Radar System Engineering

296 ANTENNAS, SCANNERS, AND STABILIZATION [SEC. 9.14
to be described was developed for the 3-cm band to provide coastal
defense batteries with accurate target position and “ splash-spotting”
data for fire control. An azimuth beamwidth of 0.55° and a short pulse
(* @cc) make accurate tracking possible in both azimuth and range.
The sector that is rapidly scanned is 10° wide and the center of this sector
may be swung to any azimuth position for search purposes.
Externally the scanner consists of a mount, which ordinarily rests on a
tower platform; the antenna housing, 143 by 56 by 27.5 in., constructed
FIG. 924.-Detail
Antenna
(left . z
end)
r 1+x ~ wavaguide
of AN/APQ-7 r-f switch.
of plywood; and the copper-coated plywood reflector, 2 by 12 ft, hinged
to the deck of the housing (Fig. 9.25). The reflector is a half parabolic
cylinder of l-ft focal length, and is fed by the 1l-ft by 1.4-in. linear
aperture of the enclosed portion of the antenna to produce the beam 0.55°
in azimuth by 3° in elevation. Terminating in this aperture is a long
“horn,” a parallel-plate region of copper-coated plywood, folded as in Fig.
9.26. The conducting surfaces are spaced } in. apart and increase in
width from about 2 ft at the edge AA to about 11 ft at the edge BB.
This horn extends over a length of about 12 ft and is folded three times.
The feeding edge AA of the parallel plates consists of a boundary which
forms a 90° arc, 14* in. in radius. Radiation is fed into the parallel
plates between these flanges by four feed horns, each 2 in. wide, with
suitable chokes meeting the flanges. The four horns are mounted on
four radial waveguides which are fed at their intersection by a four-way
r-f sector switch (Fig. 9.27). This switch consists mainly of a rotary
joint’ which terminates in four waveguides F. at 90° to each other. These
1SeeFig. 11.13.