A glass substrate based multi-branch resonator microstrip dual-band filter

Abstract

The application discloses a kind of glass substrate-based multi-branch resonator microstrip double-passband filter, form two mouth-shaped frame loop resonances in the metal of only one side of glass substrate;First pair of parallel coupling line section, first transmission line section, second pair of parallel coupling line section, second transmission line section constitute the first mouth-shaped frame loop resonance;Second pair of parallel coupling line section, third transmission line section, third pair of parallel coupling line section, fourth transmission line section constitute the second mouth-shaped frame loop resonance;The two mouth-shaped frame loop resonances are axisymmetric with second pair of parallel coupling line section.The two mouth-shaped frame loop resonances and double-microstrip line branch jointly generate two resonance points to form two passbands;The other side metal of glass substrate is as reference ground.The circuit structure of the application is simple, easy to manufacture, and has superior performance.The application uses glass substrate, and does not need metallized via.

Description

Technical Field

[0001] This invention relates to a dual-passband filter. Background Technology

[0002] Filters are key components in radio frequency microwave circuits and communication systems, playing a crucial role in filtering out noise and retaining useful signals. Their performance directly determines the overall performance of the communication system. Without compromising performance, filters are evolving towards lower cost, lighter weight, smaller size, and better compatibility. Dual-passband filters represent a promising direction. Chinese invention patent applications CN115425377A (published December 2, 2022), entitled "A Dual-Passband Balanced Filter Based on Square Ring Loading," and CN115425376A (published December 2, 2022), entitled "A Dual-Passband Filter Based on Stub Loading," describe two different types of dual-passband filters, both requiring very complex circuit architectures to implement.

[0003] Currently, the mainstream technology for dual-passband filters uses organic material substrates. In the radio frequency field, organic material substrates have a low dielectric constant, making them less suitable for miniaturization compared to glass substrates. Glass substrates, on the other hand, are fabricated using wafer fabrication methods, making them easier to integrate than organic material substrates. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dual-passband filter. On the one hand, it adopts a simple and easy-to-process structure to achieve miniaturization. On the other hand, it adopts a glass substrate and a single-layer design, which eliminates the need to process metallized vias in the glass substrate, thus overcoming the difficulty of forming metallized vias in the glass substrate.

[0005] To address the aforementioned technical problems, this invention proposes a multi-stub resonator microstrip dual-passband filter based on a glass substrate. Two U-shaped loop resonators are formed in the metal on only one side of the glass substrate. A first pair of parallel coupled lines, a first transmission line, a second pair of parallel coupled lines, and a second transmission line constitute the first U-shaped loop resonator. A second pair of parallel coupled lines, a third transmission line, a third pair of parallel coupled lines, and a fourth transmission line constitute the second U-shaped loop resonator. The loop resonators of the two U-shaped structures are axially symmetrical about the second pair of parallel coupled lines. In this configuration, the first pair of parallel coupled line segments, the second pair of parallel coupled line segments, and the third pair of parallel coupled line segments are parallel to each other; the first transmission line segment and the fourth transmission line segment are on a straight line, referred to as the first straight line; the first straight line is perpendicular to the first pair of parallel coupled line segments; the second transmission line segment and the third transmission line segment are on a straight line, referred to as the second straight line; the second straight line is perpendicular to the first pair of parallel coupled line segments; the first pair of parallel coupled line segments, the second pair of parallel coupled line segments, and the third pair of parallel coupled line segments constitute a dual microstrip line stub. The first pair of parallel coupled line segments and the third pair of parallel coupled line segments resonate at a first frequency, and the second pair of parallel coupled line segments resonates at a second frequency; the loop resonance of the two U-shaped structures and the dual microstrip line stubs together generate two resonant points, forming two passbands; the metal on the other side of the glass substrate serves as a reference ground.

