HK1182542B - Near field communications (nfc) devices and method for detecting a presence of near field communications (nfc) devices - Google Patents

Abstract

The present invention is directed to detecting a presence of near field communications (NFC) devices, wherein, a near field communications (NFC) device detects a presence of another NFC capable device within its magnetic field. The NFC device observes signal metrics of an observed detection signal at various intervals. The NFC device determines a statistical relationship based upon at least two first signal metrics from among the signal metrics to determine an estimate of at least one second signal metric from among the signal metrics. The NFC device compares a difference between the estimate of the signal metric of the at least one second signal metric and the at least one second signal metric. The NFC capable device makes a first determination that another NFC device is present within its magnetic field when the difference indicates that the at least one second signal metric is non-linearly related to the at least two first signal metrics.

Description

Near field communication device and method for detecting the presence of a near field communication device

Cross reference to related patent

This application claims priority to united states provisional application No. 61/566,855 filed on 5.12.2011 and united states non-provisional application No. 13/325,675 filed on 14.12.2011, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to Near Field Communication (NFC), and more particularly, to detecting the presence of an NFC-enabled device.

Background

Near Field Communication (NFC) devices are being integrated into mobile devices, such as smartphones, to facilitate their use in conducting daily transactions. For example, rather than carrying multiple credit cards, credit information provided by a credit card may be loaded into an NFC device and stored therein for use as needed. The NFC device is simply tapped to a credit card terminal to relay credit information to the terminal to complete the transaction. Another example is that ticket writing systems, such as those used in bus and train terminals, may only write fare information to NFC devices, rather than providing paper tickets to passengers. The passenger can take a bus or train without using a paper ticket by merely lightly clicking the NFC device to the reader.

Typically, NFC interaction includes a polling mode of operation, whereby communication is established between NFC devices. The first conventional method detects a magnetic field of the first conventional NFC device for the second NFC device according to a predetermined polling routine. In this first conventional method, the first conventional NFC device generates a magnetic field without any technology-dependent information for a predetermined period (often referred to as a guard time). Upon expiration of the guard time, the first legacy NFC device uses a legacy poll command to probe a magnetic field of a second NFC device of a first technology type (such as type a, type B, or type F). The legacy poll command includes a legacy request command, type a (reqa), a legacy request command, type b (reqb), or a legacy request command, type f (reqf). If no response is received from the second legacy NFC device, the first legacy NFC device generates a magnetic field without any information for another guard time and uses a legacy poll command to probe the magnetic field of the second NFC device of the second technology type. "NFCForum: NFCActivitySpecification: technical Specification, NFCForum published on 18/11/2010^TMThe first conventional method is further described in Activity1.0NFCForum-TS-Activity-1.0 ", the entire contents of which are incorporated herein by reference.

The guard time of the first conventional method unnecessarily consumes power. Typically, the guard time is about 5ms when probing NFC devices of type a and type B, and may be up to 20ms or more when probing NFC devices of type F. In addition, the first conventional NFC device may have to generate a magnetic field without any information for more than one guard time and use more than one polling command for a certain technology to detect the magnetic field. For example, a first conventional method typically polls for type a devices, then type B devices, and then type F devices. In this example, the first legacy NFC device generates a guard time for type A, B and F devices and provides REQA, REQB, and REQF commands, thereby establishing communication with type F NFC devices.

A second conventional method transmits detection pulses of substantially the same amplitude to detect the presence of an NFC device. The first NFC device continuously provides detection pulses until a change in amplitude of one of the detection pulses is detected. The change indicates the presence of the second NFC device in the magnetic field of the first NFC device. The second conventional method is further described in U.S. patent application No. 12/446,591 filed 4/22/2009, pursuant to 35u.s.c. § 371(c), the entire contents of which are incorporated herein by reference.

However, simple detection of pulse changes is susceptible to environmental changes. For example, moving the first NFC device around the environment may cause the amplitude of the detection pulse to change. Another example is that objects within the environment (such as metal objects or other NFC-nonfunctional devices) enter the magnetic field, which may cause the amplitude of the detection pulse to change. These changes may be caused by environmental changes alone and not due to the second NFC becoming present within the magnetic field. Thus, the first NFC device may erroneously determine that the second NFC device is present.

Therefore, there is a need to overcome the above-mentioned drawbacks to detect the presence of another NFC device in a magnetic field. Other aspects and advantages of the invention will become apparent from the following detailed description.

Disclosure of Invention

(1) A near field communication device comprising:

a modulator module configured to modulate the detection signal onto a carrier to provide a modulated detection signal;

an antenna module configured to apply the modulated detection signal to an inductive coupling element to generate a magnetic field that provides the detection signal;

a demodulator module configured to demodulate the detection signal to provide a recovered detection signal; and

a controller module configured to:

(i) determining a plurality of signal metrics for the recovered detection signal,

(ii) estimating at least one second signal metric of the plurality of signal metrics based on at least two first signal metrics of the plurality of signal metrics to provide an estimated value of the at least one second signal metric, an

(iii) Determining that another near field communication capable device is present in the magnetic field when the at least one second signal metric is not linearly related to the at least two first signal metrics.

(2) The near field communication device of (1), wherein the plurality of signal metrics represents at least one selected from the group consisting of: mean, total energy, average power, mean square, instantaneous power, root mean square, variance, norm, coupling coefficient, and voltage level of the recovered detection signal at different time instances.

(3) A near field communication device according to (1), wherein the detection signal is characterized as a monotonically increasing step function.

