A k-band broadband rectangular waveguide to stripline transition structure

Abstract

The application discloses a K-band broadband rectangular waveguide to stripline transition structure, and relates to the field of microwave and millimeter wave integration. The structure comprises a rectangular waveguide, a substrate integrated waveguide and a stripline structure, the last two of which share a dielectric substrate, upper and lower layer metals and a metalized via array. The upper layer metal is provided with first and second coupling windows; the rectangular waveguide is vertically arranged on the upper layer metal and is connected to the first coupling window; the stripline metal extends to the second coupling window and is connected to the substrate integrated waveguide. The metalized via array comprises C-shaped and symmetrically distributed vias. The application realizes low-loss and broadband mode conversion between the waveguide and the stripline based on the substrate integrated waveguide right-angle transition, the specific via arrangement and the matching adjustment network, the working frequency band is 19.7-26.3 GHz, the return loss is less than-20 dB, and the system integration is improved.

Description

Technical Field

[0001] This invention relates to the field of microwave and millimeter-wave integration, specifically to a transition structure from a K-band broadband rectangular waveguide to a stripline. Background Technology

[0002] The statements in this section are provided only as background information in connection with this disclosure and may not constitute prior art.

[0003] In recent years, with the rapid iteration and deep integration of modern radar systems, electronic countermeasures equipment, and emerging information technologies such as 5G mobile communication and satellite internet, the millimeter-wave band has become a research hotspot and core application direction in the field of electronic information due to its unique advantages such as abundant bandwidth resources, high spatial resolution, good directivity, and compact device size. Compared with traditional microwave band devices, millimeter-wave components have technical characteristics such as smaller physical size, higher system integration, and significantly reduced overall size and weight, perfectly meeting the stringent requirements of miniaturization, lightweighting, and high performance for next-generation precision-guided weapons, airborne and spaceborne electronic equipment, and portable communication terminals.

[0004] In microwave and millimeter-wave systems, microstrip lines and rectangular waveguides remain the primary forms of signal transmission, and their technologies are relatively mature, finding widespread application in passive and active circuit design and system design. Meanwhile, with technological advancements, microwave multilayer dielectric substrate technology and millimeter-wave waveguide-microstrip transition structures have also been widely adopted, effectively breaking down the integration barriers between traditional three-dimensional and planar circuits.

[0005] In current RF circuit and antenna system design practices, various mature topologies such as probe transitions, fin transitions, and coupling slot transitions have been developed both domestically and internationally to address the mode conversion and impedance matching issues between rectangular waveguides and microstrip lines. However, research on "rectangular waveguide-stripline" conversion structures in the millimeter-wave band is relatively limited. Existing structures generally suffer from narrow operating bandwidth, high insertion loss, high processing precision requirements, and difficulties in vertical integration, making it difficult to meet the design requirements of next-generation millimeter-wave systems for broadband, high integration, miniaturization, and high reliability. Summary of the Invention

[0006] The purpose of this invention is to address the problems of narrow operating bandwidth, high insertion loss, high processing precision requirements, and high vertical integration difficulty in existing millimeter-wave waveguide-to-stripline conversion structures. It provides a K-band broadband rectangular waveguide-to-stripline transition structure, based on a substrate-integrated waveguide as a right-angle transition bridge, combined with a specially arranged array of metallized vias for electromagnetic boundary constraints, and by introducing an adjustable metal via network and a multi-order matching isolation ring. This achieves low-loss, wide-bandwidth, and efficient mode conversion between the rectangular waveguide and the stripline, effectively breaking through the bandwidth bottleneck of waveguide-to-planar transmission line conversion, and improving vertical space utilization and system horizontal integration.

