Patent Application
20210250065
The present specification relates to systems, methods, apparatuses, devices, articles of manufacture and instructions for near-field electromagnetic induction communications.
According to an example embodiment, a device including a near-field electromagnetic induction (NFEMI) antenna, comprising: a first inductive coil having a first end coupled to a first feeding connection and a second end coupled to a second feeding connection; a second inductive coil, having a first end coupled to the second end of the first inductive coil and a second end; wherein the second inductive coil is formed into a first surface; a third inductive coil formed into a second surface; wherein the first surface including the second inductive coil and the second surface including the third inductive coil are configured to form a first capacitance (C); wherein the third inductive coil includes a first end galvanically coupled to the second end of the second inductive coil; wherein the first inductive coil is configured to receive or transmit non-propagating quasi-static near-field magnetic induction signals; and wherein the second and third inductive coil are configured to receive or transmit non-propagating quasi-static near-field electric induction signals.
In another example embodiment, the first surface includes the first inductive coil.
In another example embodiment, the first inductive coil geometrically surrounds the second inductive coil.
In another example embodiment, the first surface including the first inductive coil and the second surface including the third inductive coil are configured to form a second capacitance (Ca).
In another example embodiment, the third inductive coil includes a second end; and the second end of the third inductive coil is electrically open-ended.
In another example embodiment, further comprising a first substrate; wherein the second inductive coil is coupled to one side of the first substrate; and wherein the third inductive coil is coupled to a side opposite to the one side of the first substrate.
In another example embodiment, the first inductive coil is coupled to the one side of the first substrate.
In another example embodiment, further comprising a conductive plate; wherein the third inductive coil includes a second end; and wherein the conductive plate is coupled to the second end of the third inductive coil.
In another example embodiment, the conductive plate and the first inductive coil are configured to increase the second capacitance (Ca).
In another example embodiment, the second inductive coil and the third inductive coil are configured to increase the first capacitance (C).
In another example embodiment, further comprising a first substrate; wherein the first and second inductive coils are coupled to one side of the first substrate; wherein the third inductive coil is coupled to a side opposite to the one side of the first substrate; and wherein the conductive plate is coupled to the side opposite to the one side of the first substrate.
In another example embodiment, the first inductive coil and the feeding connections are configured to carry a current; and the current is based on the near-field magnetic signals.
In another example embodiment, the second and third inductive coils are configured to carry a voltage; and the voltage is based on the near-field electric signals.
In another example embodiment, the first and second surfaces are planar surfaces.
In another example embodiment, the first, second and third inductive coils are formed in a shape of at least one of: a circle, a rectangle, a polygon, an oval, or a diamond.
In another example embodiment, the capacitance (C) between the second and third inductive coils is a distributed capacitance.
In another example embodiment, the capacitance (Ca) between the first and third inductive coils is a distributed capacitance.
In another example embodiment, the first, second and third inductive coils each include a looped element or structure; and the looped element or structure is at least one of: helical, a planar spiral, or a three-dimensional spiral.
In another example embodiment, the antenna is embedded in at least one of: a glucose sensor, a wearable device; a smart watch; a smartwatch housing, a wireless mobile device, an earbud, a hearing aid, a headphone, an activity tracker, or a heart rate monitor.
According to an example embodiment, a device including a near-field electric induction (NFEI) antenna, comprising: an inductive coil (i.e. L2/314), a first feeding connection, and a second feeding connection are formed into a first surface; wherein a first end of the inductive coil is coupled to the second feeding connection; another inductive coil (i.e. L3/316) formed into a second surface; wherein a first end of the another inductive coil is galvanically coupled (i.e. at 318) to a second end of the inductive coil; wherein the inductive coil in the first surface and the another inductive coil in the second surface are configured to form a first capacitance (C); wherein the another inductive coil in the second surface and the first feeding connection in the first surface are configured to form a second capacitance (Ca); and wherein the inductive coils are configured to receive or transmit non-propagating quasi-static near-field electric induction signals.
