A Surface Acoustic Wave Broadband Stop Filter

Abstract

The invention belongs to the technical field of filters, and specifically relates to a surface acoustic wave broadband band-stop filter; the filter comprises: at least two surface acoustic wave resonators connected in series, at least two surface acoustic wave resonators connected in parallel, and at least one spiral electrode structure; one end of the parallel surface acoustic wave resonator is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; one end of the spiral electrode structure is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; the invention improves the relative bandwidth of the surface acoustic wave band-stop filter, has good suppression of wide-frequency range noise signals, improves the performance of the surface acoustic wave band-stop filter, and can meet the needs of more radio frequency systems for suppressing wide-frequency range noise signals; at the same time, the invention is easy to realize in terms of process, can be promoted in any frequency band, and has high practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of filters, and in particular relates to a surface acoustic wave broadband band-stop filter. Background Art

[0002] As a frequency selection device, the filter can allow signals of a specific frequency to pass through while suppressing and attenuating signals of other frequencies. By using the frequency selection function of the filter, effective signals can be extracted and interference signals can be filtered out. The band-stop filter is a type of filter that can extract a wide range of useful signals while suppressing a small range of interference signals.

[0003] Surface acoustic wave filters are small in size, light in weight, and have good consistency, and are widely used in mobile communications and other fields. With the rapid development of communication technology, the electromagnetic environment is becoming increasingly complex, and the signal transmission and reception process is easily affected by interference signals, making it difficult to meet the needs of signal processing in complex environments. Conventional surface acoustic wave band-stop filters can achieve a narrow stopband bandwidth. Due to the insufficient stopband bandwidth, the filtering effect is poor, and the interference of wide-band noise signals to the RF system cannot be completely suppressed. Wide-bandwidth band-stop filters are highly consistent with the requirements of modern wireless communication device design, and there is an urgent need for surface acoustic wave band-stop filters with wide-bandwidth stopband suppression characteristics. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a surface acoustic wave broadband band-stop filter, which comprises: at least two surface acoustic wave resonators connected in series, at least two surface acoustic wave resonators connected in parallel and at least one spiral electrode structure; one end of the parallel surface acoustic wave resonator is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; one end of the spiral electrode structure is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded.

[0005] Preferably, the spiral electrode structure comprises a piezoelectric material (101), a spiral electrode (102), a signal output electrode (103), a signal input electrode (104) and a dielectric film (105); the spiral electrode (102), the signal output electrode (103), the signal input electrode (104) and the dielectric film (105) are all arranged on the piezoelectric material (101), the signal output electrode (103) is connected to the outer ring port of the spiral electrode (102), the signal input electrode (104) is connected to the inner ring port of the spiral electrode (102), and the dielectric film (105) covers the spiral electrode (102) to isolate the signal input electrode (104) from the rest of the spiral electrode (102) except the inner ring port.

[0006] Furthermore, the outer ring port or the inner ring port of the spiral electrode (102) is connected between the second surface acoustic wave resonator RS2 and the third surface acoustic wave resonator RS3, and the other port of the spiral electrode (102) is grounded.

[0007] Furthermore, the piezoelectric material (101) is lithium niobate with a YX tangent angle of 0 to 41 degrees.

[0008] Furthermore, the spiral electrode (102) is in the shape of a circular ring or a regular polygonal circular ring.

[0009] Preferably, the metal material in the surface acoustic wave resonator and the spiral electrode structure is a composite material consisting of one or at least two of titanium, aluminum, copper, platinum and gold.

[0010] Preferably, the interdigital period of the surface acoustic wave resonators connected in series is greater than the interdigital period of the surface acoustic wave resonators connected in parallel.

