HK1186311B - 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. A near field communications (NFC) device is disclosed that detects a presence of another NFC capable device within its magnetic field. The NFC device generates an unmodulated frequency varying detection sequence to generate a frequency varying magnetic field and/or a modulated frequency invariant detection sequence to generate a carrier-frequency invariant magnetic field. The NFC device samples these magnetic fields and compares these samples to various a priori known responses of various objects to determine whether another NFC device is present within the frequency varying magnetic field and/or the carrier-frequency invariant magnetic field.

Description

Presence detection for Near Field Communication (NFC) devices

Technical Field

The present disclosure relates to Near Field Communication (NFC), and more particularly to detecting the presence of an NFC capable device (NFCcapabledevice).

Background

Near Field Communication (NFC) devices are integrated into mobile devices, such as smart phones, for example, to facilitate their use in conducting daily transactions. For example, instead of carrying a large number of credit cards, the credit information provided by these credit cards may be loaded into the NFC device and stored therein for use when needed. The NFC device is only tapped to the credit card terminal to relay credit information to the terminal to complete the transaction. As another example, a ticket writing system such as a terminal used in buses and trains may only write ticket fare information into NFC devices without providing a paper ticket to a passenger. The passenger can take a bus or train without using a paper ticket by only touching the NFC device to the reader.

Generally, NFC includes a polling mode of operation to establish communication between NFC devices. A first conventional method probes the magnetic field of a first conventional NFC device for a second NFC device according to a predetermined polling procedure. In this first conventional method, a first conventional NFC device generates a magnetic field without any information for a predetermined duration of time, commonly referred to as a guard time (guard time), which is technology dependent. Thereafter, the first conventional NFC device probes the magnetic field for a second NFC device of the first technology type (such as type a, B, or F, for example) at the end of the guard time using a conventional polling command. The conventional polling command includes such a conventional request command type a (REQA), a conventional request command type B (REQB), or a conventional request command type F (REQF).Thereafter, the first conventional NFC device generates a magnetic field without any information for another guard time, and if no response is received from the second conventional NFC device, the magnetic field for the second NFC device of the second technology type is probed with a conventional polling command. "NFC forum published on 11/18/2010: description of NFC actions: technical description, NFC Forum^TMAction 1.0NFC Forum TS action 1.0 "(" NFCForum: NFCActivitySpecification: technical Specification, NFCForum)^TMActivity1.0nfcforum-TS-Activity-1.0 "), which is incorporated herein by reference without loss of its integrity. Other technologies may also be employed, such as, but not limited to, ISO15693 proximity cards, for example.

The guard time of the first conventional method unnecessarily consumes power. Typically, the guard time is about 5ms when probing type a and type B NFC devices and may be up to 20ms or more when probing type F NFC devices. Furthermore, the first conventional NFC device has to generate a magnetic field without any information for more than one guard time and for some technologies to detect the magnetic field with more than one polling command. For example, a first conventional approach typically polls a type a devices, then polls B devices, and then polls F devices. In such an example, a first type of conventional NFC device generates guard times for type a, B, and F devices and issues REQA, REQB, and REQF commands to establish communication with the F type NFC device.

A second conventional method transmits detection pulses having substantially similar amplitudes to detect the presence of an NFC device. The first NFC device continuously emits detection pulses until a change in amplitude of one of the detection pulses is detected. The change indicates a second NFC device within the magnetic field of the first NFC device. In U.S. patent application No. filed 4 month 22, 2009, under 35u.s.c. § 371 (c): 12/446,591, which is incorporated herein by reference for all purposes without loss of its integrity.

However, such simple pulse change detection is susceptible to environmental changes. For example, moving the first NFC device in the environment may cause a change in the amplitude of one or more detection pulses. As another example, an object in the environment that enters the magnetic field, such as a metal object or other non-NFC capable device, for example, may cause a change in the amplitude of one or more detection pulses. These changes may be caused by changes in the environment only, and not by the second NFC that is entering a magnetic field. Thus, the first NFC device may incorrectly determine that the second NFC device is present.

Therefore, there is a need to detect the presence of another NFC device in a magnetic field that overcomes the above-mentioned disadvantages. Other aspects and advantages of the present disclosure will become apparent as the following detailed description proceeds.

Disclosure of Invention

(1) A method for detecting a presence of a first Near Field Communication (NFC) capable device, comprising:

(a) generating, by the second near field communicable device, a magnetic field to detect a presence of the near field communicable device;

(b) comparing the magnetic field with an a priori known response of the first near field communicable device to the magnetic field; and

(c) determining that the first near-field communicable device is present in the environment of the second near-field communicable device when the magnetic field substantially matches the a priori known response.

(2) The method of (1), wherein step (a) comprises:

(a) (i) generating a variable frequency magnetic field to detect the presence of the near field communicable device.

(3) The method of (2), wherein step (a) (i) comprises:

(a) (i) (1) applying a plurality of detection signals to an inductive coupling element to generate the variable frequency magnetic field, each of the plurality of detection signals characterized by a different one of a plurality of frequencies.

(4) The method of (3), wherein step (a) (i) (1) comprises:

(a) (I) (1) (I) applying a first detection signal of the plurality of detection signals including a first carrier wave having a first frequency of the plurality of frequencies over a first time period to generate a first magnetic field; and

(a) (i) (1) (II) applying a second detection signal of the plurality of detection signals including a second carrier wave having a second frequency of the plurality of frequencies over a second time period to generate a second magnetic field,

wherein the variable frequency magnetic field comprises the first magnetic field and the second magnetic field.

(5) The method of (1), wherein step (a) comprises:

(a) (i) generating a carrier frequency constant magnetic field to detect the presence of the near field communicable device.

(6) The method of (5), wherein (a) (i) comprises:

(a) (i) (1) applying a detection signal to an inductive coupling element to generate the carrier frequency constant magnetic field, the detection signal characterized by an electronic signal modulated with a carrier wave having more than one period.

