A near field communication system and working method thereof

Abstract

The present disclosure relates to the technical field of near field communication, and discloses a near field communication system and a working method thereof, wherein the near field communication system comprises a control chip, a low pass filter module, a first matching circuit module, and a second matching circuit module; the first antenna is a differential antenna, and the second antenna is a single-ended antenna; the control chip comprises a radio frequency modulation transmission module, a differential receiving module, and a single-ended receiving module; the first receiving end and the second receiving end are respectively connected to the first antenna through a first peripheral receiving circuit, and the first receiving end, the second receiving end, the first peripheral receiving circuit, and the first antenna form a first receiving circuit; the third receiving end is connected to the second antenna through a second peripheral receiving circuit, and the third receiving end, the second peripheral receiving circuit, and the second antenna form a second receiving circuit. The working method is used for the above-mentioned near field communication system. The present disclosure can realize dual-antenna time-sharing operation, and can also achieve a larger communication area, achieve a better transmission effect, and improve the success rate of near field communication.

Description

Technical Field

[0001] The present disclosure relates to the technical field of near field communication, and in particular to a near field communication system and a working method thereof. Background Art

[0002] Near Field Communication (NFC) is an emerging technology that enables terminal devices (such as mobile phones) using NFC technology to exchange data when they are close to each other. In card reader mode, mobile terminals with NFC read and write information from media such as tags, stickers, and business cards with NFC chips. In card swipe mode, mobile terminals with NFC are equivalent to an IC card using RFID technology, which can be used as credit cards, transportation cards, access control, train tickets, etc.

[0003] As mobile phone terminals are getting bigger and bigger and foldable screen phones have appeared, there is a conflict between the card swiping and card reading positions when terminal users actually use NFC communication. For example, when swiping a card, they want to use the top of the phone; when reading a card, they want to use the middle of the phone. This places certain requirements on the performance of the dual antennas on the top and middle of the terminal device, otherwise it is easy to cause poor communication effects.

[0004] Therefore, it is a technical problem that needs to be urgently solved by technical personnel in this field to provide a near-field communication system and a working method that can realize dual-antenna time-sharing operation, while also achieving a larger communication area and a better transmission effect when the dual-antenna time-sharing operation is carried out, thereby improving the success rate of near-field communication. Summary of the invention

[0005] In order to solve the above technical problems, the present disclosure provides a near field communication system and a working method thereof, so as to solve the problem that the communication equipment with a dual antenna structure in the prior art has low communication performance and affects the user experience.

[0006] The present disclosure provides a near field communication system, including a control chip, a low-pass filter module, a first matching circuit module, a second matching circuit module, a first antenna and a second antenna; wherein the first antenna is a differential antenna and the second antenna is a single-ended antenna;

[0007] The control chip includes a radio frequency modulation and transmission module, a differential receiving module, a single-ended receiving module, a first transmitting end, a second transmitting end, a first receiving end, a second receiving end, and a third receiving end; wherein the radio frequency modulation and transmission module is connected to the first transmitting end and the second transmitting end, the first receiving end and the second receiving end are connected to the differential receiving module, and the third receiving end is connected to the single-ended receiving module;

[0008] The first transmitting end and the second transmitting end are respectively connected to two input ends of the low-pass filtering module;

[0009] The first matching circuit module is connected between the output end of the low-pass filter module and the first antenna; the second matching circuit module is connected between the output end of the low-pass filter module and the second antenna;

[0010] The first receiving end and the second receiving end are respectively connected to the first antenna through the first peripheral receiving circuit, and the first receiving end, the second receiving end, the first peripheral receiving circuit, and the first antenna form a first receiving circuit;

[0011] The third receiving end is connected to the second antenna through the second peripheral receiving circuit. The third receiving end, the second peripheral receiving circuit and the second antenna form a second receiving circuit.

[0012] Optionally, the low-pass filter module includes an EMC filter circuit formed by two first capacitors and two first inductors;

[0013] One ends of the two first inductors are connected to the first transmitting end and the second transmitting end respectively, the other ends of the two first inductors are connected to one ends of the two first capacitors respectively, and the other ends of the two first capacitors are both grounded.

[0014] Optionally, the first matching circuit module includes two second capacitors and two third capacitors, one end of the two second capacitors is connected to the output end of the low-pass filtering module, the other ends of the two second capacitors are respectively connected to one end of the two second capacitors, and the other ends of the two second capacitors are grounded;

[0015] The second matching circuit module includes two fourth capacitors and one fifth capacitor, one end of the two fourth capacitors is connected to the output end of the low-pass filter module, the other end of the two fourth capacitors is connected to one end of the fifth capacitor, and the other end of the fifth capacitor is grounded.

[0016] Further optionally, in the first matching circuit module, a first node is included between a second capacitor and a third capacitor, and a second node is included between another second capacitor and another third capacitor;

[0017] One end of the first antenna is connected to the first node, and the other end of the first antenna is connected to the second node;

[0018] In the second matching circuit module, a third node is included between the fourth capacitor and the fifth capacitor, one end of the second antenna is connected to the third node, and the other end of the second antenna is grounded.

[0019] Further optionally, two first resistors are also included between the first antenna and the first matching circuit module;

[0020] A first resistor is connected between the first node and one end of the first antenna;

[0021] Another first resistor is connected between the second node and the other end of the first antenna.

[0022] Optionally, the first peripheral receiving circuit includes two groups of sixth capacitors and second resistors connected in series, the first receiving end is connected to the first matching circuit module through one group of the sixth capacitors and second resistors connected in series, and the second receiving end is connected to the first matching circuit module through another group of the sixth capacitors and second resistors connected in series;

[0023] The second peripheral receiving circuit includes a seventh capacitor and a third resistor connected in series, and the third receiving end is connected to one end of the second antenna through the seventh capacitor and the third resistor connected in series.

