Filter circuit, dielectric filter and duplexer

Abstract

The utility model relates to a filter circuit, a dielectric filter and a duplexer, and the filter circuit comprises a signal input end which is used for inputting a signal; the signal output end is used for outputting a signal; the resonance unit comprises a plurality of resonance circuits which are sequentially arranged between the signal input end and the signal output end in parallel; the coupling inductor unit is arranged between the signal input end and the grounding end and between the signal output end and the grounding end, and the coupling capacitor unit is arranged between the signal input end and the first resonance circuit and between the signal output end and the last resonance circuit. According to the utility model, the problem of large return loss in an ultra-wide passband can be solved, standing waves are effectively improved, the working efficiency of the filter is improved, and the communication effect is improved. The dielectric filter is connected with the grounding silver layer on the outer surface of the ceramic substrate through leading out a first connecting line and a second connecting line from the input port and the output port respectively, and plays a role of equivalent inductance.

Description

Technical Field

[0001] This utility model relates to the field of communication equipment technology, and in particular to a filter circuit, a dielectric filter, and a duplexer. Background Technology

[0002] During filter operation, when a signal passes through the filter, the reflected wave due to impedance mismatch or filter characteristics superimposed on the incident wave will form a standing wave phenomenon (also known as return loss). Standing waves affect system performance and signal transmission quality, leading to signal energy loss, reduced system efficiency, signal distortion, and impaired communication. Excessively high standing wave ratios can cause equipment overheating and even damage. Therefore, controlling standing waves is particularly important in radio frequency and microwave systems. Specifically, monitoring the amount of signal reflected back when passing through the filter indicates low return loss and minimal signal attenuation or distortion; conversely, high return loss indicates high return loss. Different filters have different passband width requirements, allowing different signal frequencies to pass. A wider passband allows for a wider range of signal frequencies. For example, in 5G systems, the Ministry of Industry and Information Technology (MIIT) has allocated the 3400MHz~3600MHz frequency band to China Mobile and China Unicom. The connection between the input and output ports and the filter circuit is called input coupling and output coupling (or input-output matching). The suitability of this coupling or matching directly determines the quality of the filter's passband return loss. Generally speaking, the wider the passband, the larger the required input and output coupling capacitors.

[0003] In actual production, silver layers are printed on the surface of the ceramic body to form coupling between different silver layers. However, due to the limited area and volume, the input and output coupling capacitance cannot be increased indefinitely. Therefore, when designing and manufacturing dielectric filters, there is a problem of excessively wide passband, which leads to severe return loss. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a filter circuit, dielectric filter and duplexer that can solve the problem of large return loss in ultra-wide passband, effectively reduce return loss, improve standing wave ratio, improve filter efficiency and enhance communication performance.

[0005] To solve the above-mentioned technical problems, this utility model provides a filter circuit, including,

[0006] The signal input terminal is used to input signals.

[0007] The signal output terminal is used to output signals.

[0008] A coupling inductor unit is disposed between the signal input terminal and the ground terminal, and between the signal output terminal and the ground terminal;

[0009] A coupling capacitor unit is disposed between the signal input terminal and the first resonant circuit, and between the signal output terminal and the last resonant circuit;

[0010] During operation, the electrical signal is input from the signal input terminal, passes through multiple resonant circuits, and is output from the signal output terminal.

[0011] In one embodiment of this utility model, the coupling inductor unit includes a first coupling inductor and a second coupling inductor, the first coupling inductor being disposed between the signal input terminal and the ground terminal, and the second coupling inductor being disposed between the signal output terminal and the ground terminal.

[0012] In one embodiment of this utility model, the coupling capacitor unit includes a first coupling capacitor and a second coupling capacitor. The first coupling capacitor is disposed between the signal input terminal and the resonant unit, and the second coupling capacitor is disposed between the signal output terminal and the resonant unit.

