Nfc antenna circuit and communication device comprising the same

Abstract

This application provides an NFC antenna circuit and a communication device including the same. The NFC antenna circuit includes: a first NFC coil, a second NFC coil, an NFC tag circuit, a first impedance matching circuit, and a second impedance matching circuit. The first and second NFC coils are used for coupling with other NFC devices, and the second NFC coil is larger than the first NFC coil. The NFC tag circuit is used to identify other NFC devices. The first impedance matching circuit connects the first NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to interact with other NFC devices. The tuning frequency of the first impedance matching circuit is the standard operating frequency for NFC communication. The second impedance matching circuit connects the second NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to draw power from other NFC devices. This application can achieve low-cost implementation of an NFC antenna circuit that can both communicate with other NFC devices and output control signals, thus enriching the functionality of the NFC antenna circuit.

Description

Technical Field

[0001] This application relates to the field of NFC communication technology, and more particularly to an NFC antenna circuit and a communication device including the same. Background Technology

[0002] NFC (Near Field Communication) technology has made significant progress in recent years and is widely used in payment, access control, public transportation and other fields.

[0003] Most devices using NFC technology employ a passive power source. This means that NFC devices do not have a built-in power supply. When an NFC device is brought near a card reader (e.g., a mobile phone or POS machine), the electromagnetic field emitted by the reader is sensed in the device's coil. This electromagnetic induction generates enough electrical energy to activate the device, enabling it to exchange data with the card reader. Passively powered NFC devices lack the ability to actively output control signals, thus limiting their functionality.

[0004] Some NFC devices use an active power source. These devices include a built-in power supply and can output control signals without relying on an external electromagnetic field. However, these NFC devices are relatively expensive, and their built-in power supply has limited battery life, which cannot adequately meet practical needs. Utility Model Content

[0005] This application provides a low-cost and feature-rich NFC antenna circuit and a communication device including the same.

[0006] This application provides an NFC antenna circuit, including:

[0007] A first NFC coil and a second NFC coil are used for coupling with other NFC devices, wherein the size of the second NFC coil is larger than the size of the first NFC coil;

[0008] NFC tag circuitry, used to identify other NFC devices;

[0009] A first impedance matching circuit connects the first NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to interact with other NFC devices; the tuning frequency of the first impedance matching circuit is the standard operating frequency for NFC communication.

[0010] The second impedance matching circuit connects the second NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to obtain power from other NFC devices.

[0011] The first NFC coil enables the NFC antenna circuit to communicate with other NFC devices; the second NFC coil enables the NFC antenna circuit to draw power from other NFC devices, thus allowing the NFC antenna circuit to output control signals. The first and second NFC coils are low-cost. The second NFC coil is larger than the first NFC coil, making the NFC antenna circuit more efficient at drawing power from other NFC devices, thus enabling the NFC antenna circuit to output stable control signals. In this way, the NFC antenna circuit can communicate with other NFC devices and output control signals at low cost, making the NFC antenna circuit more functional.

[0012] In some possible implementations, the tuning frequency of the second impedance matching circuit is different from the tuning frequency of the first impedance matching circuit.

[0013] The tuning frequency of the second impedance matching circuit is different from that of the first impedance matching circuit, so that the coupling of the second NFC coil with other NFC devices will not affect the coupling of the first NFC coil with other NFC devices. When drawing power from other NFC devices, the impact on the communication quality with other NFC devices is reduced.

[0014] In some possible implementations, the size of the first NFC coil is less than 3mm × 3mm.

[0015] The small size of the first NFC coil allows other NFC devices to continue reading other devices after they are coupled to the NFC antenna circuit, with minimal impact on the reading performance of other NFC devices.

[0016] In some possible implementations, the NFC antenna circuit further includes a controller, the controller including an enable port and a power supply port, the NFC tag circuit including a signal output port connected to the enable port, and the second impedance matching circuit connected to the power supply port.

[0017] The second impedance matching circuit is connected to the power supply port of the controller, which can supply power to the controller; the signal output port is connected to the enable port of the controller, so that the NFC tag circuit can output an enable signal to the controller to wake up the controller, and the controller can output control signals to the outside world, thus enabling the NFC antenna circuit to output control signals to the outside world and enriching the functions of the NFC antenna circuit.

