| ABSTRACT:
A non-acoustic pulse-echo radar monitor is employed in the repetitive
mode, whereby a large number of reflected pulses are averaged to produce
a voltage that modulates an audio oscillator to produce a tone that corresponds
to the heart motion. The antenna used in this monitor generally comprises
two flat copper foils, thus permitting the antenna to be housed in a substantially
flat housing. The monitor converts the detected voltage to an audible signal
with both amplitude modulation and Doppler effect. It further uses a dual
time constant to reduce the effect of gross sensor-to-surface movement.
The monitor detects the movement of one or more internal body parts, such
as the heart, lungs, arteries, and vocal chords, and includes a pulse generator
for simultaneously inputting a sequence of pulses to a transmit path and
a gating path. The pulses transmitted along the transmit path drive an
impulse generator and provide corresponding transmit pulses that are applied
to a transmit antenna. The gating path includes a range delay generator
which generates timed gating pulses. The timed gating pulses cause the
receive path to selectively conduct pulses reflected from the body parts
and received by a receive antenna. The monitor output potential can be
separated into a cardiac output indicative of the physical movement of
the heart, and a pulmonary output indicative of the physical movement of
the lung. |