Surface acoustic wave filter with built-in inductor

Abstract

The utility model discloses a surface acoustic wave filter with a built-in inductor, which belongs to the technical field of surface acoustic wave filters, comprises a piezoelectric substrate, and is characterized in that one end of a coupling resonant filter is connected with a signal input terminal, and the other end of the coupling resonant filter is connected with one end of a third surface acoustic wave resonator; the other end of the third surface acoustic wave resonator is connected with the signal output terminal, the first surface acoustic wave resonator and the first inductor are connected between the signal input terminal and the coupling resonant filter in parallel, one end of the first surface acoustic wave resonator is connected with the signal input terminal, and the other end of the first surface acoustic wave resonator is connected with the ground potential. One end of the first inductor is connected with the signal input terminal, and the other end is connected with a ground potential. Compared with the prior art, the bandwidth of the surface acoustic wave filter is expanded.

Description

Technical Field

[0001] The utility model relates to the technical field of surface acoustic wave filters, in particular to an internal inductor surface acoustic wave filter. Background Art

[0002] Surface acoustic wave filters, with their excellent frequency selectivity and low-loss characteristics, have become key components for signal filtering. However, the two key performance indicators of relative bandwidth and rectangularity are inevitably restricted by the physical properties of the materials used and the complexity of the design structure.

[0003] To solve this technical problem, the existing method is to use an external matching circuit to expand the bandwidth of the surface acoustic wave filter. Specifically, the external matching circuit can adjust the input and output impedances of the filter to better match other parts of the system, reduce signal reflection and loss during transmission, and thereby improve the signal transmission efficiency and the overall performance of the filter. At the same time, through reasonable circuit design, the frequency response characteristics of the filter can also be improved to a certain extent, making it closer to the ideal state and meeting a wider range of application requirements.

[0004] However, this solution is not perfect, and it exposes a series of defects in practical applications:

[0005] ① Components and connecting wires in the external circuit will introduce additional losses, resulting in an increase in the insertion loss of the filter, which will affect the signal transmission efficiency and reduce the overall performance of the system.

[0006] ② During the process of expanding the bandwidth, the group delay characteristic of the filter may change, resulting in signal distortion in the frequency domain. This distortion may affect the waveform and phase characteristics of the signal, and thus affect the signal transmission quality.

[0007] ③ Components in the external circuit may be affected by temperature changes, resulting in changes in the performance of the filter, which will affect the stability and reliability of the filter, especially more significantly in high-temperature or low-temperature environments. Summary of the Invention

[0008] The purpose of the utility model is to provide an internal inductor surface acoustic wave filter to achieve the purpose of expanding the bandwidth of the surface acoustic wave filter in view of the above deficiencies of the prior art.

[0009] An internally inductive surface acoustic wave filter provided by the present utility model comprises a piezoelectric substrate; characterized in that: a first surface acoustic wave resonator, a second surface acoustic wave resonator, a third surface acoustic wave resonator, a coupled resonator filter, a first inductor and a second inductor are provided on the piezoelectric substrate; one end of the coupled resonator filter is connected to a signal input terminal, the other end is connected to one end of the third surface acoustic wave resonator, the other end of the third surface acoustic wave resonator is connected to a signal output terminal, the first surface acoustic wave resonator and the first inductor are respectively connected in parallel between the signal input terminal and the coupled resonator filter, one end of the first surface acoustic wave resonator is connected to the signal input terminal, the other end is connected to a ground potential, one end of the first inductor is connected to the signal input terminal, the other end is connected to a ground potential, the second surface acoustic wave resonator is connected in parallel between the coupled resonator filter and the third surface acoustic wave resonator, one end of the second surface acoustic wave resonator is connected to a connection point between the coupled resonator filter and the third surface acoustic wave resonator, the other end of the third surface acoustic wave resonator is connected to a ground potential; the second inductor is connected in parallel between the third surface acoustic wave resonator and the signal output terminal, one end of the second inductor is connected to the signal output terminal, the other end is connected to a ground potential.

[0010] Further, the coupled resonator filter comprises three groups of interdigital transducers and two groups of reflection gratings, the three groups of interdigital transducers are placed collinearly, and one reflection grating is placed at each of its two ends.

