Biomedical Engineering Reference
In-Depth Information
Figure 9.5. Implantable devices with WIBI.
in a regular transformer, two coils are coupled using an iron core, which signif-
icantly reduces the magnetic leakage and increases the coupling coefficient
k to nearly 1. In the WIBI system, k is typically less than 0.05. We must
design a converting circuit sensitive enough to pick up the low induced voltage
in the implanted coil. Data transmission is overlaid on the continuous power
transmission. Two directions of communication are named as download (from
the base station to the WIBI) and upload (from the WIBI to the base station).
Download transmission utilizes amplitude modulate with 100% modulate rate.
The base station shuts the current in the base station coil shortly to send a
pulse, and a series of pulses carries the data. Since the WIBI has limited power,
the upload transmission uses a “reflecting” phenomenon. The WIBI shorts the
implanted coil promptly to generate a current pulse, and this pulse is received
by the base station coil.
The WIBI System Architecture
The purpose of developing the WIBI system is to support various applications
with different requirements. The flexibility of WIBI is one of the important
design targets. Table 9.1 lists the requirement of the WIBI design.
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