(4) A near field communication device as recited in (3), wherein the detection signal is characterized by being at a first power level for a first duration to provide a first interval, at a second power level for a second duration to provide a second interval, and at a third power level for a third duration to provide a third interval.

(5) The near field communication device of (4), wherein the first power level is less than the second power level, the second power level being less than the third power level.

(6) The near field communication device of (4), wherein the plurality of signal metrics includes a first signal metric corresponding to the first interval, a second signal metric corresponding to the second interval, and a third signal metric corresponding to the third interval.

(7) The near field communication device of (1), wherein the controller module is further configured to determine a statistical relationship based on the at least two first signal metrics, and to estimate the at least one second signal metric based on the statistical relationship.

(8) The near field communication device of (7), wherein the statistical relationship is a best fit line between the at least two first signal metrics.

(9) The near field communication device of (1), wherein the controller module is further configured to compare the at least one second signal metric to an estimated value of the at least one second signal metric to determine a difference.

(10) The near field communication device of (9), wherein the controller module is further configured to compare the difference to a threshold and determine that the at least one second signal metric is non-linearly related to the at least two first signal metrics when the difference is greater than or equal to the threshold.

(11) The near field communication device of (10), wherein the controller module is further configured to determine that the at least one second signal metric is linearly related to the at least two first signal metrics when the difference is less than the threshold, and determine that the other near field communication capable device is not present in the magnetic field when the at least one second signal metric is linearly related to the at least two first signal metrics.

(12) A method for detecting the presence of a near field communication device, comprising:

(a) modulating, by the second near field communication device, the detection signal onto a carrier wave to provide a modulated detection signal;

(b) applying, by the second near field communication device, the modulated detection signal to an inductive coupling element to generate a magnetic field that provides the detection signal;

(c) demodulating, by the second near field communication device, the detection signal to provide a recovered detection signal;

(d) determining, by the second near field communication device, a plurality of signal metrics of the recovered detection signal;

(e) estimating, by the second near field communication device, at least one second signal metric of the plurality of signal metrics based on at least two first signal metrics of the plurality of signal metrics to provide an estimated value of the at least one second signal metric, an

(f) Determining, by the second near field communication device, that the near field communication device is present in the magnetic field when the at least one second signal metric is not linearly related to the at least two first signal metrics.

(13) The method of (12), wherein the step (d) comprises:

(d) (i) determining at least one selected from the group consisting of: mean, total energy, average power, mean square, instantaneous power, root mean square, variance, norm, coupling coefficient, and voltage level of the recovered detection signal at different time instances.

(14) The method of (12), wherein the step (a) comprises:

(a) (i) modulating a monotone increasing step function onto the carrier.

(15) The method of (14), wherein the step (a) (i) comprises:

(a) (i) (a) modulating a first power level for a first duration to provide a first interval;

(a) (i) (B) modulating a second power level for a second duration to provide a second interval; and

(a) (i) (C) modulating a third power level for a third duration to provide a third interval, the first power level being less than the second power level, the second power level being less than the third power level.

(16) The method of (15), wherein the step (d) comprises:

(d) (i) determining a first signal metric corresponding to the first interval;

(d) (ii) determining a second signal metric corresponding to the second interval;

(d) (iii) determining a third signal metric corresponding to the third interval.

(17) The method of claim 12, further comprising:

(g) a statistical relationship is determined based on the at least two first signal metrics, and the at least one second signal metric is estimated based on the statistical relationship.

(18) The method of (17), wherein the step (g) comprises:

(g) (i) determining a best fit line based on the at least two first signal metrics, and estimating the at least one second signal metric based on the best fit line.

(19) The method of (12), further comprising:

(g) comparing the at least one second signal metric to an estimated value of the at least one second signal metric to determine a difference.

(20) The method of (19), further comprising:

(h) comparing the difference to a threshold and determining that the at least one second signal metric is non-linearly related to the at least two first signal metrics when the difference is greater than or equal to the threshold.

(21) The method of (20), further comprising:

(i) determining that the at least one second signal metric is linearly related to the at least two first signal metrics when the difference is less than the threshold, and determining that the near field communication device is not present in the magnetic field when the at least one second signal metric is linearly related to the at least two first signal metrics.

Drawings

Embodiments of the present invention are described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Further, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.

Fig. 1 shows a block diagram of an NFC environment according to an exemplary embodiment of the invention;

fig. 2 illustrates a conventional detection mode of operation for a first conventional NFC device to detect the presence of a second conventional NFC device;

fig. 3A shows a detection signal used by a first NFC-enabled device to detect the presence of a second NFC-enabled device within its magnetic field according to an exemplary embodiment of the present invention;

fig. 3B shows a first possible variation of a detection signal used by a first NFC-enabled device to detect the presence of a second NFC-enabled device within its magnetic field according to an exemplary embodiment of the invention;

fig. 3C shows a second possible variation of a detection signal used by a first NFC-enabled device to detect the presence of a second NFC-enabled device within its magnetic field according to an exemplary embodiment of the invention;

fig. 3D shows a third possible variation of a detection signal used by a first NFC-enabled device to detect the presence of a second NFC-enabled device within its magnetic field according to an exemplary embodiment of the invention;

fig. 4 is a flowchart of exemplary operational steps for detecting the presence of an NFC-enabled device within a magnetic field in accordance with an exemplary embodiment of the present invention;

fig. 5 shows a block diagram of an NFC device that may be used to detect the presence of other NFC-enabled devices according to an example embodiment of the present invention;

fig. 6A shows a first possible variation of a detection signal used by a first NFC-enabled device to detect a second NFC-enabled device held within its magnetic field according to an exemplary embodiment of the invention; and

fig. 6B shows a second possible variation of the detection signal used by the first NFC-enabled device to detect the second NFC-enabled device held within its magnetic field according to an exemplary embodiment of the invention.

