Nfc radio antenna circuit and terminal device

Abstract

The utility model provides a kind of NFC radio frequency antenna circuit and terminal equipment, it is related to wireless communication technical field.The NFC radio frequency antenna circuit includes antenna module, NFC chip module and matching circuit module, the matching circuit module is used to adjust the impedance between the NFC chip module to the antenna module and the output resistance of the NFC chip module is matched;The matching circuit module includes wideband radio frequency transformer, and the wideband radio frequency transformer is connected with the antenna module by specified type impedance line.So, the performance of NFC radio frequency antenna circuit can be improved.

Description

Technical Field

[0001] The embodiments described in this specification relate to the field of wireless communication technology, specifically to an NFC radio frequency antenna circuit and a terminal device. Background Technology

[0002] Near-Field Communication (NFC), also known as short-range wireless communication, is an electromagnetic coupling induction technology with an electromagnetic field frequency of 13.56MHz. The transmitting device excites the antenna to generate a magnetic field, and transfers energy to the target device through near-field coupling, thereby enabling short-range wireless connections and realizing interactive communication between electronic devices.

[0003] Currently, the transmission distance, or reading and sensing distance, of transmitting devices typically ranges from 10mm to 50mm, depending on factors such as the type of card / target device, the performance of the NFC chip, and the medium used in the transmission process. In the antenna circuit of the transmitting device, the NFC hardware circuit and the antenna need to be very close to each other to prevent interference with the radio frequency antenna or increased link loss. Therefore, the performance of the antenna circuit needs improvement. Utility Model Content

[0004] In view of this, various embodiments of this specification are intended to provide an NFC radio frequency antenna circuit and terminal device to improve the performance of the antenna circuit.

[0005] This specification provides an NFC radio frequency antenna circuit, which includes an antenna module, an NFC chip module, and a matching circuit module. The matching circuit module is used to adjust the impedance between the NFC chip module and the antenna module to match the output resistance of the NFC chip module. The matching circuit module includes a broadband radio frequency transformer for adjusting the impedance between the matching circuit module and the antenna module, and the broadband radio frequency transformer is connected to the antenna module through a specified type of impedance line.

[0006] In some implementations, the specified type of impedance line includes radio frequency coaxial cable or twisted pair cable.

[0007] In some embodiments, the NFC radio frequency antenna circuit further includes an EMC filtering module for filtering out high-order harmonics of the signal transmitted by the NFC chip module and reducing electromagnetic interference.

[0008] In some embodiments, the EMC filtering module includes a first inductor, a second inductor, a first capacitor, and a second capacitor; wherein, the first end of the first inductor is connected to the second interface of the NFC chip module, the first end of the second inductor is connected to the first interface of the NFC chip module, the second end of the first inductor, the first capacitor, the second capacitor, and the second end of the second inductor are connected in series, and the first capacitor and the second capacitor are connected to a ground terminal; the second end of the first inductor and the first capacitor are connected to the third interface and the reference voltage interface of the NFC chip module through a thirteenth capacitor and a resistor.

[0009] In some embodiments, the matching circuit module further includes a first matching circuit module, a second matching circuit module, a third matching circuit module, a first matching resistor, and a second matching resistor; wherein the first matching circuit module includes a third capacitor and a fourth capacitor connected in parallel, the second matching circuit module includes a sixth capacitor and a fifth capacitor connected in parallel; the third matching circuit module includes multiple capacitor branches connected in parallel, each capacitor branch being connected to the ground terminal; wherein the first terminal of the first matching circuit module is connected between the second terminal of the first inductor and the first capacitor; the first terminal of the second matching circuit module is connected between the second terminal of the second inductor and the second capacitor; the second terminals of the first matching circuit module, the third matching circuit module, and the second terminal of the second matching circuit module are connected in series; the second terminal of the first matching circuit module and the third matching circuit module are connected to the first terminal of the first matching resistor; the second terminal of the second matching circuit module and the third matching circuit module are connected to the first terminal of the second matching resistor.

[0010] In some implementations, the second terminal of the first matching circuit module and the third matching circuit module are connected to the third interface and the reference voltage interface of the NFC chip module through the fourteenth capacitor and the first resistor.

[0011] In some embodiments, the second end of the first matching resistor is connected to the first end of the primary coil in the broadband RF transformer; the second end of the primary coil in the broadband RF transformer is connected to the positive terminal of the antenna through the specified type of impedance line; the second end of the second matching resistor is connected to the first end of the secondary coil in the broadband RF transformer; and the second end of the secondary coil in the broadband RF transformer is connected to the negative terminal of the antenna through the specified type of impedance line.

