Optimized Near-Field Communication Antenna Structure for Reduced Coupling

An optimized near-field communication (NFC) antenna structure for reduced coupling with a wireless charging (WLC) coil of a computing device includes the WLC coil and an NFC coil that at least partially overlaps the WLC coil. The NFC coil of the optimized structure may include two sections that partially overlap the WLC coil and meet, over the WLC coil, at an angle to reduce coupling between the WLC coil and the NFC coil. The angled shape of the NFC coil may be implemented in various shapes resulting in one or more angles such that the first and second sections of the NFC coil are angled with respect to one another over the WLC coil. The combination or shape of the angles of the NFC coil, as well as NFC coil position relative to the WLC coil, may be optimized to reduce coupling between the NFC coil and the WLC coil.

SUMMARY

This disclosure describes an optimized near-field communication (NFC) antenna structure for reduced coupling between an NFC coil of the antenna structure and a wireless charging (WLC) coil of a computing device (e.g., a smartphone). In aspects, the optimized NFC antenna structure includes the WLC coil and the NFC coil, which at least partially overlaps the WLC coil. The NFC coil of the optimized structure may include two sections that partially overlap the WLC coil and meet, over the WLC coil, at an angle to reduce coupling between the WLC coil and the NFC coil. The NFC coil may be partially disposed over the WLC coil such that a magnetic field generated by the NFC coil is induced into the WLC coil through mutual induction or coupling between the respective coils. In aspects, a geometry, shape, or position of the NFC coil is optimized to reduce the coupling between the respective coils, which may prevent operation of the NFC coil from impairing or interfering with operation of the WLC coil.

This disclosure describes various aspects of an optimized NFC antenna structure for reduced coupling. In aspects, a computing device includes a housing that substantially defines a housing plane of the computing device, a first coil, and a second coil. The computing device also includes a battery positioned within the housing and circuitry coupled to the battery. The first coil is coupled to the circuitry and includes a first conductor having a first shape that is positioned substantially parallel to the housing plane and at least partially within the housing, the first shape forming a winding. The second coil is coupled to the circuitry and includes a second conductor forming a second shape that is positioned substantially parallel to the housing plane and at least partially within the housing. The second coil is usable to generate a magnetic field when subject to an electric current. The second coil at least partially overlaps the first coil. The second shape of the second coil has at least three sections that include a first section that does not overlap the first coil, a second section coupled to a first end of the first section of the second coil, with the second section extending over the first coil. A third section of the second coil is coupled to a second end of the first section of the second coil, with the third section extending over the first coil and being coupled to the second section of the second coil. In aspects, an angle between the second section and third section of the second coil is in a range of 80 degrees to 160 degrees. In aspects, an optimized NFC antenna structure includes the first coil, the second coil, and the dielectric assembly, which may be embodied in a computing device to enable near-field communication and wireless charging.

The same numbers are used throughout the drawings to reference like features and components.

DETAILED DESCRIPTION

An optimized near-field communication (NFC) antenna structure may include an NFC antenna for contactless communication and a wireless charging coil (WLC) for receiving power from and/or transmitting power to another device. In aspects, the optimized NFC antenna structure may be used by a computing device to communicate with another computing device over a short distance (e.g., a distance less than 4 centimeters (cm)) without contact. The computing device may provide a current to the NFC antenna to generate radiation that may be at least partially received by a receiving NFC antenna of another computing device. For example, a smartphone may transfer payment information to an electronic reader by sending an alternating current to an NFC antenna of the smartphone to generate magnetic fields. When the smartphone is positioned near the electronic reader, changes in the magnetic flux (e.g., associated with the generated magnetic fields) over time may induce a current into a receiving NFC antenna of the electronic reader through inductive coupling to transfer the payment information. Alternatively or additionally, the computing device may use the WLC to provide power to other devices, which may include peripheral devices or other computing devices. In some cases, the computing device may use the WLC coil to receive power from another device, such as a wireless charger.

To improve performance of contactless communications using NFC antennas or wireless power transfer using the WLC, some manufacturers include one or more dielectric sheets in an optimized NFC antenna structure to localize magnetic fields and reduce magnetic-field loss. These dielectric sheets may also act as an insulator to protect circuitry of the computing device. In some cases, a respective magnetic field of the NFC antenna and the WLC couples with the other antenna or coil, which may impair or prevent operation of contactless communication or wireless charging functions of the computing device. Thus, in aspects of optimized near-field communication (NFC) antenna structure, a geometry of the NFC antenna (e.g., NFC coil) may be configured to reduce coupling between the co-located coils of the optimized antenna structure to improve contactless communication or wireless charging performance of a computing device.