The above discussion is not intended to represent every example embodiment or every implementation within the scope of the current or future Claim sets. The Figures and Detailed Description that follow also exemplify various example embodiments.
Various example embodiments may be more completely understood in consideration of the following Detailed Description in connection with the accompanying Drawings.
While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that other embodiments, beyond the particular embodiments described, are possible as well. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are covered as well.
Herein discussed are near-field interactions between a near-field device, perhaps on a user's body, and other conductive surfaces and/or other wireless networked devices (e.g. Internet of Things (IoT) devices) based on near-field electromagnetic induction (NFEMI), where the transmitter and receiver are coupled by both magnetic (H) and electric (E) fields. While RF wireless communication is accomplished by propagating an RF plane wave through free space, NFEMI communication utilizes non-propagating quasi-static H and E fields.
An H-field antenna (i.e. magnetic antenna) is primarily sensitive to magnetic fields and/or primarily initiates magnetic fields when driven by a current. Any E-field component from an H-field antenna is strongly reduced (e.g. −20 to −60 dB reduction, a factor of 0.1 to 0.0008 (10% to 0.08%) depending on the antenna design).
A small loop antenna is an example H-field antenna and includes a loop antenna with dimensions much smaller than the wavelength of its use. The small loop antenna does not resonate at the NFEMI carrier frequency but is instead tuned to resonance by an external reactance. In some example embodiments the current in the small loop antenna has in every position of the loop the same value.
An E-field antenna (i.e. electric antenna) is primarily sensitive to electric fields and/or primarily initiates electric fields when driven by a voltage. Any H-field component from an E-field antenna is strongly reduced (e.g. −20 to −60 dB reduction, a factor of 0.1 to 0.0008 (10% to 0.08%) depending on the antenna design).
A short loaded dipole antenna is an example E-field antenna and includes a short dipole with dimensions much smaller than the NFEMI carrier frequency and in some example embodiments has extra capacitance surfaces at both ends.
The quasi-static characteristic of these fields is a result of the NFEMI antenna dimensions in combination with their carrier frequencies. Most of the near-field energy is stored in the form of magnetic and electric fields, while a small amount of RF energy inevitably propagates in free space. Small antenna geometries minimize radiating waves in free space.
Some wearables, such as hearing aids and wireless earbuds, employ Near-Field Magnetic Induction (NFMI) as a wireless communication method. In NFMI wireless communication, two loosely coupled coils realize signal transfer. No radiation of radio waves takes place. A current flowing in the transmission coil generates a H-field which in turn induces a current in the receiving coil. In this way, wireless communication is accomplished. Unfortunately, H-field based NFMI systems with small antenna coils have a limited range that may be much smaller than an entire wearable user's body. Such H-field communications are sensitive to coil orientation. In the case of a hearing aid form factor, a H-field induction based system cannot cover an entire human body. However, since in hearing aids both coils are always aligned with each other, they are not influenced by the movement of the human body.
Other wearables employ Near-field Electric Induction (NFEI)) as a wireless communication method. NFEI allows electronic devices on and near a conductive surface (e.g. a human body) to exchange information through E-field coupling (e.g. at 21 MHz). NFEI is also sometimes called Body Coupled Communication (BCC). While E-field based NFEI signals can have a greater range than H-field based NFMI signals, the E-field signal strength can vary with regard to body posture and is sensitive to body movements. The body can even partially block a capacitive return path, thereby increasing E-field channel loss and reliable and robust wireless communication is not possible.
When the NFEMI antenna 100 is proximate to a structure (e.g. a conductive structure, a body, a person, an object, etc.) the magnetic and electric fields will be substantially confined to the structure and not significantly radiate in free-space. This enhances security and privacy of such body networked communications.
In various example embodiments, the antenna 100 operates at or below 50 MHz (e.g. for example at 30 MHz) to ensure that the fields are following the structure's contours and to ensure that far field radiation is strongly reduced.
