U.S. patent application number 13/196139 was filed with the patent office on 2012-03-08 for ultra wideband (uwb) baby monitors for detection of infant cardiopulmonary distress.
Invention is credited to Joe P. Tupin, JR..
Application Number | 20120059268 13/196139 |
Document ID | / |
Family ID | 45560013 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120059268 |
Kind Code |
A1 |
Tupin, JR.; Joe P. |
March 8, 2012 |
ULTRA WIDEBAND (UWB) BABY MONITORS FOR DETECTION OF INFANT
CARDIOPULMONARY DISTRESS
Abstract
Ultra wideband patient monitoring systems, and particularly baby
monitoring systems, adapted to prevent reflective loss between the
antenna and the patient's body. The devices, systems and methods
described herein may be used to efficiently couple UWB energy to a
patient for patient monitoring. In particular, described herein are
impedance transformer pads, mats and the like, upon which a patient
may comfortably lie while being monitored via one or more UWB
sensors (e.g., antenna); the impedance transformer pads help match
the impedance and prevent reflective loss of UWB energy. Also
described herein are bassinets, including NICU bassinets and baby
monitors.
Inventors: |
Tupin, JR.; Joe P.;
(Truckee, CA) |
Family ID: |
45560013 |
Appl. No.: |
13/196139 |
Filed: |
August 2, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61369843 |
Aug 2, 2010 |
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Current U.S.
Class: |
600/484 |
Current CPC
Class: |
H01Q 5/25 20150115; G01S
13/0209 20130101; G01S 13/88 20130101; A61B 5/0205 20130101; A61B
2503/045 20130101; A61B 5/0002 20130101; G01S 13/42 20130101; G01S
7/28 20130101; A61B 5/6892 20130101; A61B 5/05 20130101 |
Class at
Publication: |
600/484 |
International
Class: |
A61B 5/0205 20060101
A61B005/0205 |
Claims
1. An impedance transformer pad for use with an ultra wideband
(UWB) monitoring system to minimize reflective loss of the UWB
energy, the impedance transformer pad comprising: a soft or
resilient recumbent surface formed at least in part from an
impedance transformer region having a thickness of between about
0.4 cm and 7 cm, wherein the impedance transformer region has at
least one layer having a dielectric constant of between about 5 and
about 20; and a UWB antenna abutting the impedance transformer
region; wherein the UWB antenna is configured to transmit and
receive UWB signals through the impedance transformer region to
monitor the patient resting on the pad.
2. The pad of claim 1, wherein the recumbent surface is sized to
fit into a bassinet.
3. The pad of claim 1, wherein the impedance transformer region has
a single homogenous layer.
4. The pad of claim 1, wherein the impedance transformer region has
at least two adjacent planar layers, wherein each planar layer has
a different thickness and dielectric constant.
5. The pad of claim 1, wherein the impedance transformer region has
three adjacent planar layers, wherein each planar layer has a
different thickness and dielectric constant.
6. The pad of claim 1 wherein the impedance transformer region is
formed of silicone.
7. The pad of claim 1, wherein the impedance transformer region has
a thickness of between about 0.5 cm and 5 cm.
8. The pad of claim 1, further comprising a backing beneath the
impedance transformer region and the UWB antenna.
9. The pad of claim 1, further comprising a plurality of UWB
antennas beneath and abutting the impedance transformer region.
10. The pad of claim 1, wherein the antenna is configured to emit a
UWB signal having a bandwidth, and wherein the impedance
transformer region has one or more planar layers each having a
dielectric and wherein and the thickness of each layer is
approximately one quarter or one half of the wavelength of the
center frequency of the bandwidth in the dielectric of that
layer.
11. A ultra wideband (UWB) patient monitoring system having an
impedance transformer pad to minimize reflective loss, the system
having a UWB bandwidth for emitting sensing signals, the system
further comprising: an impedance transformer pad having a UWB
antenna beneath an impedance transformer region, the antenna
configured to transmit UWB signals through the impedance
transformer region to a patient resting on the pad, wherein the
impedance transformer region has one or more planar layers and the
thickness of each layer is approximately one quarter or one half of
the wavelength of the center frequency of the bandwidth in the
dielectric of that layer; and a processor configured to receive
signals from UWB antenna to monitor the patient.
12. The system of claim 11, wherein the impedance transformer pad
further comprises a backing layer behind the impedance transformer
layer and the antenna.
13. The system of claim 11, further comprising a cable connecting
the antenna of the impedance transformer pad to the processor.
14. The system of claim 11, wherein the impedance transformer pad
is flexible, hypoallergenic, and water proof.
15. The system of claim 11, wherein the impedance transformer
region of the impedance transformer pad has a single homogenous
layer configured as a quarter wavelength layer wherein the
thickness is approximately one quarter of the wavelength of the
center frequency of the bandwidth in the dielectric of the
layer.
16. The system of claim 11, wherein the impedance transformer
region of the impedance transformer pad has two or more layers.
17. The system of claim 11, wherein the impedance transformer
region of the impedance transformer pad has three layers,
comprising adjacent planar layers configured as a quarter
wavelength layer, a half wavelength layer, and a quarter wavelength
layer.
18. The system of claim 11, wherein the impedance transformer is
configured to fit within a bassinet.
19. The system of claim 11, wherein the impedance transformer pad
comprises a plurality of UWB antennas.
20. The system of claim 11, wherein the UWB antenna is an air
antenna.
21. A method of monitoring an infant using an ultra wideband (UWB)
radar system including an impedance transformer pad, the method
comprising: placing the infant atop the impedance transformer pad;
and emitting a UWB signal from a UWB antenna, wherein the signal
passes from the antenna, through an impedance transformer region of
the impedance transformer pad and into the infant, further wherein
the impedance transformer region has at least one layer having a
dielectric constant of between about 5 and about 20, wherein the
impedance transformer pad reduces the impedance miss-match between
the antenna and the infant to reduce reflective loss of energy from
the signal.
22. The method of claim 21, further comprising receiving a
reflected UWB signal from the infant using the UWB antenna.
23. The method of claim 21, wherein emitting the UWB signal
comprises passing the signal through the impedance transformer
region wherein the impedance transformer region has a single
homogenous planar layer having a dielectric that is the geometric
mean of the dielectric of the antenna and the dielectric of the
infant.
24. The method of claim 21, wherein emitting the UWB signal
comprises passing the signal through the impedance transformer
region wherein the impedance transformer region has a thickness
between about 0.4 cm and about 7 cm.
25. The method of claim 21, wherein emitting the UWB signal
comprises passing the signal through the impedance transformer
region wherein the impedance transformer region has a plurality of
layers each with a dielectric value, wherein the thickness of each
layer is approximately one quarter or one half of the wavelength of
a center frequency of the bandwidth of the emitted signal in the
dielectric of that layer.
26. The method of claim 21, wherein placing comprises placing the
infant atop the impedance transformer pad within an NICU
bassinet.
27. The method of claim 21, wherein emitting comprises emitting the
UWB signal from the antenna to the infant through the impedance
transformer region without passing thought the air.
28. An ultra wideband (UWB) baby monitoring system, the system
comprising: an impedance transformer pad having a soft or resilient
recumbent surface upon which a baby may rest; a UWB antenna coupled
to the impedance transformer pad and configured to emit a UWB
signal through the transformer pad and into the baby, wherein the
impedance transformer pad is configured to prevent reflective loss
of more than 50% of energy of the UWB signal; and a processor in
communication with the UWB antenna and configured to monitor the
baby when the baby is resting on the impedance transformer pad.
29. The system of claim 28 configured to apply UWB signals in a
bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a different dielectric value.
30. The system of claim 28 configured to apply UWB signals in a
bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a dielectric value, wherein the
thickness of each layer is less than one half of the wavelength of
the center frequency in the dielectric of that layer.
31. The system of claim 28 configured to apply UWB signals in a
bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a dielectric value, wherein the
thickness of each layer is approximately one quarter or one half of
the wavelength of the center frequency in the dielectric of that
layer.
