WO2017041496A1

WO2017041496A1 - Passive nfc communication interface having independent energy receiving antenna

Info

Publication number: WO2017041496A1
Application number: PCT/CN2016/080853
Authority: WO
Inventors: 王清斌
Original assignee: 王清斌
Priority date: 2015-09-08
Filing date: 2016-05-02
Publication date: 2017-03-16
Also published as: CN105099527B; CN105099527A

Abstract

The present invention belongs to the field of wireless communication, and specifically relates to a passive NFC communication interface having an independent energy receiving antenna. The passive NFC communication interface comprises an NFC passive communication circuit for passive communication and a radio frequency energy receiving circuit for NFC radio frequency energy receiving. The NFC passive receiving circuit comprises an NFC communication antenna, a communication antenna matching circuit and a NFC transceiver, wherein the NFC communication antenna is connected to the NFC transceiver via the communication antenna matching circuit. According to the present invention, energy receiving power of an NFC passive communication interface is greatly improved, and a large amount of electricity is supplied to a device with the passive NFC communication interface. According to the additional electricity, the device is permitted to provide more functions, performance is higher and user experience is better. The application range of an NFC passive communication interface is greatly extended by the present invention at present and in the next few years.

Description

Passive NFC communication interface with independent energy receiving antenna

Technical field

The invention belongs to the field of wireless communications, and in particular relates to a passive NFC communication interface with an independent energy receiving antenna.

Background technique

NFC (Near Field Communication) achieves a communication distance (several centimeters) that is much shorter than conventional wireless communication due to the use of a magnetic field as an information carrier, and has the advantages of high security and ease of use. An important part of the NFC standard is the inheritance of high frequency RFID passive interfaces, allowing communication between active NFC interfaces and passive NFC interfaces. Specifically, the passive NFC interface receives RF energy from the active NFC interface to power itself and external devices to maintain internal computing and external communications. NFC passive interfaces are widely used in wireless payment, Bluetooth pairing, point-to-point transmission, passive tags and other applications, and have broad application prospects in the future Internet of Things. However, the design of the existing passive NFC communication interface is directly inherited from the RFID, the energy receiving efficiency is very low, and only a small amount of energy (about 10 mW) can be obtained from the active NFC interface, so that only the simple operation of the passive device can be maintained. Such as reading and writing internal memory. For a large number of applications for NFC passive interfaces, such as bank dual interface cards, new visual bank cards, smart wearable devices, sensor networks, etc., such low reception power greatly limits these applications. The features and performance that can be provided.

The existing solution mainly starts from reducing the power consumption of the device, so that this small amount of energy can also maintain the normal operation of the device. These solutions include the use of newer manufacturing technologies to reduce power consumption (such as upgrading from a 130nm process to a 90nm process), increasing device sleep time, and lowering the package. Set the working frequency and so on. However, these approaches either increase the cost of the device or limit the performance of the device.

Summary of the invention

In order to effectively solve the above problems, the present invention provides a passive NFC communication interface design with an independent energy receiving antenna with high receiving power, to fundamentally solve the problem of low receiving power of the NFC passive interface.

A passive NFC communication interface with an independent energy receiving antenna, comprising an NFC passive communication circuit and a radio frequency energy receiving circuit;

Further, the NFC passive communication circuit is composed of an NFC communication antenna, a communication antenna matching circuit, and an NFC transceiver, and is specifically responsible for NFC passive communication;

Further, the radio frequency energy receiving circuit is composed of a radio frequency energy receiving antenna, a radio frequency energy receiving antenna matching circuit, a bridge rectification, and a DC/DC, and is specifically responsible for receiving NFC radio frequency energy;

Further, the NFC communication antenna is connected to the NFC transceiver through a communication antenna matching circuit, the communication antenna matching circuit adjusts the impedance of the NFC communication antenna to be matched with the NFC transceiver, and the NFC transceiver demodulates the 13.56 received by the NFC communication antenna. Mhz signal, and modulate the 13.56Mhz signal to be sent to the NFC communication antenna;

Further, the NFC communication antenna receives only a very low energy signal to ensure that the RF energy receiving antenna receives most of the RF energy, and has at least one of the following properties: low Q value (<20), low inductance value (<4uH) ), low coupling with the transmitting antenna (coupling coefficient <0.2), not 13.56Mhz resonance (after connection with the communication antenna matching circuit);

