Surface plasmon polariton (SSPP) based bandpass filter

Abstract

This application provides a bandpass filter based on surface plasmon resonances (SSPPs), comprising: a dielectric substrate including a first plane and a second plane disposed opposite to each other; a feed section disposed on the first plane, including an input feed structure and an output feed structure, centrally symmetrical, for providing electromagnetic excitation; and a resonant section disposed on the second plane, horizontally and vertically symmetrical, corresponding to portions of the input feed structure and the output feed structure, for generating a passband under electromagnetic excitation; wherein the resonant section has a connected first slot structure and a second slot structure, wherein the first slot structure is horizontally and vertically symmetrical, and corresponding to portions of the input feed structure and the output feed structure; the second slot structure is horizontally and vertically symmetrical, for forming surface plasmon resonances. This application combines SSPPs and surface plasmon resonances (MSTs), effectively achieving miniaturization and high-performance design of the bandpass filter.

Description

Technical Field

[0001] The disclosed embodiments of this application relate to the field of wireless communication technology, and more specifically, to a bandpass filter based on artificial surface plasmon polaritons (SSPP). Background Technology

[0002] Microstrip bandpass filters possess significant advantages such as planar structure, mature fabrication technology, ease of integration, and low cost, leading to their widespread application in mobile communications, satellite terminals, radar transceivers, and RF front-end modules. Therefore, research on high-performance, wide-stopband bandpass filters with tunable passbands based on microstrip platforms has substantial engineering application value. Currently, traditional microstrip bandpass filters typically rely on resonator structures to achieve passband response. Their electrical dimensions are significantly limited by the operating wavelength, making further miniaturization difficult. Furthermore, microstrip structures have weak electromagnetic field containment capabilities, making them prone to radiated leakage and crosstalk, which can affect the normal operation of other components in the system. Summary of the Invention

[0003] According to an embodiment of this application, a bandpass filter is proposed to solve the above-mentioned problems.

[0004] According to aspects of this application, an exemplary bandpass filter is disclosed, comprising: a dielectric substrate including a first plane and a second plane disposed opposite to each other; a feed section disposed on the first plane, including an input feed structure and an output feed structure, centrally symmetrical, for providing electromagnetic excitation; and a resonant section disposed on the second plane, horizontally and vertically symmetrical, respectively corresponding to portions of the input feed structure and the output feed structure, for generating a passband under electromagnetic excitation; wherein the resonant section is provided with a first slot structure and a second slot structure that are connected, wherein the first slot structure is horizontally and vertically symmetrical, and respectively corresponding to portions of the input feed structure and the output feed structure; the second slot structure is horizontally and vertically symmetrical, for forming artificial surface plasmons.

[0005] In some embodiments, the second groove structure includes a preset number of artificial surface plasmon resonance units, which are horizontal and vertically symmetrical; wherein the preset number of artificial surface plasmon resonance units are uniformly arranged along the direction of the first groove structure and are connected to the first groove structure.

[0006] In some embodiments, the artificial surface plasmon unit includes a pair of horizontally symmetrical and interconnected barbed grooves.

[0007] In some embodiments, the first groove structure includes a first square groove, a wire groove, and a second square groove connected in sequence, wherein the first square groove and the second square groove are symmetrically arranged with respect to the middle vertical direction of the wire groove.

[0008] In some embodiments, the width of the first square groove or the second square groove is greater than the width of the wire groove.

[0009] In some embodiments, the preset number of artificial surface plasmon resonance units are uniformly arranged along the direction of the groove, and the artificial surface plasmon resonance units are connected to the groove at a horizontally symmetrical position of the artificial surface plasmon resonance units.

[0010] In some embodiments, the bandpass filter further includes a control unit disposed on the first plane and corresponding to the center portion of the pair of barbed slots.

[0011] In some embodiments, the input feed structure and the output feed structure are arranged symmetrically with respect to the center of the first plane, and include a first feed section, a second feed section and a third feed section connected in sequence, wherein the widths of the second feed section, the first feed section and the third feed section increase sequentially.

[0012] In some embodiments, the third feed line portion is disposed corresponding to the first square groove or the second square groove portion, the third feed line portion is disposed corresponding to the center portion of the pair of barbed grooves, and the third feed line portion is disposed corresponding to one end of one of the barbed grooves of the pair of barbed grooves.

