Novel nfc wideband filter circuit and electronic device
The novel NFC wideband filter circuit, which uses a filter circuit composed of feedthrough beads and BDL differential common-mode filters, solves the problems of narrow frequency band and poor noise suppression of traditional filter circuits, and achieves the effects of wideband filtering and miniaturization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN TOP FLIGHT TECH CO LTD
- Filing Date
- 2025-07-16
- Publication Date
- 2026-08-04
AI Technical Summary
Traditional NFC filtering circuits have a single filtering effect, a narrow frequency band, and are difficult to achieve wideband filtering. They also have poor noise suppression, occupy a lot of PCB space, and cannot meet electromagnetic compatibility standards.
A novel NFC wideband filter circuit is constructed using a first through-bead, a second through-bead, and a BDL differential common-mode filter. The through-bead provides differential-mode filtering, while the BDL differential common-mode filter provides common-mode filtering, forming a Faraday cage structure to suppress common-mode noise and differential-mode conversion.
It achieves a wideband filtering effect of 30MHz-1GHz, suppresses clock noise and data noise radiation, reduces PCB space occupation, reduces electromagnetic radiation interference, and improves the miniaturization potential of products and the pass rate of electromagnetic compatibility tests.
Smart Images
Figure CN224596456U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electromagnetic emission technology in electromagnetic compatibility, and more specifically, to a novel NFC wideband filter circuit. Background Technology
[0002] NFC itself is a radio wave transmission near an electromagnetic field, which requires the corresponding induction coil to transmit the corresponding communication frequency. If the filtering process at the signal transmitting end is not adequate, other radiation interference will be radiated out through the induction coil, causing it to fail to meet the corresponding electromagnetic compatibility standards.
[0003] Traditional NFC filtering circuits have a relatively simple filtering effect, typically using a combination of inductor L and multiple capacitors C for filtering, such as... Figure 5 Four capacitors C are used for filtering. The balance between multiple capacitors is poor, which can easily lead to changes in noise pattern. At the same time, they occupy a lot of PCB space. The combined LC filter has a narrow frequency band, mainly concentrated in 200MHz, and cannot achieve wideband filtering coverage. In particular, the noise suppression effect at the 13.56MHz clock is poor. Utility Model Content
[0004] The technical problem to be solved by this invention is how to solve the radiation emission problem on the NFC data sensing coil, simplify the filtering circuit, and provide a new NFC broadband filtering circuit to address the above-mentioned defects of the prior art.
[0005] The technical solution adopted by this utility model to solve its technical problem is: on the one hand A novel NFC wideband filtering circuit includes a first feedthrough bead, a second feedthrough bead, and a BDL differential common-mode filter. The first end of the first through-hole magnetic bead is used to receive the first differential signal, and the second end is used to output the first differential signal after preliminary filtering. The first end of the second through-hole magnetic bead is used to receive the second differential signal, and the second end is used to output the second differential signal after preliminary filtering. The second ends of the first through-bead and the second through-bead are both connected to the first end of the BDL differential common-mode filter, and the second end of the BDL differential common-mode filter is grounded; the BDL differential common-mode filter is used to suppress common-mode noise and perform differential-mode conversion.
[0006] Preferably, both the first and second through-hole magnetic beads are conductive wires coated with nickel-zinc ferrite.
[0007] Preferably, the BDL differential common-mode filter includes two balanced and symmetrical differential signal input terminals and two parallel reference electrodes G1 and G2, wherein the reference electrodes G1 and G2 form a Faraday cage structure.
[0008] on the other hand An electronic device includes any one of the novel NFC broadband filtering circuits described above. The electronic device uses the common-mode filtering circuit to suppress common-mode noise during signal transmission, ensuring internal signal communication quality and reducing external electromagnetic radiation interference.
[0009] Preferably, the electronic device is a computer, communication equipment, or consumer electronic terminal, and the common-mode filter circuit is integrated into the signal interface module or power module of the electronic device.
[0010] The beneficial effects of this utility model are as follows: 1. Suppress clock and data noise radiated from the NFC data transmitter via the antenna. Only three filtering components are needed, with filtering effects covering 30MHz-1GHz, enabling products to pass corresponding EMC (electromagnetic compatibility) tests more effectively.
