CIRCUIT FOR WIRELESS DATA TRANSFER COMPRISING TEMPERATURE REGULATION
A circuit for an NFC chip is described herein. According to one exemplary configuration, the circuit comprises an antenna for near field communication, an antenna resonant circuit which has an adjustable resonant frequency, a temperature sensor and a controller circuit coupled to the temperature sensor. The controller circuit is designed to change the resonant frequency of the antenna resonant circuit according to a temperature sensor signal provided by the temperature sensor.
This application is a continuation application of earlier filed U.S. patent application Ser. No. 16/555,853 entitled “CIRCUIT FOR WIRELESS DATA TRANSFER COMPRISING TEMPERATURE REGULATION,” (Attorney Docket No. 2018P51034US), filed on Aug. 29, 2019, the entire teachings of which are incorporated herein by this reference.
U.S. patent application Ser. No. 16/555,853 claims priority to earlier filed European Patent Application Serial Number EP10 2018 121408.1, filed on Sep. 3, 2018, the entire teachings of which are incorporated herein by this reference.
TECHNICAL FIELDThe present description relates to the field of electronic components for wireless data transfer such as NFC reader/writer devices, RFIDs and the like.
BACKGROUNDNear field communication (NFC) is an international transmission standard based on RFID technology for contactless data-exchange by means of electromagnetically coupled coils over relatively short distances (e.g. a few centimeters) and a data transfer rate of currently 424 kbit/s maximum. This technology has been used until now primarily in the “micropayment” field (cashless payments involving small sums) and in access control. Examples of other uses are the transfer of authentication data for establishing communication via a Bluetooth or WLAN connection, for instance, and opening weblinks when a URL (Uniform Resource Locator) of a website is stored in an NFC chip. NFC is standardized in ISO/IEC 18092 (Near Field Communication Interface and Protocol-1) and ISO/IEC 21481 (Near Field Communication Interface and Protocol-2).
With regard to the payment function mentioned, many modern mobile devices such as smartphones are equipped with an NFC reader/writer. Such devices are known as NFC-enabled mobile devices. An NFC chip, often also called an NFC tag or NFC transponder, usually does not have its own energy supply and is supplied with energy from the electromagnetic field generated by an NFC-enabled mobile device. In other words, energy is transferred from the NFC-enabled mobile device to the NFC chip, whereas data transfer is possible in both directions. Currently available NFC-enabled devices usually work at a fixed transmit power and do not allow any power regulation. The set transmit power can vary markedly depending on the type and manufacturer of the NFC-enabled device. For example, there are NFC-enabled smartphones that work with about ten times the NFC transmit power of other smartphones.
The antennas of NFC-enabled devices and NFC chips (NFC transponders) are, strictly speaking, simple conductor loops. In the various antenna circuits, these conductor loops constitute an inductance, which together with corresponding capacitances form parallel resonant circuits. For efficient energy transfer from an NFC-enabled device to an NFC chip, the antenna circuits are usually operated at the same resonant frequency, thereby maximizing the inductive coupling and the induced voltage. In standard applications, this resonant frequency is typically 13.56 MHz.
When there is good inductive coupling of the antenna of an NFC chip to the antenna of an NFC-enabled device (for instance when the NFC chip is situated very close to the mobile device), situations can arise in which more energy is transferred to the NFC chip than is needed in the NFC chip. In such situations, the excess energy must be dissipated in the NFC chip, for instance in shunt transistors. The dissipation of the excess energy can result in relatively high temperatures in an NFC chip.
BRIEF DESCRIPTIONA circuit for an NFC chip is described below. According to one exemplary embodiment, the circuit comprises an antenna for near field communication, an antenna resonant circuit which has an adjustable resonant frequency, a temperature sensor and a controller circuit coupled to the temperature sensor. The controller circuit is designed to change the resonant frequency of the antenna resonant circuit according to a temperature sensor signal provided by the temperature sensor.
In accordance with further embodiments, the antenna resonant circuit (R) comprises an adjustable capacitance, and wherein the controller circuit is operative to change the adjustable capacitance for the purpose of changing the resonant frequency.
In yet further embodiments, the circuit further includes: an RF front end, which is coupled to the antenna and is operative to generate a supply voltage on the basis of an RF signal received by the antenna.
In still further embodiments, the RF front end (11) includes a reader/writer for near field communication.
In further example embodiments, the circuit includes sensor electronics for acquiring and processing one or more sensor signals. A controller coupled to the sensor electronics is operative to transfer, via the RF front end and the antenna, the processed sensor signals, or information dependent thereon, to an external device.