[0024] Based on the same inventive concept, the present disclosure also provides a working method of a near field communication system, which is applied to the above-mentioned near field communication system; the working method includes:

[0025] The RF modulation and transmission module of the control chip controls the first signal to be sent to the first transmission end and the second signal to be sent to the second transmission end; the RF modulation and transmission module controls the phase difference and output amplitude between the first signal and the second signal;

[0026] The first signal and the second signal are modulated and converted by a low-pass filter module to filter out electromagnetic interference;

[0027] The first matching circuit module and the second matching circuit module are used to adjust the transmission load and the resonant frequency, and the first matching circuit module is used to achieve the optimal output of the first antenna efficiency, and the second matching circuit module is used to achieve the optimal output of the second antenna efficiency;

[0028] According to the different phase difference and output amplitude between the first signal and the second signal, the radiation energy output to the first antenna and the second antenna is controlled to be different;

[0029] The first receiving end and the second receiving end receive signals from the first antenna in real time through the first receiving circuit, and the differential receiving module completes amplitude detection, signal demodulation and phase detection of the signal received from the first antenna;

[0030] The third receiving end receives the signal from the second antenna in real time through the second receiving circuit, and the single-ended receiving module completes the amplitude detection, signal demodulation and phase detection of the signal received from the second antenna;

[0031] The control chip selects one of the first antenna and the second antenna to communicate with the card reader device through a field detection algorithm in a card simulation mode of the near field communication system according to the detection results of the differential receiving module and the detection results of the single-ended receiving module.

[0032] Optionally, the first antenna and the second antenna work in time sharing;

[0033] The radio frequency modulation and transmission module controls the output amplitudes of the first signal and the second signal to be equal, the phase difference is 180°, the first antenna works, and the second antenna does not work;

[0034] The radio frequency modulation and transmission module controls the output amplitudes of the first signal and the second signal to be equal, the phase difference is 0°, the first antenna does not work, and the second antenna works.

[0035] Optionally, the detection result of the differential receiving module and the detection result of the single-ended receiving module include any one of electric field strength, receiving current, receiving power and received signal strength indication.

[0036] Further optionally, in a card emulation mode of the near field communication system, selecting one of the first antenna and the second antenna to communicate with the card reader device through a field detection algorithm includes:

[0037] The detection result of the differential receiving module includes a received signal strength indicator value A of the first antenna, and the detection result of the single-ended receiving module includes a received signal strength indicator value B of the second antenna;

[0038] The field detection algorithm includes calculating the proportion of A;

[0039] When A / A+B≥40%, the control chip selects the first antenna to communicate with the card reader;

[0040] When A / A+B<40%, the control chip selects the second antenna to communicate with the card reader.

[0041] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0042] The near-field communication system disclosed in the present invention detects and compares the signal of the first antenna received in real time by the first receiving circuit and the signal of the second antenna received in real time by the second receiving circuit through a field detection algorithm, selects to send the first antenna and the second antenna to work in time-sharing according to the received communication signal, and selects one of the first antenna and the second antenna to communicate with the external card reader device, that is, any one of the first antenna and the second antenna is full-power output when working, so that the radiation area of ​​any one of the antennas is the largest. The near-field communication system provided in the present invention can realize the output energy control of the dual antennas without adding switching devices, realize the time-sharing work of the dual antennas, and can also achieve a larger communication area and achieve a better transmission effect when the dual antennas work in time-sharing, thereby improving the success rate of near-field communication. When the near-field communication system disclosed in the present invention is applied to the terminal device, it can realize the time-sharing work of the dual antennas, and can also achieve a larger communication area and achieve a better transmission effect when the dual antennas work in time-sharing, thereby improving the success rate of near-field communication, and meeting the higher communication performance requirements of the terminal device. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0045] Figure 1 is a structural schematic diagram of a near field communication system provided by an embodiment of the present invention;

[0046] Figure 2 yes Figure 1 A schematic diagram of the structure of a near field communication system used in a terminal device;

[0047] Figure 3 yes Figure 1 A schematic diagram of structural details of a near field communication system;

[0048] Figure 4 yes Figure 3 A schematic diagram of controlling the operation of the first antenna and the second antenna;

[0049] Figure 5 yes Figure 4 Timing diagram of each signal end in;

[0050] Figure 6 yes Figure 4 Another timing diagram of each signal terminal in;

[0051] Figure 7 yes Figure 1 Another schematic diagram of structural details of a near field communication system;

[0052] Figure 8 It is a flowchart of a working method of a near field communication system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0054] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0055] Please refer to Figure 1 , Figure 1 000 is a structural diagram of a near field communication system provided by an embodiment of the present invention. The near field communication system 000 provided by this embodiment includes a control chip 10, a low-pass filter module 20, a first matching circuit module 301, a second matching circuit module 302, a first antenna 401 and a second antenna 402; wherein the first antenna 401 is a differential antenna, and the second antenna 402 is a single-ended antenna;

[0056] The control chip 10 includes a radio frequency modulation and transmission module 10A, a differential receiving module 10B, a single-ended receiving module 10C, a first transmitting end TX1, a second transmitting end TX2, a first receiving end RXN, a second receiving end RXP, and a third receiving end RX; wherein the radio frequency modulation and transmission module 10A is connected to the first transmitting end TX1 and the second transmitting end TX2, the first receiving end RXN and the second receiving end RXP are connected to the differential receiving module 10B, and the third receiving end RX is connected to the single-ended receiving module 10C;

[0057] The first transmitting terminal TX1 and the second transmitting terminal TX2 are respectively connected to two input terminals of the low-pass filter module 20;

[0058] The first matching circuit module 301 is connected between the output end of the low-pass filter module 20 and the first antenna 401; the second matching circuit module 302 is connected between the output end of the low-pass filter module 20 and the second antenna 402;

[0059] The first receiving end RXN and the second receiving end RXP are respectively connected to the first antenna 401 through the first peripheral receiving circuit 501, and the first receiving end RXN, the second receiving end RXP, the first peripheral receiving circuit 501, and the first antenna 401 form a first receiving circuit;

[0060] The third receiving end RX is connected to the second antenna 402 through the second peripheral receiving circuit 502 . The third receiving end RX, the second peripheral receiving circuit 502 , and the second antenna 402 form a second receiving circuit.

