LC band-pass filter circuit and filter

Abstract

The invention discloses an LC band-pass filtering circuit and a filter, and belongs to the technical field of microwave filtering, the circuit comprises an input port, an output port, a first band-pass filtering unit, a first attenuation suppression unit, a second attenuation suppression unit and a second band-pass filtering unit; one end of the first attenuation suppression unit is connected with the input port, and the other end is grounded; the output end of the first band-pass filtering unit is connected with the input end of the second band-pass filtering unit; the output end of the second band-pass filtering unit is connected with the output port; and the second attenuation suppression unit is respectively connected with the input port, the input end and the output end of the first band-pass filtering unit and the input end of the second band-pass filtering unit. A plurality of transmission zeros are introduced into each band-pass filtering unit, the plurality of transmission zeros are formed through the grounded attenuation suppression unit and the band-pass filtering unit, and out-of-band suppression and insertion loss suppression are provided for signal filtering.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave filtering, and in particular to an LC bandpass filtering circuit and a filter. Background Art

[0002] In RF circuit design, the application of LC bandpass filters in intermediate frequency circuits has irreplaceable roles and advantages. As the plate circuits are now miniaturized and the requirements for out-of-band suppression and insertion loss of bandpass filters are becoming increasingly stringent, it is necessary to increase the order and transmission zero point to achieve high suppression effect.

[0003] It is difficult to add many transmission zeros to traditional LC filters, and the insertion loss will increase as the filter order increases, which is often a contradiction. It is difficult for traditional LC filters to achieve high near-end suppression attenuation, and usually it is necessary to increase the order and transmission zeros to change the out-of-band suppression attenuation amplitude, but too many transmission zeros and orders will bring additional insertion loss and circuit complexity.

[0004] Therefore, there is an urgent need for an LC bandpass filter circuit and filter that can provide good out-of-band suppression and insertion loss suppression during the signal filtering process. Summary of the invention

[0005] In view of this, it is necessary to provide an LC bandpass filter circuit and filter that can provide good out-of-band suppression and insertion loss suppression during the signal filtering process.

[0006] In order to achieve the above-mentioned object, on the one hand, the present invention provides an LC bandpass filter circuit, comprising: an input port, an output port, a first bandpass filter unit, a first attenuation suppression unit, a second attenuation suppression unit and a second bandpass filter unit; One end of the first attenuation suppression unit is connected to the input port, and the other end is grounded; the output end of the first band-pass filter unit is connected to the input end of the second band-pass filter unit; the output end of the second band-pass filter unit is connected to the output port; the second attenuation suppression unit is respectively connected to the input port, the input end and the output end of the first band-pass filter unit, and the input end of the second band-pass filter unit; Among them, the first bandpass filter unit and the second bandpass filter unit include multiple grounded LC series resonance units, and multiple filtering transmission zero points are formed in the signal filtering process through the grounded first attenuation suppression unit and the second attenuation suppression unit and the first bandpass filter unit and the second bandpass filter unit, providing out-of-band suppression and insertion loss suppression for signal filtering.

[0007] In a possible implementation, the first attenuation suppression unit includes a first inductor and a first capacitor; One end of the first inductor is connected to the input port, and the other end is grounded; One end of the first capacitor is connected to the input port, and the other end is grounded.

[0008] In one possible implementation, the LC series resonance unit includes an inductor and a capacitor connected in series, one end of the multiple LC series resonance units is connected to the first bandpass filter unit and the second bandpass filter unit, and the other end is grounded, and a bandpass transmission zero point is generated by the grounded multiple LC series resonance units.

[0009] In a possible implementation, the first bandpass filtering unit includes a first low-pass filtering subunit and a first high-pass filtering subunit; The first low-pass filtering subunit and the first high-pass filtering subunit are connected in series.

