WO2023231153A1 - Passive low-pass filter and low-pass filter circuit - Google Patents

Abstract

The present application belongs to the technical field of filtering electronics, and provides a passive low-pass filter and a low-pass filter circuit. The low-pass filter comprises: a radio frequency input module, a first resonance module, a first attenuation module, a plurality of second resonance modules connected in series, a plurality of second attenuation modules and a radio frequency output module. Specifically, the radio frequency input module is used for outputting a first radio frequency signal, and the first resonance module is used for outputting a second radio frequency signal of a preset passband frequency; the first attenuation module is used for attenuating a clutter signal in the second radio frequency signal; the plurality of second resonance modules connected in series are used for adjusting the frequency of the second radio frequency signal; each second attenuation module is used for attenuating the clutter signal in the second radio frequency signal to generate a third radio frequency signal; and the radio frequency output module is used for outputting the third radio frequency signal. By means of the embodiments of the present application, the problems of broadband passband and frequency cut-off characteristics of a conventional low-pass filter being unable to meet requirements and the volume miniaturization thereof being insufficient are solved.

Description

A passive low-pass filter and low-pass filter circuit

This application claims priority to the Chinese patent application with application number 202210602935.1 filed with the China Patent Office on May 30, 2022, the entire content of which is incorporated into this application by reference.

Technical field

The present application belongs to the field of filtering electronic technology, and in particular relates to a passive low-pass filter and a low-pass filter circuit.

Background technique

In the rapidly developing modern wireless communication systems, such as Virtual Reality (VR), Wireless Local Area Network (WLAN), satellite communications, etc., the demand for low-pass filters is increasing day by day. In these systems, low-pass filters are used in the RF front-end receiver to suppress image frequencies, local oscillator frequencies, and harmonics.

Currently, in traditional low-pass filters, because the equivalent inductor has self-capacitance and the equivalent capacitance has self-inductance, second harmonics are easily generated in practical applications, affecting the performance of the filter. At the same time, with the development of miniaturization of electronic equipment, the filters implemented by existing technology are larger and cannot meet the demand for miniaturization.

Therefore, the traditional filter has the problem that the wide passband and steep frequency cutoff characteristics of the filter circuit cannot meet the needs, and the miniaturization of the low-pass filter is not enough.

technical problem

This application provides a passive low-pass filter and a low-pass filter circuit, aiming to solve the problems that the wide-band passband and frequency cutoff characteristics of the traditional low-pass filter cannot meet the needs and the size is not sufficiently miniaturized.

Technical solutions

The first aspect of the embodiment of the present application provides a passive low-pass filter, including:

A radio frequency input module is used to access radio frequency signals, mix and process the radio frequency signals, and output a first radio frequency signal;

A first resonance module, coupled to the radio frequency input module, is used to adjust the frequency of the first radio frequency signal to output a second radio frequency signal with a preset passband frequency;

A first attenuation module, coupled to the first resonance module, used to attenuate the clutter signal in the second radio frequency signal;

A plurality of second resonant modules connected in series, coupled with the first resonant module, used to adjust the frequency of the second radio frequency signal;

A plurality of second attenuation modules, the first end of each second attenuation module is coupled to a common node between adjacent second resonant modules, and the second end of each second attenuation module is grounded , used to attenuate the clutter signal in the second radio frequency signal and generate a third radio frequency signal;

A radio frequency output module is connected to the plurality of second resonance modules connected in series and is used to output the third radio frequency signal.

In one embodiment, the first resonant module includes a first inductor and a first capacitor, and the first end of the first inductor and the first end of the first capacitor are commonly connected to the radio frequency input module, The second end of the first inductor and the second end of the first inductor are commonly connected to the second resonant module.

In one embodiment, each of the second resonant modules includes a second inductor and a second capacitor, and the second inductor is connected in parallel with the second capacitor.

In one embodiment, the first attenuation module includes at least one capacitor, a first end of the at least one capacitor is connected to the first resonant module, and a second end of the at least one capacitor is connected to ground.

In one embodiment, the first inductor and the second inductor are spiral inductors or rectangular inductors.

In one embodiment, the structure of the first capacitor and the second capacitor is a metal-dielectric-metal structure.

In one embodiment, the passive low-pass filter further includes a substrate layer and a grounded metal layer;

Wherein, the first resonant module and the second resonant module are formed on the substrate layer, and the first attenuation module and the second attenuation module are connected to the ground metal layer through a through-hole structure.

