Microstrip waveguide conversion structure

Abstract

The invention discloses a microstrip waveguide conversion structure, which comprises a non-standard rectangular waveguide, a stepped impedance conversion structure, a dielectric plate, a strip line and a vertical metal probe, the stepped impedance conversion structure is integrated in the non-standard rectangular waveguide; the dielectric plate is arranged at the top of the non-standard rectangular waveguide; the strip line is printed on the surface of the dielectric plate; the vertical metal probe is installed in the dielectric plate, the lower end of the vertical metal probe is inserted into the metal hollow cylinder to form electric connection, and the upper end of the vertical metal probe is connected with the strip line. According to the invention, the stepped impedance conversion structure is adopted to match the vertical metal probe, the probe is prevented from directly extending into the waveguide, and the design is changed into a waveguide surface fitting design, so that the risk of high-order mode excitation is reduced; one end of the vertical metal probe is connected with the microstrip line through a metal bonding pad, impedance continuity is optimized, and the influence caused by parasitic inductance is reduced; a stepped impedance conversion structure is introduced into the non-standard rectangular waveguide, and the working bandwidth is widened to 78%; and a low-loss dielectric plate is selected, so that the insertion loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of microstrip antenna technology, and more particularly to a microstrip waveguide conversion structure. Background Technology

[0002] In the field of microstrip antenna technology, the loss of microstrip lines increases significantly with length and frequency, causing antenna gain and G / T performance to fail to meet requirements. While waveguides offer low loss, using waveguide networks in large-scale antenna arrays results in an overall size and weight exceeding expectations. Therefore, existing technologies commonly employ a hybrid feeding scheme: large-scale microstrip arrays are divided into 2×2 or 4×4 subarrays, with microstrip networks used for feeding within the subarrays to maintain design flexibility, while waveguide networks are used for power combining between ports when subarrays are cascaded. This technique retains the ease of integration of microstrip antennas while overcoming the transmission loss problems at long distances and high frequencies inherent in purely microstrip network solutions.

[0003] In existing technologies, the transition from microstrip to waveguide can be divided into five main categories: 1. Probe Coupling Transition: A probe on the microstrip line extends into the waveguide and excites the waveguide master mode (TE) through electric field coupling. 10 Its structure is as follows: a vertical probe with a length of approximately λ is formed at the end of the microstrip line through a metallized via. g / 4, and the distance between the probe and the short-circuited end of the waveguide is tuned to λ. g Impedance matching is achieved by 4 / 4. This structure is very simple; 2. Slot-line coupling transition: The microstrip line couples to the waveguide via a radiating slot at the ground plane, with the slot line acting as a magnetic field coupler. Its structure involves an H-shaped or cross-shaped slot below the microstrip line to enhance coupling, requiring precise alignment between the waveguide and the microstrip line. This structure avoids the mechanical fragility of the probe and is suitable for high frequencies of 100+ GHz. 3. Substrate Integrated Waveguide (SIW) Transition: The microstrip line transitions to the SIW via a stepped impedance transformer before docking with a standard waveguide. The structure is a gradual transition from microstrip line to coplanar waveguide to SIW, with the waveguide impedance matched at the SIW end via a metallized via array. This structure allows for seamless integration and is suitable for the Sub-THz frequency band. 4. Fin Transition: The microstrip line gradually transitions to a fin, and then is coupled to the waveguide via an E-plane probe. Its structure is a multi-stage transition from microstrip line to coplanar waveguide to fin, with optimized matching of the asymmetric fin structure at the fin's end. 5. Patch Antenna Coupling Transition: The microstrip patch acts as the radiating element, receiving energy through a waveguide opening. Its structure is as follows: the patch size is set to the target size corresponding to the resonant point, and the waveguide opening position is typically offset from the center λ. g / 4, this structure is compatible with planar processes and is suitable for array integration.