[0010] In a possible implementation, the multiple bandpass transmission zeros include a first transmission zero and a second transmission zero; the multiple LC series resonance units include a first LC resonance subunit and a second LC resonance subunit; the first low-pass filter subunit includes a second inductor, a third inductor, a first LC resonance subunit and a second LC resonance subunit; The second inductor and the third inductor are connected in series; One end of the first LC resonator unit is connected to the second inductor, and the other end is grounded, so as to form a first transmission zero point; One end of the second LC resonator unit is connected to the third inductor, and the other end is grounded, so as to form a second transmission zero point.

[0011] In a possible implementation, the plurality of bandpass transmission zeros further include a third transmission zero and a fourth transmission zero; the plurality of LC series resonance units further include a third LC resonance subunit and a fourth LC resonance subunit; the first high-pass filter subunit includes a second capacitor and a third capacitor; The second capacitor and the third capacitor are connected in series; One end of the third LC resonator unit is connected to the second capacitor, and the other end is grounded, so as to form a third transmission zero point; One end of the fourth LC resonator unit is connected to the third capacitor, and the other end is grounded, so as to form a fourth transmission zero point.

[0012] In a possible implementation, the second attenuation suppression unit includes a fifth capacitor and a sixth capacitor; One end of the fifth capacitor is connected to the input port, and the other end is connected to the input end of the first band-pass filter unit; One end of the sixth capacitor is connected to the output end of the first band-pass filtering unit, and the other end is grounded.

[0013] In a possible implementation, the second bandpass filtering unit includes a second low-pass filtering subunit and a second high-pass filtering subunit; The second low-pass filtering subunit and the second high-pass filtering subunit are connected in series.

[0014] In a possible implementation, the plurality of bandpass transmission zeros further include a fifth transmission zero and a sixth transmission zero; the plurality of LC series resonance units further include a fifth LC resonance subunit and a sixth LC resonance subunit; The second low-pass filter subunit includes a fourth inductor and a fifth LC resonance subunit; The second high-pass filter subunit includes a fourth capacitor and a sixth LC resonance subunit; The fourth inductor and the fourth capacitor are connected in series; One end of the fifth LC resonator unit is connected to the fourth inductor, and the other end is grounded, so as to form a fifth transmission zero point; One end of the sixth LC resonator unit is connected to the fourth capacitor, and the other end is grounded, so as to form a sixth transmission zero point.

[0015] In a second aspect, the present invention further provides a filter, comprising the LC bandpass filter circuit as described above.

[0016] The beneficial effects of the present invention are as follows: by setting an input port, an output port, a first band-pass filter unit, a first attenuation suppression unit, a second attenuation suppression unit and a second band-pass filter unit; one end of the first attenuation suppression unit is connected to the input port, and the other end is grounded; the output end of the first band-pass filter unit is connected to the input end of the second band-pass filter unit; the output end of the second band-pass filter unit is connected to the output port; the second attenuation suppression unit is respectively connected to the input port, the input end, the output end of the first band-pass filter unit and the input end of the second band-pass filter unit; the first band-pass filter unit and the second band-pass filter unit include a plurality of grounded LC series resonance units, and through the grounded first attenuation suppression unit and the second attenuation suppression unit and the first band-pass filter unit and the second band-pass filter unit, a plurality of filtering transmission zero points are formed in the signal filtering process, providing out-of-band suppression and insertion loss suppression for signal filtering. The present invention forms a plurality of filtering transmission zero points by introducing a plurality of band-pass transmission zero points in the band-pass filter unit, combining the grounded attenuation suppression unit and the band-pass filter unit, and providing out-of-band suppression and insertion loss suppression for signal filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, 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 work.

[0018] Figure 1 The present invention provides a schematic structural diagram of an LC bandpass filter circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, unless otherwise specified, “plurality” means two or more than two.