[0011] 2. Primarily used in NFC data transmission port filtering circuits, this design enhances the filtering effect against differential and common-mode noise. The feedthrough bead R provides differential-mode filtering, while the BDL differential-common-mode filter provides common-mode filtering. This circuit design offers unique filtering advantages, providing strong differential-mode filtering while suppressing differential-to-common-mode conversion and increasing common-mode filtering. Most importantly, it saves PCB space, making product miniaturization more advantageous.
[0012] 3. Compared to the two filter capacitors in traditional circuits, a single BDL differential-common-mode filter reduces the conversion of differential-mode noise into common-mode noise caused by errors in the parameters of the two capacitors, thereby reducing differential-to-common-mode conversion. Simultaneously, due to the balanced characteristics of the BDL differential-to-common-mode filter, it enhances the filtering effect of common-mode noise. One device replaces multiple capacitors, reducing circuit cost and PCB board space. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is an overall circuit diagram of the novel NFC wideband filter circuit according to an embodiment of this application.
[0014] Figure 2This is a physical image of the nickel-zinc ferrite through-hole magnetic beads according to an embodiment of this application.
[0015] Figure 3 This is a physical diagram of the BDL differential common-mode filter according to an embodiment of this application.
[0016] Figure 4 These are EMI test data for the filter circuit in the embodiments of this application.
[0017] Figure 5 This is a circuit diagram of an existing filter circuit in the background art.
[0018] Figure 6 These are EMI test data for traditional filter circuits. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of this utility model. Obviously, the described embodiments are some, but not all, of the embodiments of this utility model. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0020] The preferred embodiment of this utility model is as follows: Figure 1-4 As shown, a novel NFC wideband filter circuit includes a first feedthrough bead R1, a second feedthrough bead R2, and a BDL differential common-mode filter C11.
[0021] The first terminal of the first through-bead R1 is used to receive the first differential signal TX1, and the second terminal is used to output the first differential signal X1 after preliminary filtering. The first terminal of the second through-bead R2 is used to receive the second differential signal TX2, and the second terminal is used to output the second differential signal RTX2 after preliminary filtering. The second terminals of both the first and second through-beads R1 and R2 are connected to the first terminal of the BDL differential-common-mode filter C11, and the second terminal of the BDL differential-common-mode filter C11 is grounded to GND. The BDL differential-common-mode filter is used to suppress common-mode noise and perform differential-common-mode conversion. As a common reference ground GND, it forms a noise discharge path with the BDL differential-common-mode filter C11.
[0022] The first differential signal TX1 and the second differential signal TX2 are a pair of differential signals. During normal transmission, they have opposite phases and equal amplitudes, while the common-mode noise signal has the same phase. The first through-bead R1 and the second through-bead R2 present low impedance to the differential signal to ensure normal transmission, and high impedance to the common-mode noise signal to hinder its propagation. The BDL differential-common-mode filter C11 is used to bypass the common-mode noise signal to ground to filter out residual common-mode interference.
[0023] Differential signals are high-speed data signals or differential power signals. Common-mode filtering circuits are used for high-speed signal interfaces or power filtering scenarios, including but not limited to signal filtering for USB interfaces and HDMI interfaces.
[0024] As an optional embodiment, both the first through-bead R1 and the second through-bead R2 can be selected as nickel-zinc ferrite through-beads. Through-beads with high impedance can be selected to suppress noise in the 10MHz-500MHz frequency band. Nickel-zinc ferrite through-beads enhance the effect of differential mode filtering while reducing the impact on signal integrity, greatly reducing the noise radiation of the circuit to the outside world, and enhancing the stability of the circuit operation.
[0025] The BDL differential-common mode filter includes two balanced and symmetrical differential signal input terminals and two parallel reference electrodes G1 and G2, which form a Faraday cage structure. Its main purpose is to filter the common-mode noise of the clock mixed in with the data from the NFC chip data traces, while reducing the conversion between differential and common modes.
[0026] Suppresses clock and data noise radiated from the NFC data transmitter via the antenna. Only three filtering components are needed, with filtering effects covering 30MHz-1GHz, enabling products to pass corresponding EMC (electromagnetic compatibility) tests more effectively.
[0027] Primarily used in NFC data transmission port filtering circuits, this design enhances the filtering effect against differential and common-mode noise. The feedthrough bead R provides differential-mode filtering, while the BDL differential-common-mode filter provides common-mode filtering. This circuit design offers unique filtering advantages, providing strong differential-mode filtering while suppressing differential-to-common-mode conversion and increasing common-mode filtering. Most importantly, it saves PCB space, making it more advantageous for product miniaturization.
