Filter

Abstract

The utility model discloses a filter, relates to the related technical field of microwave transmission, and is used for solving the technical problem that the existing filter has overlarge insertion loss in high frequency, especially millimeter wave and millimeter wave frequency bands. The filter provided by the utility model comprises an insulating substrate which comprises a body and a supporting table, the body is provided with a first surface and a second surface which are oppositely arranged in a third direction, the first surface is provided with a groove, and the groove is provided with a first side wall and a second side wall which are oppositely arranged in a first direction; the transmission lines comprise a first transmission line and a plurality of second transmission lines which are arranged on the supporting part; and the conductive layer comprises a first conductive layer arranged on the first side wall and a second conductive layer arranged on the second side wall.

Description

Technical Field

[0001] The utility model relates to the technical field related to microwave transmission technology, in particular to a filter. Background Art

[0002] In various systems for receiving and transmitting microwaves, filters, as a device with frequency selection function, can select useful frequency signals from many stray microwave frequencies. Its performance is directly related to the performance of the transceiver system.

[0003] In the field of microwave communication, with the rapid expansion of the scope of application, the limited electromagnetic spectrum is becoming increasingly crowded. High frequencies, especially millimeter waves and above, are receiving attention from the industry due to their rich spectrum resources. However, as the frequency increases, the loss of transmission lines, dielectric losses, and parasitic effects of devices will increase significantly, and the overall performance of the corresponding devices will decrease. As a key component of microwave communication systems, filters play a vital role. Therefore, how to provide a high-performance and miniaturized microwave high-frequency filter is an urgent problem to be solved. Utility Model Content

[0004] The utility model provides a filter, which can not only complete the filtering and frequency selection function, but also solve the problem of large insertion loss of existing high-frequency filters, especially millimeter wave and above millimeter wave frequency bands.

[0005] To achieve the above-mentioned purpose, the filter provided in the present application has a first direction, a second direction and a third direction intersecting in pairs, and the filter includes:

[0006] An insulating substrate, comprising a body and a support platform, wherein the body has a first surface and a second surface arranged opposite to each other in a third direction, the first surface is provided with a groove, and the groove has a first side wall and a second side wall arranged opposite to each other in the first direction;

[0007] A transmission line, comprising a first transmission line and a plurality of second transmission lines disposed on the support portion, wherein the plurality of second transmission lines are coupled to the first transmission line;

[0008] The conductive layer includes a first conductive layer disposed on the first side wall and a second conductive layer disposed on the second side wall.

[0009] In some embodiments of the present application, the filter further includes:

[0010] A conductive cover plate covers the first surface and is enclosed by the body to form a cavity. There are gaps between the first transmission line and the plurality of second transmission lines and the conductive cover plate.

[0011] In some embodiments of the present application, the support platform has a first protrusion and a second protrusion arranged opposite to each other in the second direction, and the first end of the first transmission line is arranged on the first protrusion, and the second end of the first transmission line is arranged on the second protrusion.

[0012] In some embodiments of the present application, the support platform is disposed in the groove, the support platform extends along the second direction, and the height of the support platform does not exceed the depth of the groove.

[0013] In some embodiments of the present application, a wall surface of the support platform facing away from the groove bottom of the groove is closer to the second surface than the first surface.

[0014] In some embodiments of the present application, the conductive cover plate extends along a first direction and a second direction on the first surface, and a wall surface of the conductive cover plate facing the first surface is a flat surface and is in contact with the first surface.

[0015] In some embodiments of the present application, the plurality of second transmission lines are arranged in parallel with each other, and each second transmission line is perpendicular to the first transmission line.

[0016] In some embodiments of the present application, the first transmission line and the plurality of second transmission lines are electrically connected.

[0017] In some embodiments of the present application, the plurality of second transmission lines constitute a plurality of identical or different resonance units, and the intervals between each second transmission line may be equal or unequal.