The example idealized antenna 100 includes the magnetic (H-field) antenna 105 having a resistance (R3) and an inductance (L1), the electric (E-field) antenna 120 having a conductive structure formed from the two loading plates 125 and 130, and the two feeding points 135, 140.
The supporting circuits 150 include a tuning circuit 155, an LNA 160 (low noise amplifier), a communications signal interface 165, and a controller 170.
The tuning circuit 155 is coupled to the first and second feed points 135, 140. The tuning circuit 155 includes a first variable tuning capacitance bank (C1), a second variable tuning capacitance bank (C2), a first variable tuning resistance bank (R1), and a second variable tuning resistance bank (R2). The capacitance banks and resistance banks are coupled to a reference potential 190 (e.g. a ground potential). The capacitive banks are coupled to the controller 170 by control line 175, and the resistance banks are coupled to the controller 170 by control line 180.
The controller 170 adjusts the first and second capacitance banks (C1), (C2) to adjust a resonant frequency of the magnetic 105 and the electric 120 antennas (e.g. to 10.6 MHz). The controller 170 adjusts the first and second resistance banks (R1), (R2) to adjust a bandwidth of the magnetic 105 and the electric 120 antennas (e.g. to 400 KHz) sufficient to allow the non-propagating quasi-static near-field signal to be received from the antennas 105, 120.
The capacitance banks (C1), (C2) are equally tuned using the control line 175 from the controller 170, and the resistance banks (R1), (R2) are equally tuned using the control line 180 from the controller 170.
The LNA 160 is coupled between the tuning circuit 155 and a communications signal interface 165. When the near-field device 145 is receiving the non-propagating quasi-static near-field signal, induced voltage 185 (Vlna) is present across the LNA 160 differential inputs. The LNA 160 amplifies the received near-field signal which is then further processed by additional radio/RFIC/baseband circuits (not shown) coupled to the communications signal interface 165. The LNA 160 is also coupled to the reference potential 190.
Since both inputs to the LNA 160 are coupled to the antennas 105, 120 the near-field device's 145 configuration is said to be balanced. The balanced circuit configuration helps reject interference signals that enter both LNA 160 input lines with the same amplitude and phase. In other examples an unbalanced device can be used.
During operation a voltage is induced in the electric (E-field) antenna 120 by a received near-field electric signal. This voltage generates a current through the E-field antenna 120. The received voltage is defined by:
where:
U voltage at the LNA 160 input [Volts]
Ca electric antenna 120 equivalent capacitance
Ct Tuning capacitance (e.g. combination of C1 and C2)
Q quality factor of the antenna system
In this geometric configuration where the coupled coils 215 (L1) and 217 (L2) are nested (i.e. L2 is surrounded by L1) and because the magnetic antenna formed by magnetically coupled coils L1 and L2 is implemented as a planar structure (i.e. a distributed geometry) a significant amount of electric field is generated. Moreover, this antenna structure benefits from the property of the coupled coil antenna of generating a higher electric field for the same transmit voltage at feeding connections 235 and 240 compared to a single coil antenna and the property of receiving a larger voltage at feeding connections 235 and 240 for the same voltage induced in the antenna by the electric field as compared to a single coil antenna.
A magnetic (H-field) antenna 212 portion includes inductance (L1) having a resistance (R3). The electric (E-field) antenna 214 portion includes inductance (L2) having the open end 202. Due to the geometry of the antenna 200, a distributed capacitance (Ca) between the inductance (L1) and inductance (L2) also exists.
The antenna 200 is similarly coupled to feeding connections 235, 240 and the supporting circuits 272 as discussed in
Inductances L1 and L2 are in a series combination having a same winding direction, and thus have a same magnetic flux direction. As a result a voltage at the input of L1 is higher across L1+L2. No conductive plates are included in the antenna 200.