[0018] In some possible implementations, the NFC antenna circuit further includes a rectifier circuit connected to the second impedance matching circuit and the NFC tag circuit.

[0019] The rectifier circuit rectifies the signal output from the second impedance matching circuit, making it more suitable for powering the NFC tag circuit.

[0020] In some possible implementations, the NFC antenna circuit further includes a low-dropout linear regulator circuit connected to the rectifier circuit and the NFC tag circuit.

[0021] The low-dropout linear regulator circuit can convert the unstable voltage output from the rectifier circuit into a more stable voltage, which is then output to the NFC tag circuit, thereby providing better power to the NFC tag circuit and ensuring that the NFC tag circuit IC works normally.

[0022] In some possible implementations, the rectifier circuit includes a first input terminal and a second input terminal, and the second impedance matching circuit includes a first inductor, a second inductor, a first capacitor, and a ground terminal; the first inductor is connected to a first terminal of the second NFC coil and the first input terminal, the second inductor is connected to a second terminal of the second NFC coil and the second input terminal, the first capacitor is connected in parallel between the first terminal and the second terminal of the second NFC coil, and the first capacitor is connected to the ground terminal.

[0023] The first inductor, the second inductor, and the first capacitor form an LC parallel resonant matching network, which can improve the energy transfer efficiency between the second NFC coil and other NFC devices.

[0024] In some possible implementations, the second impedance matching circuit includes a second capacitor and a third capacitor, the second capacitor being connected in series with the first inductor between a first end of the second NFC coil and the first input terminal, and the third capacitor and the second inductor being connected in series between a second end of the second NFC coil and the second input terminal.

[0025] The second capacitor, the third capacitor, the first inductor, the second inductor, and the first capacitor form a π-type LC impedance matching network, which further optimizes the impedance matching accuracy.

[0026] In some possible implementations, the NFC tag circuit includes a third input terminal and a fourth input terminal, and the first impedance matching circuit includes a third inductor, a fourth inductor, a fourth capacitor, a fifth capacitor, and a ground terminal; the third inductor is connected to a first terminal of the first NFC coil and the third input terminal, the fourth inductor is connected to a second terminal of the first NFC coil and the fourth input terminal, the fourth capacitor is connected in parallel between the first terminal and the second terminal of the first NFC coil, the fifth capacitor is connected in parallel between the third input terminal and the fourth input terminal, and the fourth and fifth capacitors are connected to the ground terminal.

[0027] The third inductor, fourth inductor, fourth capacitor, and fifth capacitor form an LC parallel resonant network, which can improve the energy transfer efficiency between the first NFC coil and other NFC devices.

[0028] This application also provides a communication device, including:

[0029] Load circuit; and

[0030] The NFC antenna circuit as described in any of the above is connected to the load circuit.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] Figure 1 The diagram shown is a circuit diagram of one embodiment of the NFC antenna circuit of this application. Detailed Implementation

[0034] This application provides an NFC antenna circuit and a communication device including the same. The NFC antenna circuit and the communication device including the same are described in detail below with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0035] Figure 1 The diagram shown is a circuit diagram of one embodiment of the NFC antenna circuit 10 of this application. Figure 1 As shown, the NFC antenna circuit 10 includes: a first NFC coil 11, a second NFC coil 12, an NFC tag circuit IC, a first impedance matching circuit 13, and a second impedance matching circuit 14.

[0036] The first NFC coil 11 and the second NFC coil 12 are used for coupling with other NFC devices. These other NFC devices are devices that use NFC technology, such as card readers. When the NFC antenna circuit 10 approaches another NFC device, and that device sends a signal at the standard operating frequency (13.56MHz) for NFC communication, the first NFC coil 11 and the second NFC coil 12 inductively couple with the other NFC device.

[0037] The second NFC coil 12 is larger than the first NFC coil 11. Coupled with the same other NFC devices, the second NFC coil 12, due to its larger size, can harvest more energy than the first NFC coil 11. Figure 1In the illustrated embodiment, the first NFC coil 11 is contained within the second NFC coil 12. In other embodiments, the first NFC coil 11 and the second NFC coil 12 may be disposed separately. The number of coil turns of the first NFC coil 11 and the second NFC coil 12 may be the same or different.