[0006] Furthermore, the first and second parallel coupling line segments constitute the first pair of parallel coupling line segments; the third and fourth parallel coupling line segments constitute the second pair of parallel coupling line segments; and the fifth and sixth parallel coupling line segments constitute the third pair of parallel coupling line segments.

[0007] Furthermore, the two ends of the first transmission line segment are respectively connected to the first end of the second coupling line segment and the first end of the sixth transmission line segment, and the second end of the second coupling line segment is open.

[0008] Furthermore, the two ends of the second transmission line section are respectively connected to the first end of the first coupling line section and the first end of the fifth transmission line section. The first end of the first coupling line section is also connected to port one, and the second end of the first coupling line section is open.

[0009] Furthermore, the two ends of the third transmission line section are respectively connected to the first end of the sixth coupling line section and the first end of the fifth transmission line section, while the second end of the sixth coupling line section is open.

[0010] Furthermore, the two ends of the fourth transmission line section are respectively connected to the first end of the fifth coupling line section and the first end of the sixth transmission line section. The first end of the fifth coupling line section is also connected to port two, and the second end of the fifth coupling line section is open.

[0011] Furthermore, the first transmission line segment and the fourth transmission line segment are sandwiched together and connected to the first end of the sixth transmission line segment. The second end of the sixth transmission line segment is connected to the first end of the fourth coupling line segment, and the second end of the fourth coupling line segment is open.

[0012] Furthermore, the second transmission line segment and the third transmission line segment are sandwiched together and connected to the first end of the fifth transmission line segment. The second end of the fifth transmission line segment is connected to the first end of the third coupling line segment, and the second end of the third coupling line segment is open.

[0013] Furthermore, either port one or port two can be used as an input port, and the other as an output port.

[0014] Furthermore, the first pair of parallel coupling line segments and the third pair of parallel coupling line segments are axially symmetric with respect to the second pair of parallel coupling line segments.

[0015] The technical advantages achieved by this invention are as follows: First, the circuit structure of this invention is simple and easy to manufacture, and the resulting dual-passband filter exhibits superior performance. Second, this invention utilizes a glass substrate, which offers significant advantages for filter miniaturization and low-loss design. Currently, the main challenge with glass substrates is the use of metallized vias, preventing their widespread application in radio frequency communication systems. This invention employs a single-layer metal design, eliminating the need for metallized vias to achieve dual-band filter functionality. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the glass substrate material used in the fabrication of microstrip filters in this invention.

[0017] Figure 2 This is a schematic diagram of the structure of the microstrip dual-passband filter based on a glass substrate multi-stub resonator according to the present invention.

[0018] Figure 3 yes Figure 2 A simplified circuit structure diagram.

[0019] Figure 4 This is a schematic diagram of the S-parameter measurement results of the present invention.

[0020] The following are the annotations in the figure: 1 is port one, 2 is port two, 11 is the first coupling line segment, 12 is the second coupling line segment, 13 is the first transmission line segment, 14 is the second transmission line segment, 15 is the third coupling line segment, 16 is the fifth transmission line segment, 21 is the fifth coupling line segment, 22 is the sixth coupling line segment, 23 is the third transmission line segment, 24 is the fourth transmission line segment, 25 is the fourth coupling line segment, 26 is the sixth transmission line segment, 90 is the upper metal cladding layer, 92 is the glass layer, and 94 is the lower metal cladding layer. Detailed Implementation

[0021] Please see Figure 1 The glass substrate material used in this invention for fabricating the microstrip filter comprises three layers: a glass layer 92 in the middle, a metal upper cladding layer 90 on one side of the glass layer 92, and a metal lower cladding layer 94 on the other side of the glass layer 92. The multi-stub resonator microstrip dual-passband filter structure proposed in this invention is... Figure 1 The invention is fabricated on a glass substrate material as shown. Specifically, the invention involves forming a single layer of metal within the glass substrate material. Figure 2 The circuit structure shown uses another metal layer of the glass substrate material as a reference ground, thus eliminating the need to form metal vias in the glass layer 92. For example, the circuit structure can be formed in the upper metal cladding layer 90, with the lower metal cladding layer 94 serving as the reference ground; alternatively, the two can be interchanged.

