U.S. patent application number 12/388264 was filed with the patent office on 2009-08-20 for pulsed ultra-wideband sensor and the method thereof.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to MAKSIM VLADIMIROVICH FESENKO, IGOR YAKOVLEVICH IMMOREEV, TEH HO TAO.
Application Number | 20090209850 12/388264 |
Document ID | / |
Family ID | 40552082 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090209850 |
Kind Code |
A1 |
TAO; TEH HO ; et
al. |
August 20, 2009 |
PULSED ULTRA-WIDEBAND SENSOR AND THE METHOD THEREOF
Abstract
A pulsed ultra-wideband sensor comprises a control unit designed
for forming a time delay of a synchronizing pulse, a probing signal
forming path, a transmitting antenna, a receiving antenna, a path
of a probing signal transmitter, with an output of said path being
connected to the transmitting antenna, a path of a return signal
receiver, with an input of the path being connected to the
receiving antenna, and a first electronic switch. The input of the
first electronic switch is connected to the output of the path for
forming a probing signal, and its outputs--to the input of the path
of the probing signal transmitter and to the path of a return
signal receiver. The outputs of the channels for processing a
return signal, which are parts of the path of the return signal
receiver, are connected to the path for calculating a respiratory
rate and a heart rate.
Inventors: |
TAO; TEH HO; (HSINCHU CITY,
TW) ; IMMOREEV; IGOR YAKOVLEVICH; (MOSCOW, RU)
; FESENKO; MAKSIM VLADIMIROVICH; (MOSCOW, RU) |
Correspondence
Address: |
WPAT, PC;INTELLECTUAL PROPERTY ATTORNEYS
2030 MAIN STREET, SUITE 1300
IRVINE
CA
92614
US
|
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
HSINCHU
TW
|
Family ID: |
40552082 |
Appl. No.: |
12/388264 |
Filed: |
February 18, 2009 |
Current U.S.
Class: |
600/425 |
Current CPC
Class: |
A61B 5/0507 20130101;
G01S 7/415 20130101; A61B 5/024 20130101; G01S 13/0209 20130101;
A61B 5/08 20130101; G01S 13/56 20130101 |
Class at
Publication: |
600/425 |
International
Class: |
A61B 6/00 20060101
A61B006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2008 |
RU |
RU2008106039 |
Claims
1. A pulsed ultra-wideband sensor, comprising a control unit (1)
designed for forming a time delay of a synchronizing pulse, a
probing signal forming path including a coherent radio pulse
generator (2) connected to said control unit (1), a transmitting
and receiving antennas (3 and 4), a path of a probing signal
transmitter, whose output is connected to the transmitting antenna
(3), a path of a return signal receiver, comprising two channels
for processing a return signal, each of said channels comprising a
signal mixer (13 and 18) whose first input is connected to the
receiving antenna (4), and a phase-shifting circuit (12) with an
input of the phase-shifting circuit (12) connected to an output of
the probing signal forming path and an output of the phase-shifting
circuit (12) connected to a second input of the signal mixer (18)
of the second channel for processing a return signal, is
characterized in that the said sensor additionally comprises a
first electronic switch (5) and a respiratory rate and heart rate
calculating path including two frequency filters (28 and 29), two
adders (30 and 31), two blocks (32 and 33) for calculating a signal
amplitude, two blocks (34 and 35) for calculating a signal energy,
two integrators (36 and 37), two comparators (38 and 39), two
signal multiplying blocks (40 and 41), two blocks (42 and 43) for
generating a reference signal, second and third electronic switches
(44 and 45), a respiratory rate calculating block (46) and a heart
rate calculating block (47), the input of the first electronic
switch (5) being connected to the output of the probing signal
forming path, the first output of the first electronic switch (5)
being connected to the input of path of the probing signal
transmitter and the second output of the first electronic switch
(5) being connected to the second input of the signal mixer (13) of
the first channel for processing a return signal and to the input
of the phase-shifting circuit (12), the control input of the first
electronic switch (5) being connected to the control unit (1), the
inputs of the first and second frequency filters (28 and 29) being
connected respectively to the outputs of the first and second
channels for processing a return signal, the first input of the
first adder (30) being connected to the output of the first channel
for processing a return signal, the second input of the first adder
(30) being connected to the output of the first frequency filter
(28), the first input of the second adder (31) being connected to
the output of the second channel for processing a return signal,
the second input of the second adder (31) being connected to the
output of the second frequency filter (29), the first input of the
first signal multiplying block (40) being connected to the output
of the first adder (30), the second input of the first signal
multiplying block (40) being connected to the output of the first
block (42) for generating a reference signal, the first input of
the second signal multiplying block (41) is connected to the output
of the second adder (31), the second input of the second signal
multiplying block (41) is connected to the output of the second
block (43) for generating a reference signal, the input of the
first integrator (36) is connected to the output of the first
signal multiplying block (40), the output of the first integrator
(36) is connected to the first input of the second electronic
switch (44) and to the input of the first block (34) for
calculating a signal energy, the input of the second integrator
(37) is connected to the output of the second signal multiplying
block (41), the output of the second integrator (37) is connected
to the second input of the second electronic switch (44) and to the
input of the second block (35) for calculating a signal energy, the
output of the first block (34) for calculating a signal energy is
connected to the first input of the first comparator (38), the
output of the second block (35) for calculating a signal energy is
connected to the second input of the first comparator (38), the
output of the first comparator (38) is connected to the control
input of the second electronic switch (44), the input of the first
block (32) for calculating a signal amplitude is connected to the
output of the first frequency filter (28), the output of the first
block (32) for calculating signal amplitude is connected to the
first input of the second comparator (39), the input of the second
block (33) for calculating a signal amplitude is connected to the
output of the second frequency filter (29), the output of the
second block (33) for calculating a signal amplitude is connected
to the second input of the second comparator (39), the output of
the second comparator (39) is connected to the control input of the
third electronic switch (45), whose first input is connected to the
output of the first frequency filter (28) and its second input--to
the output of the second frequency filter (29), the output of the
third electronic switch (45) is connected to the input of the
respiratory rate calculating block (46), the output of the second
electronic switch (44) is connected to the input of the heart rate
calculating block (47).
2. The sensor according to the claim 1, is characterized in that it
comprises a data displaying block (48), with a first input of said
block (48) being connected to the output of the heart rate
calculating block (47) and a second input of said block (48) being
connected to the output of the respiratory rate calculating block
(46).
3. The sensor according to the claim 1, is characterized in that
the blocks (42 and 43) for generating a reference signal provided
with inputs, the input of the first block (42) for generating a
reference signal being connected to the output of the first adder
(30) and the input of the second block (43) for generating a
reference signal being connected to the output of the second adder
(31).
4. The sensor according to the claim 1 is characterized in that the
blocks (42 and 43) for generating a reference signal are designed
for forming a reference signal of constant shape.
5. The sensor according to the claim 1 is characterized in that the
probing signal forming path comprises a buffer amplifier (6) and a
band pass filter (5), which are connected in series with the
coherent radio pulse generator (2), with the output of said filter
being connected to the input of the first electronic switch
(5).
6. The sensor according to the claim 1 is characterized in that the
output of the signal mixer (13 and 18) of each channel for
processing a return signal is connected to the path for calculating
a respiratory rate and a heart rate through the band pass filter
(14 and 19), the low-frequency amplifier (15 and 20) and the
low-frequency filter (16 and 21), which are connected in series to
each other.
7. The sensor according to the claim 1 is characterized in that the
path of the return signal receiver includes a band pass filter (10)
and a signal amplifier (11), which are connected in series to the
receiving antenna (4), with the output of said signal amplifier
being switched to the channels for processing a return signal.
8. The sensor according to the claim 1 is characterized in that the
path of the probing signal transmitter comprises a band pass filter
(8) and a signal amplifier (9) which are connected in series to the
transmitting antenna (3), with the input of said signal amplifier
being connected to the first output of the first electronic switch
(5).
9. The sensor according to the claim 1 is characterized in that the
control unit (1) designed for forming a time delay of a
synchronizing pulse comprises a driving generator (23), to which
are connected in parallel a path for forming a synchronizing signal
of the transmitter, the said path comprising a first short-pulse
former (24), and a path for forming a synchronizing signal of the
receiver, the said path comprising a controlled digital delay line
(25) and a second short-pulse former (26) with an output forming a
first output of the control unit (1), the said output being
connected to the control input of the first electronic switch (5),
and an "OR" circuit (27), the inputs of the said circuit being
connected to the outputs of the path for forming a synchronizing
signal of the transmitter and the path for forming a synchronizing
signal of the receiver, with the output of the "OR" circuit (27)
forming a second output of the control unit (1), the said output
being connected to the coherent radio pulse generator (2).
10. A pulsed ultra-wideband sensor comprising a processing circuit,
the processing circuit comprising: a first frequency filter
configured to receive an in-phase signal; a second frequency filter
configured to receive a quadrature signal; a first signal amplitude
calculating unit configured to calculate an signal amplitude of an
output signal of the first frequency filter; a second signal
amplitude calculating unit configured to calculate an signal
amplitude of an output signal of the second frequency filter; a
first electronic switch configured to output one of the output
signals of the first and the second frequency filters according to
calculated results of the first and the second signal amplitude
calculating units; a first adder configured to subtract the output
signal of the first frequency filter from an input signal of the
first frequency filter; a second adder configured to subtract the
output signal of the second frequency filter from an input signal
of the second frequency filter; a first signal integrating unit
configured to calculate correlation integrals of output signals of
the first adder and a first reference signal; a second signal
integrating unit configured to calculate correlation integrals of
output signals of the second adder and a second reference signal; a
first signal energy calculating unit configured to calculate signal
energy of an output signal of the first signal integrating unit; a
second signal energy calculating unit configured to calculate
signal energy of an output signal of the second signal integrating
unit; and a second electronic switch configured to output one of
the output signals of the first and the second signal integrating
units according to calculated results of the first and the second
signal energy calculating units.
