GB2500000A

GB2500000A - Microwave monitoring using an electrically conductive textile

Info

Publication number: GB2500000A
Application number: GB1203846.9A
Authority: GB
Inventors: Al-Shamma A Ahmed; Andrew Shaw; Alex Mason; Stephen Wylie
Original assignee: Liverpool John Moores Univ
Current assignee: Liverpool John Moores Univ
Priority date: 2012-03-05
Filing date: 2012-03-05
Publication date: 2013-09-11
Anticipated expiration: 2032-03-05
Also published as: GB2500000B; GB201203846D0

Abstract

Physiological information is gathered from a subject using an electrically conductive textile 11 interrogated with microwaves. The textile 11 has at least one property measurable at a microwave frequency. The textile 11 acts as a sensor by having microwave properties affected by flexure or extension for example. Alternatively the fabric 11 may act as an antenna for a sensor (14, fig. 1) attached to the fabric 11. Monitoring may be wired or wireless. The textile 11 may be made into clothing 15 to be worn by the subject, and may be used for monitoring personnel in hazardous environments, athletes and other sportspeople.

Description

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Microwave Monitoring

5 This invention relates to microwave monitoring, particularly, but not exclusively, to monitoring of biological conditions and functions.

Measurements of various bodily conditions are made by attaching electrodes to locations on the body and picking up electrical signals, as, for example, by electrocardiography. 10 Other measurements may be made by strain gauges subject to forces generated, for example, by the expansion and contraction of the chest, which may be used to monitor breathing.

Such measurements usually involve an electrical connection between the sensors and a 15 measuring or monitoring instrument, to which the subject is 'hooked up'. However, there is growing interest in portability and freedom from physical constraint, enabling a patient, for example, to move around freely or an athlete to be monitored while performing. Moreover, electrodes and sensors can be incorporated in garments, as taught inter alia in GB2473478, US2009/0203984, and US2009/0013728. W02004/100784 and 20 GB2456822 disclose fabrics or garments involving electrically conducting threads of which electrical properties change when subject to deformation as through bodily movement. Electrically conductive threads in fabrics or garments may be used as part of a circuit connecting sensors to measuring devices.

25 The present invention provides for greater freedom of movement and ease of monitoring.

The invention comprises a method of gathering information from a subject by measuring at least one property of an electrically conductive textile at a microwave frequency.

30 By 'textile' is meant a yarn or thread or a fabric made from or incorporating an electrically conductive yarn or thread, whether woven, knitted or non-woven, or a fabric, which may be a film, incorporating an electrical element that has measurable properties at microwave frequencies. Such textiles may be flexible or drapable in such a way that microwave properties are affected by flexure or extension, or may simply act as a 35 microwave antenna in a circuit of which a microwave measurement depends on the condition of a sensor, flexibility or drapability allowing the textile to be fashioned as or incorporated into a garment or other wearable item such as a wristband or sensor patch.

The textile may be connected by a cable, for example, a coaxial N-type connection to a 40 microwave generator and/or to an analyser such as a vector network analyser or a spectrum analyser to generate and/or analyse its microwave response. It may be used, therefore, as a microwave receiver or a microwave transmitter, or, without physical connection, both as receiver and transmitter, picking up microwave radiation beamed at it, for example, and emitting microwave radiation which is picked up by a receiver.

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The electrical properties of the textile, such as its conductivity and, in the case of a fabric, its permittivity, may change in response to variables such as stretch, pressure,

temperature and shape, and the textile may itself constitute a sensor, a value associated with which being communicated by transmitted and/or reflected microwave radiation.

The invention also comprises an electrically conductive textile configured as a microwave transmitter, reflector and/or receiver incorporating a sensor, changes in a value associated with which measurably affect a microwave spectrum associated with the fabric.

The textile may comprise a garment, such as a vest, or an armband or wristband, or a conductive thread incorporated in a garment or a fabric.

The invention also comprises such a textile in combination with microwave generation, reception and analysis equipment.

The equipment may operate in a range of frequencies from 9kHz to 20GHz.

Measurement may be made at more than one frequency.

Measurement may be made at a frequency in the region of a resonant frequency of the textile, slight variations in the resonant frequency resulting in marked variations in a reflected or transmitted microwave signal for good sensitivity.

Methods of gathering information and textiles and equipment used therein according to the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a view of a fabric with electrically conductive elements;

Figure 2 is a close-up of an electrically conductive element of Figure 1;

Figure 3 is a view of a garment incorporating microwave-responsive sensors;

Figure 4 is a diagrammatic illustration of a microwave generator/receiver/analyser set-up.

The drawings illustrate methods of gathering information from a subject by measuring at least one property of an electrically conductive textile at a microwave frequency.