[0038] The NFC tag circuit IC is used to identify other NFC devices. When the NFC antenna circuit 10 communicates with other NFC devices, the NFC tag circuit IC can identify them. The NFC tag circuit IC includes an NFC tag chip.

[0039] The first impedance matching circuit 13 connects the first NFC coil 11 and the NFC tag circuit IC, enabling the NFC antenna circuit 10 to interact with other NFC devices. The tuning frequency of the first impedance matching circuit 13 is the standard operating frequency for NFC communication.

[0040] The tuning frequency of the first impedance matching circuit 13 is the standard operating frequency for NFC communication, enabling the NFC antenna circuit 10 to resonate at the standard operating frequency. This improves the quality factor, strengthens the magnetic field strength, and increases the recognition accuracy of the first NFC coil 11 in communication with other NFC devices. The first impedance matching circuit 13 connects the first NFC coil 11 and the NFC tag circuit IC, allowing impedance matching between the NFC tag circuit IC and other NFC devices when the first NFC coil 11 couples with them. This enables power transfer and communication with other NFC devices.

[0041] The second impedance matching circuit 14 connects the second NFC coil 12 and the NFC tag circuit IC, enabling the NFC antenna circuit 10 to obtain power from other NFC devices.

[0042] When the second NFC coil 12 couples with other NFC devices, the second impedance matching circuit 14 enables the NFC tag circuit IC to achieve impedance matching with the other NFC devices, allowing it to draw power from them. Because the second NFC coil 12 is larger, the NFC tag circuit IC can draw more power from other NFC devices, enabling it to output control signals.

[0043] The first NFC coil 11 enables the NFC antenna circuit 10 to communicate with other NFC devices; the second NFC coil 12 enables the NFC antenna circuit 10 to obtain power from other NFC devices, thereby allowing the NFC antenna circuit 10 to output control signals; the first NFC coil 11 and the second NFC coil 12 have low costs; the size of the second NFC coil 12 is larger than that of the first NFC coil 11, making the NFC antenna circuit 10 more efficient at obtaining power from other NFC devices, thus allowing the NFC antenna circuit 10 to output stable control signals; in this way, the NFC antenna circuit 10 can communicate with other NFC devices and output control signals at low cost, making the NFC antenna circuit 10 more functional.

[0044] In some possible implementations, the tuning frequency of the second impedance matching circuit 14 is different from the tuning frequency of the first impedance matching circuit 13.

[0045] The tuning frequency of the first impedance matching circuit 13 is the standard operating frequency (13.56MHz), and the tuning frequency of the second impedance matching circuit 14 can be greater than or less than the standard operating frequency (13.56MHz). In this way, the first impedance matching circuit 13 and the second impedance matching circuit 14 will not resonate simultaneously, reducing the mutual interference of the coupling between the first NFC coil 11 and the second NFC coil 12. In some embodiments, the tuning frequency of the second impedance matching circuit 14 is in the range of 13.56MHz to 20MHz, which can ensure high energy harvesting efficiency.

[0046] The tuning frequency of the second impedance matching circuit 14 is different from that of the first impedance matching circuit 13, so that the coupling of the second NFC coil 12 with other NFC devices will not affect the coupling of the first NFC coil 11 with other NFC devices, thereby reducing the impact on the communication quality with other NFC devices when obtaining power from other NFC devices.

[0047] In some possible implementations, the size of the first NFC coil 11 is less than 3mm × 3mm.

[0048] The first NFC coil 11 is relatively small in size. When coupled to other NFC devices, the energy generated is concentrated in a small area, thus minimizing external interference. After coupling with the first NFC coil 11, other NFC devices can also couple with other NFC coils. The multiple coils are less prone to mutual interference, allowing other NFC devices to read from multiple devices and improving their performance.

[0049] In some embodiments, the first NFC coil 11 is a square coil with dimensions less than 3mm × 3mm. In other embodiments, the first NFC coil 11 is a circular coil with an inner diameter less than 3mm.

[0050] The small size of the first NFC coil 11 allows other NFC devices to continue reading other devices after they are coupled to the NFC antenna circuit 10, with minimal impact on the reading performance of other NFC devices.