11. The pulsed ultra-wideband sensor of claim 10, wherein the first
reference signal exhibits a constant shape.
12. The pulsed ultra-wideband sensor of claim 10, wherein the first
reference signal is generated according to the output signal of the
first adder.
13. The pulsed ultra-wideband sensor of claim 10, wherein the
second reference signal exhibits a constant shape.
14. The pulsed ultra-wideband sensor of claim 10, wherein the
second reference signal is generated according to the output signal
of the second adder.
15. The pulsed ultra-wideband sensor of claim 10, wherein the first
signal integrating unit comprises: a first signal multiplying block
configured to multiply the output signal of the first adder by the
first reference signal; and a first integrator configured to
calculate an integral of an output signal of the first signal
multiplying block.
16. The pulsed ultra-wideband sensor of claim 10, wherein the
second signal integrating unit comprises: a second signal
multiplying block configured to multiply the output signal of the
second adder by the second reference signal; and a second
integrator configured to calculate the integral of an output signal
of the second signal multiplying block.
17. The pulsed ultra-wideband sensor of claim 10, wherein the
processing unit further comprises a first comparator configured to
compare the calculated results of the first and the second signal
amplitude calculating units and to control the first electronic
switch.
18. The pulsed ultra-wideband sensor of claim 10, wherein the
processing unit further comprises a second comparator configured to
compare the calculated results of the first and the second signal
energy calculating units and to control the second electronic
switch.
19. The pulsed ultra-wideband sensor of claim 10, wherein the
processing unit further comprises a first reference signal
generating block for generating the first reference signal.
20. The pulsed ultra-wideband sensor of claim 10, wherein the
processing unit further comprises a second reference signal
generating block for generating the second reference signal.
21. A method for measuring physiological parameters, comprising:
filtering a first information signal and a second information
signal indicative of both a first physiological parameter and a
second physiological parameter to generate a first filtered signal
and a second filtered signal indicative of merely the first
physiological parameter; summing the first information signal and
the first filtered signal to generate a first summed signal
indicative of merely the second physiological parameter; summing
the second information signal and the second filtered signal to
generate a second summed signal indicative of merely the second
physiological parameter; correlating the first summed signal with a
first reference signal to generate a first correlated signal;
correlating the second summed signal with a second reference signal
to generate a second correlated signal; selecting a first
physiological parameter signal from the first filtered signal and
the second filtered signal based on the amplitude of the first
filtered signal and the second filtered signal; and selecting a
second physiological parameter signal from the first correlated
signal and the second correlated signal based on the energy of the
first filtered signal and the second filtered signal.
22. The method of claim 21, wherein the first information signal
exhibits a 90-degree phase difference from the second information
signal.
23. The method of claim 21, wherein the correlation of the first
summed signal and the first reference signal is accomplished by
integrating a product of the first summed signal multiplied by the
first reference signal.
24. The method of claim 21, wherein the correlation of the second
summed signal and the second reference signal is accomplished by
integrating a product of the second summed signal multiplied by the
second reference signal.
25. The method of claim 21, further comprising: determining a first
physiological parameter according to local extremes of the first
physiological parameter signal.
26. The method of claim 21, further comprising: determining a
second physiological parameter according to local extremes of the
second physiological parameter signal.
27. The method of claim 21, wherein the first physiological
parameter is a respiratory rate.
28. The method of claim 21, wherein the second physiological
parameter is a heart rate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to the medicinal diagnostic
instruments for monitoring individual's physiological parameters,
in particular, radar aids for diagnosis of individual's
physiological parameters under stationary and field conditions.
[0003] 2. Description of the Related Art
[0004] The employment of an ultra-wideband radar as measuring means
allows a number of problems to be settled, which may not be
realized using traditional diagnostics means. The ultra-wideband
sensors allow noninvasive measurements to be taken to thereby avoid
the probability of infecting a patient during measurements. In
addition, there is no necessity in employing specially furnished
laboratories and high-skilled personnel.
[0005] The ultra-wideband sensors provide for contact-free
diagnosis allowing patients having vast burns or skin diseases to
be treated in the absence of the possibility of using contact
diagnosis means. With the employment of such sensors, a patient may
be investigated through clothing to thereby reduce diagnosis
time.
[0006] The employment of ultra-wideband sensors provides the
desired safety for a patient thanks to the low-level energy of an
electromagnetic signal emitted. The radiation load induced to a
patient is minimized by orders of magnitude in comparison with
X-ray computed tomography.
[0007] Moreover, there is no necessity in thorough disinfecting of
a measurement instrument and also there is no need in utilizing
disposable elements of an apparatus and consumable materials. As a
consequence, total expenses for maintaining diagnostic technique
are significantly reduced.
[0008] According to the classification used nowadays, to the
ultra-wideband radar systems may be referred radars with a signal
band width determined from the following condition:
0.25<(f.sub.upper-f.sub.lower)/(f.sub.upper+f.sub.lower)<1,
where f.sub.upper and f.sub.lower are respectively upper and lower
boundaries of a signal band width (see, for example, I. Ya.
Immoreev. Ultra-wideband radars: new possibilities, unique
problems, the features of system. Journal of Bauman's MGTU, Series
"Instrument making", Number 4, 1998; I. Ya. Immoreev. The
possibilities and features of ultra-wideband radio systems. Applied
electronics, Kharkov, vol. 1, No 2, 2002, pages 122 to 140). In
addition, the signal bandwidth (f.sub.upper-f.sub.lower) of
ultra-wideband radar measurement systems should be at least 500 MHz
(see Federal Communications Commission FCC 02-48. Washington, D.C.
20554. ET Dockets 98-153. First Report and Order. Apr. 22, 2002).
The employment of ultra-wideband radar measurement aids allows the
signal information content to be widened owing to an increased
distance resolution of the sensor.
[0009] Various circuit designs of pulsed ultra-wideband sensors
known nowadays are adapted for monitoring the functioning of
patient's respiratory organs and a cardio-vascular system. For
example, the U.S. Pat. No. 5,519,400 (issued on May 21, 1996)
describes a pulsed ultra-wideband sensor with phase-code modulation
for controlling the movement of a subject under study. Short video
pulses are used as a reference signal and an excitation signal for
a transmitting antenna of an apparatus. The apparatus has a signal
transmitter with a transmitting antenna sending out an
ultra-wideband signal at a frequency of from 2 GHz to 10 GHz. A
time delay block generates a control signal determining a time
delay between a series of pulse signals. A receiver with a
receiving antenna receives discrete signals in accordance with a
gating signal of the time delay block. A gating signal delays the
receiving of a sent-out pulse signal for a time interval equal to
the total time during which the sent-out signal reaches the subject
under study and a return signal reaches the receiving antenna. The
time delay depends on the distance between the sensor and the
subject under study.
[0010] A required delay of a probing signal pulses and pulses of a
signal to be received is provided by the time delay block. The
signals are modulated by means of this block. The modulating signal
is encoded in order to avoid the interference of the adjacent radar
sensors. The signal receiver comprises a synchronization block for
synchronizing with a modulating signal and two quadrature channels
for processing a return signal. One of the quadrature channels
operates in phase with a reference signal, and in the other channel
a signal is generated with a 90.degree. phase shift relative to the
reference signal. Data produced from outputs of the quadrature
channels of the receiver is used for subsequent analysis of the
signals. The quadrature channels are alternately changed-over upon
receiving of a return signal by means of a high-speed controllable
change-over mechanism. Each of the quadrature channels is equipped
with an individual filter and a signal amplifier.
[0011] During operation of the prior art radar sensor, the
probability of simultaneous processing of the signals delivered to
the quadrature channels is excluded. Utilization of a
single-channel pattern of processing a return electromagnetic
signal in the sensor eliminates the probability of simultaneous
processing of the signals in the two quadrature channels in order
to neutralize distortions in the received signal.
[0012] In turn, the impossibility of joint processing of the
signals does not allow data on physiological parameters of the
subject under study to be obtained with a desired extent of
accuracy at any point on a working distance under measurement
process. In this case the so-called "blind" zones occur at the
working distance between the sensor and the subject under study,
wherein the phase sensitivity of the sensor is significantly
decremented in said zones, though the amplitude of the probing
signals reflected from the subject may be sufficiently high. The
quantity of such zones and the gaps between them depend on an
extent of distance under measurement of the radar sensor and a
length of oscillation waves filling the probing signal.
[0013] The presence of the "blind" zones and the restricted working
distance of measurements of the sensor, with the extent of said
distance depending on duration of the probing signals, results in
degrading the measurement accuracy of patient's physiological
parameters at predetermined points of measurement distance. This
imposes essential restrictions on the field of application of the
pulsed ultra-wideband sensor. Such a sensor may be used only in
case of full immobility of a patient and a fixed distance between
the sensor and the patient. Any changing in the position of the
patient needs distance retuning of the sensor. In certain cases the
position of the sensor relative to the subject under study should
be adjusted in order to avoid the occurrence of the patient in the
"blind" zone at the measurement distance.
