Biomedical Engineering Reference
In-Depth Information
5.6.3
Microwave Absorber with Surface-Printed Conductive Line Patterns
Another example of a microwave absorber based on the equivalent transfor-
mation of a material constant is a microwave absorber able to change a match-
ing frequency characteristic and produce a thinner absorber. This has been
done by printing small, periodical conductive line patterns on the surface of
the absorbing materials using a single absorbing material [12]. The advantage
of using conductive line patterns is that microwave absorbers can be made
with characteristics capable of changing the matching frequency toward both
a higher and a lower frequency region and yielding a matching characteristic
of multipeaks. This idea is based on the principle that the conductive line pat-
terns printed on the surface of absorbing material can be constructed so as to
provide a behavior either of capacitance or inductance for the absorbing mate-
rial, depending on wavelength.
These microwave absorbers are made by printed thin conductive lines on
the surface of the rubber ferrite as shown in Figure 5.32. Figures 5.32
a
,
b
show
patterns printed with a thin line lattice and cross patterns, respectively. Figures
a
Conductor
c
Magnetic
material
a
b
b
Conductive
plate
t
t
(a)
(b)
Spacer
Magnetic
material
Conductor
a
c
a
c
C
b
b
t
t
Conductive plate
(c)
(d)
FIGURE 5.32
Examples of EM wave absorber conductive line patterns on surface:
(
a
) lattice type; (
b
) cross type; (
c
) square-frame type; (
d
) double-layer type.
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