(7) The method of (6), wherein step (a) (i) (1) comprises:

(a) (I) (1) (I) modulating a first period of said electronic signal with said carrier wave having a first frequency to provide a first modulated period; and

(a) (i) (1) (II) modulating said electronic signal for a second period with said carrier wave having said first frequency to provide a second modulated period;

(a) (i) (1) (III) applying the first and second modulated periods to the inductive coupling element to generate the carrier frequency constant magnetic field.

(8) The method of (1), further comprising:

(d) sampling, by the second near field communicable device, the magnetic field; and

(e) transforming samples of the magnetic field from a time domain representation to a frequency domain representation, an

Wherein step (c) comprises:

(c) (ii) (i) comparing in the frequency domain the characterization in the frequency domain of the samples of the magnetic field and the samples of the a priori known response.

(9) The method of (1), wherein step (c) comprises:

(c) determining that the magnetic field substantially matches the a priori known response when the magnetic field differs from the a priori known response by a threshold amount.

(10) The method of (1), wherein step (c) comprises:

(c) determining that the magnetic field substantially matches the a priori known response when the magnetic field is substantially the same as the a priori known response.

(11) A first Near Field Communication (NFC) enabled device, comprising:

a demodulator module configured to reconstruct a detection sequence from a magnetic field configured to detect a presence of a second near-field communicable apparatus; and

a controller module configured to compare the magnetic field with an a priori known response of the first near field communicable device to the magnetic field and determine that the second near field communicable device is present in the environment of the first near field communicable device when the magnetic field substantially matches the a priori known response.

(12) The first near field communication device of (11), wherein the magnetic field is characterized as a variable frequency magnetic field.

(13) The first near-field communication device of (12), further comprising:

an antenna module configured to apply a plurality of detection signals to an inductive coupling element to generate the variable frequency magnetic field, each of the plurality of detection signals characterized by a different one of a plurality of frequencies.

(14) The first near-field communication device of (13), wherein the antenna module is further configured to apply a first detection signal of the plurality of detection signals including a first carrier wave having a first frequency of the plurality of frequencies for a first time period to generate a first magnetic field and to apply a second detection signal of the plurality of detection signals including a second carrier wave having a second frequency of the plurality of frequencies for a second time period to generate a second magnetic field,

wherein the variable frequency magnetic field comprises the first magnetic field and the second magnetic field.

(15) The first near-field communication device of (11), wherein the magnetic field is characterized as a carrier frequency constant magnetic field.

(16) The first near field communication device of (15), wherein step (a) (i) comprises:

an antenna module configured to apply a detection signal characterized by rectangular pulses modulated with a carrier wave having more than one period to an inductive coupling element to generate the carrier frequency constant magnetic field.

(17) The first near-field communication device of (16), further comprising:

a modulator configured to modulate the rectangular pulse of a first period with the carrier wave having a first frequency to provide a first modulated period and to modulate the rectangular pulse of a second period with the carrier wave having the first frequency to provide a second modulated period,

wherein the antenna module is further configured to apply the first modulated period and the second modulated period to the inductive coupling element to generate the carrier frequency constant magnetic field.

(18) The first near-field communication device of (11), wherein the controller module is further configured to sample the magnetic field, transform the samples of the magnetic field from a time-domain representation to a frequency-domain representation, and compare the samples of the magnetic field in the frequency domain with representations of the samples of the a priori known response in the frequency domain.

(19) The first near-field communication device of (11), wherein the controller module is further configured to determine that the magnetic field substantially matches the a priori known response when the magnetic field differs from the a priori known response by a threshold amount.

(20) The first near-field communication device of (11), wherein the controller module is further configured to determine that the magnetic field substantially matches the a priori known response when the magnetic field is substantially the same as the a priori known response.

Drawings

Embodiments of the present disclosure 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 figure in which the reference number first appears.

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

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;

fig. 3A graphically illustrates a first frequency detection sequence that may be used by a first NFC-enabled device to detect the presence of a second NFC-enabled device according to an exemplary embodiment of the present disclosure;

FIG. 3B graphically illustrates a frequency domain characterization of a first frequency detection sequence, according to an example embodiment of the present disclosure;

fig. 4A graphically illustrates a second frequency detection sequence that may be used by a first NFC-enabled device to detect a second NFC-enabled device in accordance with an exemplary embodiment of the present disclosure;

FIG. 4B graphically illustrates a characterization of the frequency domain of a second frequency detection sequence, according to an example embodiment of the present disclosure;

fig. 5 is a flowchart of exemplary operational steps for detecting the presence of a NFC capable device within an environment, according to an exemplary embodiment of the present disclosure;

FIG. 6A illustrates a priori known responses of a plurality of various objects to a variable frequency magnetic field (frequency variable in magnetic field), according to an exemplary embodiment of the present disclosure;

FIG. 6B illustrates a priori known responses of a plurality of various objects to a carrier-frequency constant magnetic field (carrier-frequency in variable magnetic field), according to an exemplary embodiment of the present disclosure;

fig. 7 is a second flowchart of exemplary operational steps for detecting the presence of a NFC-enabled device within an environment, according to an exemplary embodiment of the present disclosure; and

fig. 8 illustrates a block diagram of an NFC capable device that may be used to detect the presence of other NFC capable devices according to an example embodiment of the present disclosure.

The present disclosure 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 in accordance with the disclosure. References in the detailed description to "one exemplary embodiment," "an example exemplary embodiment," etc., indicate that the 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 example embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an exemplary embodiment, it will be understood by those skilled in the art that such feature, structure, or characteristic may be modified in connection with other exemplary embodiments whether or not explicitly described.

The exemplary embodiments described herein are for illustrative purposes and are not limiting. Other exemplary embodiments may be made and modifications made within the spirit and scope of the disclosure. Therefore, the detailed description is not intended to limit the disclosure. The scope of the invention (i) is defined only by the following claims and equivalents thereof.

Embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure 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; an optical storage medium; a flash memory device; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, data signals, etc.), and others. Further, firmware, software, procedures, instructions may be described herein as performing some action. However, it is to 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, processes, instructions, etc.

