A miniaturized four-cavity SIW filter suitable for 5G millimeter wave

Abstract

The application discloses a miniaturized four-cavity SIW filter suitable for 5G millimeter waves, which comprises a single-layer dielectric plate, the upper and lower surfaces of the single-layer dielectric plate are respectively paved with an upper metal layer and a lower metal layer, the periphery and the internal array of the single-layer dielectric plate, the upper metal layer and the lower metal layer are distributed with a plurality of metal through holes with different sizes, the upper metal layer of the single-layer dielectric plate is slotted as a coupling structure, and the left and right ends are respectively paved with input and output microstrip lines one and two used as adjustable impedance for input and output. The structure of the application is only a single-layer structure, so it has better heat dissipation, and is easy to manufacture, and the influence generated between the layers does not need to be considered too much. The passband bandwidth of the application is 5GHz, has better return loss and insertion loss indexes, and according to different application scene examples, the passband frequency can be adjusted in the range of 20-32GHz.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of filters, in particular to a miniaturized four-cavity SIW filter suitable for 5G millimeter waves. BACKGROUND

[0002] A filter is a tool that can select the frequency of a signal. Through the selection ability of the filter, people can receive or send signals carrying useful information and filter out the noise generated by the signal generator and the interference signals generated in the transmission process.

[0003] In today's rapidly developing communication industry, the frequency spectrum resources of electromagnetic waves are gradually limited. The industry has developed from the earliest 2G to the current 5G. While exploring higher frequency communication rules, the update and iteration of filters are also in full swing. From the filter of hundreds of megahertz to the current gigahertz and terahertz filter is also being developed as the frequency band continues to rise. It is particularly important to research filters with stronger filtering function and more suitable frequency band.

[0004] Compared with other types of filters, the substrate integrated waveguide (SIW) technology has the advantages of small size, low loss, easy to manufacture and the like, and stands out among a variety of filters suitable for 5G millimeter waves.

[0005] In recent years, some technical solutions suitable for 5G millimeter wave filters have been disclosed. Compared with the prior art, among them: the Chinese patent with the patent number CN113178669B discloses a "5G millimeter wave bandpass filter based on integrated substrate gap waveguide", which adopts a three-layer dielectric substrate, adds a periodic metal via in the top dielectric substrate to form an electromagnetic bandgap structure to improve the out-of-band suppression characteristics of the filter, and prints two open triangular resonators on the upper surface of the bottom dielectric plate. The opening length and width of the triangular resonator can be adjusted to adjust the filter bandwidth; the Chinese patent with the patent number CN112164846A discloses a "millimeter wave bandpass filter", which is composed of a dielectric substrate and two layers of LTCC. Two resonators composed of metalized vias are arranged on the dielectric substrate, and four resonators composed of metalized vias are arranged on the two layers of LTCC. The coupling connection between the two layers of LTCC and the dielectric substrate is realized through the inductive coupling window structure, so as to realize the filtering characteristics. However, the filters proposed in the above two prior arts have a large number of overall stack layers, high filter profile, complex structure, and need to use LTCC, HDI and surface mounting technology to realize, the processing flow is complex, the process is difficult and the cost is high. SUMMARY

[0006] Based on the technical problems existing in the background art, the application provides a miniaturized four-cavity SIW filter suitable for 5G millimeter waves.

[0007] The application provides a miniaturized four-cavity SIW filter suitable for 5G millimeter waves, which comprises a single-layer dielectric plate, the upper surface and the lower surface of the single-layer dielectric plate are respectively paved with an upper metal layer and a lower metal layer, a plurality of metal through holes with different sizes are distributed on the periphery and the internal array of the single-layer dielectric plate, the upper metal layer of the single-layer dielectric plate is slotted as a coupling structure, and the left end and the right end are respectively paved with an input-output microstrip line one and an input-output microstrip line two which are used as adjustable impedance input-output.

[0008] Preferably, the distribution of the plurality of metal through holes forms four middle cavity structures, and the four middle cavity structures are respectively a first cavity, a second metal cavity, a third metal cavity and a tail cavity.