[0021] The descriptions of "first", "second", etc. involved in the embodiments of the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the technical features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0022] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] Before describing the embodiments, the following definitions are given for the relevant terms: The transmission zero is the frequency point where the filter transfer function is equal to zero. At this frequency point, the signal energy cannot pass through the filter, thus completely blocking the signal. From an energy perspective, the transmission zero is the frequency point where the power is fully reflected back to the signal end.

[0024] A bandpass filter is a filter that allows signals within a certain frequency range to pass while rejecting signals below and above that frequency range.

[0025] The present invention provides an LC bandpass filter circuit and a filter, which are respectively described below.

[0026] In some embodiments of the present invention, Figure 1 As shown, Figure 1 A schematic diagram of the structure of an embodiment of the LC bandpass filter circuit provided by the present invention, comprising: an input port 10, an output port 50, a first bandpass filter unit 30, a first attenuation suppression unit 20, a second attenuation suppression unit (without serial number in the figure), and a second bandpass filter unit 40; One end of the first attenuation suppression unit 20 is connected to the input port 10, and the other end is grounded; the output end of the first band-pass filter unit 30 is connected to the input end of the second band-pass filter unit 40; the output end of the second band-pass filter unit 40 is connected to the output port 50; the second attenuation suppression unit is respectively connected to the input port 10, the input end and the output end of the first band-pass filter unit 30, and the input end of the second band-pass filter unit 40; Among them, the first bandpass filter unit 30 and the second bandpass filter unit 40 include multiple grounded LC series resonant units. Through the grounded first attenuation suppression unit 20 and the second attenuation suppression unit and the first bandpass filter unit 30 and the second bandpass filter unit 40, multiple filtering transmission zero points are formed in the signal filtering process, providing out-of-band suppression and insertion loss suppression for signal filtering.

[0027] It should be noted that this embodiment is an improvement on the elliptical filter circuit. The elliptical filter is a filter with equal ripple characteristics in both the passband and the stopband. Compared with other types of filters, the elliptical filter has the smallest passband and stopband fluctuations under the same order, and can obtain a narrower transition bandwidth. First, the center frequency, bandwidth, passband fluctuations and stopband attenuation parameters in the bandpass filter circuit are determined, and a suitable order of the elliptical filter circuit is selected. The higher the order, the better the filtering performance, but the higher the complexity of the design and implementation. Therefore, it is necessary to select a suitable order, and set the parameters of each component in the low-pass filter circuit and the high-pass filter circuit through the elliptical function, the parameters of each elliptical filter circuit and the allowed specific frequency range. The low-pass filter circuit and the high-pass filter circuit are cascaded to form a bandpass filter unit, and each filter component is isolated by designing a grounded series LC circuit. A test device such as a network analyzer or a spectrum analyzer is used to perform a simulation test on the constructed filter circuit. According to the test results, the parameters of each component in the circuit are adjusted and optimized to improve the performance of the filter.

[0028] Specifically, the first attenuation unit forms the first transmission zero point by grounding, and improves the transmission zero point attenuation characteristics formed on the left and right sides of the passband. In this embodiment, appropriate parameters are set for the components in the first attenuation unit by calculation, and the passband suppression attenuation can be increased to 10dB by simulation test; the first bandpass filter unit performs the first filtering and screening on the input signal, allowing the signal within a specific frequency range to pass; the second attenuation suppression unit isolates the first bandpass filter unit from the second bandpass filter unit, improves the attenuation of the transmission zero point formed on the left and right sides of the passband, and the capacitor connected to the input port serves as a second attenuation suppression unit. Part, which is combined with high-pass filtering components to further enhance out-of-band suppression; the second band-pass filtering unit further filters the signal to ensure that only signals within the required frequency range can pass. In the first band-pass filtering unit and the second band-pass filtering unit, multiple grounded series LC circuits are set to form multiple transmission zeros, and transmission zeros are generated in the stop band of the filter, thereby further improving the stop band attenuation performance of the filter. The first band-pass filtering unit and the second band-pass filtering unit connected in series are combined with the grounded series LC circuit to minimize transmission loss, improve transmission zero characteristics and increase the attenuation amplitude of left and right pass band suppression.

