b. The
most
important
points
to
remember
about
waveguide
are
as
follows:
(1) Waveguide is a hollow pipe, usually rectangular, used to guide
microwave energy.
(2) Waveguide is a very efficient transmission medium because it has
very little loss of energy.
(3) Waveguide is used principally
to
guide
energy
to
antennas, test equipment, and dummy loads.
(4) A choke joint is a device used to join two sections of waveguide.
(5) Waveguide bends are smooth or mitered.
(6) Twisted
waveguide
changes
the
plane
of
the
field
within
a
waveguide.
(7) Flexible waveguide is usually used when a loss of energy can be
tolerated.
(8) Waveguide must be tuned to prevent serious reflections.
(9) A
shutter
and
resistive
card
are
two
types
of
waveguide
attenuators.
Learning Event 2:
RADAR ANTENNAS
1.
General.
You know that radar operates on the echo principle. The magnetron
generates short regularly-spaced RF pulses when excited by short DC pulses
from the modulator. These high-power RF pulses are transmitted into space
in a narrow beam from a directional antenna (Figure 131). A target in the
path of the radar beam sends back some of the RF energy in the form of
echoes. The antenna intercepts these echoes and directs them to a sensitive
receiver and finally to the radar indicator.
184
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