A half-mode substrate integrated waveguide filter loaded with open-circuited stubs

Abstract

This invention belongs to the field of communication technology, specifically a half-mode substrate integrated waveguide filter with an open-circuit stub, comprising: a dielectric substrate, including an upper metal layer, a dielectric layer, and a lower metal layer sequentially disposed; a first via enclosure, including a plurality of first metallized vias penetrating the dielectric substrate and electrically connecting the upper metal layer and the lower metal layer, the plurality of first metallized vias being arranged at intervals to form a lateral equivalent electric wall, the lateral equivalent electric wall, the side of the dielectric substrate opposite to the first via enclosure, the upper metal layer, and the lower metal layer jointly defining a half-mode substrate integrated waveguide cavity; and at least one open-circuit stub disposed in the half-mode substrate integrated waveguide cavity and electromagnetically coupled to the half-mode substrate integrated waveguide cavity at a predetermined position, wherein the end of the open-circuit stub away from the coupling position remains open.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a half-mode substrate integrated waveguide filter with loaded open stubs. Background Technology

[0002] Phased array radar and satellite communication systems place higher demands on the frequency selection and spurious suppression of the radio frequency front end. As a key passive device, the insertion loss, selectivity, stopband suppression and structural integrability of filters directly affect the performance of the transmit and receive links.

[0003] While traditional microstrip line filters are easy to integrate with planar circuits, their open transmission structure results in relatively low quality factors, high losses, and limited power capacity. In high-frequency applications such as Ku band filters, it is often difficult to simultaneously achieve low loss and high selectivity. Metal rectangular waveguide filters offer advantages in both quality factor and high power capacity, but they are large, heavy, and have high manufacturing and assembly costs. Furthermore, they are not easily integrated into planar circuits and array T / R components at high density. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a half-mode substrate integrated waveguide filter with loaded open-circuit stubs.

[0005] This invention provides a half-mode substrate integrated waveguide filter with loaded open-circuit stubs, comprising: A dielectric substrate includes an upper metal layer, a dielectric layer, and a lower metal layer disposed sequentially. A first via enclosure, a plurality of first metallized vias penetrating the dielectric substrate and electrically connecting the upper metal layer and the lower metal layer, the plurality of first metallized vias being arranged at intervals to form a lateral equivalent electric wall, the lateral equivalent electric wall, the side of the dielectric substrate opposite to the first via enclosure, the upper metal layer and the lower metal layer together defining the half-mode substrate integrated waveguide cavity; At least one open-circuit stub is disposed in the half-mode substrate integrated waveguide cavity and electromagnetically coupled to the half-mode substrate integrated waveguide cavity at a predetermined position, and the end of the open-circuit stub away from the coupling position remains open.

[0006] In one embodiment, the half-mode substrate integrated waveguide filter with loaded open-circuit stubs further includes a second via fence, the second via fence including a plurality of second metallized vias, the plurality of second metallized vias penetrating the dielectric substrate and electrically connecting the upper metal layer and the lower metal layer; the second via fence is located in the half-mode substrate integrated waveguide cavity, covers a portion of the length along the propagation direction, and is spaced apart from the dielectric substrate side away from the first via fence.

[0007] In one embodiment, the cross-sections of the first metallized via and the second metallized via are both regular hexagonal, making the first metallized via and the second metallized via form regular hexagonal prisms.

[0008] In one embodiment, the coupling between the open-circuit stub and the half-mode substrate integrated waveguide cavity is achieved by at least one of the following methods: The open-circuit stub is electrically connected to the conductor pattern of the upper metal layer at the coupling position; The open-circuit stub and the conductor pattern of the upper metal layer are separated at the coupling position to form a gap coupling; At least a portion of the open-circuit spur is arranged parallel to and opposite the input excitation slot and / or the output excitation slot within a predetermined spacing range.

[0009] In one embodiment, the open-circuit stub includes at least two open-circuit stubs, which are located at different positions along the propagation direction and / or at different lateral positions along the width direction, near the virtual magnetic wall side and near the lateral equivalent electric wall side.

[0010] In one embodiment, the electrical length of the open stub is one-quarter of the waveguide wavelength or an odd multiple thereof in the transmission mode of the open stub, so that it exhibits low impedance resonance characteristics at the input end at the corresponding frequency, thereby forming a transmission zero on the main transmission path of the half-mode substrate integrated waveguide cavity.