According to another exemplary embodiment, the circuit comprises an antenna for near field communication (NFC), which is designed to receive an RF signal from an external NFC-enabled device. The circuit also comprises an RF front end connected to the antenna and having an NFC reader/writer, and comprises a temperature sensor, which provides a temperature sensor signal. Coupled to the temperature sensor is a controller, which is designed to transmit data to the NFC-enabled device using the NFC reader/writer and on the basis of the temperature sensor signal, which data causes the NFC-enabled device to change the power of the RF signal. In accordance with further embodiments, the controller is operative to send, depending on the temperature sensor signal, using the NFC reader/writer, a request to the NFC-enabled device to adjust the power of the RF signal.
In addition, a method for stabilizing the temperature in an NFC chip is described. According to one exemplary embodiment, the method comprises measuring a temperature of a chip (circuit) by means of a temperature sensor, and varying a resonant frequency of an antenna resonant circuit comprising an antenna that is coupled to an NFC reader/writer arranged in the NFC chip. In accordance with further embodiments, the method includes adjusting a capacitance of a capacitor in the antenna resonant circuit to change the resonant frequency.
According to one exemplary embodiment, the method comprises receiving an RF signal by means of a reader/writer for near field communication, measuring a chip temperature by means of a temperature sensor, transferring data on the basis of the temperature signal to an NFC-enabled device, and the NFC-enabled device changing the power of the RF signal in response to the transferred data.
Various exemplary embodiments are explained in greater detail below with reference to figures. The diagrams are not necessarily to scale and the exemplary embodiments are not limited just to the aspects shown. The aim is rather to illustrate the principles behind the exemplary embodiments. In the figures:
As mentioned in the introduction, near field communication (NFC) is a standard for transferring energy and data between an NFC-enabled device 2 such as a tablet computer or a smartphone, for instance, and an NFC chip 1. This situation is shown in
NFC chips can be employed in various applications. NFC is mainly used for authentication, for example in association with payment systems (e.g. micropayment) or systems for access control. A relatively new use is coupling sensors to an NFC-enabled mobile device such as a smartphone, for instance, by means of near field communication. In this case, the sensor electronics comprises an RFID front end (radiofrequency (RF) front end circuit) for near field communication with the mobile device. The mobile device can be used, for instance in a measurement application, for further processing of measurement data transferred by means of NFC from the sensor electronics to the mobile device, and to display this measurement data on a screen of the mobile device. In addition, the mobile device can receive user inputs and transfer these user inputs by means of NFC to the sensor electronics. The mobile device can thereby act as a human-machine interface for the sensor electronics.
Sensor apparatuses such as the example shown in
As mentioned, the NFC chip 1 can also be supplied with energy by means of NFC. Latest NFC-enabled devices, however, do not allow any control of the transferred power (energy per unit of time), and the NFC interfaces at both ends (NFC-enabled device 2, NFC chip 1) are usually designed to achieve optimum inductive coupling. The power that is not needed by the NFC chip 1 is dissipated in the form of heat, for instance in an electrical resistor, which in the NFC chip 1 results in a temperature rise. In many uses, a raised temperature is of no further relevance, but in sensor applications, temperature fluctuations have a negative impact on the accuracy of the measurement. The following exemplary embodiments provide a solution for regulating or stabilizing (within certain limits) the temperature in the NFC chip.
Even though not shown explicitly in
A explained above, the temperature in the NFC chip 1 can rise if too much power is transferred to the RFID front end 11 via the NFC transmission channel In order to counteract this temperature rise, the NFC chip 1 can comprise a temperature sensor 12, which provides a temperature measurement signal, which is input to a controller circuit 13. This controller circuit 13 is designed to change the resonant frequency fR of the antenna resonant circuit R so that the resonant frequency fR is no longer matched to the carrier frequency used for the near field communication (NFC). The result of said detuning of the resonant frequency fR is that the power received by the RFID front end 11 falls, and hence less power has to be dissipated, and the temperature in the NFC chip can fall again. The detuning of the resonant frequency fR of the antenna resonant circuit R can be achieved, for example, by changing the capacitance of the capacitor CR. For this purpose, the capacitor can be designed, for example, as a digitally tunable capacitor (DTC) or as a varactor.
The temperature controller 13 facilitates a closed control loop, which is shown schematically in
For example, the resonant frequency fR can be adapted according to the difference STEMP-SREF (difference between measured temperature and reference temperature). If the level of the temperature signal STEMP is higher than the (e.g. constant) level of the reference signal SREF, then the resonant frequency fR can be increased until the (constant) carrier frequency fC used by the NFC-enabled device 2 (e.g. fC=13.56 MHz) lies no longer within (or at the edge of) the resonance peak of the antenna resonant circuit R. If the level of the temperature signal STEMP is lower than the level of the reference signal SREF, then the resonant frequency fR can be shifted towards the carrier frequency used by the NFC-enabled device 2 so that the carrier frequency lies in the central region of the resonance peak.
