EP4044363A1

EP4044363A1 - A wireless communication device

Info

Publication number: EP4044363A1
Application number: EP21157066.8A
Authority: EP
Inventors: Mart Kornelis-Jan TE VELDE; Timon Rutger Grob
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2021-02-15
Filing date: 2021-02-15
Publication date: 2022-08-17

Abstract

A wireless communication device (10) has a printed circuit board (18), a flexible antenna (22), and a wireless communications circuit within a housing (12). The flexible antenna (22) follows a path from a location where it connects to the printed circuit board (18) towards an inner surface of a cover (16) of the housing (12). Most of the antenna (22) is thereby spaced from the printed circuit board (18) while the antenna (22) has a simple connection to the printed circuit board (18).

Description

FIELD OF THE INVENTION

This invention relates to wireless communication devices, such as wearable sensors that report sensor data wirelessly.

BACKGROUND OF THE INVENTION

Wearable health patches with wireless sensor data communication are well known, for example for measuring heart rate, respiration rate, activity levels, and posture (e.g. to detect a fall).
Many different sensor types are possible, such as skin conductivity, PPG measurement, motion measurement using accelerometers etc.
Examples of suitable wireless communication systems are WiFi, Bluetooth, LoRa, 4G and 5G. However, any desired wireless communications modality may be integrated into a sensor.
The wireless communication requires integration of an antenna into the sensor device. An antenna may for example be printed on the circuit board that carries the main sensor components and circuitry. The antenna may instead be a ceramic chip antenna, which is mounted on the printed circuit board as a surface mount component. The antenna is designed for miniaturization and accordingly will compromise on efficiency. As a result, there will be a reduced effective range. Thus, miniaturized planar antennas as used in wearable sensors do not give optimal range and power consumption. Whip or stub antennas are more efficient, but they are not suited for wearable biosensors because of their size.
One particular issue resulting in the low efficiency mentioned above, and hence limited range and high power consumption, is the proximity of the antenna to the body against which the sensor is worn, for example where the sensor signals are collected.
It is known to improve the efficiency by mounting the antenna away from, and typically above, the main printed circuit board. This gives more room for the antenna as well as positioning the antenna further away from the body. The antenna may for example be formed at a top of the sensor housing, whereas the printed circuit board is mounted at a bottom of the sensor housing.
However, electrical connections are then needed between the slightly remote antenna and the printed circuit board, and these connections add cost and complexity as well as requiring enhanced positional accuracy in the assembly process. Spring loaded connections (e.g. a spring-loaded pogo pin construction) may be used, or other contact spring constructions (e.g. conductive tracks formed on pillars of the housing). These connections may also exert an additional force on the printed circuit board, which may not be desired.

SUMMARY OF THE INVENTION

There is therefore a need for an improved antenna configuration for use in a wireless communication device. The invention is defined by the independent claims. The dependent claims define advantageous embodiments.
According to examples in accordance with an aspect of the invention, a wireless communication device comprises:

a housing having a base and a cover;
a printed circuit board mounted within the housing, the printed circuit board comprising a wireless communications circuit; and
a flexible antenna electrically and mechanically connected to the printed circuit board at a first location, coupled to the wireless communications circuit,
wherein the flexible antenna follows a path from the printed circuit board towards an inner surface of the cover of the housing.

