Metamaterial resonator and waveguide band-pass filter including the same

Abstract

A metamaterial resonator according to one embodiment of the technical concept of the present disclosure comprises a first metamaterial resonant element extending in a vertical direction and a second metamaterial resonant element extending in a horizontal direction and intersecting the first metamaterial resonant element, and in terms of one cross-sectional area, the first metamaterial resonant element and the second metamaterial resonant element form a cross shape.

Description

Technology Field

[0001] The technical concept of the present disclosure relates to a metamaterial resonator and a waveguide bandpass filter including the same. Background Technology

[0003] Waveguide filters, particularly waveguide bandpass filters, are core components of wireless communication devices for satellites and aerospace communications. Recently, there has been a demand for reductions in the size and weight of waveguide bandpass filters due to the need for miniaturization and lightweighting in communication payloads, including microsatellites such as Low Earth Orbit (LEO) satellites, as well as geostationary and medium-orbit satellites and aircraft.

[0004] Accordingly, research is being conducted to realize lightweight waveguide filters by utilizing 3D printing technology and metal coating technology in order to find an alternative to the CNC (Computer Numerical Control) machining method, which has disadvantages in terms of weight and cost as a manufacturing method for general waveguide filters.

[0005] For example, a waveguide bandpass filter with a metastructure applied using 3D printing technology and metal coating technology can be cited. The waveguide bandpass filter has a structure in which a pin-type LRM (Locally Resonant Metamaterial, LRM) resonator with a resonant frequency (fr) is added to a waveguide having a cutoff frequency (fc), and resonance is utilized at a spacing between resonators shorter than half the wavelength of the electromagnetic wave.

[0006] The aforementioned waveguide bandpass filter has the advantage of being able to be designed with a reduced length compared to waveguide bandpass filters that do not apply a metastructure. However, there are limitations in implementing high performance, such as steep skirt characteristics (high Out-Of-Band (OOB) rejection performance). To improve OOB rejection performance, the width of the filter section must be reduced; however, this is because reducing the filter section width narrows the passband and imposes constraints on matching at the transition portion due to increased discontinuity characteristics in the input / output sections (flanges).

[0007] Therefore, measures to resolve such problems are required. The problem to be solved

[0009] The technical problem that the technical concept of the present disclosure aims to solve is to provide a metamaterial resonator capable of improving out-of-band rejection performance while maintaining bandpass performance, and a waveguide bandpass filter including the same.

[0010] The technical problems that the technical concept of the present disclosure aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0012] To achieve the above objectives, a metamaterial resonator according to one aspect of the technical concept of the present disclosure comprises: a first metamaterial resonant element extending in a vertical direction; and a second metamaterial resonant element extending in a horizontal direction and intersecting the first metamaterial resonant element; wherein, from the perspective of one cross-sectional area, the first metamaterial resonant element and the second metamaterial resonant element form a cross shape.

[0013] According to an exemplary embodiment, the length in the vertical direction of the first metamaterial resonant element may be different from the length in the horizontal direction of the second metamaterial resonant element.

[0014] According to an exemplary embodiment, the first metamaterial resonant element may include an overlapping segment that overlaps with the second metamaterial resonant element, and non-overlapping segments spaced apart from each other along the vertical direction with the overlapping segment in between, and the lengths in the vertical direction of at least two of the overlapping segment and the non-overlapping segments may be different from each other.

[0015] According to an exemplary embodiment, the second metamaterial resonant element may include an overlapping segment that overlaps with the first metamaterial resonant element, and non-overlapping segments spaced apart from each other along the horizontal direction with the overlapping segment in between, and the length of the overlapping segment in the horizontal direction may be different from the length of the non-overlapping segments in the horizontal direction, and the length of each of the non-overlapping segments in the horizontal direction may be the same.

[0016] According to an exemplary embodiment, the first cross-section perpendicular to the vertical direction of the first metamaterial resonant element and the second cross-section perpendicular to the horizontal direction of the second metamaterial resonant element may each have a square shape.

[0017] According to an exemplary embodiment, the area of ​​the first cross-section may be constant along the vertical direction, and the area of ​​the second cross-section may be constant along the horizontal direction.

[0018] According to an exemplary embodiment, the first metamaterial resonant element and the second metamaterial resonant element may be formed integrally.

[0019] According to an exemplary embodiment, the first metamaterial resonant element and the second metamaterial resonant element may include a base and a metal thin film covering the surface of the base.