The following detailed description of exemplary embodiments will so fully reveal the general nature of the disclosure that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such as the exemplary embodiments, without undue experimentation, without departing from the spirit and scope of the present disclosure. Accordingly, such adaptations and modifications are intended to be within the meaning of exemplary embodiments based on the teachings and guidance included herein, and their various equivalents. 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 with the benefit of the teachings herein.

For the purposes of such discussion, the term "module" will be understood to include at least one of software, firmware, and hardware (such as one or more circuits, microchips, or devices, or any combination thereof), and any combination thereof. Further, it should be understood that each module may include one, or more than one, component of an actual device, and each component forming a portion of the module may cooperate or work independently with any other component forming a portion of the module. Rather, the modules described herein may represent a single component in an actual device. Further, the components in the module may be a single component or dispersed among multiple devices in a wired or wireless manner.

Although, the present disclosure will be described in terms of NFC, those skilled in the art will recognize that the present disclosure 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 disclosure. For example, although the present disclosure will be described using NFC-enabled communication devices, those skilled in the art will recognize that the functionality of these NFC-enabled communication devices may be applied to other communication devices using near and/or far fields without departing from the spirit and scope of the present disclosure.

An exemplary Near Field Communication (NFC) implementation

Fig. 1 shows a block diagram of an NFC environment according to an exemplary embodiment of the present disclosure. 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 that are sufficiently close to each other. It will be apparent to those skilled in the art that 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 other electronic devices or host devices, such as mobile phones, portable computer devices, other computing devices such as personal computers, laptop computers, or desktop computers, computer peripherals such as printers, portable audio and/or video players, payment systems, ticket writing systems such as, for example, parking tickets, bus ticket counting systems, train ticket counting systems, or entry ticket counting systems, or ticket reading systems, toys, games, posters, packaging, advertising material, product inventory checking systems, and/or any other suitable electronic device without departing from the spirit and scope of the present disclosure.

The first NFC device 102 detects the presence of the second NFC device 104 so that information between the first NFC device 102 and the second NFC device 104 can be communicated. Generally, the first NFC device 102 observes the presence of the second NFC device 104 in its magnetic field. The first NFC device 102 observes its magnetic field to determine if a second NFC device 104 is present within its environment. Upon detecting the presence of the second NFC-enabled device 104 in its environment, the first NFC-enabled device 102 may enter a polling mode (such as a conventional polling mode of operation 208 or other suitable polling mode as would be apparent to one of ordinary skill in the relevant art without departing from the spirit and scope of the present disclosure) to establish communication with the second NFC-enabled device.

Traditional detection mode of operation

Typically, a first conventional NFC device operates in a conventional detection mode of operation to detect the presence of a second conventional NFC device. When a second legacy NFC device is detected, the first legacy NFC enters a legacy polling mode of operation to establish communication with 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 having substantially similar amplitudes until a change in amplitude of one of the conventional detection pulses is detected. The change in amplitude indicates that the second conventional NFC device has entered a magnetic field provided by the first conventional NFC device. When a second legacy NFC device is detected, the first legacy NFC enters a legacy polling mode of operation to establish communication with the second legacy NFC device.

As shown in diagram 202, the first conventional NFC device provides one or more conventional detection pulses 206.1 through 206.N, each of the conventional detection pulses 206.1 through 206.N characterized by substantially similar amplitudes. For example, the amplitude of the conventional detection pulse 206.1 is substantially similar to the conventional detection pulse 206.2, and the amplitude of the conventional detection pulse 206.2 is substantially similar to the conventional detection pulse 206. N. As also shown in diagram 202, the first conventional NFC device enters a conventional polling mode of operation 208 after a conventional detection pulse 206.N to establish communication with the second conventional NFC device. "NFC forum published on 11/18/2010: description of NFC actions: technical description, NFC Forum^TMAction 1.0NFC Forum TS action 1.0 "(" NFCForum: NFCActivitySpecification: technical Specification, NFCForum)^TMActivity1.0nfcforum-TS-Activity-1.0, ") an example of a traditional polling mode of operation 208 is described, which is incorporated herein by reference for all purposes without loss of its integrity.

As shown in diagram 204, the first conventional NFC device observes one or more conventional detection pulses 206.1 through 206.N, referred to as one or more observed detection pulses 210.1 through 210. N. One or more observed detected pulses 210.1 through 210. (N-1) are characterized by substantially similar amplitudes. The substantially similar amplitudes of the one or more observed detected pulses 210.1 through 210 (N-1) indicate that a second conventional NFC device is not present in the magnetic field. As also shown in diagram 204, the amplitude of observed detected pulse 210.N is not substantially similar to the amplitude of observed detected pulse 210. (N-1). This difference in amplitude indicates that the second conventional NFC device has entered the magnetic field during the conventional detection pulse 206. N. Thus, the first conventional NFC device may enter the conventional polling mode of operation 208 to establish communication with the second conventional NFC device. The first legacy NFC device continues to observe the legacy polling mode of operation 208 (the legacy polling mode of operation 208 is referred to as the observed polling mode of operation 212) to verify that the second legacy NFC device is still present in the magnetic field. In U.S. patent application No. filed 4 month 22, 2009, under 35u.s.c. § 371 (c): 12/446,591, the conventional detection mode of operation is further described.

However, such simple detection of a change to the conventional detection mode is susceptible to environmental changes. For example, moving the first legacy NFC device in the environment may cause the amplitude of one or more legacy detection pulses 206.1 through 206.N to change. As another example, an object in the environment of an incoming magnetic field, such as a metal object or other non-NFC-enabled device, for example, may cause one or more of the conventional detection pulses 206.1 through 206.N to change in amplitude. However, these changes are caused by these environments, not by the second conventional NFC that is entering a magnetic field. Thus, in the absence of the second conventional NFC device in the magnetic field, the first conventional NFC device may incorrectly determine that the second conventional device is present in the magnetic field and enter the conventional polling mode of operation 208.