In one embodiment, the substrate layer material is gallium arsenide material, and the thickness of the substrate layer is 100±5 μm.

In one embodiment, the radio frequency input module and the radio frequency output module are both coplanar port structures.

A second aspect of the embodiment of the present application provides a low-pass filter circuit, including the passive low-pass filter as described in any one of the above.

beneficial effects

Compared with the prior art, the beneficial effects of the embodiments of the present application are:

The above-mentioned low-pass filter circuit includes a radio frequency input module, a first resonance module, a first attenuation module, a plurality of second resonance modules connected in series, a plurality of second attenuation modules and a radio frequency output module. Among them, the radio frequency input module is used to access the radio frequency signal and output the first radio frequency signal; the first resonance module is used to output the second radio frequency signal with a preset passband frequency; the first attenuation module is used to attenuate the impurities in the second radio frequency signal. wave signal; multiple second resonance modules connected in series are used to adjust the frequency of the second radio frequency signal; each second attenuation module is used to attenuate the clutter signal in the second radio frequency signal to generate a third radio frequency signal; the radio frequency output module is used to to output the third radio frequency signal. The embodiments of the present application can solve the problems that the wide-band passband and frequency cutoff characteristics of the traditional low-pass filter cannot meet the needs and the size is insufficiently miniaturized. The main inventive concept of the present application is to set the first attenuation module and the second attenuation module. It can effectively attenuate the clutter signal in the radio frequency signal. By setting the first resonant module and the second resonant module, the frequency of the radio frequency signal can be adjusted. This operation can effectively avoid the wide-band pass of the filter circuit in the traditional filter. The band and steep frequency cutoff characteristics cannot meet the needs, as well as the problem of insufficient miniaturization of the low-pass filter.

Description of the drawings

Figure 1 is a schematic diagram of the principle of a passive low-pass filter provided by an embodiment of the present application;

Figure 2 is an equivalent circuit diagram of a passive low-pass filter provided by an embodiment of the present application;

Figure 3 is an equivalent circuit diagram of another passive low-pass filter provided by an embodiment of the present application;

Figure 4 is a schematic structural diagram of another passive low-pass filter provided by an embodiment of the present application;

Figure 5 is a schematic diagram of parameter test curves of the input port return loss S11 and the output port return loss S22 of a low-pass filter with a passband frequency of 0.5 GHz provided by an embodiment of the present application;

Figure 6 is a schematic diagram of the stopband suppression S21 parameter test curve of a low-pass filter with a passband frequency of 0.5 GHz provided by an embodiment of the present application.

Among them, each figure in the figure is marked with:

101. Radio frequency input module; 102. Radio frequency output module; 103. First resonance module; 104. Multiple second resonance modules; 105. First attenuation module; 106. Multiple second attenuation modules.

Embodiments of the invention

In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clear, this application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It should be understood that the terms "length", "width", "top", "bottom", "front", "back", "left", "right", "vertical", "horizontal", "top" The orientations or positional relationships indicated by "bottom", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply the device referred to. Or elements must have a specific orientation, be constructed and operate in a specific orientation and therefore are not to be construed as limitations on the application.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of this application, "plurality" means two or more than two, unless otherwise explicitly and specifically limited.

Although the types and frequencies of existing filters in our country have basically satisfied all kinds of telecommunications equipment, with the development of the electronics industry, the performance requirements for filters are getting higher and higher, and the functions are becoming more and more numerous. Filters are required to develop in the direction of integration. Overall, the development of passive filters in my country is relatively slow, especially low-pass filters developed using thin-film integrated passive device (IPD) technology, which have not yet been mass-produced and applied. In order to shorten the gap with demand , it is necessary to independently develop low-pass filters based on thin-film integrated passive device technology.

RF passive components (such as resistors, inductors, capacitors, and filters) can be fabricated through a variety of processes, such as low temperature co-fired ceramics. ceramic (LTCC) technology embeds passive components into multilayer substrates. The LTCC process is widely used because of its excellent electrical and mechanical properties. Most traditional low-pass filters are made using the LTCC process. However, the size of the ceramic substrate using the LTCC process has encountered a bottleneck on the road to miniaturization.