[0014] Automatic distance retuning of the sensor is provided
through the usage of an automatic distance tracking system which
significantly complicates the design of the instrument. However,
even the application of the expensive automatic distance tracking
system does not eliminate the possibility of occurrence of the
subject under study in the "blind" zone.
[0015] Another prior art pulsed ultra-wideband sensor used for
monitoring the patient's physiological parameters is described in
the USA published patent application No. 2004/0249258 (issued on
Dec. 9, 2004). The instrument is a pulsed ultra-wideband low-power
radar with a receiving-transmitting antenna. Short video pulses are
used as a reference probing signal. The apparatus comprises a
constant-frequency pulse generator, a transmitter, a receiver, a
delayed signals generating block, an analog-to-digital signal
converter, a signal processing block, a data displaying block, and
a control and synchronization block. The signal processing block
provides for an expanded statistic processing of return signals.
The return signal energy is enhanced by stepped amplification of
the signal amplitude in the receiver before the signal is converted
to a digital code.
[0016] However the given sensor is characterized by the
impossibility of avoiding the occurrence of spatial zones where the
information content of the return signal is reduced. Moreover, the
sensor does not provide for simultaneous generation of reliable
data on physiological parameters of patient's various organs.
[0017] It is known from the U.S. Pat. No. 5,573,012 (issued on Nov.
12, 1996) a pulsed radar instrument for monitoring various
physiological parameters including the parameters of patient's
cardio-vascular system and respiratory organs. Functioning of the
instrument is based on processing of the signals reflected from the
subject under study and generation of a voltage-averaged signal
used for modulating a signal of the audio-frequency generator. The
signal converter converts the measured voltage of the return signal
to an amplitude-frequency modulated audio signal. The apparatus
comprises a pulse generator, which generates pulses for opening an
input circuit of a signal receiver, and an accumulator for
accumulating the receiver input circuit signals.
[0018] The received signal may be processed by frequency filtration
and amplification for controlling various parameters. However, the
signal processing circuit does not rule out the possibility of
occurrence of the "blind" zones at the distance between the subject
under test and the sensor. Also, the given sensor is not of
ultra-wideband type sensors since the frequency of a driving
generator is 1 MHz with the signal bandwidth not greater than 0.1
MHz. The return signal is measured and processed in the given
sensor using the Doppler effect. Hereupon the sensor does not
provide for desired information content of the signal that is
intrinsic in the ultra-wideband sensors.
[0019] The closest prior art to the claimed invention is a pulsed
ultra-wideband sensor for monitoring the parameters of patient's
cardio-vascular system and respiratory organs, which is described
in the U.S. Pat. No. 4,085,740 (issued on Apr. 25, 1978). The
sensor comprises a generator which generates electromagnetic
oscillations with a frequency of 10 GHz. The generated signal is
modulated with the use of a modulation block. The modulated signal
is delivered to a transmitter and is then transferred by means of a
transmitting antenna toward the subject under study.
[0020] The probing signal reflected from the subject is perceived
by a receiving antenna of the sensor and is then branched in two
channels of the receiver input circuit. At the same time a probing
reference signal is sent out to an attenuator whose output signal
is also branched in two channels. The first in-phase reference
signal is delivered to a mixer of the first channel of the
receiver, and the second reference signal is delivered to a
phase-shifting circuit for acquiring a phase shift by an angle of
90.degree.. The output of the phase-shifting circuit is connected
to a second input of the mixer of the second channel of the
receiver.
[0021] The receiver of the sensor has two quadrature channels for
processing a return signal. Each of said channels has a signal
mixer whose output is connected in series to a detector adapted for
signal demodulation. The signal is then supplied to a signal
amplifier and a filter. During monitoring of patient's
physiological parameters, sine-shaped signals are formed at mixer
outputs in the quadrature channels. Upon demodulation of a
composite signal of two phase-shifted sinusoids, a signal amplitude
is defined which is a function of a relative angular phase turning
speed of the two signals fed to the mixer input. The magnitude of a
relative phase of the return signal in each of the channels
describes the frequency of movement of patient's chest or a heart
rate depending on tuning of the filters and amplifiers in the
signal processing channels.
[0022] The first quadrature channel of the receiver is designed for
separating a signal indicative of frequency of the chest cyclic
motions, and the second quadrature channel is designed for
separating the signal indicative of a heart rate. The respective
signals are defined using amplifiers and frequency filters tuned
for respective amplitude and frequency of patient's physiological
parameter under control.
[0023] The quadrature channels for processing the return signal in
the prior art sensor are of a concrete functional designation. Each
of said channels is used for monitoring a certain physiological
parameter: a heart rate or a respiratory rate. Due to that, the
prior art instrument is characterized by the similar features, as
it is with the above instruments, namely: the output signal of the
sensor has low information content owing to the presence of "blind"
zones at portions of a working measurement distance (in the space
between the subject under test and the sensor); the field of
application of the sensor is limited due to the necessity of fixing
the distance between the sensor and the patient; the sensor may not
be used even on a slight movement of the subject under study.
[0024] The reduced information content of the return signal results
from the processes occurring during diagnosis. The signal carrying
useful information is measured in the ultra-wideband sensor by
determining the phase difference between the probing reference
signal and the signal reflected from the subject under study.
Movement of the patient's chest causes changes in the phase
incursion of the signal reflected from the subject under test.
[0025] The movement of the chest is of reciprocation nature with a
low amplitude. The maximum chest movement amplitude indicative of
normal respiration is 5 mm, whereas the heart beating amplitude is
from 0.2 mm to 2 mm. So, the oscillation frequency of a probing
signal must be sufficiently high, from 3 GHz to 20 GHz, in order to
enable the desired accuracy in measurements of patient's
physiological parameters.
[0026] Traditional signal processing patterns characteristic of the
above prior art sensors use a correlation system for processing a
return signal. The operation of such systems is based on
multiplying of a probing signal and a return signal delayed for a
time interval during which the signal propagates to the subject
under test and comes back to the receiving antenna. Short video
pulses with a duration not in the excess of a period of
oscillations filling the probing pulse are commonly used as a
probing signal. The output signal of the correlation system for
processing a return signal is proportional to the phase difference
between the probing signal and the return signal.
[0027] In case the subject under test is immobile, the amplitude Z
of the output signal after processing is determined in compliance
with the following correlation:
Z = E 0 E 1 2 nT 0 cos ( .PHI. ) , ( 1 ) ##EQU00001##
[0028] where E.sub.0 is a maximum amplitude of the probing
signal;
[0029] E.sub.1 is a maximum amplitude of the return signal;
[0030] T.sub.0 is a period of oscillations of the probing
signal;
[0031] n is a whole number of periods of oscillations filling the
probing pulse.
[0032] The magnitude of phase difference .phi. in the expression
(1) is determined by the time during which electromagnetic waves
propagate to the subject under test and come back:
.PHI. = .omega. 0 2 R 1 C = 4 .pi. R 1 .lamda. , ( 2 )
##EQU00002##
[0033] where .omega..sub.0=2.sup..pi.f.sup.0--is a circular
frequency of the probing signal;
[0034] f.sub.0--is an average frequency of the probing signal
spectrum;
[0035] C--is an electromagnetic wave propagation speed;
[0036] .lamda.--is a wavelength of oscillations filling the probing
signal;
[0037] R.sub.1--a distance between the subject under test and the
sensor. 7
[0038] The normalized chart Z(R.sub.1)T.sub.0 of function of
amplitude of an output signal generated by the correlation system
for processing a return signal depending on the distance to the
subject under test is illustrated in FIG. 1 of the accompanying
drawings. As seen from the represented graphical dependence, there
are "blind" zones at a working distance between the sensor and the
subject under test, wherein the output signal of the sensor is
equal to or approximates a zero value. The presence of such zones
does not depend on the reflective capacity (an effective scattering
area) of the subject under test. The distance between the
boundaries of the "blind" zones is proportional to
.lamda./4=T.sub.0C/4 and depends on the probing signal oscillation
period.
[0039] The number N of such "blind" zones is in reverse proportion
to the period T.sub.0 of oscillations of the probing signal or the
wavelength .lamda. of the probing signal:
N = 4 R 1 T 0 C = 4 R 1 .lamda. . ##EQU00003##
The lower is the period (the higher the frequency), the greater
number of such zones are created at the working distance of
measurement.
[0040] In particular, with an average frequency of the probing
signal spectrum of 6 GHz at the working distance of 2 m, there will
be 160 of such zones, and the distance between the "blind" zone
boundaries will be 12.5 mm. It is, therefore, quite probable that
during measuring of a respiratory rate and a heart rate, the
patient's chest surface which reflects the probing signals will
occur within one of the "blind" zones.
[0041] In case the subject under test is within the region of the
"blind" zone with an amplitude of movement of the subject being
lower than a quarter of the oscillation wavelength of the probing
signal, measurements of parameters of subject's movement will be
extremely difficult. The indicated circumstances cause an adverse
effect upon accuracy of measurement results, which is intolerable
in carrying diagnosis of a patient.
[0042] With high amplitudes of subject's reciprocating movements,
for example, with patient's deep breath, and high average
frequencies of the probing signal spectrum, the shape of the output
signal of the correlation system is substantially distorted as
compared to the actual function characterizing the movement of the
subject under study. It is, therefore, impossible to determine the
patient's respiratory rate and heart rate with a desired
accuracy.