[0018] In some embodiments of the present application, the distances between the surfaces of the support platform, the first protruding portion, and the second protruding portion facing away from the groove and the bottom of the groove are the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 is a structural schematic diagram of a filter provided in an embodiment of the present application;

[0021] Figure 2 This is a front view of a filter provided in an embodiment of the present application;

[0022] Figure 3 is a top view of a filter provided in an embodiment of the present application;

[0023] Figure 4 shows a schematic diagram of an 8th order LC filter;

[0024] Figure 5 is a schematic diagram of an 8th-order filter provided in an embodiment of the present application;

[0025] Figure 6 is a frequency response curve diagram of a filter provided in an embodiment of the present application;

[0026] Figure 7 It is a partial enlarged view of the filter frequency response curve provided in the embodiment of the present application.

[0027] The main reference numerals in the drawings of this application specification are described as follows:

[0028] 1-insulating substrate; 100-body; 101-support platform; 1011-first protruding portion; 1012-second protruding portion; 102-first surface; 103-second surface; 104-groove; 105-first side wall; 106-second side wall;

[0029] 2-conductive cover; 200-cavity;

[0030] 3-transmission line; 300-first transmission line; 3001-first end of the first transmission line (300); 3002-second end of the first transmission line (300); 301-second transmission line;

[0031] 4-conductive layer; 401-first conductive layer; 402-second conductive layer. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0033] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0035] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. In order to facilitate the understanding of the technical solution of this application, some of the terms involved in this application are first explained.

[0036] As mentioned above, in the field of microwave communications, the limited electromagnetic spectrum is becoming increasingly crowded, which puts forward a series of higher requirements for filters. For an ideal filter, on the one hand, it needs to have more accurate frequency selection capabilities (i.e., high performance) to accurately separate the required frequency signals from the extremely dense and complex spectrum and reduce interference and errors; on the other hand, it also needs to have lower insertion loss to ensure that the energy loss of the signal is minimized when passing through the filter, maintaining the strength and quality of the signal.

[0037] However, the components inside the traditional LC filter, such as inductors and capacitors, may have parasitic resistance to high-frequency signals, causing energy to be dissipated in the form of heat, thereby generating losses. The existing microstrip filter, as a low-profile filter structure, can solve some of the problems brought by the traditional LC filter. However, the surface current of the existing microstrip filter is mainly concentrated on the lower surface of the microstrip line conductor, and the roughness of the lower surface of the microstrip line is often large due to the requirements of the printing process, which makes the surface current of the microstrip line very uneven during transmission, resulting in large conductor losses, which is contrary to the requirements of the idealized filter.

[0038] Therefore, existing filters, whether traditional LC filters or microstrip filters, will often suffer from problems such as signal distortion during transmission due to excessive losses at high frequencies, especially above the millimeter wave and millimeter wave bands. In order to solve the above problems, the present application provides a filter that not only has excellent frequency selection capabilities, but also ensures that the filter can transmit signals under low loss conditions. Below, the technical solution of the present application is described in detail. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments of the present application. In the following embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0039] refer to Figure 1 The filter provided in the present application has a first direction X, a second direction Y and a third direction Z that intersect each other. The filter includes an insulating substrate 1, a conductive cover plate 2, a transmission line 3, and a conductive layer 4.

[0040] The insulating substrate 1 includes a body 100 and a support platform 101. The body 100 has a first surface 102 and a second surface 103 opposite to each other in a third direction Z. A groove 104 is provided on the first surface 102. The groove 104 also has a first side wall 105 and a second side wall 106 opposite to each other in the first direction X.

[0041] The transmission line 3 includes a first transmission line 300 and a plurality of second transmission lines 301 disposed on the support platform 101 .

[0042] The conductive layer 4 includes a first conductive layer 401 disposed on the first side wall 105 and a second conductive layer 402 disposed on the second side wall 106 .

[0043] It can be understood that in the third direction Z, the wall surface of the support platform 101 facing away from the groove bottom is closer to the second surface 103 relative to the first surface 102, and it can also be understood that the support platform 101 is disposed in the groove 104 and does not extend out of the groove 104. Therefore, in the third direction Z, the height of the support platform 101 does not extend beyond the depth of the groove 104.