[0007] The technical solution of the present invention is as follows: A transition structure from a K-band broadband rectangular waveguide to a stripline includes: a rectangular waveguide, a substrate integrated waveguide, and a stripline structure; The substrate integrated waveguide and the stripline structure share a dielectric substrate, an upper metal layer disposed on the upper surface of the dielectric substrate, a lower metal layer disposed on the lower surface of the dielectric substrate, and a metallized via array that penetrates the dielectric substrate and connects the upper metal layer and the lower metal layer. The upper metal layer is provided with a first coupling window and a second coupling window respectively; The substrate integrated waveguide further includes a metal patch disposed within the first coupling window; the rectangular waveguide is vertically disposed on the upper metal layer, and the port of the rectangular waveguide is connected to the first coupling window; The stripline structure also includes a stripline metal embedded inside the dielectric substrate, one end of which extends to the second coupling window and is connected to the substrate integrated waveguide. The metallized via array includes a plurality of metallized vias penetrating the dielectric substrate; wherein, some of the metallized vias are distributed in a C-shape along the three sides of the first coupling window, and the C-shaped metallized vias include two rows of metallized vias located on both sides of the metal patch; some of the metallized vias are symmetrically distributed along both sides of the second coupling window.

[0008] Furthermore, the C-shaped and symmetrically distributed metallized vias together enclose the dielectric substrate, which is equivalent to a metal wall with rectangular waveguide characteristics.

[0009] Furthermore, the transition structure also includes four adjustment metal through holes for adjusting the matching, all four adjustment metal through holes penetrating the dielectric substrate; The four adjustable metal through holes are symmetrically arranged inside the two rows of metallized through holes on both sides of the metal patch, and the four adjustable metal through holes are located at the connection between the first coupling window and the second coupling window.

[0010] Furthermore, a matching isolation ring is formed around the metal patch within the first coupling window; the length L2 of the matching isolation ring is 4.20 mm and the width W2 is 7.84 mm; the length L3 of the metal patch is 2.00 mm and the width W3 is 4.62 mm.

[0011] Furthermore, a matching isolation ring is formed around the strip metal within the second coupling window; the matching isolation ring includes isolation segments of different widths, wherein the width W5 of one isolation segment is 0.20 mm and the width W6 of the other isolation segment is 0.51 mm.

[0012] Furthermore, in the C-shaped distributed metallized vias, the center-to-center distance W1 between the two rows of metallized vias is 12.37 mm; the center-to-center length L1 of the C-shaped distributed metallized vias in the longitudinal direction is 7.98 mm.

[0013] Furthermore, the center-to-center spacing of the metallized vias symmetrically distributed along both sides of the second coupling window is different at both ends; the center-to-center spacing W4 at one end is 6.17 mm, and the center-to-center spacing W8 at the other end is 2.80 mm.

[0014] Furthermore, the width W7 of the strip metal is 0.7 mm.

[0015] Furthermore, the dielectric substrate is a single-layer RS300B material substrate with a thickness of 0.508mm; the rectangular waveguide is a standard WR-42 rectangular waveguide.

[0016] Furthermore, the operating frequency band of this transition structure is 19.7GHz to 26.3GHz, and the in-band return loss within the operating frequency band is less than -20dB.

[0017] Compared with existing technologies, the advantages of this invention are: 1. Expanding the operating bandwidth and reducing standing wave ratio. This invention innovatively introduces four symmetrical adjustable metal vias at the coupling window junctions, forming a parallel capacitive / inductive compensation network that can accurately counteract the harmful phase shift caused by structural discontinuities. Simultaneously, in conjunction with matching isolation rings with different gap widths within the second coupling window, multiple resonant points are constructed, significantly reducing port reflections. Simulation results show that this transition structure exhibits an in-band return loss of less than -20dB in the 19.7GHz~26.3GHz frequency band, with a relative bandwidth reaching 28.7%.

[0018] 2. Reduced insertion loss. The metallized via array (including C-type and symmetrical distribution) used in this invention encloses a metal wall with rectangular waveguide characteristics within the dielectric substrate, forming a semi-enclosed electromagnetic resonance and reflection cavity. This forces the electromagnetic wave to propagate forward, effectively preventing high-frequency energy leakage to the rear or sides within the substrate and significantly reducing the insertion loss of signal transmission.