Exemplary detection mode of operation

The present disclosure generates a variety of magnetic fields to detect NFC-enabled devices or other objects in its environment. As discussed in fig. 3A-3B, the present disclosure may use a variable frequency magnetic field to detect NFC-enabled devices or other objects within an environment. As discussed in fig. 4A-4B, the present disclosure may use a carrier frequency constant magnetic field to detect NFC-enabled devices or other objects within an environment. The present disclosure measures a variable frequency magnetic field and/or a carrier frequency constant magnetic field to detect NFC-enabled devices or other objects within its environment.

Variable frequency magnetic field

Fig. 3A graphically illustrates a first frequency detection sequence that may be used by a first NFC-enabled device to detect the presence of a second NFC-enabled device according to an example embodiment of the present disclosure. Generally, a first NFC-enabled device (such as, for example, the first NFC device 102) is configured to operate in an initiator, or reader, mode of operation, and a second NFC-enabled device (such as, for example, the second NFC device 104) is configured to operate in a target, or tag, mode of operation.

The first NFC-enabled device may generate a variable frequency magnetic field using the detection sequence 300 to continuously probe the environment at multiple frequencies to detect the presence of the second NFC-enabled device as well as other objects and/or other non-NFC-enabled devices. In particular, the first NFC device applies the detection signals 302.1 to 302.N to its inductive coupling elements in a sequential or near sequential manner to generate a variable frequency magnetic field. Generally, a first NFC device applies a frequency converted carrier to its inductive coupling element for different times to generate a frequency converted magnetic field. For example, the first NFC-device application comprises having a first frequency f₁To its inductive coupling element for a first time period τ₁A first magnetic field is generated. Next, the first NFC-enabled device applies the second frequency f₂To its inductive coupling element for a second time period τ₂A second magnetic field is generated. The first NFC-device continues in a substantially similar manner until all of the detection signals 302.1 through 302.N in the detection sequence 300 are applied to its inductive coupling element to generate a variable frequency magnetic field.

The detection signals 302.1 to 302.N may be characterized by a duration τ₁To tau_NFrequency f₁To f_NOr pulse train of energy. Uniformly, frequency f₁To f_NRepresents any series or sequence of frequencies that may be used to perform a sequential or near sequential frequency sweep over a varying magnetic frequency field over a range of frequencies, such as from about 12.0 to about 14.5MHz or from about 11.0 to about 15.0MHz, for example. Duration tau₁To tau_NRepresenting when a second NFC capable device is presentIt may be a sufficient period of time to cause a perturbation in the variable frequency magnetic field. In general, these disturbances may be caused by a second NFC device harvesting or drawing power from the variable frequency magnetic field when present. In addition, duration τ₁To tau_NThere may be a sufficient period of time for the first NFC-enabled device to detect a perturbation in the variable frequency magnetic field that may indicate the presence or absence of the second NFC-enabled device.

Fig. 3B graphically illustrates a frequency domain characterization of a first frequency detection sequence, according to an example embodiment of the present disclosure. The detection sequence 304 may be used to detect a sequence at F₁Sequentially probing the environment to detect the presence of a second NFC-enabled device, and other objects and/or other non-NFC-enabled devices within the environment to F3. Detection sequence 304 includes detection signals 306.1 through 306.3. This is for purposes of example only and those skilled in the art will recognize that detection signals 306.1 through 306.3 may include any suitable number of detection signals to perform a sequential, or nearly sequential, frequency sweep over a frequency-varying magnetic field in a frequency range to detect the presence of a second NFC-enabled device and other objects and/or other non-NFC-enabled devices without departing from the spirit and scope of the present disclosure. The test sequence 304 may represent an example frequency domain characterization of the test sequence 300.

The first NFC-enabled device uses the detection sequence 304 to perform a sequential, or near sequential, frequency sweep over the frequency-varying magnetic field in a frequency range to detect the presence of the second NFC-enabled device as well as other objects and/or other non-NFC-enabled devices. The first NFC-enabled device may apply a detection signal 306.1 to its inductive coupling element to generate a signal having a first frequency F₁Of the first magnetic field. Thereafter, the first NFC-enabled device may apply the detection signal 306.2 to its inductive coupling element to generate the signal having the second frequency F₂Of the second magnetic field. Next, the first NFC device may apply the detection signal 306.3 to its inductive coupling element to generate a signal having a third frequency F₃The third magnetic field of (2). Collectively, the first to third magnetic fields are referred to as variable frequency magnetic fields.

Carrier frequency constant magnetic field

Fig. 4A graphically illustrates a second frequency detection sequence that may be used by a first NFC-enabled device to detect a second NFC-enabled device, in accordance with an exemplary embodiment of the present disclosure. The first NFC-enabled device may use the detection sequence 400 to generate a carrier frequency constant magnetic field to probe the environment at multiple frequencies simultaneously to detect the presence of the second NFC-enabled device, as well as other objects and/or other non-NFC-enabled devices. In particular, the first NFC-enabled device applies a detection signal 402.1 to its inductive coupling element to generate a carrier frequency constant magnetic field. Optionally, the first NFC-enabled device may apply one or more detection signals 402.1 to 402.n to its inductive coupling element in a sequential or near sequential manner to generate a carrier frequency constant magnetic field. The first NFC device modulates one or more cycles of an electrical signal (such as, for example, a square pulse 404) with a carrier 406 having a frequency f to generate detection signals 402.1 to 402. n. Thereafter, the first NFC-enabled device applies the detection signals 402.1 to 402.n to its inductive coupling element to generate a carrier frequency constant magnetic field. Modulation of the electrical signal with carrier wave 406 may cause frequencies or groups of frequencies, generally referred to as sidebands, containing energy less than and/or greater than frequency f to be present within detection sequence 400.

Fig. 4B graphically illustrates a characterization of the frequency domain of the second frequency detection sequence according to an exemplary embodiment of the present disclosure. The detection sequence 406 may be used to simultaneously probe the environment at multiple frequencies using a carrier frequency constant magnetic field to detect the presence of a second NFC-enabled device, and other objects and/or non-NFC-enabled devices within the environment. The test sequence 406 may represent an exemplary frequency domain representation of the test sequence 400.