[0022] Please see Figure 2 The circuit structure of the multi-stub resonator microstrip dual-passband filter formed in only one side of the metal of the glass substrate material according to the present invention is as follows: A first pair of parallel coupling segments 11 and 12, which are substantially parallel to each other, constitute a first pair of parallel coupling segments. A second pair of parallel coupling segments 15 and 25, which are substantially parallel to each other, constitute a second pair of parallel coupling segments. A third pair of parallel coupling segments 21 and 22, which are substantially parallel to each other, constitute a third pair of parallel coupling segments. The first pair of parallel coupling segments, the second pair of parallel coupling segments, and the third pair of parallel coupling segments remain substantially parallel to each other.

[0023] The two ends of the first transmission line segment 13 are respectively connected to the first end of the second coupling line segment 12 and the first end of the sixth transmission line segment 26, and the second end of the second coupling line segment 12 is open. The two ends of the second transmission line segment 14 are respectively connected to the first end of the first coupling line segment 11 and the first end of the fifth transmission line segment 16, and the first end of the first coupling line segment 11 is also connected to port 1, and the second end of the first coupling line segment 11 is open. The two ends of the third transmission line segment 23 are respectively connected to the first end of the sixth coupling line segment 22 and the first end of the fifth transmission line segment 16, and the second end of the sixth coupling line segment 22 is open. The two ends of the fourth transmission line segment 24 are respectively connected to the first end of the fifth coupling line segment 21 and the first end of the sixth transmission line segment 26, and the first end of the fifth coupling line segment 21 is also connected to port 2, and the second end of the fifth coupling line segment 21 is open. Either port 1 or port 2 is used as an input port, and the other is used as an output port.

[0024] The first transmission line segment 13 and the fourth transmission line segment 24 are substantially on a straight line, referred to as the first straight line. The first straight line is substantially perpendicular to the first pair of parallel coupling segments. The first straight line is substantially perpendicular to the second pair of parallel coupling segments. The first straight line is substantially perpendicular to the third pair of parallel coupling segments. The first transmission line segment 13 and the fourth transmission line segment 24 are sandwiched between and jointly connected to the first end of the sixth transmission line segment 26. The second end of the sixth transmission line segment 26 is connected to the first end of the fourth coupling segment 25, and the second end of the fourth coupling segment 25 is open.

[0025] The second transmission line segment 14 and the third transmission line segment 23 are substantially on a straight line, referred to as the second straight line. The second straight line is substantially perpendicular to the first pair of parallel coupling segments. The second straight line is substantially perpendicular to the second pair of parallel coupling segments. The second straight line is substantially perpendicular to the third pair of parallel coupling segments. The second straight line is substantially parallel to the first straight line. The second transmission line segment 14 and the third transmission line segment 23 sandwich and connect to the first end of the fifth transmission line segment 16. The second end of the fifth transmission line segment 16 is connected to the first end of the third coupling segment 15, and the second end of the third coupling segment 15 is open.

[0026] Figure 2 The circuit structure of the multi-stub resonator microstrip dual-passband filter shown can be simplified as follows: Figure 3 The diagram shows a pair of essentially parallel transmission lines. The electrical length of these two transmission lines is θ, and the even-mode impedance based on odd-even mode analysis is Z. 0e The odd-mode impedance value based on even-mode analysis is Z. 0o . Figure 3 In the middle, the transmission line located above corresponds, for example, to Figure 2 The sum of the first coupling section 11, port 1, second transmission section 14, fifth transmission section 16, third coupling section 15, third transmission section 23, and sixth coupling section 22 provides input current I1 and input voltage V1 through input port 1. Figure 3 In the middle, the transmission line two located below corresponds to, for example, to Figure 2 The sum of the second coupling section 12, the first transmission section 13, the sixth transmission section 26, the fourth coupling section 25, the fourth transmission section 24, port 2, and the fifth coupling section 21 in the output port 2 is used to obtain the output current I2 and the output voltage V2.