[0012] In some implementations, the number of parallel capacitor branches in the third module of the matching circuit is at least three.

[0013] In some embodiments, two ESD protection diodes are connected in series between the second end of the first matching resistor and the second end of the second matching resistor; the two ESD protection diodes are connected to the ground terminal.

[0014] This specification provides a terminal device, which includes the NFC radio frequency antenna circuit provided in any of the above embodiments.

[0015] The various embodiments provided in this specification include an NFC radio frequency antenna circuit comprising an antenna module, an NFC chip module, and a matching circuit module. The matching circuit module is used to adjust the impedance between the NFC chip module and the antenna module to match the output resistance of the NFC chip module. The matching circuit module includes a broadband radio frequency transformer, which is connected to the antenna module through a specified type of impedance line. This can improve the performance of the NFC radio frequency antenna circuit. Attached Figure Description

[0016] Figure 1 A schematic diagram of the matching circuit module provided for the embodiments of this specification; Figure 2a A circuit diagram of the NFC radio frequency antenna circuit provided for the embodiments of this specification; Figure 2b A circuit diagram of the NFC radio frequency antenna circuit provided for the embodiments of this specification; The labels in the attached figures are explained as follows: L0401, First Inductor; L0402, Second Inductor; C0418, First Capacitor; C0408, Second Capacitor; C0420, Third Capacitor; C0402, Fourth Capacitor; C0415, Fifth Capacitor; C0401, Sixth Capacitor; C0403, Seventh Capacitor; C0405, Eighth Capacitor; C0411, Ninth Capacitor; C0422, Tenth Capacitor; C0421, Eleventh Capacitor; C0407, Twelfth Capacitor; C0423, Thirteenth Capacitor; C0412, Fourteenth Capacitor; R0405, first resistor; R0402, first matching resistor; R0401, second matching resistor; D0401, first ESD protection diode; D0402, second ESD protection diode; NFC_GND-, Ground terminal; TX1-, First interface; TX2, Second interface; PRR, Primary coil; SEC, Secondary coil; VMID, Reference voltage interface; RX, Third interface; T0401, Broadband RF transformer; NFC_ANT-, Antenna negative terminal; NFC_ANT+, Antenna positive terminal. Detailed Implementation

[0017] To enable those skilled in the art to better understand the solutions described in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0018] In related technologies, the NFC hardware circuitry and antenna in the transmitting device often need to be positioned close together to prevent interference with the radio frequency antenna or increased link loss. This means that the hardware circuitry and antenna in the transmitting device need to be bundled together in the same environment. If the NFC hardware circuitry also includes other power supplies, peripherals, and other circuits, then higher requirements are placed on the actual overall installation location or space of the final product or terminal device.

[0019] This specification provides an NFC radio frequency antenna circuit, which includes an antenna module, an NFC chip module, and a matching circuit module. The matching circuit module is used to adjust the impedance between the NFC chip module and the antenna module to match the output resistance of the NFC chip module. Please refer to [link to documentation]. Figure 1 The matching circuit module includes a broadband RF transformer, which is connected to the antenna module via a specified type of impedance line. Exemplarily, the broadband RF transformer in the matching circuit module, i.e., the RF antenna matching circuit, can adjust the impedance between the matching circuit module and the antenna module to match the output impedance of the NFC chip module.

[0020] The broadband RF transformer has an impedance ratio of 1:1 and supports a passband within a specified range with a center frequency of 13.56MHz. This enables 1:1 antenna conversion while minimizing circuit losses; testing shows its losses are less than 1dB. Specified impedance wire types can include dedicated impedance wires of selectable lengths, RF coaxial cables, or twisted-pair cables. This reduces the impact of impedance wire length on antenna performance while increasing the spatial flexibility of the NFC antenna, thereby improving the feasibility and applicability of practical applications.

[0021] The matching circuit module can adjust the antenna resonant point to 13.56MHz, while simultaneously adjusting the antenna circuit impedance to near the chip's output resistance. The broadband RF transformer enables the matching circuit module to achieve a balun effect, converting unstable or mismatched signals from the external antenna into stable, matched signals fed back to the NFC chip module, thus ensuring stable card reading. The transmission length between the broadband RF transformer and the antenna module can be selected and matched according to actual needs. This allows for increasing the transmission distance between the antenna in the transmitting device and the NFC hardware circuitry without affecting the sensing distance between the transmitting and target devices, achieving an external NFC independent antenna without compromising antenna circuit performance.