[0013] This utility model also provides a dielectric filter, comprising,

[0014] Matrix;

[0015] An electrode surface is disposed on the substrate and is used to connect a circuit board. The electrode surface includes an input port and an output port.

[0016] A circuit printing surface is disposed on the substrate, and the circuit printing surface is provided with a plurality of silver blocks; the signal input terminal of the filter circuit is connected to the input port, and the signal output terminal of the filter circuit is connected to the output port;

[0017] A ground plane is disposed on the substrate, and the input port is electrically connected to the ground plane via a first connecting line; the output port is electrically connected to the ground plane via a second connecting line.

[0018] The electrode surface, the circuit printing surface, and the ground plane can support a filter circuit as described above.

[0019] In one embodiment of this utility model, a first silver block, a second silver block, a third silver block, and a fourth silver block are sequentially arranged on the circuit printing surface, the input port is connected to the first silver block, and the output port is connected to the fourth silver block.

[0020] In one embodiment of this utility model, the substrate is provided with a first through hole, a second through hole, a third through hole and a fourth through hole at intervals, wherein the first through hole corresponds to the first silver block, the second through hole corresponds to the second silver block, the third through hole corresponds to the third silver block and the fourth through hole corresponds to the fourth silver block.

[0021] In one embodiment of this utility model, both the first connecting line and the second connecting line are silver wires.

[0022] In one embodiment of this utility model, the substrate is a ceramic body with a dielectric constant of 90.

[0023] In one embodiment of this utility model, the electrode surface and the ground surface are disposed opposite to each other along the thickness direction of the substrate, and the circuit printing surface is disposed on the side of the substrate.

[0024] This invention also provides a duplexer, comprising at least one dielectric filter as described above.

[0025] The above-mentioned technical solution of this utility model has the following advantages compared with the prior art:

[0026] The filter circuit described in this utility model includes a signal input terminal, a signal output terminal, a resonant unit, and a coupling inductor unit. The resonant unit includes multiple resonant circuits arranged in parallel between the signal input terminal and the signal output terminal. The coupling inductor unit is arranged between the signal input terminal and the first resonant circuit, and between the signal output terminal and the last resonant circuit. This forms an L-shaped matching network between the signal input terminal and the ground terminal of the filter circuit, and also between the signal output terminal and the ground terminal. This solves the problem of high return loss in an ultra-wide passband, effectively reduces return loss, improves standing wave ratio, and thus improves the working efficiency of the filter and enhances communication performance. Attached Figure Description

[0027] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0028] Figure 1 This is a schematic diagram of the filter circuit structure of a preferred embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of a dielectric filter according to a preferred embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the circuit structure of a filter that supports 512MHz-582MHz with an output coupling capacitor of 16.6pF.

[0031] Figure 4 yes Figure 3 A schematic diagram of a standing wave test.

[0032] Figure 5 yes Figure 3 Based on the circuit, with the input and output capacitance still at 16.6pF, the schematic diagram of the standing wave test when the filter passband is 462MHz~582MHz is shown.

[0033] Figure 6 exist Figure 5 Based on this, a schematic diagram of the standing wave test after adopting the filtering circuit of this utility model is provided.

[0034] Explanation of reference numerals in the accompanying drawings: P1, signal input terminal; P2, signal output terminal; L1, first coupling inductor; L2, second coupling inductor; C1, first coupling capacitor; C2, second coupling capacitor; LC1, first resonant circuit; LC2, second resonant circuit; LC3, third resonant circuit; LC4, fourth resonant circuit; 1, substrate; 10, electrode surface; 101, input port; 102, output port; 20, circuit printing surface; 201, first silver block; 202, second silver block; 203, third silver block; 204, fourth silver block; 30, ground plane; 41, first connecting line; 42, second connecting line. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. Example 1

[0036] Reference Figure 1 As shown, this utility model discloses a filter circuit, including a signal input terminal P1, which is used to input signals;

[0037] The filter circuit also includes a signal output terminal P2, which is used to output a signal.