[0011] The beneficial effects of the present invention are as follows: the surface acoustic wave band-stop filter provided by the present invention has the characteristics of good passband flatness and large bandwidth. Compared with the traditional surface acoustic wave band-stop filter, the relative bandwidth of the surface acoustic wave band-stop filter is improved, and the noise signal in a wide frequency range is well suppressed. It can filter out interference signals with a relative bandwidth of the stopband greater than 10%, improve the performance of the surface acoustic wave band-stop filter, and meet the needs of more radio frequency systems for suppressing noise signals in a wide frequency range. At the same time, the present invention is easy to implement in terms of process, can be promoted in any frequency band, and has high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic structural diagram of the surface acoustic wave broadband band-stop filter in the present invention;

[0013] Figure 2 Schematic diagram of the spiral electrode structure when the spiral electrode is in the shape of a ring in the present invention;

[0014] Figure 3 Schematic diagram of the spiral electrode structure when the spiral electrode is in the shape of a regular polygon in the present invention;

[0015] Figure 4 The present invention is a flow chart for manufacturing a wideband surface acoustic wave band-stop filter;

[0016] Figure 5 The figure is a frequency response curve diagram of a broadband surface acoustic wave band-stop filter according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0018] The present invention provides a surface acoustic wave broadband band-stop filter, which comprises: at least two surface acoustic wave resonators connected in series, at least two surface acoustic wave resonators connected in parallel, and at least one spiral electrode structure; one end of the parallel surface acoustic wave resonator is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; one end of the spiral electrode structure is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded;

[0019] In some embodiments of the present invention, Figure 1 As shown, the SAW broadband band-stop filter comprises a first SAW resonator RS1, a second SAW resonator RS2, a third SAW resonator RS3, a fourth SAW resonator RS4, a fifth SAW resonator RP1, a sixth SAW resonator RP2 and a spiral electrode L1; the first SAW resonator RS1, the second SAW resonator RS2, the third SAW resonator RS3 and the fourth SAW resonator RS4 are connected in series; one end of the fifth SAW resonator RP1 is connected between the first SAW resonator RS1 and the second SAW resonator RS2, and the other end is grounded; the sixth SAW resonator RP2 is connected between the third SAW resonator RS3 and the fourth SAW resonator RS4, and the other end is grounded; one end of the spiral electrode structure L1 is connected between the second SAW resonator RS2 and the third SAW resonator RS3, and the other end is grounded. Preferably, the first SAW resonator RS1 is connected to the input terminal 1, and the fourth SAW resonator RS4 is connected to the output terminal 2.

[0020] The interdigital period of the surface acoustic wave resonators connected in series is greater than the interdigital period of the surface acoustic wave resonators connected in parallel.

[0021] like Figure 2 As shown, the spiral electrode structure includes a piezoelectric material 101, a spiral electrode 102, a signal output electrode 103, a signal input electrode 104 and a dielectric film 105; the spiral electrode 102, the signal output electrode 103, the signal input electrode 104 and the dielectric film 105 are all arranged on the piezoelectric material 101, the signal output electrode 103 is connected to the outer ring port of the spiral electrode 102, the signal input electrode 104 is connected to the inner ring port of the spiral electrode 102, and the dielectric film 105 covers the spiral electrode 102 to isolate the signal input electrode 104 from the rest of the spiral electrode 102 except the inner ring port.

[0022] Preferably, Figure 2 , Figure 3 As shown, the shape of the spiral electrode 102 is a ring or a regular polygonal ring. The spiral electrode can reduce the passband loss of the surface acoustic wave band stop filter, improve the useful signal extraction capability of the surface acoustic wave band stop filter, and enhance the overall performance of the surface acoustic wave band stop filter.

[0023] The outer loop port or the inner loop port of the spiral electrode 102 is connected between the second surface acoustic wave resonator RS2 and the third surface acoustic wave resonator RS3, and the other port of the spiral electrode 102 is grounded.

[0024] The piezoelectric material 101 is lithium niobate with a YX tangent of 0 to 41 degrees. This tangential piezoelectric material has a large electromechanical coupling coefficient, which can increase the relative bandwidth of the band-stop filter and filter out more interference signals.

[0025] Preferably, the metal material in the surface acoustic wave resonator and the spiral electrode structure is a composite material consisting of one or at least two of titanium, aluminum, copper, platinum and gold.