This device design enables an antenna to be spaced from the printed circuit board by having a flexible antenna, which curves away from the printed circuit board toward the inner surface (e.g. the underside) of the cover of the housing. The antenna may follow a path to a seating area within the volume of the housing. This seating area may be right against the inner surface of the cover of the housing or it may be spaced from the inner surface.
The wireless communication device may be a wearable device.
The wireless communications circuit may be for transmitting data using the antenna or for receiving data from the antenna or for both transmission and reception. Typically, the device is for transmitting data to be reported to an external entity so that the wireless communications circuit has at least transmission capability. The wireless communication device typically comprises a battery (or energy harvesting system) and is a standalone unit.
The device may be for sending any data. The device for example comprises a wireless sensor and further comprises a sensor for collecting sensor data, wherein the wireless communications circuit is for wirelessly transmitting the sensor data using the antenna. The sensor data may be physiological sensor data or other data such as position or movement data.
There is a connection between the flexible antenna and the printed circuit board, but this can be a conventional connection generally in the plane of printed circuit board, such as a solder connection or a plug and socket connection. It avoids the need for spring loaded connections or conductive tracks formed on pillars of the housing, which contain additional components, require enhanced positional accuracy in the assembly process and may exert an additional force between the cover and the printed circuit.
The printed circuit board is for example a rigid circuit board, so there is a rigid-to-flex connection between the printed circuit board and the flexible antenna.
The flexible antenna is for example seated against the inner surface (i.e. the underside) of the cover of the housing. This provides the greatest spacing from the printed circuit board, hence the greatest spacing from the subject wearing the device and hence this reduces attenuation.
The first location may be at a periphery of the printed circuit board. This enables the connection to be formed as an edge connector, and it does not take up any space from the main area of the printed circuit board.
Alternatively, the first location may be set back from a periphery of the printed circuit board. This may be preferred so that the printed circuit board is as large as possible within the housing.
The flexible antenna may comprise a carrier sheet having a conductive antenna layer formed on the carrier sheet. The flexible antenna for example has the structure of a flexible printed circuit board, with a track or patch defining the conductive antenna layer.
The antenna layer is for example printed and the carrier sheet comprises a flexi foil. This provides a low cost set of components with simple assembly.
The carrier sheet for example has a projecting portion having an end for electrical and mechanical connection to the printed circuit board at the first location. The carrier sheet thus has a main antenna area and a connection tab extending from the antenna area for connection to the printed circuit board. This may be the feed terminal of a patch antenna.
In a practical embodiment, the carrier sheet comprises an antenna area and the projecting portion extends from a peripheral edge of the antenna area. The antenna area is for example rectangular.
In another example, the carrier sheet comprises an antenna area with a recessed notch and the projecting portion extends outwardly from a base of the recessed notch. In this design, a connection tab extends from a more central part of the antenna area. This forms a tongue, and it gives more freedom in positioning the location at which the flexible antenna connects to the printed circuit board.
In a practical embodiment, the flexible antenna may be elastic and is elastically biased by its elasticity towards the inner surface of the cover of the housing. The flexible antenna thus holds itself in position. It may for example be connected to the printed circuit board in a flat state, and the elastic bias is towards this flat state. During assembly, the flexible antenna is deformed away from the flat state and thereby an elastic bias is created.
The flexible antenna is for example electrically and mechanically connected to the printed circuit board by solder connections or by a plug connector. This provides a simple assembly process.
The invention also provides a method of assembling a device, the method comprising:

providing a printed circuit board having a wireless communications circuit;
electrically and mechanically connecting a flexible antenna to the printed circuit board at a first location;
mounting the printed circuit board above the base of a housing; and
providing a cover of the housing, wherein providing the cover of the housing involves deforming the flexible antenna such that it follows a path from the printed circuit board towards an inner surface of the cover of the housing.

