Radio frequency harmonic rejection circuit and electronic device

Abstract

The application discloses a radio frequency harmonic filtering circuit and electronic equipment, and relates to the technical field of radio frequency harmonic filtering circuits, and aims to provide a radio frequency harmonic filtering circuit and electronic equipment.

Description

Technical Field

[0001] This application relates to the field of electronic circuits, specifically to radio frequency harmonic filtering circuits and electronic devices. Background Technology

[0002] Electronic terminal products must pass certification testing before they can be sold on the market. During the certification testing process, it must be ensured that the power of spurious signals of the terminal product does not exceed the specified limits. Currently, some terminal products have a technical problem: the second harmonic generated by their 2.4G radio frequency signal leaks through the 5G radio frequency signal port, and the leakage power is relatively large. These leaked harmonic signals are then radiated into the external environment through the 5G radio frequency signal antenna, ultimately causing the radiated spurious index to exceed the standard range.

[0003] Several solutions have been proposed to address this technical problem, but all have certain limitations. One approach is to add an SPDT (Single Pole Double Throw) switch or filter to the 5G RF signal path. However, using an SPDT switch increases the insertion loss of the 5G RF signal path, while filters, although they can suppress insertion loss to some extent, introduce significant in-band insertion loss (signal attenuation during transmission) and also increase design costs. Another solution is to reduce the antenna gain of the 5G RF signal antenna at the 2.4 GHz harmonic frequency, but this method requires debugging under fixed terminal antenna conditions, making implementation difficult. Utility Model Content

[0004] To address the aforementioned issues, this application provides a radio frequency harmonic filtering circuit and electronic device, which enables the filtering of radio frequency harmonics under low-cost conditions.

[0005] One technical solution adopted in this application is: providing a radio frequency harmonic filtering circuit, the radio frequency harmonic filtering circuit including: a filter stub line, the first end of the filter stub line being coupled to a 5G radio frequency signal transmission line; a zero-ohm resistor, the first end of the zero-ohm resistor being coupled to a first position of the filter stub line, and the second end of the zero-ohm resistor being grounded; wherein, the distance between the first position of the filter stub line and the first end of the filter stub line is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal.

[0006] In one embodiment, the radio frequency harmonic filtering circuit further includes a filter element, the first end of which is coupled to a 5G radio frequency signal transmission line, and the second end of which is grounded.

[0007] In one embodiment, the filtering element is a capacitor or an inductor.

[0008] In one embodiment, when the width of the filter stub line is 0.09 mm and the distance between the first position of the filter stub line and the first end of the filter stub line is 19.1 mm, 19.1 mm is within a preset range of half the wavelength of the second harmonic of the 2.4G radio frequency signal.

[0009] In one embodiment, when the width of the filter stub line is 0.09 mm and the distance between the first position of the filter stub line and the first end of the filter stub line is 38.4 mm, 38.4 mm is within a preset range of twice the wavelength of half the second harmonic of the 2.4G radio frequency signal.

[0010] In one embodiment, when the width of the filter spur line is 0.09 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 57.5 mm, 57.5 mm is within a preset range of three times the half wavelength of the second harmonic of the 2.4G radio frequency signal.

[0011] In one embodiment, when the width of the filter spur line is 0.06 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 39.5 mm, 39.5 mm is within a preset range of twice the wavelength of half the second harmonic of the 2.4G radio frequency signal.

[0012] In one embodiment, when the width of the filter spur line is 0.06 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 58.8 mm, 58.8 mm is within a preset range of three times the half wavelength of the second harmonic of the 2.4G radio frequency signal.

[0013] In one embodiment, the distance between the first position of the filter branch line and the first end of the filter branch line is determined by the following formula:

[0014]

[0015] Where L represents the distance between the first position of the filter stub and the first end of the filter stub, n represents a positive integer, c represents the speed of light in a vacuum, f represents the frequency of the 2.4G radio frequency signal, and ε represents the dielectric constant of the filter stub.