[0019] 3. Improved system integration and lightweight design. This invention utilizes a right-angle structure to achieve the transition from three-dimensional rectangular waveguides to substrate-integrated waveguides and then to planar striplines. The striplines and substrate-integrated waveguides share the same dielectric substrate, resulting in an extremely compact structure that effectively reduces the thickness of the dielectric substrate. This provides an excellent miniaturized interconnection solution for radar front-ends, satellite communication, and other systems. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 This is a three-dimensional perspective view of the transition structure from the K-band broadband rectangular waveguide to the stripline of the present invention. Figure 2 This is a top-view perspective structural diagram of the present invention; Figure 3 for Figure 2 The corresponding dimension parameter annotation diagram is shown in the figure; Figure 4 For the present invention along Figure 1 A cross-sectional view along the AA direction; Figure 5 The figure shows the simulation results of the transition structure from the K-band broadband rectangular waveguide to the stripline of this invention.

[0022] Explanation of reference numerals in the attached figures: 1-Rectangular waveguide; 2-Metal patch; 3-Upper metal layer; 4-First coupling window; 5-Metalized via array; 6-Adjustable metal via; 7-Second coupling window; 8-Strip metal; 9-Dielectric substrate; 10-Lower metal layer. Detailed Implementation

[0023] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0024] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0025] Example 1 like Figures 1 to 5 As shown, this embodiment provides a transition structure from a K-band broadband rectangular waveguide to a stripline. This structure aims to achieve low-loss, wide-bandwidth, and efficient mode conversion between the waveguide and the planar stripline, providing a new high-performance, highly integrated interconnection solution for K-band radar, satellite communication, and other systems.

[0026] Specifically, combined Figure 1 3D perspective view and Figure 4 As can be seen from the cross-sectional view, the transition structure from the K-band broadband rectangular waveguide to the stripline includes: a rectangular waveguide 1, a substrate integrated waveguide, and a stripline structure. The substrate integrated waveguide and the stripline structure share a dielectric substrate 9, an upper metal layer 3 disposed on the upper surface of the dielectric substrate 9, a lower metal layer 10 disposed on the lower surface of the dielectric substrate 9, and a metallized via array 5 that penetrates the dielectric substrate 9 and connects the upper metal layer 3 and the lower metal layer 10. The upper metal layer 3 is provided with a first coupling window 4 and a second coupling window 7 respectively. The substrate integrated waveguide also includes a metal patch 2 disposed within the first coupling window 4; the rectangular waveguide 1 is vertically disposed on the upper metal 3, and the port of the rectangular waveguide 1 is connected to the first coupling window 4. The stripline structure also includes a stripline metal 8 embedded inside the dielectric substrate 9, one end of which extends to the second coupling window 7 and is connected to the substrate integrated waveguide.

[0027] In this embodiment, the transition structure employs a right-angle design to achieve a broadband transition from a rectangular waveguide to a substrate-integrated waveguide, and then to a stripline, moving from a longitudinal to a lateral direction. During energy transmission, the electromagnetic wave of the input signal (typically a TE10 mode) is fed into the vertically positioned rectangular waveguide 1. Through the coupling structure formed by the first coupling window 4 and the metal patch 2, the electromagnetic energy is vertically coupled into the substrate-integrated waveguide region within the dielectric substrate 9, thus converting it into a substrate-integrated waveguide transmission mode. Subsequently, the electromagnetic wave propagates forward along the substrate-integrated waveguide (considering the overall layout in the attached figures, the rectangular waveguide, substrate-integrated waveguide, and stripline structure are arranged roughly from right to left in the horizontal direction), smoothly transitions through the second coupling window 7 region, and finally enters the stripline metal 8, transforming into a quasi-TEM transmission mode for the stripline. This right-angle transition method significantly improves the lateral integration and longitudinal space utilization of millimeter-wave circuits, effectively breaking through the integration barrier of traditional three-dimensional waveguide circuits and planar transmission line conversion.

[0028] Furthermore, such as Figure 2 As shown in the top-view perspective, the metallized via array 5 includes a plurality of metallized vias penetrating the dielectric substrate 9; wherein, some of the metallized vias are distributed in a C-shape along three sides of the first coupling window 4, and the C-shaped distributed metallized vias include two rows of metallized vias located on both sides of the metal patch 2; some of the metallized vias are symmetrically distributed along both sides of the second coupling window 7. The C-shaped distributed metallized vias and the symmetrically distributed metallized vias together enclose the interior of the dielectric substrate 9, equivalent to a metal wall with rectangular waveguide characteristics.