Further, the RF energy receiving antenna is connected to the input of the bridge rectifier through a radio frequency energy receiving antenna matching circuit, and the output of the bridge rectifier is connected to the input of the DC/DC, and the RF energy receiving antenna matching circuit adjusts the resonance of the RF energy receiving antenna. Frequency and impedance, bridge rectification converts the received RF energy into a DC voltage, and DC/DC regulates and outputs the DC voltage;

Further, the radio frequency energy receiving antenna has the following properties: an inductance value between 3 uH and 10 uH, a Q value of 20 or more, an antenna area of 100 mm ² to 5000 mm ² , and a connection with the RF energy receiving antenna matching circuit at 13.56 Mhz resonance;

Further, the RF energy receiving antenna matching circuit adjusts the impedance of the RF energy receiving antenna to a suitable range according to an actual load condition to improve the receiving power;

Further, the rectified output end of the radio frequency energy receiving circuit is connected to the power source of the passive NFC communication interface to provide all power for the operation of the passive NFC communication interface;

Further, the passive NFC communication interface is connected to an external device through a bus, and transmits NFC data received by the NFC passive communication circuit to an external device, and receives NFC data to be transmitted from the external device;

Further, the power source of the passive NFC communication interface is connected to the external device through a certain form to provide all or part of the power for the operation of the external device.

A passive NFC communication method with an independent energy receiving antenna, which uses the above passive NFC communication interface, characterized in that the communication method comprises the following steps:

A) applying two or more antennas for NFC communication and NFC radio frequency energy reception respectively;

B) controlling the antenna that performs NFC communication to receive a very low energy signal, And adjusting the received signal impedance to match the NFC transceiver;

C) Control the antenna that performs NFC RF energy reception to increase the received power.

Further, the antenna for the NFC communication in the step B) controls the Q value below 20, the inductance value is below 4 uH, the coupling coefficient with the transmitting antenna is less than 0.2, or does not resonate at 13.56 Mhz;

The antenna for NFC radio frequency energy reception in the step C) is specifically controlled to have an inductance value of 3uH-10uH, a Q value of 20 or more, and an antenna area of 100mm ² to 5000mm ² .

Advantageous Effects of Invention: The present invention can greatly improve the energy receiving power of a passive NFC communication interface, and provides a large amount of power for a device with a passive NFC communication interface. This extra power will allow the device to offer more features, higher performance, and a better user experience. The invention greatly expands the range of applications of passive NFC communication interfaces in the current and future years.

The present invention is different from the traditional passive NFC communication interface using the same antenna for communication and energy reception. The present invention uses two or more antennas for communication and NFC radio frequency energy reception, respectively, allowing each antenna to be optimized separately, while ensuring NFC The communication performance greatly increases the RF reception power. This device with a passive NFC communication interface provides a large amount of power, allowing the device to provide more functionality, higher performance, and a better user experience. The invention greatly expands the range of applications of passive NFC communication interfaces in the current and future years.

DRAWINGS

Figure 1 is a schematic view of the electrical structure of the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Rather, the invention is to cover any alternatives, modifications, and equivalents and embodiments of the invention. Further, in order to provide a better understanding of the present invention, the specific details are described in detail in the detailed description of the invention. The invention may be fully understood by those skilled in the art without a description of these details.

As shown in FIG. 1, the present invention provides a design of a passive NFC communication interface with an independent energy receiving antenna having a high received power, the passive NFC communication interface 4 including an NFC passive communication circuit and a radio frequency energy receiving circuit. The NFC passive communication circuit includes an NFC communication antenna 1, a communication antenna matching circuit 2, and an NFC transceiver 3, and provides an NFC passive communication function; the RF energy The receiving circuit comprises a radio frequency energy receiving antenna 10, a radio frequency energy receiving antenna matching circuit 9, a bridge rectification 8, a DC/DC 7, and an NFC radio frequency energy receiving function; the NFC communication antenna 1 is connected to the NFC transceiver through the communication antenna matching circuit 2 3; the NFC communication antenna 1 receives a signal from the NFC active interface and transmits a signal generated by the NFC transceiver 3; the communication antenna matching circuit 2 adjusts the impedance of the NFC communication antenna 1 to match the NFC transceiver 3 The NFC transceiver 3 demodulates the signal from the antenna and modulates the signal sent to the antenna; the RF energy receiving antenna 10 is matched by the RF energy receiving antenna Road 9 is connected to the input of bridge rectifier 8 and the output of bridge rectifier 8 is connected. The RF energy receiving antenna 10 receives the RF energy transmitted by the NFC active interface; the RF energy receiving antenna matching circuit 9 tunes the RF energy receiving antenna 10 to a resonant frequency of 13.56 Mhz, and The antenna impedance is converted to a suitable range according to the actual load condition; the RF energy is transmitted to the bridge rectifier 8 for rectification by impedance transformation, and the obtained DC voltage is converted into a suitable voltage by DC/DC 7 to supply power to the passive NFC communication interface 4; The passive NFC communication interface 4 is connected to the external device 5 through a data bus, and the external device 5 is responsible for processing the NFC data received by the passive NFC communication interface 4 and providing the NFC data to be transmitted by the passive NFC communication interface 4; The power output of the source NFC communication interface 4 is also connected to the external device 5 for transmitting the energy received by the passive NFC communication interface 4 to the external device.