32. The system of claim 28, wherein the impedance transformer pad
is configured to fit within a bassinet.
33. The system of claim 28, wherein the impedance transformer pad
comprises a non-toxic, hypoallergenic, and water proof
material.
34. A bassinet configured for ultra wideband (UWB) monitoring of an
infant, the bassinet comprising: a temperature-regulated bassinet
enclosure having walls and a lower surface; and at least one UWB
antenna integrated into the bassinet and configured to emit UWB
energy into an infant within the bassinet from the tower surface of
the bassinet; wherein the tower surface of the bassinet impedance
matches to minimize reflective loss of UWB energy between the UWB
antenna and the infant.
35. The bassinet of claim 34, wherein the lower surface comprises
an impedance transformer pad covering the UWB antenna on that the
UWB antenna emits UWB signals through the impedance transformer
pad.
36. The bassinet of claim 34, wherein the UWB antenna is configured
to apply UWB signals in a bandwidth having a center frequency,
further wherein the lower surface comprises an impedance
transformer region covering the UWB antenna, on which an infant may
rest, wherein the impedance transformer region has one or more
planar layers each with a dielectric value, wherein the thickness
of each layer is less than one half of the wavelength of the center
frequency in the dielectric of that layer.
37. The bassinet of claim 34, wherein the UWB antenna has a
dielectric approximately matched to the dielectric of the
infant.
38. The bassinet of claim 34, wherein the UWB antenna has a
dielectric of approximately 50.
39. The bassinet of claim 34, wherein further comprising a
plurality of UWB antennas.
40. The bassinet of claim 34, further comprising a processor
configured to receive signals from the UWB antenna to monitor the
infant.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. Provisional
Patent Application No. 61/369,843, titled "Non-Contact Baby Monitor
for the Neonatal Intensive Care Unit With Application to Home
Monitoring for Detection of Cardiopulmonary Distress" filed on Aug.
2, 2010.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
FIELD
[0003] Described herein are non-contact baby monitors for
monitoring an infant. In particular, described herein are ultra
wideband (UWB) baby monitoring systems for measuring an infant's
cardiopulmonary state, and detecting distress. Included herein are
devices including integrated UWB monitors and bassinettes and/or
impedance transformer pads for optimizing the transfer of energy
between the UWB system and the infant being monitored.
BACKGROUND
[0004] The Neonatal Intensive Care Unit (NICU) is a unit of a
hospital specializing in the care of ill or premature newborn
infants. Approximately 500,000 babies born in the United States
each year are treated in a neonatal intensive care unit with the
most common causes for admission being premature birth, difficult
delivery, breathing problems, infections, and birth defects.
[0005] NICU protocols specify continuous monitoring of vital signs,
to alert caregivers of a deteriorating condition or an emergent
event. These events can develop slowly, as in hyperkalemia, which
can lead to cardiac arrhythmia, or can appear suddenly, as commonly
seen in respiratory distress. Current monitoring techniques rely
heavily on ECG technology which requires direct skin contact via
adhesive electrodes and are thus highly undesirable due to the need
for skin contact. Premature babies have extremely delicate skin
that is susceptible to damage and infection, increasing their risk
of complications and potentially extending their time in the NICU.
Premature babies younger than 30 to 32 weeks have thin skin,
lacking the layers of body fat that would have been put on during
the final weeks of pregnancy. In extremely premature babies, the
coarse, top layer of skin hasn't yet formed. During their stay in
the NICU, every attempt is made to minimize skin contact, even
limiting physical contact by parents and caregivers.
[0006] Besides the potential for complications resulting from
direct placement of electrodes on the infant's skin, there is an
identified need to reduce the amount of physical contact to the
neonatal intensive care patient since contact is known to stress
the infant and can compromise recovery and development. Thus,
monitoring technologies that minimize placement of electrodes on
the patient as well as minimize the need for caregivers to touch
the patient to collect vital signs information are highly
desirable.
[0007] Thus, there is a need for non-contact baby/infant monitors,
and this need is particularly acute in the NICU context. A number
of variations of non-contact UWB sensors have been proposed, such
as those offered by Sensiotec, and described in U.S. Pat. No.
7,432,847 and U.S. 2009/0227882. However, these devices suffer from
limitations inherent in their configuration resulting in a loss of
signal strength. This loss of signal strength results in less
efficient devices, and may limit the penetration and accuracy.
Thus, it would be useful to provide systems, devices and methods
for monitoring an infant, and particularly an infant in an NICU
setting in a reliable, low-energy and non-contact fashion.
Described herein are systems, devices and methods that may address
this need.
SUMMARY OF THE DISCLOSURE
[0008] Described herein are non-contact monitoring UWB systems,
which may also be referred to as UWB radar systems or UWB radar
monitoring systems. In particular, described herein are UWB
monitoring systems that provide impedance matching between the
emitter (and/or receiver) antenna and the patient such that the
emitted UWB energy is efficiently transmitted and received. In some
variations the system may include an impedance transformer,
configured as a pad or other reclining surface that matches the
impedance (e.g., dielectric) of the antenna to that of the patient.
The impedance transformer may thereby reduce the reflection of UWB
energy between the antenna and the patient, preventing energy loss
and allowing more efficient operation. In some variations, the
system includes a dedicated bassinet in which the UWB components
have been integrated; integration may allow optimization of the
positioning of the UWB antenna. Also described herein are systems
configured to be used with existing cribs or basinets for
monitoring (including at-home monitoring).
[0009] For example, described herein are impedance transformer pads
for use with an ultra wideband (UWB) monitoring system to minimize
reflective loss of the UWB energy. The impedance transformer pads
may include: a soft or resilient recumbent surface formed at least
in part from an impedance transformer region having a thickness of
between about 0.4 cm and 7 cm, wherein the impedance transformer
region has at least one layer having a dielectric constant of
between about 5 and about 20; and a UWB antenna abutting the
impedance transformer region; wherein the UWB antenna is configured
to transmit and receive UWB signals through the impedance
transformer region to monitor the patient resting on the pad.
[0010] Any of the 1, wherein the pads described herein may be for
use with (or integrated into) a bassinet. For example, the
recumbent surface may be sized to fit into a bassinet.
[0011] In some variations the impedance transformer region has a
single homogenous layer. This layer may have a dielectric value
that is intermediate between the dielectric constant of the UWB
antenna(s) and the patient (e.g., the geometric mean). Impedance
transformer regions may include multiple layers (e.g., 2, 3, 4, 5,
6, etc.); virtually any number of layers may be included, however,
this may increase the cost and complexity of the devices. In some
variations, the impedance transformer region has at least two
adjacent planar layers, wherein each planar layer has a different
thickness and dielectric constant. For example, in some variations,
the impedance transformer region has three adjacent planar layers,
wherein each planar layer has a different thickness and dielectric
constant.
[0012] The impedance transformer region (including each layer
thereof) may be formed of any appropriate material that may take
the desired thickness and dielectric properties, as well as being
biocompatible, pliable/soft, easy to clean, non-toxic,
hypoallergenic, and water proof. For example in some variations the
layer(s) of the impedance transformer region are formed of
silicone.
[0013] The size of the impedance transformer region may have a
thickness of between about 0.5 cm and 5 cm, including all of the
layers, if more than one layer is present.
[0014] In some variation, the pad includes a backing layer beneath
the impedance transformer region and the UWB antenna. The pad may
include a plurality of UWB antennas beneath and abutting the
impedance transformer region. The antenna may be configured to emit
a UWB signal having a bandwidth, and wherein the impedance
transformer region has one or more planar layers each having a
dielectric and wherein and the thickness of each layer is
approximately one quarter or one half of the wavelength of the
center frequency of the bandwidth in the dielectric of that
layer.