Figures 1 and 2 illustrate a fabric 11 incorporating electrically conductive threads 12.

The fabric 11 is a knitted fabric, principally of elastomeric threads 13, covered with polyester fibres. The conductive threads 12 are of polyethylene multifilament yarn coated with a nanolayer of silver, copper or other high conductivity metal.

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When the fabric 11 stretches, electrical properties of the conductive threads 12 will change. One of the conductive threads 12 is connected to a pressure sensor 14, which has an electrical output, serving as an aerial therefor.

5 Figure 3 illustrates a vest 15, which incorporates patches 16 of fabric such as fabric 11.

Figure 4 illustrates a microwave set-up for making measurements of properties of a textile 11, comprising a microwave generator 41 and a microwave receiver/analyser 42. These are capable of operation over the frequency range 9kHz to 20GHz.

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The generator 41 can be connected to the textile 11 by a cable 43, typically a coaxial cable with an N-type connector attached to a terminal 17 attached to a conductive thread (Figure 1), and the receiver/analyser 42 may be similarly connected. However, either the generator 41 or the receiver 42 or both may be wirelessly connected, to give a wearer of a 15 garment improved freedom of movement/activity.

Microwave power of the order of lmW can be effective for communication between generator and textile and receiver and textile over distances of the order of a few metres while being at a safe level for subjects and attendant personnel.

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The arrangement may be used for patient monitoring, as, for example, for ECG monitoring, or blood pressure monitoring, using, for example, stretchable threads in a sleeve, or temperature monitoring, using threads with a high rate of change of resistance with temperature, as taught for example in W02009001108. The arrangement may also 25 be used for monitoring personnel in hazardous environments to give indication of ambient conditions, and for monitoring athletes and other sportspeople in training or during actual performance.

Provision for cable connection might be used for calibration.

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Particularly accurate measurement may be made if the measuring frequency is close to a resonant frequency of the textile. At such frequency, the reflected or transmitted radiation may be at a maximum or minimum, changing rapidly as the measurement frequency or the resonant frequency changes.

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Claims

Claims:

1 A method of gathering information from a subject comprising measuring at least one property of an electrically conductive textile at a microwave frequency.

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2 A method according to claim 1, in which the textile comprises a yarn or thread or a fabric made from or incorporating an electrically conductive yarn or thread.

3 A method according to claim 1, in which the textile comprises a film,

10 incorporating an electrical element that has measurable properties at microwave frequencies.

4 A method according to any one of claims 1 to 3, in which the textile is flexible or drapable in such a way that microwave properties are affected by flexure or extension.

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5 A method according to any one of claims 1 to 4, in which the textile acts as a microwave antenna in a circuit of which a microwave measurement depends on the condition of a sensor, or of flexibility or drapability of the textile.

20 6 A method according to any one of claims 1 to 5, in which the textile is fashioned as or incorporated into a garment or other wearable item such as a wristband or sensor patch.

7 A method according to any one of claims 1 to 6, in which the textile is connected 25 by a cable, for example, a coaxial N-type connection to a microwave generator and/or to an analyser such as a vector network analyser or a spectrum analyser to generate and/or analyse its microwave response.

8 A method according to any one of claims 1 to 7, ion which the textile is used, as a 30 microwave receiver or a microwave transmitter, or, without physical connection, both as receiver and transmitter, picking up microwave radiation beamed at it, for example, and emitting microwave radiation which is picked up by a receiver.

9 A method according to any one of claims 11 to 8, in which the electrical 35 properties of the textile, such as its conductivity and, in the case of a fabric, its permittivity, change in response to variables such as stretch, pressure, temperature and shape.

10 A method according to any one of claims 1 to 9, in which the textile itself

40 constitutes a sensor, a value associated with which being communicated by transmitted and/or reflected microwave radiation.

11 An electrically conductive textile configured as a microwave transmitter, reflector and/or receiver incorporating a sensor, changes in a value associated with which

45 measurably affect a microwave spectrum associated with the fabric.

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12 A textile according to claim 11, comprising a garment, such as a vest, or an armband or wristband, or a conductive thread incorporated in a garment or a fabric.

13 A textile according to claim 11, in combination with microwave generation, 5 reception and analysis equipment.

14 A combination according to claim 13, operating in a range of frequencies from 9kHz to 20GHz.

10 15 A combination according to claim 13 or claim 14, in which measurement is made at more than one frequency.

16 A combination according to any one of claims 13 to 15, in which measurement is made at a frequency in the region of a resonant frequency of the textile, whereby slight 15 variations in the resonant frequency result in marked variations in a reflected or transmitted microwave signal for good sensitivity.