Independent antenna structure:

Unlike conventional passive NFC communication interfaces that use the same antenna for communication and energy reception, the passive NFC communication interface 4 uses separate antennas (NFC communication antenna 1 and RF energy receiving antenna 10) for communication and NFC RF energy reception, respectively. The main reason for using the independent antenna structure is that the NFC passive communication circuit and the RF energy receiving circuit have very different requirements for the antenna. For NFC passive communication circuits, in order to achieve the necessary communication bandwidth, an antenna with a lower Q value (quality factor) must be used (for example, Q < 20). The higher the quality factor, the stronger the antenna selectivity and the lower the bandwidth. On the contrary, for the RF energy receiving circuit, in order to improve the receiving efficiency and power at 13.56 Mhz, it is necessary to use an antenna with a high Q value (for example, Q>50). The contradiction of the Q value requirement determines that the receiving efficiency and power cannot be effectively improved under the premise of ensuring communication performance. Therefore, the use of a single antenna greatly limits the NFC RF energy that the system can receive.

The passive NFC communication interface 4 uses separate antennas, and the NFC communication antenna 1 and the RF energy receiving antenna 10 are responsible for communication and energy reception, respectively. Since multiple antennas can be optimized separately, communication performance and reception efficiency can be balanced.

The passive NFC communication interface 4 can use more than two antennas according to actual conditions to improve the receiving range.

Antenna system optimization:

Optimization measures for the NFC communication antenna 1 and the RF energy receiving antenna 10 are now described. The purpose of the optimization is to increase the energy received by the RF energy receiving antenna 10 as much as possible while ensuring the communication performance of the NFC communication antenna 1.

In the passive NFC communication interface 4, since only the energy received by the RF energy receiving antenna 10 can be collected and utilized (the energy received by the NFC communication antenna 1 will eventually be converted into heat energy and lost), in order to improve the energy receiving power, NFC communication Antenna 1 needs to reduce the received energy as much as possible (only need to meet the sensitivity of NFC transceiver 3). The NFC communication antenna 1 must have at least one of the following properties to reduce the received energy. First, low antenna Q (<25). This can be achieved by reducing the cross-sectional area of the antenna, stringing resistors into the antenna, and the like. Second, low antenna inductance (<4uH). It can be realized by using an antenna with a small number of turns, reducing the antenna area, and the like. Third, low coupling to the transmit antenna. This can be achieved by reducing the antenna area, adjusting the antenna position, and increasing the distance from the transmitting antenna. Fourth, it does not resonate at 13.56Mhz. This can be achieved by adjusting the antenna matching circuit 2.

For the RF energy receiving antenna 10, in order to allow it to receive as much energy as possible, the RF energy receiving antenna 10 and the RF energy receiving antenna matching circuit 9 are required to satisfy four conditions. First, the RF energy receiving antenna 10 is connected to the RF energy receiving antenna matching circuit 9 to resonate at 13.56 Mhz. Considering that the internal resonant capacitor of the RF energy receiving antenna matching circuit 9 is limited by the actual value, the influence of the parasitic capacitance, and the mutual inductance with the receiving antenna, the inductance value of the RF energy receiving antenna 10 cannot be too large, otherwise it cannot resonate at 13.56 Mhz. However, an excessively low inductance value results in a low received power, so the inductance value is generally suitable between 3uH and 10uH. Second, the RF energy receiving antenna 10 has as high a Q value as possible. Methods for increasing the Q value include using an antenna having a larger cross-sectional area, reducing the parasitic capacitance of the antenna, using a lower impedance antenna material, and the like. Third, the output impedance of the RF energy receiving antenna 10 connected to the RF energy receiving antenna matching circuit 9 needs to be matched with the load impedance to ensure maximum power transmission. This can be achieved by adjusting the parameters of the RF energy receiving antenna matching circuit 9. Fourth, the RF energy receiving antenna 10 needs to have a suitable area to provide sufficient coupling with the transmitting antenna. For the antenna size of a typical NFC active interface, the face of the RF energy receiving antenna 10 must be between 100 mm ² and 5000 mm ² .