[0051] In some embodiments, the size of the first NFC coil is less than 1.5mm × 1.5mm.

[0052] In some possible implementations, the NFC antenna circuit 10 also includes a controller MCU, which includes an enable port T1 and a power supply port VCC1. The NFC tag circuit IC includes a signal output port T3, which is connected to the enable port T1. The second impedance matching circuit 14 is connected to the power supply port VCC1.

[0053] The controller MCU is connected to the NFC tag circuit IC and can receive control signals from the NFC tag circuit IC. The controller MCU can also be connected to other load circuits to control them. The second impedance matching circuit 14 is connected to the power supply port VCC1 of the controller MCU, thus providing power to the controller MCU and enabling it to operate. The signal output port T3 of the NFC tag circuit IC is connected to the enable port T1 of the controller MCU. The NFC tag circuit IC can output an enable signal to the controller MCU, allowing the controller MCU to output control signals to subsequent load circuits and control their operation. Since the signal output of the NFC tag circuit IC itself is relatively small and difficult to directly control the load circuit, sending an enable signal to the controller MCU to control the load circuit improves the signal output capability of the NFC antenna circuit 10. When it is necessary to control the load circuit, the NFC antenna circuit 10 can actively output control signals to achieve control of the load circuit.

[0054] The second impedance matching circuit 14 is connected to the power supply port VCC1 of the controller MCU, which can supply power to the controller MCU; the signal output port T3 is connected to the enable port T1 of the controller MCU, so that the NFC tag circuit IC can output an enable signal to the controller MCU, wake up the controller MCU, and the controller MCU can output control signals to the outside world, so that the NFC antenna circuit 10 can output control signals to the outside world, enriching the functions of the NFC antenna circuit 10.

[0055] In some possible implementations, the NFC antenna circuit 10 also includes a rectifier circuit 15 connected to the second impedance matching circuit 14 and the NFC tag circuit IC.

[0056] The rectifier circuit 15 receives the output voltage of the second impedance matching circuit 14, rectifies it, and transmits it to the NFC tag circuit IC. The NFC tag circuit IC includes a power receiving port VCC2. The rectifier circuit 15 is connected to the output terminal of the second impedance matching circuit 14 and the power receiving port VCC2 of the NFC tag circuit IC, rectifying the output voltage of the second impedance matching circuit 14 and sending it to the power receiving port VCC2. The rectifier circuit 15 includes a plurality of rectifier diodes connected to the output terminal of the second impedance matching circuit 14 to rectify the output voltage of the second impedance matching circuit 14. In some embodiments, the rectifier circuit 15 includes a Schottky diode for converting AC signals to DC signals.

[0057] The rectifier circuit 15 rectifies the signal output from the second impedance matching circuit 14, making it more suitable for powering the NFC tag circuit IC.

[0058] In some possible implementations, the NFC antenna circuit 10 also includes a low-dropout linear regulator circuit LDO1 connected to the rectifier circuit 15 and the NFC tag circuit IC.

[0059] The low-dropout linear regulator (LDO1) circuit suppresses voltage fluctuations, converting an unstable input voltage into a stable output voltage. The output voltage of the rectifier circuit 15 may be unstable. The LDO1 circuit connects the rectifier circuit 15 and the NFC tag circuit IC, converting the unstable voltage output from the rectifier circuit 15 into a stable voltage, which is then supplied to the power receiving port VCC2 of the NFC tag circuit IC, ensuring a stable power supply voltage for the NFC tag circuit IC.

[0060] The low dropout linear regulator circuit LDO1 can convert the unstable voltage output from the rectifier circuit 15 into a more stable voltage, which is then output to the NFC tag circuit IC, thereby providing better power to the NFC tag circuit IC and ensuring that the NFC tag circuit IC works normally.

[0061] The NFC antenna circuit 10 also includes a low-dropout linear regulator (LDO2) circuit, which connects to the rectifier circuit 15 and the controller MCU. The LDO2 circuit connects the output of the rectifier circuit 15 to the power supply port VCC1 of the controller MCU. The LDO2 circuit converts the output voltage of the rectifier circuit 15 and transmits it to the controller MCU, providing a stable power supply voltage for the controller MCU.

