Non-grounded anisotropic metasurface diaphragm for inhibiting evanescent waves in compact cavity

Abstract

The invention provides a non-grounded anisotropic metasurface diaphragm for inhibiting evanescent waves in a compact cavity, and belongs to the field of cavity filters, the non-grounded anisotropic metasurface diaphragm comprises a cavity, metasurface diaphragms and a mushroom-shaped structure are arranged in the cavity, the mushroom-shaped structure is located between the two metasurface diaphragms, and the mushroom-shaped structure is located between the two metasurface diaphragms. And coaxial feed probes are symmetrically arranged on the outer side of the metasurface diaphragm and penetrate through the lower wall of the cavity. By adopting the non-grounded anisotropic metasurface diaphragm for suppressing the evanescent waves in the compact cavity, noise suppression of the evanescent waves in a broadband range is realized.

Description

Technical Field

[0001] The invention relates to the field of cavity filters, and in particular to a non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity. Background Art

[0002] With the rapid advancement of fifth-generation mobile communication technology, artificial intelligence and the Internet of Things, there is a more urgent need for miniaturization of high-performance circuits, integration of RF circuits and compactness of design. In this context, the number of noise sources in circuit systems has increased dramatically, and the distance between these noise sources and potential interfered objects has been reduced. The problem of RF interference has become increasingly prominent and has attracted widespread attention.

[0003] To meet this challenge, shielded packaging technology for circuits and systems has been widely used, which has shown an indispensable role in effectively reducing external emission noise of the package. However, driven by cost control, circuits and systems tend to adopt shared metal packaging solutions, which inevitably leads to internal RF interference problems between components or subsystems.

[0004] There are currently two major challenges for RFI suppression in cavities. The primary challenge stems from the shrinking gap space. Traditional internal RFI suppression methods rely on short-circuit metal walls to achieve excellent cavity shielding performance. However, high-density circuit layouts make the space reserved for short-circuit structures increasingly limited. To address this issue, existing technologies have explored a variety of methods that do not rely on short-circuit structures, such as electromagnetic bandgap structures, lossy materials, metamaterials, and metasurface membranes. Although these methods have alleviated the interference problem to a certain extent, they still have certain limitations.

[0005] Another major challenge is the emerging problem of evanescent wave coupling. With the continuous expansion of the operating frequency band of RF front-end chips, especially in compact shielded cavities, the cutoff frequency is gradually increasing. This results in less interference with low-frequency components when they are far away from the cutoff frequency, and the attenuation effect of the evanescent wave is more obvious. However, as the necessary frequency band gradually approaches the cutoff frequency, the evanescent wave coupling phenomenon becomes more and more significant, and effective suppression measures must be taken. It is worth noting that all current ungrounded shielding designs focus on suppressing propagating waves in the cavity. However, the industry has not yet reported an ungrounded, broadband evanescent wave suppression method specifically developed to address the challenges of miniaturized cavities.

[0006] Therefore, it is particularly urgent to develop and design shielding technology that is suitable for compact metal shielding cavities and has the characteristics of being ungrounded, small lateral size, and wide operating bandwidth. Summary of the invention

[0007] The object of the present invention is to provide a non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, and to place the non-grounded anisotropic metasurface diaphragm in a cavity package to achieve evanescent wave noise suppression in a broadband range.

[0008] To achieve the above-mentioned objectives, the present invention provides a non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, comprising a cavity, wherein a metasurface diaphragm and a mushroom-shaped structure are arranged inside the cavity, wherein the mushroom-shaped structure is located between two metasurface diaphragms, and coaxial feeding probes are symmetrically arranged on the outside of the metasurface diaphragm, and the coaxial feeding probes pass through the lower wall of the cavity.

[0009] Preferably, a capacitive metasurface is provided on the metasurface diaphragm, the capacitive metasurface is composed of vertical grooves and transverse grooves, and a lumped capacitor and a lumped resistor are arranged on the capacitive metasurface, the lumped capacitor is placed in the vertical groove, and the lumped resistor is placed in the transverse groove.

