Biomedical Engineering Reference
In-Depth Information
Fig. 13 Output voltages (mea-
sured) in tracking mode (TM)
(f PR =
40 MHz). The target
movement rate is 1.25 Hz
Another set of field operational tests has been carried out in order to detect the res-
piratory activity of a subject under test. Two measurement setups have been adopted
as shown in Fig. 14 .
In Fig. 14 a, an adult person is sitting in front of the radar at a distance of 30 cm.
The output of the radar is shown in Fig. 15 a. Note that the output voltage swing is
about 5 mV during the normal respiratory activity and is almost constant when the
person under test stops breathing (i.e., voluntary apnea). A number of additional tests
up to a distance of 45 cm and extensive results can be found in Zito et al. [ 14 ]. Here
it is worth mentioning that tests have been carried out successfully for both genders,
with chest displacements of about 1 cm.
In Fig. 14 b, an infant (asleep) sitting in a car baby seat placed under the radar
sensor at a distance D
30 cm from the chest moving with a displacement of about
2 mm. The output voltage of the radar sensor tracks the respiratory rate profile of the
infant, as reported in Fig. 15 b. Note the presence of a very short apnea of about 3 s,
in which the out voltage remains approximately constant except for small variations
( < 2 mV) due to noise.
=
Fig. 14 Measurement of the respiration rate of: a an adult person placed at 30 cm from the ultra-
wideband (UWB) radar sensor; b a baby in a car seat placed at 30 cm from the UWB radar sensor
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