[0043] The amplitude Z(t) of the output signal of a correlation
processing system is described by the following expression:
Z(t)=E.sub.m cos(.phi.(t)+.phi..sub.1), (3)
[0044] where
E m = E 0 E 1 2 nT 0 ##EQU00004##
is a maximum energy of interaction between the return signal and
the probing signal, which is released at an output load with a unit
resistance;
.PHI. 1 = 2 .omega. 0 R 1 c = 4 .pi. .DELTA. R 1 .lamda.
##EQU00005##
is a phase shift depended upon the distance between the subject
under test and the sensor;
.PHI. ( t ) = 2 .omega. 0 .DELTA. Rf ( .OMEGA. t ) C = 4 .pi.
.DELTA. R .lamda. F ( .OMEGA. t ) ##EQU00006##
is an instantaneous phase value resulted from movement of the
subject under test;
[0045] F(.OMEGA.t) is a law of movement of the subject under
test;
[0046] .OMEGA.=2.pi.f is a circular frequency of reciprocation of
the subject under test;
[0047] f is a frequency of reciprocation of the subject under
test;
[0048] t is a current time;
[0049] .DELTA.R is a maximum amplitude of movement of the subject
under test.
[0050] Suppose the subject under study is at a distance R.sub.1
from the sensor and is movable in accordance with a sinusoidal law
at a circular frequency .OMEGA. and amplitude .DELTA.R. Such
expression
[0051] (3) for the output signal will assume the following
form:
Z ( t ) = E m cos ( 4 .pi. .DELTA. R .lamda. sin ( .OMEGA. t ) + 4
.pi. R 1 .lamda. ) , ( 4 ) ##EQU00007##
[0052] Oscillograms of the output signal (changing in the amplitude
Z(t) and the amplitude-and-frequency spectrum Z(f1) of the output
signal) of the correlation system are illustrated in FIGS. 2 to 9
on the accompanying drawings. The changed amplitude Z(t) of the
signal in the represented charts has only a variable component. The
cited curves refer to the various values m (m=0.5 in FIGS. 2 and 3;
m=2 in FIGS. 4 and 5; m=5 in FIGS. 6 and 7; m=10 in FIGS. 8 and 9),
said values being determined in compliance with the ratio:
m = 4 .pi. .DELTA. R .pi. . ##EQU00008##
The curves show the nature of changing in the output signal with
varying values .DELTA.R of the oscillations amplitude of the
subject under study and respective values m. The measured
oscillation frequency of the subject under test was 1 Hz. The value
f1 in the charts is the frequency of the signal reflected from the
subject under test.
[0053] It follows from the curves that the shape of the output
signal essentially differs from the real law of movement of the
subject with greater values .DELTA.R in comparison with the
wavelength .lamda.. With .DELTA.R>.lamda. (see FIGS. 4 to 9,
m=2, 5 and 10), the function of changing the amplitude and movement
speed of the subject under study becomes difficult to be determined
in case a single-channel signal processing circuit is used.
[0054] With low values of oscillations amplitude .DELTA.R of the
subject under study in comparison with the wavelength .lamda.
(.DELTA.R<.lamda.), the output signal of the quadrature channel
may have variable as well as constant components. It should be
noted that the constant component of the return signal contains
useful information on immobile subjects, the subject under test
also being among said immobile subjects. In the prior art
apparatuses such constant signal components are removed by filters
in each channel for processing a return signal before the
subsequent programmed processing of the signal. Therefore, useful
information needed for enabling an accurate determination of
physiological parameters is loosed.
[0055] A special programmed signal calibration for the immovable
subject under test is used for the purpose of recovering the
information on movement of the subject under study, said
information being contained in the constant component of the return
signal. In case the position of the subject under study is changed,
the signal calibration procedure should be repeated. This leads to
prolonged measurements and complicated software and design of the
sensor.
SUMMARY OF THE INVENTION
[0056] The claimed invention is targeted at elimination of the
above intrinsic in the prior art apparatuses and including the
impossibility of simultaneous processing of the signal reflected
from the subject under study in the two processing channels and
separation of a maximum information-saturated part of the return
signal for further processing and determining the patient's heart
rate, respiratory rate or other physiological parameters at a
desired accuracy.
[0057] The claimed invention provides a novel technical result to
resolve the given technical problem, the technical result includes
an increase in the phase sensitivity of the sensor and a precise
determination of a heart rate, a respiratory rate or other
physiological parameters upon movement of the patient within a
range of working distances of measurements.
[0058] The achievement of the given technical result is provided
through the usage of a pulsed ultra-wideband sensor. The sensor
comprises a control unit adapted for forming a time delay of
synchronizing pulse, a probing signal forming path including a
coherent radio pulse generator connected to the control unit, a
transmitting antenna, a receiving antenna, a probing signal
transmitter path, whose output is connected to the transmitting
antenna, and a return signal receiver path comprising two
quadrature channels for processing of a return signal. Each of said
channels comprises a signal mixer having a first input connected to
the receiving antenna, and a phase-shifting circuit whose input is
connected to an output of the probing signal forming path. The
output of the phase-shifting circuit is connected to a second input
of the signal mixer of the second channel for processing a return
signal.
[0059] The sensor implemented according to the given invention
comprises a first electronic switch and a respiratory rate and a
heart rate calculating path including two frequency filters, two
adders, two signal amplitude calculating blocks, two signal energy
calculating blocks, two integrators, two comparators, two signal
multiplying blocks, two block for generating reference signals, a
second electronic switch and a third electronic switch, a
respiratory rate calculating block, and a heart rate calculating
block.
[0060] The input of the first electronic switch is connected to the
output of the probing signal forming path. The first output of the
first electronic switch is connected to the input of the path of
the probing signal transmitter. The second output of the first
electronic switch is connected to the second input of the signal
mixer of the first channel for processing a return signal and to
the input of the phase-shifting circuit. The control input of the
first electronic switch is connected to the control unit.
[0061] The inputs of the first and second frequency filters are
connected respectively to the outputs of the first and second
channels for processing a return signal. The first input of the
first adder is connected to the output of the first channel for
processing a return signal. The second input of the first adder is
connected to the output of the first frequency filter. The first
input of the second adder is connected to the output of the second
channel for processing a return signal. The second input of the
second adder is connected to the output of the second frequency
filter.
[0062] The first input of the first signal multiplying block is
connected to the output of the first adder. The second input of the
first signal multiplying block is connected to the output of the
first block for generating a reference signal. The first input of
the second signal multiplying block is connected to the output of
the second adder. The second input of the second signal multiplying
block is connected to the output of the second block for generating
a reference signal.
[0063] The input of the first integrator is connected to the output
of the first signal multiplying block. The output of the first
integrator is connected to the first input of the second electronic
switch and to the input of the first signal energy calculating
block. The input of the second integrator is connected to the
output of the second signal multiplying block. The output of the
second integrator is connected to the second input of the second
electronic switch and to the input of the second signal energy
calculating block. The output of the first signal energy
calculating block is connected to the first input of the first
comparator. The output of the second signal energy calculating
block is connected to the second input of the first comparator. The
output of the first comparator is connected to the control input of
the second electronic switch.
[0064] The input of the first signal amplitude calculating block is
connected to the output of the first frequency filter. The output
of first signal amplitude calculating block is connected to the
first input of the second comparator. The input of the second
signal amplitude calculating block is connected to the output of
the second frequency filter. The output of the second signal
amplitude calculating block is connected to the second input of the
second comparator. The output of the second comparator is connected
to the control input of the third electronic switch, whose first
input is connected to the output of the first frequency filter and
second input is connected to the output of the second frequency
filter. The output of the third switch is connected to the input of
the respiratory rate calculating block, and the output of the
second electronic switch is connected to the input of the heart
rate calculating block.
[0065] The method for measuring physiological parameters according
to the embodiments of the invention comprises: filtering a first
information signal and a second information signal indicative of
both a first and a second physiological parameters to generate a
first filtered signal and a second filtered signal indicative of
merely a first physiological parameter; summing the first
information signal and the first filtered signal to generate a
first summed signal indicative of merely a second physiological
parameter; summing the second information signal and the second
filtered signal to generate a second summed signal indicative of
merely a second physiological parameter; correlating the first
summed signal with a first reference signal to generate a first
correlated signal; correlating the second summed signal with a
second reference signal to generate a second correlated signal;
selecting a first physiological parameter signal from the first
filtered signal and the second filtered signal based on the
amplitude of the first filtered signal and the second filtered
signal; and selecting a second physiological parameter from the
first correlated signal and the second correlated signal based on
the energy of the first filtered signal and the second filtered
signal.