[0010] Preferably, the mushroom-shaped structure includes a metal patch and a first metal through hole, the metal patch is attached to the surface of the mushroom-shaped structure, the first metal through hole is arranged on the metal patch, and the first metal through hole passes through the mushroom-shaped structure.

[0011] Preferably, the super-surface diaphragm and the mushroom-shaped structure partially fill the cross-section of the cavity, the super-surface diaphragm and the mushroom-shaped structure are close to the upper wall of the wall, the distance between the super-surface diaphragm and the lower wall of the cavity is greater than 2 mm, and the distance between the mushroom-shaped structure and the lower wall of the cavity is greater than 7 mm.

[0012] Preferably, the metasurface diaphragm includes a high-frequency non-grounded anisotropic metasurface diaphragm and a low-frequency non-grounded anisotropic metasurface diaphragm, and the capacitance values ​​of the lumped capacitors on the high-frequency non-grounded anisotropic metasurface diaphragm and the low-frequency non-grounded anisotropic metasurface diaphragm are different.

[0013] Preferably, the upper surface of the super-surface diaphragm is covered with copper, and the lower surface of the mushroom-shaped structure is covered with copper.

[0014] Preferably, the spacing between the high-frequency non-grounded anisotropic metasurface diaphragm and the low-frequency non-grounded anisotropic metasurface diaphragm and the mushroom-shaped structure is the same.

[0015] Therefore, the present invention adopts the above-mentioned non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, and the technical effects are as follows: 1. While keeping the inherent attenuation inside the package cavity unchanged, the metasurface diaphragm structure partially fills the cavity cross section and introduces additional transmission zeros in the target frequency band; 2. The super-surface diaphragm is not grounded, and the distance from the bottom wall of the cavity is greater than 2 mm, and has a small lateral size; 3. By embedding capacitors into the metasurface, the size of the lateral capacitance can be controlled, and the position of the transmission zero point can be easily adjusted; 4. Multiple metasurface membranes are combined to achieve multi-order filter effects; 5. Compared with traditional shielding methods, it has the advantages of small lateral size, non-grounding, wide working bandwidth, no parasitic transmission poles and evanescent wave suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of a third-order band-stop filter composed of a non-grounded anisotropic metasurface diaphragm of the present invention; Figure 2 A side view of the overall structure of a third-order band-stop filter composed of a non-grounded anisotropic metasurface diaphragm of the present invention; Figure 3 This is a front view of the high-frequency non-grounded anisotropic metasurface diaphragm of the present invention; Figure 4 This is a front view of the mushroom-shaped structure of the present invention; Figure 5 This is a front view of the low-frequency non-grounded anisotropic metasurface diaphragm of the present invention; Figure 6 It is a schematic diagram of assembling the third-order band-stop filter of the present invention; Figure 7 The simulation and test S parameters of the first-order band-stop filter performance of the present invention without the non-grounded anisotropic metasurface diaphragm and with the non-grounded anisotropic metasurface diaphragm with a transmission coefficient further reduced by 10 dB; Figure 8 The simulation and test S parameters of the performance of the second-order band-stop filter of the present invention without the non-grounded anisotropic metasurface diaphragm and with the non-grounded anisotropic metasurface diaphragm with a transmission coefficient further reduced by 10 dB; Fig. 9 The present invention provides simulation and test parameters for the performance of a third-order band-stop filter without a non-grounded anisotropic metasurface diaphragm and with a non-grounded anisotropic metasurface diaphragm, in which the transmission coefficient is further reduced by 10 dB.