[0044] It can be understood that the second transmission line 301 is a branch waveguide, including multiple branches. Figure 1Only four branches are shown, and each branch is parallel to each other and perpendicularly arranged on one side of the transmission line 300 and extends along the first direction X. The above-mentioned multiple branch waveguides are equivalent to multiple waveguide resonators (also called resonance units), and the waveguide resonator can be regarded as an equivalent LC series resonant circuit. The filtering effect of signals of different frequencies can be achieved by adjusting the size, shape and material of the transmission line 301. Its principle is similar to changing the filtering characteristics by adjusting the capacitance and inductance values ​​in the LC filter. Among them, multiple transmission lines 301 are coupled with the transmission line 300, that is, the above-mentioned multiple transmission lines 301 are electrically connected to the above-mentioned transmission line 300, or the above-mentioned multiple transmission lines 301 and the above-mentioned transmission line 300 are not directly connected, and capacitive coupling is achieved through inter-line capacitance. The above-mentioned multiple transmission lines 301 are arranged on one side or both sides of the transmission line 300 in parallel with each other, and are perpendicular or approximately perpendicular to the transmission line 300.

[0045] Further references Figure 1 and Figure 2 The filter further includes a conductive cover plate 2, which is disposed on the first surface 102 and encloses the body 100 of the insulating substrate 1 to form a cavity. There is a gap between the first transmission line 300 and the second transmission line 301 and the conductive cover plate 2, that is, neither of them is in contact with the conductive cover plate 2.

[0046] In this technical solution, the present application provides a support platform 101 extending along the third direction Z in the groove 104 of the main body 100. Accordingly, the specific structure of the transmission line 3 and the specific structure of the support platform 101 are adapted to each other, so that the support platform 101 can also provide an effective transmission path for the transmission line 3. Based on the above-mentioned setting of the support platform 101 and the transmission line 3, when transmitting signals, most of the electric field is mainly concentrated on both sides of the transmission line 3 and in the air cavity with a height of H formed by the conductive cover plate 2 and the insulating substrate 1, and only a small part of the electric field is distributed in the insulating substrate 1, that is, when transmitting signals, most of the electric field is bound in the air, which greatly reduces the transmission loss.

[0047] Continue to refer Figure 2 The wall surface of the conductive cover plate 2 facing the first surface 102 is a flat surface and fits with the first surface 102, thereby ensuring that the structure of the conductive cover plate 2 is a simple flat plate structure, which is easy to process.

[0048] Continue to refer Figure 1 and Figure 3, the support platform 101 has a first protruding portion 1011 and a second protruding portion 1012 in the second direction Y. The first end 3001 of the transmission line 300 is arranged on the first protruding portion 1011, and the second end 3002 of the transmission line 300 is arranged on the second protruding portion 1012. It can also be understood that the first protruding portion 1011 and the second protruding portion 1012 are used to limit the position of the transmission line 300 on the support platform 101, that is, the transmission line 300 extends from the first protruding portion 1011 to the second protruding portion 1012 in the second direction Y.

[0049] It can be understood that the distances between the surfaces of the support platform 101 , the first protruding portion 1011 and the second protruding portion 1012 facing away from the groove 104 and the bottom of the groove 104 are the same.

[0050] The principle diagram of the filter provided by the present application is described in detail below in conjunction with the accompanying drawings.

[0051] Figure 4 According to the present application, a schematic diagram of an LC filter is provided.

[0052] It should be understood that the filtering principle of the LC filter is based on the impedance characteristics of inductance and capacitance to signals of different frequencies, and the filtering effect of a specific frequency signal is achieved by designing a series circuit or a parallel circuit of capacitors and inductors.