In recent years, compared with the LTCC process and the PCB (Printed Circuit Board) process, the IPD semiconductor process can manufacture thinner line widths, high-density capacitors, high-quality factor (Q-factor) inductors and high-quality Precision inductors can use thin film integrated passive device technology to integrate various passive devices, which has far-reaching significance for achieving high integration and high performance in communication systems. In order to meet the performance requirements of low-pass filters with compact size, steep frequency cutoff characteristics and high out-of-band rejection transmission characteristics, system integration technologies such as system-in-a-package (SiP) are applied in RF systems. widely.

In this embodiment, the low-pass filter is an electronic filter device that allows signals below the cutoff frequency to pass but cannot pass signals above the cutoff frequency.

The Q value of the inductor, also called the quality factor of the inductor, is the main parameter to measure the inductor device. The inductor Q value refers to the ratio of the inductive reactance and its equivalent loss resistance when the inductor operates under an AC voltage of a certain frequency. The higher the Q value of an inductor, the smaller its losses and the higher its efficiency.

As shown in FIG. 1 , the first aspect of the embodiment of the present application provides a schematic diagram of the principle of a passive low-pass filter. For convenience of explanation, only the parts related to this embodiment are shown.

Please refer to Figure 1. The passive low-pass filter in the embodiment of the present application includes: a radio frequency input module 101, a first resonant module 103, a first attenuation module 105, a plurality of second resonant modules 104, and a plurality of second attenuation modules. 106 and RF output module 102.

In this embodiment, the radio frequency input module 101 is used to access radio frequency signals, mix and process the radio frequency signals, and output the first radio frequency signal. The first resonance module 103 is coupled to the radio frequency input module 101 and is used to process the first radio frequency signal. The frequency of the signal is adjusted to output a second radio frequency signal with a preset passband frequency; the first attenuation module 105 is coupled to the first resonance module 103 for attenuating the clutter signal in the second radio frequency signal; a plurality of series-connected The second resonant module 104 is coupled to the first resonant module 103 for adjusting the frequency of the second radio frequency signal; the first end of each second attenuation module 106 is coupled to the common ground between adjacent second resonant modules 104 node, the second end of each second attenuation module 106 is grounded, used to attenuate the clutter signal in the second radio frequency signal to generate a third radio frequency signal; the radio frequency output module is connected to multiple second resonance modules 104 connected in series, with to output the third radio frequency signal.

In this embodiment, it should be noted that the accessed radio frequency signal may include interference frequencies of various amplitudes. At the common contact point between the first resonance module 103 and the first attenuation module 105, the first attenuation module 105 will perform shunt processing on the radio frequency signal. , the first attenuation module 105 will adjust the noise signal of the second radio frequency signal output by the first resonance module 103 to quickly attenuate the noise signal at the cut-off frequency at the pole.

Further, the second radio frequency signal directly enters a plurality of second resonant modules 104, wherein the plurality of second resonant modules 104 are coupled to the first resonant module 103, and the plurality of second resonant modules 104 are used to adjust the second radio frequency signal. The frequency at which the passband frequency deviates from the preset value. Further, the first ends of the plurality of second attenuation modules 106 are coupled to a common node between adjacent second resonant modules 104 , and the second end of each second attenuation module 106 is connected to ground, for adjusting the frequency at the cut-off frequency. Other clutter frequency amplitude attenuation processing is performed to generate a third radio frequency signal; when the radio frequency signal reaches the preset signal and the clutter attenuates to the preset range, the radio frequency signal enters and is connected to multiple second resonance modules 104 connected in series. The radio frequency output module 102 is configured to output the third radio frequency signal to the coplanar port.

In one embodiment, the radio frequency input module 101 includes a radio frequency (RF) interface. The radio frequency signal accessed by the radio frequency interface can be one or more of digital analog signals, audio signals, and video signals, and the corresponding signals are mixed. The process outputs a signal frequency that meets a preset value. For example, the radio frequency interface is connected to a digital analog signal, and a stable digital analog signal is output through mixed processing at the radio frequency interface, and triggers the subsequent module to implement the corresponding function. It should be noted that the radio frequency input module 101 can also be provided with multiple other wireless interfaces, and the radio frequency interfaces can also be replaced accordingly according to the needs of the device to implement corresponding functions. The specific interface type and model are not limited.

In one embodiment, the first resonance module 103 includes at least any one of an inductive component or a capacitive component.

In this embodiment, as shown in Figure 2, the first resonant module 103 includes a first inductor L1 and a first capacitor C1. The first end of the first inductor L1 and the first end of the first capacitor C1 are commonly connected to the radio frequency input. In the module 101 , the second end of the first inductor L1 and the second end of the first inductor L1 are commonly connected to the second resonant module 104 .