FIG. 1illustrates, at100-1and100-2, example implementations of a computing device102-1used to perform a contactless communication with a receiving computing device102-2. The computing device may be a mobile electronic device with a screen, input device (e.g., touchscreen and hardware switches), and a battery. While the computing device102-1depicted inFIG. 1is a smartphone, other types of computing devices may also support the techniques described herein. A computing device102may include, for instance, a tablet, a laptop, a computing watch, computing glasses, a home-service device, a drone, a netbook, an e-reader, a virtual-reality headset, and/or another home appliance. The computing device102may be wearable or non-wearable but mobile. The computing device102may include one or more processors, receivers, transmitters, circuitry, and so forth.

As shown at100-1, the computing device102-1may include a housing104that at least partially covers (e.g., encloses, protects) an optimized NFC antenna structure106and substantially defines a housing plane108(e.g., an XY plane across a front surface (screen) or back surface of the computing device102-1). In this example, the optimized NFC antenna structure106includes an NFC antenna110(e.g., an NFC coil) and a WLC112that are oriented substantially parallel to the housing plane108and may be respectively positioned to at least partially overlap one another. In aspects, the computing device102-2includes a battery (not shown) positioned within the housing104and circuitry (not shown) that couples various components of the computing device. For example, the circuitry can couple a transceiver of the computing device102-2to the NFC antenna110or couple the battery to the WLC112to enable wireless reception or transmission of power by the computing device.

Example implementation at100-2illustrates the computing device102-1positioned near a receiving computing device102-2and generating magnetic fields114when a current116is supplied to the NFC antenna110. Changes in the magnetic flux over time, associated with these magnetic fields114, may induce an electromotive force (EMF) into a receiving antenna118in accordance with Faraday's law of induction. This EMF may correspond to an induced current120associated with, for instance, encrypted information used to complete a contactless payment.

Some preceding NFC antennas (e.g., rectangular shaped coils), however, may generate magnetic fields114that excessively couple with a WLC co-located with the NFC antenna, which may impair or disrupt operation of a wireless charging circuit coupled to the WLC. For example, magnetic fields generated by NFC polling transmissions may prevent the wireless charging circuit coupled to the WLC from detecting another device or result in false detection of another source of wireless charging magnetic fields. In some cases, this can cause the wireless charging circuit to enter a timeout state or to cease detection operations. As a result, the user may be prevented from accessing wireless charging functionalities of a computing device when the NFC antenna is active for various polling or communication operations. Consequently, barriers may exist that prevent users from efficiently using contactless communication and wireless charging functionalities of a computing device. This disclosure describes an optimized NFC antenna structure that utilizes various geometries and arrangements of an NFC antenna (NFC coil), a WLC, and dielectric assembly to reduce coupling of a magnetic field between the NFC antenna and the WLC. By so doing, a computing device may operate an NFC transceiver with less or minimal interference to wireless charging circuitry of the computing device.

In general, an NFC antenna110or WLC112may refer to an electromagnetic coil comprising a conductive material (e.g., copper wire or copper traces) that enables the flow of current at a resonant frequency, for instance, of 13.56 Megahertz (13.56 MHz) for NFC or 150 kilohertz (150 kHz) for wireless charging. In aspects, the WLC112may be implemented generally as a conductive coil (e.g., wires or traces) with an appropriate resonance for wireless charging operations, which may include transmitting wireless power to another device or receiving wireless power from a power source. In aspects, the WLC112may be implemented as any suitable shape, which may include a circle, an ellipse, a rectangle, a rectangle with rounded corners, a square with rounded corners, a stadium, a polygon with rounded corners, or the like.

The electrical characteristics of the NFC antenna may include an inductance, a resistance, and a capacitance based on an associated topography (e.g., dimensions, number of windings, spacing). For example, some NFC antennas are configured for an inductance of 200-600 nanohenry (nH) with a quality factor of approximately 8-15 and a self-resonant frequency greater than 30 MHz. NFC antennas may be used to read and/or write information on NFC tags, communicate with another NFC antenna of a second device, and/or perform card emulation for transactions including payments or ticketing.