[0038] The filter circuit further includes a resonant unit, which includes multiple resonant circuits arranged in parallel between the signal input terminal P1 and the signal output terminal P2. Specifically, the resonant circuit is a capacitor-inductor resonant circuit. During operation, the electrical signal is input from the signal input terminal, passes through the multiple resonant circuits, and is output from the signal output terminal.

[0039] The filter circuit also includes a coupling inductor unit, which is disposed between the signal input terminal P1 and the first resonant circuit, and between the signal output terminal P2 and the last resonant circuit; in detail, one end of the coupling inductor unit is grounded, and the other end is connected to the filter circuit.

[0040] The filter circuit also includes a coupling capacitor unit, which is disposed between the signal input terminal P1 and the first resonant circuit, and between the signal output terminal P2 and the last resonant circuit.

[0041] In this way, an L-shaped matching network can be formed between the signal input terminal P1 and the ground terminal of the filter circuit, and an L-shaped matching network can be formed between the signal output terminal P2 and the ground terminal to continuously achieve wide-band return loss coupling.

[0042] Therefore, it can be seen that the filter circuit protected by this utility model has a signal input terminal, a signal output terminal, a resonant unit, and a coupling inductor unit. The resonant unit includes multiple resonant circuits arranged in parallel between the signal input terminal and the signal output terminal. The coupling inductor unit is arranged between the signal input terminal and the first resonant circuit, and between the signal output terminal and the last resonant circuit. This forms an L-shaped matching network between the signal input terminal and the ground terminal of the filter circuit, and between the signal output terminal and the ground terminal. This solves the problem of large return loss in the ultra-wide passband, effectively reduces return loss, improves standing wave ratio, and thus improves the working efficiency of the filter and enhances the communication effect.

[0043] In a preferred embodiment, the coupling inductor unit includes a first coupling inductor L1 and a second coupling inductor L2. The first coupling inductor L1 is disposed between the signal input terminal P1 and the ground terminal, and the second coupling inductor L2 is disposed between the signal output terminal P2 and the ground terminal.

[0044] In this embodiment, the resonant unit includes a first resonant circuit LC1, a second resonant circuit LC2, a third resonant circuit LC3, and a fourth resonant circuit LC4 arranged sequentially along the signal input terminal P1 to the signal output terminal P2.

[0045] Of course, in some other implementations, the number of resonant circuits may vary depending on the characteristics of the filter, and may be two, three or more.

[0046] In detail, the filter circuit also includes a first coupling capacitor C1 and a second coupling capacitor C2. The first coupling capacitor C1 is disposed between the signal input terminal P1 and the resonant unit, and the second coupling capacitor C2 is disposed between the signal output terminal P2 and the resonant unit. Thus, the first coupling capacitor C1 and the first coupling inductor L1 cooperate to form a first L-shaped matching network, and the second coupling capacitor C2 and the second coupling inductor L2 cooperate to form a second L-shaped matching network.

[0047] The present invention will be described below with reference to specific embodiments:

[0048] For example Figure 3 The filter circuit shown, with an input-output coupling capacitor of 16.6pF, supports a return loss of less than -20dB for frequencies ranging from 512MHz to 582MHz. Figure 4 As shown.

[0049] In practical applications, when the filter passband is 462MHz~582MHz, the input and output capacitances remain unchanged at 16.6pF. Figure 5 As shown in the figure, the S11 line (i.e., the return loss line) reaches -10dB, which is much worse than the previous scheme. Moreover, due to the poor return loss, obvious ripples also appear in the passband.