The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.

Detailed Description

The following detailed description refers to the accompanying drawings that illustrate exemplary embodiments consistent with this invention. References in the detailed description to "one exemplary embodiment," "an example exemplary embodiment," etc., indicate that the exemplary embodiment described may include a particular feature, structure, or characteristic, but every exemplary embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same exemplary embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an exemplary embodiment, it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other exemplary embodiments whether or not explicitly described.

The exemplary embodiments described herein are for purposes of illustration and not limitation. Other exemplary embodiments are possible, and modifications may be made to the exemplary embodiments within the spirit and scope of the invention. Therefore, the detailed description is not intended to limit the invention. Rather, the scope of the invention is to be defined only by the following claims and their equivalents.

Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

The following detailed description of exemplary embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such exemplary embodiments, without undue experimentation, without departing from the spirit and scope of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the exemplary embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings herein.

Although the description of the present invention will be described in terms of NFC, one of ordinary skill in the relevant art will recognize that the present invention may be applied to other communications using the near field and/or the far field without departing from the spirit and scope of the present invention. For example, while the present invention is described using NFC-enabled communication devices, one of ordinary skill in the relevant art will recognize that the functionality of these NFC-enabled communication devices may be applied to other communication devices using the near field and/or the far field without departing from the spirit and scope of the present invention.

Exemplary Near Field Communication (NFC) Environment

Fig. 1 shows a block diagram of an NFC environment according to an exemplary embodiment of the present invention. The NFC environment 100 provides for wireless communication of information, such as one or more commands and/or data, between a first NFC device 102 and a second NFC device 104 in sufficient proximity to each other. As will be apparent to one of ordinary skill in the relevant art(s) without departing from the spirit and scope of the present invention, the first NFC device 102 and/or the second NFC device 104 may be implemented as stand-alone or discrete devices, or may be incorporated into or coupled to another electronic device or host device (such as a mobile phone, portable computing device), another computing device (such as a personal computer, notebook, or desktop computer), a computer peripheral (such as a printer, portable audio and/or video player, payment system), a ticket writing system (such as a parking ticketing system, bus ticketing system, train ticketing system, or admission ticketing system), or in a ticket reading system, toy, game, poster, packaging, advertising material, product inventory checking system, and/or any other suitable electronic device.

The first NFC device 102 detects the presence of the second NFC device 104 to enable communication of information between the first NFC device 102 and the second NFC device 104.

Legacy detection mode of operation

Conventionally, a first conventional NFC device operates in a conventional detection mode of operation to detect the presence of a second conventional NFC device. The first legacy NFC device enters a legacy polling mode of operation to establish communication with the second legacy NFC device upon detection of the second legacy NFC device.

Fig. 2 illustrates a conventional detection mode of operation used by a first conventional NFC device to detect the presence of a second conventional NFC device. The first conventional NFC device provides conventional detection pulses of substantially the same amplitude until a change in amplitude of one of the conventional detection pulses is detected. The amplitude change indicates that the second legacy NFC device has entered the magnetic field provided by the first legacy NFC device.

Upon detecting the second legacy NFC device, the first legacy NFC enters a legacy polling mode of operation to establish communication with the second legacy NFC device.

As shown in graphical illustration 202, the first conventional NFC device provides conventional detection pulses 206.1 through 206.N, each of the conventional detection pulses 206.1 through 206.N characterized as having a substantially similar amplitude. For example, the amplitude of the conventional sense pulse 206.1 is substantially similar to the amplitude of the conventional sense pulse 206.2, while the amplitude of the conventional sense pulse 206.2 is substantially similar to the amplitude of the conventional sense pulse 206. N. As further shown by the graphical illustration 202, the first legacy NFC device enters a legacy polling mode of operation 208 after the legacy detection pulse 206.N to establish communication with the second legacy NFC device. "NFCForum: NFCActivitySpecification: technical Specification, NFCForum published on 18/11/2010^TMActivity1.0NFCForum-TS-Activity-1.0, "an example of a conventional polling mode of operation 208 is described and incorporated herein by reference in its entirety.

As shown in graphical illustration 204, the first legacy NFC device observes legacy detection pulses 206.1 through 206.N, referred to as legacy observed detection pulses 210.1 through 210. N. The conventional observed detection pulses 210.1 through 210 (N-1) are characterized as having substantially similar amplitudes. The substantially similar amplitudes of the conventional observed detection pulses 210.1 through 210 (N-1) indicate that the second conventional NFC device is not present in a magnetic field. As further shown by graphical illustration 204, the amplitude of observed sense pulse 210.N is not substantially similar to the amplitude of observed sense pulse 210. (N-1). The difference in amplitude indicates that a second conventional NFC device has entered the magnetic field during the conventional detection pulse 206. N. Accordingly, the first legacy NFC device may enter a legacy polling mode of operation 208 to establish communication with the second legacy NFC device. This conventional detection mode of operation is further described in U.S. patent application No. 12/446,591, filed on 4/22/2009, the entire contents of which are incorporated herein by reference.