[0061] Specifically, the near field communication system of this embodiment can be used in a terminal device with a near field communication function. The near field communication system includes dual antennas, namely a first antenna 401 and a second antenna 402, wherein the first antenna 401 is a differential antenna, which is suitable for scenarios with high requirements for long-distance transmission and anti-interference, and the second antenna 402 is a single-ended antenna, which is suitable for short-distance data transmission, and the transmission is simple and common. The near field communication system of this embodiment uses two different types of antennas, which can make the terminal device using the near field communication system of this embodiment suitable for different application environments, and the near field communication system can perform contactless short-range wireless communication with an external NFC device (such as an external card reader). The near field communication system 000 includes a control chip 10, which can be an NFC control chip (Near Field Communication Controller, NFCC, also called NFC chip). The control chip 10 includes a first transmitting terminal TX1 and a second transmitting terminal TX2, and the first transmitting terminal TX1 and the second transmitting terminal TX2 are respectively connected to two input terminals of a low-pass filter module 20, and the low-pass filter module 20 is used to filter the signals sent and output by the first transmitting terminal TX1 and the second transmitting terminal TX2 to output a sinusoidal wave waveform with a frequency of 13.56 MHz. The working frequency of the contactless IC card reader is 13.56 MHz, so through the low-pass filter module 20, the working frequency of the near-field communication system 000 can be achieved at 13.56 MHz, and the inductive coupling and data transmission realize wireless identification and communication. The control chip 10 includes a radio frequency modulation and transmission module 10A, and the radio frequency modulation and transmission module 10A is connected to the first transmitting terminal TX1 and the second transmitting terminal TX2, and is used to provide signals to the first transmitting terminal TX1 and the second transmitting terminal TX2 respectively. The control chip 10 includes a first receiving terminal RXN, a second receiving terminal RXP and a differential receiving module 10B, the first receiving terminal RXN and the second receiving terminal RXP are connected to the differential receiving module 10B, and the differential receiving module 10B is used to receive the signals of the first receiving terminal RXN and the second receiving terminal RXP, and perform signal amplitude detection, signal demodulation and phase detection on the received signals. The control chip 10 includes a third receiving terminal RX and a single-ended receiving module 10C, the third receiving terminal RX is connected to the single-ended receiving module 10C, and the single-ended receiving module 10C is used to receive the signal of the third receiving terminal RX, and perform signal amplitude detection, signal demodulation and phase detection on the received signals.

[0062] The first matching circuit module 301 is connected between the output end of the low-pass filter module 20 and the first antenna 401. The first matching circuit module 301 is used to adjust the load impedance of the first transmitting end TX1 and the second transmitting end TX2 transmitting signals and adjust the resonant frequency to 13.56MHz to achieve the optimal transmission efficiency of the first antenna 401. The first receiving end RXN and the second receiving end RXP are respectively connected to the first antenna 401 through the first peripheral receiving circuit 501. The first receiving end RXN, the second receiving end RXP, the first peripheral receiving circuit 501, and the first antenna 401 form a first receiving circuit. Since the signal amplitude of the first antenna 401 can generally reach 40Vpp when it is working, and the signals received by the first receiving end RXN and the second receiving end RXP are only 1.8Vpp, the first peripheral receiving circuit 501 can be used to achieve signal isolation and pre-attenuation. The second matching circuit module 302 is connected between the output end of the low-pass filter module 20 and the second antenna 402. The second matching circuit module 302 is used to adjust the load impedance of the transmission signal of the first transmitting end TX1 and the second transmitting end TX2 and adjust the resonant frequency to 13.56MHz to achieve the optimal transmission efficiency of the second antenna 402. The third receiving end RX is connected to the second antenna 402 through the second peripheral receiving circuit 502. The third receiving end RX, the second peripheral receiving circuit 502, and the second antenna 402 form a second receiving circuit. Since the signal amplitude of the second antenna 402 can generally reach 40Vpp (peak-to-peak voltage is 40V) when it is working, and the signal received by the third receiving end RX is only 1.8Vpp (peak-to-peak voltage is 1.8V), the second peripheral receiving circuit 502 can be used to achieve signal isolation and pre-attenuation.

[0063] When the near field communication system provided in this embodiment is working, the RF modulation and transmission module 10A of the control chip 10 first sends a first signal to the first transmitting terminal TX1 and sends a second signal to the second transmitting terminal TX2, and controls the phase difference and output amplitude of the first signal and the second signal; after the low-pass filter module 20 modulates the signal conversion to eliminate electromagnetic interference, there is a certain distribution relationship between the radiation energy transmitted and output to the first antenna 401 and the second antenna 402, and then by realizing the phase difference and output amplitude between the first transmitting terminal TX1 and the second transmitting terminal TX2, the distribution of the radiation energy of the two antennas can be controlled. The first matching circuit module 301 and the second matching circuit module 302 are used to adjust the transmission load and the resonant frequency, and the first antenna 401 is realized to have the best efficiency output through the first matching circuit module 301; and the second antenna 402 is realized to have the best efficiency output through the second matching circuit module 302. Then the differential receiving module 10B and the single-ended receiving module 10C receive signals from the first antenna 401 and the second antenna 402 in real time, and independently complete the detection and judgment of the received signals, such as completing the antenna end signal amplitude detection, signal demodulation and phase detection, so as to realize the communication between the antenna and the object under test, card detection, radio frequency field detection, etc. Specifically, the first receiving end RXN and the second receiving end RXP receive signals from the first antenna 401 in real time through the first receiving circuit, and the differential receiving module 10B completes the signal amplitude detection, signal demodulation and phase detection received from the first antenna 401; the third receiving end RX receives signals from the second antenna 402 in real time through the second receiving circuit, and the single-ended receiving module 10C completes the signal amplitude detection, signal demodulation and phase detection received from the second antenna 402. Finally, according to the detection results of the differential receiving module 10B and the single-ended receiving module 10C, the first antenna 401 and the second antenna 402 select the optimal antenna to communicate with the card reader device through the field detection algorithm when they are in PICC mode; specifically, the control chip 10 selects one of the first antenna 401 and the second antenna 402 to communicate with the external card reader device through the field detection algorithm according to the detection results of the differential receiving module 10B and the detection results of the single-ended receiving module 10C in the card simulation mode of the near field communication system 000, that is, the PICC mode. The end user can achieve an increase in the communication coverage area in the optimal antenna selection communication scenario without perception.