[0028] This application suppresses clock noise and data noise radiated from the NFC data transmitter via the antenna. Only three filtering components are needed, and the filtering effect covers 30MHz-1GHz, enabling the product to pass the corresponding EMC (electromagnetic compatibility) tests more effectively.
[0029] Primarily used in NFC data transmission port filtering circuits, this design enhances the filtering effect on differential and common-mode noise. The feedthrough bead R provides differential-mode filtering, while the BDL differential-common-mode filter C11 provides common-mode filtering. This circuit design offers unique filtering advantages, providing strong differential-mode filtering while suppressing differential-to-common-mode conversion and increasing common-mode filtering. Most importantly, it saves PCB space, making it more advantageous for product miniaturization.
[0030] Compared to the two filter capacitors in traditional circuits, a single BDL differential-common-mode filter C11 reduces the conversion of differential-mode noise to common-mode noise caused by parameter errors in the two capacitors, thus reducing differential-to-common-mode conversion. Simultaneously, the balanced characteristics of the BDL differential-to-common-mode filter C11 enhance the common-mode noise filtering effect of the circuit. One component replaces multiple capacitors, reducing circuit cost and PCB space. The circuit achieves full-band noise suppression from 30MHz to 1GHz through the synergistic mechanism of differential-mode filtering by the first feedthrough bead R1 and the second feedthrough bead R2, and common-mode filtering by the BDL filter, reducing the number of components from four or more to three. When applied between the NFC data transmitter and the induction coil, the circuit suppresses radiated noise from the 13.56MHz clock and data signals, resulting in a lower noise peak in EMI testing compared to traditional circuits.
[0031] The first through-bead R1 and the second through-bead R2 suppress high-frequency noise in the 10MHz-500MHz frequency band through the frequency impedance characteristics of the magnetic materials, and reduce the impact on signal integrity through the single-wire structure. The first through-bead R1 and the second through-bead R2 form a signal path. By selecting high-impedance beads in the 10MHz-500MHz frequency band, wideband suppression of differential-mode noise is achieved. In addition, the first through-bead R1 and the second through-bead R2 have small parasitic inductance, which reduces the attenuation of useful signals.
[0032] The BDL differential common-mode filter C11 is connected between RTX1, RTX2 and ground GND. The filter suppresses common-mode noise and differential common-mode conversion in the 35MHz-1000MHz frequency band through a Faraday cage structure or a coaxial line structure. Its parasitic parameters ESR and RSL are lower than those of traditional capacitor combinations.
[0033] Example 2 An electronic device includes any of the novel NFC broadband filter capacitors described in Embodiment 1. The electronic device suppresses common-mode noise during signal transmission through a common-mode filter circuit, ensuring internal signal communication quality and reducing external electromagnetic radiation interference. The electronic device can be a computer, communication equipment, or a consumer electronics terminal. The common-mode filter circuit is integrated into the signal interface module or power supply module of the electronic device.
[0034] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A novel NFC wideband filtering circuit characterized in that, Includes a first through-hole magnetic bead, a second through-hole magnetic bead, and a BDL differential common-mode filter; The first end of the first through-hole magnetic bead is used to receive the first differential signal, and the second end is used to output the first differential signal after preliminary filtering. The first end of the second through-hole magnetic bead is used to receive the second differential signal, and the second end is used to output the second differential signal after preliminary filtering. The second ends of the first through-bead and the second through-bead are both connected to the first end of the BDL differential common-mode filter, and the second end of the BDL differential common-mode filter is grounded; the BDL differential common-mode filter is used to suppress common-mode noise and perform differential-common-mode conversion.
2. A novel NFC wideband filtering circuit according to claim 1, characterized in that, Both the first and second through-hole magnetic beads are wire-coated nickel-zinc ferrite structures.
3. A novel NFC wideband filtering circuit according to claim 1, characterized in that, The BDL differential common-mode filter includes two balanced and symmetrical differential signal input terminals and two parallel reference electrodes G1 and G2, which form a Faraday cage structure.
4. An electronic device, comprising: The electronic device is provided with a novel NFC wideband filtering circuit comprising any one of claims 1-3, and the electronic device suppresses common-mode noise during signal transmission through the novel NFC wideband filtering circuit.
5. The electronic device of claim 4, wherein, The electronic device is a computer, communication equipment, or consumer electronic terminal, and the novel NFC wideband filtering circuit is integrated into the signal interface or power module of the electronic device.