However, this simple change detection of the conventional detection mode is susceptible to environmental changes. For example, moving the first conventional NFC device around the environment may cause a change in the amplitude of the conventional detection pulses 206.1 to 206. N. As another example, objects in the environment (such as metal objects or other non-NFC-enabled devices) enter the magnetic field, possibly causing a change in the amplitude of the conventional detection pulses 206.1 to 206. N. However, these changes are caused by environmental changes, rather than the second conventional NFC becoming present in the magnetic field. Thus, the first conventional NFC device may incorrectly determine that a second conventional NFC device is present in a magnetic field and enter the conventional polling mode of operation 208 when the second conventional NFC device is not present in a magnetic field.

In general, these changes due to the environment can be characterized as linear. However, the variation due to another NFC-enabled device becoming present within the magnetic field may be characterized as non-linear. For example, when other NFC-enabled devices enter a magnetic field, they begin to get or acquire power, which causes a non-linear change in the magnetic field. However, conventional detection modes of operation cannot distinguish between linear and non-linear variations; thus, the conventional detection mode is prone to misinterpret the environmental change as being an indication that the second conventional NFC is present in a magnetic field.

Exemplary detection mode of operation

The invention is able to distinguish between linear and non-linear changes, so that changes in the detection signal of the invention, characterized as linear, can be identified as environmental changes. These variations of the detection signal of the present invention, characterized as non-linear, can be expressed as a result of another NFC-functional device becoming present in the magnetic field.

Fig. 3A shows a detection signal used by a first NFC-enabled device to detect the presence of a second NFC-enabled device in its magnetic field according to an exemplary embodiment of the present invention. Generally, a first NFC-enabled device (e.g., first NFC device 102) is configured to operate in an initiator or reader mode of operation and a second NFC-enabled device (e.g., second NFC device 104) is configured to operate in a recipient or tag mode of operation.

The first NFC-enabled device provides a magnetic field representative of the detection signal 302 to detect the presence of the second NFC-enabled device in its magnetic field. The detection signal 302 is characterized as a monotonically increasing and/or monotonically decreasing function, such as a monotonically increasing step or step function. In an exemplary embodiment, the first NFC enabled device may provide a plurality of detection signals 302 to form a detection sequence. In this exemplary embodiment, the plurality of detection signals 302 in the detection sequence are provided in temporally separated intervals. For example, the first NFC-enabled device may periodically provide each detection signal 302 in the detection sequence. As another example, the first NFC device may provide each detection signal 302 in the detection sequence in response to an event. As another example, the first NFC-enabled device may provide each detection signal 302 from the detection sequence at a different time.

As shown in fig. 3A, the first NFC-enabled device is for a first duration t₁At a first power level p₁The detection signal 302 is provided to provide a first interval 304.1. Generally, the detection signal 302 represents a waveform modulated onto a carrier wave; however, for clarity, only the envelope of the modulated carrier is shown in fig. 3A to 3D. The first NFC-enabled device then changes the power level of the detection signal 302 from the first power level p₁Adjusted to a second power level p₂And for a second duration t₂At a second power level p₂The detection signal 302 is provided to provide a second interval 304.2. However, the device is not suitable for use in a kitchenThereafter, the first NFC-enabled device changes the power level of the detection signal 302 from the second power level p₂Adjusted to a third power level p₃And for a third duration t₃At a third power level p₃The detection signal 302 is provided to provide a third interval 304.3. However, the detection signal 302 shown in fig. 3A is for illustration purposes only, and one of ordinary skill in the relevant art will recognize that the detection signal 302 may include any suitable number of intervals without departing from the spirit and scope of the present invention.

In an exemplary embodiment, the first power level p₁Below a second power level p₂And a second power level p₂Below a third power level p₃. In another exemplary embodiment, the lowest power level (e.g., the first power level p)₁) With a sufficient power level to allow the second NFC-enabled device to derive power from the detection sequence 300 upon entering a magnetic field. In another exemplary embodiment, the first duration t₁A second duration t₂And/or a third duration t₃Of sufficient duration (e.g., may be about 20 microseconds) to allow stabilization of the magnetic field generated thereby.

The first NFC-enabled device detects its magnetic field change by observing detection signal 302 to provide an observed detection signal 306. The first NFC-enabled device observes, from the observed detection signal 306, a first signal metric 308.1 corresponding to the first interval 304.1, a second signal metric 308.2 corresponding to the second interval 304.2, and a third signal metric 308.3 corresponding to the third interval 304.3. The first signal metric 308.1, the second signal metric 308.2, and/or the third signal metric 308.3 may represent an average, a total energy, an average power, a mean square, an instantaneous power, a root mean square, a variance, a norm, a voltage level, a coupling coefficient, and/or any other suitable signal metric that would be apparent to one of ordinary skill in the relevant art for their corresponding intervals 304.1 through 304.3.

Based on the first and second ones of the signal metrics 308.1-308.3, the first NFC-enabled device determines a statistical relationship 312 to determine a signal metric estimate 310 (which represents an estimate of a third one of the signal metrics 308.1-308.3). For example, the first NFC-enabled device may use the first signal metric 308.1 and the second signal metric 308.2 to statistically determine a best fit line as the statistical relationship 312. As another example, the first NFC-enabled device may statistically determine a best-fit suitable curve (e.g., a quadratic polynomial, a cubic polynomial, a higher order polynomial, or any combination thereof) as the statistical relationship 312 using the first signal metric 308.1 and the second signal metric 308.2. The first NFC-enabled device may determine an estimate of the third signal metric 308.3 as the signal metric estimate 310 using a best fit line and/or a best fit suitable curve.