[0020] A waveguide bandpass filter according to one embodiment of the technical concept of the present disclosure comprises: a waveguide extending in a first horizontal direction; and a plurality of metamaterial resonators arranged along the first horizontal direction within the internal space of the waveguide; wherein each of the plurality of metamaterial resonators comprises a first metamaterial resonant element extending in a vertical direction and a second metamaterial resonant element extending in a second horizontal direction perpendicular to the first horizontal direction and intersecting with the first metamaterial resonant element, and in terms of one cross-sectional area, the first metamaterial resonant element and the second metamaterial resonant element form a cross shape.

[0021] According to an exemplary embodiment, at least some of the plurality of metamaterial resonators may be arranged to be spaced apart at uneven intervals in the first horizontal direction.

[0022] According to an exemplary embodiment, the plurality of metamaterial resonators may be arranged such that the metamaterial resonators on one side and the metamaterial resonators on the other side are mirror-symmetric with respect to an imaginary line crossing the center of the waveguide.

[0023] According to an exemplary embodiment, the spacing between the metamaterial resonators on one side may gradually increase along the first direction, and the spacing between the metamaterial resonators on the other side may gradually decrease along the first direction.

[0024] According to an exemplary embodiment, the plurality of metamaterial resonators may be arranged in the internal space of the waveguide such that one end of the first metamaterial resonant element is spaced apart from one of the inner surfaces of the waveguide facing each other in the vertical direction, and both ends of the second metamaterial resonant element are spaced apart from the inner surfaces of the waveguide facing each other in the second horizontal direction.

[0025] According to an exemplary embodiment, the spacing between one end of the first metamaterial resonant element and one of the inner surfaces of the waveguide facing each other in the vertical direction may be greater than the spacing between both ends of the second metamaterial resonant element and the inner surfaces of the waveguide facing each other in the second horizontal direction.

[0026] According to an exemplary embodiment, the waveguide may include an input section, a filter section, and an output section, and the plurality of metamaterial resonators may be located in the filter section, and at least one of the input section and the output section may include a metamaterial port configured to couple an electromagnetic wave signal to the plurality of metamaterial resonators.

[0027] According to an exemplary embodiment, the metamaterial port may include first and second metamaterial port elements extending in the vertical direction and a third metamaterial port element extending in the second horizontal direction and intersecting the first and second metamaterial port elements, and in terms of one cross-sectional area, the first and second metamaterial port elements and the third metamaterial port element may form a double cross shape.

[0028] According to an exemplary embodiment, the waveguide and the plurality of metamaterial resonators can be formed integrally.

[0029] According to an exemplary embodiment, the waveguide and the plurality of metamaterial resonators may include a base and a metal thin film covering the surface of the base. Effects of the invention

[0031] According to embodiments based on the technical concept of the present disclosure, bandpass performance can be maintained by minimizing the narrowing of the passband of a waveguide bandpass filter through a cross-shaped metamaterial resonator, and out-of-band rejection performance can be improved by increasing the coupling between the cross-shaped metamaterial resonator and the waveguide.

[0032] In addition, by making the array spacing of cross-shaped metamaterial resonators at least partially non-uniform, matching characteristics can be maintained with a single metamaterial port.

[0033] Accordingly, this enables the miniaturization and weight reduction of the waveguide bandpass filter while also improving performance.

[0034] The effects obtainable by embodiments according to the technical concept of the present disclosure are not limited to the effects mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0036] A brief description of each drawing is provided to help to better understand the drawings cited in the present disclosure. FIG. 1 is a perspective view showing a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 2 is a plan view showing a waveguide bandpass filter according to one embodiment of the present disclosure. FIGS. 3 and 4 are drawings for illustrating a metamaterial resonator of a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 5 is a graph showing the dispersion of a metamaterial resonator according to one embodiment of the present disclosure. FIG. 6 is a graph showing the electric field storage energy density and impedance characteristics of a metamaterial resonator according to one embodiment of the present disclosure and a conventional metamaterial resonator. FIG. 7 is a graph showing the simulation results of the transmission coefficients of a metamaterial resonator according to one embodiment of the present disclosure and a conventional metamaterial resonator. FIGS. 8 and 9 are drawings for illustrating a metamaterial port of a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 10 is a graph showing the results of simulating the reflection coefficient and transmission coefficient of a waveguide bandpass filter according to one embodiment of the present disclosure. Specific details for implementing the invention

[0037] Exemplary embodiments according to the technical concept of the present disclosure are provided to more fully explain the technical concept of the present disclosure to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the technical concept of the present disclosure is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more faithful and complete and to fully convey the technical concept of the present invention to those skilled in the art.

[0038] In this disclosure, terms such as "first," "second," etc. are used to describe various members, regions, layers, parts, and / or components; however, it is obvious that these members, parts, regions, layers, parts, and / or components should not be limited by these terms. These terms do not imply a specific order, hierarchy, or superiority, and are used solely to distinguish one member, region, part, or component from another. Accordingly, the first member, region, part, or component described below may refer to the second member, region, part, or component without departing from the teachings of the technical concept of this disclosure. For example, without departing from the scope of rights of this disclosure, the first component may be named the second component, and similarly, the second component may be named the first component.