Now discussed is a near-field antenna device having a physical and electrical structure that enables a set of inductive coils to have an aggregate inductance greater than a sum of their individual inductances. The near-field antenna device in some example embodiments has a same communication performance as some other single-coil or dual-coil near-field devices, but instead has geometric/physical dimensions up to 50% smaller than such other single and dual coil near-field devices.
For the purposes of this discussion the following definitions are hereby provided:
In some example embodiments, an “open ended” element/structure is herein defined to include an element/structure that is “not galvanically connected” to any other element/structure.
In some example embodiments, a “coil” is herein defined to include a “looped” conductive element/structure, including helical, planar spiral, and three-dimensional spiral elements/structures.
In further example embodiments, an “open-ended coil” is herein defined to include elements/structures where a voltage and/or electric-field is different for (e.g. is not the same or uniform throughout) various portions of the element/structure.
In some example embodiments, a “conductive plate” is herein defined to include an element/structure where a voltage and/or electric-field is substantially the same throughout all portions of the element/structure;
The tri-coil antenna device 300 of
The near-field antenna 306 portion includes: a magnetic (H-field) antenna 308 having a first inductive coil 312 (e.g. a conductor segment having a first end, second end) with inductance (L1) and resistance (R3); an electric (E-field) antenna 310 having a second inductive coil 314 (e.g. conductor segment having a first end, second end) with inductance (L2) and a third inductive coil 316 (e.g. conductor segment having a first end, second end) with inductance (L3).
The second inductive coil 314 is formed into a first surface. The first surface is herein defined as a surface created by a physical shape of the second inductive coil 314. The first surface is not a surface on the first or second substrate 302, 304.
The third inductive coil 316 is formed into a second surface. The second surface is herein defined as a surface created by a physical shape of the third inductive coil 316. The second surface is not a surface on the first or second substrate 302, 304.
Also shown is a connection point 317, a galvanic connection 318 (e.g. via/galvanic short), a resistance (R4), an optional conductive loading plate 320 (not used if the third inductive coil 316 (L3) is left open ended), a first feeding connection 326, and a second feeding connection 328.
A first capacitance (C) 322 is formed between the second inductive coil 314 and the third inductive coil 316. A second capacitance (Ca) 324 is formed between either the third inductive coil 316 or the conductive loading plate 320, and either the first inductive coil 312 or the first feeding connection 326. The third inductive coil 316 (L3) and the second inductive coil 314 (L2) in some example embodiments are aligned to each other to maxize the first capacitance 322 (C).
The first inductive coil 312 (L1) and the second inductive coil 314 (L2) are also magnetically coupled, where the magnetic coupling can be expressed by a first coupling factor k1. The third inductive coil 316 (L3) and the second inductive coil 314 (L2) are also magnetically and capacitively coupled, where the magnetic coupling can be expressed by a second coupling factor k2.
The first inductive coil 312 has a first end coupled to the first feeding connection 326 and a second end coupled to the second feeding connection 328. The second inductive coil 314, has a first end coupled to the second end of the first inductive coil 312 and a second end.
The second inductive coil 314 is formed into the first surface. The third inductive coil 316 formed into the second surface. The first surface including the second inductive coil 314 and the second surface including the third inductive coil 316 are configured to form the first capacitance (C) 322.
The third inductive coil 316 includes a first end galvanically coupled by the galvanic connection 318 (e.g. a via) to the second end of the second inductive coil 314.
The first inductive coil 312 is configured to receive or transmit near-field magnetic induction signals, and the second and third inductive coil 314, 316 are configured to receive or transmit near-field electric induction signals.
In various example embodiments the first surface includes the first inductive coil 312 as well. The first surface including the first inductive coil 312 and the second surface including the third inductive coil 316 are configured to form the second capacitance (Ca) 324. In some example embodiments the first surface the first inductive coil 312 geometrically surrounds the second inductive coil 314.
In some example embodiments the second end of the third inductive coil 316 is electrically open-ended, wherein in other example embodiments the second end of the third inductive coil 316 is coupled to the conductive plate 320.
