Band-pass filter with stop-band structure

Abstract

The invention discloses a band-pass filter with a stop-band structure, which comprises the stop-band structure and a pass-band structure, the pass-band structure is connected with the stop-band structure, the stop-band structure is connected with an input end, and the stop-band structure is also connected with an output end. The stop band structure comprises a first series resonator, a sixth series resonator and a sixth parallel resonator, the first series resonator is used for adjusting the impedance of the filter, and the sixth series resonator and the sixth parallel resonator are used for forming stop bands at corresponding suppression positions; and the stop-band structure and the pass-band structure are arranged at an interval of a preset distance so as to realize far-end high suppression.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave filters, and in particular to a bandpass filter with a stopband structure. Background Art

[0002] A surface acoustic wave filter is a device that uses surface acoustic waves to propagate and filter in a crystal. It can filter high-frequency signals and is widely used in wireless communications, broadcasting and television, radar, navigation, etc. However, surface acoustic wave resonators mainly use the method of increasing the filter order to achieve remote suppression, which will increase the overall volume of the filter and worsen the loss. Summary of the invention

[0003] The purpose of the present invention is to design a bandpass filter with a stopband structure in order to solve the above problems.

[0004] The present invention achieves the above-mentioned purpose through the following technical solutions: Bandpass filter with stopband structure, including: A stopband structure and a passband structure, wherein the passband structure is connected to the stopband structure, the stopband structure is connected to the input end, and the stopband structure is also connected to the output end; The stopband structure and the passband structure are arranged at a preset distance.

[0005] The beneficial effects of the present invention are: The bandpass filter including the stopband structure includes a stopband structure and a passband structure. The passband structure is connected to the stopband structure. The stopband structure is connected to the input end. The stopband structure is also connected to the output end. The stopband structure includes a first series resonator, a sixth series resonator and a sixth parallel resonator. The first series resonator is used to adjust the filter impedance. The sixth series resonator and the sixth parallel resonator are used to form a stopband at a corresponding suppression point. The stopband structure and the passband structure are arranged at a preset distance to achieve high remote suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The overall structure diagram of the bandpass filter with a stopband structure of the present invention; Figure 2 A circuit diagram of a bandpass filter having a stopband structure according to the present invention; Figure 3 A resonator admittance diagram of a bandpass filter having a stopband structure according to the present invention; Figure 4 is an S parameter performance diagram of a bandpass filter with a stopband structure according to the present invention; Figure 5 The S parameter performance diagram of the bandpass filter with a stopband structure and the admittance diagram of the passband structure resonator of the present invention; Figure 6The S parameter performance diagram of the bandpass filter with a stopband structure and the admittance diagram of the stopband structure resonator of the present invention; In the figure: S1-first series resonator, S2-second series resonator, S3-third series resonator, S4-fourth series resonator, S5-fifth series resonator, S6-sixth series resonator, P1-first parallel resonator, P2-second parallel resonator, P3-third parallel resonator, P4-fourth parallel resonator, P5-fifth parallel resonator, P6-sixth parallel resonator, 1-input end, 2-output end, 3-ground end, 4-ground end, 5-ground end, 6-ground end. DETAILED DESCRIPTION

[0007] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0008] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0009] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0010] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0011] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0012] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0013] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0014] like Figure 1-6 As shown, the bandpass filter with stopband structure includes: A stopband structure and a passband structure, wherein the passband structure is connected to the stopband structure, the stopband structure is connected to an input terminal 1, and the stopband structure is also connected to an output terminal 2; The stopband structure and the passband structure are arranged at a preset distance.

[0015] In one embodiment, the stopband structure includes a first series resonator S1 , and one end of the first series resonator S1 is connected to the input end 1 .

[0016] In one embodiment, the stopband structure further includes a sixth series resonator S6 and a sixth parallel resonator P6 , and a common end of the sixth series resonator S6 and the sixth parallel resonator P6 is connected to the output end 2 .

[0017] In one embodiment, the passband structure includes a second parallel resonator P2, a third series resonator S3, a fourth series resonator S4, a fifth series resonator S5, a first parallel resonator P1, a second parallel resonator P2, a third parallel resonator P3, a fourth parallel resonator P4, and a fifth parallel resonator P5; the other end of the first series resonator S1 is connected to one end of the first parallel resonator P1 and a common end of the second series resonator S2, the other end of the first parallel resonator P1 is grounded, the other end of the second series resonator S2 and the common end of the second parallel resonator P2 are connected to the The third series resonator S3 is connected, the other end of the second parallel resonator P2 is grounded, the other end of the third series resonator S3 is respectively connected to the third parallel resonator P3 and the fourth series resonator S4, the other end of the third parallel resonator P3 is grounded, the other end of the fourth series resonator S4 is connected to one end of the fifth series resonator S5, the other end of the fourth parallel resonator P4 is grounded, the other end of the fifth series resonator S5 is respectively connected to the fifth parallel resonator P5 and the sixth series resonator S6, and the other end of the fifth parallel resonator P5 is grounded.