This provides a simple method of manufacturing the device defined above. It avoids the need for accurate alignment of parts and avoids the need for any spring connectors or other intricate connections between the printed circuit board and the antenna.
The flexible antenna is for example elastic and is elastically biased by its elasticity towards the inner surface of the housing cover.
The method may comprise electrically and mechanically connecting the flexible antenna to the printed circuit board by soldering or by use of a plug connector.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 shows a known wearable sensor;
Figure 2 shows a first example of wearable sensor with an antenna configuration in accordance with the invention; and
Figure 3 shows a second example of wearable sensor with an antenna configuration in accordance with the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.
It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.
The invention provides a wireless communication device, which has a printed circuit board, a flexible antenna and a wireless communications circuit within a housing. The flexible antenna follows a path from a location where it connects to the printed circuit board towards an inner surface of the cover of the housing (i.e. the internal underside of the cover). The antenna is thereby spaced from the printed circuit board but has a simple connection to the printed circuit board. The device is for example a sensor patch for wirelessly reporting sensor data, such as physiological sensor data. The sensor data may be collected by an electrode in contact with the skin or by an optical system for sensing optical signals at the skin surface.
It is known to mount an antenna spaced apart from a main printed circuit board within a sensor. Figure 1 shows an example of how to implement such an arrangement.
Figure 1 shows a wireless communication device in the form of a sensor 10 comprising a housing 12 having a base 14 and a cover 16 which forms a top of the housing. It is noted that the terms "base" and "top" are used only for convenience and are not intended to imply any required orientation of the device. A printed circuit board 18 is mounted at the base 14 of the housing and carries a sensor circuit 20 comprising a sensor for collecting sensor data and a wireless transmission circuit for wirelessly transmitting the sensor data.
An antenna 22 is mounted at a top part of the internal space of the housing (i.e. spaced from the base), for example against the cover. To provide an electrical connection between the printed circuit board 18 and the antenna 22, there is a spring-loaded pogo pin connector 24 for making contact between a contact pad 26 of the printed circuit board and a spring-loaded contact face 28 of the pogo pin connector 24.
There may instead be conductive tracks provided along pillars, which project down from the antenna, and spring contacts on the printed circuit board.
These connections between the printed circuit board and the antenna add cost and complexity as well as requiring enhanced positional accuracy in the assembly process.
Figure 2 shows a first example of a wearable sensor in accordance with the invention. The same parts are given the same reference numbers as in Figure 1.
Figure 2A shows the sensor before the assembly is complete, in particular with the housing cover 16 opened up. Figure 2B shows the sensor when assembly is complete, and Figure 2C shows a plan view of the shape of the antenna.
As in Figure 1, the sensor 10 comprises a housing 12 having a base 14 and a cover 16. A printed circuit board 18 is mounted at or near the base 14 of the housing and carries the sensor circuit 20, again comprising a sensor for collecting sensor data and a wireless transmission circuit for wirelessly transmitting the sensor data.
The antenna 22 is a flexible antenna, which is electrically and mechanically connected to the printed circuit board at a first location 40.
The antenna may be a microstrip patch antenna or a loop antenna formed as a conductive track. There may be two electrical connections, one to a feed line of a patch antenna and one to a ground plane, or connections to opposite ends of a loop antenna.
One example of a suitable antenna design is a so-called inverted F antenna, as is often used for cellular connectivity. The antenna comprises a conductive plane, parallel to the printed circuit board assembly, with two electrical connections; ground and feed. Slits can be present in the conductive plane to tune to the correct frequency bands.
In the pre-assembled condition shown in Figure 2A, the antenna 22 is flat and generally in the same plane as the printed circuit board 18. The connection between the flexible antenna 22 and the printed circuit board 18 can be a conventional connection such as a solder connection between traces on the printed circuit board and traces forming part of the flexible antenna. Instead, a connector may be soldered to the printed circuit board 18 and the antenna may have plug connector. In the connected state shown, the antenna is generally planar and in a plane parallel to the plane of the printed circuit board. The connection does not need any spring loaded connections or pillar designs.
The printed circuit board 18 is for example a conventional rigid circuit board, so there is a rigid-to-flex connection between the printed circuit board 18 and the flexible antenna 22.
Any suitable connection may be used between the antenna and the printed circuit board, and which makes the connection without needing the presence of the cover 16 of the housing. The electrical connection can be made by soldering or by using a connector (e.g. a zero insertion force (ZIF) connector). Alternatively, the flexible antenna can be part of an integral flex-rigid printed circuit board assembly.