[0022] In some implementations, the NFC radio frequency antenna circuit may also include an EMC filtering module for filtering out high-order harmonics of the NFC chip module's transmitted signal and reducing electromagnetic interference.

[0023] Specifically, please refer to Figure 2a and Figure 2b In the NFC radio frequency antenna circuit, the EMC filtering module may include a first inductor L0401, a second inductor L0402, a first capacitor C0418, and a second capacitor C0408.

[0024] The first end of the first inductor L0401 is connected to the second interface TX2 of the NFC chip module, and the first end of the second inductor L0402 is connected to the first interface TX1 of the NFC chip module. The second end of the first inductor L0401, the first capacitor C0418, the second capacitor C0408, and the second end of the second inductor L0402 are connected in series. The first capacitor C0418 and the second capacitor C0408 are connected to the ground terminal NFC_GND.

[0025] In this configuration, the second terminal of the first inductor L0401 is connected to the first capacitor C0418 via the thirteenth capacitor C0423 and the first resistor R0405, and is then connected to the third interface RX and the reference voltage interface VMID of the NFC chip module. For example, the connection between the second terminal of the first inductor L0401 and the first capacitor C0418 forms an output terminal of the EMC filter module, denoted as TX2_0. The output terminal TX2_0, the thirteenth capacitor C0423, and the first resistor R0405 are connected in series.

[0026] In some implementations, please refer to [the relevant documentation]. Figure 2a and Figure 2b The matching circuit module may also include a first matching circuit module, a second matching circuit module, a third matching circuit module, a second matching resistor R0401, and a first matching resistor R0402.

[0027] The matching circuit first module may include a third capacitor C0420 and a fourth capacitor C0402 connected in parallel. The matching circuit second module may include a sixth capacitor C0401 and a fifth capacitor C0415 connected in parallel. The matching circuit third module may include multiple capacitor branches connected in parallel, each capacitor branch consisting of two capacitors connected in series, and the two capacitors in each capacitor branch are connected to the ground terminal NFC_GND.

[0028] In this circuit, the first terminal of the first matching circuit module is connected between the second terminal of the first inductor L0401 and the first capacitor C0418. The first terminal of the second matching circuit module is connected between the second terminal of the second inductor L0402 and the second capacitor C0408. The second terminals of the first matching circuit module, the third matching circuit module, and the second matching circuit module are connected in series. For example, the connection between the second terminal of the second inductor L0402 and the second capacitor C0408 forms another output terminal of the EMC filter module, denoted as TX1_0. The first terminal of the first matching circuit module is connected to output terminal TX2_0, and the first terminal of the second matching circuit module is connected to output terminal TX1_0.

[0029] The second terminal of the first matching circuit module and the third matching circuit module are connected to the first terminal of the first matching resistor R0402; the second terminal of the second matching circuit module and the third matching circuit module are connected to the first terminal of the second matching resistor R0401. For example, the second terminal of the first matching circuit module is denoted as output terminal TX2_1, and the second terminal of the second matching circuit module is denoted as TX1_1.

[0030] In some implementations, the second terminal of the first matching circuit module and the third matching circuit module are connected to the third interface RX and the reference voltage interface VMID of the NFC chip module through the fourteenth capacitor C0412 and the first resistor R0405.

[0031] In some implementations, the second end of the first matching resistor R0402 is connected to the first end of the primary coil PRR in the broadband RF transformer T0401; the second end of the primary coil PRR in the broadband RF transformer T0401 is connected to the positive terminal of the antenna NFC_ANT+ through a specified type impedance line.

[0032] The second terminal of the second matching resistor R0401 is connected to the first terminal of the secondary coil SEC in the broadband RF transformer T0401; the second terminal of the secondary coil SEC in the broadband RF transformer T0401 is connected to the negative terminal of the antenna NFC_ANT- through a specified type impedance line.

[0033] In some implementations, please refer to [the relevant documentation]. Figure 2a and Figure 2bThe number of parallel capacitor branches in the third module of the matching circuit is at least three. For example, one capacitor branch includes the seventh capacitor C0403 and the eighth capacitor C0405, another capacitor branch includes the ninth capacitor C0411 and the tenth capacitor C0422, and yet another capacitor branch includes the eleventh capacitor C0421 and the twelfth capacitor C0407.