[0064] Due to the single antenna of the fixed position of the terminal device in the prior art, the communication range of the received communication signal is limited to a certain extent. In this embodiment, the coverage area of ​​the communication range of the received communication signal can be increased by setting the first antenna and the second antenna; in terms of transmission power, the near field communication system 000 of this embodiment selects one of the first antenna 401 and the second antenna 402 to communicate with the external card reader device through the field detection algorithm, that is, full power transmission is used, and any of the first antenna 401 and the second antenna 402 is full power output when working, so that the radiation area of ​​any antenna is the largest. In this embodiment, the first antenna 401 and the second antenna 402 are selected to work in time-sharing mode through the received communication signal. When in PICC mode, it can be understood that any antenna in the working state is working in the normal sending and receiving mode, so the communication area can be greatly improved. Therefore, the near field communication system 000 provided in this embodiment can realize the output energy control of the dual antenna without adding switching devices, realize the time-sharing operation of the dual antenna, and can also achieve a larger communication area and a better transmission effect when the dual antenna is working in time-sharing mode, thereby improving the success rate of near field communication.

[0065] Optional, such as Figure 2 As shown, Figure 2 yes Figure 1Schematic diagram of the structure of the near field communication system used in the terminal device. When the near field communication system 000 in this embodiment is applied to the terminal device 111, the first antenna 401 and the second antenna 402 can be installed at different positions of the terminal device 111. For example, the first antenna 401 can be installed at the top 111A of the terminal device 111, and the second antenna 402 can be installed at the middle 111B of the terminal device 111. When the user actually uses NFC communication, if the top 111A of the terminal device 111 is used to swipe the card, the first antenna 401 is closer to the external card reader. According to the detection result of the received signal, for example, the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is a stronger RSSI (received signal strength indication) value, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is a weaker RSSI (received signal strength indication) value, then the control chip 10 can select the first antenna 401 to communicate with the external card reader through the field detection algorithm, and the second antenna 402 does not work. The signals sent by the radio frequency modulation transmission module 10A to the first transmitting end TX1 and the second transmitting end TX2 are all sent at full power. When the first antenna 401 is working, it outputs at full power, and the radiation area is the largest. In this way, the communication area can be greatly improved, and a better transmission effect is achieved, and the success rate of near-field communication is improved. The communication performance requirements are met. Similarly, if the middle part 111B of the terminal device 111 is used to perform a card reading operation, the second antenna 402 is closer to the external card reading device. Through the detection result of the received signal, for example, the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is a weaker RSSI (received signal strength indication) value, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is a stronger RSSI (received signal strength indication) value, then the control chip 10 can select the second antenna 402 through the field detection algorithm to communicate with the external card reading device, the first antenna 401 is not working, and the signals sent by the RF modulation and transmission module 10A to the first transmitting end TX1 and the second transmitting end TX2 are all sent at full power. When the second antenna 402 is working, it outputs at full power and the radiation area is the largest. In this way, the communication area can be greatly improved, a better transmission effect can be achieved, the success rate of near-field communication can be improved, and the communication performance requirements can be met. Therefore, when the near-field communication system 000 provided in this embodiment is applied to the terminal device 111, it can realize dual-antenna time-sharing operation, and can also achieve a larger communication area and better transmission effect when the dual-antenna time-sharing operation is carried out, thereby improving the success rate of near-field communication and meeting the higher communication performance requirements of the terminal device.

[0066] Optionally, in this embodiment, the detection result of the differential receiving module 10B and the detection result of the single-ended receiving module 10C may include any one of the electric field strength, the receiving current, and the receiving power in addition to the received signal strength indication. The receiving current can be calculated by Ohm's law based on the voltage received by the antenna and the input impedance of the antenna. The received voltage can be converted into the electric field strength. If the antenna coefficient is known, the electric field strength can be calculated using the formula E=V / AF, where V represents the voltage received by the antenna and AF represents the antenna coefficient. The received power can be calculated based on the received current or received voltage and input impedance of the antenna. Therefore, the detection result of the differential receiving module 10B and the detection result of the single-ended receiving module 10C may be any one of the above, and both can reflect the strength of the signal received by the first antenna 401 and the second antenna 402.

[0067] In some optional embodiments, please refer to Figure 1 and Figure 3 , Figure 3 yes Figure 1 A schematic diagram of the structural details of a near-field communication system. In this embodiment, the low-pass filter module 20 includes an EMC filter circuit formed by two first capacitors C0 and two first inductors L0; one end of the two first inductors L0 is respectively connected to the first transmitting terminal TX1 and the second transmitting terminal TX2, and the other end of the two first inductors L0 is respectively connected to one end of the two first capacitors C0, and the other end of the two first capacitors C0 is grounded GND. The low-pass filter module 20 filters the signal output by the first transmitting terminal TX1 and the second transmitting terminal TX2 to obtain a filtered signal, which is, for example, a fundamental signal obtained after filtering to eliminate the harmonic signal in the transmitting signal. The signal output by the first transmitting terminal TX1 and the second transmitting terminal TX2 of this embodiment can output a sinusoidal waveform with a frequency of 13.56MHz after filtering by the low-pass filter module 20.

[0068] The first matching circuit module 301 of this embodiment includes two second capacitors C11 and two third capacitors C12, one end of the two second capacitors C11 are connected to the output end of the low-pass filter module 20, the other ends of the two second capacitors C11 are respectively connected to one end of the two second capacitors C12, and the other ends of the two second capacitors C12 are grounded GND; the first matching circuit module 301 is used to receive the filtered signal output by the low-pass filter module 20 and output the first excitation signal to the first antenna 401, and the first excitation signal is used to drive the first antenna 401 to generate a magnetic field. One second capacitor C11 in the first matching circuit module 301 is mainly used to achieve impedance matching of one end of the first antenna 401 to the first transmitting end TX1 to achieve optimal transmission efficiency, and the other second capacitor C11 is mainly used to achieve impedance matching of the other end of the first antenna 401 to the second transmitting end TX2 to achieve optimal transmission efficiency; the two third capacitors C12 in the first matching circuit module 301 are mainly used to make the resonant frequency of the first antenna 401 above 13.56MHz.