[0013] In some embodiments, the third feed line portion is provided with a slot, wherein the slot is closer to one side and farther from the other side in both the horizontal and vertical directions of the third feed line portion. The beneficial effects of this application are as follows: the resonant part is provided with a connected first slot structure and a second slot structure, wherein the first slot structure is respectively provided with the input feed line structure and the output feed line structure, and the second slot structure is used to form SSPP, realizing the combination of SSPP and MST structure, effectively realizing the miniaturization and high-performance design of bandpass filter. These and other objectives of this application will undoubtedly be apparent to those skilled in the art after reading the following detailed description of the figures and the preferred embodiments illustrated therein. Attached Figure Description

[0014] Figure 1 This is a perspective view of a bandpass filter according to an embodiment of this application.

[0015] Figure 2 This is a top view schematic diagram of a bandpass filter according to an embodiment of this application.

[0016] Figure 3 This is a bottom view schematic diagram of a bandpass filter according to an embodiment of this application.

[0017] Figure 4 This is an enlarged schematic diagram of the SSPP unit in a bandpass filter according to an embodiment of this application.

[0018] Figure 5 This is a dispersion curve diagram of the SSPP unit in the bandpass filter according to an embodiment of this application.

[0019] Figure 6 This is a graph of the S-parameter response of a bandpass filter according to an embodiment of this application. Detailed Implementation

[0020] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0021] In the following description, specific details such as particular system architectures, interfaces, and technologies are presented for illustrative purposes rather than for limiting purposes, in order to provide a thorough understanding of this application.

[0022] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, "many" in this document means two or more. Moreover, the term "at least one" in this document means any combination of at least two of any one or more of a plurality of objects. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0023] like Figures 1-4 The diagram shown is a schematic representation of a bandpass filter 100 according to an embodiment of this application. The bandpass filter 100 includes a dielectric substrate 110, a feed line portion 120, and a resonant portion 130.

[0024] The dielectric substrate 110 includes a first plane 111 and a second plane 112 disposed opposite to each other. A feed line portion 120 is disposed on the first plane 111, including an input feed line structure F1 and an output feed line structure F2, which are centrally symmetrical and used to provide electromagnetic excitation. A resonant portion 130 is disposed on the second plane 112, which is horizontally and vertically symmetrical, and is respectively disposed corresponding to portions of the input feed line structure F1 and the output feed line structure F2, used to generate a passband under electromagnetic excitation.

[0025] Both the feed line section 120 and the resonant section 130 are implemented using metal layers on the dielectric substrate 110. The feed line section 120 is implemented using a metal layer on the first plane 111 of the dielectric substrate 110, and the resonant section 130 is implemented using a metal layer on the second plane 112 of the dielectric substrate 110. The input feed line structure F1 and the output feed line structure F2 of the feed line section 120 are centrally symmetrical, that is, the feed line section 120 is centrally symmetrical. The resonant section 130 is horizontally and vertically symmetrical, that is, the feed line section 120 itself is centrally symmetrical, and the resonant section 130 itself is horizontally and vertically symmetrical. Thus, the feed line section 120 and the resonant section 130 are connected in the horizontal direction and in the vertical direction, so the bandpass filter 100 itself is also a symmetrical structure.

[0026] The resonant section 130 is partially configured to correspond with the input feed structure F1, and partially configured to correspond with the output feed structure F2. In other words, portions of the resonant section 130 are configured corresponding to or opposite to portions of the input feed structure F1, and portions of the resonant section 130 are configured corresponding to or opposite to portions of the output feed structure F2, thereby forming coupling between the input feed structure F1, the output feed structure F2, and the resonant section 130. Thus, under the electromagnetic excitation provided by the input feed structure F1 and the output feed structure F2, the resonant section 130 generates a passband through the coupling between the input feed structure F1, the output feed structure F2, and the resonant section 130.

[0027] The resonant section 130 is provided with a first slot structure c1 and a second slot structure c2 that are connected. The first slot structure c1 is horizontal and vertically symmetrical, and is respectively provided with the input feed line structure F1 and the output feed line structure F2. The second slot structure c2 is horizontal and vertically symmetrical and is used to form artificial surface plasmon polaritons (SSPP).

[0028] On the dielectric substrate 111, the structure formed by the feed line portion 120 and the first slot structure c1 is a microstrip-to-slotline transition (MST) structure. The MST structure, as a high-pass structure, exhibits high-pass characteristics. The artificial surface plasmon formed by the second slot structure c2 exhibits low-pass characteristics. A portion of the first slot structure c1 corresponds to or is opposite to a portion of the input feed line structure F1, and a portion of the first slot structure c1 corresponds to or is opposite to a portion of the output feed line structure F2. Therefore, in this bandpass filter 100, combining the high-pass characteristics of the MST structure and the low-pass characteristics of the second slot structure c2, under the electromagnetic excitation provided by the input feed line structure F1 and the output feed line structure F2, a bandpass characteristic is formed through the coupling between the input feed line structure F1 and the output feed line structure F2 and the resonant portion 130, thereby generating a passband on the second plane 112 of the dielectric substrate 110.