The conductive plate 320 and the first inductive coil 312 are in some examples configured to increase the second capacitance (Ca) 324. Similarly in other example embodiments the second inductive coil 314 and the third inductive coil 316 are configured to increase the first capacitance (C) 322. In some examples the conductive loading plate 320 can be kept small and as far as possible from the first inductive coil 312 (L1) to minimize undesirable eddy currents.
In those example embodiments that include the first substrate 302 (e.g. where there is not an air gap between the first and third coils 312, 316 and/or the second and third coils 314, 316, the first and second inductive coils 312, 314 are coupled to one side of the first substrate 302 and the third inductive coil 316 is coupled to a side opposite to the one side (e.g. an opposite side) of the first substrate 302. The conductive plate 320 is also coupled to the side opposite to the one side of the first substrate 302.
The first inductive coil 312 and the feeding connections 326, 328 are configured to carry a current based on transmitted and/or received near-field magnetic signals. The second and third inductive coils 314, 316 are configured to carry a voltage based on transmitted and/or received near-field electric signals.
The first, second and third first inductive coils 312, 314, 316 (L1, L2, L3) are connected in series so as to have an aggregate inductance (L) that when a current is supplied through them a constructive magnetic and electric field is created such that the tri-coil antenna device 300 has a same communication performance as other near-field devices, but with geometric/physical dimensions 50% smaller in some example embodiments. The aggregate inductance (L) is greater than a sum of the individual inductances L1, L2, L3. For example, by positioning a first surface including the second inductive coil 314 (L2) facing a second surface including the third inductive coil 316, a higher/boosted transmit mode voltage at the conductive loading plate 320 is generated for near-field electric signal transmission and reception.
In some example embodiments the first and second surfaces are planar surfaces, and the first, second and third inductive coils 312, 314, 316 are formed in a shape of at least one of: a circle, a rectangle, a polygon, an oval, or a diamond. The first and second inductive coils 312, 314 sometimes also have a same winding direction and are physically juxtaposed as a set of curved parallel wires separated by a distance.
In various example embodiments: the capacitance (C) 322 between the second and third inductive coils 314, 316 is a distributed capacitance, and the capacitance (Ca) 324 between the first and third inductive coils, 312, 316 is a distributed capacitance; the second and third inductive coils 316 are coupled in series; and/or the first and second inductive coils 314 are configured to have a same magnetic flux direction.
In various example embodiments the first, second and third inductive coils 312, 314, 316 each include a looped element or structure, which could be at least one of: helical, a planar spiral, or a three-dimensional spiral. The first inductive coil 312 is configured to receive or transmit non-propagating quasi-static magnetic near-field signals, and the second and third inductive coils 314, 316 are configured to receive or transmit non-propagating quasi-static electric near-field signals.
The first substrate 302 in some example embodiments has an electric permittivity different from air, for example a relative permittivity of 4. Electromagnetic permittivity (c), is a measure of a material's electric polarizability. A material with high permittivity polarizes more in response to an applied electric field than a material with low permittivity, thereby storing more energy in the electric field. An ideal metal has infinite permittivity as such a metal would completely negate any electric field inside their bulk. The first substrate 302 can also have a thickness 0.5 mm or less.
The second substrate 304 (e.g.) may have a different permeability than air, for example a relative permeability of 150. In contrast to electromagnetic permittivity, electromagnetic permeability is the measure of the resistance of a material against the formation of a magnetic field, such materials can be used to decrease the physical size of the tri-coil antenna device 300. The second substrate 304 in some example embodiments is a magnetic permeable material such as a ferrite sheet configured to shield the tri-coil antenna device 300 from the supporting circuits 330.
The example near-field device 329 of
The tuning circuit 332 is configured to resonate to the near-field communication frequency and set the communication bandwidth. The controller 338 tunes the resonance frequency using the variable capacitors C1 and C2. The controller 338 tunes the communication bandwidth using the variable resistors R1 and R2. In the example shown, the tuning circuit 332 is coupled to the low noise amplifier 334 when the device is in receive mode; however, for transmit mode, the tuning circuit 332 is connected a power amplifier (not shown).