The flexible antenna for example comprises a carrier sheet such as a flexi foil having an antenna track formed e.g. printed on the carrier sheet. The flexible antenna for example has the structure of a flexible printed circuit board, with a track or patch defining the antenna conductor.
The assembly process involves fitting the cover 16 of the housing to the base 14. This may comprise closing the cover around a pivot as shown, but the cover may instead be a separate part that simply fits over the base.
Figure 2B shows that in the assembled state, the flexible antenna 22 follows a path from the printed circuit board 18 towards an inner surface of the cover 16 of the housing. The antenna is thereby spaced from the printed circuit board by having a flexible antenna that curves away from the printed circuit board towards the inner surface of the cover of the housing. In the example shown, the antenna seats right against the inner surface of the cover of the housing. This provides the greatest spacing from the printed circuit for a given housing shape, hence the greatest spacing from the subject wearing the sensor.
However, in another example, it may adopt a shape defined by guide portions of the housing. Thus, it may be spaced from the inner surface of the cover of the housing, but still spaced from the printed circuit board. The housing functions as an antenna guide, either using internal features of the housing, or the inner surface of the cover of the housing.
The antenna for example has an area of at least 50%, or at least 70% of the area of the printed circuit board. Thus, it is larger than the free space that would be available on the printed circuit board. The antenna may even have an area approaching the size of the printed circuit board (e.g. more than 80% of the area) so that the antenna is maximized in size relative to the size of the sensor.
In the example of Figure 2, the first location 40 is at a periphery, i.e. near an edge, of the printed circuit board. This enables the connection to be formed as an edge connector, and it does not take up any space from the main area of the printed circuit board.
Figure 2C shows an example of the shape of the antenna 22. The antenna shape is defined by the carrier sheet, and it comprises a main rectangular antenna area 22a and a projecting portion 22b extending outwardly from the peripheral edge of the main area 22a. The end of the projection is the first location 40 at which for electrical and mechanical connection is to be made to the printed circuit board. This example shows a patch antenna. The feed lines and connections are not shown in detail since these are all routine.
Figure 3 shows a modification to the design of Figure 2. The same reference numbers are used for the same components.
Figure 3A shows the sensor before the assembly is complete, in particular with the housing cover opened up. Figure 3B shows the sensor when assembly is complete, and Figure 3C shows a plan view of the shape of the antenna.
As shown in Figure 3A, the first location 40 is set back from a periphery of the printed circuit board, for example near the center of the printed circuit board. This may be preferred so that the printed circuit board is as large as possible within the housing.
As shown in Figure 3C, the carrier sheet comprises an antenna area 22a with a recessed notch 22c, and the projecting portion 22b extends outwardly from a base of the recessed notch 22c. In this design, the projection portion 22b forms a connection tab, which extends from a more central part of the antenna area. This forms a tongue, and it gives more freedom in positioning the location 40 at which the flexible antenna connects to the printed circuit board.
In both examples, the flexible antenna may be elastically deformable, with the rest state being the flat state shown in Figures 2A and 3A. After assembly, the antenna is elastically biased by its elasticity towards the inner surface of the cover of the housing, as it tries to return to the straight configuration.
This elastic bias may be the result of the material of the antenna and/or the nature of the connection between the antenna and the printed circuit board. The flexible antenna thus holds itself in position in the assembled state.
The antenna 22 for example has an average height over the PCB (i.e. an average height for the whole area of the antenna carrier) in the range 2mm to 15mm, such as 4mm to 10mm, for example approximately 6mm. A low height enables a low profile sensor and hence improves wearability. A battery may be located beneath the printed circuit board, e.g. with 5mm depth. Including such a battery, a total height of the sensor may be in the range 10 mm to 20 mm.
The area of the antenna carrier can be in the range 3 cm² to 25 cm², such as 5 cm² to 25 cm², or 8 cm² to 15 cm².
By way of example, relatively small cellular antennas exists with dimensions 2.5 cm x 5 cm (12.5 cm²) to cover all cellular bands.
For other communication modalities (e.g. LoRa of Semtech (Trade Marks)), smaller antennas are possible, such as 3 cm x 1.2 cm (3.6 cm²).
Note that for Bluetooth Low Energy (BLE) an antenna can be even smaller and may then be mounted directly on the printed circuit board.
By way of example, an accelerometer based sensor patch may have dimensions 2.9 cm x 5.2 cm. The sensor components, such as the accelerometer in this example, may be very small. A cellular antenna will be the limiting factor for the minimum size of the sensor patch.
Sensor patches with an electrode for contacting the skin may be larger, in particular if there are multiple spaced electrodes. For example, electrodes may be positioned 10cm away from each other.
The assembly of the sensor thus involves:

providing the printed circuit board having the sensor circuit;
electrically and mechanically connecting the flexible antenna to the printed circuit board at the first location;
mounting the printed circuit board at the base of a housing (these last two steps may be in either order); and
providing a cover of the housing. This deforms the flexible antenna such that it follows a path from the printed circuit board towards an inner surface of the cover of the housing.

The invention relates to the antenna configuration. For this reason, details have not been given of the sensor design. The sensor may be a chemical sensor e.g. for sweat or other biomaterial analysis, an accelerometer, a gyroscope, an optical sensor (e.g. a PPG sensor), a conductivity sensor, an ECG sensor, an EEG sensor, an eCTG sensor, a gas sensor, an ultrasound patch or other imaging sensor, or indeed any other known patch type sensor, for example electrode based sensor, in particular any electrode based biosensor.
Any suitable design of antenna conductor may be used.
For an electrode based sensor, the base of the housing for example has an opening to enable contact between the body and a sensor interface, or else the housing may be closed, for example with a window for an optical signal. The housing may have any suitable shape.
The routing of the antenna to a location above the plane of the printed circuit board means there is more space for a larger antenna as well as a spacing from the base.
The printed circuit board does not need to be mounted directly at the base of the housing. This is desirable if a component carried by the printed circuit board is to make contact with the body. However, some sensors do not require such contact, such as accelerometers and gyroscopes, and the printed circuit board may then be spaced from the base of the housing, but the antenna is then positioned even more spaced from the base.
The invention has been described with reference to a sensor patch. However, the invention relates generally to a way to integrate an antenna and associated wireless communication circuit in a compact way within a housing. The data to be transmitted (or received) may not be sensor data - it may be any data generated or sensed at the device, which is to be transmitted. The antenna and communications circuit may instead be used to receive commands for controlling the device. Thus, the device may be an actuator rather than a sensor. It may of course have both sensing and actuation functionality and the wireless communication may be bidirectional, with a wireless transceiver circuit.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Measures recited in mutually different dependent claims can advantageously be combined. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". Any reference signs in the claims should not be construed as limiting the scope.

Claims

A wireless communication device (10) comprising:
a housing (12) having a base (14) and a cover (16);

a printed circuit board (18) mounted within the housing (12), the printed circuit board comprising a wireless communications circuit; and

a flexible antenna (22) electrically and mechanically connected to the printed circuit board (18) at a first location (40), coupled to the wireless communications circuit,

wherein the flexible antenna (22) follows a path from the printed circuit board (18) towards an inner surface of the cover (16) of the housing (12).
The device of claim 1, comprising a sensor for collecting sensor data, wherein the wireless communications circuit is for wirelessly transmitting the sensor data using the antenna.
The device of claim 1 or 2, wherein the flexible antenna (22) is seated against the inner surface of the cover (16) of the housing (12).
The device of any one of claims 1 to 3, wherein the first location (40) is:
at a periphery of the printed circuit board (18); or

set back from a periphery of the printed circuit board (18).
The device of any one of claims 1 to 4, wherein the flexible antenna (22) comprises a carrier sheet having a conductive antenna layer formed on the carrier sheet.
The device of claim 5, wherein the antenna layer is printed and the carrier sheet comprises a flexi foil.
The device of any one of claims 5 to 6, wherein the carrier sheet has a proj ecting portion (22b) having an end for electrical and mechanical connection to the printed circuit board (18) at the first location.
The device of claim 7, wherein the carrier sheet comprises an antenna area (22a) and the projecting portion extends from a peripheral edge of the antenna area (22a).
The device of claim 8, wherein the antenna area (22a) is rectangular.
The device of claim 7, wherein the carrier sheet comprises an antenna area (22a) with a recessed notch (22c) and the projecting portion (22b) extends outwardly from a base of the recessed notch.
The device of any one of claims 1 to 10, wherein the flexible antenna (22) is elastic and is elastically biased by its elasticity towards the inner surface of the cover (16) of the housing (12).
The device of any one of claims 1 to 11, wherein the flexible antenna (22) is electrically and mechanically connected to the printed circuit board (18) by solder connections or by a plug connector.
A method of assembling a wireless communication device (10), the method comprising:
providing a printed circuit board (18) having a wireless communications circuit;

electrically and mechanically connecting a flexible antenna (22) to the printed circuit board (18) at a first location;

mounting the printed circuit board (18) within a housing (12); and

providing a cover (16) of the housing (10), wherein providing the cover of the housing involves deforming the flexible antenna (22) such that it follows a path from the printed circuit board (18) towards an inner surface of the cover (16) of the housing (12).
The method of claim 13, wherein the flexible antenna (22) is elastic and is elastically biased by its elasticity towards the inner surface of the cover (16) of the housing (12).
The method of claim 13 or 14, comprising electrically and mechanically connecting the flexible antenna (22) to the printed circuit board (18) by soldering or by use of a plug connector.