As shown in fig. 4B, a modulated rectangular pulse is generated by modulating, for example, a rectangular pulse, such as rectangular pulse 404, with, for example, a carrier, such as carrier 606. The modulated square pulses may be formed with a frequency F₁Has a frequency F and a spectral component 408 having a frequency F_s，1To F_s,nAre shown as spectral components 410.1 through 410. n. The spectral components 410.1 through 410.n shown in fig. 4B are for exemplary purposes only, and those skilled in the art will recognize that other spectral components are possible without departing from the spirit and scope of the present disclosure. The detection sequence 406 may be used to simultaneously detect at frequency F₁And frequency F_s，1To F_s,nThe environment is probed to detect the presence of a second NFC-enabled device and other objects and/or non-NFC-enabled devices within the environment.

The spectral components 410.1 to 410.n may be selectively determined by adjusting certain characteristics of the rectangular wave. For example, the duty cycle of the rectangular pulse, i.e., the ratio between the duration and the period of the rectangular pulse, may be selectively selected to determine the frequency separation of the spectral components 410.1 through 410. n. A large duty cycle generally has less frequency separation at frequencies between spectral components 410.1 to 410.n than a smaller duty cycle. In an exemplary embodiment, the square pulse 404 generally has a one-third duty cycle.

As another example, the shape of the rectangular pulse may be selected to substantially attenuate the frequency F_s，1To F_s,nA plurality of frequencies. The rectangular pulse may be selected to characterize an even function to attenuate the odd spectral components of the rectangular pulse. The rectangular pulse may be selected to characterize an odd function to attenuate even spectral components of the rectangular pulse. In the exemplary embodiment of detection sequence 406 shown in fig. 4B, rectangular pulse 404 characterizes an odd function whose even spectral components from between spectra 410.1 through 410.n are attenuated.

Using variable frequency magnetic fields and/or carrier frequency constant magnetic fields in an exemplary detection mode of operation

Fig. 5 is a flowchart of exemplary operational steps for detecting the presence of a NFC capable device within an environment, according to an exemplary embodiment of the present disclosure. The present disclosure is not limited to this working description. Rather, it will be apparent to those skilled in the art from the teachings herein that other work control flows are within the scope and spirit of the present disclosure. The following discussion describes the steps in fig. 5.

At step 502, the workflow polls the environment for the presence of NFC capable devices. The workflow polls the environment for one of the multiple technology capable NFC capable devices. It will be apparent to those skilled in the art that the various possible technology types may include type a NFC capable devices, type B NFC capable devices, type F NFC capable devices, or any other type of NFC capable devices without departing from the spirit and scope of the present disclosure. The workflow polls the environment for type a NFC capable devices with a type a request command (REQA), polls the environment for type B NFC capable devices with a type B request command (REQB), polls the environment for type F NFC capable devices with a type F request command, or polls any other type of NFC capable devices with any suitable request command as will be apparent to those skilled in the art without departing from the spirit and scope of the disclosure.

At step 504, the workflow determines whether a NFC capable device is present within the environment. The workflow listens for a response from the NFC-enabled device to the request command of the polling procedure of step 502. When the workflow receives a response, then the NFC device may be present within the environment. In this case, the work control flow proceeds to step 506. Otherwise the workflow does not receive a response. In this case, the technical-type NFC device polled at step 502 does not exist within the environment. The flow of work control proceeds to step 508.

At step 506, the workflow proceeds to communicate with NFC-enabled devices present in the environment.

At step 508, the workflow determines whether the environment has been polled for all of the multiple technology-capable NFC devices. If not, the workflow returns to step 502 to poll the environment for another one of the plurality of technically capable NFC devices. Otherwise, no NFC-enabled device exists in the environment. In this case, the workflow proceeds to step 508 to begin the detection procedure to detect the presence of a NFC capable device.

At step 510, the workflow generates a magnetic field to detect the presence of the NFC capable device using, for example, a detection sequence such as detection sequence 300, detection sequence 304, detection sequence 400, and/or detection sequence 406. The workflow may use, for example, an unmodulated variable frequency detection sequence, such as detection sequence 300 and/or detection sequence 304, to generate a variable frequency magnetic field to perform a sequential, or near sequential, frequency sweep within a frequency range to detect the presence of NFC-enabled devices and other objects and/or other non-NFC-enabled devices in the environment. Alternatively, the workflow may use modulated varying frequency detection sequences, such as detection sequence 400 and/or detection sequence 404, for example, to generate a carrier frequency constant magnetic field to probe the environment at multiple frequencies simultaneously to detect the presence of NFC capable devices and other objects and/or other non-NFC capable devices in the environment. As another alternative, the workflow may use any combination of unmodulated variable frequency detection sequences and modulated constant frequency detection sequences to detect the presence of NFC capable devices as well as other objects and/or other non-NFC capable devices in the environment.

At step 512, the workflow determines whether a NFC device is present in the environment. Specifically, the work control process samples a variable frequency magnetic field and/or a carrier frequency constant magnetic field. The workflow compares one or more samples of the variable frequency magnetic field and/or the carrier frequency constant magnetic field with one or more samples of a priori known responses of a plurality of objects present in the environment (examples of these samples are discussed in fig. 6A and 6B). For example, the various objects may include, for example, NFC-enabled devices such as type a NFC-enabled devices, type B NFC-enabled devices, type F NFC-enabled devices, or any other type of NFC-enabled devices, and/or other objects such as, for example, metal objects, or other non-NFC-enabled devices. The workflow uses the object to determine whether a NFC capable device, or other object and/or other non-NFC capable device, is within the environment. If an NFC capable device is present in the environment, the workflow returns to step 502 to poll the environment for NFC capable devices. Otherwise, the NFC-enabled device is not present in the environment. In this case, the workflow returns to step 510 to generate another magnetic field to detect the presence of the NFC-enabled device using another detection sequence.