[0026] like Figure 4 As shown, the preparation of the broadband surface acoustic wave band-stop filter in the present invention includes the following contents:

[0027] S1: Obtain a piezoelectric substrate (piezoelectric material). The piezoelectric substrate may be lithium niobate with a YX tangent of 0 to 41°.

[0028] S2: Fabricate interdigital transducers and spiral electrodes on the upper surface of the piezoelectric substrate.

[0029] S3: Prepare a dielectric film on the spiral electrode. The size of the dielectric film needs to cover the center of the spiral electrode to one side of the input electrode, so as to isolate the signal input electrode from the rest of the spiral electrode except the inner ring port.

[0030] S4: preparing input and output electrodes connected to the spiral electrode, wherein the input electrode is located above the dielectric film and connected to the inner circle port of the spiral electrode, and the output electrode is connected to the outer circle port of the spiral electrode.

[0031] The performance of the present invention was evaluated:

[0032] like Figure 5 As shown, when the spiral electrode is in the shape of a ring, the surface acoustic wave band-stop filter has a band-stop performance of 40 dB in the frequency range of 483 MHz to 539 MHz with a relative bandwidth of 10.9%, and can filter out interference signals with a stopband relative bandwidth greater than 10%.

[0033] The surface acoustic wave band-stop filter provided by the present invention has the characteristics of good passband flatness and large bandwidth. Compared with the traditional surface acoustic wave band-stop filter, the relative bandwidth of the surface acoustic wave band-stop filter is improved, the noise signal in a wide frequency range is well suppressed, and interference signals with a relative bandwidth of the stopband greater than 10% can be filtered out, thereby improving the performance of the surface acoustic wave band-stop filter and meeting the needs of more radio frequency systems for suppressing noise signals in a wide frequency range. At the same time, the present invention is easy to implement in terms of process, can be promoted in any frequency band, and has high practicality.

[0034] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A surface acoustic wave broadband band-stop filter, characterized in that: include: At least two surface acoustic wave resonators connected in series, at least two surface acoustic wave resonators connected in parallel, and at least one spiral electrode structure; one end of the parallel surface acoustic wave resonator is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; one end of the spiral electrode structure is connected between the two surface acoustic wave resonators connected in series, and the other end is grounded; the spiral electrode structure comprises a piezoelectric material (101), a spiral electrode (102), a signal output electrode (103), a signal input electrode (104), and a dielectric film (105); The spiral electrode (102), the signal output electrode (103), the signal input electrode (104) and the dielectric film (105) are all arranged on the piezoelectric material (101); the signal output electrode (103) is connected to the outer ring port of the spiral electrode (102); the signal input electrode (104) is connected to the inner ring port of the spiral electrode (102); and the dielectric film (105) covers the spiral electrode (102) to isolate the signal input electrode (104) from the rest of the spiral electrode (102) except the inner ring port.

2. A surface acoustic wave broadband band-stop filter according to claim 1, characterized in that: The outer ring port or the inner ring port of the spiral electrode (102) is connected between the second surface acoustic wave resonator RS2 and the third surface acoustic wave resonator RS3, and the other port of the spiral electrode (102) is grounded.

3. The surface acoustic wave broadband band-stop filter according to claim 1, characterized in that: The piezoelectric material (101) is lithium niobate with a YX tangent of 0-41 degrees.

4. The surface acoustic wave broadband band-stop filter according to claim 1, characterized in that: The spiral electrode (102) is in the shape of a circular ring or a regular polygonal circular ring.

5. The surface acoustic wave broadband band-stop filter according to claim 1, characterized in that: The metal material in the surface acoustic wave resonator and the spiral electrode structure is a composite material consisting of one or at least two of titanium, aluminum, copper, platinum and gold.

6. The surface acoustic wave broadband band-stop filter according to claim 1, characterized in that: The interdigital period of the surface acoustic wave resonators connected in series is greater than the interdigital period of the surface acoustic wave resonators connected in parallel.

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