[0029] Specific dimensions and structure are as follows: Figure 3 As shown, in the C-shaped distribution of the metallized vias, the center-to-center distance W1 between the two rows of metallized vias is 12.37 mm; the longitudinal center-to-center length L1 of the C-shaped metallized vias is 7.98 mm. The center-to-center distances at both ends of the symmetrically distributed metallized vias along the second coupling window 7 are different; the center-to-center distance W4 at one end is 6.17 mm, and the center-to-center distance W8 at the other end is 2.80 mm. It should be noted that the number of metallized vias in the metallized via array 5 is not limited, and those skilled in the art can flexibly set it according to actual processing requirements and isolation requirements.

[0030] The aforementioned metallized via array 5 not only serves as a physical connection between the upper and lower metal layers but also constitutes the transmission boundary of electromagnetic waves. The C-shaped via array forms a semi-enclosed electromagnetic resonance and reflection cavity, forcibly guiding the electromagnetic waves fed into the rectangular waveguide 1 forward, effectively preventing high-frequency energy from radiating backward or to the sides inside the dielectric substrate 9, thereby reducing insertion loss. At the same time, the via spacing symmetrically distributed along both sides of the second coupling window 7 gradually decreases from W4 (6.17 mm) to W8 (2.80 mm). This symmetrical gradual structure constitutes a smooth impedance transformer at the physical level, allowing the wider mode impedance of the substrate integrated waveguide to naturally transition to the low impedance state of the stripline, significantly improving broadband matching capability.

[0031] Furthermore, as a core optimization design of the present invention, the transition structure also includes four adjusting metal through holes 6 for adjusting the matching, all four adjusting metal through holes 6 penetrating the dielectric substrate 9; similarly referring to Figure 2 The four adjustable metal through holes 6 are symmetrically arranged on the inner side of the two rows of metallized through holes on both sides of the metal patch 2, and the four adjustable metal through holes 6 are located at the connection between the first coupling window 4 and the second coupling window 7.

[0032] In millimeter-wave bands (such as K-band), strong parasitic inductance and capacitance effects are generated at the multi-stage discontinuous connections between waveguides and striplines, which can easily lead to high-frequency resonance and impedance mismatch. This embodiment cleverly introduces four independent and symmetrical adjustable metal vias 6 in the transition region between the first coupling window 4 and the second coupling window 7. These four adjustable metal vias 6 introduce an additional parallel capacitive / inductive compensation network in the equivalent circuit. Those skilled in the art can precisely counteract the harmful phase shift caused by structural discontinuities by fine-tuning the specific positions and spacing of these four adjustable metal vias 6, thereby deeply optimizing the impedance matching state on both sides of the vias and significantly reducing standing waves caused by port reflections. This is a key technical feature enabling ultra-wideband low-loss transmission in this invention.

[0033] Furthermore, to further enhance the matching effect, a matching isolation ring is formed around the metal patch 2 within the first coupling window 4; the length L2 of the matching isolation ring is 4.20 mm, and the width W2 is 7.84 mm; the length L3 of the metal patch 2 is 2.00 mm, and the width W3 is 4.62 mm. A matching isolation ring is also formed around the strip metal 8 within the second coupling window 7; the matching isolation ring includes isolation segments of different widths, where one isolation segment has a width W5 of 0.20 mm, and another isolation segment has a width W6 of 0.51 mm. The width W7 of the strip metal 8 is 0.7 mm.

[0034] The precise dimensional design described above is the result of an optimal combination of parameters derived through extensive electromagnetic simulation optimization. In particular, the matching isolation ring within the second coupling window 7 employs isolation segments (W5 and W6) with different widths. This stepped or non-uniform gap width design breaks the limitation that a single gap easily generates narrowband resonance at a single frequency point, constructing multiple resonant points and further broadening the bandwidth range of impedance matching.

[0035] Finally, in this embodiment, the dielectric substrate 9 is a single-layer RS300B material substrate with a thickness of 0.508mm; the rectangular waveguide 1 is a standard WR-42 rectangular waveguide.