The first NFC-enabled device compares the first signal metric estimate 310 and the third signal metric to determine a difference between the signal metrics. In other words, the first NFC-enabled device compares the actual representation value and the estimated value of the third signal metric to determine a difference thereof. When the difference indicates that the signal metric estimate 310 is linearly related to the first signal metric and the second signal metric, the first NFC-enabled device makes a first determination that the second NFC-enabled device is not present in its magnetic field. Alternatively, when the difference indicates that the signal metric estimate 310 is not linearly (i.e., non-linearly) related to the first signal metric and the second signal metric, the first NFC-enabled device makes a second determination that a second NFC-enabled device is present in its magnetic field. In an exemplary embodiment, the first NFC enabled device may compare the difference between the third signal metric and the signal metric estimate 310 to a threshold and make a first determination when the difference is less than the threshold or make a second determination when the difference is greater than or equal to the threshold.

For example, as shown in fig. 3B, the first NFC-enabled device observes a first signal metric 308.1, a second signal metric 308.2, and a third signal metric 308.3 from the observed detection signal 306. The first NFC-enabled device statistically determines a best fit line as a statistical relationship 312 using the first signal metric 308.1 and the second signal metric 308.2 to determine a signal metric estimate 310 representing an estimate of the third signal metric 308.3. The first NFC-enabled device compares the third signal metric 308.3 and the signal metric estimate 310 and determines that the signal metric 308.3 is linearly related to the first signal metric 308.1 and the second signal metric 308.2. Since the signal metric estimate 310 is linearly related to the first signal metric 308.1 and the second signal metric 308.2, the first NFC-enabled device makes a first determination that the second NFC-enabled device is not present in its magnetic field.

Objects in the environment (such as metal objects or other non-NFC-enabled devices) may enter the magnetic field of the first NFC-enabled device. These objects may cause the third signal metric 308.3 to be linearly related to the signal metric estimate 310. However, as shown in FIG. 3C, these objects may cause the expected detection signal 314 of the detection signal 302 to be different from the observed detection signal 306. Optionally, the first NFC-enabled device may compare the first signal metric 308.1 to an expected signal metric for the first interval 304.1 and/or the second signal metric 308.2 to an expected signal metric for the second interval 304.2 to determine a difference between the observed detected signal 306 and the expected detected signal 314. The expected signal metric for the first interval 304.1 and/or the expected signal metric for the second interval 304.2 represent the signal metrics for the first interval 304.1 and the second interval 304.2, respectively, which occurs when no other objects are present in the environment.

When the observed detection signal 306 differs significantly from the expected detection signal 314, the first NFC-enabled device makes a third determination that the object present in its magnetic field is not a second NFC device. Alternatively, when the observed detected signal 306 is substantially the same as the expected detected signal 314, the first NFC-enabled device makes a fourth determination that no other object is present in its magnetic field. In an example embodiment, the first NFC-enabled device may compare the difference between the observed detection signal 306 and the expected detection signal 314 to a threshold and make a third determination when the difference is less than the threshold or make a fourth determination when the difference is greater than or equal to the threshold.

Typically, the second NFC-enabled device derives or obtains power from the detection signal 102. After sufficient power is obtained from the detection signal 302, the second NFC capable device is turned on. The switching on of the second NFC enabled device and the harvesting of power may result in a non-linear change in the magnetic field of the first NFC enabled device. Alternatively, when the second NFC-enabled device is a power NFC device (poweredNFCdevice) that does not derive power from a magnetic field, a nonlinear change or coupling field may be seen when a shunt regulator in the second NFC-enabled device limits the voltage on its antenna element.

For example, as shown in fig. 3D, the first NFC-enabled device observes a first signal metric 308.1, a second signal metric 308.2, and a third signal metric 308.3 from the observed detection signal 306. The first NFC-enabled device statistically determines a best fit line as a statistical relationship 312 using the first signal metric 308.1 and the second signal metric 308.2 to determine a signal metric estimate 310 representing an estimate of the third signal metric 308.3.

The first NFC-enabled device compares the third signal metric 308.3 with the signal metric estimate 310 to determine that the signal metric 308.3 is non-linearly related to the first signal metric 308.1 and the second signal metric 308.2. Since the signal metric estimate 310 is non-linearly related to the first signal metric 308.1 and the second signal metric 308.2, the first NFC-enabled device makes a second determination that a second NFC-enabled device is present in its magnetic field.

It should be noted that the linear variation shown in fig. 3C and the non-linear variation shown in fig. 3D are for illustrative purposes only, and one of ordinary skill in the relevant art will recognize that other linear and/or non-linear variations are possible without departing from the spirit and scope of the present invention.

Referring again to fig. 1, upon detecting the presence of the second NFC enabled device 104 in its magnetic field, the first NFC enabled device 102 may enter a polling mode (such as the conventional polling mode of operation 208 or any other suitable polling mode as would be apparent to one of ordinary skill in the relevant art) to establish communication with the second NFC enabled device without departing from the spirit and scope of the present invention.

The first NFC device 102 modulates its respective information onto a carrier wave and generates a first magnetic field by applying the modulated information communication to a first antenna to provide a first information communication 152. The first NFC device 102 continues to apply the first carrier without its corresponding information to continue to provide the first communication of information 152 when the information has been transferred to the second NFC device 104. The first NFC device 102 is in sufficient proximity to the second NFC device 104 such that the first information communication 152 is inductively coupled to the second antenna of the second NFC device 104.