[0009] Preferably, the input-output microstrip line one and the input-output microstrip line two are provided with two pairs of concentric double-semicircular first-end cavity coupling structures at the center positions.

[0010] Preferably, the two pairs of concentric double-semicircular first-end cavity coupling structures are arranged with the center slots of the two pairs of concentric double-semicircles being at an angle of 90 degrees.

[0011] Preferably, the metal through holes are divided into three different sizes of cylindrical metal through holes: first metal through holes, second metal through holes and third metal through holes, the first metal through holes, the second metal through holes and the third metal through holes all penetrate the upper metal layer, the lower metal layer and the single-layer dielectric layer, and the radii of the first metal through holes, the second metal through holes and the third metal through holes are 4 mil, 5 mil and 6 mil respectively.

[0012] Preferably, the input-output microstrip line one and the input-output microstrip line two are provided with four L-shaped input-output microstrip line impedance adjustment structures which are symmetrical about the center origin.

[0013] Preferably, the single-layer dielectric plate is made of Rogers4003 material, the relative dielectric constant is 3.55, and the thickness is 8 mil.

[0014] Preferably, the input-output microstrip line one and the input-output microstrip line two are both 50-ohm SIW characteristic impedance matching microstrip lines.

[0015] In the application, compared with the prior art, the application has the following advantages:

[0016] 1. The application is mainly used in the 20G-30GHz frequency band, and is less involved in the passband range of the SIW filter designed in China at present.

[0017] 2, The application uses a similar cavity filter structure for the SIW filter, divides the metal top layer into four cavities, and uses different sizes of metal cavities for filtering, which has the advantages of high out-of-band suppression and low in-band return loss;

[0018] 3, The coupling mode adopted by the application is a concentric double half moon coupling structure, which can adjust the strength of the head and tail cavity coupling through the distance between the double half circles, and can be changed according to requirements;

[0019] 4, The microstrip line of the application adopts an adjustable SIW characteristic impedance matching microstrip line, which is convenient for matching with front-end and rear-end products, and the matching impedance size can be changed by adjusting the L-shaped recess structure at both ends of the microstrip line;

[0020] 5, The application uses three different sizes of copper material through holes, which can perform electromagnetic isolation, and by using the distance between adjacent through holes and the different radii of different types of through holes, different sizes of metal cavities are designed to achieve low insertion loss filtering effect.

[0021] The structure of the application is only a single layer structure, so it has better heat dissipation and is easy to manufacture, and does not need to consider the influence between the layers. The passband bandwidth of the application is 5GHz, and the return loss and insertion loss indicators are better, and the passband frequency can be adjusted within the range of 20-32GHz according to different application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A top surface metal layer diagram of a miniaturized four-cavity SIW filter suitable for 5G millimeter waves is provided for the application;

[0023] Figure 2 A side view structure diagram of a miniaturized four-cavity SIW filter suitable for 5G millimeter waves is provided for the application;

[0024] Figure 3 A test result insertion loss and return loss indicator diagram of a miniaturized four-cavity SIW filter suitable for 5G millimeter waves is provided for the application;

[0025] Figure 4 A circuit principle diagram of a miniaturized four-cavity SIW filter suitable for 5G millimeter waves is provided for the application.

[0026] In the figure: 1 first cavity, 2 second metal cavity, 3 third metal cavity, 4 tail cavity, 5 first metal through hole, 6 second metal through hole, 7 third metal through hole, 8 head and tail cavity coupling structure, 9 input and output microstrip line one, 10 L-shaped input and output microstrip line impedance adjustment structure, 11 input and output microstrip line two, 12 metal through hole, 13 upper metal layer, 14 lower metal layer. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0028] Referring to Figures 1-4 A miniaturized four-cavity SIW filter suitable for 5G millimeter waves comprises a single-layer dielectric plate, the upper and lower surfaces of the single-layer dielectric plate are respectively paved with an upper metal layer 13 and a lower metal layer 14, the periphery of the single-layer dielectric plate, the upper metal layer 13 and the lower metal layer 14 and the internal array distribution thereof are provided with a plurality of metal through holes 12 of different sizes, the upper metal layer 13 of the single-layer dielectric plate is slotted as a coupling structure, and the left and right ends are respectively paved with an input-output microstrip line 1 and an input-output microstrip line 2 serving as adjustable impedance for input and output.