In one embodiment, one of the second resonant modules 104 includes a second inductor L2 and a second capacitor C2, and the second inductor L2 and the second capacitor C2 are connected in parallel. The plurality of second resonant modules 104 include a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a first capacitor C1, a second capacitor C2, a third capacitor C3 and a fourth capacitor C4, where the inductor and capacitors are connected respectively. For example, the first end of the first capacitor C1 is connected to the RF input module 101, the second end of the first capacitor C1 is connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 The first end of the third capacitor C3 is connected to the first end of the third capacitor C3. The second end of the third capacitor C3 is connected to the first end of the fourth capacitor C4. The second end of the fourth capacitor C4 is connected to the radio frequency output module 102. The first inductor L1 is connected to the first end of the third capacitor C3. The first capacitor C1 is connected in parallel, the second inductor L2 and the second capacitor C2 are connected in parallel, the third inductor L3 and the third capacitor C3 are connected in parallel, and the fourth inductor L4 and the fourth capacitor C4 are connected in parallel.

In one embodiment, the first attenuation module 105 includes at least one capacitor, a first end of the at least one capacitor is connected to the first resonant module 103, and a second end of the at least one capacitor is connected to ground.

For example, the first attenuation module 105 includes the fifth capacitor C5, and the second attenuation module 106 includes the sixth capacitor C6 and the seventh capacitor C7. Specifically, the first end of the fifth capacitor C5 is connected to the second end of the first capacitor C1, the second end of the fifth capacitor C5 is connected to ground, and the first end of the sixth capacitor C6 is connected to the second end of the second capacitor C2. , the second terminal of the sixth capacitor C6 is connected to the ground, the first terminal of the seventh capacitor C7 is connected to the second terminal of the third capacitor C3, and the second terminal of the seventh capacitor C7 is connected to the ground.

In another embodiment, as shown in FIG. 3 , when the first resonant module 103 only includes an inductor, the inductor plays the role of communicating AC resistance and DC, and the corresponding function is realized by connecting the inductor and capacitor in parallel for the first time in this circuit. and a capacitor to ground.

In this embodiment, as shown in FIG. 3 , the first resonant module 103 includes a first inductor L1. The plurality of second resonant modules 104 include a second inductor L2, a third inductor L3, a fourth inductor L4, a first capacitor C1, a second capacitor C2 and a third capacitor C3, where the inductors and capacitors are connected correspondingly, for example, the first The first end of the inductor L1 is connected to the radio frequency input module 101, the second end of the first inductor L1 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the first end of the second capacitor C2. , the second end of the second capacitor C2 is connected to the first end of the third capacitor C3, the second end of the third capacitor C3 is connected to the radio frequency output module 102, the second inductor L2 is connected in parallel with the first capacitor C1, and the third inductor L3 The second capacitor C2 is connected in parallel, the fourth inductor L4 is connected in parallel with the third capacitor C3, the first attenuation module 105 includes the fourth capacitor C4, the second attenuation module 106 includes the fifth capacitor C5 and the sixth capacitor C6. Specifically, the fourth The first end of the capacitor C4 is connected to the first end of the first capacitor C1, the second end of the fourth capacitor C4 is connected to ground, the first end of the fifth capacitor C5 is connected to the first end of the second capacitor C2, and the fifth capacitor C5 The second terminal of the sixth capacitor C6 is connected to the ground, and the first terminal of the sixth capacitor C6 is connected to the first terminal of the third capacitor C3.

Preferably, when the first resonant module 103 is provided with only one inductor, the radio frequency signal input from the radio frequency input module 101 and the radio frequency signal passing through the inductor are first processed by the first attenuation module 105 and transmitted to the non-passband frequency loss at the pole, and then After the resonance processing of the first resonant module among the plurality of second resonant modules 104, the passband frequency is stabilized in the preset value range, so that the low-pass filter has steep cutoff frequency characteristics and good out-of-band high suppression characteristics.

Optionally, the number of resonant circuits connected in series of multiple second resonant modules 104 is selected to be connected to one or more second resonant circuits according to the effect that the device needs to achieve and the actual cost, and the specific number is not limited.

Among them, the number of attenuation circuits of the plurality of second attenuation modules 106 is selected to be connected to one or more second attenuation circuits according to the effect that the device needs to achieve and the actual cost, and the specific number is not limited.