[0015] Also described herein are ultra wideband (UWB) patient
monitoring systems having an impedance transformer pad to minimize
reflective loss, the system having a UWB bandwidth for emitting
sensing signals, the system further comprising: an impedance
transformer pad having a UWB antenna beneath an impedance
transformer region, the antenna configured to transmit UWB signals
through the impedance transformer region to a patient resting on
the pad, wherein the impedance transformer region has one or more
planar layers and the thickness of each layer is approximately one
quarter or one half of the wavelength of the center frequency of
the bandwidth in the dielectric of that layer; and a processor
configured to receive signals from the UWB antenna to monitor the
patient. Any of the systems and devices described herein may also
include UWB electronics (which may be separate from or incorporated
into a processor) for generating a UWB signal for transmission and
reception by the UWB antenna. Such UWB electronics may include
signal generators, D/A and A/D converters, timing circuitry,
comparators, amplifiers, fitters, and the like. For example see
U.S. Pat. No. 7,725,150, U.S. patent application Ser. No.
12/765,680, published as US 2010/0274145A1, and U.S. patent
application Ser. No. 12/749,861, published as US 2011/0060215A1.
The UWB electronics are typically configured to generate the UWB
signal(s) for emitting from the antenna(s) and processing the
received signal (reflections) to extract physiological data.
[0016] As mentioned, the impedance transformer pad may also include
a backing layer behind the impedance transformer layer and the
antenna. The backing layer may support the recumbent surface formed
by the impedance transfer region (or it may form the recumbent
surface with the impedance transfer region).
[0017] In some variations the pad includes a cable connecting the
antenna of the impedance transformer pad to the UWB electronics
and/or processor.
[0018] In general, the impedance transformer pad is flexible,
hypoallergenic, and water proof. The pad may be used with a crib or
bassinet. For example, the pad may be sized for use in a crib or
bassinet, including a NICU. In some variation the pad includes
indicators (e.g., markings) indicating the location of the
sensors/antenna and/or the preferred positioning for the patient
infant) lying upon the pad.
[0019] In some variations the impedance transformer region of the
impedance transformer pad has a single homogenous layer configured
as a quarter wavelength layer, wherein the thickness is
approximately one quarter of the wavelength of the center frequency
of the bandwidth in the dielectric of the layer. In some variations
the impedance transformer region of the impedance transformer pad
has two or more layers.
[0020] In some variations, the impedance transformer region of the
impedance transformer pad has three layers, comprising adjacent
planar layers configured as a quarter wavelength layer, a half
wavelength layer, and a quarter wavelength layer.
[0021] In any of the variations described herein, the impedance
transformer pad may include a plurality of UWB antennas. Different
antenna may be used, or the same types of antenna. For example, the
UWB antenna may be an air antenna an antenna readily commercially
available that is configured for transmission in air, and therefore
is designed to transfer energy into a medium with a relative
dielectric constant of approximately 1).
[0022] Also described herein are methods of monitoring an infant
using an ultra wideband (UWB) radar system including an impedance
transformer pad, the method comprising: placing the infant atop the
impedance transformer pad; and emitting a UWB signal from a UWB
antenna, wherein the signal passes from the antenna, through an
impedance transformer region of the impedance transformer pad and
into the infant, further wherein the impedance transformer region
has at least one layer having a dielectric constant of between
about 5 and about 20, wherein the impedance transformer pad reduces
the impedance miss-match between the antenna and the infant to
reduce reflective loss of energy from the signal.
[0023] The method may also include receiving a reflected UWB signal
from the infant using the UWB antenna, and analyzing the signal to
monitor the infant. The method may include determining a vital sign
for the infant and in some variations, displaying the vital sign.
For example, the signal may be analyzed to determine heart rate,
etc. The system may include one or more alarms for indicating when
the infant is undergoing distress based on the monitoring. In
general, the systems, methods and devices described herein may use
one or more antennas that can be configured as emitter antenna
(transmitting the UWB signal) and/or receiver antenna (receiving
the UWB signal reflected), or both. Thus, a recovering antenna can
be the same as the transmitting antenna.
[0024] The step of emitting the UWB signal may include passing the
signal through the impedance transformer region wherein the
impedance transformer region has a single homogenous planar layer
having a dielectric that is the geometric mean of the dielectric of
the antenna and the dielectric of the infant. In some variations,
emitting the UWB signal comprises passing the signal through the
impedance transformer region wherein the impedance transformer
region has a thickness between about 0.4 cm and about 7 cm.
[0025] The step of emitting the UWB signal may include passing the
signal through the impedance transformer region wherein the
impedance transformer region has a plurality of layers each with a
dielectric value, wherein the thickness of each layer is
approximately one quarter or one half of the wavelength of a center
frequency of the bandwidth of the emitted signal in the dielectric
of that layer. In general the step of emitting comprises emitting
the UWB signal from the antenna to the infant through the impedance
transformer region without the UWB passing thought the air or a
standard mattress (which may result in increased loss when the
impedance transfer pads described herein).
[0026] In any of the method described herein, placing the infant on
the pad may comprise placing the infant atop the impedance
transformer pad within an NICU bassinet.
[0027] Also described herein are ultra wideband (UWB) baby
monitoring systems including: an impedance transformer pad having a
soft or resilient recumbent surface upon which a baby may rest; a
UWB antenna coupled to the impedance transformer pad and configured
to emit a UWB signal through the transformer pad and into the baby,
wherein the impedance transformer pad is configured to prevent
reflective loss of more than 50% of energy of the UWB signal; and a
processor in communication with the UWB antenna and configured to
monitor the baby when the baby is resting on the impedance
transformer pad. As mentioned, any of the systems and devices
described herein may also include UWB electronics as part of (or in
addition to) the processor.
[0028] The system may generally be configured to apply UWB signals
in a bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a different dielectric value. For
example, the system may be configured to apply UWB signals in a
bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a dielectric value, wherein the
thickness of each layer is less than or equal to one half of the
wavelength of the center frequency in the dielectric of that layer.
Specifically, the system may be configured to apply UWB signals in
a bandwidth having a center frequency, wherein the impedance
transformer pad comprises an impedance transformer region forming
the recumbent surface, the impedance transformer region having one
or more planar layers each with a dielectric value, wherein the
thickness of each layer is approximately one quarter or one half of
the wavelength of the center frequency in the dielectric of that
layer.
[0029] As mentioned above, the impedance transformer pad may be
configured to fit within a bassinet. Further, the impedance
transformer pad may be made of a non-toxic, hypoallergenic, and
water proof material.
[0030] Also described herein are bassinets configured for ultra
wideband (UWB) monitoring of an infant. For example, the bassinet
may include: a temperature-regulated bassinet enclosure having
walls and a lower surface; and at least one UWB antenna integrated
into the bassinet and configured to emit UWB energy into an infant
within the bassinet from the lower surface of the bassinet; wherein
the tower surface of the bassinet impedance matches to minimize
reflective loss of UWB energy between the MB antenna and the
infant.
[0031] In some variations, the lower surface of the bassinet
comprises an impedance transformer pad covering the UWB antenna so
that the UWB antenna emits UWB signals through the impedance
transformer pad. Any of the pads described above may be used; in
some variations the pad is integrated into the bassinet.
[0032] The UWB antenna may be configured to apply UWB signals in a
bandwidth having a center frequency, further wherein the tower
surface comprises an impedance transformer region covering the UWB
antenna, on which an infant may rest, wherein the impedance
transformer region has one or more planar layers each with a
dielectric value, wherein the thickness of each layer is less than
one half of the wavelength of the center frequency in the
dielectric of that layer.
[0033] In some variations, the UWB antenna may have a dielectric
approximately matched to the dielectric of the infant. For example,
the antenna may be configured to have an dielectric of
approximately 50. The outer surface of the dielectric may be
adapted so that it is comfortably for the infant to rest on top of.
For example, the upper surface of the antenna may be soft,
compliant, etc. In any of the variation described herein, the
bassinet may include a plurality of UWB antennas. Further, the
bassinet may include a processor (e.g., a UWB radar processor)
configured to receive signals from the UWB antenna to monitor the
infant, and/or UWB electronics for emitting and receiving UWB
signals and extracting physiological data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 shows one variation of an NICU bassinet with one
variation of a UWB monitoring system.
[0035] FIG. 2 shows one variation of a UWB monitoring system for an
infant, including an impedance matching pad.