[0039] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the concept of this disclosure belongs. Furthermore, commonly used terms, such as those defined in advance, should be interpreted as having a meaning consistent with what they mean in the context of the relevant technology, and should not be interpreted in an overly formal sense unless explicitly defined herein.

[0040] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or in the reverse order of the description.

[0041] In the attached drawings, variations of the depicted shapes may be expected, for example, depending on manufacturing technology and / or tolerances. Accordingly, embodiments based on the technical concept of the present disclosure should not be interpreted as being limited to specific shapes of the areas depicted in the present disclosure, but should include, for example, changes in shape resulting from the manufacturing process. Identical reference numerals are used for identical components in the drawings, and redundant descriptions thereof are omitted.

[0042] The term 'and / or' as used herein includes each of the mentioned members and all combinations of one or more.

[0043] Hereinafter, embodiments according to the technical concept of the present disclosure will be described in detail with reference to the attached drawings.

[0045] FIG. 1 is a perspective view showing a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 2 is a plan view showing a waveguide bandpass filter according to one embodiment of the present disclosure.

[0046] Referring to FIGS. 1 and 2, a waveguide bandpass filter (10) according to one embodiment of the present disclosure may include a waveguide (110) and a plurality of metamaterial resonators (130). According to an embodiment, the waveguide bandpass filter (110) may further include metamaterial ports (150, 170). Hereinafter, an embodiment in which the waveguide bandpass filter (10) includes metamaterial ports (150, 170) will be described based on the following.

[0047] A waveguide (110) may include an input section (111) that guides an input electromagnetic wave, a filter section (113) that passes a specific frequency band of the electromagnetic wave, and an output section (115) that guides the passed specific frequency band.

[0048] The input section (111), filter section (113), and output section (115) may each be in the form of a column extending in the first horizontal direction (X) and having a cross-section (YZ plane) perpendicular to the first horizontal direction (X) that is square (e.g., rectangular). Accordingly, a cavity may be defined within each of the input section (111), filter section (113), and output section (115) by two faces facing each other in the vertical direction (Z) and two faces facing each other in the second horizontal direction (Y) which is orthogonal to the first horizontal direction (X). According to an embodiment, at least one of the input section (111), filter section (113), and output section (115) may be in the form of a column with a cross-section perpendicular to the first horizontal direction (X) that is not square, and accordingly, the shape of the cavity may also be defined differently.

[0049] The area of ​​the cross-section perpendicular to the first horizontal direction (X) of the input section (111), filter section (113), and output section (115) may each be constant along the first horizontal direction. According to an embodiment, the area of ​​the cross-section perpendicular to the first horizontal direction (X) of at least one of the input section (111), filter section (113), and output section (115) may vary along the first horizontal direction (X).

[0050] The length of the filter section (113) in the first horizontal direction (X) may be longer than the length of the input section (111) and the output section (115) in the first horizontal direction (X). The lengths of the input section (111) and the output section (115) in the second horizontal direction (Y) may be equal to each other but longer than the length of the filter section (113) in the second horizontal direction (Y). The lengths of the input section (111), the filter section (113), and the output section (115) in the vertical direction (Z) may be equal to each other. According to an embodiment, the length of the filter section (113) in the first horizontal direction (X) may be shorter than the length of the input section (111) and the output section (115) in the first horizontal direction (X). Additionally, the lengths of the input section (111) and the output section (115) in the second horizontal direction (Y) may be different from each other. Additionally, the vertical length (Z) of each of the input section (111) and output section (115) may be longer than the vertical length (Z) of the filter section (113).

[0051] In this way, the shape of the input section (111), filter section (113), and output section (115), the length in the horizontal / vertical direction, etc., can be varied in various ways depending on the passband characteristics of the waveguide bandpass filter (10) and the application field.

[0052] Meanwhile, although not illustrated, at least one of the input section (111), filter section (113), and output section (115) may further include a ridge structure for adjusting the cutoff frequency and cross-sectional area of ​​the waveguide (110) according to the characteristics and performance required of the waveguide bandpass filter (10). The ridge structure may be formed on at least one of the inner surfaces of the corresponding section and may be formed in at least one or more numbers. Additionally, the ridge structure may have various cross-sectional shapes such as a circle, rectangle, or triangle, and may be formed in various geometric shapes.

