The described embodiments relate generally to devices that communicate via inductive coupling and related methods, and more particularly to devices that communicate via inductive coupling to detect an external tag (or card) device and related methods.
A NFC (Near Field Communication) enabled device is an example of a communications device that communicates via inductive coupling. NFC is a short-range wireless technology that allows communication between NFC enabled objects over a distance of less than 10 cm. NFC is based on Radio Frequency Identification (RFID) standards. It is a technology that is designed to make an easier and more convenient world for us, enhancing the way we make transactions, exchange content and connect devices. The NFC tags one might see or create include contacts, URLs, map locations, text and much more.
For RF (radio frequency) reader/tag systems (such as a NFC/RFID (near field communication/radio frequency identification) reader system described above), it is an important feature for a reader device to be able to detect a target device (e.g., tag device) within communication distance.
Therefore, there are strong motivations to provide enhanced methods and devices for detecting an external tag (or card) device.
This specification discloses methods and devices for NFC/RFID (near field communication/radio frequency identification) reader systems to detect an external target device (e.g., tag or card device) within communication distance. In some embodiments, this is achieved by: (i) directing a Tx (transmitter) unit to generate a Tx signal, (ii) sweeping through a first Tx output (e.g., Tx voltage) in an increasing manner, and then (iii) monitoring a second Tx output (e.g., Tx current). During monitoring, a step change in the second Tx output (e.g., Tx current) would indicate detection of an external target device.
The present invention provides for a method for operating a device that communicates via inductive coupling to detect an external tag device, the method comprising: (a) generating, by a Tx (transmitter) unit of the device, a transmitted signal, wherein a Tx (transmitter) control unit of the device is configured for controlling the Tx (transmitter) unit of the device; (b) sweeping through, by the Tx (transmitter) control unit of the device, a first output of the transmitted signal; (c) monitoring, by the device, a second output of the transmitted signal, wherein a change in the second output of the transmitted signal indicates detection of the external tag device.
In some embodiments, the method further comprising: (d) determining a minimum power needed for communication between the device and the external tag device.
In some embodiments, sweeping through the first output of the transmitted signal comprises: increasing or decreasing the first output of the transmitted signal.
In some embodiments, sweeping through the first output of the transmitted signal comprises: increasing or decreasing the first output of the transmitted signal so that a step change in the second output of the transmitted signal is detected, wherein the step in the second output indicates detection of the external tag device.
In some embodiments, the first output of the transmitted signal comprises one of the following: (i) a voltage of the transmitted signal, (ii) a power of the transmitted signal, (iii) a current of the transmitted signal.
In some embodiments, the second output of the transmitted signal comprises one of the following: (i) a current of the transmitted signal, (ii) a voltage of the transmitted signal, (iii) a power of the transmitted signal, (iv) wherein the second output is not the same as the first output.
In some embodiments, sweeping through the first output of the transmitted signal comprises using one or more of the following output waveforms: (i) a linear slope, (ii) a nonlinear slope, (iii) a staircase, (iv) a pulse mode with increasing or decreasing pulse heights, (v) any other waveform.
In some embodiments, monitoring, by the device, the second output of the transmitted signal, comprises: monitoring, by the Tx (transmitter) control unit of the device, the second output of the transmitted signal.
In some embodiments, the Tx (transmitter) control unit of the device monitors the second output of the transmitted signal based on sensing by one or more of the following: (i) a Tx (transmitter) driver unit of the device, (ii) a Tx (transmitter) supply unit of the device, (iii) a Rx (receiver) unit of the device.
In some embodiments, the Tx (transmitter) control unit of the device monitors the second output of the transmitted signal based on one or more of the following: (i) sensing a current of a Tx (transmitter) driver unit of the device, (ii) sensing a current of a Tx (transmitter) supply unit of the device, (iii) sensing a voltage of a Rx (receiver) unit of the device.
In some embodiments, the external tag device is one of the following: (i) a passive tag, (ii) a card device, (iii) a headset, (iv) a speaker.
In some embodiments, the step of sweeping through the first output of the transmitted signal occurs in a duty-cycled or a pulsed mode, wherein the step of sweeping through is only activated for a portion of a total time and the device is in idle for the remainder of the total time.
In some embodiments, the minimum power is used to determine an effective current and/or power consumption of the external tag device.