[0036] FIG. 3A is a partial sectional view through one variation of
an impedance transformer pad. FIG. 3B shows a top view of the
impedance transformer pad of FIG. 3A.
[0037] FIG. 4A is a partial sectional view through another
variation of an impedance transformer pad. FIG. 4B is a top view of
the impedance transformer pad of FIG. 4A.
[0038] FIG. 5 shows another variation of a UWB monitoring system
for an infant, including an impedance matching pad having three
layers in the impedance matching region.
DETAILED DESCRIPTION
[0039] The Ultra-Wideband (UWB) monitoring systems described herein
may also be referred to as medical radar systems. These systems
allow for miniature, extremely low-power medical monitoring systems
that are safe and effective. UWB medical radar is an active imaging
technology similar in functional concept to ultrasound but is based
on electromagnetic, rather than sonic energy. In practice, the
systems described herein emit a micro-pulse of electromagnetic
energy, typically on the order of one hundred picoseconds in
duration, which propagates into the human body. As the energy
enters the body, small amounts of the incident energy are reflected
back to the device. The reflections are primarily a result of the
differences in dielectric properties of the underlying tissues and
organs, and can be detected as signals ("reflection signal
energy"). The reflection signal energy is then received and
processed using signal processing algorithms to extract information
on the location, size, and relative movement of the illuminated
tissues and organs. The short pulse duration also allows the radar
to `see` at much closer distances and with finer resolution than
more traditional radar systems. The energy transmitted to the
patient is typically reduced by unwanted reflections arising
between the UWB antenna and the patient's body ("reflection toss").
The one-way reflection loss in some prior art UWB systems may be as
great as 85-90% of the emitted energy. This loss results in lower
signal strength overall, and a significant decrease in the
reflected energy from the internal anatomical structures, making
extraction of the desired physiological data more difficult and
less accurate and reliable.
[0040] Thus, the systems described herein describe systems for
reducing the reflection loss of the UWB sensor system. All of the
UWB systems described herein employ extremely low power
electromagnetic energy capable of passing through materials such as
plastics, clothing, air and bone without needing direct skin
contact, conductive gels, electrodes or leads. The actual
transmitted power levels are well below thresholds set for
governmental safety standards, as well as below those used by
widely-adopted commercial wireless technology (e.g. cell phones,
Bluetooth devices, ZigBee devices, 2.4/5.8 GHz cordless phone,
wireless intercoms and baby monitors, and 802.11 wireless interact
equipment).
[0041] The infant in the NICU environment provides some unique
challenges and opportunities for non-invasive vital signs
monitoring. First, the NICU infant is typically a premature baby
and, thus the anatomical structures are very small, complicating
the ability to collect vital signs data using non-contact active
techniques. Second, a baby admitted to a NICU stays in a
specialized isolation bassinette which provides a protective
environment for the infant. The bassinette is typically an enclosed
structure, controlling temperature, light, humidity, and air flow.
They feature transparent sides that are typically made from clear
plastic. The tops are removable--either manually or motorized, and
often includes a switch that is used to signal when the top is open
or closed.
[0042] In some variations of the devices described herein, the
system includes a UWB medical radar to interrogate the volume of
the isolation bassinette, allowing non-contact monitoring of vital
signs including cardiac and respiratory activity, without touching
the infant. These bassinettes are typically made using transparent
plastic enclosure and a mattress pad--both of which are
non-conductive; UWB radar can operate through the walls or the
pad.
UWB Sensor Attached to Bassinet
[0043] In some variations, the systems described herein include
bassinets with integrated UWB monitoring systems. In this
variations, the UWB monitoring system and bassinet may be
configured together to optimize the signal transmission and
detection and therefore the efficiency of the monitoring system.
For example, the UWB antenna(s) may be arranged (and may be fixed
in positions) around the bassinet in a manner that optimizes the
detection of infant vital signs. In some variations the bassinet
may include one or more indicators for positioning the infant
within the bassinet in a manner that provides optimal monitoring.
In addition, the bottom of the bassinet may include a recumbent
surface that is configured to optimize the transmission of UWB
energy for sensing an infant. The UWB system may also be configured
to sense the presence/absence of an infant in the bassinet, and to
automatically monitor or turn off monitoring, and to emit or
provide various alerts based on the condition of the infant.
[0044] For example, FIG. 1 shows one variation of a bassinette
enclosure 101 in which one or more radar components (e.g.,
transmitter 103, receiver 105, or transceiver on the walls of the
isolation bassinette allow off-body detection and monitoring of
cardiac and respiratory activity. In FIG. 1, the NICU bassinet
includes a UWB sensor configured in a bistatic mode, with
transmission 103 at one end and reception 105 at the other end of
the enclosure 101). Thus, in general, the system architecture could
include monostatic, bistatic, or multistatic topologies with
locations including bassinette corners, sides, top, bottom, front
or rear surfaces. In one implementation, the components would be
secured to the exterior surfaces to minimize the potential of any
physical interaction with the infant. However, in some variations
it may be advantageous to mount the radar components inside the
bassinette--e.g. one or more corners, to provide a wider search
area. The integrated cover switch can be used to disable the radar
when the top cover is open.
[0045] In some variations, the system includes a plurality of UWB
transmitter/receivers positioned in predetermined locations within
the bassinet. The transmitter, receiver or transceiver may be
arranged in a variety of configurations. In one variation, the UWB
components are located in an interior corner (e.g., co-located
transmitter and receiver operated in monostatic mode).
Alternatively the UWB components may be located in any two opposite
interior corners with separate transmitter and receiver operated in
bistatic mode. In some variations, the UWB components are located
on the exterior short side of the bassinet with a co-located
transmitter and receiver operated in monostatic mode. In some
variations the UWB components are located in opposite exterior
short sides with separate transmitters and receivers operated in
bistatic mode. In some variations, UWB components are located on an
exterior long side with co-located transmitter and receiver
operated in monostatic mode. Alternatively, the UWB components may
be located on opposite exterior long sides with separate
transmitters and receivers operated in bistatic mode. In some
variations the UWB components may be operated on adjacent exterior
long sides with separate transmitters and receivers operated in
bistatic mode. In general, combination of three or more adjacent
exterior long sides with separate transmitter and receiver may be
operated in multistatic mode.
[0046] In addition to the variations just described, the bassinet
may be configured so that UWB components (e.g., transmitter,
receiver, or transceiver) form part of or are coupled to a
recumbent surface (such as the bottom of the bassinet or a pad for
the bottom of the bassinet) which may be impedance matched as
described herein. This may further enhance the UWB signal
transmission/reception and therefore the reliability and operation
of the monitor. If impedance matching as described herein is not
performed, a substantial amount of energy may be lost between the
UWB antenna and the boundary of the infant's body (as much as
85-90%), resulting in a substantial decrease in efficiency and a
loss of reflected energy from internal anatomic structures, making
extraction of desired physiological data more difficult, less
accurate and less reliable.
[0047] In general, a plurality of UWB transmitter, receivers and/or
transceivers may be used. These elements may be multiplexed or used
as part of a phased array. Examples of arrangements of phased
arrays of UWB antenna are illustrated in US 2003/0090407 (specific
to the use of such arrays for imaging).
[0048] In some variations the recumbent surface (e.g., bottom of
the bassinet onto which the infant is directly placed) is flush
with the outer surface of the one or more UWB antenna (transmitter,
receiver and/or transceiver), even without an intermediate
impedance transformer pad, such as those described below. In such
cases the outer surface of the antenna, is specifically configured
(1) so that the infant may be placed directly atop it without
discomfort or risk of damage to the infant or the antenna (e.g., it
may be formed of a soft or resilient material), and the antenna
itself may be adapted to have a dielectric value approximating the
dielectric value of the infant's body (e.g., approximately 50).
[0049] One advantage of operating a UWB sensor(s) in an isolation
bassinette is that the structure of the bassinet is physically
bounded on all sides. The bassinet represents a constrained volume,
and thus there is a finite range where the target--the infant, can
be located in the bassinette. The system may be calibrated during
installation or prior to placement of the infant in the bassinette
to optimize the radar range and characterize the empty bassinette.
