This thesis describes a mathematical and experimental study
of circular arrays of directional antennas.
For directional pattern synthesis in circular arrays of
omnidirectional elements, mode-analysis or Fourier
harmonic analysis technique has previously been used. This
thesis describes the effect of using any directional
element on the mode properties - in the horizontal plane,
and on the vertical directional pattern of such arrays.
The effect of random amplitude and phase errors in the
excitation of circular arrays and of mutual coupling with
reference to directional pattern synthesis is also studied.
A procedure is outlined for designing circular arrays of
directional elements and a design of an experimental 16-
element circular array is then presented. This is an
8 foot diameter array of 16 wideband elements each having
a pattern of the form (l+cosφ) for operation at 200-400MHz
frequency band. Various mode patterns are computed for
the array to determine their purity. The theoretical
wideband performance of the array is also examined.
New techniques are described for the synthesis of single
and 2n sharp nulls in otherwise omnidirectional patterns
of circular arrays and the mechanism for independent
steering of these nulls is also described. Patterns are
computed to demonstrate and theoretically study the
techniques.
Finally, experimental results are presented to
complement the theoretical study of circular arrays and
null patterns