[0011] In one embodiment, the shape of the open-circuit stub is any one or a combination of a straight shape, a folded shape, a stepped impedance shape, or a shape with end loading, wherein: The stepped impedance open-circuit stub is composed of at least two transmission line segments with different characteristic impedances connected in series; and / or The open-circuit stub with end loading has a capacitor-loaded conductor pattern at its open end.

[0012] In one embodiment, the upper surface metal layer is further provided with one or more auxiliary slots, which are located within the upper projection range of the half-mode substrate integrated waveguide cavity.

[0013] In one embodiment, the distance between two adjacent first metallized vias in the first metallized via array is no greater than twice the equivalent diameter of the first metallized via, and the equivalent diameter of the first metallized via is less than one-tenth of the wavelength of the corresponding center frequency guided wave.

[0014] In one embodiment, the half-mode substrate integrated waveguide filter with loaded open-circuit stubs further includes: The input excitation slot (3) and the output excitation slot (4) are disposed on the upper metal layer (11) to couple the signal into the half-mode substrate integrated waveguide cavity and output it.

[0015] The advantages of this invention compared to the prior art are as follows: By loading at least one open stub inside the half-mode substrate integrated waveguide cavity and electromagnetically coupling it to the cavity at a predetermined position, an additional adjustable resonant branch can be introduced while maintaining the half-mode miniaturization advantage of the half-mode substrate integrated waveguide, achieving stronger response shaping without increasing the number of cavity stages.

[0016] Open-circuit stubs, under specific electrical length conditions, generate a resonant effect, causing energy cancellation or strong coupling suppression at the corresponding frequency point in the main transmission path, thus creating a transmission null. Placing this null near the passband edge can achieve a steeper roll-off characteristic, improving adjacent channel rejection and anti-interference capabilities.

[0017] By adjusting the coupling position of the open stub to the cavity and the parameters of the open stub, the transmission zero point can be set outside the passband, thereby increasing the stopband depth, expanding the stopband range, improving the purity of the transmit link spectrum, and reducing the risk of interference to subsequent devices.

[0018] The overall structure is based on a planar implementation of "upper metal layer - dielectric layer - lower metal layer - via enclosure - open branch". It can be completed using conventional PCB or microwave substrate metallization via and pattern etching processes. While reducing manufacturing complexity, it is easy to integrate with phased array T / R components at high density and has excellent performance consistency in mass production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 According to an embodiment of the present invention, a three-dimensional structural schematic diagram of a half-mode substrate integrated waveguide filter with loaded open-circuit stubs is shown.

[0021] Figure 2 According to an embodiment of the present invention, a schematic diagram of the frequency response curve of a half-mode substrate integrated waveguide filter with loaded open stubs is shown.

[0022] In the figure: 1. Dielectric substrate; 11. Upper metal layer; 12. Dielectric layer; 13. Lower metal layer; 2. First via enclosure; 21. First metallized via; 3. Input excitation slot; 4. Output excitation slot; 5. Open circuit stub; 6. Auxiliary slot; 7. Second via enclosure; 71. Second metallized via. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present invention can be modified or changed according to different viewpoints and application systems without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0024] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can readily implement it. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0025] In the representation of this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics represented in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. Furthermore, the specific features, structures, materials, or characteristics represented may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate different embodiments or examples represented in this invention, as well as features of different embodiments or examples, without contradiction.

[0026] Furthermore, the terms "first" and "second" are used for illustrative purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the representation of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] To clearly illustrate the present invention, components unrelated to the description are omitted, and the same or similar constituent elements throughout the specification are given the same reference numerals.

[0028] Throughout this specification, when it is said that a device is "connected" to another device, this includes not only "direct connection" but also "indirect connection" by placing other components in between. Furthermore, when it is said that a device "comprises" a certain constituent element, unless otherwise stated otherwise, this does not exclude other constituent elements, but rather implies that other constituent elements may be included.

[0029] When we say that a device is "above" another device, this can mean that it is directly above the other device, or it can mean that other devices are present in between. Conversely, when we say that a device is "directly" "above" another device, there are no other devices present in between.

[0030] While the terms first, second, etc., are used herein to denote various elements in some embodiments, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, first interface and second interface, etc., are used. Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of features, steps, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are to be interpreted inclusively, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition occur only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some manner.

[0031] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the invention. The singular form used herein includes the plural form unless the statement explicitly indicates otherwise. The word "comprising" as used in this specification means to specify a particular characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0032] Although not explicitly defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries shall be further interpreted as having a meaning consistent with relevant technical literature and the content of this present instruction, and shall not be over-interpreted as having an ideal or overly formulaic meaning unless otherwise defined.