[0062] In some possible implementations, the rectifier circuit 15 includes a first input terminal 151 and a second input terminal 152, and the second impedance matching circuit 14 includes a first inductor C211, a second inductor C212, a first capacitor C202, and a ground terminal GND. The first inductor C211 is connected to the first terminal of the second NFC coil 12 and the first input terminal 151, the second inductor C212 is connected to the second terminal of the second NFC coil 12 and the second input terminal 152, the first capacitor C202 is connected in parallel between the first terminal and the second terminal of the second NFC coil 12, and the first capacitor C202 is connected to the ground terminal GND.

[0063] The first inductor C211 and the second inductor C212 are connected between the second NFC coil 12 and the rectifier circuit 15 to compensate for the parasitic capacitance of the second NFC coil 12 and achieve impedance matching. The first capacitor C202 is connected in parallel with the second NFC coil 12 to form a parallel resonant circuit, which is used to increase the impedance of the second NFC coil 12 when coupling with other NFC devices.

[0064] The first inductor C211, the second inductor C212, and the first capacitor C202 match the impedance to the input impedance of the rectifier circuit 15, thereby improving the energy transfer efficiency between the second NFC coil 12 and the rectifier circuit 15.

[0065] The first inductor C211, the second inductor C212, and the first capacitor C202 form an LC parallel resonant matching network, which can improve the energy transfer efficiency between the second NFC coil 12 and other NFC devices.

[0066] In some possible implementations, the second impedance matching circuit 14 includes second capacitors C205 and C206 and third capacitors C207 and C208. The second capacitors C205 and C206 are connected in series with the first inductor C211 between the first terminal and the first input terminal 151 of the second NFC coil 12. The third capacitors C207 and C208 and the second inductor C212 are connected in series between the second terminal and the second input terminal 152 of the second NFC coil 12.

[0067] The second capacitors C205 and C206 are connected in parallel. The third capacitors C207 and C208 are connected in parallel.

[0068] The second capacitors C205 and C206, the third capacitors C207 and C208, and the first inductor C211, the second inductor C212, and the first capacitor C202 form a π-type LC impedance matching network. The π-type LC impedance matching network has more adjustable parameters, can cover a wider impedance range, and has multi-level filtering characteristics, further optimizing impedance matching accuracy and improving energy transmission efficiency, enabling the NFC antenna circuit 10 to obtain more energy from other NFC devices.

[0069] In some possible implementations, the NFC tag circuit 10 includes a third input terminal S1 and a fourth input terminal S2, and the first impedance matching circuit 13 includes a third inductor C101, a fourth inductor C102, a fourth capacitor C106, a fifth capacitor C103, and a ground terminal GND. The third inductor C101 is connected to the first terminal of the first NFC coil 11 and the third input terminal S1, the fourth inductor C102 is connected to the second terminal of the first NFC coil 11 and the fourth input terminal S2, the fourth capacitor C106 is connected in parallel between the first terminal and the second terminal of the first NFC coil 11, the fifth capacitor C103 is connected in parallel between the third input terminal S1 and the fourth input terminal S2, and the fourth capacitor C106 and the fifth capacitor C103 are connected to the ground terminal GND.

[0070] The third inductor C101, the fourth inductor C102, and the first NFC coil 11 form a series resonant structure, which can compensate for the parasitic capacitance of the first NFC coil 11 and adjust the phase characteristics of the impedance. The fourth capacitor C106 is connected in parallel across the first NFC coil 11, forming a parallel resonant circuit with the first NFC coil 11, used to tune the resonant frequency of the first impedance matching circuit 13 to the standard operating frequency of NFC communication. The fifth capacitor C103 is connected in parallel between the third input terminal S1 and the fourth input terminal S2, which can adjust the impedance magnitude of the circuit. By adjusting the third inductor C101, the fourth inductor C102, the fourth capacitor C106, and the fifth capacitor C103, the input impedance of the NFC tag circuit 10 and the equivalent impedance of the first NFC coil 11 can be adjusted to a conjugate matching state.

[0071] The third inductor C101, the fourth inductor C102, the fourth capacitor C106, and the fifth capacitor C103 form an LC parallel resonant network, which can improve the energy transfer efficiency between the first NFC coil 11 and other NFC devices.

