Radar System Engineering

606 EXAMPLES OF RADAR SYSTEM DESIGN [SEC. 15.10
3. The ultimate capabilities of radar components should not differ
greatly throughout the wavelength region from 8 cm to 25 cm,.
Somewhat higher transmitter power will be available at the longer
wavelengths. At the time of the development described, performance
of existing components was better in the 10-cm region than
at any other wavelength suitable for this application.
15.10. Components Design.—The general system parameters chosen
as a result of considerations outlined in the last few sections are as follows:
Wavelength.
10.15toll.10cm
Pulse length,
lpsec
PltF. ., .,, , . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4oopps
Azimuth scan rate,.,.,..
,lto6rpm
,btenn~aperture, lcnverbcam ..., Sby25ft
Antenna aperture, upper be~m, . . . . .
5by25ft
Beamwidth. . . . . . . . . . . . . . . . . . . . . 1°
It now remains to describe the components of the radar set.
The Antenna.—The antenna represented a departure from the usual
paraboloid of revolution which had been used for earlier microwave
antennas. It is described and illustrated in Sec. 9.12.
In the final design of the antenna mount, the reflectors for the upper
and lower beams are mounted back-to-back, so that their axes differ
by 180°. This complicates somewhat the mechanism for transmission
of azimuth-angle data from the antenna mount to the indicators. lVhen
a given indicator is switched from upper-beam data to lower-beam data,
the mechanism controlling angular orientation of the sweep must be
suddenly shifted through a large angle. Operationally, on the other
hand, this arrangement was a considerable convenience. A given aircraft
could frequently be seen in either beam, an”d by switching beams
every half-revolution of the antenna the operator could double the rate
at which he received plots.
Lfore recent advances in antenna development have introduced
antenna types, other than the parabolic cylinder fed by a linear array,
which give the beam characteristics required for long-range surveillance
and control. The method that now appears most promising uses a
section of a paraboloid of revolution for the reflector. The periphery
of this surface is cut to give an aperture several times greater in width
than in height, and the reflector is fed by several horns or dipoles arranged
along a vertical line passing through the focus.
The latter antenna system’ has the following advantages over the
linear array:
1Similm antennas are described in Chap, 14, Vol. 12 of this ssries,