[0033] like Figure 1 As shown, this application provides a half-mode substrate integrated waveguide filter with an open-circuit stub 5, comprising: a dielectric substrate 1, including an upper metal layer 11, a dielectric layer 12, and a lower metal layer 13 sequentially disposed along the thickness direction; and a first via enclosure 2, comprising a plurality of first metallized vias 21 penetrating along the thickness direction of the dielectric substrate 1 and electrically connecting the upper metal layer 11 and the lower metal layer 13, wherein the plurality of vias are arranged at intervals and extend to form the first via enclosure 2, thereby constituting the lateral equivalent electrical wall of the half-mode substrate integrated waveguide cavity. A half-mode substrate integrated waveguide cavity is defined by a lateral equivalent electric wall, a side on the dielectric substrate 1 opposite to the via enclosure, an upper metal layer 11, and a lower metal layer 13. An input excitation slot 3 and an output excitation slot 4 are disposed on the upper metal layer 11 to couple signals into and out of the half-mode substrate integrated waveguide cavity. At least one open-circuit stub 5 is disposed in the half-mode substrate integrated waveguide cavity and electromagnetically coupled to the half-mode substrate integrated waveguide cavity at a predetermined position, with the end of the open-circuit stub 5 away from the coupling position remaining open.

[0034] It is understood that the filter described in this application is a planar waveguide filter that achieves passband transmission and controllable suppression of out-of-band or bandside signals by means of "through-hole enclosure forming a lateral equivalent electric wall + slot to complete input-output coupling + cavity open-circuit stub 5 to introduce additional resonant branches" on the basis of a half-mode substrate integrated waveguide cavity. The upper metal layer 11 and the lower metal layer 13 of the dielectric substrate 1 constitute the upper and lower conductor boundaries. The first through-hole enclosure 2 is formed by the extension of multiple metallized through-hole arrays, which is equivalent to the cavity sidewall electric wall. Together with the substrate side opposite the through-hole enclosure and the upper and lower metal layers 13, it defines the half-mode SIW cavity, giving it field confinement and energy storage capabilities similar to a waveguide resonant cavity. The input excitation slot 3 and the output excitation slot 4 are opened on the upper metal layer 11, which serve as electromagnetic coupling ports to couple external transmission line energy into the cavity and then couple it out, thereby forming the basic passband response of the filter.

[0035] In practical applications, the filter introduces an open-circuit stub 5, electromagnetically coupled to the cavity, as an additional tunable resonant branch within the half-mode substrate integrated waveguide cavity. Under specific electrical length conditions, the open-circuit stub 5 resonates and forms an energy shunting and suppression effect on the main transmission path. This generates a controllable transmission zero without increasing the cavity stage number or sacrificing the advantages of miniaturization and planar integration of the half-mode structure. This transmission zero can be placed at the edge of the passband to significantly improve the roll-off steepness and adjacent channel suppression capability, or it can be placed outside the passband or in the spurious harmonic frequency band to deepen the stopband attenuation and extend the stopband range, thereby improving the system spectral purity and reducing the risk of interference to subsequent devices. At the same time, its zero position and suppression depth can be engineered and adjusted through stub parameters and coupling positions. Furthermore, the overall structure can be achieved using conventional PCB / microwave substrate through-hole metallization and pattern etching processes, which is beneficial for high-density integration and batch consistency.

[0036] like Figure 1 As shown, in one example provided in this application, the half-mode substrate integrated waveguide filter with the loaded open stub 5 further includes a second via fence 7. The second via fence 7 includes a plurality of second metallized vias 71, which penetrate the dielectric substrate 1 and electrically connect the upper metal layer 11 and the lower metal layer 13. The second via fence 7 is located in the half-mode substrate integrated waveguide cavity, covers a portion of the length along the propagation direction, and is spaced apart from the side of the dielectric substrate 1 away from the first via fence 2.

[0037] Understandably, the second via enclosure 7, located inside the half-mode substrate integrated waveguide cavity and covering only a portion of its length along the propagation direction, does not replace the first via enclosure 2 to form a lateral equivalent electric wall. Instead, it serves as a local electric wall or disturbance structure within the cavity, introducing additional boundary constraints to alter the electromagnetic field distribution and energy propagation path within the cavity. Since the second via enclosure 7 is spaced apart from the side of the dielectric substrate 1 furthest from the first via enclosure 2, this spaced area maintains the open-boundary equivalent conditions required for the half-mode structure. This allows for precise adjustment of the equivalent cavity width, coupling strength, and resonance characteristics without disrupting the half-mode operating mechanism.