FIG. 2illustrates at200an example configuration of an optimized NFC antenna structure for reduced coupling in accordance with one or more aspects. In this example, the optimized NFC antenna structure106is implemented on a substrate202, which may include or represent a circuit board, internal surface, ground plane, or other conductive layer of a computing device. As such, the illustrated optimized NFC antenna structure106may be on or above the substrate202of a computing device and under, below, or within a housing (e.g., non-conductive enclosure or exterior surface) that substantially defines a housing plane of the computing device. In aspects, the optimized NFC antenna structure106includes an NFC antenna110that at least partially overlaps a portion of a WLC112. The WLC112may include a first coil with a conductor that forms a round or circular winding shape that is positioned substantially parallel to the housing plane of the computing device. The NFC antenna may include a second conductor (e.g., coil or winding) that forms another shape (e.g., triangular, trapezoidal, polygonal) that is positioned substantially parallel to the housing plane. As described herein, the NFC coil may generate a magnetic field when subject to an electric current and be positioned such that a portion of the magnetic field generated by the NFC coil is induced into the WLC through coupling between the coils (e.g., mutual induction).

As shown inFIG. 2, the optimized NFC antenna structure106may be implemented with a dielectric assembly of one or more sections or layers of dielectric material to increase magnetic field strength and/or improve performance of the NFC antenna110and/or WLC112. In this example, the dielectric assembly includes a first section of dielectric material204positioned below the NFC antenna110and the WLC112, and a second section of dielectric material206positioned below a portion of the NFC antenna110. In aspects, the first section of dielectric material204may include a sheet or layer of nanocrystalline (NC) to improve isolation of radiation between the NFC antenna110and/or the WLC112. The first section of dielectric material204(e.g., NC sheet) is not limited to the topography shown at200and may include various shapes that extend partially or wholly below the WLC112and/or partially below the NFC antenna110. Generally, the NC sheet may contain NC materials including polycrystalline materials with crystallite sizes on the order of nanometers (nm). The second section of dielectric material206may include one or more ferrimagnetic materials (e.g., strontium, barium, manganese, nickel, zinc) to increase the magnetic field strength associated with the optimized NFC antenna structure and improve the inductive coupling to a receiving NFC antenna. In general, the dielectric sections or sheets may be used to reduce magnetic field loss and improve isolation of magnetic fields from, for instance, generating eddy currents in nearby conductive elements and/or surfaces.

In aspects of an optimized NFC antenna, conductors (e.g., coils, wires, traces) of the NFC antenna110may be formed in substantially non-circular shapes, which include polygons with at least three sections with angular or rounded corners (shown in relation to the housing plane108). In some cases, the NFC antenna110is formed into a triangle shape or trapezoid shape with one or more sections that do not extend across the WLC112in an orthogonal fashion. In this example, the NFC antenna110includes a first section208that does not overlap the WLC112and is positioned over the second section of dielectric material206(e.g., ferrite layer). The NFC antenna110also includes a second section210and a third section212that extend at least partially over the WLC112with an angle between the second and third sections being in a range of 80 degrees to 160 degrees. The second section210and/or third section212may be positioned at least partially over a center, core, cavity, or internal diameter (e.g., a space or volume between windings) of the WLC112. In some implementations, the angle between the second section210and the third section212is within a range of 130 degrees to 140 degrees. In aspects, the NFC antenna110may include a fourth section214that couples the third section212to the first section208(or any intermediate section) of the NFC antenna. The fourth section of the NFC antenna110may at least partially overlap the WLC112or be positioned such that the fourth section214does not overlap the WLC112. As such, the NFC antenna110may be formed or configured generally in a trapezoid shape or isosceles trapezoid shape that partially overlaps the WLC112. This is but one configuration of an optimized NFC antenna structure, which is further described along with other example configurations throughout this disclosure.