[0072] This application also provides a communication device, including: a load circuit and an NFC antenna circuit 10 as described above, wherein the NFC antenna circuit 10 is connected to the load circuit.

[0073] The load circuit is connected to the controller MCU of the NFC antenna circuit 10 and is used to receive control signals from the controller MCU, enabling the controller MCU to control the operation of the load circuit. In some embodiments, the load circuit includes a display circuit, an audio circuit, a charging circuit, etc., and correspondingly, the controller MCU can control the operation of the display circuit, audio circuit, and charging circuit. In some embodiments, the communication device is a mobile phone case, the load circuit is a display circuit, and the mobile phone case includes a display circuit and the NFC antenna circuit 10. When the mobile phone case is close to the mobile phone, the NFC antenna circuit 10 establishes communication with the mobile phone. The mobile phone can power the NFC antenna circuit 10 and send control commands to the NFC tag circuit IC of the NFC antenna circuit 10. The NFC tag circuit IC sends control commands to the controller MCU, and the controller MCU controls the display circuit to display, such as controlling the color and pattern displayed by the display circuit, thereby realizing the control of the color and pattern display of the mobile phone case. In this way, the mobile phone can control the display of the mobile phone case.

Claims

1. An NFC antenna circuit, characterized by include: A first NFC coil and a second NFC coil are used for coupling with other NFC devices, wherein the size of the second NFC coil is larger than the size of the first NFC coil; NFC tag circuitry, used to identify other NFC devices; A first impedance matching circuit connects the first NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to interact with other NFC devices; the tuning frequency of the first impedance matching circuit is the standard operating frequency for NFC communication. The second impedance matching circuit connects the second NFC coil and the NFC tag circuit, enabling the NFC antenna circuit to obtain power from other NFC devices.

2. The NFC antenna circuit according to claim 1, characterized in that, The tuning frequency of the second impedance matching circuit is different from that of the first impedance matching circuit.

3. The NFC antenna circuit of claim 1, wherein, The size of the first NFC coil is less than 3mm × 3mm.

4. The NFC antenna circuit of claim 1, wherein, The NFC antenna circuit also includes a controller, which includes an enable port and a power supply port. The NFC tag circuit includes a signal output port, which is connected to the enable port. The second impedance matching circuit is connected to the power supply port.

5. The NFC antenna circuit of claim 1, wherein, The NFC antenna circuit also includes a rectifier circuit, which connects the second impedance matching circuit and the NFC tag circuit.

6. The NFC antenna circuit of claim 5, wherein, The NFC antenna circuit also includes a low-dropout linear regulator circuit, which is connected to the rectifier circuit and the NFC tag circuit.

7. The NFC antenna circuit of claim 5, wherein, The rectifier circuit includes a first input terminal and a second input terminal. The second impedance matching circuit includes a first inductor, a second inductor, a first capacitor, and a ground terminal. The first inductor is connected to the first terminal of the second NFC coil and the first input terminal. The second inductor is connected to the second terminal of the second NFC coil and the second input terminal. The first capacitor is connected in parallel between the first terminal and the second terminal of the second NFC coil. The first capacitor is connected to the ground terminal.

8. The NFC antenna circuit according to claim 7, characterized in that, The second impedance matching circuit includes a second capacitor and a third capacitor. The second capacitor and the first inductor are connected in series between the first end of the second NFC coil and the first input end. The third capacitor and the second inductor are connected in series between the second end of the second NFC coil and the second input end.

9. The NFC antenna circuit of claim 1, wherein, The NFC tag circuit includes a third input terminal and a fourth input terminal. The first impedance matching circuit includes a third inductor, a fourth inductor, a fourth capacitor, a fifth capacitor, and a ground terminal. The third inductor is connected to the first terminal of the first NFC coil and the third input terminal. The fourth inductor is connected to the second terminal of the first NFC coil and the fourth input terminal. The fourth capacitor is connected in parallel between the first terminal and the second terminal of the first NFC coil. The fifth capacitor is connected in parallel between the third input terminal and the fourth input terminal. The fourth capacitor and the fifth capacitor are connected to the ground terminal.

10. A communication device, characterized by include: Load circuit; and The NFC antenna circuit as described in any one of claims 1-9 is connected to the load circuit.

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