[0029] It should be noted that, Figure 1 This is a perspective view from a top angle, in which the metal layer on the first plane 111 of the dielectric substrate 110 is shown in the light.

[0030] In this embodiment, the resonant part 130 is provided with a connected first slot structure c1 and a second slot structure c2. The first slot structure c1 is partially corresponding to the input feed line structure F1 and the output feed line structure F2. The second slot structure c2 is used to form SSPP, realizing the combination of SSPP and MST structure, effectively realizing the miniaturization and high-performance design of bandpass filter 100.

[0031] In some embodiments, such as Figure 1 and Figure 3 As shown, the second groove structure c2 includes a preset number of artificial surface plasmon units c21, which are horizontal and vertically symmetrical; wherein the preset number of artificial surface plasmon units c21 are uniformly arranged along the direction of the first groove structure c1 and are connected to the first groove structure c1.

[0032] exist Figure 3 In the example, the preset quantity can be 3, meaning that in the bandpass filter 100, the second slot structure c2 includes 3 SSPP units c21. The artificial surface plasmon resonance units c21 are horizontally and vertically symmetrical, that is, the SSPP unit c21 itself is a horizontally and vertically symmetrical structure. The 3 SSPP units c21 are evenly arranged along the direction of the first slot structure c1, that is, the interval between two adjacent SSPP units c21 is the same. The 3 SSPP units c21 are connected to the first slot structure c1. For example, the position where the 3 SSPP units c21 are connected to the first slot structure c1 is located at a horizontally symmetrical position of the 3 SSPP units c21, that is, the 3 SSPP units c21 are horizontally symmetrical about the center horizontal direction of the first slot structure c1.

[0033] In some embodiments, such as Figure 1 , Figure 3 and Figure 4 As shown, the artificial surface plasmon unit c21 includes a pair of horizontally symmetrical and interconnected barbed grooves c211.

[0034] SSPP unit c21 includes a pair of barbed grooves c211, each barbed groove c211 including a main groove g1 and an I-shaped groove g2, wherein the four branch grooves g22 of the I-shaped groove g2 are bent inward to form a barb. In some examples, the main groove g1 and the I-shaped groove g2 have the same width, the length of the main groove g1 is slightly less than the length of the middle groove g21 of the I-shaped groove g2, and the length of the branch grooves g22 of the I-shaped groove g2 is greater than the length of the main groove g1 and the length of the middle groove g21 of the I-shaped groove g2.

[0035] In some embodiments, such as Figure 1 and Figure 3 As shown, the first groove structure c1 includes a first square groove c11, a wire groove c13 and a second square groove c12 connected in sequence, wherein the first square groove c11 and the second square groove c12 are symmetrically arranged in the middle vertical direction relative to the wire groove c13.

[0036] The first square groove c11 and the second square groove c12 are symmetrically arranged in the middle vertical direction with respect to the wire groove c13, that is, the first square groove c11 and the second square groove c12 are symmetrical with respect to the middle position of the wire groove c13.

[0037] Furthermore, in some embodiments, such as Figure 1 and Figure 3 As shown, the width of the first square groove c11 or the second square groove c12 is greater than the width of the wire groove c13.

[0038] The width of the first square groove c11 or the second square groove c12 is much larger than the width of the wire groove c13. For example, the width of the first square groove c11 or the second square groove c12 can be tens or even hundreds of times the width of the wire groove c13.

[0039] In some embodiments, such as Figure 1 and Figure 3 As shown, a preset number of artificial surface plasmon units c21 are uniformly arranged along the direction of the groove c13, and the artificial surface plasmon units c21 are connected to the groove c13 at the horizontally symmetrical position of the artificial surface plasmon units c21.

[0040] The artificial surface plasmon unit c21 is connected to the slot c13 at a horizontally symmetrical position, that is, at the middle horizontal position of the artificial surface plasmon unit c21. In some examples, the slot width of the artificial surface plasmon unit c21 can be the same as the slot width of the slot c13.

[0041] In some embodiments, such as Figure 1 and Figure 2 As shown, the bandpass filter 100 also includes a control unit 140, which is disposed on the first plane 111 and is disposed corresponding to the center portion of a pair of barbed grooves c211.