[0069] The second matching circuit module 302 of this embodiment includes two fourth capacitors C21 and one fifth capacitor C22, one end of each of the two fourth capacitors C21 is connected to the output end of the low-pass filter module 20, the other end of each of the two fourth capacitors C21 is connected to one end of the fifth capacitor C22, and the other end of the fifth capacitor C22 is grounded GND. The second matching circuit module 302 is used to receive the filtered signal output by the low-pass filter module 20 and output a second excitation signal to the second antenna 402, and the second excitation signal is used to drive the second antenna 402 to generate a magnetic field. One of the fourth capacitors C21 in the second matching circuit module 302 is mainly used to achieve impedance matching of one end of the second antenna 402 to the first transmitting end TX1 to achieve optimal transmission efficiency, and another fourth capacitor C21 is mainly used to achieve impedance matching of the other end of the second antenna 402 to the second transmitting end TX2 to achieve optimal transmission efficiency; one of the fifth capacitors C22 in the second matching circuit module 302 is mainly used to make the resonant frequency of the second antenna 402 at 13.56MHz.

[0070] It can be understood that in the first matching circuit module 301 of the present embodiment, a first node N1 is included between a second capacitor C11 and a third capacitor C12, and a second node N2 is included between another second capacitor C11 and another third capacitor C12; one end of the first antenna 401 is connected to the first node N1, and the other end of the first antenna 401 is connected to the second node N2; in the second matching circuit module 302, a third node N3 is included between the fourth capacitor C21 and the fifth capacitor C22, one end of the second antenna 402 is connected to the third node N3, and the other end of the second antenna 402 is grounded GND, thereby realizing the connection between the first matching circuit module 301 and the first antenna 401, and realizing the connection between the second matching circuit module 302 and the second antenna 402. Since the first antenna 401 is a differential antenna and the second antenna 402 is a single-ended antenna in the present embodiment, the circuit structure of the second matching circuit module 302 is different from the circuit structure of the first matching circuit module 301.

[0071] The first peripheral receiving circuit 501 of the present embodiment includes two groups of sixth capacitors Cr1 and second resistors Rr1 connected in series. The first receiving terminal RXN is connected to the first matching circuit module 301 through one group of sixth capacitors Cr1 and second resistors Rr1 connected in series. The second receiving terminal RXP is connected to the first matching circuit module 301 through another group of sixth capacitors Cr1 and second resistors Rr1 connected in series. The first matching circuit module 301 includes two second capacitors C11 and two third capacitors C12. One end of the two second capacitors C11 is connected to the output end of the low-pass filter module 20. One group of sixth capacitors C11 is connected in series. r1 and the second resistor Rr1 are connected between the first receiving terminal RXN and a second capacitor C11, and another group of sixth capacitors Cr1 and second resistors Rr1 are connected between the second receiving terminal RXP and another second capacitor C11. A group of sixth capacitors Cr1 and second resistors Rr1 connected in series, a second capacitor C11 and the first antenna 401 form a first receiving circuit corresponding to the first receiving terminal RXN, and another group of sixth capacitors Cr1 and second resistors Rr1 connected in series, another second capacitor C11 and the first antenna 401 form a first receiving circuit corresponding to the second receiving terminal RXP.

[0072] The second peripheral receiving circuit 502 of this embodiment includes a seventh capacitor Cr2 and a third resistor Rr2 connected in series. The third receiving end RX is connected to one end of the second antenna 402 through the seventh capacitor Cr2 and the third resistor Rr2 connected in series. The second receiving circuit corresponding to the third receiving end RX is formed by the seventh capacitor Cr2 and the third resistor Rr2 connected in series with the second antenna 402.

[0073] When the near field communication system 000 of this embodiment is working, the first receiving end RXN and the second receiving end RXP receive signals from the first antenna 401 in real time through the first receiving circuit, and the differential receiving module 10B completes the amplitude detection, signal demodulation and phase detection of the signal received from the first antenna 401; the third receiving end RX receives signals from the second antenna 402 in real time through the second receiving circuit, and the single-ended receiving module 10C completes the amplitude detection, signal demodulation and phase detection of the signal received from the second antenna 402. The control chip 10 uses the field detection algorithm to obtain, based on the detection result, that if the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is a stronger RSSI (received signal strength indication) value, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is a weaker RSSI (received signal strength indication) value, it means that the first antenna 401 is closer to the external card reader device, then the control chip 10 can select the first antenna 401 to communicate with the external card reader device through the field detection algorithm, and the second antenna 402 does not work; The control chip 10 uses a field detection algorithm based on the detection result. If the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is that the RSSI (received signal strength indication) value is weaker, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is that the RSSI (received signal strength indication) value is stronger, it means that the second antenna 402 is closer to the external card reader device. The control chip 10 can select the second antenna 402 to communicate with the external card reader device through the field detection algorithm, and the first antenna 401 does not work.

[0074] Optionally, in this embodiment, the control chip 10 controls the first antenna 401 and the second antenna 402 to work in a preferential time-sharing manner, and the first antenna 401 and the second antenna 402 may work in a time-sharing manner. Figure 3 , Figure 4 and Figure 5 As shown, Figure 4 yes Figure 3 The schematic diagram of controlling the operation of the first antenna and the second antenna is shown in FIG. Figure 5 yes Figure 4 In the timing diagram of each signal end, the RF modulation and transmission module 10B of the control chip 10 controls the first signal to be sent to the first transmission end TX1 and the second signal to be sent to the second transmission end TX2; the RF modulation and transmission module 10B controls the phase difference and output amplitude of the first signal and the second signal; Figure 5As shown, the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 180°. After the low-pass filter module 20 modulates the signal conversion, filters out the electromagnetic interference, and the first matching circuit module 301 adjusts the transmitting load and the resonant frequency, one end of the first antenna 401 (point K1) and the other end of the first antenna 401 (point K2) form a potential difference, there is current on the first antenna 401, and the first antenna 401 works; while the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 180° (the first signal and the second signal are equal in amplitude and opposite in phase), and the signal waveforms formed by sending to one end (point K3) of the second antenna 402 cancel each other, and one end (point K3) of the second antenna 402 and the other end (point K4) of the second antenna 402 are both 0V, there is no potential difference, there is no current in the second antenna 402, and the second antenna 402 does not work.