[0066] The invention is exemplified by the description of concrete
examples of embodiment of the pulsed ultra-wideband sensor designed
for measuring a respiratory rate, a heart rate or other
physiological parameters and the method thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] The accompanying drawings illustrate the following:
[0068] FIG. 1 is a normalized chart
Z(R.sub.1R.sub.1/.lamda.)/T.sub.0 of an output signal of a
correlation processing system depending on a relative distance
R1/.lamda. to the immobile subject under study;
[0069] FIG. 2 is a chart of function Z(t) of an output signal of a
correlation processing system with m=0.5;
[0070] FIG. 3 is an amplitude-frequency spectrum Z(f.sub.1) of an
output signal of a correlation processing system with m=0.5;
[0071] FIG. 4 is a chart of function Z(t) of an output signal of a
correlation processing system with m=2;
[0072] FIG. 5 is an amplitude-frequency spectrum Z(f.sub.1) of an
output signal of a correlation processing system with m=2;
[0073] FIG. 6 is a chart of function Z(t) of an output signal of a
correlation processing system with m=5;
[0074] FIG. 7 is an amplitude-frequency spectrum Z(f.sub.1) of an
output signal of a correlation processing system with m=5;
[0075] FIG. 8 is a chart of function Z(t) of an output signal of a
correlation processing system with m=10;
[0076] FIG. 9 is an amplitude-frequency spectrum Z(f.sub.1) of an
output signal of a correlation processing system with m=10;
[0077] FIG. 10 is a block diagram of a probing signal forming path,
a path of a probing signal transmitter, and a path of a return
signal receiver;
[0078] FIG. 11 is a block diagram of a control unit;
[0079] FIG. 12 is a block diagram of a respiratory rate and a heart
rate calculating path in the first version of embodiment;
[0080] FIG. 13 is a block diagram of a respiratory rate and heart
rate calculating path in the second version of embodiment;
[0081] FIG. 14 is a time diagram U(t) of synchronizing pulses at
the output of a driving generator of a control unit;
[0082] FIG. 15 is a time diagram U(t) of synchronizing pulses at
the output of a delay line of a synchronizing signal forming path
of the receiver;
[0083] FIG. 16 is a time diagram U(t) of synchronizing pulses at
the output of a first short pulse generating element of a
synchronizing signal forming path of the transmitter;
[0084] FIG. 17 is a time diagram U(t) of synchronizing pulses at
the output of a second short pulse generating element of a
synchronizing signal forming path of the receiver;
[0085] FIG. 18 is a time diagram U(t) of synchronizing pulses at
the output of a control unit;
[0086] FIG. 19 is a time diagram U(t) of coherent radio pulses at
the output of a self-contained microwave generator;
[0087] FIG. 20 is a time diagram Z.sub.1(t) of a signal of a first
channel for processing a return signal at the input of a first
frequency filter;
[0088] FIG. 21 is a time diagram Z.sub.1(t) of a signal of a first
channel for processing a return signal at the output of a first
integrator;
[0089] FIG. 22 is a time diagram Z.sub.2(t) of a signal of a second
channel for processing a return signal at the input of a second
frequency filter;
[0090] FIG. 23 is a time diagram Z.sub.2(t) of a signal of a second
channel for processing a return signal at the output of a second
integrator;
[0091] FIG. 24 is a comparative diagram of energy values E(t) of
signals at the output of a first (an upper curve) and a second (a
lower curve) signal energy calculating blocks; and
[0092] FIG. 25 shows a processing circuit according to one
embodiment of the present invention.
EMBODIMENT OF THE PRESENT INVENTION
[0093] The pulsed ultra-wideband sensor comprises a control unit 1
(CU) for forming a time delay for a synchronizing signal, a probing
signal forming path including an externally excited self-contained
microwave generator (SMG) 2 used as a coherent radio pulse
generator (see FIG. 10). The sensor is further provided with a
transmitting antenna 3 and a receiving antenna 4, a path of a
probing signal transmitter, a first electronic switch 5, and a path
of a return signal receiver with two channels for processing a
return signal (see FIG. 10).
[0094] The probing signal forming path comprises a buffer amplifier
6 (BA) and a band pass filter 7 (BFPS) for the probing signal,
which are connected in series with the self-contained microwave
generator 2. The band pass filter 7 is connected to the input of
the first electronic switch 5. The path of the probing signal
transmitter comprises a band pass filter 8 (BFT) of the transmitter
and an amplifier 9 (TA) of the transmitter, which are connected in
series to the transmitting antenna 3, with the input of amplifier
being connected to the first output of the controlled electronic
switch 5 (see FIG. 10).
[0095] The path of the return signal receiver comprises a band pass
filter 10 (BFRS) for the return signal and a low-noise amplifier 11
(LNA), which are connected in series to the receiving antenna 4,
with the output of the low-noise amplifier being connected to the
two parallel switched channels for processing a return signal. The
receiver path also includes a phase-shifting circuit 12 (PSC). The
first channel for processing a return signal comprises a signal
mixer 13 (SM1) to the output of which signal mixer are connected in
series a band pass filter 14 (BF1), a low-frequency amplifier 15
(LFA1), a low-frequency filter 16 (LFF1), and an analog-to-digital
converter 17 (ADC1). The first input of the signal mixer 13 is
connected to the output of the low-noise amplifier 11 while the
second input is connected to the second output of the first
electronic switch 5 (see FIG. 10).
[0096] The second channel for processing a return signal comprises
a signal mixer 18 (SM2) to the output of which mixer are connected
in series a band pass filter 19 (BF2), a low-frequency amplifier 20
(LFA2), a low-frequency filter 21 (LFF2) and an analog-to-digital
converter 22 (ADC2). The first input of the signal mixer 18 is
connected the output of the low-noise amplifier 11 while the second
input is connected to the second output of the first electronic
switch 5 through the phase-shifting circuit 12 providing a phase
shift of a probing signal by an angle of 90.degree.. The
low-frequency filters 16 and 21 with a lower frequency boundary of
about 0.1 Hz provide for selection of the signals under process
with a band pass higher than the indicated "cutoff frequency" (see
FIG. 10).
[0097] The control unit 1 for forming a time delay for a
synchronizing pulse, whose block diagram is shown in FIG. 11,
comprises a driving generator 23 (DG), a path for forming a
synchronizing signal of the transmitter and controlling the process
of forming a probing signal, and a path for forming a synchronizing
signal of the receiver.
[0098] The path for forming a synchronizing signal of the
transmitter comprises a first short-pulse former 24 (SPF1) by means
of which a short video pulse of the synchronizing signal is
generated. The path for forming a synchronizing signal of the
receiver, consisting of a controlled digital delay line 25 (DDL)
and a second short-pulse former 26 (SPF2), defines a first output
of the control unit 1, said output being connected to a control
input of the first electronic switch 5. Both paths for forming
synchronizing signals of the transmitter and the receiver are
connected to the inputs of an "OR" circuit 27 whose output forms a
second output of the control unit 1. This output is connected to
the control input of the self-contained microwave generator 2 (see
FIG. 11).
[0099] The respiratory and heart rates calculating path whose block
diagram is shown in FIGS. 12 and 13 includes two frequency filters
28 and 29 (FF1 and FF2), two adders 30 and 31 (AD1 and AD2), two
blocks 32 and 33 (BCA1 and BCA2) for calculating signal amplitude,
two blocks 34 and 35 (BCE1 and BCE2) for calculating signal energy,
two integrators 36 and 37 (INT1 and INT2), two comparators 38 and
39 (COM1 and COM2), two signal multiplying blocks 40 and 41 (SMB1
and SMB2), two blocks 42 and 43 (GRS1 and GRS2) for generating
reference signals, a second electronic switch 44 and a third
electronic switch 45, a respiratory rate calculating block 46
(BCR), a heart rate calculating block 47 (BCH), and a data
displaying block 48 (DDB).
[0100] The frequency filters 28 and 29 are designed for frequency
selection of the signals defining a movement of a chest and the
signals defining heartbeats. The given signals are contained in a
return signal which is an integral curve of a patient's respiration
and heartbeat function. The frequency filters 28 and 29 have a band
pass providing "smoothing" of the frequencies characteristic of the
heart rate on the integral curve of the return signal. The said
curve includes the frequency characteristics of the chest
oscillations and heart beats. The band pass of the filters 28 and
29 is delimited by an upper "cutoff frequency" of about 1 Hz.
[0101] The input of the first frequency filter 28 is connected to
the output of the first channel for processing a return signal. The
input of the second frequency filter 29 is connected to the output
of the second channel for processing a return signal. In the
example of embodiment of the sensor under consideration the inputs
of the first and second frequency filters 28 and 29 are connected
to the outputs of the analog-to-digital converters 17 and 22,
respectively.
[0102] The first input of the first adder 30 is connected to the
output of the first channel for processing a return signal, with
the output of the analog-to-digital converter 17 serving as an
output of said first channel. The second input of the first adder
30 is connected to the output of the first frequency filter 28. The
first input of the second adder 31 is connected to the output of
the second channel for processing a return signal, with the output
of the analog-to-digital converter 22 serving as an output of said
second channel. The second input of the second adder 31 is
connected to the output of the second frequency filter 29.
[0103] The first input of the first signal multiplying block 40 is
connected to the output of the first adder 30. The second input of
the first signal multiplying block 40 is connected to the output of
the first block 42 for generating a reference signal. The first
input of the second signal multiplying block 41 is connected to the
output of the second adder 31. The second input of the second
signal multiplying block 41 is connected to the output of the
second block 43 for generating a reference signal 43.
[0104] The input of the first integrator 36 is connected to the
output of the first signal multiplying block 40. The output of the
first integrator 36 is connected to the first input of the second
electronic switch 44 and to the input of the first block 34 for
calculating signal energy. The input of the second integrator 37 is
connected to the output of the second signal multiplying block 41.
The output of the second integrator 37 is connected to the second
input of the second electronic switch 44 and to the input of the
second block 35 for calculating signal energy.