[0042] The control unit 140 can be a metal layer on the first plane 111 of the dielectric substrate 110. In other words, the control unit 140 can be implemented through the metal layer of the first plane 111. The control unit 140 is partially aligned with the center of a pair of barbed slots c211, that is, the control unit 140 is partially aligned with the center of the SSPP unit c21. Therefore, the control unit 140 can be used to control the equivalent wave impedance of the SSPP unit c21, making it closer to the impedance of the MST, thereby reducing the matching difficulty and improving the return loss of the bandpass filter 100.

[0043] In some embodiments, such as Figure 1 and Figure 2 As shown, the input feeder structure F1 and the output feeder structure F2 are arranged symmetrically with respect to the center of the first plane 111, and include a first feeder section F11 or F21, a second feeder section F12 or F22 and a third feeder section F13 or F23 connected in sequence, with the widths of the second feeder section F12 or F22, the first feeder section F11 or F21 and the third feeder section F13 or F23 increasing sequentially.

[0044] The equivalent impedance of the first feed line section F11 or F21 can be 50 ohms, meaning the width of the first feed line section F11 or F21 is the width corresponding to 50 ohms on the dielectric substrate 110. The length of the second feed line section F12 or F22 is less than that of the first feed line section F11 or F21. The third feed line section F13 or F23 can be square, and the size of the third feed line section F13 or F23 can be greater than the size of the first square slot c11 or the second square slot c12, meaning the width of the third feed line section F13 or F23 is greater than the width of the first square slot c11 or the second square slot c12.

[0045] Furthermore, in some embodiments, such as Figure 1 and Figure 2 As shown, the third feed line part F13 or F23 is partially corresponding to the first square slot c11 or the second square slot c12. The third feed line part F13 or F23 is partially corresponding to the center part of a pair of barbed slots c211, and the third feed line part F13 or F23 is positioned close to one end of one of the barbed slots c211.

[0046] like Figure 1 As shown, the third feed line section F13 or F23 is configured to correspond to the first square slot c11 or the second square slot c12. That is, a portion of the third feed line section F13 or F23 is configured to correspond to or be opposite to a portion of the first square slot c11 or the second square slot c12, thereby forming a coupling between the input feed line structure F1 and the output feed line structure F2 and the resonant section 130.

[0047] The third feed section F13 or F23 is configured to correspond to the center portion of a pair of barbed slots c211. Specifically, a portion of the third feed section F13 or F23 corresponds to a portion of the center of the pair of barbed slots c211, and vice versa. This allows the third feed section F13 or F23 to be used to adjust the equivalent impedance of the SSPP unit c21, bringing it closer to the impedance of the MST, thereby reducing matching difficulty and improving the return loss of the bandpass filter 100. In other words, for the three SSPP units c21, specifically the first SSPP unit c21 on the left and the third SSPP unit c21 on the right, the third feed section F13 or F23 of the input feed structure F1 or output feed structure F2 also functions as a control section 140 to adjust the equivalent impedance of these two SSPP units c21, bringing it closer to the impedance of the MST, thus reducing matching difficulty and improving the return loss of the bandpass filter 100. It can be seen that the third feed section F13 or F23 of the input feed structure F1 or the output feed structure F2 is not only used to provide electromagnetic excitation, but also serves as the control section 140, realizing an integrated design and a transitionless structure design, further improving the miniaturization effect.

[0048] It should be noted that, in Figure 1 In the example, the bandpass filter 100 has three SSPP units c21, and correspondingly, it should have three control units 140 to control the equivalent impedance of each of the three SSPP units c21. Figure 1 and Figure 2 As shown, since the third feed section F13 or F23 of the input feed structure F1 and the output feed structure F2, the bandpass filter 100 has one control section 140.

[0049] The third feed line section F13 or F23 is positioned near one end of one of the barbed slots c211 in a pair of barbed slots c211, that is, the third feed line section F13 or F23 is positioned near one end of the SSPP unit c21 to cover one end of the SSPP unit c21.

[0050] Specifically, such as Figure 1As shown, one side of the third feed line section F13 or F23 is flush with the bent portion of the I-shaped slot g2 of the SSPP unit c21. The distance from one side of the third feed line section F13 or F23 to one side of the corresponding parallel first square slot c11 is different, and the distance from one side of the third feed line section F13 or F23 to one side of the SSPP unit c21 is also different. The first feed line section F11 or F21 and the second feed line section F12 or F22 are partially corresponding to the SSPP unit c21. For example, portions of the first feed line section F11 or F21 and the second feed line section F12 or F22 can be partially corresponding to one side of a barbed slot c211 of the SSPP unit c21.

[0051] In some embodiments, such as Figure 1 and Figure 2 As shown, the third feeder section F13 or F23 is provided with a slot F131 or F231. The slot F131 or F231 of the third feeder section F13 or F23 is closer to one side and farther away from the other side in both the horizontal and vertical directions.

