DISPLAYING RADAR SWEEP,
VIDEO, AND SYMBOLS
In the following sections, we cover the steps
involved in displaying radar sweep, video, and
symbols on the PPI used in the Data Display Group
RADAR SWEEP AND VIDEO
The PPI scan or sweep originates in the center of
the circular screen.
The sweep progresses (traces)
outward until the edge of the screen or the end of
sweep is reached. One sweep occurs for each radar
pulse transmitted. The angle of the sweep varies as
the position of the rotating radar antenna varies,
resulting in a clockwise or counterclockwise rotation
of the sweep on the screen. As the antenna is rotated,
the sweep rotates around the CRT in synchronism
with the antenna position.
The PPI provides real-time range and bearing
display of radar, sonar, or IFF/SIF returns. The sweep
trace is intensified (brightened) by video signals that
indicate the range of the return. The angle of the
sweep on the screen indicates the bearing of the
The PPI console sweep and video display is
generated from data received from the radar, sonar, or
IFF. Ancillary equipment converts the data into a
format that can be used by the PPI console. The PPI
console receives the following information from the
Digital sweep (digital DC/DU pulse trains)
Sign of X and sign of Y
Sweep timing (end-of-sweep and range-mark
The digital sweep pulse trains (DC/DU) are used
to control the deflection of the CRT electron beam.
They indicate the changing sweep coordinates for the
display of the rotating sweep.
Sign of X and Sign of Y
The sign of X and the sign of Y determine the
quadrant in which the sweep and video will be
Sweep timing signals include range-mark signals
and the end-of-sweep signal. The zero-mile range
mark is used to start the sweep deflection outward
from the center of the screen.
signals are displayed as intensified rings on the CRT
so that a relationship between the radar video and
range may be established.
The end-of-sweep signal causes the CRT beam to
be blanked and retraced to the center of the CRT. The
end-of-sweep signal also resets various counters in
preparation for the next sweep.
Radiation reflections from the radar, sonar, or
IFF/SIF are received as video signals. The video
signals are displayed as an intensification of the
The generation of display symbology is integrated
with the development of the sweep and video.
Symbols are generated from data words outputted by
The following steps are required to
paint a symbol:
Blank the sweep
M o v e t h e C R T b e a m t o t h e s y m b o l
Paint the symbol
Blank the CRT beam
Move the beam back to sweep position