The second NFC device 104 derives or obtains power from the first information communication 152 to recover, process, and/or provide a response to the information. The second NFC device 104 demodulates the first information communication 152 to recover and/or process the information. The second NFC device 104 may respond to its respective information by applying the information to a first carrier inductively coupled to a second antenna to provide a second modulated information communication 154.

Further operations of the first NFC device 102 and/or the second NFC device 104 are described in International Standard ISO/IE18092:2004(E), "information technology-Telecommunications and information exchange BetWeenches systems-near field communication-Interface and protocol (NFCIP-1)" published 4/1 in 2004, and International Standard ISO/IE21481:2005(E), "information technology-near field communication and information exchange BetWestsystems-near field communication-Interface and protocol-2(NFCIP-2) published 1/15 in 2005," further operations published by the first NFC device 102 and/or the second NFC device 104 are described herein in their entirety and incorporated by reference.

Although fig. 1 and 3A-3D have been described with respect to initiator mode operation and recipient mode operation, one of ordinary skill in the relevant art will recognize that the first NFC device 102 and/or the second NFC device 104 depicted in fig. 1 and/or the first NFC capable device and/or the second NFC capable device depicted in fig. 3A-3D may alternatively be configured to operate in a communication mode of operation (communicative) without departing from the spirit and scope of the present invention. These NFC devices and/or NFC-enabled devices may be configured to operate in initiator mode operation and/or recipient mode operation, and may switch between these modes of operation in a communication mode of operation.

Method for detecting NFC-functional devices

Fig. 4 is a flowchart of exemplary operational steps for detecting the presence of an NFC-enabled device in a magnetic field, in accordance with an exemplary embodiment of the present invention. The present invention is not limited to this operational description. Rather, it will be apparent to those of ordinary skill in the relevant art in view of the teachings herein that other operational control flows are within the scope and spirit of the present invention. The following discussion describes the steps in fig. 4.

At step 402, the operational control flow provides a magnetic field representative of an interval of a detection signal (such as one of the detection signals 302). For example, the detection signal may be resolved into a plurality of intervals such as intervals 304.1 to 304.3. Each of the plurality of intervals is characterized as having a corresponding power level p and a corresponding duration t. The operational control flow provides one of these multiple intervals for its corresponding duration t at its corresponding power level p.

At step 404, the operational control flow observes the signal metrics from the interval of step 402.

In step 406, the operational control flow determines whether the detection signal includes more intervals. If so, the operational control flow returns to step 402 to provide another interval of the detected signal at its corresponding power level p for its corresponding duration t. Otherwise, the operation control flow proceeds to step 408.

At step 408, the operational control flow selects one of the intervals from step 402 and estimates a signal metric for the selected interval. For example, the operational control flow may statistically determine a best fit line using the signal metrics of the unselected intervals observed in step 404. In another example, the operational control flow may use the signal metrics of the unselected intervals observed in step 404 to statistically determine a suitable curve (such as a quadratic polynomial, a cubic polynomial, a higher order polynomial, or any combination thereof) that best fits. The operational control flow may use a best-fit line or a best-fit appropriate curve to estimate the selected interval.

At step 410, the operational control flow compares the difference between the signal metric observed at step 404 from the selected interval of step 408 and the signal metric selected at step 408 for the interval estimated at step 408 with a threshold. When the difference is less than the threshold, the operational control flow makes a first determination that the interval selected from step 408 is linearly related to the interval not selected from step 408, indicating that another device is not present in its magnetic field. The operational control flow returns to step 402 to provide another detection signal. Otherwise, when the difference is greater than or equal to the threshold, the operational control flow makes a second determination that the interval selected from step 408 is non-linearly related to the interval not selected from step 408, indicating that another device is present in its magnetic field. The operation control flow proceeds to step 412.

At step 412, the operational control flow begins a polling mode operation to establish communication with the devices present in its magnetic field.

Exemplary NFC device

Fig. 5 shows a block diagram of an NFC device that may be used to detect the presence of other NFC-enabled devices according to an example embodiment of the present invention. The NFC device 500 may be configured to operate in a detection mode of operation to detect the presence of another NFC-enabled device in its magnetic field. It should be noted that fig. 5 only illustrates a detection mode of operation, and one of ordinary skill in the relevant art will recognize that NFC device 500 may be configured to operate in other modes of operation, such as a point-to-point (P2P) communication mode or a read/writer (R/W) communication mode, without departing from the spirit and scope of the present invention. NFC device 500 includes a controller module 502, a modulator module 504, an antenna module 506, and a demodulator module 508. The NFC device 500 may represent an exemplary embodiment of the first NFC device 102. The controller module 502 controls the overall operation and/or configuration of the NFC device 500. In the detection mode of operation, the controller module 502 generates a detection signal 552 (e.g., such as the detection signal 302). The detection signal 552 may represent a monotonically increasing and/or decreasing function.

The controller module 502 may generate the detection signal 552 in response to a command. Commands may be provided to the controller module 502 from one or more data storage devices, such as one or more contactless transponders, one or more contactless tags, one or more contactless smart cards, and other machine-readable media as would be apparent to one of ordinary skill in the relevant art, or a combination thereof, without departing from the spirit and scope of the present invention. Other machine-readable media may include, but are not limited to: read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, electrical, optical, acoustical or other form of propagated signals (such as carrier waves, infrared signals, digital signals). The controller module 502 may also receive commands from a user interface such as a touch screen display, alphanumeric keypad, microphone, mouse, speaker, and other suitable user interfaces as would be apparent to one of ordinary skill in the relevant art without departing from the spirit and scope of the present invention. Controller module 502 may further receive commands from other electronic devices or host devices coupled to NFC device 500.