[0105] The output of the first block 34 for calculating signal
energy is connected to the first input of the first comparator 38.
The output of the second block 35 for calculating signal energy is
connected to the second input of the first comparator 38. The
output of the first comparator 38 is connected to the control input
of the second electronic switch 44.
[0106] The input of the first block 32 for calculating signal
amplitude is connected to the output of the first frequency filter
28. The output of the first block 32 for calculating signal
amplitude is connected to the first input of the second comparator
39. The input of the second block 33 for calculating signal
amplitude is connected to the output of the second frequency filter
29. The output of second block 33 for calculating signal amplitude
is connected to the second input of the second comparator 39. The
output of the second comparator 39 is connected to the control
input of the third electronic switch 45.
[0107] The first input of the third electronic switch 45 is
connected to the output of the first frequency filter 28, and the
second input--to the output of the second frequency filter 29. The
output of the third electronic switch 45 is connected to the input
of the respiratory rate calculating block 46. The output of the
second electronic switch 44 is connected to the input of the heart
rate calculating block 47. The first input of the data displaying
block 48 is connected to the output of the heart rate calculating
block 47. The second input of the data displaying block 48 is
connected to the output of the respiratory rate calculating block
46.
[0108] In the first version of embodiment of the path for
calculating respiratory and heat rates, illustrated in FIG. 12, the
blocks 42 and 43 for generating reference signals are provided with
inputs connected to the outputs of the adders 30 and 31,
respectively. The output signals of the adders 30 and 31 in the
given version of embodiment are used for forming a reference signal
in the form of lengths of a return signal under process in the real
time. Duration of time intervals for such signal lengths is
selected to be 3 s. The formed reference signals are transferred to
the input of the respective signal multiplying block (40 or
41).
[0109] In the second version of embodiment of the respiratory and
heart rates calculating path illustrated in FIG. 13, the blocks 42
and 43 for generating reference signals are designed for forming
signals of constant shape. The reference signal is introduced into
a memory element of each of said blocks 42 and 43 for generating
reference signals and transferred to the input of the respective
signal multiplying block (40 or 41). The reference signal may be a
signal length with duration of 3 s, said signal length being
characterized by the following dependence:
Z ( t ) = - ( t 2 - 1 ) .times. exp ( - t 2 2 ) ##EQU00009##
[0110] It should be noted that in the examples of embodiment of the
pulsed ultra-wideband sensor under consideration, a number of
additional elements and blocks are used which may be avoided, under
the stipulation that the implementation of the invention and the
achievement of the technical result connected with an increase in a
phase sensitivity of the sensor and an accuracy of measurements
upon movement of the subject under study may be still reached.
[0111] Particularly, in certain cases of a constructive embodiment
of the sensor, the employment of a common data displaying block is
not needed. The outputs of the signal mixers 13 and 18 functioning
in the sensor as phase detectors may be directly connected to the
inputs of the frequency filters 28 and 29. The channels for
processing the return signal may be connected to the receiving
antenna 4 without usage of additional means for signal
amplification and frequency selection. In the path of the probing
signal transmitter, the transmitting antenna 3 may be connected
directly to the first output of the first electronic switch 5.
[0112] Moreover, in some versions of constructive embodiment of the
sensor, the transmitting antenna 3 and the receiving antenna 4 may
be integrated in a single block of the transmit-receive device (not
shown in the drawing). The given block provides coupling at various
periods of time of the transmit-receive device, which alternately
functions as an electromagnetic signal emitter and receiver, to the
path of the probing signal transmitter--in the mode of operation of
the transmitting antenna--and to the path of the return signal
receiver--in the mode of operation of the receiving antenna. The
paths of the transmitter and the receiver may be alternately
coupled to the block of the transmitting-and-receiving antenna
through an additional electronic switch. The employment of the
single block of the transmitting-and-receiving antenna enables
integration of two independently functioning antennas in a single
constructional part of the sensor.
[0113] The above described pulsed ultra-wideband sensor operates as
follows.
[0114] The driving generator 23 generates square-shaped
synchronizing pulses with a period T.sub.0 (a time diagram of
synchronizing pulses is represented in FIG. 14). Then the signal is
divided and received into two paths: the path for forming a
synchronizing signal of the transmitter designed for controlling
the generation of a probing signal, and the path for forming a
synchronizing signal of the receiver.
[0115] In the path for forming a synchronizing signal of the
transmitter, a short video pulse with a delay t.sub.d1 (see FIG.
16) is formed at the leading edge of the first synchronizing pulse
by means of a first short-pulse former 24. The duration of the
formed pulse depends on the desired duration of the probing
signal.
[0116] In the path for forming a synchronizing signal of the
receiver, the controlled digital delay line 25 provides delaying of
the synchronizing pulse for a time t.sub.d2 (see the time diagram
in FIG. 15) during which delay the probing signal is propagated to
the subject under test and comes back to the sensor. The delay
value defines the extent of the working distance of measurement of
the sensor and is calculated according to the formula:
t d 2 = 2 R 1 C , ##EQU00010##
where R.sub.1 is a distance between the subject under study and the
sensor, C is a propagation speed of electromagnetic waves. Using
the second short-pulse former 26, a short video pulse of a
synchronizing signal with a delay of t.sub.d3=t.sub.d1 (see FIG.
17) is formed at the leading edge of the second synchronizing
pulse. The given synchronizing signal is sent to the first output
of the control unit 1 connected to the control input of the first
electronic switch 5.
[0117] The synchronizing signals formed in the paths of the control
unit by means of the "OR" circuit 27 are combined into a single
synchronizing signal which is a periodic sequence of pairs of video
pulses-duplets (see FIG. 18). The time interval between the duplet
pulses is defined by the delay time t.sub.d2. The period T0 of
duplet pulses is set by the driving generator 23. The synchronizing
signal including the duplet of video pulses is sent to the second
output of the control unit 1 connected to the control input of the
self-contained microwave generator 2. On entry of the control
synchronizing signal, the self-contained microwave generator 2
generates two coherent radio pulses following each other with a
time interval t.sub.d2 (see FIG. 19).
[0118] The duplet of coherent pulses formed in the self-contained
microwave generator 2 is transmitted through a buffer amplifier 6
and a band pass filter 7 of the probing signal to the input of the
first electronic switch 5. The first electronic switch 5 is
controlled by means of synchronizing signals delivered from the
first output of the control unit 1 to the control input of the
electronic switch. The first electronic switch 5 provides for
controlled switching of the signals formed in the probing signal
forming path. Controlled by the synchronizing signals of the
control unit 1, the probing signals are sent to the path of the
signal transmitter or to the path of the return signal
receiver.
[0119] In the initial state, the first electronic switch 5 is in
the position shown in FIG. 10. In the given position, the signal of
the self-contained microwave generator 2 enters the path of the
probing signal transmitter. In the amplifier of the transmitter 9
the probing signal is amplified to the desired extent, with signal
energy losses being neutralized in the band pass filter 7 of the
probing signal and in the band pass filter 8 of the transmitter.
The band pass filters 7, 8 and 10 have a pass band of from 3 GHz to
10 GHz and are designed for suppressing the out-of-band
radiation.
[0120] The generated probing signal is transmitted to the
transmitting antenna 3 and spread toward the subject under study.
In a rated time interval t.sub.d2 necessary for propagation of the
probing signal to the subject under test and back to the sensor, a
video pulse is generated in the path for forming a synchronizing
signal of the receiver, said video pulse being transferred from the
first output of the control unit 1 to the control input of the
first electronic switch 5.
[0121] On entry of the synchronizing signal, a controlling action
is generated in the first electronic switch for changing the
switching of contacts. As a result, the probing signal forming path
is connected to the second inputs of the signal mixers 13 and 18.
The probing reference signal is delivered to the signal mixer 18
after passage through the phase-shifting circuit 12 providing a
phase shift by an angle of 90.degree.. As a result, the second
coherent radio pulse of the self-contained microwave generator 2
enters the second channel for processing a return signal with a
shifted phase. The in-phase signal and the signal with a shifted
phase function are served as reference signals for the signal
mixers 13 and 18.
[0122] The signal reflected from the subject under test and
received by the receiving antenna 4 passes through the band pass
filter 10 of the return signal, providing reduction in the level of
noises from the outside radio systems, and is amplified to the
desired extent by means of the low-noise amplifier 11. The filtered
out and amplified return signal is sent to the channels for
processing a return signal, to the first inputs of the signal
mixers 13 and 18 functioning as phase detectors. After correlation
with the probing reference signals which are sent to the second
inputs of the signal mixers 13 and 18, two signals are generated in
the channels for processing a return signal: a first in-phase
signal in the first channel and a second signal with a phase shift
by an angle of 90.degree. in the second channel.
[0123] In each of the channels for processing a return signal, the
signal is separated in each of the band pass filters 14 and 19 and
the signals are amplified by means of the low-frequency amplifiers
15 and 20. The low-frequency filters 16 and 21 provide the
frequency selection of the signals and separation of the signals
having frequency above the "cutoff frequency", which is about 0.1
Hz to correspond the lower boundary of the respiratory rate. The
separated and amplified signals are then digitized in the
analog-to-digital converters 17 and 22 of the first and second
channels for processing a return signal.