[0053] The input section (111), filter section (113), and output section (115) may each have a base having a metamaterial structure and a metal thin film layer coated on the surface of the base (not shown). According to an embodiment, the base may have a metamaterial structure only in a portion of its thickness or in a portion of its area, or the entire base may have a metamaterial structure. The base may include a polymer material as a material for the 3D printer. The metal thin film may include at least one metal material.

[0054] A plurality of metamaterial resonators (130) may be located in the filter section (113) of the waveguide (110). A metamaterial port (150) and a metamaterial port (170) may be located in the input section (111) and output section (115) of the waveguide (110), respectively.

[0055] Each of the multiple metamaterial resonators (130) may have a cross shape (or plus shape) in the cross section (YZ plane) perpendicular to the first horizontal direction (X) and may function as a unit resonator. The metamaterial ports (150, 170) may have a double cross shape in the cross section (YZ plane) perpendicular to the first horizontal direction (X) and may function as a matching port in the input section (111) and filter section (113), and in the filter section (113) and output section (115), respectively.

[0056] A plurality of metamaterial resonators (130) may be arranged such that they are positioned on the lower surface inside the filter section (113) but do not come into contact with the upper surface and both sides inside the filter section (113), and at least some of them are spaced apart from each other at an uneven interval along the first horizontal direction (X).

[0057] The metamaterial port (150) may be positioned on the lower surface inside the input section (111) but not in contact with the upper surface and both sides inside the input section (111), and may be positioned adjacent to the first metamaterial resonator of the filter section (113). The metamaterial port (170) may be positioned on the lower surface inside the output section (115) but not in contact with the upper surface and both sides inside the output section (115), and may be positioned adjacent to the last metamaterial resonator of the filter section (113).

[0058] Metamaterial ports (150), a plurality of metamaterial resonators (130), and metamaterial ports (170) arranged sequentially along a first horizontal direction (X) may be mirror-symmetric with respect to an imaginary line crossing the center of the waveguide (110) (e.g., the center of the filter section (113) or the center of the plurality of metamaterial resonators (130)). According to an embodiment, the spacing between the metamaterial ports and metamaterial resonators on one side with respect to the imaginary line may gradually increase, and the spacing between the metamaterial resonators and metamaterial ports on the other side with respect to the imaginary line may gradually decrease.

[0059] Referring further to FIG. 2, an example is given in which a plurality of metamaterial resonators (130) included in a waveguide bandpass filter (10) are composed of 11, and the waveguide bandpass filter (10) has a passband characteristic of 7.2 GHz to 7.8 GHz.

[0060] Based on a virtual line (CL) crossing the sixth metamaterial resonator in the center, the spacing (d1 to d6) between the metamaterial port (150) on the input section (111) side and the five metamaterial resonators may be inversely the same as the spacing (d7 to d12) between the five metamaterial resonators and the metamaterial port (170) on the output section (113) side.

[0061] Also, the intervals (d1 to d6) may gradually increase, and the intervals (d7 to d12) may gradually decrease. For example, the intervals (d1 to d6) may each be 3.65 mm, 6.4 mm, 7.6 mm, 8 mm, 8.2 mm, and 8.3 mm, and the intervals (d7 to d12) may each be 8.3 mm, 8.2 mm, 8 mm, 7.6 mm, 6.4 mm, and 3.65 mm.

[0062] A plurality of metamaterial resonators (130) and metamaterial ports (150, 170) may have a structure such as a waveguide (110), a base having a metamaterial structure, and a metal thin film layer coated on the surface of the base (not shown). According to an embodiment, the waveguide (110), the plurality of metamaterial resonators (130), and the metamaterial ports (150, 170) may be manufactured integrally by a 3D printer and thus may have the same structure. Similarly, the base may have a metamaterial structure only in a portion of its thickness or in a portion of its area, or the entire base may have a metamaterial structure. Additionally, the base may include a polymer material as the material for the 3D printer, and the metal thin film may include at least one metal material.

[0063] The functions, characteristics, detailed shapes, etc. of the plurality of metamaterial resonators (130) and metamaterial ports (150, 170) will be explained in detail with further reference to FIGS. 3 to 9.

[0064] FIGS. 3 and 4 are drawings for explaining a metamaterial resonator of a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 3 is an enlarged view of a portion in which one of the plurality of metamaterial resonators (130) is located in the waveguide bandpass filter (10) of FIG. 1, and a cross-section perpendicular to the first horizontal direction (X) of the metamaterial resonator (130) at any level. FIG. 4 is an enlarged view of the metamaterial resonator (130).

[0065] Referring to FIG. 3 (a) and (b), the metamaterial resonator (130) may include a first metamaterial resonant element (131) extending in the vertical direction (Z) and a second metamaterial resonant element (133) extending in the second horizontal direction (Y).