[0029] In this embodiment, an input port 10, an output port 50, a first band-pass filter unit 30, a first attenuation suppression unit 20, a second attenuation suppression unit and a second band-pass filter unit 40 are set; one end of the first attenuation suppression unit 20 is connected to the input port 10, and the other end is grounded; the output end of the first band-pass filter unit 30 is connected to the input end of the second band-pass filter unit 40; the output end of the second band-pass filter unit 40 is connected to the output port 50; the second attenuation suppression unit is respectively connected to the input port 10, the input end and the output end of the first band-pass filter unit 30 and the input end of the second band-pass filter unit 40; the first band-pass filter unit 30 and the second band-pass filter unit 40 include a plurality of grounded LC series resonant units, and a plurality of filtering transmission zeros are formed in the signal filtering process through the grounded first attenuation suppression unit 20 and the second attenuation suppression unit and the first band-pass filter unit 30 and the second band-pass filter unit 40, so as to provide out-of-band suppression and insertion loss suppression for the signal filtering.

[0030] The present invention forms multiple filtering transmission zero points by introducing multiple bandpass transmission zero points in the bandpass filtering unit, combining the grounded attenuation suppression unit and the bandpass filtering unit, and provides out-of-band suppression and insertion loss suppression for signal filtering.

[0031] In some embodiments of the present invention, the first attenuation suppression unit 20 includes a first inductor L1 and a first capacitor C1; One end of the first inductor L1 is connected to the input port 10, and the other end is grounded; One end of the first capacitor C1 is connected to the input port 10 , and the other end is grounded.

[0032] Specifically, suitable inductors and capacitors are selected according to parameters such as the required bandwidth, center frequency, and out-of-band suppression. By adjusting the parameter values ​​of the inductors and capacitors, a filter with the required frequency response characteristics is achieved. Grounding the inductor can form a more stable electrical connection with other components in the circuit, reducing electromagnetic interference and noise. Grounding the capacitor can improve its stability and better absorb and release electrical energy, thereby improving the frequency response and transmission zero point characteristics of the filter. A grounded inductor and a grounded capacitor are set at the input port of the bandpass filter circuit to form an LC resonant circuit, providing frequency selectivity for the circuit. Through multiple experiments and tests, the values ​​of the inductor and the capacitor are accurately adjusted to find the best combination, accurately control the passband and stopband characteristics of the filter, improve the transmission zero point attenuation characteristics of the filter on both sides of the passband, and improve the performance of the filter.

[0033] In this embodiment, an LC resonant circuit is formed by grounding an inductor and a capacitor, thereby improving the transmission zero-point attenuation characteristics formed on the left and right sides of the passband and improving the performance of the filter.

[0034] In some embodiments of the present invention, the LC series resonant unit includes an inductor and a capacitor connected in series, one end of the multiple LC series resonant units is connected to the first bandpass filter unit and the second bandpass filter unit, and the other end is grounded, and a bandpass transmission zero point is generated by the grounded multiple LC series resonant units.

[0035] Specifically, by setting a plurality of grounded LC series resonance units on the bandpass filter, the grounded LC series resonance units produce a resonance effect at a specific frequency, thereby introducing a transmission zero point in the transmission characteristics of the filter. When the frequency of the input signal is equal to the resonance frequency, the resonance unit absorbs most of the signal energy, resulting in a reduction in the amplitude of the input signal, forming a transmission zero point. Through a plurality of grounded series LC series resonance units, a plurality of transmission zero points can be introduced on both sides of the passband. These transmission zero points can further improve the frequency selectivity and stopband suppression capability of the filter.

[0036] This embodiment introduces multiple transmission zeros on both sides of the passband through multiple grounded series LC series resonance units, thereby improving the performance of the filter.