[0075] like Figure 3 , Figure 4 and Figure 6 As shown, Figure 4 yes Figure 3 The schematic diagram of controlling the operation of the first antenna and the second antenna is shown in FIG. Figure 6 yes Figure 4 Another timing diagram of each signal end in the control chip 10, the RF modulation and transmission module 10B controls the first signal to be sent to the first transmission end TX1, and the second signal to be sent to the second transmission end TX2; the RF modulation and transmission module 10B controls the phase difference and output amplitude of the first signal and the second signal; Figure 6 As shown, the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 0°. After the low-pass filter module 20 modulates the signal conversion, filters out the electromagnetic interference, and the first matching circuit module 301 adjusts the transmitting load and the resonant frequency, there is no potential difference between one end (point K1) of the first antenna 401 and the other end (point K2) of the first antenna 401, there is no current on the first antenna 401, and the first antenna 401 does not work; while the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 0° (the first signal and the second signal are equal in amplitude and in phase), and the signal waveform formed by sending to one end (point K3) of the second antenna 402 is superimposed in half a period, and one end (point K3) of the second antenna 402 and the other end (point K4) of the second antenna 402 form a potential difference, there is current on the second antenna 402, and the second antenna 402 works.

[0076] From the above, it can be seen that the control chip 10 of this embodiment controls the first antenna 401 and the second antenna 402 to work in a preferential time-sharing manner, and the signals sent by the RF modulation and transmission module 10A to the first transmitting end TX1 and the second transmitting end TX2 are all sent at full power. The first antenna 401 and the second antenna 402 are both full-power output when they work in a time-sharing manner, and the radiation area is the largest. In this way, the communication area can be greatly improved, a better transmission effect can be achieved, and the success rate of near-field communication is improved.

[0077] In some optional embodiments, please refer to Figure 1 and Figure 7 , Figure 7 yes Figure 1 Another schematic diagram of structural details of the near-field communication system. In this embodiment, two first resistors Rq are also included between the first antenna 401 and the first matching circuit module 301; one first resistor Rq is connected between the first node N1 and one end of the first antenna 401; and the other first resistor Rq is connected between the second node N2 and the other end of the first antenna 401.

[0078] This embodiment explains that a first resistor Rq can also be set between the first antenna 401 and the first matching circuit module 301. Since an excessively large Q value of the antenna (the ratio of the energy stored in the antenna to the energy dissipated per cycle) may lead to a degradation in RF performance, a first resistor Rq is set between the first node N1 and one end of the first antenna 401, and another first resistor Rq is connected between the second node N2 and the other end of the first antenna 401, which can be used to attenuate the Q value of the first antenna 401, thereby improving the RF performance of the first antenna 401.

[0079] In some optional embodiments, please refer to Figure 1-Figure 7 and Figure 8 , Figure 8 It is a flowchart of a working method of a near field communication system provided by an embodiment of the present invention. The working method of a near field communication system provided by this embodiment can be applied to the near field communication system 000 of any of the above embodiments; the working method of this embodiment includes:

[0080] S11: The RF modulation and transmission module 10A of the control chip 10 controls the first signal to be sent to the first transmission end TX1 and the second signal to be sent to the second transmission end TX2; the RF modulation and transmission module 10A controls the phase difference and output amplitude (such as Figure 3-Figure 6 shown);

[0081] S12: The first signal and the second signal are modulated and converted by the low-pass filter module 20 to filter out electromagnetic interference;

[0082] S13: The first matching circuit module 301 and the second matching circuit module 302 are used to adjust the transmission load and the resonant frequency, and the first matching circuit module 301 is used to achieve the optimal output efficiency of the first antenna 401, and the second matching circuit module 302 is used to achieve the optimal output efficiency of the second antenna 402;

[0083] S14: According to the different phase difference and output amplitude between the first signal and the second signal, the radiation energy output to the first antenna 401 and the second antenna 402 is controlled to be different;

[0084] S21: The first receiving end RXN and the second receiving end RXP receive signals from the first antenna 401 in real time through the first receiving circuit, and the differential receiving module 10B completes amplitude detection, signal demodulation and phase detection of the signal received from the first antenna 401;

[0085] S22: The third receiving end RX receives a signal from the second antenna 402 in real time through the second receiving circuit, and the single-ended receiving module 10C completes amplitude detection, signal demodulation and phase detection of the signal received from the second antenna 402;

[0086] S31: The control chip 10 selects one of the first antenna 401 and the second antenna 402 to communicate with the external card reader device through the field detection algorithm according to the detection results of the differential receiving module 10B and the detection results of the single-ended receiving module 10C in the card emulation mode of the near field communication system 000. Optionally, the detection results of the differential receiving module 10B and the detection results of the single-ended receiving module 10C include any one of the electric field strength, the receiving current, the receiving power and the received signal strength indication. According to the voltage received by the antenna and the input impedance of the antenna, the receiving current can be calculated by Ohm's law. The receiving voltage can be converted into the electric field strength. If the antenna coefficient is known, the electric field strength can be calculated using the formula E=V / AF, where V represents the voltage received by the antenna and AF represents the antenna coefficient. According to the receiving current or receiving voltage and input impedance of the antenna, the receiving power can be calculated. Therefore, the detection results of the differential receiving module 10B and the detection results of the single-ended receiving module 10C can be any of the above, and both can reflect the strength of the signal received by the first antenna 401 and the second antenna 402.