In some embodiments, sweeping through the first output of the transmitted signal is fast enough such that impact of changing a distance between the device and the external tag device does not affect accuracy of determining the minimum power needed for communication between the device and the external tag device.
The present invention provides for a computer program product comprising executable instructions encoded in a non-transitory computer readable medium which, when executed by the device, carry out or control the following method for operating a device that communicates via inductive coupling to detect an external tag device, the method comprising: (a) generating, by a Tx (transmitter) unit of the device, a transmitted signal, wherein a Tx (transmitter) control unit of the device is configured for controlling the Tx (transmitter) unit of the device; (b) sweeping through, by the Tx (transmitter) control unit of the device, a first output of the transmitted signal; (c) monitoring, by the device, a second output of the transmitted signal, wherein a change in the second output of the transmitted signal indicates detection of the external tag device.
The present invention provides for a device for detecting an external tag device in communications with the device via inductive coupling, the device comprising: (a) a matching network; (b) an antenna; (c) a Tx (transmitter) unit, the Tx (transmitter) unit configured to generate a transmitted signal that is transmitted through the matching network and the antenna, the Tx (transmitter) unit comprising a Tx (transmitter) control unit, wherein the Tx control unit is configured for controlling the Tx (transmitter) unit, wherein the Tx control unit is further configured for detecting the external tag device by: (i) directing the Tx (transmitter) unit to generate the transmitted signal, (ii) directing the Tx (transmitter) unit to sweep through a first output of the transmitted signal, (iii) monitoring a second output of the transmitted signal, (iv) detecting the external tag device when there is a change in the second output of the transmitted signal.
In some device embodiments, the Tx control unit is further configured for determining a minimum power needed for communication between the device and the external tag device.
In some device embodiments, the first output of the transmitted signal comprises one of the following: (i) a voltage of the transmitted signal, (ii) a power of the transmitted signal, (iii) a current of the transmitted signal.
In some device embodiments, the second output of the transmitted signal comprises one of the following: (i) a current of the transmitted signal, (ii) a voltage of the transmitted signal, (iii) a power of the transmitted signal, (iv) wherein the second output is not the same as the first output.
In some device embodiments, the device further comprising: (d) a receiver unit of the device, wherein the receiver unit of the device is configured to receive a response from the external tag device.
The above summary is not intended to represent every example embodiment within the scope of the current or future Claim sets. Additional example embodiments are discussed within the Figures and Detailed Description below. Other aspects and advantages of embodiments of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.
It will be readily understood that the components of the embodiments as generally described herein and illustrated in the appended figures could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.
Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.
For NFC/RFID (near field communication/radio frequency identification) reader systems, it is a fundamental and crucial feature to be able to detect a target device (e.g., tag device) in communication distance.
An ideal perfect system can identify a target device when in reach and start a communication, while, if the target device is outside reach due to the distance being too far, the communication is abandoned. The challenge is each reader and target (and their combination in a communication) may show individual distance requirements, due to coupling conditions of antenna (geometry), positions (in three-dimensional or x/y/z space), antenna coupling, the matching network, power transfer, etc. The methods and devices described in this specification are targeting to identify exactly at which point the target device is able to respond.
Card-detection or tag-detection is an important feature of NFC/RFID reader systems with the purpose of identifying a target device within communication distance.
In particular,
The communication mechanism of the reader/tag system shown in
As typically target devices (e.g., tags) are passive, the power for operation is being harvested from the reader's CW (continuous wave). In turn, the tag operation is gated by sufficient power transferred from the reader.
Note that the power transfer does depend on distance (in three-dimensional or x/y/z space), antennas geometry and coupling, the matching network design, the power demand of the tag's processing, process variation, etc.
The most dominant factor for being able to communicate between a reader and tag device is power transfer in the direction from reader to tag, and also reader Rx sensitivity in the opposite direction. However, the power transfer is the basis for the response communication path.
As an example, for use case example B, the energy distance is 52 units, while the communication distance is 51 units. This means that for the distance below the communication distance of 51 units (which is shown as a solid white fill), the communication is passing. Then for the distance above the communication distance of 51 units (which is shown with a diagonal hatch pattern), this is a zone of partly failing communication.