[0053] like Figure 4 As shown, Figure 4 An 8th order low pass filter is shown. Among them, inductor L3 and capacitor C3 are connected in parallel, inductor L5 and capacitor C5 are connected in parallel, and inductor L7 and capacitor C7 are connected in parallel. Capacitor C2, capacitor C4, capacitor C6, and capacitor C8 are connected in parallel with inductor L1 in series, and inductor L3 and capacitor C3 are connected in parallel with inductor L1 and capacitor C4 in series, inductor L5 and capacitor C5 are connected in parallel with inductor L1 and capacitor C6 in series, and inductor L7 and capacitor C7 are connected in parallel with inductor L1 and capacitor C8 in series. It can be seen that capacitors and inductors are connected in series in the circuit in sequence to form one or more series resonant circuits, and capacitors and inductors are connected in parallel in the circuit in sequence to form one or more parallel resonant circuits. Furthermore, according to the response characteristics of inductors and capacitors to signals of different frequencies, the filtering function is realized. For low frequency signals, due to the large impedance of multiple inductors and small impedance of capacitors, the 8th order low pass filter has a good passing capacity for them. For high-frequency signals, the 8th-order low-pass filter has a good blocking ability due to the small capacitance impedance and large inductance impedance.

[0054] based on Figure 5 The filtering principle of the 8th-order low-pass filter, Figure 5 The filter provided by the present application is shown. Figure 5 As shown by Figure 1 The structural alternative shown Figure 4The inductors and capacitors in the figure form an 8th order low pass filter, namely 401 to 408 in the figure, which are connected in series to form an 8th order low pass filter.

[0055] like Figure 1 As shown in the figure, a plurality of transmission lines 301 are arranged vertically or approximately vertically on one side of the transmission line 300, which are arranged parallel to each other and are equally spaced. The plurality of transmission lines 301 are equivalent to a plurality of waveguide resonators (also called resonance units), and the waveguide resonator can be regarded as an equivalent LC series resonant circuit. The filtering effect of signals of different frequencies can be achieved by adjusting the size, shape and material of the transmission line 301. The principle is similar to changing the filtering characteristics by adjusting the capacitance and inductance values ​​in the LC filter.

[0056] It is understandable that the above Figure 5 Ports 1 and 2 of the 8th-order low-pass filter shown can be directly cascaded with a transmission line of similar structure in an integrated circuit without the need for an additional switching structure. At the same time, the air cavity structure of the filter ensures a certain degree of isolation when cascaded with other active and passive devices, improves the transmission quality of the signal, increases the stability of the filter, and thus improves the performance of the microwave communication system.

[0057] It can be understood that the transmission coefficient between the two ports of the filter and the reflection coefficient of each port are both important parameters of the filter. Among them, the transmission coefficient between the two ports refers to the ratio between the output signal and the input signal, which is used to describe the frequency selection effect of the filter on the signal and is a functional parameter of the filter. The transmission coefficient of an ideal filter in the passband should be 1, that is, the amplitude of the output signal is equal to the amplitude of the input signal. The reflection coefficient is a performance parameter that reflects the degree of impedance matching of each port of the filter. In the filter, the reflection coefficient is usually related to the impedance matching characteristics of the filter. The reflection coefficient of each port of the ideal filter should be 0, that is, there is no signal reflection. In practical applications, due to various factors such as the design and manufacturing process of the filter, the transmission coefficient of the filter in the passband cannot be 1 and the port reflection coefficient cannot be 0.

[0058] refer to Figure 6 and Figure 7 , Figure 6 According to an embodiment of the present application, a schematic diagram of a frequency response curve of a filter is shown. Figure 7 for Figure 6 A partial enlarged view of the filter transmission coefficient curve with the horizontal axis at 15GHz-22GHz. Among them, S1.1 is the reflection coefficient of the filter port, and S2.1 is the transmission coefficient between the two ports of the filter. The horizontal axis represents the frequency in GHz; the vertical axis is the dB number of the scattering coefficient.