[0017] Reference numerals 1. High-frequency non-grounded anisotropic metasurface diaphragm; 2. Mushroom-shaped structure; 3. Low-frequency non-grounded anisotropic metasurface diaphragm; 4. First lumped capacitor; 5. First lumped resistor; 6. Metal patch; 7. First metal through hole; 8. Second lumped capacitor; 9. Second lumped resistor; 10. Standard WR-90 coaxial-waveguide converter; 11. Actual model of high-frequency non-grounded anisotropic metasurface diaphragm; 12. 4mm thick WR-90 waveguide section; 13. Actual model of low-frequency non-grounded anisotropic metasurface diaphragm; 14. First coaxial feeding probe; 15. Second metal through hole; 16. Actual model of mushroom-shaped structure; 17. Second coaxial feeding probe. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0019] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0020] Embodiment 1 like Figure 1-Figure 2 As shown, the present invention provides a non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, including a cavity, a metasurface diaphragm and a mushroom-shaped structure 2 are arranged inside the cavity, the mushroom-shaped structure 2 is located between two metasurface diaphragms, and coaxial feeding probes are symmetrically arranged outside the metasurface diaphragms, and the coaxial feeding probes penetrate the lower wall of the cavity. The metasurface diaphragm and the mushroom-shaped structure 2 are partially filled in the cross section of the cavity, the metasurface diaphragm and the mushroom-shaped structure 2 are close to the upper wall of the wall, the metasurface diaphragm and the lower wall of the cavity are kept at a distance greater than 2 mm, and the mushroom-shaped structure 2 and the lower wall of the cavity are kept at a distance greater than 7 mm.

[0021] The metasurface diaphragm includes a high-frequency non-grounded anisotropic metasurface diaphragm 1 and a low-frequency non-grounded anisotropic metasurface diaphragm 3. The high-frequency non-grounded anisotropic metasurface diaphragm 1 and the low-frequency non-grounded anisotropic metasurface diaphragm 3 are both rectangular, and the selected material is Rogers RT / duroid 6010 / 6010LM, with a relative dielectric constant of 10.2, a loss tangent of 0.002, and a thickness of 0.508mm. The mushroom-shaped structure 2 is rectangular, and the selected material is FR4, with a relative dielectric constant of 4.4, a loss tangent of 0.02, and a thickness of 3mm. The spacing between the high-frequency non-grounded anisotropic metasurface diaphragm 1, the low-frequency non-grounded anisotropic metasurface diaphragm 3 and the mushroom-shaped structure 2 is 0.5mm. The upper surface of the metasurface diaphragm is covered with copper, and the lower surface of the mushroom-shaped structure 2 is covered with copper, and the thickness of the copper is 0.017mm.

[0022] like Figure 3-Figure 5 As shown, Figure 3 and Figure 5 They are the specific structures of the high-frequency non-grounded anisotropic metasurface diaphragm 1 and the low-frequency non-grounded anisotropic metasurface diaphragm 3, Figure 4 It is the specific structure of the mushroom-type structure 2. A capacitive metasurface is provided on the metasurface diaphragm, and the capacitive metasurface is composed of vertical grooves and transverse grooves. Lumped capacitors and lumped resistors are arranged on the capacitive metasurface. The lumped capacitor is placed in the vertical groove to control the transverse capacitance and adjust the transmission zero point. The lumped resistor is placed in the transverse groove to suppress the evanescent wave coupling effect of the transverse groove and avoid the generation of parasitic transmission poles and zero points. The mushroom-type structure 2 includes a metal patch 6 and a first metal through hole 7. The metal patch 6 is attached to the surface of the mushroom-type structure 2. The first metal through hole 7 is arranged on the metal patch 6. The first metal through hole 7 runs through the mushroom-type structure 2.

[0023] The resistance values ​​of the lumped resistors on the high-frequency non-grounded anisotropic metasurface diaphragm 1 and the low-frequency non-grounded anisotropic metasurface diaphragm 3 are the same, and the capacitance values ​​of the lumped capacitors on the high-frequency non-grounded anisotropic metasurface diaphragm 1 and the low-frequency non-grounded anisotropic metasurface diaphragm 3 are different. The resistance values ​​of the first lumped resistor 5 and the second lumped resistor 9 are both 36Ω, the capacitance value of the first lumped capacitor 4 is 0.1pF, and the capacitance value of the second lumped capacitor 8 is 0.35pF.