[0036] By adopting the above structure and parameter ratios, the transition structure provided by this invention can effectively reduce the thickness of the dielectric substrate, achieving a thinner and lighter system. For example... Figure 5 As shown in the simulation results, the operating frequency band of this transition structure covers 19.7GHz to 26.3GHz, with a relative bandwidth of 28.7%, and the in-band return loss (S11) within the operating frequency band is less than -20dB. Compared with the right-angle transition device of the prior art, this embodiment not only significantly expands the operating bandwidth and takes into account the requirements of miniaturization and low insertion loss, but also has a compact structure and is easier to manufacture, providing a new method for broadband applications of microwave and millimeter-wave transition structures. The principles of this invention should be understood so that the scope of protection of this invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the essence of this invention, and these modifications and combinations are still within the scope of protection of this invention.

[0037] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A transition structure from a K-band broadband rectangular waveguide to a stripline, characterized in that, include: Rectangular waveguide (1), substrate integrated waveguide and stripline structure; The substrate integrated waveguide and the stripline structure share a dielectric substrate (9), an upper metal layer (3) disposed on the upper surface of the dielectric substrate (9), a lower metal layer (10) disposed on the lower surface of the dielectric substrate (9), and a metallized via array (5) that penetrates the dielectric substrate (9) and connects the upper metal layer (3) and the lower metal layer (10). The upper metal layer (3) is provided with a first coupling window (4) and a second coupling window (7). The substrate integrated waveguide also includes a metal patch (2) disposed within the first coupling window (4); the rectangular waveguide (1) is vertically disposed on the upper metal (3), and the port of the rectangular waveguide (1) is connected to the first coupling window (4); The stripline structure also includes a stripline metal (8) embedded inside the dielectric substrate (9), one end of which extends to the second coupling window (7) and is connected to the substrate integrated waveguide. The metallized via array (5) includes a plurality of metallized vias penetrating the dielectric substrate (9); wherein, some of the metallized vias are distributed in a C-shape along the three sides of the first coupling window (4), and the C-shaped metallized vias include two rows of metallized vias located on both sides of the metal patch (2); some of the metallized vias are symmetrically distributed along both sides of the second coupling window (7).

2. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The C-shaped and symmetrically distributed metallized vias together enclose the dielectric substrate (9), which is equivalent to a metal wall with rectangular waveguide characteristics.

3. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The transition structure also includes four adjustment metal through holes (6) for adjusting the matching, and all four adjustment metal through holes (6) penetrate the dielectric substrate (9). The four adjustable metal through holes (6) are symmetrically arranged on the inner side of the two rows of metallized through holes on both sides of the metal patch (2), and the four adjustable metal through holes (6) are located at the connection between the first coupling window (4) and the second coupling window (7).

4. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, A matching isolation ring is formed around the metal patch (2) within the first coupling window (4); the length L2 of the matching isolation ring is 4.20 mm and the width W2 is 7.84 mm; the length L3 of the metal patch (2) is 2.00 mm and the width W3 is 4.62 mm.

5. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, A matching isolation ring is formed around the strip metal (8) within the second coupling window (7); the matching isolation ring includes isolation segments of different widths, wherein the width W5 of one isolation segment is 0.20 mm and the width W6 of the other isolation segment is 0.51 mm.

6. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, In the C-shaped distributed metallized vias, the center-to-center distance W1 between the two rows of metallized vias is 12.37 mm; the center-to-center length L1 of the C-shaped distributed metallized vias in the longitudinal direction is 7.98 mm.

7. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The metallized vias that are symmetrically distributed on both sides of the second coupling window (7) have different hole center spacings at both ends; the hole center spacing W4 at one end is 6.17 mm, and the hole center spacing W8 at the other end is 2.80 mm.

8. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The width W7 of the strip metal (8) is 0.7 mm.

9. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The dielectric substrate (9) is a single-layer RS300B material substrate with a thickness of 0.508mm; the rectangular waveguide (1) is a standard WR-42 rectangular waveguide.

10. The transition structure from K-band broadband rectangular waveguide to stripline according to claim 1, characterized in that, The operating frequency band of this transition structure is 19.7GHz to 26.3GHz, and the in-band return loss within the operating frequency band is less than -20dB.

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