Radar System Engineering

SEC. 9.14] SCHWA RZSCHILD ANTENNA 295
The transmission line is a waveguide ending in a choke flange attached
to the channel at the pad shown in Figs. 9.19 and 921. The transition is
matched by means of the .joa tran.sformerl illustrated in Fig. 9“23. The
transmissi~n line contains ~he r-f s-titch mentioned above and sketched
in Fig. 9.24. It is at the intersection of
four waveguides. When the vane of the
‘-1
switch is at one of its 45° positions the
4-
energy is directed through the array in
one direction and that 5 to 10 per cent of
the energy which is not radiated is
routed into a matched load. At the 0.100” To magnetron
0.660” O.uo - 1:“
middle of the 60° scan the vane is flipped
To~ples
wit hin 0.05 sec into its other 45° position
and the energy flow in the array is
‘k+ (a)
reversed.
4
Of the many significant facts that
have emerged in the study of the properties
of the Eagle array, two are worth
emphasizing. One is that practically all
defects in the azimuth pattern of such
a long array are caused by phase errors
and not by departures from the desired
partition of energy among the dipoles;
the other is that random phase errors over
lengths corresponding to a few dipoles are
negligible when compared to systematic
phasing errors.
The production scanner weighs 165 lb;
the housing vane weighs 247 lb, including
the gear box and motor. Thus the entire
assembly, exclusive of the two mounting
struts, weighs 412 lb.
~[~~:. ~
I
1.200”
AL
}
Choke
To m~etron I
- 1;“
To dipdes 1
F1c+.9.23.—Jog transition from
the rigid to the expandableguide.
The latter is shown when narrow at
a and wide at b. A section through
A-A is shownin Fig. 9.21.
9.14. Schwarzschild Antema.-It is known (Sees. 9.3 and 11.1) that
energy may be propagated in the space between flat parallel sheets of
metal. In this and the two sections following we shall discuss electrical
scanners in which curved parallel plates are used. In each scanner the
plates are straight along one side; the microwaves escape from the
straight gap between the plates on this side and then illuminate a parabolic
reflector. The electrical scan is a periodic time variation in the
direction of the energy falling upon the reflector. The antenna’ about
1R. M. Robertson, ioc. auf.
2H. A, Straus, “ Brief Description of AN/TPG-1, AN~FPG-1, SCR-598,” RL
Report No. 456, Oct. 8, 1943;also War DepartmentTechnical ManualTM 11-1566.