This paper presents the design and implementation of
a Filtering block for a Bio-Signal Processor. The aim of the Biosignal
Processor design is to implement a portable blood oxygen
analyzer which is capable of measuring the partial pressure of
Oxygen in blood. The filtering block consists of a reconfigurable
FIR filter and a running average IIR filter. The reconfigurability
of the FIR filter is dependent on the magnitude of the light sensor
diode’s current and is implemented with a feed forward loop
from the ADC output as shown in figure 1. A relation between
the output of the diode and the noise in the signal is proven in this
paper. The IIR filter is used in the Bio-Signal Processor to
calculate the average value of signals coming from the FIR filter.
The key design constraints are accuracy to compete with the
traditional blood gas analyzer and power consumption to make
the whole device portable. The filter design is implemented in
hardware using the 0.35 micron technology file from
Austriamicrosystems and synthesized using the Encounter tool
from Cadence Design Systems. The arithmetic and delay units of
the filter have been implemented using a novel 16-bit floating
point technique.