[0037] In some embodiments of the present invention, the first bandpass filtering unit 30 includes a first low-pass filtering subunit 31 and a first high-pass filtering subunit 32; The first low-pass filter subunit 31 and the first high-pass filter subunit 32 are connected in series.

[0038] Specifically, the high-pass filtering unit is used to remove the low-frequency components in the signal and retain only the high-frequency part, allowing signals with frequencies higher than a preset high-pass critical value to pass through, while signals below the high-pass critical value are attenuated and blocked. In contrast to the high-pass filtering unit, the low-pass filtering unit removes the high-frequency components in the signal and retains only the low-frequency part, allowing signals with frequencies lower than a preset low-pass critical value to pass through, while signals above the low-pass critical value are attenuated or blocked. By connecting the high-pass filtering unit and the low-pass filtering unit in series and adjusting their cutoff frequencies, only signals between the two cutoff frequencies can pass through.

[0039] In some embodiments of the present invention, the plurality of bandpass transmission zeros include a first transmission zero P1 and a second transmission zero P2; the plurality of LC series resonance units include a first LC resonance subunit 311 and a second LC resonance subunit 312; the first low-pass filter subunit 31 includes a second inductor L2, a third inductor L3, a first LC resonance subunit 311 and a second LC resonance subunit 312; The second inductor L2 and the third inductor L3 are connected in series; One end of the first LC resonator unit 311 is connected to the second inductor L2, and the other end is grounded, so as to form a first transmission zero point P1; One end of the second LC resonator unit 312 is connected to the third inductor L3 , and the other end is grounded, so as to form a second transmission zero point P2 .

[0040] Specifically, the inductor has the characteristic of isolating AC and passing DC, and the higher the AC frequency, the less likely it is to pass. Therefore, the second inductor L2 and the third inductor L3 connected in series will have an obstructive effect on high-frequency signals. The two inductors are connected in series, and a grounded series LC circuit is connected in the middle of each inductor, so the entire circuit forms a multi-order low-pass filter structure. Each additional first-order filter can further increase the attenuation of high-frequency signals, while retaining low-frequency signals to form a low-pass filter subunit.

[0041] In this embodiment, two inductors are connected in series, and two grounded series LC circuits are connected in the middle of each inductor to form a multi-order low-pass filter. This low-pass filter circuit has a simple structure, good stability and high reliability.

[0042] In some embodiments of the present invention, the plurality of bandpass transmission zeros further include a third transmission zero P3 and a fourth transmission zero P4; the plurality of LC series resonance units further include a third LC resonance subunit 321 and a fourth LC resonance subunit 322; the first high-pass filter subunit 32 includes a second capacitor C2 and a third capacitor C3; The second capacitor C2 and the third capacitor C3 are connected in series; One end of the third LC resonator unit 321 is connected to the second capacitor C2, and the other end is grounded, so as to form a third transmission zero point P3; One end of the fourth LC resonator unit 322 is connected to the third capacitor C3, and the other end is grounded, so as to form a fourth transmission zero point P4.

[0043] Specifically, the second capacitor C2 and the third capacitor C3 connected in series will have an obstructive effect on high-frequency signals because the impedance of the capacitor to high-frequency signals is greater than that to low-frequency signals. When the signal passes through the first high-pass filter subunit 32, it will first encounter the third LC resonant subunit 321, which will attenuate or reflect to varying degrees according to the frequency of the signal. Then, the signal passes through the second capacitor C2, is attenuated at high frequency, encounters the fourth LC resonant subunit 322, further encounters the third LC resonant subunit 321, and finally passes through the third capacitor C3, is further attenuated at high frequency, and the entire circuit forms a filter with a specific frequency response.

[0044] In this embodiment, two capacitors are connected in series to form a multi-order high-pass filter, and two grounded series LC circuits are connected in the middle of each capacitor to form an effective high-pass filter structure. This high-pass filter circuit has a simple structure, good stability and high reliability.

