Plane wave synthesis : a new approach to the problem of antenna near-field / far field transformation.

In the recently evolved fields of satellite and
space communications as well as in a number of related
areas, a vital requirement is an accurate knowledge of
the radiating and receiving characteristics of the transmitting
and receiving antennas as they appear at a large
distance (in the so called far-field region). It is often
impossible to obtain a direct measurement of the performance
of an antenna and in such cases where it is possible, the
accuracy obtainable is frequently limited by the many
difficulties associated with the process.
Over recent years, a number of techniques have begun
to appear which allow measurement of data close to the test
antenna (in the near-field region) and then by mathematical
processing (the transformation) predict what the far-field
performance will be. The earlier techniques while being
basically simple from a mathematical viewpoint, were not
completely general and tended to involve special, sophisticated,
hardware. The later techniques use the most
general spherical scanning system but involve much more
complicated processing.
A new approach to the problem is presented in which
much of the computational burden is pre-processed so that
the size and complexity of the ultimate prediction task is
reduced. The various measurement systems are considered
briefly and the spherical system is formulated in detail.
Simulated and experimental predictions are carried out
and studies are included of the various errors likely to
be present and their effects. The important parameters,
including the sampling criterion, are discussed in some
detail.
It is shown that this technique has the potential
for producing rapid and accurate predictions of antenna
far-field patterns including the facility of compensation
for the characteristics of the measurement probe.