Radar System Engineering

SEC. 17.2] THE ELEMENTS OF RADAR RELAY 681
directional or controlled in direction. The first situation is by far the
simpler from the technical standpoint since large antenna gains can be
used in a very simple manner.
17.2. The Elements of Radar Relay .—One obvious method of relaying
radar information is to televise an indicator screen at the radar site and to
transmit the information by existing television means. This system
leads to a loss both in signal-to-noise ratio and in resolution because
persistent displays do not televise well. Furthermore, any single
televised display would have to be a PPI presenting the maximum radar
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I
Video
I
Receiver
Trigger pulse
1’1
signals
Synchronizer
Y
Radar statton
Receiver -
P~&t3n
transmitter
Scan data
I
Display station
Video signals
*
b
Trigger pulse
F1m 17.1.—Elements of a simple radar relay system. In some caaes electric-al data from
the analyzer can be used directly to generate the indicator sweepa.
range, with the result that much inherent resolution is immediately lost
even though expanded displays might be used at the receiving end. The
first, but not the second, of these difficulties might be overcome by storing
the information on an Orthicon or other storage device rather than on a
cathode-ray tube.
A far superior method is to transmit the original radar data in such a
way that any desired displays can be produced at the receiving location in
exactly the same way as can be done at the radar itself. To do this, it is
necessary to provide at the receiving station: radar video signals, the
modulator trigger (or the pulse itself ), and a mechanical motion (or its
electrical equivalent) that faithfully reproduces the motion of the scanner.
The elements of a system for transmitting this information are
indicated in Fig. 17.1. The radar data are delivered from the set to a
“synchronizer” which. arranges them in proper form to modulate the