This calibration data could then be used to create a filter that
represents the empty bassinette. Once the infant is placed in the
bassinette the filter would operate on the radar returns, producing
an optimized signal that enhances the presence and motion of the
infant, minimizing the potential for detection of false
positives.
Impedance Transformer Pad with Integrated UWB Sensor
[0050] Any of the systems described herein may include a recumbent
surface with integrated UWB components that is configured to match
and/or optimize the impedances between the UWB antenna and the
infant, and thereby substantially reduce reflection toss. In
general, the recumbent surface may be a pad, table, platform,
mattress, cushion, blanket, or the like, on which the infant is
configured to lie, sit, or recline, where the recumbent surface
acts as an interface between the UWB antenna and also acts as an
impedance transformer to minimize reflection and improve energy
transfer between the antenna and the infant.
[0051] For example, the sleeping pad in a NICU bassinette may be
adapted to be (or include) an impedance transformer pad coupled to
the UWB antenna(s) for monitoring the infant. NICU bassinette pads
are typically made of high density foam rubber with a vinyl coating
and are primarily designed for comfort. Such foamed pads are
typically very lossy, at least in part because of the presence of
air pockets within the foamed material, so that if the foam pad
were placed between a UWB antenna and the infant, much of the UWB
energy applied would be lost in reflection or scattering. An
impedance transformer pad may be configured to avoid the toss of
reflection white maintaining comfort. In addition to providing a
comfortable surface, the pad could be optimized to work with the
UWB medical radar to optimize the energy transfer between the radar
and the infant, which may be particularly important given the small
size of the anatomical targets in the infant. Thus, the composition
of the pad and the thickness of the pad between the radar
antenna(s) and the surface of the pad may be configured to act as
an impedance transformer. The UWB sensor(s), including
transmitters, receivers and/or transceivers, may be integrated into
an impedance transformer pad, and the impedance transformer pad may
be placed beneath the infant, including on top of an existing
bassinet pad/mattress or in place of such a pad.
[0052] The impedance transformer surfaces described herein may be
referred to herein as impedance transformer pads or, for
convenience as simply "pads", although any appropriate surface (not
limited to a mattress-type pad), may be used. Such alternative
embodiments, including blankets, pillows, seats, seat covers,
garment, mattress covers, etc. configured as impedance transformers
may also be referred to as impedance transformer pads, impedance
matching pads, impedance transformers, or they may be referred to
impedance transformer structures, where the structure refers to the
form of the embodiment, e.g., blanket, pillow, seat, etc.
[0053] An impedance transformer pad may be used to efficiently
transfer energy from one medium to another (e.g., the antenna to
the infant) by minimizing reflections of the UWB energy due to
impedance mismatch between the two mediums. In general, for
non-conductive, non-magnetic materials, the relative dielectric
constant of the two mediums (e.g., between the antenna and the
subject) is the parameter of interest for this purpose.
[0054] In general, an impedance transformer pad may be formed of
one or more materials (layers) interposed between the outer surface
(antenna surface) of the UWB antenna and the outer surface
(recumbent surface) of the pad onto which the patient will rest.
These impedance transformer layers of the pad are chosen to
efficiently convey UWB energy in a predetermined bandwidth between
the antenna surface and the recumbent surface by controlling the
thickness and the dielectric properties of the transformer
layer(s).
[0055] In theory, a simple single layer impedance transformer may
be fabricated from a material with a dielectric value that is the
geometric mean of the two primary mediums on either side of the
transformer (e.g., the antenna and the infant), and have a
thickness that is an odd multiple of the fundamental wavelength of
the energy. Impedance transformer pads of increasing complexity may
also be used, in which the pad include multiple layers of material
having different dielectric constants and specific thicknesses, as
described in greater detail below.
[0056] Although a more exact determination of the thickness and
dielectric composition of the impedance layer(s) of the impedance
transformer pad may be calculated as taught herein and described in
greater detail below, in some variations impedance transformer pads
having one or more layers may be generally described as having an
impedance transformer region (e.g., the region between the
transmitting/receiving surface of an antenna and the recumbent
surface) with a thickness between 0.4 cm and 7 cm (e.g., 0.5 cm to
5 cm, or in some variations 0.5 to 7 cm), where at least one planar
layer of this impedance transformer region has a dielectric between
about 5 and about 20. For example, based on the theoretical
calculations and considerations described below, a typical
impedance transformer pad may include an impedance transformer
region formed of one or more (planar) layers of a homogenous
material; the thickness of the impedance transformer region,
between the outer surface of the pad (e.g., the surface contacting
the infant) and the emitting/receiving surface of the antenna is
typically within the range of about 0.4 cm to about 7 cm, and at
least one layer of material in this region has a dielectric
constant between about 5 and about 20.
[0057] Such general impedance transformer pads (having thicknesses
and dielectric properties in the ranges described above) may
sufficiently minimize reflection loss of the UWB signals between
the UWB antenna(s) and the infant's body to substantially increase
the efficiency of energy transferred between the two, and thereby
the increasing the energy reflected from internal structures within
the patient, increasing the strength of the received signal and the
accuracy of the system. In operation, the impedance transformer
pads described herein may reduce one-way reflective losses between
the antenna and the subject to less than 50%.
[0058] In the context of the monitors described herein, the primary
mediums in the NICU bassinet are the radar antennas and the infant;
thus, the transformer material may be selected to have a relative
dielectric constant that is the geometric mean of these two
mediums. The impedance transformer pads may therefore be configured
so that the thickness of the pad is controlled and matched to the
fundamental wavelength(s) of the energy of the UWB sensor system,
and the material composition of the impedance transformer pad may
be controlled so that the materials chosen have a dielectric value
that is within a range (e.g., the geometric mean of the antenna and
the infant) of optimal values.
[0059] An impedance transformer pad may be configured to have a
thickness within an optimal range based on the antenna dielectric
(assuming an average patient dielectric and the bandwidth of the
UWB signal, and a dielectric (or multiple dielectrics in the case
of layered pads) within an optimal range also based on the antenna
properties and the bandwidth of the UWB signal. The optimal ranges
of the thickness and dielectric(s) may be determined by calculation
based on the principles described in greater detail below. In
addition, the impedance transformer pads may also include one or
more integrated UWB antenna for transmitting and/or receiving the
UWB probe signals. Such components may be integrated on the back
(e.g., non-patient contacting) side of the impedance transformer
region of the pad, and/or integrated within the impedance
transformer pads. For example, a pad may include one or more
backing layers in which the antenna(s) are embedded beneath the
impedance transformer region. In the discussion below, the
impedance transformer region refers to the region of the pad
between the outer (emitting and/or receiving) surface of the
antenna(s) and the outer surface of the pad on which an infant may
lie (recumbent surface).
[0060] As mentioned, the optimal thickness of the impedance
transformer region of the pad may depend on the bandwidth of the
UWB signal applied by the system and the dielectric properties of
the impedance transformer region of the pad. The dielectric(s) of
the impedance transformer region of the pad may depend on the
dielectric values of the antenna and of the patient, and in the
case of impedance transformer regions having multiple layers, the
dielectric values of each layer may also be based on the dielectric
values of the other layers of the impedance transformer region.
[0061] FIG. 3A shows one variation of an impedance transformer pad
303 including an impedance transformer region 305 formed of a
single layer. Beneath the impedance transformer layer is at least
one UWB antenna(s) 307. The UWB antenna(s) may be planar antenna
and may be configured as emitters, receivers and/or transceivers.
The UWB antenna is coupled (e.g., via a cable 308) to a processor
309 which may form part of the UWB monitor system. The system may
include the pad, antenna(s), and processor. The processor may
analyze and/or output sensing data based on the UWB signals from
the antenna. Additional UWB electronics may also be included. For
example, of the systems and devices described herein may also
include UWB electronics that are separate from or incorporated into
a processor. These UWB electronics generally are configured to
generating a UWB signal for transmission, and to aid in processing
UWB signals (reflected signals) received the by the UWB antenna(s).