[0018] The first parallel resonator P1 and the second parallel resonator P2 are connected to a common ground, the third parallel resonator P3 and the fourth parallel resonator P4 are connected to a common ground, and the fifth parallel resonator P5 and the sixth parallel resonator P6 are connected to a common ground.

[0019] In this embodiment, the resonant frequency of the resonator is fa, the anti-resonant frequency is fr, and fa > fr. When f = fr, the admittance |Y|=∞; when f = fa, the admittance |Y|=0. Figure 3 It is the admittance curve of the second series resonator S2, the horizontal axis is frequency, the vertical axis is admittance value, the resonant frequency fa is 1.736 GHz, the anti-resonant frequency f is 1.806 GHz, the resonant frequency works within the passband range of the filter, and the anti-resonant frequency is outside the passband of the filter.

[0020] In this embodiment, the first series resonator S1, the sixth series resonator S6 and the sixth parallel resonator P6 form a stopband structure; wherein the first series resonator S1 is used to adjust the impedance of the filter, and the sixth series resonator S6 and the sixth parallel resonator P6 are used to form a stopband at the corresponding suppression location. It can be understood that the anti-resonance frequency point of the sixth series resonator S6 operates within the stopband; the resonant frequency point of the sixth parallel resonator P6 operates within the stopband. Figure 6 The middle curve 3 is the admittance curve of the sixth parallel resonator P6, whose resonant frequency point is 1.47 GHz, which is within the stop band; curve 4 is the admittance curve of the sixth series resonator S6, whose anti-resonance frequency point is 1.385 GHz, which is within the stop band; the sixth parallel resonator P6 and the sixth series resonator S6 form a band-stop filter outside the band, so that the band-pass filter with a stop band structure has a higher suppression level outside the band.

[0021] In this embodiment, the resonant frequency points of the second series resonator S2, the third series resonator S3, the fourth series resonator S4 and the fifth series resonator S5 operate within the passband of the filter; the anti-resonant frequency points of the first parallel resonator P1, the second parallel resonator P2, the third parallel resonator P3, the fourth parallel resonator P4 and the fifth parallel resonator P5 operate within the passband of the filter. In this embodiment, the passband structure and the stopband structure are separated by a preset distance, and the preset distance is set according to actual conditions, so that the passband structure and the stopband structure are separated by a large distance to achieve remote high suppression. Figure 5 Curve 1 is the admittance curve of the second series resonator S2, and its resonant frequency point is 1.734 GHz, which is within the filter passband; Curve 2 is the admittance curve of the first parallel resonator P1, and its anti-resonance frequency point is 1.713 GHz, which is within the filter passband. Multiple resonators form the passband of a bandpass filter with a stopband structure.

[0022] The bandpass filter including a stopband structure of the present invention includes a stopband structure and a passband structure. The passband structure is connected to the stopband structure. The stopband structure is connected to an input terminal 1. The stopband structure is also connected to an output terminal 2. The stopband structure includes a first series resonator S1, a sixth series resonator S6 and a sixth parallel resonator P6. The first series resonator S1 is used to adjust the filter impedance. The sixth series resonator S6 and the sixth parallel resonator P6 are used to form a stopband at a corresponding suppression location. The stopband structure and the passband structure are arranged at a preset distance to achieve high remote suppression. Figure 4 This is a simulation result diagram of the bandpass filter with a stopband structure of the present invention, wherein the passband is 1.675 GHz-1.775 GHz and the stopband is 1.375 GHz-1.475 GHz.

[0023] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bandpass filter with a stopband structure, characterized in that: The bandpass filter with a stopband structure comprises: A stopband structure and a passband structure, wherein the passband structure is connected to the stopband structure, the stopband structure is connected to the input end, and the stopband structure is also connected to the output end; The stopband structure and the passband structure are arranged at a preset distance.

2. The bandpass filter with a stopband structure according to claim 1, characterized in that: The stopband structure includes a first series resonator, one end of which is connected to the input end.

3. The bandpass filter with a stopband structure according to claim 2, characterized in that: The stopband structure further includes a sixth series resonator and a sixth parallel resonator, and a common end of the sixth series resonator and the sixth parallel resonator is connected to the output end.

4. The bandpass filter with a stopband structure according to claim 3, characterized in that: The passband structure includes a second parallel resonator, a third series resonator, a fourth series resonator, a fifth series resonator, a first parallel resonator, a second parallel resonator, a third parallel resonator, a fourth parallel resonator, and a fifth parallel resonator; The other end of the first series resonator is connected to one end of the first parallel resonator and a common end of the second series resonator, the other end of the first parallel resonator is grounded, the other end of the second series resonator and the common end of the second parallel resonator are connected to the third series resonator, the other end of the second parallel resonator is grounded, the other end of the third series resonator is respectively connected to the third parallel resonator and the fourth series resonator, the other end of the third parallel resonator is grounded, the other end of the fourth series resonator is connected to one end of the fifth series resonator, the other end of the fourth parallel resonator is grounded, the other end of the fifth series resonator is respectively connected to the fifth parallel resonator and the sixth series resonator, and the other end of the fifth parallel resonator is grounded.

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