[0038] In practical applications, the coverage length of the second via enclosure 7, its spacing from the side of the dielectric substrate 1, and the via diameter and spacing can serve as key design parameters for engineering modifications to the filter's center frequency, bandwidth, and stopband suppression during the commissioning phase. For example, when it is necessary to enhance the field confinement of a certain frequency band to reduce radiation leakage or improve insertion loss, the coverage length of the second via enclosure 7 can be appropriately increased or its position adjusted to enhance the local electric wall effect. When it is necessary to optimize the energy transfer between the input excitation slot 3 and the output excitation slot 4, improve passband flatness, or improve passband edge roll-off, the field distribution and equivalent coupling conditions near the open boundary can be adjusted by changing the spacing between the second via enclosure 7 and the open boundary side. Meanwhile, the second via enclosure 7 adopts a metallized via form that penetrates the substrate and electrically connects the upper metal layer 11 and the lower metal layer 13. Its process is consistent with that of the first via enclosure 2, which facilitates mass production and consistency control without significantly increasing processing difficulty, making it more suitable for high-density integrated applications such as phased array T / R components.

[0039] like Figure 1As shown, in one example provided in this application, the cross-sections of both the first metallized via 21 and the second metallized via 71 are regular hexagons, making the first metallized via 21 and the second metallized via 71 regular hexagonal prisms. Specifically, the center distance between two adjacent first metallized vias 21 in the array of first metallized vias 21 is no greater than twice the equivalent diameter of the first metallized via 21, and the equivalent diameter of the first metallized via 21 is less than one-tenth of the waveguide wavelength at the corresponding center frequency.

[0040] It should be noted that, in this embodiment, the equivalent diameter is the diameter of the inscribed circle corresponding to the cross-section of the regular hexagon (optionally, the diameter of the circumscribed circle can also be used as the equivalent diameter, and the following constraints also apply). In other embodiments, when the cross-section of the first metallized through-hole 21 and / or the second metallized through-hole 71 is circular, the equivalent diameter is the diameter of the circle; when the cross-section is a regular polygon, the equivalent diameter is either the diameter of the inscribed circle or the diameter of the circumscribed circle corresponding to the regular polygon.

[0041] It is understood that the above-mentioned dimensional relationship is used to make the array of first metallized vias 21 electromagnetically approximately form a continuous metal sidewall, thereby reducing the possibility of electromagnetic field leakage and radiation from the via gaps and suppressing parasitic modes and additional losses introduced by sparse vias or excessively large via diameters; wherein, the waveguide wavelength is the waveguide propagation wavelength at the center frequency in the half-mode substrate integrated waveguide structure.

[0042] In actual use, after determining the center frequency and dielectric parameters, the waveguide wavelength at the center frequency is first calculated or simulated. Then, the via geometry is selected and the equivalent diameter is determined in combination with the process capability. Subsequently, the via array is arranged according to the constraint that "the via center distance is not greater than twice the equivalent diameter". Electromagnetic simulation is used to verify whether the insertion loss, return loss and stopband suppression meet the indicators. If lateral leakage or stopband degradation occurs, it can be adjusted by reducing the via center distance, increasing the via equivalent diameter (provided that it is less than one-tenth of the waveguide wavelength), or increasing the number of vias.

[0043] The calculation formula based on the relevant parameters of the first metallized through-hole 21 is as follows: Let the center distance between adjacent first metallized vias 21 be... The equivalent diameter of the first metallized via 21 is The center frequency is ,but:

[0044]

[0045] in For half-mode substrate integrated waveguide structures at the center frequency The guided wave wavelength below.

[0046] The equivalent diameter is calculated as follows: When the cross-section of the first metallized through-hole 21 is a regular hexagon, let the side length of the regular hexagon be... ; If the equivalent diameter is taken as the diameter of the inscribed circle :

[0047] If the equivalent diameter is taken as the diameter of the circumcircle :

[0048] When the cross-section of the first metallized through-hole 21 is circular, let the radius of the circle be... ,but:

[0049] If the cross-section of the first metallized through-hole 21 is a regular polygon, let the side length of the regular polygon be... Then its inscribed circle radius and circumscribed circle radius are respectively:

[0050]

[0051] therefore, , equivalent diameter Desirable or Any one of them.