[0066] The first metamaterial resonant element (131) and the second metamaterial resonant element (133) can be intersected, for example, orthogonally and superimposed on each other, and can form a cross shape (or plus shape) in terms of a cross section (YZ plane) perpendicular to the first horizontal direction (X).

[0067] Due to the overlap, the first metamaterial resonant element (131) may include non-overlapping segments (131-1, 131-3) protruding in the vertical direction (Z) and an overlapping segment (131-2) between them. And, the second metamaterial resonant element (133) may include non-overlapping segments (133-1, 133-3) protruding in the second horizontal direction (Y) and an overlapping segment (133-2) between them. Here, the overlapping segments (131-2, 133-2) are substantially a single part, but are described separately for convenience of explanation.

[0068] The first metamaterial resonance element (131) is in the form of a column with a square cross-section (XY plane) perpendicular to the vertical direction (Z), and the area of ​​the cross-section may be constant along the vertical direction (Z). The second metamaterial resonance element (133) is also in the form of a column with a square cross-section (XZ plane) perpendicular to the second horizontal direction (Y), and the area of ​​the cross-section may be constant along the second horizontal direction (Y).

[0069] According to an embodiment, at least one of the cross-sectional shape of the first metamaterial resonant element (131) and the cross-sectional shape of the second metamaterial resonant element (133) may have a shape other than a square. In other words, at least one of the first metamaterial resonant element (131) and the second metamaterial resonant element (133) may be implemented in a column shape other than a square column shape.

[0070] According to an embodiment, at least one of the cross-sectional area of ​​the first metamaterial resonant element (131) and the cross-sectional area of ​​the second metamaterial resonant element (133) may differ in the extension direction.

[0071] For example, at least one of the first metamaterial resonant element (131) and the second metamaterial resonant element (133) may have a cross-sectional area of ​​non-overlapping segments larger than the cross-sectional area of ​​overlapping segments, or vice versa. Alternatively, at least one of the first metamaterial resonant element (131) and the second metamaterial resonant element (133) may have different cross-sectional areas of non-overlapping segments. Alternatively, at least one of the first metamaterial resonant element (131) and the second metamaterial resonant element (133) may have different cross-sectional areas of non-overlapping segments and overlapping segments. The above examples presuppose that the cross-sectional area of ​​each of the non-overlapping and overlapping segments is constant along the extension direction, but the technical concept of the present disclosure is not limited thereto. It goes without saying that the cross-sectional area may increase or decrease along the extension direction for each segment unit.

[0072] The cross-sectional area of ​​the first metamaterial resonant element (131) and the cross-sectional area of ​​the second metamaterial resonant element (133) may differ from each other, but are not limited thereto.

[0073] The first metamaterial resonant element (131) may have a total length (length in the vertical direction (Z)) such that one end (non-overlapping segment (131-1)) contacts the lower surface inside the filter section (113) and the other end (non-overlapping segment (131-3)) does not contact the upper surface inside the filter section (113) and is spaced apart. The second metamaterial resonant element (133) may have a total length (length in the second horizontal direction (Y)) such that both ends (non-overlapping segments (133-1, 133-3)) do not contact the two sides inside the filter section (113) and are spaced apart.

[0074] The total length of the first metamaterial resonant element (131) and the total length of the second metamaterial resonant element (133) may differ from each other. For example, the total length of the first metamaterial resonant element (131) may be shorter than the total length of the second metamaterial resonant element (133) (see FIG. 4). However, it is not limited thereto. The total lengths of the first and second metamaterial resonant elements (131, 133) may be determined by considering the spacing with respect to the inner surface of the filter section (113), in which case, depending on the shape of the cross-section (YZ plane) perpendicular to the first horizontal direction (X) of the filter section (113), the total lengths of the first and second metamaterial resonant elements (131, 133) may be the same, or the total length of the first metamaterial resonant element (131) may be longer than the total length of the second metamaterial resonant element (133).

[0075] According to an embodiment, at least two of the non-overlapping segments (131-1, 131-3) and the overlapping segment (131-2) of the first metamaterial resonant element (131) may have different lengths in the vertical direction (Z), which is the extension direction. This is not limited thereto, and some of the non-overlapping segments (131-1, 131-3) and the overlapping segment (131-2) may have the same length.

[0076] According to an embodiment, two of the non-overlapping segments (133-1, 133-3) and the overlapping segment (133-2) of the second metamaterial resonant element (133) may have different lengths in the second horizontal direction (Y), which is the extension direction. This is not limited thereto, and some of the non-overlapping segments (131-3, 133-3) and the overlapping segment (133-2) may have the same length.