[0087] Optionally, the first antenna 401 and the second antenna 402 of the present embodiment work in time-sharing mode, and one of them is selected to communicate with the external card reader device. According to the phase difference and output amplitude of the first signal and the second signal, the radiation energy output to the first antenna 401 and the second antenna 402 is controlled to be different; for example, if the RF modulation and transmission module 10A controls the output amplitudes of the first signal and the second signal to be equal, and the phase difference is 180°, the first antenna 401 works, and the second antenna 402 does not work; if the RF modulation and transmission module 10A controls the output amplitudes of the first signal and the second signal to be equal, and the phase difference is 0°, the first antenna 401 does not work, and the second antenna 402 works.

[0088] Optionally, in the card emulation mode of the near field communication system 000, selecting one of the first antenna 401 and the second antenna 402 to communicate with the card reader device through a field detection algorithm includes:

[0089] The detection result of the differential receiving module 10B includes the received signal strength indicator value A of the first antenna 401, and the detection result of the single-ended receiving module 10C includes the received signal strength indicator value B of the second antenna 402; the field detection algorithm is mainly based on the ratio of the RSSI values ​​detected by the first antenna 401 and the second antenna 402 in real time. When the RSSI value of the first antenna 401 received in real time by the differential receiving module 10B through the first receiving circuit accounts for greater than or equal to 40%, that is, when A / A+B≥40%, the control chip 10 selects the first antenna 401 to communicate with the external card reader device, and the second antenna 402 does not work; when the RSSI value of the first antenna 401 received in real time by the single-ended receiving module 10C through the second receiving circuit accounts for less than 40%, that is, when A / A+B<40%, the control chip 10 selects the second antenna 402 to communicate with the external card reader device, and the first antenna 401 does not work.

[0090] When the near field communication system 000 of this embodiment is working, the first receiving end RXN and the second receiving end RXP receive signals in real time from the first antenna 401 through the first receiving circuit, and the differential receiving module 10B completes the signal amplitude detection, signal demodulation and phase detection received from the first antenna 401; the third receiving end RX receives signals in real time from the second antenna 402 through the second receiving circuit, and the single-ended receiving module 10C completes the signal amplitude detection, signal demodulation and phase detection received from the second antenna 402.

[0091] The control chip 10 uses a field detection algorithm based on the detection result. If the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is that the RSSI (received signal strength indication) value is stronger, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is that the RSSI (received signal strength indication) value is weaker, it means that the first antenna 401 is closer to the external card reader device. The control chip 10 can select the first antenna 401 to communicate with the external card reader device through the field detection algorithm, and the second antenna 402 does not work. The RF modulation and transmission module 10B of the control chip 10 controls the first signal to be sent to the first transmission end TX1, and the second signal to be sent to the second transmission end TX2; the RF modulation and transmission module 10B controls the phase difference and output amplitude of the first signal and the second signal; the output amplitudes of the first signal of the first transmission end TX1 and the second signal of the second transmission end TX2 are controlled to be equal, and the phase difference is 180°, then the low-pass filter module 20 modulates the signal conversion, filters out electromagnetic interference, and adjusts the transmission load and the resonant frequency through the first matching circuit module 301. One end (K1 point) of the first antenna 401 and the second end (K2 point) of the first antenna 401 are connected to the first antenna 401. The other end of the first antenna 401 (point K2) forms a potential difference, there is current on the first antenna 401, and the first antenna 401 works; the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 180° (the first signal and the second signal are of equal amplitude and inverted phase), and the signal waveforms formed by sending to one end (point K3) of the second antenna 402 cancel each other out, and one end (point K3) of the second antenna 402 and the other end (point K4) of the second antenna 402 are both 0V, there is no potential difference, there is no current in the second antenna 402, and the second antenna 402 does not work.

[0092] The control chip 10 uses a field detection algorithm based on the detection result. If the detection result of the first antenna 401 obtained by the differential receiving module 10B through the first receiving circuit is that the RSSI (received signal strength indication) value is weaker, and the detection result of the second antenna 402 obtained by the single-ended receiving module 10C through the second receiving circuit is that the RSSI (received signal strength indication) value is stronger, it means that the second antenna 402 is closer to the external card reader device. The control chip 10 can select the second antenna 402 to communicate with the external card reader device through the field detection algorithm, and the first antenna 401 does not work. The RF modulation and transmission module 10B of the control chip 10 controls the first signal to be sent to the first transmission end TX1, and the second signal to be sent to the second transmission end TX2; the RF modulation and transmission module 10B controls the phase difference and output amplitude of the first signal and the second signal; controls the output amplitudes of the first signal of the first transmission end TX1 and the second signal of the second transmission end TX2 to be equal, and the phase difference is 0°, then the low-pass filter module 20 modulates the signal conversion, filters out electromagnetic interference, and adjusts the transmission load and the resonant frequency through the first matching circuit module 301. One end (point K1) of the first antenna 401 There is no potential difference between the first antenna 401 and the other end (point K2) of the first antenna 401, there is no current on the first antenna 401, and the first antenna 401 does not work; while the output amplitudes of the first signal of the first transmitting end TX1 and the second signal of the second transmitting end TX2 are equal, and the phase difference is 0° (the first signal and the second signal are of equal amplitude and in phase), and the signal waveform formed by sending to one end (point K3) of the second antenna 402 is superimposed by half a cycle, and one end (point K3) of the second antenna 402 and the other end (point K4) of the second antenna 402 form a potential difference, there is current on the second antenna 402, and the second antenna 402 works.

[0093] The working method of the near-field communication system provided in this embodiment detects and compares the signal of the first antenna 401 received in real time by the first receiving circuit and the signal of the second antenna 402 received in real time by the second receiving circuit through a field detection algorithm, and selects the first antenna 401 and the second antenna 402 to work in time-sharing according to the received communication signal. When the near-field communication system enters the PICC mode, it can be understood that any antenna in the working state is working in the normal sending and receiving mode, so that the communication area can be greatly improved. Therefore, the working method of the near-field communication system provided in this embodiment can realize the output energy control of the dual antennas without adding switching devices, realize the time-sharing operation of the dual antennas, and can also achieve a larger communication area and a better transmission effect when the dual antennas work in time-sharing, thereby improving the success rate of near-field communication.