FIG. 3illustrates at300cross-sectional views of an example optimized NFC antenna structure106that includes a WLC coil, an NFC coil, and a dielectric assembly configured in accordance with one or more aspects. The cross-sectional views shown at300are depicted with respect to a section plane302(e.g., a YZ plane) that is orthogonal to the housing plane108. These views include a cross-sectional view304-1(view304-1) along an edge (view line A-A) of the optimized NFC antenna structure and a cross-sectional view304-2(view304-2) along a centerline (view line B-B) of the optimized NFC antenna structure. In the views illustrated, dimensions of each component (e.g., NFC antenna110, WLC112, dielectric material204, dielectric material206) are depicted by way of example only and are not limited to the relative dimensions, arrangement, or material stack-ups shown.

In the example view304-1, a portion of the NFC antenna110(e.g., a first section) may be positioned over or overlap the first section of dielectric material204and the second section of dielectric material206. Here, note that this portion of the NFC antenna110and/or the second section of dielectric material206is not positioned over or overlap the WLC112. With reference to view304-2, the WLC112is positioned over the first section of dielectric material204(e.g., NC sheet), which is shown in reference to the substrate202(e.g., device main logic board or ground plane). The NFC antenna110is positioned to partially overlap the WLC112and the second section of dielectric material206(e.g., ferrite layer). In some cases, the illustrated configuration of the NFC antenna110and WLC112provide a compact and space-efficient implementation that enables contactless communication and/or wireless charging functionalities.

FIG. 4illustrates at400cross-sectional views of another example optimized NFC antenna structure106that includes a WLC coil, an NFC coil, and a dielectric assembly configured in accordance with one or more aspects. Here, the optimized NFC antenna structure is shown illustrated in relation to housing402, which may include a non-conductive or magnetic field-permeable surface of a computing device (e.g., back housing). The cross-sectional views shown at400are depicted with respect to the section plane302(e.g., a YZ plane) that is orthogonal to the housing plane108. These views include a cross-sectional view404-1(view404-1) along an edge (view line A-A) of the optimized NFC antenna structure and a cross-sectional view404-2(view404-2) along a centerline (view line B-B) of the optimized NFC antenna structure. In the views illustrated, dimensions of the components (e.g., NFC antenna110, WLC112, dielectric material204, dielectric material206) are depicted by way of example only and are not limited to the relative dimensions, arrangement, or material stack-ups shown.

In the example view404-1, the NFC antenna110and a portion of the first section of dielectric material204(e.g., NC sheet) may be positioned near or in contact with the housing402. For example, one or more components of the optimized NFC antenna structure106may be assembled in relation to the housing402or the substrate202using various adhesives or fabrication techniques. In other words, the components of the optimized NFC antenna structure106may be assembled as a sub-assembly of coils and dielectric material (e.g., flexible circuits and dielectric layers), which is then assembled between the substrate202and the housing402(e.g., positioned or adhered to the housing or substrate).

With reference to view404-2, the WLC112is also positioned near or against the housing402and below a portion of the NFC antenna110. Here, note that a first portion of the WLC112is co-planar with the NFC antenna110and a second portion of the WLC112is positioned below a portion of the NFC antenna110. As shown at402-2, a contour of the first section of dielectric material204(e.g., NC sheet) may follow a general contour of components positioned above the first section, which include the NFC antenna, WLC112, and the second section of dielectric material206(e.g., ferrite layer). As noted, the example configurations described herein may enable a compact and space-efficient implementation of the NFC antenna110and the WLC112in a device with reduced coupling.

FIG. 5illustrates at500a plan view of an example optimized NFC antenna structure implemented in accordance with one or more aspects. In aspects of an optimized NFC antenna structure, a geometry and/or positioning of the NFC antenna110may be configured to reduce coupling between the NFC antenna110and the WLC112.FIGS. 5-8generally illustrate and describe non-limited examples of an optimized NFC antenna structure with varying geometries. As described herein, the NFC antenna110may be implemented with four sections208,210,212, and214, with respective ends of the second section210and third section212coupled over the WLC112. In some cases, the fourth section214is positioned over the WLC112and couples an end of the third section212to an end of the first section208. Thus, a shape of the NFC antenna110may include a quadrilateral, trapezoid, isosceles trapezoid, and so forth. Although not shown, the NFC antenna110may also be implemented with three sections (e.g., without section214, section210coupled directly to section212) or with additional sections to form various polygonal shapes (e.g.,FIGS. 6 and 7).