As another example, for use case example D, the energy distance is 42 units, while the communication distance is 37 units. This means that for the distance below the communication distance of 37 units (which is shown as a solid white fill), the communication is passing. Then for the distance above the communication distance of 37 units (which is shown with a diagonal hatch pattern), this is a zone of partly failing communication. Then for the distance above the “zone of partly failing communication” (i.e., above the “diagonal hatch pattern” zone), there is full communication fail.
These two examples show that the energy distance and communication distance are strongly dependent on reader and tag device design, and consequently differ for different device types.
As the distance and operation state of the target (e.g., tag) device can be unknown, the maximum output power for test and communication has to be picked (which is according to this example 3.2 W). However, the choice of maximum output power (i.e., 3.2 W) might be a total overkill and waste of energy for a target device A at a distance of, for example, 20 mm, which would easily operate at 0.2 W. This is a power saving of 3.0 W, which is a power saving factor of >90% !
Therefore, in some embodiments, this invention is to detect the presence of a tag, and also the minimum power level at which the tag becomes active. With that knowledge, the power level can be adjusted to what is needed to operate the tag rather than to transmit the maximum possible. This approach even works at far distance when measuring of detuning is hardly possible.
In
In
As described above, one pivotal block here is the Tx (transmitter) control unit 460, which can be implemented in HW (hardware) and/or SW (software) to control the Tx output signal (and power), all configuration of the related blocks (driver, LDO or low-dropout regulator, etc.), and timing.
In some embodiment, the function and procedure of testing can be the following:
a. Enable the Tx driver to emit a field with a specific field-strength.
b. Start monitoring the power emitted by the DUT (e.g., known Tx voltage and measured Tx current). (Note that DUT denotes a device under test.)
c. Change the Tx driver emitted power (e.g., increase the Tx voltage) in a (small) step.
d. Monitor the emitted power again and compare with the previous measured data samples.
e. Note that, at some (increased) Tx power level transmitted from the reader device, the target device (e.g., the tag) will harvest sufficient energy from the field to be able to start-up. Consequently, the target device's impact on the system will be to change from a fully inactive and passive mode to an active state, where energy is drawn.
f. The energy consumed by the target device (e.g., the tag) will show up as an impedance change on the target device side. Furthermore, considering the “law of energy conservation”, the reader device needs to supply the additional energy drawn by the target device.
g. The change of power state for the target device (e.g., the tag) will show up as change in the Tx power emitted by the reader device which is to be detected.
h. Consequently, the Tx power level at which the target device (e.g., the tag) is getting active can be accurately detected.
At time t1, the target device (e.g., the tag) will harvest sufficient energy from the received field at the target device. Having sufficient energy, the tag processing units (analog and digital) will start-up and draw energy/current from the harvester, which in turn extracts the energy from the field.
Initially, up to a specific Tx voltage (and consequently Tx power), the target device (e.g., the tag) is inactive and there is no impact on the communication channel (matching networks, antenna, air channel, etc.). Hence, the impedance seen by the Tx driver is constant.
At time t1, when the target device (e.g., the tag) is starting up, drawing energy from the harvester, the harvester (e.g., a rectifier) loads the communication path (assuming the communication path as a mutual inductance, which is loaded by the active rectifier diode). In the target device (e.g., the tag) inactive case, the rectifier is in a not-conducting switched-off condition, and behaving as a passive part of the circuit.
As soon as the harvester is above the diode voltage levels and the target device (e.g., the tag) becomes active, there is a significant loading that impacts the mutual inductance. Hence, the power out of the Tx will change.
Without the presence of an active target device, the Tx current increase over time is proportionally to the Tx voltage increase. Therefore, initially, up to a specific Tx voltage (and consequently Tx power), the Tx current is increasing over time (in a manner proportionally to the Tx voltage increase), because the target device (e.g., the tag) is inactive and there is no impact on the communication channel (matching networks, antenna, air channel, etc.).
At time t1, when the target device (e.g., the tag) is starting up, drawing energy from the harvester, a huge step increase in the Tx current is seen. Then, as the target device (e.g., the tag) becomes fully active, the current consumption becomes relatively constant, so a steady increase of the Tx current is seen after this initial huge step increase at time t1.