UWB electronics may include signal generators, D/A and A/D
converters, timing circuitry, comparators, amplifiers, filters, and
the like. For example see U.S. Pat. No. 7,725,150, U.S. patent
application Ser. No. 12/765,680, published as US 2010/0274145A1,
and U.S. patent application Ser. No. 12/749,861, published as US
2011/0060215A1. UWB electronics may be configured to generate the
UWB signal(s) for emitting from the antenna(s) and processing the
received signal (reflections) to extract physiological data.
[0062] In FIG. 3A, the pad also includes a backing region 311 which
may also act as a substrate on which the antenna(s) and impedance
transformer surface sits. The backing region may be a foamed
material, or any other appropriate material, and may have
dielectric that is mismatched with the dielectric of the impedance
transformer surface above it. In FIG. 3A, the impedance transformer
surface may have a thickness in the range of between about 0.4 cm
and 7 cm (e.g., 0.5 cm to 5 cm, or in some variations 0.5 to 7 cm).
This impedance transformer surface is formed of a homogenous
material having a dielectric generally between 5 and 20. In some
variations this impedance transformer surface is made from a
solution of silicone that has been adjusted to have the desired
dielectric value by adding additives (e.g., salts, etc.). In this
example, the outer impedance transformer layer is laminated
directly on to the backing layer and antenna(s). For comfort, the
pad may provide support, yet not be excessively hard/rigid, in
order to avoid creating sores at pressure points on the body. The
pad may also be easy to clean, non-toxic, hypoallergenic, and water
proof. Thus, in some variations the outer impedance transforming
region of the pad may be fabricated from silicone gels. As
mentioned, these gels may be doped with common materials, e.g.
carbon black or barium titanate, to create layers with dielectrics
within the desired range (e.g., <30).
[0063] The overall shape of the pad, including the number and
orientation of the UWB antennas, may be varied, FIG. 3B illustrates
one variation of a UWB transformer pad for use with a UWB
monitoring system that has four antenna arranged across a midline
region of the pad. FIG. 3B shows a top view looking down on the
outer surface of the impedance transformer region; the antenna 307,
307', 307'', 307''' beneath this region are indicated by the dashed
boxes. In some variations the pad may also include markings
indicating the preferred positioning for a patient (e.g., infant)
lying on the pad. In FIG. 3B this is illustrated by the shaded
outline of the infant 321. This may be indicated on the pad
visually, or the pad may simply mark (e.g., in color and/or text)
the location of the antennas and/or the desired orientation of the
patient. The pad may be any appropriate size. For example, the pad
may be a one foot by one foot square, or it may be smaller or
larger. The type and size of the LAB antenna may also be adjusted;
in this example, the antennas are 2 inches long.
[0064] The range of values for the thickness and dielectric of the
impedance transformer region provided above for the example shown
in FIGS. 3A and 3B are general, however more precise values may be
calculated given the properties of the antenna and assuming a
bandwidth of the UWB signal. For example, in one variation of an
impedance transformer pad having a single layer impedance
transformer region of the pad, the thickness of the transmissive
layer of the pad will typically be centered around about 1/4 of the
center frequency (e.g., the geometric mean of the bandwidth) of the
applied UWB signals. A range of thicknesses may therefore be
determined as optimal or appropriate from this estimate. To
approximate these values, the following assumptions are made: (1)
the desired transmission bandwidth is approximately 3 GHz to 6 GHz;
(2) the characteristic impedance of the antenna is approximately
377 Ohm (air), and the relative dielectric constant is 1; (3) we
assume that the patient's relative dielectric constant is
approximately 50 (which is particularly accurate for bodies having
a low fat content, such as preemies).
[0065] Assuming the bandwidth of the UWB signal is approximately
3-6 GHz, the geometric mean is approximately 4.25 GHz, which may be
referred to as the center frequency (f.sub.c). In this single layer
example, an approximate optimized dielectric for the single layer
may be based on the mean value between the dielectric of the
antenna and the target (e.g., the aggregate dielectric of the
infant's body). For example: for a single layer quarter wavelength
pad, the relative dielectric constant of pad is the geometric mean
of the dielectric of air (.di-elect cons..sub.air) and of the
patient (.di-elect cons..sub.patient) or approximately 7.07
(.di-elect cons..sub.d). The thickness of the pad for the
quarter-wavelength case is therefore equal to one quarter of the
wavelength at the center frequency in the dielectric, or:
thickness of pad = .lamda. / 4 in the dielectric = c 4 f c d = 3 10
cm / s 4 .times. 4.24 e 9 c / s .times. 7.07 = 0.67 cm
##EQU00001##
(where c is the speed of light f.sub.c center frequency and
.di-elect cons..sub.d is the dielectric of the impedance
transformer region of the pad).
[0066] Thus, in this example, a pad such as the one shown in FIGS.
3A and 3B may be made using readily commercially available air
antennas (.di-elect cons..sub.air) for a bandwidth of 3-6 GHz, and
therefore has a thickness of the outer impedance transformer region
of approximately 0.67 cm (e.g. between 0.6 and 0.9 cm) and a
dielectric value for this region of approximately 7.07 (e.g.,
between 5 and 9). This outer impedance transformer region may be
formed of silicone that is doped with carbon black to achieve this
impedance value. The pad may also include a backing region formed
of foam rubber, and a plurality (e.g. 2, 3, 4, 5, 6, 7, 8, etc.) of
antenna abutting the impedance transformer region so that UWB
energy is directed toward the patient through the impedance
transformer region. A system including such a pad may include the
pad as described above (or in any of the other variations described
herein) and a processor and/or additional UWB electronics
communicating with the antennas in the pad; in some variations an
output (e.g., one or more of audible outputs, visual outputs,
electronic outputs, etc.) may also be part of the systems. The
processor may include a housing, and one or more inputs (e.g.,
touch screens, keypads, etc.) for receiving information. In some
variations the antenna may be directly coupled to UWB electronics
for generating the UWB signal and/or processing the received signal
reflections and extracting physiological data. For example the
antenna may be integrated with some or all of the UWB electronics,
or it may be connected to them, and the UWB electronics (and/or
additional processor) may be positioned separately from the pad, as
illustrated in FIG. 3A.
[0067] The presumed dielectric constant for the patient is based on
a reasonable value for preemies. Because premature infants do not
have as much body fat, their aggregate relative dielectric constant
is approximately 40 to 60. As described above, based on this range
of values, a single layer quarter wavelength transformer pad may be
formed at least in part of a material that has a relative
dielectric constant between about 5 and about 20 to efficiently
couple energy from the antennas to the patient. The antenna used
for the pads described herein may have a different dielectric value
(e.g., other than air) and may be optimized to couple energy from
the circuitry to a medium other than air, which may also reduce the
physical size of the antenna. Thus, based on the antenna variation,
optimal values for the dielectric constant of the impedance
transformer pads could be somewhat lower or higher, and may be
within the range, for example, of about 5 to about 25.
[0068] A single layer quarter wavelength impedance transformer pad
may be particularly useful with narrowband signals, though its
performance may degrade as the bandwidth of the signal increases,
as is the case with UWB radar. To compensate for this, multilayer
transformers pads may be used, and may be better suited to minimize
reflections across the desired portion of the spectrum. Exemplary
multilayer transformers pads may include a 2 layer
"quarter-quarter" transformer pad and a 3 layer
"quarter-half-quarter" transformer pad, where the quarter and half
references are with respect to the estimated wavelength of the
center frequency of the UWB monitor. Pads having more than three
layers for the impedance transformer region are also
contemplated.
[0069] For example, three exemplary variations of impedance
transformer pads are: quarter, quarter-quarter, and
quarter-half-quarter variations. The quarter-quarter is variation
may provide improved bandwidth and can be fabricated from materials
with dielectrics between those of the characteristic impedance of
the antennas and the dielectric of the patient. The
quarter-half-quarter may use a material for the half layer that has
a dielectric significantly above either of the other two (quarter
layers) for an improvement in bandwidth over the quarter and
quarter-quarter layer variations. Numerous other topologies,
including more than three layers, are possible. Typically, however,
the greater the number of layers, the larger associated materials
cost and manufacturing complexity; additional layers may, however,
provide a modest improvement in performance.