[0016] This application also provides an electronic device that includes the radio frequency harmonic filtering circuit described above.

[0017] One technical solution adopted in this application is to provide a radio frequency (RF) harmonic filtering circuit, which includes: a filter stub line, the first end of which is coupled to a 5G RF signal transmission line; a zero-ohm resistor, the first end of which is coupled to a first position of the filter stub line, and the second end of which is grounded; wherein the distance between the first position of the filter stub line and the first end of the filter stub line is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G RF signal. By means of the above method, a filter stub line conforming to an integer multiple of half the wavelength of the second harmonic of the 2.4G RF signal is coupled to the 5G RF signal transmission line, and the filter stub line is grounded, thereby filtering out the second harmonic of the 2.4G RF signal using the filter stub line without affecting the transmission of the 5G RF signal. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] in:

[0020] Figure 1 This is a schematic diagram of the structure of the first embodiment of the radio frequency harmonic filtering circuit provided in this application;

[0021] Figure 2 This is a schematic diagram of the first frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0022] Figure 3 This is a schematic diagram of the second frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0023] Figure 4 This is a schematic diagram of the third frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0024] Figure 5 This is a schematic diagram of the structure of the second embodiment of the radio frequency harmonic filtering circuit provided in this application;

[0025] Figure 6 This is a schematic diagram of the fourth frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0026] Figure 7 This is a schematic diagram of the fifth frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0027] Figure 8 This is a schematic diagram of the sixth frequency response curve of the radio frequency harmonic filtering circuit provided in this application;

[0028] Figure 9 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0030] The terms "first," "second," etc., used in this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] Near-end spurious signals refer to spurious interference signals generated near the local oscillator signal (i.e., within the short distance range of the signal transmission line). For example, the second harmonic signal (spurious interference signal) of the 2.4G radio frequency signal generated on the 5G radio frequency signal (local oscillator signal) transmission line.

[0033] To effectively address near-end spurious emissions, an SPDT (Single Pole Double Throw) switch can be introduced into the 5G RF signal path. Specifically, when the 2.4G RF signal is transmitting, the SPDT switch is turned off to block the transmission path of the 5G RF signal, thereby interrupting the harmonic transmission path of the 2.4G RF signal and effectively mitigating excessive spurious emissions. However, this solution introduces additional insertion loss into the 5G RF signal path and depends on platform support for the SPDT switch function; some platforms may not have this feature. Furthermore, adding RF switching devices will correspondingly increase costs.

[0034] Another solution is to add a filter to the 5G RF signal path to ensure the smooth passage of the 5G RF signal while attenuating the second harmonic of the 2.4G RF signal by more than 10dB. However, designing such a filter is quite challenging given that the second harmonic frequency of the 2.4G RF signal is very close to that of the 5G RF signal. Currently available products are either expensive or have significant in-band insertion loss.

[0035] Alternatively, the problem can be solved by reducing the antenna gain of the 5G RF signal antenna at the 2.4G RF signal harmonic frequency. This requires fine-tuning the antenna's directivity to reduce the gain at spurious frequencies while ensuring that the efficiency at the useful signal frequency is not affected. However, this adjustment process is relatively complex and difficult when the terminal antenna environment is fixed.

[0036] This application provides a radio frequency harmonic filtering circuit 100. This solution can minimize the introduction of additional 5G radio frequency signal path insertion loss while controlling costs, ensuring that the stable transmission of 5G radio frequency signals is not affected, and effectively filtering out the second harmonic interference generated by 2.4G radio frequency signals.

[0037] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the radio frequency harmonic filtering circuit provided in this application. The radio frequency harmonic filtering circuit 100 includes: a filter stub line 10 and a zero-ohm resistor 20.

[0038] The first end of the filter branch line 10 is coupled to the 5G radio frequency signal transmission line; the first end of the zero-ohm resistor 20 is coupled to the first position of the filter branch line 10, and the second end of the zero-ohm resistor 20 is grounded.