[0024] The non-grounded anisotropic metasurface diaphragm can introduce transmission zeros below the cutoff frequency of the packaging cavity, and its lateral size is relatively small, maintaining a distance of 2 mm. Since inserting a capacitive metasurface into the packaging cavity will introduce additional parasitic transmission poles and zeros, the present invention adopts a method of embedding resistors into the lateral gap to destroy the momentum matching condition, thereby suppressing additional resonance and coupling, and at the same time changing the electric field coupling path to suppress the transmission zeros above the cutoff frequency. Since the gap coupling capacitance of the capacitive metasurface itself is too small to work normally below the cutoff frequency of the packaging cavity, the present invention further adopts a method of embedding capacitors into vertical gaps to achieve effective control of lateral capacitance and adjust the transmission zeros in the desired frequency band, thereby achieving excellent evanescent wave suppression performance. The mushroom-type structure 2 itself does not introduce a specific transmission zero, but after coupling with the non-grounded anisotropic metasurface diaphragm, it provides an additional phase for the electric field, so that the anisotropic metasurface diaphragm can introduce additional transmission zeros, further expanding the suppression bandwidth.

[0025] HFSS2022 is used to simulate, process and test the non-grounded anisotropic metasurface diaphragm designed to be placed in the packaging cavity to achieve broadband evanescent wave suppression performance.

[0026] like Figure 6As shown, the experimental assembly schematic diagram of the non-grounded anisotropic metasurface diaphragm placed in the packaging cavity to achieve the performance of the third-order evanescent wave band-stop filter in the present invention, the entire test framework includes a standard WR-90 coaxial-waveguide converter 10, a high-frequency non-grounded anisotropic metasurface diaphragm actual model 11, a 4mm thick WR-90 waveguide segment 12, a low-frequency non-grounded anisotropic metasurface diaphragm actual model 13, a first coaxial feeding probe 14, a second coaxial feeding probe 17, a second metal through hole 15 and a mushroom-type structure actual model 16. In order to facilitate assembly and testing, the design of the non-grounded anisotropic metasurface diaphragm is consistent with the size of the waveguide flange, but the actual effective area is maintained at 22.86×8 square millimeters, and the second metal through holes 15 are densely placed around to prevent electromagnetic wave leakage; the mushroom-type structure actual model 16 is placed on the top wall of the 4mm thick WR-90 waveguide segment 12; the first coaxial feeding probe 14 and the second coaxial feeding probe 17 are used to simulate the unintentional noise radiation of the active device inside the packaging cavity.

[0027] Figure 7 , Figure 8 , Fig. 9 The simulation and test S parameters of the performance of the first-order, second-order and third-order band-stop filters of the present invention are respectively without the non-grounded anisotropic metasurface diaphragm and with the non-grounded anisotropic metasurface diaphragm when the transmission coefficient is further reduced by 10 dB.

[0028] Figure 7 As shown, before the non-grounded anisotropic metasurface diaphragm is inserted, that is, in the empty package cavity, the transmission coefficient gradually decreases with frequency because the waves below the cutoff frequency are evanescent, and the attenuation is more significant at lower frequencies. Due to the small distance between the two coaxial feeding probes, the coupling is still around -30dB near 6GHz, which increases the risk of RF electromagnetic interference in the Sub-6G module. In contrast, after the non-grounded anisotropic metasurface diaphragm is applied, a transmission zero is introduced below the cutoff frequency, and the transmission coefficient is lower than -61dB at 5.63GHz, at which time the isolation is improved by about 25dB, and the overall coupling within 5.5-5.89GHz is lower than -40dB. In addition, the coupling performance in the low-frequency range is consistent with that of the empty package cavity. For reference, the transmission performance with an isolation improvement of not less than 10dB compared with the empty package cavity is defined as effective suppression. Therefore, a single-layer non-grounded anisotropic metasurface diaphragm achieves a suppression bandwidth of 5.5-5.89GHz (relative bandwidth of 6.84%). Since the suppression occurs in the frequency band dominated by the evanescent wave, it is called evanescent wave interference suppression.