[0070] As an example, a three layer transformer
("quarter-half-quarter" transformer pad) may provide good
performance over a 100% bandwidth case, e.g. 3 GHz to 6 GHz.
Similarly, other transformer pad structures, including multiple
layers, can be employed to enhance energy transfer.
[0071] FIG. 5 illustrates one variations of an impedance
transformer pad that has an impedance transformer region formed of
three layers; a 1/4 wavelength layer, a 1/2 wavelength layer, and
1/4 wavelength layer. By having multiple layers, it may be possible
to expand the bandwidth over which the transformer pad effectively
moves energy. Each layer is designated by the fraction of the
center frequency (f.sub.c), e.g., 1/4 wavelength, 1/2 wavelength,
etc. as a function of the dielectric of the layer.
[0072] In FIG. 5, a UWB system includes an impedance transforming
pad having three layers: a quarter (1/4 wavelength) layer 501, a
half (1/2 wavelength) layer 503, and another quarter (1/4
wavelength) layer 504. Thus, this variation may be referred to as a
quarter-half-quarter wavelength impedance transformer pad, and
includes at least one integrated UWB antenna 505. As illustrated in
FIG. 2, the antenna may be a UWB planar antenna 505, and may
communicate with a UWB processor 509 (e.g., via RF cable 507 or
other means, including wirelessly). As mentioned above, additional
UWB electronics for generating the UWB signal(s) for transmission,
receiving the UWB signal reflections, and for processing the
reflections to extract the desired physiological data may be
included as part of the processor, or separately. Further these
features may be integrated with the antenna or separate from the
antenna and connected as mentioned above.
[0073] In general, pads of this variation may also fall into the
same range of values for the thickness and dielectric values of the
impedance transformer region described generally above, however
each layer may have its own characteristic dielectric value, and
specific thickness. The overall thickness may typically be between
0.4 cm and 7 cm (the aggregate thickness of all layers of the
impedance transformer region), and at least one layer of the
impedance transformer region may have a dielectric value between
about 5 and about 20.
[0074] For example, one variation of an impedance transformer pad
having a three layer quarter-half-quarter impedance transformer
region may be formed so that each layer has the following
dielectric and thickness values, which may be estimated. Referring
to the arrangement of FIG. 5 and making the same assumptions
mentioned above (e.g., an antenna having a .di-elect cons..sub.air
of 1, a bandwidth of 3-6 GHz and a patient having a .di-elect
cons..sub.body of 50), the values may be calculated as illustrated
below.
[0075] The half wavelength layer (layer 2) 503 may be formed of a
material that is selected for cost and/or ease of manufacturing. In
this example, assume that the dielectric (.di-elect cons..sub.d2)
is 5. Other materials, having other dielectric values (ranging from
1 to >50) may be used. Based on this value, the thickness may be
calculated as:
Thickness of layer 2 = .lamda. / 2 in the dielectric = c 2 f c d 2
= 3 10 cm / s 2 .times. 4.24 e 9 c / s .times. 5 = 1.58 cm
##EQU00002##
[0076] Similarly layer 3, which is the layer of the impedance
transformer region closes to the antenna has a relative dielectric
constant that is the geometric mean of air and layer 2, or
approximately 2.24 (e.g., the square root of .di-elect
cons..sub.air and .di-elect cons..sub.d2). Based on this
dielectric, the thickness of this layer is:
Thickness of layer 3 = .lamda. / 4 in the dielectric = c 2 f c d 3
= 3 10 cm / s 4 .times. 4.24 e 9 c / s .times. 2.24 = 2.64 cm
##EQU00003##
[0077] Layer 1 is the remaining layer closest to the outer surface
of the impedance transformer region, closest to the recumbent
surface. The relative dielectric constant of layer 1 (.di-elect
cons..sub.d1) is a function of dielectrics of the antennas, layer
3, and patient. It can be calculated using the equation:
3 2 * body a ##EQU00004##
where: [0078] .di-elect cons..sub.a=relative dielectric constant
associated with the antenna(s), [0079] .di-elect
cons..sub.3=relative dielectric constant of layer 3, and [0080]
.di-elect cons..sub.body=relative dielectric constant of patient's
body Thus, the relative dielectric constant of layer
[0080] 1 = 3 2 * body a = 2.24 2 * 50 1 = 15.84 . ##EQU00005##
based on this dielectric, the thickness of layer 1 can be
calculated as described above as:
Thickness of layer 1 = .lamda. / 4 in the dielectric = c 4 f c d 1
= 3 10 cm / s 4 .times. 4.24 e 9 c / s .times. 15.84 = 0.44 cm
##EQU00006##
[0081] Thus, the thickness of the impedance transformer region is
the aggregate thickness of all three layers (0.44 cm+1.58 cm+2.64
cm), 4.66 cm, and the dielectric constants are: 15.84, 2.24 and 5.
Pads such as those illustrated above having three layers (e.g.,
configured as Quarter-Half-Quarter pads) may be particularly
useful, as the bandwidth may be better than single or double layer
variations.
[0082] FIGS. 4A and 4B illustrate a double-layer variation of an
impedance transformer pad of a UWB system, configured as a
quarter-quarter transformer pad. In this example, the pad includes
an impedance transformer region 405 formed of a first layer 403 and
a second layer 401. In this example, the antennas 407, 407' abut
the second layer 401, and includes signal handling components 409,
409', which may include on-board circuitry (e.g., signal
processing) and/or communications circuitry for passing the signal
to other portions of the UWB system 409, which may include an
off-pad processor and/or UWB electronics. In some variations, the
processor and any additional UWB electronics may be integrated into
the pad.
[0083] FIG. 4B shows a top view of another variation of an
impedance transformer pad 400, similar to the variation shown in
FIG. 3B. In this example, the positions of two antenna are
indicated by the dashed boxes 404, 407' beneath the outer surface
of the pad. As mentioned, any appropriate number and positioning of
antennas allowing the UWB signal to reach an infant lying on the
pad may be used. Antennas which may be used as part of an impedance
transformer pad include planar structures (antenna), which may
minimize discomfort and are typically designed to couple energy
from the electronic circuitry to air.
[0084] In any of the variations of the impedance transformer pad
having impedance transformer regions formed of multiple layers, the
various layers may be laminated together. Thus, for example,
single, double, triple, or more layers may be used, as indicated.
In addition, one or more additional backing layers e.g., foam
backing layers) may be laminated or otherwise affixed to the
impedance transformer region.
[0085] In all of the variations illustrated above, the impedance
transformer region is formed as a planar layer extending across the
entire surface of the pad. In some variations the impedance
transformer region extends only over a sub-region of the surface of
the pad, which may be limited to just the region above the antenna
and between the antenna transmission/receiving surface and the
upper (recumbent) surface of the pad. In some variations the
impedance transformer region may be slightly larger than the
underlying antenna surface. Multiple such impedance transformer
regions ("islands") may extend across the surface of the pad over
top of each antenna; these discrete impedance transformer regions
may be surrounded by the same support layer material (e.g., foam
rubber, etc.) as beneath the impedance transformer region. Such
variations may be particularly useful where multiple types of
antennas having different properties (e.g., different dielectrics)
are used. In this variation, the different impedance transformer
regions may have a different number of layers or may have different
characteristic thicknesses and/or dielectrics.
[0086] Returning now to FIG. 2, another variation of an impedance
transformer pad configured as a quarter-quarter impedance
transformer pad with an integrated UWB antenna is illustrated. In
this example, the impedance transformer pad includes two layers
(first layer 201 and a second layer 202) and an integrated planar
UWB antenna 205 which is attached to the underside of the impedance
transformer pad. The UWB antenna is shown connected via RF cable
207 to a UWB processor 209, which may be located outside of the
bassinet. Additional UWB electronics (not shown) may also be
included (as part of or in addition to the UWB processor) for
generating the signal(s), conditioning the received signal(s)
and/or extracting information from the received signal(s).