[0124] At the output of the first channel for processing a return
signal, a signal
Z 1 ( t ) = 1 2 E m cos ( .PHI. ( t ) + .PHI. 1 ) ##EQU00011##
is formed, which is in phase with the probing reference signal (see
FIG. 20). At the output of the second channel for processing a
return signal, a signal Z.sub.2
( t ) = - 1 2 E m sin ( .PHI. ( t ) + .PHI. 1 ) ##EQU00012##
is formed which is phase shifted relative to the probing reference
signal by an angle of 90.degree. (see FIG. 22). The given signals
are transmitted to the respiratory rate and heart rate calculating
path, the structure design of which path is shown in FIGS. 12 and
13.
[0125] The signal of the first channel for processing a return
signal is sent to the first frequency filter 28, and the signal of
the second channel--to the second frequency filter 29. The
indicated filters having the upper "cutoff frequency" of about 1 Hz
provide a delay of a high-frequency signal indicative of the heart
rate. Thereby the signals indicative of patient's respiration are
separated at the output of the frequency filters 28 and 29 from the
resultant return signal involving the signals indicative of the
patient's chest oscillations and heart rate.
[0126] After the frequency selection, the signals from the outputs
of the frequency filters 28 and 29 enter the second inputs of the
signal adders 30 and 31, the inputs of the third electronic switch
45 and the inputs of the blocks 32 and 33 for calculating a
amplitude of the signal. The signals of the first and second
channels for processing a return signal are sent to the first
inputs of the signal adders 30 and 31, respectively.
[0127] The signal adders 30 and 31 operate in a mode of extracting
signals delivered to their inputs. After extraction of signals
indicative of chest oscillations from the composite return signals
of the first and second channels for processing a return signal,
the signals indicative of patient's heart rate are formed at the
outputs of the adders 30 and 31. Discrete signals produced as a
result of frequency selection and characterizing various
physiological parameters (respiration and heartbeats) are subjected
to further correlation processing.
[0128] Signal multiplying blocks 40 and 41 and integrators 36 and
37 coupled to the outputs of said blocks are used as a correlation
system for processing a signal indicative of a heart rate. The
signals from the outputs of adders 30 and 31 are transferred to the
first inputs of the signal multiplying blocks 40 and 41. The
reference signals from the outputs of the blocks 42 and 43 for
generating a reference signal are supplied to the second inputs of
the signal multiplying blocks 40 and 41.
[0129] In the first version of embodiment of the respiratory rate
and heart rate calculating path whose block diagram is illustrated
in FIG. 12, the blocks 42 and 43 for generating a reference signal
are provided with inputs coupled to the outputs of signal adders 30
and 31, respectively. In such a case, fixed lengths of signals
under process are used as a reference signal. The duration of such
lengths of signals is selected to be equal to at least average
oscillation period of a return signal. With the example of
embodiment of the sensor under consideration the duration of the
formed reference signal is 3 s.
[0130] In certain time intervals, for example with a period of 60
s, a length of a signal is recorded by means blocks 42 and 43 at
the output from the respective signal adders 30 and 31 to a memory
element. The given length of a signal is used as a reference signal
and is transferred to the second input of the respective signal
multiplying block (40 or 41) till next recording of a signal
length.
[0131] In the second version of embodiment of the respiratory rate
and heart rate calculation path, whose block diagram is illustrated
in FIG. 13, the blocks 42 and 43 are designed for forming a
reference signal of constant shape. The signal with a predetermined
shape of a curve is stored in memory units of the blocks 42 and 43
and is continuously transferred to the input of the respective
signal multiplying block (40 or 41).
[0132] In the example of embodiment of the respiratory rate and
heart rate calculating path, as a fixed length of a reference
signal is used a signal with a predetermined shape of curve, the
so-called wavelet, described by the following dependence:
Z ( t ) = - ( t 2 - 1 ) .times. exp ( - t 2 2 ) . ##EQU00013##
The duration of such a reference signal is selected to be equal to
at least average oscillation period of a return signal. For the
example under consideration the duration of the formed signal is 3
s.
[0133] Upon multiplying of the incoming signals in the blocks 40
and 41, the reference signal is moved discretely along the signal
under process, and the product of multiplying the incoming signals
is calculated. The resultant signals from the outputs of the blocks
40 and 41 are transferred to the respective integrators 36 and 37,
by means of which integrators the correlation integrals of the
signals under process are discretely calculated for each current
instant of time. Time diagrams Z.sub.1(t) and Z.sub.2(t) of the
signals, respectively, of the first and second channels for
processing a return signal at the output of the first and second
integrators 36 and 37 are illustrated in FIGS. 21 and 23.
[0134] It is obvious from the cited time diagrams Z.sub.1(t) and
Z.sub.2(t) of the signals of the first and second channels for
processing a return signal that the signal of the first channel at
the output of the correlation system (see FIG. 21) is of
distinguishable cyclic character and allows the heart rate value to
be determined with a high accuracy. The signal of the second
channel (see FIG. 23) is of "diffuse" non-periodic character, and
due to this the heart rate may not be determined with a desired
accuracy.
[0135] The signals generated in the integrators 36 and 37 are then
transferred to the second inputs of the second electronic switch 44
and to the inputs of the signal energy calculating blocks 34 and
35. The signal Z.sub.1(t) enters from the output of the first
integrator 36 to the first input of the second electronic switch 44
and to the input of the first signal energy calculating block 34
from the first channel for processing a return signal. The signal
Z.sub.2(t) enters from the output of the second integrator 37 to
the second input of the second electronic switch 44 and to the
input of the second signal energy calculating block 35 from the
second channel for processing a return signal.
[0136] In order to select a signal which may be further used for
precise determining of a heart rate, a procedure for selecting a
signal on the basis of its energy value is applied. The energy of
the signals delivered from the first and second channels for
processing a return signal is determined using the blocks 34 and 35
for calculating energy. The energy of signal in each of the blocks
34 and 35 is determined as a sum of squares of signal amplitude
values during a fixed time interval. In the example of embodiment
of the sensor under consideration, the squares of signal amplitude
values are calculated during a fixed time interval. The procedure
for determining the energy in the blocks 34 and 35 is provided in a
real time mode during a three-second time interval ("a sliding
window") which moves along the incoming signal for one time-taking
after each measurement.
[0137] The calculated signal energy values are then transferred
from the outputs of the blocks 34 and 35 respectively to the first
and second inputs of the first comparator 38. The comparator 38
allows the incoming signals to be compared and a signal having a
maximum high energy to be defined. A comparative diagram of energy
values of the signals E(t) calculated in relative units of
measurement is presented in FIG. 24. The upper curve in the
comparative diagram E(t) shows changing in the signal energy at the
output of the first signal energy calculating block 34. The lower
curve in the comparative diagram E(t) characterizes changing in the
signal energy at the output of the second signal energy calculating
block 35.
[0138] It follows from the comparative diagram presented (see FIG.
24) that the signal delivered from the first channel for processing
the return signal substantially surpasses the signal delivered from
the second channel for processing a return signal in its energy
value. Based on the result of comparison of the two incoming
signals, the comparator 38 sends the signal to the control input of
the second electronic switch 44. The result is that a controlling
action is generated for changing the position of the switch
contacts, the said changed position should comply with the selected
signal of maximum energy. The output of the first integrator 36 is
switched to the input of the heart rate calculating block 47
designed for further processing of the selected signal.
[0139] Using the heart rate calculating block 47, the local maximum
values of the signal under test are searched and time marks
(current time values) are defined in conformance with the local
maximum values found out. On the basis of the revealed time marks,
the patient's heart rate is calculated. The signal indicative of
the calculated heart rate value is then transferred to the first
input of the data displaying block 48.
[0140] In order to select a signal which is to be further used for
precise determining of the respiratory rate, a procedure is used
for selecting the signal on the basis of an amplitude value.
Utilization of the signal amplitude value as a criterion in
comparing of signals at the output of the frequency filters 28 and
29 is due to the low-frequency nature of the curve corresponding to
the oscillations of the patient's chest. The respiratory rate is
essentially lower in its value, approximately by an order of
magnitude, than the heart rate. Therefore, a determining factor for
selecting a respiration signal for further processing is the
availability of pronounced maximum values of signal amplitude. It
is evident from the presented time diagrams Z.sub.1(t) and
Z.sub.2(t) of the signals of the first and second channels for
processing a return signal that the amplitude of the signal of the
first channel substantially surpasses the amplitude of the signal
of the second channel. The average range between the opposite
signal peaks of the first channel is about 40 units and the
respective average range for the second channel is about 3 units
(see FIGS. 20 and 22).
[0141] The correlation processing of the respiration signals
separated using the filters 28 and 29 is carried out by means of
two signal amplitude calculating blocks 32 and 33. At the output of
the first block 32 is formed a signal indicative of an amplitude of
the respiration signal delivered from the first channel for
processing a return signal. At the output of the second block 33 is
formed a signal indicative of an amplitude of the respiration
signal delivered from the second channel for processing a return
signal. The signals defining the respiration signal amplitude are
transferred from the blocks 32 and 33 respectively to the first and
second inputs of the second comparator 39.
[0142] The values of the two incoming signals from the blocks 32
and 33 for calculating a signal amplitude are compared by
comparator 39. On the basis of a comparison result, the comparator
39 sends the signal to the control input of the third electronic
switch 45 to generate a control action for changing the position of
the switch contacts. The switched connection of contacts should
correspond to the selected signal of maximum amplitude. In the
example of embodiment under consideration the output of the first
frequency filter 28 is connected to the output of the block 46 for
calculating a respiratory rate, and the selected signal is
delivered from the first channel for processing a return signal to
the indicated block for further processing thereof.