[0039] The distance between the first position of the filter spur line 10 and the first end of the filter spur line 10 is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal.

[0040] Specifically, the filter stub line 10, as the core conductive element in the RF harmonic filtering circuit 100 of this application, can be flexibly designed in terms of material and structure according to the actual application scenario, such as using planar transmission lines like microstrip lines or striplines. This type of filter stub line 10 is typically fabricated directly on the PCB (Printed Circuit Board) using a high-precision etching process. When the filter stub line 10 is connected to the RF path of a 5G RF signal, it forms a resonant match with the 5G RF signal frequency band, resulting in a significant stopband effect on the second harmonic of the 2.4G RF signal. In the circuit layout, one end of the filter stub line 10 is coupled to the 5G RF signal transmission line with low loss through precision solder joints or vias, while the other end extends to a predetermined electrical node position.

[0041] On the one hand, the zero-ohm resistor 20 serves as a precise physical connection point, providing a stable grounding reference for the filter branch line 10 through its low impedance characteristics. On the other hand, during the circuit simulation and debugging phase, the zero-ohm resistor 20 can be quickly replaced through soldering or surface mount technology. By adjusting the soldering position (i.e., the first position) of the first end of the zero-ohm resistor 20, it is convenient to adjust the equivalent electrical length of the filter branch line 10 according to the actual test data, thereby optimizing the bandwidth and attenuation depth of harmonic suppression.

[0042] Specifically, the physical distance between the first position of the filter stub line 10 (i.e., the coupling point of the first end of the zero-ohm resistor 20) and the first end of the filter stub line 10 is limited to a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4 GHz radio frequency signal (approximately 4.8-5.0 GHz). By adjusting the soldering position (i.e., the first position) of the first end of the zero-ohm resistor 20, the effective electrical length of the filter stub line 10 can be flexibly changed. When the distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is within the preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4 GHz radio frequency signal, that is, when the equivalent electrical length of the filter stub line 10 precisely matches an integer multiple of half the wavelength of the second harmonic of the 2.4 GHz radio frequency signal, the trajectory of the filter stub line 10 on the Smith chart will show a complete integer rotation, ultimately forming a short circuit at the coupling point between the filter stub line 10 and the 5G radio frequency signal transmission line. At this time, the second harmonic signal of the 2.4G radio frequency signal is forcibly reflected at the end of the filter branch line 10. The reflected wave and the incident wave produce destructive interference at the coupling point, so that the energy of this frequency band is efficiently guided to the grounding path of the zero ohm resistance 20, forming a low impedance discharge channel.

[0043] In the above solution, by adjusting the equivalent electrical length of the branch line, the bandpass characteristics within the 5G RF signal band can be flexibly achieved, while simultaneously forming a stopband attenuation for the second harmonic signal band of the 2.4G RF signal. This minimizes the introduction of additional insertion loss into the 5G RF signal path, ensuring stable transmission of the 5G RF signal while effectively filtering out interference from the second harmonic of the 2.4G RF signal. Furthermore, the replaceable nature of the zero-ohm resistor 20 significantly improves the yield and reliability of the product during mass production.

[0044] In some embodiments, the impedance of the filter branch line 10 is equal to or greater than the impedance of the 5G radio frequency signal transmission line.

[0045] Specifically, when the impedance of the filter stub 10 is equal to the impedance of the 5G RF signal transmission line, in non-2.4G RF signal second harmonic frequency bands (such as the 5G RF signal operating frequency band), the filter stub 10 is matched to the 5G RF signal, and the 5G RF signal energy passes through almost unaffected, avoiding excessive insertion loss. For example, if the impedance of the filter stub 10 is 50Ω, in the 5GHz frequency band, the 5G RF signal will only experience a small capacitive / inductive disturbance due to the parallel connection of the filter stub 10 (which can be compensated for by the matching circuit), and the attenuation of the 5G RF signal will be within a controllable range (e.g., within 0.5dB).

