Omnidirectional antenna with high gain, low profile, vertical
polarization, even CP polarization is very difficult to design, although
it is from the dipole. In this book, a novel idea that the running wave
in the coaxial wire is disturbed by the orthogonal slot array on the
cylindrical metal shell is introduced, which radiates the CP wave in
omni-direction. When feeding on two ends of the coaxial wire
respectively, there will appear left hand circularly polarized (LHCP)
omnidirectional radiation or right hand circularly polarized (RHCP)
omnidirectional radiation. By introducing the T-shaped feed structure,
the coaxial wire with slot array can conveniently produce the LHCP and
RHCP radiation diversity with one end feeding. In the further, combining
with the directional antenna, it will generate the pattern diversity in
the half-sphere space. The antenna of the coaxial wire with slot array
can further transform into conical CP beam antenna if the coaxial wire
becomes into a conical frustum. By introducing the PIN diode into the
slot, the antenna of the coaxial wire with slot array can radiate the
reconfigurable directional beam by switching the states of the PIN
diodes. By introducing a novel switchable microwave circuit, the
omnidirectional /directional pattern switchable antenna can be realized
easily.This book proposes a continues method to develop the
potentialities of the omnidirectional antenna. And the readers can study
the method or ideas of the omnidirectional slots antenna, even graft the
CP or diversity methods to other antennae.