[0045] In some embodiments of the present invention, the second attenuation suppression unit includes a fifth capacitor C5 and a sixth capacitor C6; One end of the fifth capacitor C5 is connected to the input port 10, and the other end is connected to the input end of the first band-pass filter unit 30; One end of the sixth capacitor C6 is connected to the output end of the first band-pass filter unit 30 , and the other end is grounded.

[0046] Specifically, by connecting the fifth capacitor C5 in series with the first bandpass filter unit 30, the frequency response characteristics of the capacitor and the frequency selection function of the bandpass filter circuit are utilized to further enhance the performance of the filter, and the capacitor and inductor are alternately connected in series to improve the transmission zero point characteristics and increase the attenuation amplitude of the left and right passband suppression, thereby providing better out-of-band suppression in the first bandpass filter unit 30.

[0047] Furthermore, a grounded sixth capacitor C6 is provided between the first bandpass filter unit 30 and the second bandpass filter unit 40 to isolate the first bandpass filter unit 30 from the second bandpass filter unit 40, and at the same time improve the attenuation of the transmission zero point formed on the left and right sides of the passband, thereby reducing the signal transmission loss.

[0048] This embodiment provides good out-of-band suppression for the filter circuit by setting a capacitor connected in series with the pass filter unit and a grounded capacitor, improves the passband left and right suppression attenuation, and reduces transmission loss.

[0049] In some embodiments of the present invention, the second bandpass filtering unit 40 includes a second low-pass filtering subunit 41 and a second high-pass filtering subunit 42; The second low-pass filter sub-unit 41 and the second high-pass filter sub-unit 42 are connected in series.

[0050] This embodiment sets a simple second bandpass filter unit 40 to filter the output signal of the first bandpass filter unit 30 again, so as to more effectively select and transmit the signal within a specific frequency range, more effectively suppress out-of-band interference, and improve the performance of the filter circuit.

[0051] In some embodiments of the present invention, the plurality of bandpass transmission zeros further include a fifth transmission zero P5 and a sixth transmission zero P6; the plurality of LC series resonance units further include a fifth LC resonance subunit 411 and a sixth LC resonance subunit 421; The second low-pass filter subunit 41 includes a fourth inductor L4 and a fifth LC resonance subunit 411; The second high-pass filter subunit 42 includes a fourth capacitor C4 and a sixth LC resonant subunit 421; The fourth inductor L4 and the fourth capacitor C4 are connected in series; One end of the fifth LC resonator unit 411 is connected to the fourth inductor L4, and the other end is grounded, so as to form a fifth transmission zero point P5; One end of the sixth LC resonator unit 421 is connected to the fourth capacitor C4 , and the other end is grounded, so as to form a sixth transmission zero point P6 .

[0052] Specifically, the inductor L4 and the capacitor are connected in series, and the output ends thereof are respectively connected to a grounded series LC series resonant unit, forming a simple filtering circuit which can be regarded as a combination of two interacting LC resonant circuits, each of which performs frequency selection and filtering on its input signal.

[0053] Based on the above LC bandpass filter circuit, an embodiment of the present invention further provides a filter accordingly, which can implement the technical solution described in the above LC bandpass filter circuit embodiment, and will not be described in detail here.

[0054] The LC bandpass filter circuit provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An LC bandpass filter circuit, characterized in that: include: An input port, an output port, a first band-pass filtering unit, a first attenuation suppression unit, a second attenuation suppression unit, and a second band-pass filtering unit; One end of the first attenuation suppression unit is connected to the input port, and the other end is grounded; the output end of the first band-pass filter unit is connected to the input end of the second band-pass filter unit; the output end of the second band-pass filter unit is connected to the output port; The second attenuation suppression unit is respectively connected to the input port, the input end and the output end of the first band-pass filtering unit, and the input end of the second band-pass filtering unit; Among them, the first bandpass filter unit and the second bandpass filter unit include multiple grounded LC series resonance units, and multiple filtering transmission zero points are formed in the signal filtering process through the grounded first attenuation suppression unit and the second attenuation suppression unit and the first bandpass filter unit and the second bandpass filter unit, providing out-of-band suppression and insertion loss suppression for signal filtering.