[0052] Calculation of guided wave wavelength; waveguide wavelength With position constant The relationship is:

[0053] It can be directly extracted through full-wave electromagnetic simulation. Optionally, the equivalent rectangular waveguide TE_{10}$ principal mode approximation is used, written as:

[0054]

[0055] in The relative permittivity of the medium, The speed of light in a vacuum. This is the cutoff frequency.

[0056] The cutoff frequency can be determined by the equivalent rectangular waveguide width dimension. Represented as:

[0057] This also leads to the commonly used expression for guided wave wavelength:

[0058]

[0059] Will Substitute and you will get , used for the dimensional constraints above.

[0060] The calculation of the relevant parameters of the second metallized through-hole 71 is the same as that of the first metallized through-hole 21, and will not be repeated here.

[0061] like Figure 1 As shown, in one optional embodiment provided by this application, the open-circuit stub 5 is electrically connected to the conductor pattern of the upper metal layer 11 at a coupling position. Specifically, the open-circuit stub 5 is disposed on the upper metal layer 11 and directly connected to the conductor pattern of the upper metal layer 11 within the cavity at a predetermined coupling position, forming a conductive connection. It should be noted that this application does not limit the specific location of the open-circuit stub 5; the conductor pattern of the upper metal layer 11 connected to it can be a local metal island, a loading segment, or a metal trace area connected to the excitation structure within the cavity. The other end of the open-circuit stub 5 remains open to maintain its open-circuit resonant characteristics.

[0062] Understandably, the electrical connection is a direct-feed type, with open-circuit stub 5 acting as an additional resonant branch of the cavity. Its input impedance varies with frequency and exhibits strong resonance under specific electrical length conditions. This resonant branch will significantly disturb the main mode field distribution of the cavity, causing energy shunting or equivalent impedance abrupt changes at the target frequency, resulting in deep slumps or destructive effects on the main transmission path, thereby creating transmission zeros or enhancing stopband suppression.

[0063] In one optional embodiment provided in this application, a gap is provided between the open-circuit stub 5 and the conductor pattern of the upper metal layer 11 at the coupling position to form a slot coupling; specifically, the open-circuit stub 5 and the conductor pattern of the upper metal layer 11 in the cavity are not directly connected at the coupling position, but maintain a predetermined gap, and the two form a slot structure relative to each other. The gap can be a straight slot, a narrow slot, or a partially open shape, which can be achieved by planar etching. The open-circuit stub 5 still maintains an open circuit at one end.

[0064] Understandably, slot coupling is a type of capacitive coupling, and the coupling strength is determined by the slot capacitance. At resonance, the open-circuit stub 5 exchanges energy with the cavity through capacitive coupling, causing an additional phase rotation in the cavity response at a specific frequency to cancel out the energy, thus creating a transmission zero. Slot coupling allows for controllable coupling without introducing DC conduction, facilitating precise adjustment of the zero position and passband effects.

[0065] Key parameters include slot width, relative overlap length, coupling location, and open stub size. Generally, smaller slots and longer overlaps result in stronger coupling, deeper zero points, and closer proximity to the passband. This approach offers more controllable side effects on the passband and is suitable for designs that require a steep roll-off at the passband edge while balancing insertion loss and passband flatness.

[0066] In one optional embodiment provided in this application, at least a portion of the open-circuit stub 5 is arranged parallel to and opposite the input excitation slot 3 and / or the output excitation slot 4 within a predetermined spacing range. Specifically, the open-circuit stub 5 is arranged near the input excitation slot 3 and / or the output excitation slot 4, such that at least a segment of the open-circuit stub 5 is parallel to the slot direction and is placed relative to it at a predetermined spacing. This relative segment can be located on one or both sides of the slot, or it can be close to the input end or the output end, forming a local near-field coupling region.

[0067] In this embodiment, the open-circuit stub 5 not only couples with the cavity but also generates an additional coupling path with the near field of the excitation slot, forming a controllable bypass coupling or cross-coupling effect. When the open-circuit stub 5 resonates, it will produce frequency-selective suppression or cancellation on the injection and extraction process of excitation energy, causing the transfer function to have a zero. By selectively coupling with the input slot or the output slot, the zero can be more specifically arranged at the low end or high end of the passband, or used to suppress specific spurious and harmonic responses.

[0068] The spacing, parallel relative length, relative position, and electrical length of open-circuit stub 5 and slot are considered. Smaller spacing and longer parallel segments result in stronger coupling and a more pronounced zero point. This method effectively introduces transmission zeros without significantly altering the cavity's main dimensions, offering advantages for achieving asymmetric roll-off, improving adjacent channel suppression, or extending stopband width. Furthermore, it offers high layout freedom, facilitating co-optimization with existing input / output excitation structures.