[0034] In some embodiments, two ESD protection diodes, namely the first ESD protection diode D0401 and the second ESD protection diode D0402, are connected in series between the second terminal of the first matching resistor R0402 and the second terminal of the second matching resistor R0401. The first ESD protection diode D0401 and the second ESD protection diode D0402 are connected to the ground terminal.

[0035] This specification provides a terminal device, which includes the NFC radio frequency antenna circuit described in any of the above embodiments.

[0036] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments described herein, and are not intended to limit the scope of this utility model.

[0037] It is understood that the various implementation methods described in this specification can be implemented individually or in combination, and the implementation methods in this specification are not limited in this respect.

[0038] Unless otherwise stated, all technical and scientific terms used in the embodiments of this specification have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this specification. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0039] The above description is merely a specific embodiment of this specification, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this specification should be included within the protection scope of this specification. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. An NFC radio frequency antenna circuit, characterized in that, The NFC radio frequency antenna circuit includes an antenna module, an NFC chip module, and a matching circuit module. The matching circuit module is used to adjust the impedance between the NFC chip module and the antenna module to match the output resistance of the NFC chip module. The matching circuit module includes a broadband radio frequency transformer for adjusting the impedance between the matching circuit module and the antenna module, and the broadband radio frequency transformer is connected to the antenna module through a specified type of impedance line.

2. The NFC radio frequency antenna circuit according to claim 1, characterized in that, The specified type of impedance line includes radio frequency coaxial cable or twisted pair cable.

3. The NFC radio frequency antenna circuit according to claim 1, characterized in that, The NFC radio frequency antenna circuit also includes an EMC filtering module, which is used to filter out high-order harmonics of the signal transmitted by the NFC chip module and reduce electromagnetic interference.

4. The NFC radio frequency antenna circuit according to claim 3, characterized in that, The EMC filtering module includes a first inductor, a second inductor, a first capacitor, and a second capacitor; Wherein, the first end of the first inductor is connected to the second interface of the NFC chip module, the first end of the second inductor is connected to the first interface of the NFC chip module, the second end of the first inductor, the first capacitor, the second capacitor and the second end of the second inductor are connected in series, and the first capacitor and the second capacitor are connected to the ground terminal. The second terminal of the first inductor is connected to the first capacitor via a thirteenth capacitor and a resistor, and is then connected to the third interface and reference voltage interface of the NFC chip module.

5. The NFC radio frequency antenna circuit according to claim 4, characterized in that, The matching circuit module further includes a first matching circuit module, a second matching circuit module, a third matching circuit module, a first matching resistor, and a second matching resistor; The first matching circuit module includes a third capacitor and a fourth capacitor connected in parallel; the second matching circuit module includes a sixth capacitor and a fifth capacitor connected in parallel; and the third matching circuit module includes multiple capacitor branches connected in parallel, each capacitor branch being connected to the ground terminal. Wherein, the first end of the first matching circuit module is connected between the second end of the first inductor and the first capacitor; the first end of the second matching circuit module is connected between the second end of the second inductor and the second capacitor; the second ends of the first matching circuit module, the third matching circuit module, and the second end of the second matching circuit module are connected in series. The second terminal of the first matching circuit module and the third matching circuit module are connected to the first terminal of the first matching resistor; the second terminal of the second matching circuit module and the third matching circuit module are connected to the first terminal of the second matching resistor.

6. The NFC radio frequency antenna circuit according to claim 5, characterized in that, The second terminal of the first matching circuit module and the third matching circuit module are connected to the third interface and the reference voltage interface of the NFC chip module through the fourteenth capacitor and the first resistor.

7. The NFC radio frequency antenna circuit according to claim 5, characterized in that, The second end of the first matching resistor is connected to the first end of the primary coil in the broadband radio frequency transformer; the second end of the primary coil in the broadband radio frequency transformer is connected to the positive terminal of the antenna through the specified type of impedance line. The second end of the second matching resistor is connected to the first end of the secondary coil in the broadband radio frequency transformer; the second end of the secondary coil in the broadband radio frequency transformer is connected to the negative terminal of the antenna through the specified type of impedance line.

8. The NFC radio frequency antenna circuit according to claim 5, characterized in that, The number of parallel capacitor branches in the third module of the matching circuit is at least three.

9. The NFC radio frequency antenna circuit according to claim 5, characterized in that, Two ESD protection diodes are connected in series between the second end of the first matching resistor and the second end of the second matching resistor; the two ESD protection diodes are connected to the ground terminal.

10. A terminal device, characterized in that, The terminal device includes the NFC radio frequency antenna circuit according to any one of claims 1 to 9.

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