Alternatively, in some variations, the processor 209 and other UWB
components (e.g., electronics) may be located within the bassinet
or may be coupled wirelessly to the antenna 205. In some
variations, the processor controls the transmission and reception
of UWB signals and may provided signal processing and analysis of
the patient's (e.g., infant's) vitals. Outputs, including alarms,
storage of signals (including alarms, etc.), and transmission of
data from the UWB system may also be coordinated and controlled by
the processor.
[0087] The impedance transformer pads described herein may address
problems and inefficiencies present in other UWB sensor systems,
particularly those used for recumbent patients. As mentioned above,
"mattress" UWB sensors for monitoring the health of an individual
in a bed or chair have been described, but have not been optimized
to improve radar performance. Optimization would not be possible
when UWB systems are used with standard mattress materials. For
example, foam rubbers used in most mattresses are made from
styrene-butadiene or polyurethane, which have relative dielectric
constants in the range of 2 to 4 prior to being converted into
foam, outside of the optimal dielectric range. To create foam
rubber, the base rubber compounds have gas injected into them
during manufacturing to decrease hardness and improve comfort as
well as increase insulating properties, and the introduction of gas
reduces the dielectric constant of these materials proportionally
to the percentage of gas by volume used in the product. Also, gas
bubbles cause scattering, reducing the performance of the radar.
Both the miss-match of the extremely low relative dielectric
constants and scattering by gas bubbles make traditional foam
rubber mattress materials unsuitable for use in an impedance
transformer as described herein. Further, the thicknesses of
mattresses are much larger than the range of thicknesses described
herein for optimal configuration of an impedance transformer
pad.
Signal Processing
[0088] Data from the UWB medical radar system may be processed to
provide appropriate outputs, including cardiac wall motion
waveforms or indicators, cardiac rate waveforms or indicators, and
respiratory waveforms or indicators as well as refined data derived
from these basic data types. Programmable alarms may be set by
caregivers to alert them of changes to the infant's condition. The
resulting data could be displayed on a local monitor or a
centralized monitor. With connection to the hospital network, the
data could be accessed by healthcare professionals remotely.
[0089] In addition to detection of basic vital signs, including
cardiac and respiratory activity, the UWB sensor systems described
herein may be programmed to detect other motions, including heads
turns or limb movement, and could be configured so that the absence
of age-appropriate motion over a pre-defined period of time
triggers alarms, prompting caregivers to check on the infant. For
example, in some variation the processor may receive one or more
inputs that may help it to monitor the infant. For example, the
processor may receive the infant's age and use this information to
appropriate toggle alerts or analysis information. For example, the
amount of motion typically observed in pre-mature babies is a
function of gestational age at the time of birth. For example, a
baby born at 28 weeks or less does not move much, with motion
limited to fist clinches or limb flexes. Between 29 and 32 weeks of
gestation, motion is jerky and can include head turns. At 35 weeks,
the baby is capable of a variety of motions, including tucking into
the fetal position. In addition, other sensors, such as temperature
(e.g., infrared) sensors, pressure sensors, or the like, could be
integrated to provide enhanced monitoring capabilities.
[0090] In general, the UWB signals generated and proceed to
determine vital properties (e.g., heart rate, body movements, and
the like) may be handled as previously described, for example, in
U.S. Pat. No. 7,725,150, U.S. patent application Ser. No.
12/765,680, published as US 2010/0274145A1; and U.S. patent
application Ser. No. 12/749,861, published as US
2011/0060215A1.
[0091] The system may further be configured to integrate with one
or more other hospital monitors, records, or hospital control
systems. Thus, these monitors may interface with existing infant
monitoring systems. For example, the processor may allow
communication/interface with other monitoring or hospital patient
care systems.
[0092] In addition, the systems and devices described herein may
include automatic on/off or other power management functions, which
may also be used to toggle alerts and data collection. For example,
the UWB sensors/impedance transformer pads described herein may
determine when the patient (e.g., infant) is laying on the
recumbent surface (e.g., impedance transformer pad). Since these
devices efficiently transfer energy between the UWB antenna and
patient, the voltage standing wave ratio (VSWR) will reflect when
the patient is not present on the pad. This is relatively simple to
detect in the sensor and can be used as a way to tell when a
patient is present, allowing the radar to go into a "sleep" mode
when the patient is gone. In sleep mode, the radar may occasionally
"wake up" to test for the presence of the patient and when
detected, resume full operation. The system may also be set up to
trigger an alarm if the VSWR ratio indicates that the patient has
moved off of the impedance transformer pad.
[0093] In general, the impedance transformer pads described herein
may be adapted for comfort, as the infant may be placed directly on
them. Furthermore, these pads may be well adapted for use as a
sleeping surface, and particularly for an infant sleeping surface.
For example, the impedance transformer pads may be flexible,
pliable, soft, and/or resilient. The pad may be configured to be
easily removed (and may therefore contain coupling/uncoupling
features whereby the integrated UWB antenna components in the
impedance transformer pads may be uncoupled and reconnected to the
rest of the UWB monitoring system (including one or more
processors, displays, etc.). The impedance transformer pads may
also be configured so that it can be easily and safely washed or
laundered and/or sterilized. Thus, the impedance transformer pad
may include a waterproof or water resistant outer coating, and the
antenna components may be protected from corrosion or degradation
by washing, or by contamination from blood, urine, or the like.
[0094] Any of the impedance transformer pads described above may
also include one or more indicators, including markings,
illuminated regions (e.g., LEDs, etc.) indicating the optimal
placement or positioning of the subject on the pad, and/or the
orientation of the pad on or relative to the bassinet, bed, seat,
etc. For example, the impedance transformer pad may include a
color-coated or otherwise labeled region indicating how the infant
is to be oriented when laying on the pad, such as where to
optimally position the head and torso.
[0095] Although the variations of the UWB monitoring systems
described above are illustrated in the context of infant/NICU
embodiments, these systems and devices may be used and/or adapted
for use by non-infant (including adult or veterinarian) use. For
example, a impedance transformer pad may be used on top of an
adult-sized mattress for use with one or more adult patients,
including gerontological or hospital use.
[0096] Other variations of the devices and systems described herein
include, in particular, garments, seats, and/or blankets configured
as impedance transformer pads for use with UWB monitoring systems.
Such impedance transformer pads may be configured with integrated
antennas and the appropriate thickness and dielectric properties.
For example, an impedance transformer pads may be configured as
part of car seat that may be used over an existing car seat and may
optimally provide feedback to a mobile UWB monitoring systems. In
other variations, a blanket or bedcovering may be configured as an
impedance transformer pad, which may be applied over a patient, or
beneath them as a mattress pad or the like.
[0097] In particular, variations of the systems described here may
be used for home (rather than just NICU) monitoring. For example,
parents, particularly those of infants with medical problems, are
often concerned about the undetected onset of emergent medical
problems when their child is asleep. It may therefore be desirable
to use the devices described herein for active baby monitoring.
Currently available baby monitors include traditional audio and
video monitors as well as crib pads with motion sensors capable of
detecting motion and respiration. The systems described above could
be used to provide a monitoring able to detect cardiac activity and
other vital signs, including gross body motion. Simplified
variations of the system may be adapted for home use, including
systems limited to one or two radar components, such as a single
transceiver, a separate transmitter and receiver, or two
transceivers. These systems may include an impedance transformer
pad as described above, or may be configured to mount or hang from
the child's crib. A communications link may be used to transmit
infant data to a small receiving station that the parents could
carry with them or place nearby.
[0098] While the foregoing has been with reference to particular
embodiments of the invention, it will be appreciated by those
skilled in the art that changes in these embodiments may be made
without departing from the principles and spirit of the invention,
the scope of which is defined by the appended claims. The
intention(s) described herein are intended to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the appended
claims. The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations
are intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
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