[0027] Formula 1

[0028] The coupling matrix A is calculated using Formula 1, where j represents the imaginary unit and cot represents the cotangent function. It can be observed that the coupling matrix A is a two-row, two-column matrix containing four matrix elements.

[0029] Formula 2 is

[0030] In Formula 2, A 12 This represents the matrix element in the first row and second column of the coupling matrix A. 22 This represents the element in the second row and second column of coupling matrix A. Formula 2 calculates the single-ended input impedance Z of the input port based on coupling matrix A. in .

[0031] Figure 2 In the multi-stub resonator microstrip dual-passband filter shown, the first pair of parallel coupled lines 11 and 12, the first transmission line 13, the second pair of parallel coupled lines 15 and 25, and the second transmission line 14 constitute the loop resonance of the first U-shaped architecture. The second pair of parallel coupled lines 15 and 25, the third transmission line 23, the third pair of parallel coupled lines 21 and 22, and the fourth transmission line 24 constitute the loop resonance of the second U-shaped architecture. The loop resonances of these two U-shaped architectures are basically axially symmetric about the second pair of parallel coupled lines 15 and 25. The first pair of parallel coupled lines, the second pair of parallel coupled lines, and the third pair of parallel coupled lines constitute dual microstrip line stubs. The first pair of parallel coupled lines 11 and 12 and the third pair of parallel coupled lines 21 and 22 are also basically axially symmetric about the second pair of parallel coupled lines 15 and 25. Dual-passband filters require two resonant points to achieve two passbands, necessitating numerous microstrip stubs for resonance, resulting in a complex and large circuit structure. This invention innovatively employs two U-shaped loop resonators and dual microstrip stubs to generate two resonant points, forming two passbands. The first pair of parallel coupled segments 11 and 12, and the third pair of parallel coupled segments 21 and 22 resonate at the first frequency f1, while the second pair of parallel coupled segments 15 and 25 resonates at the second frequency f2. Based on the required first frequency f1 and second frequency f2, the input impedance of the input port and the input impedance of the output port can be calculated, and then adjusted accordingly. Figure 2 The length and width of each part can be adjusted to control the two resonant frequencies and the impedance of the entire filter, thus completing the design of a dual-passband filter. The circuit architecture of this invention is simple, small in size, and has superior performance.

[0032] Please see Figure 4 This is a schematic diagram of the scattering parameters (S-parameters) of the multi-stub resonator microstrip dual-passband filter based on a glass substrate according to the present invention. The present invention relates to a dual-passband filter, and the S-parameters are used to measure the effectiveness of the dual-passband design. Figure 4 In the diagram, S11, shown by the solid line, represents the reflection coefficient, and S21, shown by the dashed line, represents the forward transmission coefficient. Generally, within the passband, S11 should be less than -10dB, and S21 should be as close to zero as possible; outside the passband, S11 should be as close to zero as possible, and S21 should be less than -10dB. Figure 3The example illustrates two passbands of 4 GHz and 4.75 GHz. Furthermore, this invention can achieve S11 less than -25 dB and S21 between -1 dB and 0 within the passband; and S11 between -2 dB and 0 and S21 less than -17 dB outside the passband. This fully demonstrates that the dual-passband filter implemented by this invention has excellent dual-passband performance. Figure 2 The different values ​​of the shape and size of each part in the circuit structure shown will result in changes in the center frequencies of the two passbands.