[0011] Further, the signal input terminal is respectively connected to a comb-shaped electrode at one end of the first surface acoustic wave resonator, a comb-shaped electrode at one end of the interdigital transducer at the middle position of the coupled resonator filter and an input end of the first inductor through a bus bar, the comb-shaped electrode at the other end of the first surface acoustic wave resonator is connected to a ground potential through a bus bar, the comb-shaped electrode at the other end of the interdigital transducer at the middle position of the coupled resonator filter is connected to a ground potential through a bus bar, the output end of the first inductor is connected to a ground potential; the comb-shaped electrodes at one end of the interdigital transducers on both sides of the coupled resonator filter are respectively connected to a ground potential through a bus bar, the comb-shaped electrodes at the other end of the interdigital transducers on both sides of the coupled resonator filter are respectively connected to the comb-shaped electrodes at one end of the second surface acoustic wave resonator and the third surface acoustic wave resonator through a bus bar, the comb-shaped electrode at the other end of the second surface acoustic wave resonator is connected to a ground potential through a bus bar, the comb-shaped electrodes at the other end of the third surface acoustic wave resonator are respectively connected to an input end of the second inductor and a signal output terminal through a bus bar, and the output end of the second inductor is connected to a ground potential.

[0012] Further, the first inductor and the second inductor are annular vortex-shaped linear structure inductors, quadrilateral vortex-shaped linear structure inductors or hexagonal vortex-shaped linear structure inductors.

[0013] Compared with the prior art, the utility model has the following prominent beneficial effects:

[0014] In the utility model, a built-in inductor, namely a first inductor and a second inductor, is respectively connected in parallel at the positions of a signal input terminal and a signal output terminal, and the relative bandwidth of the surface acoustic wave filter is further broadened through the combination of sound and electricity. Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of the utility model;

[0016] Figure 2 is a schematic structural diagram of a coupled resonator filter part of the utility model;

[0017] Figure 3 is a circuit diagram of the utility model;

[0018] Wherein, 1. piezoelectric substrate, 2. first surface acoustic wave resonator, 3. coupled resonator filter, 4. first inductor, 5. third surface acoustic wave resonator, 6. second surface acoustic wave resonator, 7. ground potential, 8. signal input terminal, 9. signal output terminal, 10. second inductor. Detailed Embodiments

[0019] The utility model will be further described below in conjunction with the drawings in the specification and the detailed embodiments.

[0020] As Figures 1 to 3 shown, the utility model includes a piezoelectric substrate 1, a first surface acoustic wave resonator 2, a second surface acoustic wave resonator 6, a third surface acoustic wave resonator 5, a coupled resonator filter 3, a first inductor 4 and a second inductor 10.

[0021] The piezoelectric substrate 1 is provided with a first surface acoustic wave resonator 2, a second surface acoustic wave resonator 6, a third surface acoustic wave resonator 5, a coupled resonator filter 3, a first inductor 4 and a second inductor 10.

[0022] The material of the piezoelectric substrate 1 is lithium niobate, lithium tantalate, quartz or a pyroelectricity-free lithium niobate or lithium tantalate wafer.

[0023] One end of the coupled resonator filter 3 is connected to the signal input terminal 8, the other end is connected to one end of the third surface acoustic wave resonator 5, and the other end of the third surface acoustic wave resonator 5 is connected to the signal output terminal 9.

[0024] Between the signal input terminal 8 and the coupled resonator filter 3, the first surface acoustic wave resonator 2 and the first inductor 4 are respectively connected in parallel. One end of the first surface acoustic wave resonator 2 is connected to the signal input terminal 8, and the other end is connected to the ground potential 7. One end of the first inductor 4 is connected to the signal input terminal 8, and the other end is connected to the ground potential 7.

[0025] The described coupled resonator filter 3 is in parallel with the third surface acoustic wave resonator 5 and the second surface acoustic wave resonator 6. One end of the second surface acoustic wave resonator 6 is connected to the connection point between the coupled resonator filter 3 and the third surface acoustic wave resonator 5, and the other end of the third surface acoustic wave resonator 5 is connected to the ground potential 7.

[0026] The described third surface acoustic wave resonator 5 is in parallel with the second inductor 10 between it and the signal output terminal 9. One end of the second inductor 10 is connected to the signal output terminal 9, and the other end is connected to the ground potential 7.

[0027] In this embodiment, the described coupled resonator filter 3 includes three groups of interdigital transducers and two groups of reflection gratings. The three groups of interdigital transducers are placed collinearly, and a reflection grating is placed at each end.

[0028] The described signal input terminal 8 is connected to the comb-shaped electrode at one end of the first surface acoustic wave resonator 2, the comb-shaped electrode at one end of the interdigital transducer at the middle position of the coupled resonator filter 3, and the input end of the first inductor 4 through a bus bar. The comb-shaped electrode at the other end of the first surface acoustic wave resonator 2 is connected to the ground potential 7 through a bus bar. The comb-shaped electrode at the other end of the interdigital transducer at the middle position of the coupled resonator filter 3 is connected to the ground potential 7 through a bus bar. The output end of the first inductor 4 is connected to the ground potential 7.