The methods for regulating/stabilizing the temperature in an NFC chip, which are implemented by the exemplary embodiments described above, are summarized below.
Claims
1. An apparatus comprising:
- antenna hardware operative to receive near field communications from a communication device;
- a resonant circuit component to control a resonant frequency of operating the antenna hardware; and
- a controller operative to: i) receive a temperature sensor signal from a temperature sensor, the temperature sense signal indicative of a temperature sensed by the temperature sensor, and ii) adjust the resonant frequency of operating the antenna hardware to regulate the temperature with respect to a reference temperature.
2. The apparatus as in claim 1, wherein the controller is further operative to adjust the resonant frequency and regulate the temperature via adjustments to the resonant circuit component.
3. The apparatus as in claim 2, wherein the resonant circuit component is a capacitor component whose capacitance is adjustable.
4. The apparatus as in claim 3, wherein the controller is operative to regulate the temperature with respect to the reference temperature via application of the adjustments to the resonant circuit component.
5. The apparatus as in claim 1, wherein the temperature represents a temperature of a chip component including the resonant circuit component.
6. The apparatus as in claim 1, wherein the controller is operative to transmit a command to the communication device depending on the temperature sensor signal, the command causing the communication device to change the power of the near field communications generated by the communication device to the antenna hardware.
7. The apparatus as claim 1, wherein the controller is operative to send, depending on the temperature, a request from the antenna hardware to the communication device to adjust a magnitude of the near field communications transmitted from the communication device.
8. The apparatus as in claim 1, wherein the resonant frequency is defined by a combination of a capacitance of the resonant frequency component and inductance of the antenna hardware.
9. The apparatus as in claim 1, wherein the controller circuit is operative to adjust a magnitude of the resonant frequency with respect to a carrier frequency of the near field communications received from the communication device depending on the temperature as indicated by the temperature sensor signal.
10. The apparatus as in claim 1 further comprising:
- a RF (Radio Frequency) signal processing circuit coupled to the antenna hardware, the RF signal processing circuit operative to convert energy received from the near field communications received from the communication device into a power supply voltage to power a circuit; and
- wherein a magnitude of the energy received from the near field communications through the antenna hardware is controlled via adjustments to the resonant frequency, the controller operative to generate the adjustments to the resonant frequency based on a difference between the temperature as indicated by the temperature sensor signal and the reference temperature.
11. A method comprising:
- receiving near field communications at antenna hardware, the near field communications transmitted from a communication device;
- controlling a resonant frequency of operating the antenna hardware via a resonant circuit component; and
- via a controller: i) receiving a temperature sensor signal from a temperature sensor, the temperature sense signal indicative of a temperature sensed by the temperature sensor, and ii) adjusting the resonant frequency of operating the antenna hardware to regulate the temperature with respect to a reference temperature.
12. The method as in claim 11 further comprising:
- regulating the temperature via adjustments to the resonant circuit component, the adjustments the resonant frequency.
13. The method as in claim 12, wherein the resonant circuit component is a capacitor component; and
- wherein adjusting the resonant frequency includes adjusting a capacitance of the capacitor component.
14. The method as in claim 11 further comprising:
- regulating the temperature with respect to the reference temperature via adjustments to the resonant circuit component.
15. The method as in claim 11, wherein the temperature represents a temperature of a chip component in which the resonant circuit component resides.
16. The apparatus as in claim 11 further comprising:
- transmitting a command from the antenna hardware to the communication device depending on the temperature sensor signal, the command causing the communication device to change the power of the near field communications generated by the communication device to the antenna hardware.
17. The method as claim 11 further comprising:
- via a command transmitted from the antenna hardware, sending a request to the communication device to adjust a magnitude of the near field communications transmitted from the communication device depending on the temperature.
18. The method as in claim 11, wherein the resonant frequency is defined by a combination of a capacitance of the resonant frequency component and inductance of the antenna hardware.
19. The method as in claim 11 further comprising:
- adjusting a magnitude of the resonant frequency with respect to a carrier frequency of the near field communications received from the communication device depending on the temperature as indicated by the temperature sensor signal.
20. The apparatus as in claim 1 further comprising:
- via an RF (Radio Frequency) signal processing circuit coupled to the antenna hardware, converting energy received from the near field communications into a power supply voltage to power a circuit; and
- controlling a magnitude of the energy received from the near field communications through the antenna hardware via adjustments to the resonant frequency, a magnitude of the adjustments to the resonant frequency being based on a difference between the temperature as indicated by the temperature sensor signal and the reference temperature.
Type: Application
Filed: Dec 13, 2021
Publication Date: Mar 31, 2022
Inventors: Gerald Holweg (Graz), Carolin Kollegger (Stallhofen), Johannes Schweighofer (Graz), Inge Siegl (Graz), Christoph Steffan (Graz)
Application Number: 17/548,981