[0046] If the impedance of filter stub 10 is slightly higher than that of the 5G RF signal transmission line, when it is connected in parallel to the 5G RF signal transmission line, it will form a higher equivalent impedance at the frequency of the second harmonic of the 2.4G RF signal. This will enhance the suppression effect on the second harmonic of the 2.4G RF signal while reducing the attenuation of the 5G RF signal.

[0047] In one application scenario, the impedance of the 5G radio frequency signal transmission line is 50 ohms. When the impedance of the filter stub line 10 is equal to the impedance of the 5G radio frequency signal transmission line, the width of the filter stub line 10 is maintained at the standard line width of 0.09 mm to match the 50 ohm impedance.

[0048] In one embodiment, the width of the filter spur line 10 is 0.09 mm, and the distance between the first position of the filter spur line 10 and the first end of the filter spur line 10 is 19.1 mm. 19.1 mm is within a preset range of one half the wavelength of the second harmonic of the 2.4G radio frequency signal.

[0049] Specifically, the two ends of the 5G radio frequency signal transmission line are connected to port 1 and port 2 (not shown in the figure), as follows: Figure 2 As shown, Figure 2 Each point represents the transmission loss of the 5G radio frequency signal from port 1 to port 2. For example, point m1 indicates that the insertion loss of the 5G radio frequency signal from port 1 to port 2 is 21.22dB. At this time, the maximum path insertion loss of the 5G radio frequency signal is 9.991dB, and the minimum harmonic suppression is 27dB.

[0050] In one embodiment, when the width of the filter stub line 10 is 0.09 mm, and the distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is 38.4 mm, 38.4 mm falls within a preset range that is twice the half wavelength of the second harmonic of the 2.4 GHz radio frequency signal. Figure 3 As shown, the maximum insertion loss of the 5G radio frequency signal is 4.343dB, and the minimum harmonic suppression is 16.6dB.

[0051] In one embodiment, when the width of the filter stub line 10 is 0.09 mm and the distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is 57.5 mm, 57.5 mm falls within a preset range of three times the half wavelength of the second harmonic of the 2.4 GHz radio frequency signal. Figure 4 As shown, the maximum insertion loss of the 5G radio frequency signal is 2.388dB, and the minimum harmonic suppression is 14.26dB.

[0052] Combination Figure 2 , Figure 3 and Figure 4 It can be seen that when the width of the filter stub line 10 is kept at the standard line width of 0.09 mm that matches the 50 ohm impedance, when the distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is within a preset range of an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal, and the multiple gradually increases, the insertion loss of the 5G radio frequency signal can be reduced and the suppression of the second harmonic of the 2.4G radio frequency signal can be enhanced.

[0053] In the above scheme, by reasonably increasing the equivalent electrical length of the filter branch line 10 to an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal, not only can the signal insertion loss be effectively reduced and the signal transmission efficiency improved, but the harmonic suppression capability can also be significantly enhanced, thereby optimizing the radio frequency performance of the 5G radio frequency signal and providing a more stable and cleaner signal transmission environment for the wireless communication system.

[0054] See Figure 5 , Figure 5 This is a schematic diagram of the second embodiment of the radio frequency harmonic filtering circuit provided in this application. The radio frequency harmonic filtering circuit 100 includes: a filter branch line 10 and a zero-ohm resistor 20.

[0055] The first end of the filter branch line 10 is coupled to the 5G radio frequency signal transmission line; the first end of the zero-ohm resistor 20 is coupled to the first position of the filter branch line 10, and the second end of the zero-ohm resistor 20 is grounded.

[0056] The distance between the first position of the filter spur line 10 and the first end of the filter spur line 10 is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal.

[0057] In some embodiments, the radio frequency harmonic filtering circuit 100 further includes a filter element 30, the first end of which is coupled to a 5G radio frequency signal transmission line, and the second end of which is grounded.

