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Testing of large (high-gain) antennas
at submillimetre wavelengths is a formidable task. The classical far-field
method does not work in the Earth's atmosphere because the atmospheric loss is
too high - for this very reason we must launch the future scientific telescopes
to space outside the atmosphere. The near-field scanning method has been used
with some success up to 650 GHz. The applied near-field methods give useful
information only on the main beam and its vicinity, because the field-sampling
is typically very sparse. Reflector-based compact antenna test range (CATR)
measurements have been carried out up to 500 GHz. Recently, also hologram-based
CATR measurements have been carried at 322 GHz. This short course discusses the
techniques and limitations of the various test methods, and introduces the
participants to the hologram-based CATR and near-field scanning also by
laboratory demonstrations/exercises.
The participants have a choice to
study a related specific topic prior to the short course, write a brief report
and present that to other participants during the course.
The lectures include the following:
introduction, submm-wave instrumentation, near-field scanning, near field to
far field transformation, compact antenna test range (CATR), CATR based on
reflectors, CATR based on a lens, CATR based on a hologram, site definition,
hologram design, hologram fabrication, construction of a hologram based CATR,
quiet-zone testing, antenna testing in a hologram based CATR, analysis of
measurement results, future developments.
The laboratory demonstrations
(excercises) include the following:
- measurement of a horn antenna
- scanning of near field or quiet
zone field
- antenna measurement in a hologram
CATR
- elimination of disturbing
scatterer effect in a CATR
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