As shown at500, the NFC antenna110can be configured with a second section210and a third section212that have an interior angle502(e.g., angle between the sections) that is within a range of 80 degrees to 160 degrees. In some cases, the NFC antenna110is configured such that an interior angle504between the second section210and the fourth section214is within a range of 85 degrees to 95 degrees. In this example, the NFC antenna110is implemented such that an interior angle between the second section210and the third section212is approximately 135 degrees. Alternatively, angular dimensions of the NFC antenna sections may be defined as an exterior angle506with reference to the third section212or an orthogonal line508across the WLC112. Thus, in some cases, an exterior angle of the third section212and one of the second section210or fourth section214is in a range of ten degrees to 50 degrees. As shown inFIG. 5, the second section210and the third section212may have an exterior angle510of approximately 45 degrees. Although not specifically shown, the third section212and the fourth section214may also have a similar exterior angle of approximately 45 degrees. As described herein, the geometry of the NFC antenna110, including respective lengths and angles of sections210,212, and/or214, can be configured to reduce coupling between the NFC antenna110and the WLC112.

FIG. 6illustrates at600a plan view of another example optimized NFC antenna structure implemented in accordance with one or more aspects. In this example, the NFC antenna110includes a fifth section602coupled between the first section208and the second section210, and a sixth section604coupled between the fourth section214and the first section208. As shown inFIG. 6, the sections of the NFC antenna110may be configured such that the second section210and the third section212have an exterior angle606of approximately 34 degrees. Although not specifically shown, the third section212and the fourth section214may also have a similar exterior angle of approximately 34 degrees. Alternatively, any or all of the sections of the NFC antenna110may be configured with different lengths or exterior angles.

FIG. 7illustrates at700a plan view of yet another example optimized NFC antenna structure implemented in accordance with one or more aspects. In this example, the NFC antenna110includes a fifth section702coupled between the first section208and the second section210, and a sixth section704coupled between the fourth section214and the first section208. As shown inFIG. 7, the NFC antenna110may be configured such that the second section210and the third section212may have an exterior angle706of approximately 23 degrees. Although not specifically shown, the third section212and the fourth section214may also have a similar exterior angle of approximately 23 degrees. Alternatively, any or all of the sections of the NFC antenna110may be configured with different lengths or exterior angles.

FIG. 8illustrates at800a plan view of an example optimized NFC antenna structure that includes an asymmetric NFC coil in accordance with one or more aspects. As shown inFIG. 8, the NFC antenna110may be formed and/or positioned asymmetrically with respect to the WLC112. In this example, the NFC antenna110is implemented with four sections802,804,806, and808, with respective ends of the second section804and third section806meeting or being coupled over the WLC112. As shown inFIG. 8, the NFC antenna110is positioned or configured asymmetrically with respect to the WLC112, with the first section802and fourth section808positioned to not overlap the WLC112. Generally, a shape of the NFC antenna110may include a quadrilateral, polygon, trapezoid, and so forth. Although not shown, the NFC antenna110may also be implemented with three sections (e.g., without section808, section802coupled directly to section806) or with additional sections to form various polygonal shapes.

In aspects, the NFC antenna110can be configured such that an interior angle810between the second section804and the third section806(e.g., angle between the sections) is within a range of 80 degrees to 160 degrees. In some aspects, the angle between the second section804and the third section806of the NFC antenna110is within a range of 125 degrees to 145 degrees. In this example, the NFC antenna110is implemented such that an interior angle between the second section804and the third section806is approximately 135 degrees. Alternatively, angular dimensions of the NFC antenna sections may be defined as an exterior angle812with reference to the third section806or an orthogonal line814across the WLC112. Thus, in some cases, an exterior angle of the second section804and the third section806is in a range of ten degrees to 50 degrees. As shown inFIG. 8, the second section804and the third section806may have an exterior angle816of approximately 45 degrees. Although not specifically shown, in some aspects (e.g.,FIG. 5), the third section806and the fourth section808may also have a similar exterior angle of approximately 45 degrees. As described herein, the geometry of the NFC antenna110, including respective lengths and angles of sections802,804,806, and/or808(or additional sections), can be configured to reduce coupling between the NFC antenna110and the WLC112.

Although an optimized antenna structure for reduced coupling has been described in language specific to features, it is to be understood that the subject of the appended claims is not necessarily limited to the specific techniques described herein. Rather, the specific techniques are disclosed as example implementations of an optimized antenna structure for reduced coupling between coils or antennas (e.g., an NFC coil and a WLC coil).