electronics. Because of this, the 52C has significant
improvements over earlier versions of the 52 radar in
the areas of detection, reliability, and maintenance.
The antenna assembly (fig. 2-1) is a planar array,
tilted back at an angle of 25 degrees. This 25-degree tilt
allows the antenna to provide high-elevation coverage.
The array is a collection of rows of slotted waveguides
and is fed RF from a feed system running the length of
one side of the total array assembly. This antenna scans
in the vertical plane by transmitting different
frequencies, as selected by a digital computer.
The AN/SPS-52C radar has four modes of
operation: high angle, long range, high data rate, and
MTI (Moving Target Indicator). The operator selects
the appropriate mode, depending on the threat type and
environment. The primary mode is high angle. In this
mode, the radar provides coverage to a range of
approximately 180 miles and an elevation of
approximately 45 degrees. In the long-range mode,
t h e r a d a r p r o v i d e s c o v e r a g e t o a r a n g e o f
approximately 300 miles and an elevation of
approximately 13 degrees. The high data rate mode
provides a range of approximately 110 miles and an
elevation of approximately 45 degrees. This mode is
used because of its unique ability to acquire pop-up
and close-in targets quickly. The MTI mode is useful in
a high-clutter environment (such as weather in extreme
sea-state conditions) where targets are normally hard
to locate. Coverage is about 70 miles and up to an
elevation of 38 degrees.
The 52C radar is used with the SYS-1/SYS-2 radar
system. The SYS-1/SYS-2 system coordinates all
radar sensors on a ship into a single system. It does this
by using a processor designed around integrated
automatic detection-and-tracking (IADT). The
advantage of using such a system is that the unique
characteristics of the various ships radars can be
integrated, resulting in more accurate and quicker
detection of threats. This is part of a program for
non-AEGIS class ships called New Threat Upgrade
The AN/SPS-52C radar is presently found on the
WASP (LHD) class and the TARAWA (LHA) class
amphibious assault ships. It will eventually be replaced
by the AN/SPS-48E.
The AN/SPS-48 radar is a complete system
upgrade of the AN/SPS-52C including all component
elements transmitter, receiver, computer (radar and
automatic detection and tracking), frequency
synthesizer and height display indicator. Figure 2-2
shows an antenna for the SPS-48 radar on the USS
Boxer LHD-4 (see arrow).
The SPS-48 radar is a long-range, three-
dimensional, air-search radar system that provides
contact range, bearing, and height information to be
displayed on consoles and workstations. It does
this by using a frequency-scanning antenna,
which emits a range of different frequencies in
the E/F band. The SPS-48 radar has three power
modes: high, medium, and low.
An upgrade was needed because the 52C radars
single elevation beam could not dwell long enough in
any particular direction. To solve this problem, the 48
series uses a process that stacks nine beams (a train of
n i n e p u l s e s a t d i ff e r e n t f r e q u e n c i e s ) i n t o a
pulse-group. The nine beams simultaneously scan a
5-degree elevation area, allowing the stack to cover 45
degrees of elevation.
Two versions of the SPS-48 are currently in use:
the 48C and the latest version, the 48E. Maximum
elevation has increased somewhat, 65 degrees versus
45 degrees for the 52C. The E version has twice the
radiated power of the 48C, developed by reducing
the sidelobes and increasing the peak power. Receiver
sensitivity is increased and the 48E has a four-stage
solid state transmitter. The main operating modes are:
EAC (Equal Angle Coverage)The radars
energy is concentrated at a low angle.
MEM (Maximum Energy Management)Both
high and medium power are regulated.
AEM (Adaptive Energy Management)Allows
the radar to be adapted to a priority target radar
Figure 2-1.AN/SPS-52 radar antenna.