[0059] refer to Figure 6, it can be seen from S2.1 that in the 15GHz-22GHz passband, the transmission coefficient between the two ports of the filter is close to 1. At the same time, it can be seen from S1.1 that the port reflection coefficient is less than -30dB in the passband, which meets the requirements of microwave communication systems in the millimeter wave and above frequency bands, and has broad application prospects in microwave communications in the millimeter wave and above frequency bands. Specifically, refer to Figure 7 The M1 point in Figure 7 The horizontal coordinate corresponding to the point M1 is 22GHz, and the vertical coordinate is -0.3dB, that is, in the 15GHz-22GHz passband, the filter insertion loss is less than 0.3dB. Therefore, when filtering at high frequencies, especially millimeter waves and above, the filter provided by the present application has low insertion loss.

[0060] It can be understood that when the filter provided by the present application performs signal filtering operations, not only the energy loss is relatively low, which is conducive to maintaining the strength and quality of the signal, but also the required frequency range can be accurately selected to effectively filter out clutter and interference signals, thereby improving the performance of the entire microwave communication system. Furthermore, the filter provided by the present application adopts a planar circuit structure, which has the advantages of compact structure and easy integration. This makes the filter provided by the present application have broad application prospects in miniaturized, high-performance communication and radar systems, helps to realize the compact design of the filter, and is easier to integrate with other circuit elements and systems, thereby reducing the complexity of design and manufacturing.

[0061] It should be noted that, for the sake of convenience in description, the aforementioned method embodiments are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described order of actions, because according to the present invention, certain steps can be performed in other orders or simultaneously.

[0062] In summary, although the present application has been disclosed as above with preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Ordinary technicians in this field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined in the claims.

Claims

1. A filter, characterized in that: Having a first direction (X), a second direction (Y) and a third direction (Z) intersecting each other, the filter comprises: An insulating substrate (1) comprises a body (100) and a support platform (101), wherein the body (100) has a first surface (102) and a second surface (103) arranged opposite to each other in a third direction (Z), the first surface (102) is provided with a groove (104), and the groove (104) has a first side wall (105) and a second side wall (106) arranged opposite to each other in a first direction (X); A transmission line (3), comprising a first transmission line (300) and a plurality of second transmission lines (301) arranged on the support platform (101), wherein the plurality of second transmission lines (301) are coupled to the first transmission line (300); The conductive layer (4) comprises a first conductive layer (401) arranged on the first side wall (105) and a second conductive layer (402) arranged on the second side wall (106).

2. The filter according to claim 1, characterized in that Also includes: A conductive cover plate (2) covers the first surface (102) and encloses the body (100) to form a cavity (200), and there is a gap between the first transmission line (300) and the plurality of second transmission lines (301) and the conductive cover plate (2).

3. The filter according to claim 1, characterized in that The support platform (101) has a first protruding portion (1011) and a second protruding portion (1012) arranged opposite to each other in a second direction (Y), and the first end (3001) of the first transmission line (300) is arranged on the first protruding portion (1011), and the second end (3002) of the first transmission line (300) is arranged on the second protruding portion (1012).

4. The filter according to claim 1, characterized in that The support platform (101) is arranged in the groove (104), the support platform (101) extends along the second direction (Y), and the height of the support platform (101) does not exceed the depth of the groove (104).

5. The filter according to claim 1, characterized in that The wall surface of the support platform (101) facing away from the groove bottom of the groove (104) is closer to the second surface (103) relative to the first surface (102).

6. The filter according to claim 2, characterized in that The conductive cover plate (2) extends on the first surface (102) along a first direction (X) and a second direction (Y); the wall surface of the conductive cover plate (2) facing the first surface (102) is a flat surface and is in contact with the first surface (102).

7. The filter according to claim 1, characterized in that The plurality of second transmission lines (301) are arranged in parallel with each other, and each second transmission line (301) is perpendicular to the first transmission line (300).

8. The filter according to claim 1, characterized in that The first transmission line (300) and the plurality of second transmission lines (301) are electrically connected.

9. The filter according to claim 1, characterized in that The plurality of second transmission lines (301) form a plurality of identical or different resonance units, and the intervals between each second transmission line (301) may be equal or unequal.

10. The filter according to claim 3, characterized in that The distances between the surfaces of the support platform (101), the first protruding portion (1011) and the second protruding portion (1012) facing away from the groove (104) and the bottom of the groove (104) are the same.

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