2. The LC bandpass filter circuit according to claim 1, characterized in that: The first attenuation suppression unit includes a first inductor and a first capacitor; One end of the first inductor is connected to the input port, and the other end is grounded; One end of the first capacitor is connected to the input port, and the other end is grounded.

3. The LC bandpass filter circuit according to claim 1, characterized in that: The LC series resonance unit includes an inductor and a capacitor connected in series. One end of the multiple LC series resonance units is connected to the first bandpass filter unit and the second bandpass filter unit, and the other end is grounded. A bandpass transmission zero point is generated by the grounded multiple LC series resonance units.

4. The LC bandpass filter circuit according to claim 1, characterized in that: The first bandpass filtering unit includes a first low-pass filtering subunit and a first high-pass filtering subunit; The first low-pass filtering subunit and the first high-pass filtering subunit are connected in series.

5. The LC bandpass filter circuit according to claim 4, characterized in that: The multiple bandpass transmission zeros include a first transmission zero and a second transmission zero; the multiple LC series resonance units include a first LC resonance subunit and a second LC resonance subunit; the first low-pass filter subunit includes a second inductor, a third inductor, a first LC resonance subunit and a second LC resonance subunit; The second inductor and the third inductor are connected in series; One end of the first LC resonator unit is connected to the second inductor, and the other end is grounded, so as to form a first transmission zero point; One end of the second LC resonator unit is connected to the third inductor, and the other end is grounded, so as to form a second transmission zero point.

6. The LC bandpass filter circuit according to claim 5, characterized in that: The plurality of bandpass transmission zero points further include a third transmission zero point and a fourth transmission zero point; the plurality of LC series resonance units further include a third LC resonance subunit and a fourth LC resonance subunit; the first high-pass filter subunit includes a second capacitor and a third capacitor; The second capacitor and the third capacitor are connected in series; One end of the third LC resonator unit is connected to the second capacitor, and the other end is grounded, so as to form a third transmission zero point; One end of the fourth LC resonator unit is connected to the third capacitor, and the other end is grounded, so as to form a fourth transmission zero point.

7. The LC bandpass filter circuit according to claim 1, characterized in that: The second attenuation suppression unit includes a fifth capacitor and a sixth capacitor; One end of the fifth capacitor is connected to the input port, and the other end is connected to the input end of the first band-pass filter unit; One end of the sixth capacitor is connected to the output end of the first band-pass filtering unit, and the other end is grounded.

8. The LC bandpass filter circuit according to claim 1, characterized in that: The second bandpass filtering unit includes a second low-pass filtering subunit and a second high-pass filtering subunit; The second low-pass filtering subunit and the second high-pass filtering subunit are connected in series.

9. The LC bandpass filter circuit according to claim 8, characterized in that: The plurality of bandpass transmission zeros further include a fifth transmission zero and a sixth transmission zero; the plurality of LC series resonance units further include a fifth LC resonance subunit and a sixth LC resonance subunit; The second low-pass filter subunit includes a fourth inductor and a fifth LC resonance subunit; The second high-pass filter subunit includes a fourth capacitor and a sixth LC resonance subunit; The fourth inductor and the fourth capacitor are connected in series; One end of the fifth LC resonator unit is connected to the fourth inductor, and the other end is grounded, so as to form a fifth transmission zero point; One end of the sixth LC resonator unit is connected to the fourth capacitor, and the other end is grounded, so as to form a sixth transmission zero point.

10. A filter, characterized in that: The method comprises the LC bandpass filter circuit as claimed in any one of claims 1 to 9.

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