[0058] In some embodiments, the filter element 30 is a capacitor or an inductor.

[0059] Specifically, capacitors or inductors exhibit unique impedance characteristics at high frequencies, meaning their impedance decreases as the frequency increases. When a 5G RF signal flows through a parallel capacitor or inductor, it provides a low-impedance path, allowing the signal to pass more smoothly and effectively reducing insertion loss during transmission. Since the second harmonic frequency of the 2.4G RF signal falls near the high-impedance region of the capacitor or inductor (relative to the 5G RF signal), it significantly suppresses the second harmonic of the 2.4G RF signal.

[0060] In the above scheme, the use of filter element 30 not only improves the transmission quality of 5G radio frequency signals, but also reduces the impact of harmonic interference on signals in other frequency bands, thereby optimizing the performance of the entire radio frequency system.

[0061] In another application scenario, the impedance of the 5G radio frequency signal transmission line is 50 ohms. When the width of the filter stub line 10 is narrowed to 0.06 mm, the impedance of the filter stub line 10 increases accordingly and becomes greater than the impedance of the 5G radio frequency signal transmission line.

[0062] Specifically, when the width of the filter stub line 10 becomes narrower, the impedance of the filter stub line 10 will increase accordingly, which may lead to a significant increase in insertion loss during 5G radio frequency signal transmission, affecting the integrity and quality of the signal.

[0063] In one embodiment, the distance between the first position of the filter branch line 10 and the first end of the filter branch line 10 is determined by the following formula:

[0064]

[0065] Where L represents the distance between the first position of the filter branch line 10 and the first end of the filter branch line 10, n represents a positive integer, c represents the speed of light in a vacuum, f represents the frequency of the 2.4G radio frequency signal, and ε represents the dielectric constant of the filter branch line 10.

[0066] Specifically, if changes in the width of the filter stub 10 lead to changes in the material structure (such as dielectric layer thickness and fill density) or test conditions (such as edge effects and parasitic capacitance), it will indirectly affect the measurement results of the dielectric constant □ of the filter stub 10. For example, an excessively narrow stub may induce parasitic effects, causing the observed value of the dielectric constant to deviate from the true value. Therefore, when the width of the filter stub 10 changes, even if the distance between the first position of the filter stub 10 and the first end of the filter stub 10 is an integer multiple of half the wavelength of the second harmonic of the 2.4 GHz radio frequency signal, the distance between the first position of the filter stub 10 and the first end of the filter stub 10 will still deviate.

[0067] In one embodiment, the physical distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is limited to a preset range of an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal ± 5%.

[0068] In one embodiment, the width of the filter spur line 10 is 0.06 mm, and when the distance between the first position of the filter spur line 10 and the first end of the filter spur line 10 is 39.5 mm, 39.5 mm is within a preset range of twice the wavelength of half the second harmonic of the 2.4G radio frequency signal.

[0069] Specifically, to reduce the increase in 5G RF signal insertion loss caused by the high impedance of the filter stub 10, a filter element 30 is connected in parallel on the 5G RF signal transmission line, such as... Figure 6 As shown, with a 0.5pF capacitor connected in parallel, the maximum insertion loss of the 5G RF signal is 1.233dB, and the minimum harmonic suppression is 11dB.

[0070] In one embodiment, when the width of the filter stub line 10 is 0.06 mm and the distance between the first position of the filter stub line 10 and the first end of the filter stub line 10 is 58.8 mm, 58.8 mm falls within a preset range of three times the half wavelength of the second harmonic of the 2.4 GHz radio frequency signal. Figure 7 As shown, the maximum insertion loss of the 5G radio frequency signal is 1.807dB, and the minimum harmonic suppression is 12.2dB.

[0071] Specifically, in order to reduce the increase in insertion loss of 5G RF signals caused by the high impedance of the filter stub 10, a filter element 30 is connected in parallel on the 5G RF signal transmission line, such as... Figure 8 As shown, with a 0.3pF capacitor connected in parallel, the maximum insertion loss of the 5G RF signal is 0.88dB, and the minimum harmonic suppression is 12.7dB, which basically meets most usage requirements.

