and electronic attack (EA). High performance military antennas can provide transmit and receive capabilities in challenging operational environments.
Military Antenna Types
Military antennas can include directional military antennas, omnidirectional military
antennas and military antenna arrays. Military antennas can be designed around the available space
(a cylinder’s diameter and height) and maximum weight. A military antenna’s low end frequency range
can be increased by increasing the available height for the antenna. A military antenna’s high
end frequency range can be adjusted by selecting different connector types. For example, a
military antenna with an SMA connector can have an upper end frequency of approximately 18 GHz.
A military antenna can be narrowband or ultrawideband. An ultrawideband military antenna can transmit
or receive in all narrowband frequencies (narrowband signals are signals which are not localized in
time and thus which have long duration but narrow frequency) throughout a broad frequency range.
Military Antenna Applications
Military antenna applications include surface ships, subsurface ships such as submarines, UUVs,
ground vehicles such as Humvees or Jeeps, aircraft including unmanned aerial vehicles (UAVs),
team-transportable and man-portable. The antenna requirements are frequently driven by the application.
For example, weight-sensitive platforms such as UAVs require military antennas which are extremely lightweight.
Platforms such as surface ships or aircraft often require military antennas which have low radar cross section (RCS),
while RCS is much less of a factor for military antennas on platforms such as ground vehicles. An ultrawideband frequency
range is advantageous for any military antenna application, as it enables minimizing the number of antennas required,
for minimal visual profile, reduced space/weight usage, minimal system complexity/greater ease of integration and upgrade.
Military Antenna Performance Metrics
An example of a key performance metric for a military antenna is voltage standing wave ratio
(VSWR). VSWR describes the power transfer from the cable to the antenna, for example, a VSWR level
of 3 means that 75% of the power is accepted and re-radiated by the antenna, rather than being
reflected back to the transmitter. Thus when asked "what frequency range does the military antenna cover",
the answer is typically based on the frequency range for which the antenna has a VSWR < 3.
A further key performance feature for a military antenna is that of nearly constant effective aperture.
With constant effective aperture, even if an adversary changes their frequency, as long as transmission
is at the same power level, the military antenna will maintain its signal strength. With a constant gain
military antenna, as the frequency at which the adversary is operating increases, the operator can start
losing the signal. However, with a military antenna that has increasing gain with frequency,
the signal is maintained even as the adversary changes their frequency.
The typical polarization of a military antenna is vertical linear polarization. Horizontal
polarization leads to much higher path loss and is thus less favored for military antenna
applications, although it is used for other applications, such as television for example.
Additionally, a military antenna can be designed for polarization agility, which is important
for satellite communications, as it enables matching the antenna polarization to the polarization of the signal of interest.
Military Antennas for Multiple Platforms
There is a wide variety of military antenna applications, and different antenna types designed for
particular military platforms on air, land and sea. A thorough understanding of military antenna performance
metrics, such as the examples introduced above, should assist decision-makers in selecting the right COTS or custom military antenna for their application.