[0050] When the filter circuit scheme of this utility model is adopted, such as Figure 1 As shown, the filter passband remains 462MHz~582MHz. At this point, combined with... Figure 5 As shown, the return loss in the passband is less than -20dB, indicating that the solution can indeed solve the problem of poor return loss in the passband within the ultra-wide passband. Example 2

[0051] refer to Figure 2 As shown, this utility model also discloses a dielectric filter, including a substrate 1;

[0052] The dielectric filter further includes an electrode surface 10, which is disposed on the substrate 1 and is used to connect to a circuit board. The electrode surface 10 includes an input port 101 and an output port 102.

[0053] The dielectric filter further includes a circuit printing surface 20, which is disposed on the substrate 1, and a plurality of silver blocks are printed on the circuit printing surface 20.

[0054] The signal input terminal P1 of the filter circuit is connected to the input port 101, and the signal output terminal P2 of the filter circuit is connected to the output port 102.

[0055] The dielectric filter further includes a ground plane 30, which is disposed on the substrate 1. The input port 101 is electrically connected to the ground plane 30 via a first connecting line 41; the output port 102 is electrically connected to the ground plane 30 via a second connecting line 42. It should be noted that, in radio frequency characteristics, the first connecting line 41 and the second connecting line 42 can be equivalent to inductors with a certain inductance value. Therefore, the first connecting line 41 can be equivalent to the first coupling inductor L1 in Embodiment 1, and the second connecting line 42 can be equivalent to the second coupling inductor L2 in Embodiment 1.

[0056] The electrode surface 10, the circuit printing surface 20, and the ground surface 30, as described above, cooperate with each other to support the filter circuit as described in Embodiment 1.

[0057] Therefore, it can be understood that the dielectric filter to be protected by this utility model is connected to the grounding silver layer on the outer surface of the ceramic substrate by leading out the first connecting line and the second connecting line from the input port and the output port respectively. Since the grounding wire can be equivalent to an inductor with a certain inductance value in the radio frequency characteristics, the first connecting line and the second connecting line play the role of equivalent inductor, and together with the resonant unit, a filter circuit as described in Embodiment 1 is formed on the substrate.

[0058] In a preferred embodiment, a first silver block 201, a second silver block 202, a third silver block 203, and a fourth silver block 204 are sequentially and alternately printed on the circuit printing surface 20. A first resonant circuit LC1 is formed on the first silver block 201, a second resonant circuit LC2 is formed on the second silver block 202, a third resonant circuit LC3 is formed on the third silver block 203, and a fourth resonant circuit LC4 is formed on the fourth silver block 204. Adjacent silver blocks are coupled together.

[0059] The input port 101 is connected to the first silver block 201, and the output port 102 is connected to the fourth silver block 204.

[0060] Furthermore, the substrate 1 is provided with a first through hole, a second through hole, a third through hole, and a fourth through hole at intervals, corresponding to form four resonators. Among them, the first through hole corresponds to the first silver block 201, the second through hole corresponds to the second silver block 202, the third through hole corresponds to the third silver block 203, and the fourth through hole corresponds to the fourth silver block 204.

[0061] Combination Figure 1 and Figure 2 As shown, the working principle of the dielectric filter is as follows:

[0062] The signal enters the first silver block 201 through the input port 101, and the signal is split into two paths. One path is grounded through the first through hole connected to the first silver block 201, and the other path continues to be conducted to the second silver block 202, forming a first capacitor between the first silver block 201 and the second silver block 202. The capacitance value of the first capacitor is determined by the distance between the first silver block 201 and the second silver block 202.

[0063] The signal entering the second silver block 202 is divided into two paths. One path is grounded through the second through hole connected to the second silver block 202, and the other path continues to be conducted to the third silver block 203. A second capacitor is formed between the second silver block 202 and the third silver block 203. The capacitance value of the second capacitor is determined by the distance between the second silver block 202 and the third silver block 203.

[0064] Similarly, the signal is conducted from the third silver block 203 to the fourth silver block 204, the fourth silver block 204 is grounded through the fourth through hole, and the signal is conducted from the fourth silver block 204 to the output port 102 to realize the signal output; thus, a complete signal input and output process is formed.

