The preceding paragraphs indicated that radar systems are divided into types based on the designed
use. This section presents the general characteristics of several commonly used radar systems. Typical
characteristics are discussed rather than the specific characteristics of any particular radar system.
Search radar, as previously mentioned, continuously scans a volume of space and provides initial
detection of all targets within that space. Search radar systems are further divided into specific types,
according to the type of object they are designed to detect. For example, surface-search, air-search, and
height-finding radars are all types of search radar.
A surface-search radar system has two primary functions: (1) the detection and determination of
accurate ranges and bearings of surface objects and low-flying aircraft and (2) the maintenance of a 360-
degree search pattern for all objects within line-of-sight distance from the radar antenna.
The maximum range ability of surface-search radar is primarily limited by the radar horizon;
therefore, higher frequencies are used to permit maximum reflection from small, reflecting areas, such as
ship masthead structures and the periscopes of submarines. Narrow pulse widths are used to permit a high
degree of range resolution at short ranges and to achieve greater range accuracy. High pulse-repetition
rates are used to permit a maximum definition of detected objects. Medium peak power can be used to
permit the detection of small objects at line-of-sight distances. Wide vertical-beam widths permit
compensation for the pitch and roll of own ship and detection of low flying aircraft. Narrow horizontal-
beam widths permit accurate bearing determination and good bearing resolution. For example, a common
shipboard surface-search radar has the following design specifications:
Transmitter frequency 5,450-5,825 MHz
Pulse width .25 or 1.3 microseconds
Pulse-repetition rate between 625 and 650 pulses per second
Peak power between 190 and 285 kW
Vertical beam width between 12 and 16 degrees
Horizontal beam width 1.5 degrees
Surface-search radar is used to detect the presence of surface craft and low flying aircraft and to
determine their presence. Shipboard surface-search radar provides this type of information as an input to
the weapons system to assist in the engagement of hostile targets by fire-control radar. Shipboard surface-
search radar is also used extensively as a navigational aid in coastal waters and in poor weather
conditions. A typical surface-search radar antenna is shown in figure 1-24.