[0069] like Figure 1As shown, in one optional embodiment provided by this application, the open-circuit stub 5 includes at least two open-circuit stubs 5, which are respectively located at different positions along the propagation direction of the half-mode substrate integrated waveguide cavity and / or at different lateral positions along the width direction, near the virtual magnetic wall side and near the lateral equivalent electric wall side. In this embodiment, there are two open-circuit stubs 5, which are respectively arranged at intervals along the propagation direction in the half-mode substrate integrated waveguide cavity. One end of each of the two open-circuit stubs 5 is electrically connected to the conductor pattern of the upper metal layer 11, and the other end maintains an open-circuit structure. In this embodiment, two open-circuit stubs 5 are spaced apart along the propagation direction of the half-mode substrate integrated waveguide cavity, so that the two open-circuit stubs 5 form differentiated coupling to the cavity main mode at different phases and different field strengths. When each open-circuit stub 5 exhibits low impedance resonance under its corresponding electrical length condition, it will generate more significant and controllable energy shunting and equivalent impedance mutation on the main transmission path, which is conducive to forming one or more transmission zeros in the target frequency band and coordinating the frequency position and suppression depth of the transmission zeros, thereby improving the stopband suppression degree and improving the out-of-band selectivity, and making the band edge roll-off steeper.

[0070] Furthermore, the spacing of the two open-circuit stubs 5 can improve the freedom of response shaping, expanding the stopband suppression from a single resonant disturbance to the superposition effect of multiple positional disturbances. This enhances the suppression depth or expands the effective stopband range while reducing the risk of increased passband insertion loss and deteriorated passband ripple that may be introduced by strong coupling of a single stub, achieving a better trade-off between passband performance and stopband suppression performance. At the same time, this structure has a certain role in sharing and mitigating the resonant frequency deviation of a single stub caused by processing and assembly errors, which is beneficial to improving the consistency and stability of the device's electrical performance.

[0071] It is understood that in this application, at least two open-circuit stubs 5 are respectively set at different positions along the propagation direction and / or at different lateral positions along the width direction, near the virtual magnetic wall side and near the lateral equivalent electric wall side. This allows each open-circuit stub 5 to form differentiated coupling with the main transmission path of the cavity under different electromagnetic field strengths and phase conditions, thereby improving the design freedom and robustness of the filter response. Specifically, by introducing parallel resonant branches at different positions, one or more transmission zeros can be generated in the target frequency band, and the frequency position and suppression depth of the transmission zeros can be synergistically controlled to obtain higher stopband suppression capability and steeper band-edge roll-off characteristics. At the same time, by utilizing the difference in field distribution caused by the boundary conditions at the virtual magnetic wall side and the lateral equivalent electric wall side, the coupling strength of the stubs can be adjusted. While enhancing stopband suppression or expanding the effective stopband range, the adverse effects on passband insertion loss and passband ripple are reduced, thereby achieving a better trade-off between passband performance and stopband suppression.

[0072] In one optional embodiment provided in this application, the electrical length of the open stub 5 is one-quarter of the waveguide wavelength or an odd multiple thereof in the transmission mode of the open stub 5, so that it exhibits low impedance resonance characteristics at the input end at the corresponding frequency, thereby forming a transmission zero on the main transmission path of the half-mode substrate integrated waveguide cavity.

[0073] Understandably, under the aforementioned electrical length conditions, the open-circuit stub 5 is equivalent to a low-impedance resonant branch connected in parallel to the main transmission path. At the corresponding resonant frequency, it strongly shunts the energy on the main transmission path and causes a sudden change in equivalent impedance, resulting in significant attenuation and the formation of a transmission zero at that frequency. This effectively improves stopband suppression, enhances out-of-band selectivity, and makes the band roll-off steeper. Furthermore, by designing the electrical length of the open-circuit stub 5 to be different odd multiples of a quarter-waveguide wavelength, the frequency position of the transmission zero can be flexibly set without significantly increasing the structural size. This satisfies response shaping requirements for different frequency bands or different suppression needs, and reduces the adverse effects on passband insertion loss and passband ripple, achieving a better trade-off between passband performance and stopband suppression. The electrical length satisfies: Equivalent to physical length: .in, The phase constant (the phase part of the propagation constant) is expressed in units of 1000 ppm. ; It is a constant, taking the value of a non-negative integer of 0, 1, 2, 3...; Wavelength of the guided wave, unit .