[0065] In a preferred embodiment, both the first connecting line 41 and the second connecting line 42 are silver wires.

[0066] In detail, the substrate 1 is a ceramic body with a dielectric constant of 90.

[0067] In a specific implementation, for example, a silver layer with a width of 0.15 mm, a length of 6 mm, and a thickness of 10 μm is printed on a ceramic body with a dielectric constant of 90. Theoretically, its inductance value is approximately 12.6 NH. It should be noted that the inductance value can be achieved by adjusting the line width and length, thereby allowing for design adjustments according to different needs to achieve the optimal effect.

[0068] In a preferred embodiment, the electrode surface 10 and the ground surface 30 are disposed opposite each other along the thickness direction of the substrate, and the circuit printing surface 20 is disposed on the side of the substrate 1. Example 3

[0069] This utility model also discloses a duplexer, comprising two dielectric filters as described in Embodiment 2.

[0070] In the description of this utility model, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0071] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A filter circuit, characterized in that: include, The signal input terminal is used to input signals. The signal output terminal is used to output signals. A resonant unit, comprising a plurality of resonant circuits sequentially connected in parallel between the signal input terminal and the signal output terminal; A coupling inductor unit is disposed between the signal input terminal and the ground terminal, and between the signal output terminal and the ground terminal; A coupling capacitor unit is disposed between the signal input terminal and the first resonant circuit, and between the signal output terminal and the last resonant circuit; During operation, the electrical signal is input from the signal input terminal, passes through multiple resonant circuits, and is output from the signal output terminal.

2. The filter circuit according to claim 1, characterized in that: The coupling inductor unit includes a first coupling inductor and a second coupling inductor. The first coupling inductor is disposed between the signal input terminal and the ground terminal, and the second coupling inductor is disposed between the signal output terminal and the ground terminal.

3. A filter circuit according to claim 1, characterized in that: The coupling capacitor unit includes a first coupling capacitor and a second coupling capacitor. The first coupling capacitor is disposed between the signal input terminal and the resonant unit, and the second coupling capacitor is disposed between the signal output terminal and the resonant unit.

4. A dielectric filter, characterized in that: include, Matrix; An electrode surface is disposed on the substrate and is used to connect a circuit board. The electrode surface includes an input port and an output port. A circuit printing surface is disposed on the substrate, and the circuit printing surface is provided with a plurality of silver blocks; the signal input terminal of the filter circuit is connected to the input port, and the signal output terminal of the filter circuit is connected to the output port; A ground plane is disposed on the substrate, and the input port is electrically connected to the ground plane via a first connecting line; The output port is electrically connected to the ground plane via a second connecting line; The electrode surface, the circuit printing surface, and the ground plane are capable of supporting a filter circuit as described in any one of claims 1-3.

5. A dielectric filter according to claim 4, characterized in that: The circuit printing surface is provided with a first silver block, a second silver block, a third silver block and a fourth silver block in sequence. The input port is connected to the first silver block and the output port is connected to the fourth silver block.

6. A dielectric filter according to claim 5, characterized in that: The substrate is provided with a first through hole, a second through hole, a third through hole and a fourth through hole at intervals, wherein the first through hole corresponds to the first silver block, the second through hole corresponds to the second silver block, the third through hole corresponds to the third silver block and the fourth through hole corresponds to the fourth silver block.

7. A dielectric filter according to claim 4, characterized in that: Both the first connecting line and the second connecting line are silver wires.

8. A dielectric filter according to claim 4, characterized in that: The substrate is a ceramic body with a dielectric constant of 90.

9. A dielectric filter according to any one of claims 4-8, characterized in that: The electrode surface and the ground surface are arranged opposite each other along the thickness direction of the substrate, and the circuit printing surface is disposed on the side of the substrate.

10. A duplexer, characterized in that: It includes two dielectric filters as described in any one of claims 4-9.

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