[0029] Figure 8As shown in the figure, since a single-layer non-grounded anisotropic metasurface diaphragm can introduce a transmission zero, by designing a double-layer non-grounded anisotropic metasurface diaphragm, the phase shift of the TE surface wave along the diaphragm satisfies the mode mismatch condition at different frequency points, and two independent resonances can be introduced. When the two resonant frequencies are close, they can be overlapped to achieve broadband shielding performance. It can be observed that when two non-grounded anisotropic metasurface diaphragms are used separately, transmission zeros can be introduced at 5.4 GHz and 5.76 GHz, respectively. When they are combined into a second-order band-stop filter, their coupling effect causes the two resonant frequencies to expand, with a −10 dB suppression range of 5.18 to 5.88 GHz (relative bandwidth of 12.6%), and the suppression bandwidth is more than doubled compared to two separate non-grounded anisotropic metasurface diaphragms.

[0030] Fig. 9 As shown in the figure, when there is no non-grounded anisotropic metasurface diaphragm, the transmission coefficient between the two feeding ports decreases slowly with the decrease of frequency. In contrast, when the non-grounded anisotropic metasurface diaphragm is inserted, three transmission zeros appear in the designed frequency band (5-6GHz), which significantly improves the evanescent wave suppression effect. The curve with a 10dB reduction in the measured transmission coefficient without the non-grounded anisotropic metasurface diaphragm is used as an effective suppression reference. The measured -10dB suppression bandwidth is 5.08 to 6.1GHz, the relative bandwidth is 18.2%, and the measured curve is highly consistent with the simulated curve. Although the attenuation curve below -70dB is difficult to observe due to the limitation of the sensitivity of the network analyzer used for testing and the influence of background noise, the three transmission zeros generated by the third-order band-stop filter are clearly verified within the designed frequency band. In addition, the transmission coefficient curve outside the stopband is consistent with the curve without the non-grounded anisotropic metasurface diaphragm, verifying the effectiveness of the proposed design.

[0031] Therefore, the present invention adopts the above-mentioned non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, maintaining a relatively small size, being non-grounded and having a wide bandwidth, which makes it an innovative solution for suppressing radio frequency interference in electrically small cavity packages and dense integrated circuits.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity, characterized in that: It comprises a cavity, wherein a supersurface diaphragm and a mushroom-shaped structure are arranged inside the cavity, wherein the mushroom-shaped structure is located between two supersurface diaphragms, and coaxial feeding probes are symmetrically arranged outside the supersurface diaphragms, and the coaxial feeding probes penetrate the lower wall of the cavity.

2. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 1, characterized in that: A capacitive metasurface is provided on the metasurface diaphragm, the capacitive metasurface is composed of vertical grooves and transverse grooves, and a lumped capacitor and a lumped resistor are arranged on the capacitive metasurface, the lumped capacitor is placed in the vertical groove, and the lumped resistor is placed in the transverse groove.

3. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 1, characterized in that: The mushroom-shaped structure includes a metal patch and a first metal through hole. The metal patch is attached to the surface of the mushroom-shaped structure. The first metal through hole is arranged on the metal patch. The first metal through hole runs through the mushroom-shaped structure.

4. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 1, characterized in that: The super-surface diaphragm and the mushroom-shaped structure partially fill the cross-section of the cavity, the super-surface diaphragm and the mushroom-shaped structure are close to the upper wall of the wall, the distance between the super-surface diaphragm and the lower wall of the cavity is greater than 2 mm, and the distance between the mushroom-shaped structure and the lower wall of the cavity is greater than 7 mm.

5. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 1, characterized in that: The metasurface diaphragm comprises a high-frequency non-grounded anisotropic metasurface diaphragm and a low-frequency non-grounded anisotropic metasurface diaphragm, and the capacitance values ​​of the lumped capacitors on the high-frequency non-grounded anisotropic metasurface diaphragm and the low-frequency non-grounded anisotropic metasurface diaphragm are different.

6. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 1, characterized in that: The upper surface of the super-surface diaphragm is covered with copper, and the lower surface of the mushroom-shaped structure is covered with copper.

7. The non-grounded anisotropic metasurface diaphragm for suppressing evanescent waves in a compact cavity according to claim 5, characterized in that: The high-frequency non-grounded anisotropic metasurface diaphragm and the low-frequency non-grounded anisotropic metasurface diaphragm have the same spacing with the mushroom-shaped structure.

Images