[0077] In this way, the shape, length in the horizontal / vertical direction, etc. of the first metamaterial resonant element (131) and the second metamaterial resonant element (133) can be varied in various ways depending on the passband characteristics and application fields of the waveguide bandpass filter (10).

[0078] A detailed design example of a metamaterial resonator (130) in which a waveguide bandpass filter (10) has a passband characteristic of 7.2 to 7.8 GHz is described with further reference to FIG. 4.

[0079] Referring to FIG. 4, in the vertical direction (Z) which is the extension direction, the total length (L1) of the first metamaterial resonant element (131) may be 6 mm, the lengths (L11, L13) of the non-overlapping segments (131-1, 133-3) may be 3 mm and 2.1 mm, respectively, and the length (L12) of the overlapping segment (131-2) may be 0.9 mm.

[0080] In the second horizontal direction (Y) which is the extension direction, the total length (L2) of the second metamaterial resonant element (133) may be 8.4 mm, the lengths (L21, L23) of the non-overlapping segments (133-1, 133-3) may be 2.7 mm, and the length (L22) of the overlapping segment (133-2) may be 3 mm.

[0081] The length of the first and second metamaterial resonance elements (131, 13) in the first horizontal direction (X) may be 2.5 mm.

[0082] FIG. 5 is a graph showing the dispersion of a metamaterial resonator according to one embodiment of the present disclosure.

[0083] Figure 5 shows the results of a simulation performed in a state simulating a waveguide environment by setting the XZ plane and XY plane as PEC (Perfect Electric Conductor) and the YZ plane as an infinite array of PBC (Periodic Boundary Condition) conditions to extract the dispersion diagram of the metamaterial resonator (130) described with reference to Figure 4.

[0084] As shown in FIG. 5, it can be seen that the metamaterial resonator (130) exhibits the characteristic of propagating (passing through) the frequency band of approximately 7 to 8 GHz, more specifically 7.2 to 7.8 GHz of electromagnetic waves, while blocking other frequency bands.

[0085] FIG. 6 is a graph showing the electric field storage energy density and impedance characteristics of a metamaterial resonator according to one embodiment of the present disclosure and a conventional metamaterial resonator.

[0086] FIG. 6 shows the results of analyzing the electric field storage energy density and impedance characteristics using a pin-shaped metamaterial resonator as a comparative example with the metamaterial resonator (130) of FIG. 4.

[0087] Referring to FIG. 6(a) and (b), it can be seen that at a passband center frequency of 7.5 GHz, the electric field storage energy density (Fig. 6(a)) of a metamaterial resonator (130) having a cross shape according to one embodiment of the present disclosure is greater than the electric field storage energy density of a metamaterial resonator having a pin shape.

[0088] The increased electric field storage energy density of the metamaterial resonator (130) implies an increase in capacitance, which can be confirmed from the fact that the reactance value of the metamaterial resonator (130) at 7.0 to 7.2 GHz is reduced and the impedance value is steeper compared to the pin-shaped metamaterial resonator, as shown in FIG. 6 (c) and (d).

[0089] FIG. 7 is a graph showing the simulation results of the transmission coefficients of a metamaterial resonator according to one embodiment of the present disclosure and a conventional metamaterial resonator.

[0090] Figure 7 shows the simulation results of each transmission coefficient (S21) using a pin-shaped metamaterial resonator as a comparison example with the metamaterial resonator (130) of Figure 4.

[0091] Referring to FIG. 7, at 7 GHz, the fin-shaped metamaterial resonator showed a transmission coefficient (S21) of -27 dB, whereas the metamaterial resonator (130) showed a transmission coefficient (S21) of -59 dB, so it can be seen that the out-of-band rejection characteristics of the metamaterial resonator (130) are improved by more than 30 dB compared to the fin-shaped metamaterial resonator.

[0092] In this way, according to one embodiment of the present disclosure, a metamaterial resonator having a cross shape can improve out-of-band rejection performance by increasing the coupling between the waveguide and the metamaterial resonator while maintaining band-pass performance.

[0093] FIGS. 8 and 9 are drawings for illustrating a metamaterial port of a waveguide bandpass filter according to one embodiment of the present disclosure. FIG. 8 is an enlarged view of the portion where the metamaterial port (150) is located in the waveguide bandpass filter (10) of FIG. 1 and a cross-section perpendicular to the first horizontal direction (X) of the metamaterial port (150) at any level. FIG. 9 is an enlarged view of the metamaterial port (150). Since the metamaterial port (170) is substantially identical to the metamaterial port (150) shown in FIGS. 8 and 9, a detailed description is omitted here.

[0094] Referring to FIG. 8 (a) and (b), the metamaterial port (150) may include first and second metamaterial port elements (151, 153) extending in the vertical direction (Z) and a third metamaterial port element (155) extending in the second horizontal direction (Y).

