Biomedical Engineering Reference
In-Depth Information
CHAPTER FIVE
EM Wave Absorbers
Protecting Biological and
Medical Environment
Recently, EM environments have become very complex because of the wide
and rapid spread of many kinds of electric or electronic devices, as exempli-
fied by recent cellular telephone progress. As a result, EM wave interference
problems due to these devices have increased in frequency. Also, biological
effects based on these kinds of EM wave radiation have been feared. As a
countermeasure for protecting biological and medical environment as well as
the measurement involved, knowledge of EM wave absorbers has become
important. In this chapter, we study materials for EM wave absorbers, theory,
and application.
5.1
FOUNDATION OF EM WAVE ABSORBERS
The start of the research on EM wave absorbers dates back to the mid-1930s.
The first wave absorber was due to research in the 2-GHz band in Naamlooze
Vennootschap Machinerieen in the Netherlands [1]. The wave absorber
reported in 1945 was for military purpose [2]. It was used for protecting the
periscope and snorkel of a submarine from search by radar. It consists of the
structure that piled up “Wesch material,” which is comprised of composite
rubber and carbonyl iron, a resistance sheet, and plastic. This absorber has
been called a “Jauman absorber.” In the project organized by O. Halpen at the
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