RF energy receiving circuit design:

The RF energy receiving circuit is composed of an RF energy receiving antenna 10, a RF energy receiving antenna matching circuit 9, a bridge rectifier 8 and a DC/DC 7, and the function is to convert the RF energy transmitted by the NFC active interface into DC power with as little loss as possible. can. The RF energy receiving antenna matching circuit 9 is responsible for tuning the RF energy receiving antenna 10 to a resonant frequency of 13.56 Mhz and adjusting the antenna impedance to an appropriate level according to the actual load. The bridge rectifier 8 is used to convert the 13.56 Mhz RF signal into DC power, and the DC/DC 7 regulates the DC voltage. To minimize conversion losses, the bridge rectifier 8 can be a high speed, low dropout Schottky diode, and the DC/DC 7 can use a low power, high efficiency buck, boost or switched capacitor regulator.

Claims

A passive NFC communication interface having an independent energy receiving antenna, characterized in that the passive NFC communication interface comprises an NFC passive communication circuit for passive communication and a radio frequency energy receiving circuit for NFC radio frequency energy reception.
The passive NFC communication interface with an independent energy receiving antenna according to claim 1, wherein the NFC passive receiving circuit comprises an NFC communication antenna, a communication antenna matching circuit, and an NFC transceiver.
The passive NFC communication interface with an independent energy receiving antenna according to claim 2, wherein the radio frequency energy receiving circuit comprises a radio frequency energy receiving antenna, a radio frequency energy receiving antenna matching circuit, bridge rectification and DC/ DC.
A passive NFC communication interface having an independent energy receiving antenna according to claim 3, wherein said NFC communication antenna is coupled to said NFC transceiver via a communication antenna matching circuit.
A passive NFC communication interface with an independent energy receiving antenna according to claim 4, wherein said communication antenna matching circuit adjusts the impedance of the NFC communication antenna to match the NFC transceiver, the NFC transceiver Demodulating the 13.56 Mhz signal received by the NFC communication antenna and modulating the 13.56 Mhz signal to be transmitted to the NFC communication antenna;

The NFC communication antenna has at least one of the following properties: a Q value of less than 20, an inductance value of less than 4 uH, a coupling coefficient with a transmitting antenna of less than 0.2, or no resonance of 13.56 Mhz.
Passive with independent energy receiving antenna according to claim 4 The NFC communication interface is characterized in that the RF energy receiving antenna is connected to the input of the bridge rectifier through a radio frequency energy receiving antenna matching circuit, and the output of the bridge rectifier is connected to the input of the DC/DC, and the output voltage of the DC/DC Powering the passive NFC communication interface.
The passive NFC communication interface with an independent energy receiving antenna according to claim 6, wherein the RF energy receiving antenna matching circuit adjusts the resonant frequency of the RF energy receiving antenna to 13.56 Mhz, and the RF energy The impedance of the receiving antenna is adjusted to an appropriate range according to the actual load condition to increase the receiving power;

The RF energy receiving antenna has an inductance value of 3uH-10uH, a Q value of 20 or more, and an antenna area of 100mm 2 to 5000mm 2 .
The passive NFC communication interface with an independent energy receiving antenna according to claim 1, wherein the passive NFC communication interface is connected to an external device through a data bus and a power output, and the external device receives and processes the passive device. NFC data for the NFC communication interface, and NFC data that needs to be sent to provide a passive NFC communication interface.
A passive NFC communication method with an independent energy receiving antenna, the passive NFC communication interface according to any one of the preceding claims 1-8, characterized in that the communication method comprises the following steps:

A) applying two or more antennas for NFC communication and NFC radio frequency energy reception respectively;

B) controlling the antenna that performs NFC communication to receive a very low energy signal and adjusting the received signal impedance to match the NFC transceiver;

C) Control the antenna that performs NFC RF energy reception to increase the received power.
Passive with independent energy receiving antenna according to claim 9 The NFC communication method is characterized in that the antenna for the NFC communication in the step B) controls the Q value to be 20 or less, the inductance value to be 4 uH or less, the coupling coefficient with the transmitting antenna to be less than 0.2, or not to resonate at 13.56 Mhz;

The antenna for NFC radio frequency energy reception in the step C) is specifically controlled to have an inductance value of 3uH-10uH, a Q value of 20 or more, and an antenna area of 100mm 2 to 5000mm 2 .