In this embodiment, the radio frequency input module 101 also includes a plurality of through holes. When the radio frequency input module 101 includes two through holes, the two through holes are respectively connected to the ground terminal Via of the radio frequency coplanar end; wherein, the radio frequency output module When 102 includes two through holes, the two through holes are respectively connected to the ground terminal Via of the radio frequency coplanar end; wherein, the capacitors in the branch composed of the first attenuation module 105 and a plurality of second attenuation modules 106 are respectively connected to the corresponding through holes. Via, the capacitance of each branch is connected to the ground metal layer through the through hole.

Preferably, the size of the through hole on the back side of the ground is 84 ±5um. It should be noted that the size of the through hole is not limited to the size set in this embodiment. The specific size can be based on the realization of the device function and the large-scale and industrialization of the through hole. Convenient and economical angle selection for production.

In one embodiment, the first attenuation module 105 includes at least one capacitor, a first end of the at least one capacitor is connected to the first resonant module 103, and a second end of the at least one capacitor is connected to ground.

Specifically, the first end of each branch capacitor is connected to the common contact point, and the second end of each branch capacitor is connected to the ground metal layer.

In one embodiment, the first inductor L1 and the second inductor L2 are spiral inductors or rectangular inductors.

Preferably, the inductor of the passive low-pass filter is an inductor made of ring-shaped magnetic material, and the finished shape of the inductor is multiple spiral inductors or rectangular inductors. Among them, the inductor can only use ring-shaped magnetic materials and cannot use polygonal materials. When using polygonal When using different materials, the inductor made is an air-core inductor; optionally, the style of the finished product is not limited to annular or rectangular, and the specific style and shape can be set according to the size of the board and the need to realize the corresponding functions.

In one embodiment, the structure of the first capacitor C1 and the second capacitor C2 is a metal-dielectric-metal structure.

It should be noted that the dielectric layer in the middle of the capacitor can be made of different materials. Specifically, the medium includes one or more of alumina, capacitor paper, and ceramic tiles. The specific dielectric material is selected according to the functional needs and Manufacturing cost selection, the specific type is not limited.

In one embodiment, the passive low-pass filter further includes a substrate layer and a grounded metal layer;

Among them, the first resonant module 103 and the second resonant module 104 are formed on the substrate layer, and the first attenuation module 105 and the second attenuation module 106 are connected to the ground metal layer through a through-hole structure.

Specifically, the capacitors set in the low-pass filter are formed on the substrate layer using a thin-film integrated passive device (IPD) process, and are composed of top metal, bottom metal, and top metal and bottom metal. It is composed of an intermediate insulation layer.

Optionally, the underlying metal surface is embedded in a grounded metal layer to form a sheath or shielding layer, and one or more of single-point grounding, midpoint grounding, two-end grounding, and cross-interconnection are used.

Alternatively, the intermediate insulating layer may be, but is not limited to, a silicon nitride intermediate insulating layer.

In one embodiment, the substrate layer is a semiconductor material arsenide as a conductive surface layer, and the thickness of the substrate is 100±5 μm. Specifically, except that the substrate layer is a single-layer substrate, the substrate layer is a gallium arsenide (GaAs) substrate. , other semiconductor materials, such as silicon, can also be used. When the thickness of the substrate layer ≦200 μm, preferably, the thickness of the substrate layer 10 is 100 μm, but the specific substrate thickness is selected according to functional implementation.

In another embodiment, the passive low-pass filter, the substrate layer, and the ground metal layer form a passive low-pass filter chip; the length of the passive low-pass filter chip is 1.8 ±0.05mm; the passive low-pass filter chip The width is 0.9 ±0.05mm; the passive low-pass filter chip height is 0.1 ±0.05mm. By forming the low-pass filter of the above size based on the thin-film integrated passive device process, the low-pass filter is ultra-miniaturized and can be easily applied to various electronic devices that require patching.

In another embodiment, as shown in Figures 4 and 5, Figure 4 shows the input port return loss S11 and the output port return loss of a low-pass filter with a passband frequency of 0.5 GHz provided by an embodiment of the present application. A schematic diagram of the S22 parameter test curve. Figure 5 is a schematic diagram of the stopband suppression S21 parameter test curve of a low-pass filter with a passband frequency of 0.5 GHz provided by an embodiment of the present application. The input port return loss S11 of the low-pass filter is less than -16.0dB in the entire 0-0.5GHz frequency band, indicating that the loss reflected back by the low-pass filter in this embodiment after passing through the main path and each resonant branch is small and low. The filter achieves impedance matching. The stopband suppression S21 of the low-pass filter is greater than -1.82dB in the entire 0-0.5GHz frequency band, indicating that the low-pass filter has small insertion loss and good transmission characteristics. At 1.068GHz, S21＜-20dB. At 1.3GHz, S21＜-40dB indicates that the low-pass filter has a good rectangular coefficient and a steep cutoff frequency. At 1.25~8GHz, S21＜-35dB indicates low-pass filtering. The device has high out-of-band rejection characteristics.