The tri-coil antenna device 300 can be in various examples embedded in at least one of: a glucose sensor, a wearable device; a smart watch; a smartwatch housing, a wireless mobile device, an earbud, a hearing aid, a headphone, an activity tracker, or a heart rate monitor. Thus wearables for wireless on-body networks that require a small form factor are good candidate applications for the tri-coil antenna device 300.
For example in a medical application the tri-coil antenna device 300 can be embedded in a glucose monitoring system that is worn on-body (e.g. see
Other applications include specialty sensors that can benefit from the small form factor of the tri-coil antenna device 300. The second substrate 304 could be at least one of: a patch, a medical patch, air, a high dielectric material, or a polyethylene foam.
In some example embodiments the magnetic (H-field) antenna 308 with the first inductive coil 312 is not included. Such example embodiments only use the electric (E-field) antenna 310.
Such example embodiments include a near-field electric induction (NFEI) antenna 310 device comprising: an inductive coil 314 (L2), the first feeding connection 326, and the second feeding connection 328 formed into a first surface. A first end of the inductive coil 314 is coupled to the second feeding connection 328. Another inductive coil 316 (L3) is formed into a second surface. A first end of the another inductive coil 316 is galvanically coupled at 318 to a second end of the inductive coil 314. The inductive coil 314 in the first surface and the another inductive coil 316 in the second surface are configured to form the first capacitance (C) 322 and the another inductive coil 316 in the second surface and the first feeding connection 326 in the first surface are configured to form the second capacitance (Ca) 324. The inductive coils 314, 316 are configured to receive or transmit near-field electric induction signals.
Communication in some example embodiments is by not only NFEMI, but also RF (e.g. Bluetooth). The sensor device 400 has a small volume to minimize the obstruction for the user which poses a problem for existing NFEMI antennas to be integrated without severe degradation of its performance. The sensor device 400 is suitable for measuring body parameters and wirelessly communicating the body parameters to another device.
The sensor device 400 has a housing 402 containing a carrier with the supporting circuits 330 required to sense body parameters and process then in the required way. The parameters and other information can be wirelessly communicated with another device close to the body. Additionally, an RF communication module and antenna may be integrated for long range communication. Wireless charging functions and other near field communication as NFC may also be included.
The first substrate 302 containing the near-field antenna 306 is planar and is positioned at the bottom side 406 of the sensor device 400. The bottom side 406 is designed to be attached to a user's body.
Various instructions and/or operational steps discussed in the above Figures can be executed in any order, unless a specific order is explicitly stated. Also, those skilled in the art will recognize that while some example sets of instructions/steps have been discussed, the material in this specification can be combined in a variety of ways to yield other examples as well, and are to be understood within a context provided by this detailed description.
In some example embodiments these instructions/steps are implemented as functional and software instructions. In other embodiments, the instructions can be implemented either using logic gates, application specific chips, firmware, as well as other hardware forms.
When the instructions are embodied as a set of executable instructions in a non-transitory computer-readable or computer-usable media which are effected on a computer or machine programmed with and controlled by said executable instructions. Said instructions are loaded for execution on a processor (such as one or more CPUs). Said processor includes microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. A processor can refer to a single component or to plural components. Said computer-readable or computer-usable storage medium or media is (are) considered to be part of an article (or article of manufacture). An article or article of manufacture can refer to any manufactured single component or multiple components. The non-transitory machine or computer-usable media or mediums as defined herein excludes signals, but such media or mediums may be capable of receiving and processing information from signals and/or other transitory mediums.
It will be readily understood that the components of the embodiments as generally described herein and illustrated in the appended figures could be arranged and designed in a wide variety of different configurations. Thus, the detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.
Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present invention. Thus, the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