[0143] Using the block 46 for calculating a respiratory rate, local
maximum values of the signal under study are searched and time
marks (current time values) are defined in conformance with the
local maximum values found. On the basis of the revealed time
marks, the patient's respiratory rate is calculated. The signal
indicative of the calculated respiratory rate value is then
transferred to the second input of the data displaying block 48.
The block 48 is used for displaying the results of measurements of
the respiratory and heart rates in the form convenient for visual
controlling, in particular, in the form of numerical values
displayed on a monitor unit.
[0144] FIG. 25 shows a processing circuit according to one
embodiment of the present invention. The processing circuit 2500 is
applied to a pulsed ultra-wideband sensor for measuring a
respiratory rate and a heart rate, such as the pulsed
ultra-wideband sensors according to embodiments of the present
invention, and comprises a first frequency filter 2501, a second
frequency filter 2502, a first signal amplitude calculating unit
2503, a second signal amplitude calculating unit 2504, a first
electronic switch 2505, a first adder 2506, a second adder 2507, a
first signal integrating unit 2508, a second signal integrating
unit 2509, a first signal energy calculating unit 2510, a second
signal energy calculating unit 2511 a second electronic switch
2512, a first comparator 2513 and a first comparator 2514.
[0145] The first frequency filter 2501 is configured to receive an
in-phase signal, such as the output signal of the ADC 17. The
second frequency filter 2502 is configured to receive a quadrature
signal, such as the output signal of the ADC 22. The first signal
amplitude calculating unit 2503 is configured to calculate
amplitude of the output signal of the first frequency filter 2501.
The second signal amplitude calculating unit 2504 is configured to
calculate amplitude of the output signal of the second frequency
filter 2502. The first electronic switch 2505 is configured to
output one of the output signals of the first and the second
frequency filters 2501 and 2502 according to the calculated results
of the first and the second signal amplitude calculating units 2503
and 2504. The first adder 2506 is configured to subtract the output
signal of the first frequency filter 2501 from the input signal of
the first frequency filter 2501. The second adder 2507 is
configured to subtract the output signal of the second frequency
filter 2502 from the input signal of the second frequency filter
2502. The first signal integrating unit 2508 is configured to
calculate correlation integrals of the output signals of the first
adder 2506 and a first reference signal. The second signal
integrating unit 2509 is configured to calculate correlation
integrals of the output signals of the second adder 2507 and a
second reference signal. The first signal energy calculating unit
2510 is configured to calculate signal energy of the output signal
of the first signal integrating unit 2508. The second signal energy
calculating unit 2511 is configured to calculate signal energy of
the output signal of the second signal integrating unit 2509. The
second electronic switch 2512 is configured to output one of the
output signals of the first and the second signal integrating units
2508 and 2509 according to the calculated results of the first and
the second signal energy calculating units 2510 and 2511.
[0146] In some embodiments, the first signal integrating unit 2508
comprises a first signal multiplying block 2515 and a first
integrator 2516. The first signal multiplying block 2515 is
configured to multiply the output signal of the first adder 2506 by
the first reference signal. The first integrator 2516 is configured
to calculate the integral of the output signal of the first signal
multiplying block 2515. In other embodiments, the second signal
integrating unit 2509 comprises a second signal multiplying block
2517 and a second integrator 2518. The second signal multiplying
block 2517 is configured to multiply the output signal of the
second adder 2507 by the second reference signal. The second
integrator 2518 is configured to calculate the integral of the
output signal of the second signal multiplying block 2517. In some
embodiments, the processing circuit 2500 further comprises a first
comparator 2513 and a second comparator 2514. The first comparator
2513 is configured to compare the calculated results of the first
and the second signal amplitude calculating units 2503 and 2504 and
control the first electronic switch 2505. The second comparator
2514 is configured to compare the calculated results of the first
and the second signal energy calculating units 2510 and 2511 and
control the second electronic switch 2512. In some embodiments, the
first reference signal and the second reference signal exhibit a
constant shape. In other embodiments, the first reference signal is
generated according to the output signal of the first adder 2506,
while the second reference signal is generated according to the
output signal of the second adder 2507. In some embodiments, the
processing circuit 2500 further comprises a first reference signal
generating block for the generation of the first reference signal,
and a second reference signal generating block for the generation
of the second reference signal.
[0147] The sensor implemented according to the invention allows the
frequency selection of the return signal to be sequentially
executed in the two processing channels, independent signals
describing the respiratory rate to be selected separately from
other signals describing the heart rate, separate correlation
processing of the separated signals to be provided, and,
thereafter, the signal with the maximum high information content to
be selected for each of the physiological parameters under study
for further calculation of the respiratory and heart rate values
with a desired accuracy. However, the physiological parameters
measured according to the sensor and the method thereof are not
limited to respiratory rate or heart rate, but can also applied to
other physiological parameters such as intestinal motility.
[0148] The given procedure for processing the return signal,
realized using a certain structured design of the path for
calculating the respiratory and heart rate values, allows a phase
sensitivity of the sensor and measurement accuracy of the
physiological parameters under study to be significantly increased.
In addition, there appears the possibility of measuring the
parameters upon movement of the subjects under study thanks to the
elimination of influence upon the measurement results of the
"blind" zones at the working distance of the sensor.
[0149] The pulsed ultra-wideband sensor may be employed in medical
equipment as a high-sensitive means for cardio-vascular system and
respiratory organs diagnosis under stationary and field
conditions.
[0150] A list of digital and abbreviated letter symbols of
structural elements of a pulsed ultra-wideband sensor, depicted in
FIGS. 10, 11, 12, and 13 on the accompanying drawings:
[0151] 1--control unit (CU);
[0152] 2--self-contained microwave generator (SMG);
[0153] 3--transmitting antenna;
[0154] 4--receiving antenna;
[0155] 5--first electronic switch;
[0156] 6--buffer amplifier (BA);
[0157] 7--band pass filter for a probing signal (BFPS);
[0158] 8--bans pass filter for a transmitter (BFT);
[0159] 9--transmitter amplifier (TA);
[0160] 10--band pass filter for a return signal (BFRS);
[0161] 11--low-noise amplifier (LNA);
[0162] 12--phase-shifting circuit (PSC);
[0163] 13--signal mixer of a first channel for processing a return
signal (SM1);
[0164] 14--band pass filter of a first channel for processing a
return signal (BF1);
[0165] 15--low-frequency amplifier of a first channel for
processing a return signal (LFA1);
[0166] 16--low-frequency filter of a first channel for processing a
return signal (LFF1);
[0167] 17--analog-to-digital converter of a first channel for
processing a return signal (ADC1);
[0168] 18--signal mixer of a second channel for processing a return
signal (SM2);
[0169] 19--band pass filter of a second channel for processing a
return signal (BF2);
[0170] 20--low-frequency amplifier of a second channel for
processing a return signal (LFA2);
[0171] 21--low-frequency filter of a second channel for processing
a return signal (LFF2);
[0172] 22--analog-to-digital converter of a second channel for
processing a return signal (ADC2);
[0173] 23--driving generator of a control unit (DG);
[0174] 24--first short-pulse former of a control unit (SPF1);
[0175] 25--digital delay line of a control unit (DDL);
[0176] 26--second short-pulse former of a control unit (SPF2);
[0177] 27--"OR" circuit of a control unit;
[0178] 28--first frequency filter (FF1);
[0179] 29--second frequency filter (FF2);
[0180] 30--first adder (AD1);
[0181] 31--second adder (AD2);
[0182] 32--first block for calculating a signal amplitude
(BCA1);
[0183] 33--second block for calculating a signal amplitude
(BCA2);
[0184] 34--first block for calculating a signal energy (BCE1);
[0185] 35--second block for calculating a signal energy (BCE2);
[0186] 36--first integrator (INT1);
[0187] 37--second integrator (INT2);
[0188] 38--first comparator (COM1);
[0189] 39--second comparator (COM2);
[0190] 40--first signal multiplying block (SMB1);
[0191] 41--second signal multiplying block (SMB2);
[0192] 42--first block for generating a reference signal
(GRS1);
[0193] 43--second block for generating a reference signal
(GRS2);
[0194] 44--second electronic switch;
[0195] 45--third electronic switch;
[0196] 46--respiratory rate calculating block (BCR);
[0197] 47--heart rate calculating block (BCH);
[0198] 48--data display block (DDB);
[0199] 2500--processing circuit;
[0200] 2501--first frequency filter (FF1);
[0201] 2502--second frequency filter (FF2);
[0202] 2503--first signal amplitude calculating unit (BCA1);
[0203] 2504--second signal amplitude calculating unit (BCA2);
[0204] 2505--first electronic switch;
[0205] 2506--first adder (AD1);
[0206] 2507--second adder (AD2);
[0207] 2508--first signal integrating unit;
[0208] 2509--second signal integrating unit;
[0209] 2510--first signal energy calculating unit (BCE1);
[0210] 2511--second signal energy calculating unit (BCE2);
[0211] 2512--second electronic switch;
[0212] 2513--first comparator (COM1);
[0213] 2514--second comparator (COM2);
[0214] 2515--first signal multiplying block (SMB1);
[0215] 2516--first integrator (INT1);
[0216] 2517--second signal multiplying block (SMB2);
[0217] 2518--second integrator (INT2).
* * * * *