A priori known responses of multiple objects to variable frequency magnetic fields

Fig. 6A illustrates a plurality of a priori known responses of various objects to a variable frequency magnetic field according to an exemplary embodiment of the present disclosure. A number of a priori known responses to the free space 652, the small metal object 654, the large metal object 656, the second NFC-enabled device 658, and the second NFC-enabled device 660 are shown in fig. 6A. The multiple a priori known responses to the multiple subjects are for purposes of example only, and those skilled in the art will recognize that other a priori known responses to the multiple subjects and/or other a priori known responses to other subjects described in fig. 6A are possible without departing from the spirit and scope of the present disclosure.

The free space 652 represents an a priori known response of, for example, an NFC-enabled device such as the first NFC-enabled device 102 when no object is located within the variable frequency magnetic field. Typically, the peak response of the first NFC-enabled device occurs at approximately 13MHz when no object is located within the magnetic field.

The small metal object 654 represents an a priori known response of the NFC-enabled device when, for example, a small metal object such as a metal key ring is located within the variable frequency magnetic field. The a priori known response to an NFC-enabled device of a small metal object 654 is generally characterized as having its peak response at a frequency that approximates the peak response frequency of the free space 652; however, the response is attenuated compared to the free space 652.

The large metal object 656 represents the a priori known response of an NFC-enabled device when, for example, a large metal object such as a metal disk is located within the variable frequency magnetic field. The a priori known response of the NFC-enabled device to the large metal object 656 is generally characterized by having its peak response at a frequency different from the peak response frequency of the free space 652 and/or being attenuated compared to the free space 652 when the large metal object 656 is located within the variable frequency magnetic field.

The second NFC device 658 represents an a priori known response of the NFC device when the second NFC device is located within the variable frequency magnetic field operating according to type a technology, type B technology, or any other similar technology that would be apparent to one skilled in the art without departing from the technology and scope of the present disclosure. The a priori known response to the second NFC-enabled device 658 of the second NFC-enabled device is generally characterized by having its peak response at a frequency different from the peak response frequency of the free space 652 and/or being attenuated compared to the free space 652.

The second NFC-enabled device 660 represents an a priori known response of the NFC-enabled device when the second NFC-enabled device operating according to type F (FeliCa) technology, or any other similar technology apparent to those skilled in the art, is located within the variable frequency magnetic field without departing from the technology and scope of the present disclosure. In general, the second NFC device elicits a distinctive response when it is tuned to approach a frequency, or range of frequencies, corresponding to the peak response of the first NFC device. In such an example, the second NFC-enabled device 660 is characterized as being over-coupled, which reduces current flow in the first NFC-enabled device at the frequency, or range of frequencies. The a priori known response for the NFC-enabled device of the second NFC-enabled device 660 is generally characterized by having its peak response at a frequency different from the peak response frequency of the free space 652 and/or the response is attenuated compared to the free space 652.

A priori known responses of various objects to a carrier frequency constant magnetic field

Fig. 6B illustrates a plurality of a priori known responses of various objects to a carrier frequency constant magnetic field according to an exemplary embodiment of the present disclosure. A number of a priori known responses to free space 672, small metal object 674, large metal object 676, second NFC-enabled device 678, and second NFC-enabled device 680 are shown in fig. 6B. The multiple a priori known responses to the multiple subjects are for purposes of example only, and those skilled in the art will recognize that other a priori known responses to the multiple subjects described in fig. 6B and/or other a priori known responses to other subjects are possible without departing from the spirit and scope of the present disclosure.

The free space 672 represents an a priori known response of, for example, an NFC-enabled device such as the first NFC-enabled device 102 when no object is located within the carrier frequency constant magnetic field. Typically, the peak response of the first NFC-enabled device occurs at approximately 16.56MHz when no object is located within the magnetic field. However, this example is not limiting and it will be apparent to those skilled in the art that other frequencies are possible without departing from the spirit and scope of the disclosure.

The small metallic object 674 represents an a priori known response of the NFC-enabled device when, for example, a small metallic object such as a metallic key-ring is located within a carrier frequency constant magnetic field. The a priori known response to an NFC-enabled device of small metal object 674 is generally characterized as having its peak response at a frequency that approximates the peak response frequency of free space 672; however, the response is attenuated compared to the free space 652.

The large metal object 676 represents an a priori known response of the NFC-enabled device when, for example, a large metal object such as a metal disk is located within a carrier frequency constant magnetic field. The a priori known response of the NFC capable device to the large metal object 676 is generally characterized by having its peak response at a frequency different from the peak response frequency of the free space 672 and/or being attenuated compared to the free space 672 when the large metal object 676 is within the carrier frequency constant magnetic field.

The second NFC-enabled device 678 represents the a priori known response of the NFC-enabled device when the second NFC-enabled device operating according to type a technology, type B technology, or any other similar technology that will be apparent to those skilled in the art is located within a carrier frequency constant magnetic field without departing from the technology and scope of the present disclosure. The a priori known response of the second NFC-enabled device 678 to the second NFC-enabled device is generally characterized by having its peak response at a different frequency than the peak response frequency of the free space 672 and/or the response is attenuated compared to the free space 672.

The second NFC device 680 represents an a priori known response of the NFC capable device when the second NFC capable device operating in accordance with type F (FeliCa) technology, or any other similar technology apparent to those skilled in the art, is located within a carrier frequency constant magnetic field without departing from the technology and scope of the present disclosure. The a priori known response to the NFC-enabled device of the second NFC-enabled device 680 is generally characterized by having its peak response at a frequency different from the peak response frequency of the free space 672 and/or the response is attenuated compared to the free space 672.