Both
Both
If an increasing Tx voltage sweep (or, in general, an increasing Tx output sweep) is the preferred embodiment, then what are some possible increasing Tx voltage (or output) sweep patterns (or waveforms) that can be used. In that regard,
Again, the common theme for all these example waveforms is that they are all increasing in Tx output. However, the examples from
In some embodiments, the first output of the transmitted signal comprises one of the following: (i) a voltage (i.e., Tx voltage) of the transmitted signal, (ii) a power (i.e., Tx power) of the transmitted signal, (iii) a current (i.e., Tx current) of the transmitted signal. In this specification, most of the examples provided show that the first output of the transmitted signal can be a voltage (i.e., Tx voltage) of the transmitted signal. This is because, in some embodiments, the preferred choice for the first output of the transmitted signal is Tx voltage. However, in some embodiments, the first output of the transmitted signal can also be a power (i.e., Tx power) of the transmitted signal, or a current (i.e., Tx current) of the transmitted signal.
In some embodiments, the second output of the transmitted signal comprises one of the following: (i) a current (i.e., Tx current) of the transmitted signal, (ii) a voltage (i.e., Tx voltage) of the transmitted signal, (iii) a power (i.e., Tx power) of the transmitted signal, (iv) wherein the second output is not the same as the first output. In this specification, most of the examples provided show that the second output of the transmitted signal can be a current (i.e., Tx current) of the transmitted signal. This is because, in some embodiments, the preferred choice for the second output of the transmitted signal is Tx current. However, in some embodiments, the second output of the transmitted signal can also be a voltage (i.e., Tx voltage) of the transmitted signal, or a power (i.e., Tx power) of the transmitted signal, but with the obvious condition that the second output cannot be the same as the first output.
In some embodiments, the device (e.g., reader device) can be monitoring the second output of the transmitted signal. In some embodiments, the Tx (transmitter) control unit of the device can be monitoring the second output of the transmitted signal.
In some embodiments, the Tx (transmitter) control unit of the device can be monitoring the second output of the transmitted signal based on sensing by one or more of the following: (i) a Tx (transmitter) driver unit of the device, (ii) a Tx (transmitter) supply unit of the device, (iii) a Rx (receiver) unit of the device.
In some embodiments, the Tx (transmitter) control unit of the device can be monitoring the second output of the transmitted signal based on one or more of the following: (i) sensing a current of a Tx (transmitter) driver unit of the device, (ii) sensing a current of a Tx (transmitter) supply unit of the device, (iii) sensing a voltage of a Rx (receiver) unit of the device.
In one embodiment, the test sequence for the card-detection might be duty-cycled or a pulsed mode, which means that there is a short period where the system generates a field, sweeps through its field-strength, and checks for a card device to activate, while a portion of the total time, the system is in idle or standby for power saving. As a further example, in some embodiments, the step of sweeping through the first output of the transmitted signal can occur in a duty-cycled or a pulsed mode, wherein the step of sweeping through is only activated for a portion of a total time and the device is in idle for the remainder of the total time.
In one embodiment, this invention may be used to detect the effective current consumption of a card device circuits or its start up. This is because the step change in Tx (transmitter) power can be a measure of the effective current consumption of a card device circuits or its start up. Note that only a measure of the “effective” current consumption of a card device circuits or its start up is possible, because of air channel loss, etc. In some embodiments, the effective current consumption of a card device circuits can be different during “steady state operation” or during “start up”, meaning different power consumptions for the two operating modes.
In one embodiment, the sweep (or change) of the Tx power will be fast such that the impact of changing detuning (i.e., by moving or changing the distance) does not impact the measurement (accuracy). Moreover, the detection criterion is a “step” in the measured power, rather than a continuous increase/decrease caused by changing detuning. As a further example, in some embodiments, sweeping through the first output of the transmitted signal is fast enough such that impact of changing a distance between the device and the external tag device does not affect accuracy of determining the minimum power needed for communication between the device and the external tag device.
In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example embodiments.
Although the operations of the method(s) herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operations may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be implemented in an intermittent and/or alternating manner.
It should also be noted that at least some of the operations for the methods may be implemented using software instructions stored on a computer useable storage medium for execution by a computer. As an example, an embodiment of a computer program product includes a computer useable storage medium to store a computer readable program that, when executed on a computer, causes the computer to perform operations, as described herein.
The computer-useable or computer-readable medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device), or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid-state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disc, and an optical disc. Examples of optical discs include a compact disc with read only memory (CD-ROM), a compact disc with read/write (CD-R/W), a digital video disc (DVD), and a Blu-ray disc.
The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.