For further information on the construction and
discernible video signals. Because the radar frequen-
operation of microwave component, review NEETS
ties are very high and difficult to amplify, a super-
Module 11, Microwave Principles, NAVEDTRA 172-
heterodyne receiver is used to convert the echoes to a
11-00-87.
lower frequency, called the intermediate frequency
(IF), which is easier to amplify.
Duplexer
TYPES OF RADAR SYSTEMS
The duplexer is essentially an electronic switch
that permits a radar system to use a single antenna to
both transmit and receive. The duplexer must connect
the antenna to the transmitter and disconnect the
antenna from the receiver for the duration of the trans-
mitted pulse. The switching time is called receiver
recovery time, and must be very fast if close-in targets
are to be detected.
Antenna System
The antenna system routes the pulse from the
transmitter, radiates it in a directional beam, picks up
the returning echo, and passes it to the receiver with
a minimum of loss. The antenna system includes the
antenna, transmission lines, and waveguide from the
transmitter to the antenna, and transmission lines and
waveguide from the antenna to the receiver.
Because of different design parameters, no single
radar set can perform all the many radar functions
required for military use. The large number of radar
systems used by the military has forced the develop-
ment of a joint-services classification system for
accurate identification of radars. Radar systems are
usually classified according to their specific function
and installation vehicle. The joint-service stand-
ardized classification system divides these broad cate-
gories for more precise identification.
Since no single radar system can fulfill all the
requirements of modern warfare, most modern war-
ships, aircraft, and shore installations have several
radar sets, each performing a specific function. A
shipboard radar installation may include surface-
search and navigation radars, a 3-D radar, an air-
search radar, and various fire-control radars.
Receiver
Table 1-2 is a listing of equipment identification
indicators. You can use this table and the radar nom-
The receiver accepts the weak RF echoes from the
enclature to identify the parameters of a particular
antenna system and routes them to the indicator as
radar set.
1-7