[0095] The first and second metamaterial port elements (151, 153) and the third metamaterial port element (155) can overlap each other by intersecting, for example, orthogonally, and can form a double cross shape in terms of a cross section (YZ plane) perpendicular to the first horizontal direction (X).

[0096] Due to the overlap, the first metamaterial port element (151) may include non-overlapping segments (151-1, 151-3) protruding in the vertical direction (Z) and an overlapping segment (151-2) between them. The second metamaterial port element (153) may also include non-overlapping segments (153-1, 153-3) protruding in the vertical direction (Z) and an overlapping segment (153-2) between them. And, the third metamaterial resonance element (155) may include non-overlapping segments (155-1, 155-5) protruding in the second horizontal direction (Y), overlapping segments (155-2, 155-4), and a non-overlapping segment (155-3) between the overlapping segments (155-2, 155-4). Here, the overlapping segments (151-2, 155-2) are substantially one part, and the overlapping segments (153-2, 155-4) are also substantially one part, but they are described separately for convenience of explanation.

[0097] The first and second metamaterial pot elements (151, 153) are in the form of columns with a square cross-section (XY plane) perpendicular to the vertical direction (Z), and the area of ​​the cross-section may be constant along the vertical direction (Z). The third metamaterial pot element (153) is also in the form of columns with a square cross-section (XZ plane) perpendicular to the second horizontal direction (Y), and the area of ​​the cross-section may be constant along the second horizontal direction (Y).

[0098] According to an embodiment, at least one of the cross-sectional shapes of each of the first and second metamaterial port elements (151, 153) and the cross-sectional shape of the second metamaterial port element (155) may have a shape other than a square. At least one of the first to third metamaterial port elements (151, 153, 155) may be implemented in a column shape other than a square column shape.

[0099] According to an embodiment, at least one of the cross-sectional area of ​​the first metamaterial port element (151), the cross-sectional area of ​​the second metamaterial port element (153), and the cross-sectional area of ​​the third metamaterial port element (153) may differ in the extension direction.

[0100] For example, at least one of the first to third metamaterial port elements (151, 153, 155) may have a cross-sectional area of ​​non-overlapping segments larger than the cross-sectional area of ​​overlapping segments, or vice versa. Alternatively, at least one of the first to third metamaterial port elements (151, 153, 155) may have cross-sectional areas of non-overlapping segments different from each other. Alternatively, at least one of the first to third metamaterial port elements (151, 153, 155) may have cross-sectional areas of non-overlapping segments and overlapping segments different from each other. The above examples presuppose that the cross-sectional area of ​​each of the non-overlapping and overlapping segments is constant along the extension direction, but the technical concept of the present disclosure is not limited thereto. It goes without saying that the cross-sectional area may increase or decrease along the extension direction for each segment unit.

[0101] The cross-sectional areas of the first and second metamaterial port elements (151, 153) and the cross-sectional area of ​​the third metamaterial port element (155) may differ from each other, but are not limited thereto.

[0102] The first metamaterial port element (151) may have a total length (length in the vertical direction (Z)) such that one end (non-overlapping segment (151-1)) contacts the lower surface inside the input section (111) and the other end (non-overlapping segment (151-3)) does not contact the upper surface inside the input section (111) and is spaced apart.

[0103] The second metamaterial port element (153) may also have a total length (length in the vertical direction (Z)) such that one end (non-overlapping segment (153-1)) contacts the lower surface inside the input section (111) and the other end (non-overlapping segment (153-3)) does not contact the upper surface inside the input section (111) and is spaced apart.

[0104] The third metamaterial port element (155) may have a total length (length in the second horizontal direction (Y)) in which both ends (non-overlapping segments (155-1, 155-5)) are spaced apart without contacting both sides inside the input section (111).

[0105] According to the embodiment, the total length of the first and second metamaterial port elements (151, 153) and the total length of the third metamaterial port element (155) may differ from each other. For example, the total length of the first and second metamaterial port elements (151, 153) may be shorter than the total length of the third metamaterial port element (153) (see FIG. 9). However, it is not limited thereto. Additionally, the total lengths of the first and second metamaterial port elements (151, 153) may also differ from each other.

[0106] According to an embodiment, at least two of the non-overlapping segments (151-1, 151-3) and the overlapping segment (151-2) of the first metamaterial port element (151) may have different lengths in the vertical direction (Z), which is the extension direction. Alternatively, some of the non-overlapping segments (151-1, 151-3) and the overlapping segment (151-2) of the first metamaterial port element (151) may have the same length.