Determining whether or not an NFC-enabled device is present in an exemplary detection mode of operation

In general, a first NFC-enabled device, such as, for example, first NFC-enabled device 102, samples a variable frequency magnetic field generated in response to, for example, a variable frequency detection sequence, such as detection sequence 300 and/or detection sequence 304, and/or a carrier frequency constant magnetic field generated in response to, for example, a frequency constant detection sequence, such as detection sequence 400 and/or detection sequence 406. The first NFC-enabled device compares, in the time or frequency domain, samples of the variable frequency magnetic field and/or the carrier frequency constant magnetic field with corresponding samples of a plurality of a priori known responses from a variety of objects to detect the presence of, for example, a second NFC-enabled device, such as the second NFC-enabled device 104, and other objects and/or other non-NFC-enabled devices within the environment. In general, the first NFC device determines that one of the plurality of objects is present when an a priori known response corresponding to the one of the plurality of objects substantially matches a sample of the variable frequency magnetic field and/or the carrier frequency constant magnetic field. The a priori known response of the object may be approximately equal to and/or differ from the sample of the variable frequency magnetic field and/or the carrier frequency constant magnetic field by a threshold amount deemed to substantially match.

Fig. 7 is a second flowchart of exemplary operational steps for detecting the presence of a NFC-enabled device within an environment, according to an exemplary embodiment of the present disclosure. The second flowchart shown in fig. 7 further illustrates an exemplary implementation of step 512 discussed in fig. 5. The present disclosure is not limited to this working description. Rather, it will be apparent to those skilled in the art from the teachings herein that other work control flows are within the scope and spirit of the present disclosure. The following discussion describes the steps in fig. 7.

At step 702, the workflow samples a magnetic field generated by, for example, a detection sequence, such as detection sequence 300, detection sequence 304, detection sequence 400, and/or detection sequence 406. The workflow may provide one or more samples of a variable frequency magnetic field generated in response to an unmodulated variable frequency detection sequence (e.g., such as detection sequence 300, and/or detection sequence 304), and/or a carrier frequency constant magnetic field generated in response to a modulated frequency constant detection sequence (e.g., such as detection sequence 400 and/or detection sequence 406). The workflow may selectively perform a Fast Fourier Transform (FFT) and/or a Discrete Fourier Transform (DFT) on the one or more samples to transform the one or more samples from a time domain representation to a frequency domain representation.

At step 704, the workflow determines whether the one or more samples from step 702 substantially match one or more samples corresponding to a priori known responses of objects that may be present within the environment. In general, the a priori known responses of step 704 represent a priori known response selected from a plurality of a priori known responses corresponding to a plurality of objects that may be present in the environment. Specifically, the workflow determines whether the one or more amplitudes of the one or more samples from step 702 substantially match the one or more amplitudes of the one or more samples of the a priori known response at the one or more frequencies in the time domain or the frequency domain. When the one or more samples from step 702 are approximately equal to the one or more samples and/or differ by a threshold amount, the one or more samples from step 702 substantially match the one or more samples of the a priori known response. Optionally, the workflow may further process the one or more samples at step 702 prior to the comparison. For example, the workflow may determine the maximum amplitude and/or its associated frequency of the one or more samples from step 702 and determine whether the maximum amplitude and/or its associated frequency amplitude substantially matches the frequency and/or maximum amplitude of the a priori known response. When the one or more samples from step 702 substantially match the one or more samples of the a priori known response, the workflow proceeds to step 706. Otherwise, when the one or more samples from step 702 do not substantially match the one or more samples of the a priori known responses, the workflow proceeds to step 712.

At step 706, the workflow identifies objects present within the environment that have a priori known responses that substantially match the one or more samples from step 702. The substantially matching a priori known response may correspond to the absence of an object (such as free space) within the environment, the presence of another NFC-enabled device in the environment, or the presence of other objects such as metallic objects in the environment. When the workflow identifies an object present in the environment as a NFC capable device, the workflow proceeds to step 708. Otherwise, when there is no NFC capable device in the environment, the flow of work control proceeds to step 710.

At step 708, the workflow determines that a NFC device may be present in the environment. The workflow may selectively identify technology types of NFC-enabled devices present in the environment. It should be noted that when it is determined that a NFC capable device is present in the environment, as discussed in fig. 5, the workflow may poll for technology types of NFC capable devices, or alternatively, all technology types. Further, the order in which the polling is performed may be determined as the technique that first polls the response having an a priori knowledge that best matches the maximum amplitude of the sample and/or its associated frequency.

At step 710, the workflow determines that there are no NFC-enabled devices in the environment. The workflow may selectively identify objects present in the environment as non-NFC capable devices, other objects such as metallic objects, or no objects at all.

At step 712, the workflow selects other a priori known responses for other objects present in the environment. The workflow returns to step 704 to select another a priori known response from the other plurality of a priori known responses that corresponds to another object that may be present in the environment. The workflow repeats steps 704 and 712 until an object is detected in the environment, or all of a plurality of a priori known responses have been compared, at which point the workflow returns to step 702.

First exemplary NFC device

Fig. 8 illustrates a block diagram of an NFC capable device that may be used to detect the presence of other NFC capable devices according to an example embodiment of the present disclosure. The NFC device 800 may be configured to operate in a detection mode of operation to detect the presence of another NFC device in its environment. It should be noted that fig. 8 only illustrates a detection mode of operation, and those skilled in the art will recognize that the NFC device 800 may be configured to operate in other modes of operation, such as a peer-to-peer (P2P) communication mode or a reader/writer (R/W) communication mode, for example, without departing from the spirit and scope of the present disclosure. NFC device 800 includes a controller module 802, a modulator module 804, an antenna module 806, and a demodulator module 808. The NFC device 800 may represent an exemplary embodiment of the first NFC device 102.

The controller module 802 controls all operations and/or configurations of the NFC device 800. Controller module 802 generates a detection sequence 852, such as, for example, an envelope of detection sequence 300, detection sequence 304, detection sequence 400, and/or detection sequence 406, in a detection mode of operation.