[0052] The third feed section F13 or F23 is provided with a slot F131 or F231. The size of the slot F131 or F231 is smaller than the size of the third feed section F13 or F23. That is, the third feed section F13 or F23 is locally slotted, which can suppress the excitation and propagation of higher-order modes, thereby enhancing the out-of-band suppression performance and widening the stopband range.

[0053] like Figure 5 and Figure 6 As shown, it describes Figures 1-4 The electromagnetic simulation results of the bandpass filter 100 shown are as follows: Figure 5 This is the dispersion curve of SSPP unit c21 in bandpass filter 100. Figure 6 This is a graph of the S-parameters of the response of bandpass filter 100.

[0054] It can be seen that the center frequency of this bandpass filter 100 is 4.36 GHz, and its size is 0.4 × 0.28 mm. λg 2 ,in λg With a waveguide wavelength of 4.36 GHz, it has advantages such as compact structure, easy integration, and suitability for planar fabrication.

[0055] By loading a control section 140 on the back of the SSPP unit c21 and combining it with a design that incorporates slots F131 or F231 in the third feed section F13 or F23, the coupling strength and equivalent impedance can be effectively controlled, achieving compact matching and significantly improving return loss, which is no higher than -20 dB. Simultaneously, reflection loss is reduced and power transmission efficiency is improved. Furthermore, the slots F131 or F231 in the third feed section F13 or F23 can suppress the excitation and propagation of higher-order modes, thereby enhancing out-of-band suppression performance and widening the stopband range, allowing the upper stopband limit to reach 9.8 GHz.

[0056] Those skilled in the art will readily recognize that numerous modifications and variations can be made to the apparatus and method while maintaining the teachings of this application. Therefore, the above disclosure should be considered limited only by the scope of the appended claims.

Claims

1. A bandpass filter, characterized in that, include: A dielectric substrate includes a first plane and a second plane disposed opposite to each other; The feeder section, disposed on the first plane, includes an input feeder structure and an output feeder structure, which are centrally symmetrical and are used to provide electromagnetic excitation; as well as The resonant section is disposed on the second plane, and is horizontally and vertically symmetrical. It is respectively disposed corresponding to the input feed structure and the output feed structure, and is used to generate a passband under electromagnetic excitation. The resonant section is provided with a first slot structure and a second slot structure that are connected. The first slot structure is horizontal and vertically symmetrical, and is respectively provided with the input feed line structure and the output feed line structure. The second slot structure is horizontal and vertically symmetrical, and is used to form artificial surface plasmons.

2. The bandpass filter according to claim 1, characterized in that, The second groove structure includes a preset number of artificial surface plasmon units, which are horizontally and vertically symmetrical. The predetermined number of artificial surface plasmon units are uniformly arranged along the direction of the first slot structure and are connected to the first slot structure.

3. The bandpass filter according to claim 2, characterized in that, The artificial surface plasmon unit includes a pair of horizontally symmetrical and interconnected barbed grooves.

4. The bandpass filter according to any one of claims 1-3, characterized in that, The first groove structure includes a first square groove, a line groove, and a second square groove connected in sequence, wherein the first square groove and the second square groove are symmetrically arranged in the vertical direction relative to the middle of the line groove.

5. The bandpass filter according to claim 4, characterized in that, The width of the first square groove or the second square groove is greater than the width of the wire groove.

6. The bandpass filter according to claim 5, characterized in that, The preset number of artificial surface plasmon resonance units are evenly arranged along the direction of the groove, and the artificial surface plasmon resonance units are connected to the groove at the horizontally symmetrical position of the artificial surface plasmon resonance units.

7. The bandpass filter according to any one of claims 1-3, characterized in that, It also includes a control unit, which is disposed on the first plane and is disposed corresponding to the center portion of the pair of barbed grooves.

8. The bandpass filter according to claim 7, characterized in that, The input feed structure and the output feed structure are arranged symmetrically with respect to the center of the first plane, and include a first feed section, a second feed section and a third feed section connected in sequence, with the widths of the second feed section, the first feed section and the third feed section increasing sequentially.

9. The bandpass filter according to claim 8, characterized in that, The third feed line portion is configured to correspond to the first square groove or the second square groove portion, and the third feed line portion is configured to correspond to the center portion of the pair of barbed grooves, and the third feed line portion is configured to correspond to one end of one of the barbed grooves.

10. The bandpass filter according to claim 8 or 9, characterized in that, The third feeder section is provided with a slot, and the slot is closer to one side and farther away from the other side in both the horizontal and vertical directions of the third feeder section.

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