Modulator module 504 modulates sense signal 552 onto a carrier wave (e.g., a radio frequency carrier wave such as having a frequency of about 13.56 MHz) using any suitable analog or digital modulation technique to provide modulated sense signal 554. Suitable analog or digital modulation techniques may include Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation (PM), Phase Shift Keying (PSK), Frequency Shift Keying (FSK), Amplitude Shift Keying (ASK), Quadrature Amplitude Modulation (QAM), and/or any other suitable modulation technique that will be apparent to one of ordinary skill in the relevant art. In an exemplary embodiment, the modulator module 504 may include a Direct Digital Synthesizer (DDS) controlled by the controller module 502 to generate the detection signal 552. In the exemplary embodiment, modulator module 504 further includes an analog-to-digital converter (ADC) to convert sense signal 552 from a digital representation to an analog representation based on a carrier to provide a modulated sense signal 554.

The antenna module 506 applies the modulated detection signal 554 to an inductive coupling element, such as a resonance tuning circuit, to generate a magnetic field to provide a detection sequence 556. The antenna module 506 observes the detected sequence 556 to provide an observed detected sequence 558.

Demodulator module 508 demodulates observed detected sequence 558 using any suitable analog or digital modulation technique to provide recovered detected signal 560. Suitable analog or digital modulation techniques may include Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation (PM), Phase Shift Keying (PSK), Frequency Shift Keying (FSK), Amplitude Shift Keying (ASK), Quadrature Amplitude Modulation (QAM), and/or other suitable modulation techniques that may be apparent to one of ordinary skill in the relevant art.

Controller module 502 may determine a plurality of signal metrics for recovered detection signal 560. The plurality of signal metrics may include an average voltage and/or current level, an instantaneous voltage and/or current, a root mean square voltage and/or current level, an average power (mean power), an average power (averagepower), an instantaneous power, a root mean square power, a signal envelope, and/or any other suitable signal metric that would be apparent to one of ordinary skill in the relevant art without departing from the spirit and scope of the present invention. For example, controller module 502 may determine a plurality of signal metrics for recovered detection signal 560 at different time instances.

The controller module 502 determines a statistical relationship based on at least two first signal metrics of the plurality of signal metrics to determine an estimated value of at least one second signal metric of one of the plurality of signal metrics. The controller module 502 compares the estimated value of the at least one second signal metric with the at least one second signal metric to determine a difference between the signal metrics. When the difference indicates that the at least one second signal metric is linearly related to the at least two first signal metrics, the controller module 502 makes a first determination that another NFC-enabled device is not present in the magnetic field. Alternatively, when the difference indicates that the at least one second signal metric is not linearly (i.e., non-linearly) related to the at least two first signal metrics, the first NFC-enabled device makes a second determination that another NFC-enabled device is present in the magnetic field. In an exemplary embodiment, the controller module 502 may compare a difference between the at least one second signal metric and the estimated value of the at least one second signal metric to a threshold and make a first determination when the difference is less than the threshold or make a second determination when the difference is greater than or equal to the threshold.

Referring again to fig. 3A, upon detecting the presence of the second NFC-enabled device in its magnetic field, the first NFC-enabled device may continue to provide a detection signal 302 to confirm that the second NFC-enabled device is still retained in its magnetic field, as described in fig. 3A-3D. For example, as shown in fig. 6A, the first NFC-enabled device detects its magnetic field changes by observing the detection signal 302 to provide an observed detection signal 602. The first NFC-enabled device observes, from the observed detection signal 602, a first signal metric 604.1 corresponding to the first interval 304.1, a second signal metric 604.2 corresponding to the second interval 304.2, and a third signal metric 604.3 corresponding to the third interval 304.3. The first signal metric 604.1, the second signal metric 604.2, and/or the third signal metric 604.3 may represent an average, a total energy, an average power, a mean square, an instantaneous power, a root mean square, a variance, a norm, a voltage level, a coupling factor, and/or any other suitable signal metric that would be apparent to one of ordinary skill in the relevant art for their corresponding intervals 304.1 through 304.3.

The first NFC-enabled device determines a statistical relationship 608 from at least two of the signal metrics 604.1-604.3, and determines a signal metric estimate 606 representing at least one second of the signal metrics 604.1-604.3 in a substantially similar manner as described in fig. 3A-3D to determine the presence of the second NFC-enabled device in its magnetic field.

Typically, when the second NFC-enabled device is no longer present in the magnetic field, it no longer derives or obtains power from the detection signal 302. When the second NFC-enabled device has left the magnetic field, the first NFC-enabled device may observe a change in the observed signal metric of the detection signal 602, e.g., an increase and/or decrease in the signal.

For example, as shown in fig. 6B, after detecting the presence of the second NFC-enabled device, the first NFC-enabled device observes, from another observed detection signal 612, a first signal metric 610.1 corresponding to the first interval 304.1, a second signal metric 610.2 corresponding to the second interval 304.2, and a third signal metric 610.3 corresponding to the third interval 304.3 in response to the other detection signal 302. The first NFC-enabled device compares the first signal metric 604.1, the second signal metric 604.2, and/or the third signal metric 604.3 to their corresponding first signal metric 610.1, second signal metric 610.2, and/or third signal metric 610.3 to determine whether the difference between these signal metrics indicates that the second NFC-enabled device is no longer present in its magnetic field. The first signal metric 610.1, the second signal metric 610.2, and/or the third signal metric 610.3 may represent an average, total energy, average power, mean square, instantaneous power, root mean square, variance, norm, voltage level, coupling factor, and/or any other suitable signal metric that would be apparent to one of ordinary skill in the relevant art for their corresponding intervals 304.1 through 304.3.