[0107] According to an embodiment, at least two of the non-overlapping segments (153-1, 153-3) and overlapping segment (153-2) of each of the second metamaterial port elements (153) may have different lengths in the vertical direction (Z), which is the extension direction. Alternatively, some of the non-overlapping segments (153-1, 153-3) and overlapping segment (153-2) of the second metamaterial port elements (153) may have the same length.

[0108] According to an embodiment, at least two of the non-overlapping segments (155-1, 155-3, 155-5) and overlapping segments (155-2, 155-4) of the third metamaterial port element (155) may have different lengths in the second horizontal direction (Y), which is the extension direction. This is not limited thereto, and some of the non-overlapping segments (155-1, 155-3, 155-5) and overlapping segments (155-2, 155-4) of the third metamaterial port element (155) may have the same length.

[0109] In this way, the shape, length in the horizontal / vertical direction, etc. of the first to third metamaterial port elements (151, 153, 155) can be varied in various ways depending on the matching characteristics, passband characteristics, and application fields in the waveguide bandpass filter (10).

[0110] A detailed design example of metamaterial ports (150) when the waveguide bandpass filter (10) has a passband characteristic of 7.2 to 7.8 GHz is described with further reference to FIG. 9.

[0111] Referring to FIG. 9, the total length (L4) of the first and second metamaterial port elements (151, 153) in the vertical direction (Z), which is the extension direction, may be 5.81 mm, the lengths (L41, L43) of the non-overlapping segments (151-1 / 153-1, 151-3 / 153-3) may be 0.9 mm and 0.52 mm, respectively, and the length (L42) of the overlapping segments (151-2, 153-2) may be 4.5 mm.

[0112] In the second horizontal direction (Y) which is the extension direction, the total length (L5) of the third metamaterial port element (155) may be 17.3 mm, the lengths (L51, L53, L55) of the non-overlapping segments (155-1, 155-3, 155-5) may be 3.75 mm, 6.2 mm, and 3.75 mm, respectively, and the lengths (L52, L54) of the overlapping segments (155-2, 155-4) may be 1.8 mm.

[0113] The length (L6) of the first to third metamaterial port elements (151, 153, 155) in the first horizontal direction (X) may be 2.18 mm.

[0114] FIG. 10 is a graph showing the results of simulating the reflection coefficient and transmission coefficient of a waveguide bandpass filter according to one embodiment of the present disclosure.

[0115] FIG. 10 shows the results of simulating the reflection coefficient (S11) and transmission coefficient (S21) of a waveguide bandpass filter (10) designed to have a frequency bandpass characteristic of 7.2 to 7.8 GHz, as described with reference to FIG. 1, FIG. 2, FIG. 4 and FIG. 9.

[0116] Referring to FIG. 10, it can be seen that the waveguide bandpass filter (10) satisfies a reflection coefficient (S11) of less than -10 dB at the target range of 7.2 to 7.8 GHz and exhibits a non-pass band transmission coefficient (S21) of less than -50 dB.

[0117] A waveguide bandpass filter according to one embodiment of the present disclosure can have improved out-of-band rejection performance by using a metamaterial resonator having a cross shape, and can be matched to single metamaterial ports by arranging the metamaterial resonators at non-uniform intervals, thereby enabling high performance when manufacturing a metamaterial-based waveguide bandpass filter by 3D printing technology.

[0119] Meanwhile, although not illustrated, the waveguide bandpass filter (10) according to the embodiments of the present disclosure can be manufactured using 3D printing and metal coating technology.

[0120] For example, the core shape of a waveguide bandpass filter (10) can be formed through 3D printing. The core shape includes the base shape of a waveguide, a metamaterial resonator, and a metamaterial port, and at least a portion may have a metamaterial structure. The core shape can be formed from 3D printer materials such as polyetherketoneketone (PEKK) series polymer materials and polycarbonates (PC).

[0121] Subsequently, a metal thin film can be formed on the core shape surface by performing a dry (e.g., PVD) metal coating and / or a wet metal coating (e.g., electroplating).

[0122] Through this, the waveguide (110), metamaterial resonator (130), and metamaterial ports (150, 170) can be formed integrally, and the waveguide (110), metamaterial resonator (130), and metamaterial ports (150) can be implemented in a structure in which a metal thin film layer is stacked on a core base.

[0124] The description of the above-described embodiments is merely an example provided with reference to the drawings for a more thorough understanding of the present disclosure, and should not be interpreted as limiting the technical scope of the present disclosure.

[0125] Furthermore, it will be apparent to those skilled in the art to which this disclosure pertains that various changes and modifications are possible within the scope of the basic principles of this disclosure. Explanation of the symbols

[0127] 10: Waveguide bandpass filter 110: Waveguide 130: Metamaterial Resonator 150, 170: Metamaterial Port

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