[0029] The comb-shaped electrodes at one end of the interdigital transducers on both sides of the described coupled resonator filter 3 are respectively connected to the ground potential 7 through a bus bar. The comb-shaped electrodes at the other end of the interdigital transducers on both sides of the coupled resonator filter 3 are respectively connected to the comb-shaped electrodes at one end of the second surface acoustic wave resonator 6 and the third surface acoustic wave resonator 5 through a bus bar. The comb-shaped electrode at the other end of the second surface acoustic wave resonator 6 is connected to the ground potential 7 through a bus bar. The comb-shaped electrode at the other end of the third surface acoustic wave resonator 5 is respectively connected to the input end of the second inductor 10 and the signal output terminal 9 through a bus bar, and the output end of the second inductor 10 is connected to the ground potential 7.

[0030] The described first inductor 4 and second inductor 10 are toroidal spiral-shaped inductors, and the calculation formula for their inductance is:

[0031]

[0032] Where

[0033]

[0034]

[0035]

[0036] n is the number of turns of the annular vortex line;

[0037] The first inductor 4 and the second inductor 10 described above can also be inductors with a quadrilateral or hexagonal vortex line structure, and the calculation formula for their inductance is:

[0038]

[0039] Wherein,

[0040]

[0041]

[0042]

[0043] It should be noted that the specific embodiments of the present invention have been described in detail. For those skilled in the art, various obvious changes made to it without departing from the spirit and scope of the present invention are within the protection scope of the present invention.

Claims

1. An internally inductive surface acoustic wave filter, comprising a piezoelectric substrate (1); characterized in that: A first surface acoustic wave resonator (2), a second surface acoustic wave resonator (6), a third surface acoustic wave resonator (5), a coupled resonator filter (3), a first inductor (4), and a second inductor (10) are provided on the piezoelectric substrate (1); one end of the coupled resonator filter (3) is connected to a signal input terminal (8), the other end is connected to one end of the third surface acoustic wave resonator (5), the other end of the third surface acoustic wave resonator (5) is connected to a signal output terminal (9), the first surface acoustic wave resonator (2) and the first inductor (4) are respectively connected in parallel between the signal input terminal (8) and the coupled resonator filter (3), one end of the first surface acoustic wave resonator (2) is connected to the signal input terminal (8), the other end is connected to a ground potential (7), one end of the first inductor (4) is connected to the signal input terminal (8), the other end is connected to the ground potential (7), the second surface acoustic wave resonator (6) is connected in parallel between the coupled resonator filter (3) and the third surface acoustic wave resonator (5), one end of the second surface acoustic wave resonator (6) is connected to a connection point between the coupled resonator filter (3) and the third surface acoustic wave resonator (5), the other end of the third surface acoustic wave resonator (5) is connected to the ground potential (7); the second inductor (10) is connected in parallel between the third surface acoustic wave resonator (5) and the signal output terminal (9), one end of the second inductor (10) is connected to the signal output terminal (9), the other end is connected to the ground potential (7).

2. The surface acoustic wave filter with an internal inductor according to claim 1, wherein: The coupled resonator filter (3) includes three groups of interdigital transducers and two groups of reflection gratings. The three groups of interdigital transducers are placed collinearly, and a reflection grating is placed at each of its two ends.

3. The surface acoustic wave filter with built-in inductor according to claim 1, characterized in that: The signal input terminal (8) is respectively connected to the comb-shaped electrode at one end of the first surface acoustic wave resonator (2), the comb-shaped electrode at one end of the interdigital transducer at the middle position of the coupled resonator filter (3), and the input end of the first inductor (4) through a bus bar. The comb-shaped electrode at the other end of the first surface acoustic wave resonator (2) is connected to the ground potential (7) through a bus bar. The comb-shaped electrode at the other end of the interdigital transducer at the middle position of the coupled resonator filter (3) is connected to the ground potential (7) through a bus bar. The output end of the first inductor (4) is connected to the ground potential (7); the comb-shaped electrodes at one end of the interdigital transducers on both sides of the coupled resonator filter (3) are respectively connected to the ground potential (7) through a bus bar. The comb-shaped electrodes at the other end of the interdigital transducers on both sides of the coupled resonator filter (3) are respectively connected to the comb-shaped electrodes at one end of the second surface acoustic wave resonator (6) and the third surface acoustic wave resonator (5) through a bus bar. The comb-shaped electrode at the other end of the second surface acoustic wave resonator (6) is connected to the ground potential (7) through a bus bar. The comb-shaped electrode at the other end of the third surface acoustic wave resonator (5) is respectively connected to the input end of the second inductor (10) and the signal output terminal (9) through a bus bar. The output end of the second inductor (10) is connected to the ground potential (7).

4. An internal inductance surface acoustic wave filter according to claim 1, characterized in that: The first inductor (4) and the second inductor (10) are toroidal vortex linear structure inductors, quadrilateral vortex linear structure inductors, or hexagonal vortex linear structure inductors.

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