Typically, when the first NFC-enabled device observes at least one difference between corresponding signal metrics, the first NFC-enabled device makes a fifth determination that the second NFC device is no longer present in its magnetic field. Alternatively, when the first NFC-enabled device does not observe the difference between these corresponding signal metrics, the first NFC-enabled device makes a sixth determination that the second NFC device is still present in its magnetic field. In an exemplary embodiment, the first NFC-enabled device may compare the difference between these corresponding signal metrics to a threshold and make a fifth determination when the difference is greater than or equal to the threshold or make a sixth determination when the difference is less than the threshold.

As further shown in fig. 6B, the third signal metric 610.3 is greater than the third signal metric 604.3, indicating that the second functional NFC device is no longer present in the magnetic field of the first NFC-functional device. When the first NFC-enabled device observes that the third signal metric 604.3 differs from the third signal metric 610.3, the first NFC-enabled device makes a fifth determination that the second NFC device is no longer present in its magnetic field. However, this example is not limiting, and other differences between the first signal metric 604.1 and the first signal metric 610.1 and/or the second signal metric 604.2 and the second signal metric 610.2 may also indicate that the second NFC device is no longer present in the magnetic field of the first NFC-enabled device.

Optionally, the first NFC-enabled device may enter a polling mode of operation to confirm that the second NFC device is no longer present in its magnetic field.

It should be noted that the linear variation shown in fig. 6A and the non-linear variation shown in fig. 6B are for illustrative purposes only, and one of ordinary skill in the relevant art will recognize that other linear and/or non-linear variations are possible without departing from the spirit and scope of the present invention.

Conclusion

It is to be understood that the detailed description section, and not the abstract section, is intended to be used to interpret the claims. The abstract may set forth one or more, but not all exemplary embodiments of the invention, and is thus not intended to limit the invention and the appended claims in any way.

The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Other boundaries may be defined so long as the specified functions and relationships thereof are appropriately performed.

It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims (8)

1. A near field communication device comprising:

a modulator module configured to modulate a detection signal onto a carrier to provide a modulated detection signal, the detection signal being at a first power level for a first duration to provide a first interval, at a second power level for a second duration to provide a second interval, and at a third power level for a third duration to provide a third interval, the second power level being higher than the first power level;

an antenna module configured to apply the modulated detection signal to an inductive coupling element to generate a magnetic field that provides the detection signal;

a demodulator module configured to demodulate the detection signal to provide a recovered detection signal; and

a controller module configured to:

determining a first signal metric and a second signal metric of the recovered detected signal, the first signal metric corresponding to the first interval and the second signal metric corresponding to the second interval,

estimating a signal metric estimate for the recovered detected signal based on a statistical relationship between the first signal metric and the second signal metric;

determining a third signal metric for the recovered detected signal, the third signal metric corresponding to the third interval, an

Comparing a difference between the signal metric estimate and the third signal metric to a threshold to determine whether the third signal metric is non-linearly related to the first signal metric and the second signal metric, the non-linear correlation indicating the presence of a second near field communication device in the magnetic field.

2. Near field communication device according to claim 1, wherein the first, second and third signal metrics represent at least one selected from the group consisting of: mean, total energy, average power, mean square, instantaneous power, root mean square, variance, norm, coupling coefficient, and voltage level of the recovered detection signal at different time instances.

3. Near field communication device according to claim 1, wherein the detection signal is characterized by a monotonically increasing step function.

4. The near field communication device of claim 1, wherein the statistical relationship is a best fit line between the first signal metric and the second signal metric.

5. The near field communication device of claim 1, wherein the controller module is further configured to compare the signal metric estimate to the third signal metric to determine a difference.

6. The near field communication device of claim 1, wherein the controller module is further configured to determine that the second near field communication device is present in the magnetic field when the difference is greater than or equal to the threshold value.

7. The near field communication device of claim 1, wherein the controller module is further configured to determine that the second near field communication device is not present in the magnetic field when the difference is less than the threshold.

8. A method for detecting the presence of a near field communication device, comprising:

(a) modulating, by a second near field communication device, a detection signal onto a carrier wave to provide a modulated detection signal, the detection signal being at a first power level for a first duration to provide a first interval, at a second power level for a second duration to provide a second interval, and at a third power level for a third duration to provide a third interval, the second power level being higher than the first power level;

(b) applying, by the second near field communication device, the modulated detection signal to an inductive coupling element to generate a magnetic field that provides the detection signal;

(c) demodulating, by the second near field communication device, the detection signal to provide a recovered detection signal;

(d) determining, by the second near field communication device, a first signal metric and a second signal metric of the recovered detected signal, the first signal metric corresponding to the first interval and the second signal metric corresponding to the second interval;

(e) estimating, by the second near field communication device, a signal metric estimate of the recovered detected signal based on a statistical relationship between the first signal metric and the second signal metric; (f) determining, by the second near field communication device, a third signal metric of the recovered detected signal, the third signal metric corresponding to the third interval; and

(g) comparing, by the second near field communication device, a difference between the signal metric estimate and the third signal metric to a threshold to determine whether the third signal metric is non-linearly related to the first signal metric and the second signal metric, the non-linear correlation indicating the presence of the first near field communication device in the magnetic field.