The controller module 802 may generate a detection sequence 852 in response to the command. Commands may be provided to the controller module 802 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, any machine-readable medium apparent to those skilled in the art without departing from the spirit and scope of the present disclosure, or any combination thereof. Other machine-readable media may include, but are not limited to: read-only memory (ROM), Random Access Memory (RAM), magnetic disk storage media; an optical storage medium; a flash memory device; electrical, optical, acoustical or other form of propagated signals (e.g., such as carrier waves, infrared signals, data signals, etc.), and others. The controller module 802 may also receive commands from, for example, a user interface such as a touch screen display, alphanumeric keypad, microphone, mouse, speaker, any other suitable user interface as would be apparent to one of ordinary skill in the art without departing from the spirit and scope of the present disclosure. The controller module 802 may further receive commands from other electrical devices or host devices coupled to the NFC device 800.

Modulator module 804 modulates detection sequence 852 onto a carrier wave using any suitable analog or digital modulation technique to provide modulated detection sequence 854. 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 monitoring (ASK), Quadrature Amplitude Modulation (QAM), and/or any other suitable modulation technique apparent to those skilled in the art. Detection sequence 852 can represent, for example, an unmodulated variable frequency detection sequence, such as detection sequence 300, and/or detection sequence 304, and/or a modulated constant frequency detection sequence, such as detection sequence 400.

Antenna module 806 applies modulated detection sequence 854 to, for example, an inductive coupling element such as a resonant tuned circuit to generate a frequency-converted magnetic field and/or a carrier frequency constant magnetic field to provide detection sequence 856. Antenna module 806 observes detection sequence 856 to provide observed detection sequence 858.

Demodulator module 808 demodulates observed detected sequence 858 using any suitable analog or digital modulation technique to provide a reconstructed detected signal 860. 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 monitoring (ASK), Quadrature Amplitude Modulation (QAM), and/or any other suitable modulation technique apparent to those skilled in the art.

The controller module 802 samples the reconstructed detection signal 860 to detect the presence of, for example, a second NFC-enabled device, such as the second NFC-enabled device 104, and other objects and/or other non-NFC-enabled devices in the environment. The controller module 802 compares the samples of the reconstructed detection signal 860 with corresponding samples of a variety of a priori known responses from a variety of objects in the time and/or frequency domain to detect the presence of a second NFC-enabled device, and other objects and/or other non-NFC-enabled devices in the environment. In general, the controller module 802 determines that one of the plurality of objects is present when the a priori known response corresponding to the one of the plurality of objects substantially matches the samples of the reconstructed detection signal 860. Optionally, the control module 802 may perform a Fast Fourier Transform (FFT) and/or a Discrete Fourier Transform (DFT) on one or more samples of the reconstructed detected signal 860 to transform the one or more samples from a time-domain representation to a frequency-domain representation.

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 section may describe one or more, but not all exemplary embodiments of the disclosure, and thus, should not be used to limit the disclosure and the appended claims in any way.

The present disclosure 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 set for the convenience of the description. Different boundaries may be defined so long as the specified functions and relationships are properly 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 disclosure. Thus, the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the claims of the present application and their equivalents.

Claims (8)

1. A method for detecting the presence of a first near field communicable device, comprising:

(a) generating, by the second near field communicable device, a variable frequency magnetic field to detect a presence of the first near field communicable device;

(b) comparing the variable frequency magnetic field to an a priori known response of the first near field communicator to the variable frequency magnetic field; and

(c) when the variable frequency magnetic field matches the a priori known response, determining that the first near field communicable device is present in the environment of the second near field communicable device.

2. The method of claim 1, wherein step (a) comprises:

(a) (i) applying a plurality of detection signals to an inductive coupling element to generate the variable frequency magnetic field, each of the plurality of detection signals characterized by a different one of a plurality of frequencies.

3. The method of claim 2, wherein step (a) (i) comprises:

(a) (i) (1) applying a first detection signal of the plurality of detection signals including a first carrier wave having a first frequency of the plurality of frequencies over a first time period to generate a first magnetic field; and

(a) (i) (2) applying a second detection signal of the plurality of detection signals including a second carrier wave having a second frequency of the plurality of frequencies over a second time period to generate a second magnetic field,

wherein the variable frequency magnetic field comprises the first magnetic field and the second magnetic field.

4. A method for detecting the presence of a first near field communicable device, comprising:

(a) generating, by a second near-field communicable device, a carrier frequency constant magnetic field to detect a presence of the first near-field communicable device;

(b) comparing the carrier frequency constant magnetic field with a priori known responses of the first near field communicable device to the carrier frequency constant magnetic field; and

(c) determining that the first near-field communicable device is present in the environment of the second near-field communicable device when the carrier frequency constant magnetic field matches the a priori known response.

5. A first near field communicable device, comprising:

a demodulator module configured to reconstruct a detection sequence from a frequency-varying magnetic field configured to detect a presence of a second near-field communicable apparatus; and

a controller module configured to compare the variable frequency magnetic field with an a priori known response of the second near-field communicable apparatus to the variable frequency magnetic field and determine that the second near-field communicable apparatus is present in the environment of the first near-field communicable apparatus when the variable frequency magnetic field matches the a priori known response.

6. The first near field communicable device of claim 5, further comprising:

an antenna module configured to apply a plurality of detection signals to an inductive coupling element to generate the variable frequency magnetic field, each of the plurality of detection signals characterized by a different one of a plurality of frequencies.

7. The first near-field communicable device of claim 6, wherein the antenna module is further configured to apply a first detection signal of the plurality of detection signals including a first carrier wave having a first frequency of the plurality of frequencies for a first time period to generate a first magnetic field, and to apply a second detection signal of the plurality of detection signals including a second carrier wave having a second frequency of the plurality of frequencies for a second time period to generate a second magnetic field, wherein the variable frequency magnetic field includes the first magnetic field and the second magnetic field.

8. A first near field communicable device, comprising:

a demodulator module configured to reconstruct a detection sequence from a carrier frequency constant magnetic field configured to detect the presence of a second near field communicable device; and

a controller module configured to compare the carrier frequency constant magnetic field with an a priori known response of the second near-field communicable apparatus to the carrier frequency constant magnetic field and determine that the second near-field communicable apparatus is present in the environment of the first near-field communicable apparatus when the carrier frequency constant magnetic field matches the a priori known response.