[0029] In the present application, the distribution of the plurality of metal through holes 12 forms four middle cavity structures, the four middle cavity structures are respectively a first cavity 1, a second metal cavity 2, a third metal cavity 3 and a tail cavity 4, the four cavities do not adopt an absolute symmetrical structure, the size of each cavity unit can be adjusted according to the required bandwidth and frequency, and symmetry is not required.

[0030] In the present application, the center positions of the input-output microstrip line 1 and the input-output microstrip line 2 are provided with two pairs of concentric double-semicircular first-end cavity coupling structures 8.

[0031] In the present application, the two pairs of concentric double-semicircular first-end cavity coupling structures 8 are provided with two pairs of concentric double-semicircles, the center slots of the two pairs of concentric double-semicircles are mutually at an angle of 90°, and the coupling strength is enhanced or weakened by changing the spacing of the two pairs of concentric double-semicircles, thereby affecting the out-of-band suppression capability of the filter.

[0032] In the present application, the metal through holes 12 are divided into three different sizes of cylindrical metal through holes: first metal through holes 5, second metal through holes 6 and third metal through holes 7, the first metal through holes 5, the second metal through holes 6 and the third metal through holes 7 all penetrate the upper metal layer 13, the lower metal layer 14 and the single-layer dielectric layer, the radii of the first metal through holes 5, the second metal through holes 6 and the third metal through holes 7 are 4 mil, 5 mil and 6 mil respectively, the third metal through holes 7 are used to change the sizes of the first cavity and the second metal cavity, and the sizes of the tail cavity and the third metal cavity, the second metal through holes 6 are used to change the sizes of the second metal cavity and the third metal cavity, and the first metal through holes 5 are used to determine the size of the whole cavity and are distributed around the whole product.

[0033] In the present application, the input-output microstrip line 1 and the input-output microstrip line 2 are provided with four L-shaped input-output microstrip line impedance adjustment structures 10 which are symmetrical about the center origin, and the structure is used for adjusting the impedance matching of input and output.

[0034] In the application, the single-layer dielectric plate is Rogers 4003 material, the relative dielectric constant is 3.55, and the thickness is 8 mil.

[0035] In the application, the input-output microstrip line one 9 and the input-output microstrip line two 11 are both 50-ohm SIW characteristic impedance matching microstrip lines.

[0036] 1 first cavity, 2 second metal cavity, 3 third metal cavity, 4 tail cavity, 5 first metal via, 6 second metal via, 7 third metal via, 8 head-tail cavity coupling structure, 9 input-output microstrip line one, 10 L-shaped input-output microstrip line impedance adjustment structure, 11 input-output microstrip line two, 12 metal via, 13 upper metal layer, 14 lower metal layer

[0037] The structure of the application takes the structure of four cavities composed of the metal via 12 and the upper metal layer 13 and the lower metal layer 14 as a basic unit, uses the first metal via 5 as a peripheral electromagnetic shielding structure to surround the entire product, uses the third metal via 7 and the second metal via 6 as an internal electromagnetic shielding structure to guide the current flow, and cooperates with the first metal via 5 to hinder the circulation of low-frequency signals, thereby forming a structure similar to a cavity filter, so that the current flow sequence is that the current flows from the input-output microstrip line one 9 into the input impedance line, flows into the second metal cavity 2 through the first cavity 1, then flows into the third metal cavity 3, and finally flows into the tail cavity 4 and then flows out of the output impedance line through the input-output microstrip line two 11.

[0038] As shown in Figure 1 , the input-output microstrip line one 9 and the input-output microstrip line two 11 are input-output impedance lines, and the L-shaped input-output microstrip line impedance adjustment structure 10 is an L-shaped impedance adjustment structure, in this example, the impedance satisfies 50 ohms, which is convenient for matching other front-end and back-end products.