[0033] Compared to CN115425377A and CN115425376A, this invention employs a simpler circuit architecture to realize a multi-stub resonator microstrip dual-passband filter. Furthermore, this invention uses a glass substrate, eliminating the need for metal vias in the glass layer, thus simplifying manufacturing.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microstrip dual-passband filter based on a glass substrate with a multi-stub resonator, characterized in that... Two U-shaped loop resonances are formed in the metal on only one side of the glass substrate; the first pair of parallel coupling lines, the first transmission line (13), the second pair of parallel coupling lines, and the second transmission line (14) constitute the first U-shaped loop resonance; the second pair of parallel coupling lines, the third transmission line (23), the third pair of parallel coupling lines, and the fourth transmission line (24) constitute the second U-shaped loop resonance; the loop resonances of the two U-shaped structures are axially symmetrical about the second pair of parallel coupling lines; Among them, the first parallel coupling line segment (11) and the second parallel coupling line segment (12) constitute the first pair of parallel coupling line segments; the third parallel coupling line segment (15) and the fourth parallel coupling line segment (25) constitute the second pair of parallel coupling line segments; the fifth parallel coupling line segment (21) and the sixth parallel coupling line segment (22) constitute the third pair of parallel coupling line segments; the first pair of parallel coupling line segments, the second pair of parallel coupling line segments, and the third pair of parallel coupling line segments are parallel to each other; The two ends of the first transmission line segment (13) are respectively connected to the first end of the second coupling line segment (12) and the first end of the sixth transmission line segment (26), and the second end of the second coupling line segment (12) is open. The two ends of the second transmission line section (14) are respectively connected to the first end of the first coupling line section (11) and the first end of the fifth transmission line section (16). The first end of the first coupling line section (11) is also connected to port one (1). The second end of the first coupling line section (11) is open. The two ends of the third transmission line section (23) are respectively connected to the first end of the sixth coupling line section (22) and the first end of the fifth transmission line section (16), and the second end of the sixth coupling line section (22) is open. The two ends of the fourth transmission line section (24) are respectively connected to the first end of the fifth coupling line section (21) and the first end of the sixth transmission line section (26). The first end of the fifth coupling line section (21) is also connected to port two (2), and the second end of the fifth coupling line section (21) is open. The first transmission line segment (13) and the fourth transmission line segment (24) are on a straight line, which is called the first straight line; the first straight line is perpendicular to the first pair of parallel coupling segments; the first transmission line segment (13) and the fourth transmission line segment (24) are sandwiched between and connected to the first end of the sixth transmission line segment (26), the second end of the sixth transmission line segment (26) is connected to the first end of the fourth coupling segment (25), and the second end of the fourth coupling segment (25) is open. The second transmission line segment (14) and the third transmission line segment (23) are on a straight line, which is called the second straight line; the second straight line is perpendicular to the first pair of parallel coupling segments; the second transmission line segment (14) and the third transmission line segment (23) are sandwiched between and jointly connected to the first end of the fifth transmission line segment (16), the second end of the fifth transmission line segment (16) is connected to the first end of the third coupling segment (15), and the second end of the third coupling segment (15) is open; The first pair of parallel coupled line segments, the second pair of parallel coupled line segments, and the third pair of parallel coupled line segments constitute a dual microstrip line stub; The first pair of parallel coupled nodes and the third pair of parallel coupled nodes resonate at the first frequency, and the second pair of parallel coupled nodes resonates at the second frequency; the loop resonance of the two U-shaped structures and the dual microstrip line stubs together generate two resonant points, forming two passbands; the metal on the other side of the glass substrate serves as a reference ground.

2. The microstrip dual-passband filter based on a glass substrate multi-stub resonator according to claim 1, characterized in that, Either port 1 (1) or port 2 (2) can be used as an input port, and the other can be used as an output port.

3. The microstrip dual-passband filter based on a glass substrate multi-stub resonator according to claim 1, characterized in that, The first pair of parallel coupling segments and the third pair of parallel coupling segments are axially symmetrical about the second pair of parallel coupling segments.

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