[0074] like Figure 1 As shown, in one optional embodiment provided by this application, the shape of the open-circuit stub 5 is any one or a combination of a straight line, a folded line, a stepped impedance line, or a line with end loading, wherein: the stepped impedance open-circuit stub 5 is composed of at least two transmission line segments with different characteristic impedances connected in series; and / or the line with end loading open-circuit stub 5 has a capacitor-loaded conductor pattern at its open end. In this embodiment, the open-circuit stub 5 is a straight line.

[0075] It is understandable that, in this embodiment, the open stub 5 is arranged in a straight line. This allows for the introduction of a "parallel low-impedance resonant branch" effect at a preset suppression frequency without significantly increasing the main body size of the half-mode substrate integrated waveguide cavity (HMSIW) or disrupting the main transmission passband matching. This causes a strong energy shunting and equivalent impedance abrupt change in the main transmission path at that frequency, thereby forming a transmission zero. This achieves enhanced out-of-band spurious suppression, steeper band roll-off, and improved out-of-band selectivity. At the same time, the straight stub structure is simple, has good manufacturability, and high parameter repeatability. It is easy to accurately locate the transmission zero frequency through length fine-tuning and reduces the additional parasitic effects and process sensitivity caused by complex shapes such as folds, stepped impedances, or end loading.

[0076] like Figure 1 As shown, in a specific example provided in this application, the upper surface metal layer is further provided with one or more auxiliary slots 6, which are located within the upper projection range of the half-mode substrate integrated waveguide cavity. Specifically, in this embodiment, there are three auxiliary slots 6, and their projections on the upper metal layer 11 are all perpendicular to the open-circuit stub 5. This embodiment provides three auxiliary slots 6 within the upper projection range of the half-mode substrate integrated waveguide cavity, aiming to introduce additional response shaping degrees of freedom by controlling the perturbation of the upper surface metal current path and local field distribution: on the one hand, it can work with the open-circuit stub 5 to further deepen out-of-band attenuation, suppress parasitic modes or stray peaks, and improve stopband flatness; on the other hand, it can optimize band edge roll-off and out-of-band selectivity without significantly deteriorating passband matching and ripple; at the same time, the three slots act on the field strength / current strength positions in different regions in a multi-point distribution manner, which facilitates more stable frequency and suppression depth control and improves process tolerance by finely adjusting the slot size and position separately. Maintaining a perpendicular orientation between the slot and the open-circuit stub 5 reduces their direct strong coupling and mutual traction, minimizing unexpected resonance and zero-point drift. Furthermore, it enhances the ability to control different components of the cavity surface current through "orthogonal perturbation," thereby improving the controllability and stability of the overall response shaping. "Orthogonal perturbation" means that when the slot's orientation is perpendicular to the open-circuit stub 5 (and the main transmission direction), the slot primarily perturbs the surface current and electric field distribution of the other "directional component," thus separating it as much as possible from the perturbation mechanism formed by the open-circuit stub 5, achieving the effect of "no interference, each adjusting a separate part of the response."

[0077] It is understandable that the auxiliary slot 6 is a narrow opening structure set on the upper surface metal layer. By changing the current distribution of the upper surface metal and the equivalent electrical parameters of the cavity, it can adjust the cavity resonance characteristics and coupling characteristics, thereby optimizing the center frequency, passband matching, stopband suppression or passband edge roll-off characteristics of the filter.

[0078] In practical use, the initial design of the cavity size and coupling structure can be completed first based on the structure without auxiliary slots 6, so that the filter performance falls within the target frequency band range; then one or more auxiliary slots 6 are introduced in the projection range above the cavity, and the parameters are iteratively optimized by adjusting the number, length, width and relative position of the slots, so as to achieve frequency fine-tuning, coupling strength adjustment and suppression of parasitic response under the premise of meeting the processing capability constraints.

[0079] In one optional embodiment provided in this application, the dielectric substrate 1 has a relative permittivity of 3.0 to 3.8 and a loss tangent of 0.001 to 0.01.