[0039] As shown in Figure 1 , because the application in this example is adjustable within the 23-30GHz frequency band, the center frequency 26GHz is taken, the size range of each cavity is calculated, and the following formula is used to calculate:

[0040]

[0041] Where f0 is the center frequency, c0 is the speed of light in vacuum, ε r is the relative dielectric constant, and is the length and width of each cavity, which is calculated by the following formula:

[0042]

[0043] Where d is the diameter of the metal via 5, and p is the distance between two metal vias 5.

[0044] According to the calculation, the length and width of the cavity with the center frequency of 26G are 152mil and 148mil respectively. In order to obtain the passband of 24GHz-27GHz, the length and width of the cavity need to be further slightly changed in the debugging.

[0045] As shown in Figure 1 The head-tail cavity coupling structure 8 of the present application is a coaxial double semi-circular ring structure, and the openings of the inner and outer semi-circular rings are 90° to each other. The structure can enhance the coupling between the head and tail cavities, so that there is good return loss and insertion loss in the passband. By adjusting the size of the structure, in combination with the radius D and the spacing p of the metal through hole, the slight change of the passband bandwidth can be realized. The change can reach 500MHz, which can be suitable for the needs of different environments.

[0046] As shown in Figure 1 The present application is not a completely symmetrical structure. According to the passband and the frequency requirement of each cavity, the length and width of each cavity can have a slight difference. In the present example, the length L1 is 152mil, the length L2 is 148mil, the width W1 is 147mil, and the width W2 is 149mil. The data is obtained by debugging.

[0047] As shown in Figure 2 The present application can achieve the purpose of the application with the center frequency of 26GHz, the insertion loss is less than-1.5dBm, and the return loss is greater than 14dBm.

[0048] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A miniaturized four-cavity SIW filter suitable for 5G millimeter wave, characterized in that, The device comprises a single-layer dielectric substrate, on the upper and lower surfaces of which are respectively covered with an upper metal layer (13) and a lower metal layer (14). Multiple metal vias (12) of different sizes are arrayed around and inside the single-layer dielectric substrate, the upper metal layer (13), and the lower metal layer (14). The upper metal layer (13) of the single-layer dielectric substrate has slots as a coupling structure, and input / output microstrip lines 1 (9) and 2 (11) for adjustable impedance are respectively laid at its left and right ends. The distribution of the multiple metal vias (12) forms four cavity structures: a first cavity (1), a second metal cavity (2), a third metal cavity (3), and a tail cavity (4). The input / output microstrip line 1 (9)... Two pairs of concentric double semicircular head-and-tail cavity coupling structures (8) are provided at the center of the input and output microstrip line 2 (11). The central slots of the two pairs of concentric double semicircles of the two pairs of concentric double semicircular head-and-tail cavity coupling structures (8) are at a 90° angle to each other. The metal through holes (12) are divided into three types of cylindrical metal through holes of different sizes: first metal through hole (5), second metal through hole (6) and third metal through hole (7). The first metal through hole (5), second metal through hole (6) and third metal through hole (7) all penetrate the upper metal layer (13) and the lower metal layer (14) and the single-layer dielectric layer. The radius dimensions of the first metal through hole (5), second metal through hole (6) and third metal through hole (7) are 4mil, 5mil and 6mil, respectively.

2. A miniaturized four-cavity SIW filter suitable for 5G millimeter wave according to claim 1, characterized in that, The input / output microstrip line one (9) and input / output microstrip line two (11) are provided with four L-shaped input / output microstrip line impedance adjustment structures (10) symmetrical about the central origin.

3. A miniaturized four-cavity SIW filter suitable for 5G millimeter wave according to claim 1, characterized in that, The single-layer dielectric substrate is made of Rogers 4003 material, with a relative permittivity of 3.55 and a thickness of 8 mil.

4. A miniaturized four-cavity SIW filter suitable for 5G millimeter wave according to claim 1, characterized in that, Both the input / output microstrip line one (9) and the input / output microstrip line two (11) are 50-ohm SIW characteristic impedance matched microstrip lines.

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