In one embodiment, a low-pass filter circuit includes a radio frequency input module 101, a radio frequency output module 102, a plurality of resonant modules and a plurality of attenuation modules; and the radio frequency input module 101, a radio frequency output module 102, a plurality of resonant modules and Multiple attenuation modules are connected to passive low-pass filters respectively.

In the above embodiments, each embodiment is described with its own emphasis. For parts that are not detailed or documented in a certain embodiment, please refer to the relevant descriptions of other embodiments.

The above embodiments are only used to illustrate the technical solutions of the present application, but are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments. Modifications are made to the recorded technical solutions, or equivalent substitutions are made to some of the technical features; these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and shall be included in this application. within the scope of protection.

Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above functional units and circuits is used as an example. In actual applications, the above functions can be allocated to different functional units and circuits according to needs. Circuit completion means dividing the internal structure of the device into different functional units or circuits to complete all or part of the functions described above. Each functional unit and circuit in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be hardware-based. It can also be implemented in the form of software functional units. In addition, the specific names of each functional unit and circuit are only for the convenience of distinguishing each other and are not used to limit the scope of protection of the present application. For the specific working processes of the units and circuits in the above system, reference can be made to the corresponding processes in the foregoing method embodiments, which will not be described again here.

In the above embodiments, each embodiment is described with its own emphasis. For parts that are not detailed or documented in a certain embodiment, please refer to the relevant descriptions of other embodiments.

Claims (10)

1. A passive low-pass filter, characterized by including:

   A radio frequency input module is used to access radio frequency signals, mix and process the radio frequency signals, and output a first radio frequency signal;

   A first resonance module, coupled to the radio frequency input module, is used to adjust the frequency of the first radio frequency signal to output a second radio frequency signal with a preset passband frequency;

   A first attenuation module, coupled to the first resonance module, used to attenuate the clutter signal in the second radio frequency signal;

   A plurality of second resonant modules connected in series, coupled with the first resonant module, used to adjust the frequency of the second radio frequency signal;

   A plurality of second attenuation modules, the first end of each second attenuation module is coupled to a common node between adjacent second resonant modules, and the second end of each second attenuation module is grounded , used to attenuate the clutter signal in the second radio frequency signal and generate a third radio frequency signal;

   A radio frequency output module is connected to the plurality of second resonance modules connected in series and is used to output the third radio frequency signal.
2. The passive low-pass filter of claim 1, wherein the first resonant module includes a first inductor and a first capacitor, a first end of the first inductor and a third end of the first capacitor. One end is commonly connected to the radio frequency input module, and the second end of the first inductor and the second end of the first inductor are commonly connected to the second resonant module.
3. The passive low-pass filter of claim 2, wherein each second resonant module includes a second inductor and a second capacitor, and the second inductor is connected in parallel with the second capacitor.
4. The passive low-pass filter of claim 3, wherein the first attenuation module includes at least one capacitor, a first end of the at least one capacitor is connected to the first resonance module, and the at least one capacitor The second terminal of a capacitor is connected to ground.
5. The passive low-pass filter of claim 3, wherein the first inductor and the second inductor are spiral inductors or rectangular inductors.
6. The passive low-pass filter according to claim 3, wherein the structure of the first capacitor and the second capacitor is a metal-dielectric-metal structure.
7. The passive low-pass filter according to claim 1, further comprising:

   Substrate layer and ground metal layer;

   Wherein, the first resonant module and the second resonant module are formed on the substrate layer, and the first attenuation module and the second attenuation module are connected to the ground metal layer through a through-hole structure.
8. The passive low-pass filter as claimed in claim 7, characterized in that:

   The material of the substrate layer is gallium arsenide material, and the thickness of the substrate layer is 100±5 μm.
9. The passive low-pass filter of claim 8, wherein the radio frequency input module and the radio frequency output module are coplanar port structures.
10. A low-pass filter circuit, characterized by including the passive low-pass filter according to any one of claims 1 to 9.