Biomedical Engineering Reference
In-Depth Information
Figure 5.12
(a) Measured transmitted amplitudes of S
x
(black) and S
y
(red). (b) Relative phase between S
x
and S
y
. The backscattering-immune
state is highlighted by light blue. The nearly equaling amplitudes of S
x
and
S
y
and nearly 90
◦
phase shift show that the output EM wave is nearly LH
circularly polarized. (c) Measured transmitted amplitudes of S
x
(black) and
S
y
(red).(d)RelativephaseshiftbetweenS
x
andS
y
.Thedominantamplitude
in the component of S
x
and the nearly 180
◦
phase shift between S
x
and S
y
show thatthe outputEM wave is nearly x-linear polarized.
can propagate. This implies robust transport in this frequency
region. Both simulation and microwave total transmission spectra
areplottedinFig.1.1(b,c),whichagreewellwiththebandstructure.
In principle, the transmitted wave should be LH polarized inside
thepolarizationgap,eveniftheincidencewaveislinearlypolarized.
This is also verified by the experimental results shown in light blue
region of Fig. 1.12(a,b). The spectra of the transmitted amplitudes
S
x
and S
y
are almost the same, and the relative phase is nearly
90
◦
. However, outside the polarization gap from 9.36 to 9.78 GHz,
the measured transmitted amplitudes S
y
are almost twice as the
amplitudes S
x
from 9.59 to 9.78 GHz, while the relative phases are
nearly 270
◦
, indicating that the transmitted waves are of elliptical
polarization. The amplitudes S
x
and S
y
are almost the same from
9.36 to 9.59 GHz, while the relative phase with the value of around
270
◦
, showing that the transmitted waves are of RH polarization.