[0072] Combination Figure 7 and Figure 8It can be seen that when the distance between the first position of the filter branch line 10 and the first end of the filter branch line 10 is fixed, connecting the filter element 30 in parallel on the 5G radio frequency signal transmission line will effectively reduce the insertion loss of the 5G radio frequency signal.

[0073] See Figure 9 , Figure 9 This is a schematic diagram of an embodiment of the electronic device provided in this application. The electronic device 1000 includes a radio frequency harmonic filtering circuit 100, which is the same as the radio frequency harmonic filtering circuit 100 described above, and will not be repeated here.

[0074] One technical solution adopted in this application is to provide a radio frequency (RF) harmonic filtering circuit, which includes: a filter stub line, the first end of which is coupled to a 5G RF signal transmission line; a zero-ohm resistor, the first end of which is coupled to a first position of the filter stub line, and the second end of which is grounded; wherein the distance between the first position of the filter stub line and the first end of the filter stub line is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G RF signal. By means of the above method, a filter stub line conforming to an integer multiple of half the wavelength of the second harmonic of the 2.4G RF signal is coupled to the 5G RF signal transmission line, and the filter stub line is grounded, thereby filtering out the second harmonic of the 2.4G RF signal using the filter stub line without affecting the transmission of the 5G RF signal.

[0075] In the several embodiments provided in this application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0076] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0077] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0078] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A radio frequency harmonic filtering circuit, characterized in that, The radio frequency harmonic filtering circuit includes: A filter stub line, the first end of which is coupled to a 5G radio frequency signal transmission line; A zero-ohm resistor, wherein the first end of the zero-ohm resistor is coupled to the first position of the filter branch line, and the second end of the zero-ohm resistor is grounded; The distance between the first position of the filter branch line and the first end of the filter branch line is within a preset range that is an integer multiple of half the wavelength of the second harmonic of the 2.4G radio frequency signal.

2. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, The radio frequency harmonic filtering circuit also includes: A filter element, wherein the first end of the filter element is coupled to the 5G radio frequency signal transmission line, and the second end of the filter element is grounded.

3. The radio frequency harmonic filtering circuit according to claim 2, characterized in that, The filtering element is a capacitor or an inductor.

4. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, When the width of the filter spur line is 0.09 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 19.1 mm, 19.1 mm is within a preset range of one half the wavelength of the second harmonic of the 2.4G radio frequency signal.

5. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, When the width of the filter spur line is 0.09 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 38.4 mm, 38.4 mm is within a preset range of twice the wavelength of half the second harmonic of the 2.4G radio frequency signal.

6. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, When the width of the filter spur line is 0.09 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 57.5 mm, 57.5 mm is within a preset range of three times the half wavelength of the second harmonic of the 2.4G radio frequency signal.

7. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, When the width of the filter spur line is 0.06 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 39.5 mm, 39.5 mm is within a preset range of twice the wavelength of half the second harmonic of the 2.4G radio frequency signal.

8. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, When the width of the filter spur line is 0.06 mm and the distance between the first position of the filter spur line and the first end of the filter spur line is 58.8 mm, 58.8 mm is within a preset range of three times the half wavelength of the second harmonic of the 2.4G radio frequency signal.

9. The radio frequency harmonic filtering circuit according to claim 1, characterized in that, The distance between the first position of the filter branch line and the first end of the filter branch line is determined by the following formula: Where L represents the distance between the first position of the filter branch line and the first end of the filter branch line, n represents a positive integer, c represents the speed of light in a vacuum, f represents the frequency of the 2.4G radio frequency signal, and ε represents the dielectric constant of the filter branch line.

10. An electronic device, characterized in that, The electronic device includes a radio frequency harmonic filtering circuit as described in any one of claims 1-9.

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