[0080] In a specific example provided in this application, both the first metallized via 21 and the second metallized via 71 are regular hexagonal prism structures with a base surface that is a regular hexagon with a side length of 0.1 mm and a via height of 0.2975 mm. The spacing between adjacent first metallized vias 21 and adjacent second metallized vias 71 is 0.4 mm, which is the minimum net distance between the outer walls of adjacent vias. The dielectric substrate 1 has a relative permittivity of 3.3 and a loss tangent of 0.003. This filter operates in the vicinity of the 13.75 GHz to 14.5 GHz frequency band, such as... Figure 2 As shown, the transmission coefficient S21 is -19.075dB at 12.75GHz, -4.185dB at 13.75GHz, and -1.839dB at 14.5GHz. This demonstrates that the insertion loss is less than 2dB at the high end of the passband near 14.5GHz, while approximately 19dB of suppression is achieved at lower frequencies (e.g., 12.75GHz), exhibiting good frequency selectivity and passband roll-off characteristics. Furthermore, under the same center frequency and order design conditions, using a half-mode structure can reduce the lateral size of the device by approximately 50% compared to a full-mode SIW structure. This is beneficial for improving the integration density in high-density integrated applications such as phased array T / R components, while also maintaining signal transmission efficiency.

[0081] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A half-mode substrate integrated waveguide filter loaded with open-circuit stubs, characterized in that, include: The dielectric substrate (1) includes an upper metal layer (11), a dielectric layer (12) and a lower metal layer (13) disposed sequentially. The first via enclosure (2) includes a plurality of first metallized vias (21) that penetrate the dielectric substrate (1) and electrically connect the upper metal layer (11) and the lower metal layer (13). The plurality of first metallized vias (21) are arranged at intervals to form a lateral equivalent electric wall. The lateral equivalent electric wall, the side of the dielectric substrate (1) opposite to the first via enclosure (2), the upper metal layer (11) and the lower metal layer (13) together define the half-mode substrate integrated waveguide cavity. At least one open-circuit stub (5) is disposed in the half-mode substrate integrated waveguide cavity and electromagnetically coupled to the half-mode substrate integrated waveguide cavity at a predetermined position, and the end of the open-circuit stub (5) away from the coupling position remains open.

2. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, It also includes a second through-hole fence (7), which includes a plurality of second metallized through holes (71), which penetrate the dielectric substrate (1) and electrically connect the upper metal layer (11) and the lower metal layer (13); the second through-hole fence (7) is located in the half-mode substrate integrated waveguide cavity, covers a portion of the length along the propagation direction, and is spaced apart from the side of the dielectric substrate (1) away from the first through-hole fence (2).

3. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The cross-sections of the first metallized through hole (21) and the second metallized through hole (71) are both regular hexagonal, making the first metallized through hole (21) and the second metallized through hole (71) regular hexagonal prisms.

4. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The coupling between the open-circuit stub (5) and the half-mode substrate integrated waveguide cavity is achieved through at least one of the following methods: The open-circuit stub (5) is electrically connected to the conductor pattern of the upper metal layer (11) at the coupling position; The open-circuit stub (5) and the conductor pattern of the upper metal layer (11) are provided with a gap between the coupling positions to form a slot coupling; At least a portion of the open-circuit stub (5) is arranged parallel to and opposite the input excitation slot (3) and / or the output excitation slot (4) within a predetermined spacing range.

5. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The open-circuit stub (5) includes at least two stubs, which are located at different positions along the propagation direction and / or at different lateral positions along the width direction near the virtual magnetic wall side and near the lateral equivalent electric wall side.

6. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The electrical length of the open stub (5) is one-quarter of the waveguide wavelength or an odd multiple thereof in the transmission mode of the open stub (5), so that it exhibits low impedance resonance characteristics at the input end at the corresponding frequency, thereby forming a transmission zero on the main transmission path of the half-mode substrate integrated waveguide cavity.

7. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The shape of the open-circuit stub (5) is any one or a combination of a straight shape, a folded shape, a stepped impedance shape, or a shape with end loading, wherein: The stepped impedance open-circuit stub is composed of at least two transmission line segments with different characteristic impedances connected in series; and / or The open-circuit stub with end loading has a capacitor-loaded conductor pattern at its open end.

8. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, The upper metal layer (11) is also provided with one or more auxiliary slots (6), which are located within the upper projection range of the half-mode substrate integrated waveguide cavity.

9. The loaded open stub-loaded half-mode substrate integrated waveguide filter according to claim 1, wherein, The distance between two adjacent first metallized vias (21) in the first metallized via (21) array is no greater than twice the equivalent diameter of the first metallized via (21), and the equivalent diameter of the first metallized via (21) is less than one-tenth of the wavelength of the corresponding center frequency guided wave.

10. The loaded open stub-loaded half-mode substrate integrated waveguide filter of claim 1, wherein, Also includes: The input excitation slot (3) and the output excitation slot (4) are disposed on the upper metal layer (11) to couple the signal into the half-mode substrate integrated waveguide cavity and output it.

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