[0094] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0095] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A near field communication system, characterized in that: It includes a control chip, a low-pass filter module, a first matching circuit module, a second matching circuit module, a first antenna and a second antenna; wherein the first antenna is a differential antenna and the second antenna is a single-ended antenna; The control chip includes a radio frequency modulation and transmission module, a differential receiving module, a single-ended receiving module, a first transmitting end, a second transmitting end, a first receiving end, a second receiving end, and a third receiving end; wherein the radio frequency modulation and transmission module is connected to the first transmitting end and the second transmitting end, the first receiving end and the second receiving end are connected to the differential receiving module, and the third receiving end is connected to the single-ended receiving module; The first transmitting end and the second transmitting end are respectively connected to two input ends of the low-pass filtering module; The first matching circuit module is connected between the output end of the low-pass filter module and the first antenna; the second matching circuit module is connected between the output end of the low-pass filter module and the second antenna; The first receiving end and the second receiving end are respectively connected to the first antenna through a first peripheral receiving circuit, and the first receiving end, the second receiving end, the first peripheral receiving circuit, and the first antenna form a first receiving circuit; The third receiving end is connected to the second antenna through a second peripheral receiving circuit, and the third receiving end, the second peripheral receiving circuit, and the second antenna form a second receiving circuit.

2. The near field communication system according to claim 1, characterized in that: The low-pass filter module includes an EMC filter circuit formed by two first capacitors and two first inductors; One ends of the two first inductors are respectively connected to the first transmitting end and the second transmitting end, the other ends of the two first inductors are respectively connected to one ends of the two first capacitors, and the other ends of the two first capacitors are both grounded.

3. The near field communication system according to any one of claims 1 or 2, characterized in that: The first matching circuit module includes two second capacitors and two third capacitors, one end of the two second capacitors is connected to the output end of the low-pass filtering module, the other ends of the two second capacitors are respectively connected to one end of the two second capacitors, and the other ends of the two second capacitors are grounded; The second matching circuit module includes two fourth capacitors and one fifth capacitor, one end of the two fourth capacitors is connected to the output end of the low-pass filtering module, the other end of the two fourth capacitors is connected to one end of the fifth capacitor, and the other end of the fifth capacitor is grounded.

4. The near field communication system according to claim 3, characterized in that: In the first matching circuit module, a first node is included between one of the second capacitors and one of the third capacitors, and a second node is included between another of the second capacitors and another of the third capacitors; One end of the first antenna is connected to the first node, and the other end of the first antenna is connected to the second node; In the second matching circuit module, a third node is included between the fourth capacitor and the fifth capacitor, one end of the second antenna is connected to the third node, and the other end of the second antenna is grounded.

5. The near field communication system according to claim 4, characterized in that: Two first resistors are also included between the first antenna and the first matching circuit module; A first resistor is connected between the first node and one end of the first antenna; Another of the first resistors is connected between the second node and the other end of the first antenna.

6. The near field communication system according to claim 3, characterized in that: The first peripheral receiving circuit includes two groups of sixth capacitors and second resistors connected in series, the first receiving end is connected to the first matching circuit module through one group of the sixth capacitors and the second resistors connected in series, and the second receiving end is connected to the first matching circuit module through another group of the sixth capacitors and the second resistors connected in series; The second peripheral receiving circuit includes a seventh capacitor and a third resistor connected in series, and the third receiving end is connected to one end of the second antenna through the seventh capacitor and the third resistor connected in series.

7. A working method of a near field communication system, characterized in that: The working method is applied to the near field communication system according to any one of claims 1 to 6; the working method comprises: The RF modulation and transmission module of the control chip controls the first signal to be sent to the first transmission end, and the second signal to be sent to the second transmission end; the RF modulation and transmission module controls the phase difference and output amplitude of the first signal and the second signal; The first signal and the second signal are modulated by the low-pass filter module to convert the signals and filter out electromagnetic interference; The first matching circuit module and the second matching circuit module are used to adjust the transmission load and the resonant frequency, and the first antenna is outputted with the best efficiency through the first matching circuit module, and the second antenna is outputted with the best efficiency through the second matching circuit module; According to the different phase differences and output amplitudes of the first signal and the second signal, controlling the radiation energies output to the first antenna and the second antenna to be different; The first receiving end and the second receiving end receive signals from the first antenna in real time through the first receiving circuit, and the differential receiving module completes amplitude detection, signal demodulation and phase detection of the signal received from the first antenna; The third receiving end receives the signal from the second antenna in real time through the second receiving circuit, and the single-ended receiving module completes amplitude detection, signal demodulation and phase detection of the signal received from the second antenna; The control chip selects one of the first antenna and the second antenna to communicate with the card reader device through a field detection algorithm in the card simulation mode of the near field communication system according to the detection results of the differential receiving module and the detection results of the single-ended receiving module.

8. The working method of the near field communication system according to claim 7, characterized in that: The first antenna and the second antenna work in time sharing; The RF modulation and transmission module controls the output amplitudes of the first signal and the second signal to be equal, the phase difference is 180°, the first antenna works, and the second antenna does not work; The radio frequency modulation and transmission module controls the output amplitudes of the first signal and the second signal to be equal, the phase difference to be 0°, the first antenna to be inoperative, and the second antenna to be operative.

9. The working method of the near field communication system according to claim 7, characterized in that: The detection result of the differential receiving module and the detection result of the single-ended receiving module include any one of electric field strength, receiving current, receiving power and received signal strength indication.

10. The working method of the near field communication system according to claim 9, characterized in that: In the card emulation mode of the near field communication system, selecting one of the first antenna and the second antenna to communicate with a card reader device through a field detection algorithm includes: The detection result of the differential receiving module includes a received signal strength indicator value A of the first antenna, and the detection result of the single-ended receiving module includes a received signal strength indicator value B of the second antenna; The field detection algorithm includes calculating the proportion of A; When A / A+B≥40%, the control chip selects the first antenna to communicate with the card reader; When A / A+B<40%, the control chip selects the second antenna to communicate with the card reading device.

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