[0004] Of the five options listed above: The first probe-coupled transition structure has a working bandwidth of only about 15%, and the loss will increase at high frequencies due to probe parasitic parameters. The technical defects of the probe-coupled transition structure are: the probe will induce high-order mode excitation at high frequencies, the mode purity in the waveguide will decrease, the parasitic capacitance will cause impedance mismatch, and the cantilever probe is prone to breakage under vibration. The second type of slot-line coupled transition structure requires very high machining precision (slot width < 0.1λ0), which increases the machining difficulty; the technical drawback of the slot-line coupled transition structure is that the surface wave loss of the dielectric substrate can reach 30% of the total loss; The third issue is that the dielectric loss of the substrate-integrated waveguide transition structure leads to a reduction in efficiency. The technical defects of the substrate-integrated waveguide transition structure are: the high-frequency conductor loss accounts for <30%, and the dielectric loss causes insertion loss >2dB / cm. The fourth type is a very complex fin transition structure that requires a multilayer dielectric substrate. The technical drawback of the fin transition structure is that the asymmetric structure of the fin excites parasitic modes, resulting in fluctuations in in-band return loss (±3dB). The fifth type is a patch antenna coupling transition structure with a very narrow operating bandwidth, an excessively high patch Q value, a -10dB bandwidth of only 5-10%, and requires tuning of the back cavity depth.

[0005] Therefore, it is necessary to develop a microstrip waveguide conversion structure to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to design a microstrip waveguide conversion structure to solve the above problems.

[0007] The present invention achieves the above objectives through the following technical solutions: A microstrip waveguide conversion structure includes: Non-standard rectangular waveguide; the top of the non-standard rectangular waveguide has an opening in the outer wall of the waveguide; Stepped impedance transformation structure; The stepped impedance transformation structure is integrated inside a non-standard rectangular waveguide. The stepped impedance transformation structure is formed as a stepped structure with the height gradually increasing from the first end to the second end. A hollow metal cylinder is vertically set on the second end of the stepped impedance transformation structure, and the second end of the stepped impedance transformation structure is placed in the opening on the outer wall of the waveguide. Dielectric substrate; the dielectric substrate is placed on top of the non-standard rectangular waveguide; Striplines are used for signal input; the striplines are printed on the surface of the substrate. Vertical metal probe; The vertical metal probe is installed inside the dielectric substrate. The lower end of the vertical metal probe is inserted into a hollow metal cylinder to form an electrical connection, and the upper end of the vertical metal probe is connected to the stripline.

[0008] The beneficial effects of this invention are as follows: 1. In this application, a stepped impedance transformation structure is used to match the vertical metal probe, avoiding the probe from directly extending into the waveguide. Instead, a waveguide surface-mount design is used, which reduces the risk of high-order mode excitation. One end of the vertical metal probe is connected to the microstrip line through a metal pad, which optimizes impedance continuity and reduces the impact of parasitic inductance. 2. Introducing a stepped impedance transformation structure inside the non-standard rectangular waveguide widens the operating bandwidth to 78%; 3. Select low-loss dielectric substrates to reduce insertion loss. Attached Figure Description

[0009] Figure 1 This is a top view of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the vertical moving mechanism in this invention; Figure 4 This is a schematic diagram of the clamp installation structure in this invention.

[0010] The diagram is labeled as follows: 1. Non-standard rectangular waveguide; 2. Stepped impedance transformation structure; 3. Stripline; 4. Dielectric substrate; 5. Vertical metal probe; 6. First shielding ground hole; 7. Waveguide outer wall opening; 8. Second shielding ground hole. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0012] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0013] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0014] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0015] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0016] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0017] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] like Figure 1 and 2 As shown, a microstrip waveguide conversion structure includes: Non-standard rectangular waveguide 1; The top of the non-standard rectangular waveguide 1 is provided with an opening 7 on the outer wall of the waveguide; Stepped impedance transformation structure 2; Stepped impedance transformation structure 2 is integrated inside the non-standard rectangular waveguide 1, and impedance gradual matching is achieved through multi-level stepped structure; Stepped impedance transformation structure 2 is formed as a stepped structure with gradually increasing height from the first end to the second end, and a metal hollow cylinder is vertically set on the second end of the stepped impedance transformation structure 2, and the second end of the stepped impedance transformation structure 2 is placed in the opening 7 on the outer wall of the waveguide. Dielectric substrate 4; Dielectric substrate 4 is placed on top of non-standard rectangular waveguide 1; Stripline 3 is used for signal input; stripline 3 is printed on the surface of dielectric substrate 4; Vertical metal probe 5; Vertical metal probe 5 is installed inside dielectric substrate 4. The lower end of vertical metal probe 5 is inserted into a hollow metal cylinder to form an electrical connection coupling. The upper end of vertical metal probe 5 is connected to stripline 3. Multiple first shielding ground holes 6 are formed in the dielectric substrate 4; the multiple first shielding ground holes 6 are arranged in two rows on both sides of the stripline 3; Multiple second shielding holes 8 are formed within the dielectric substrate 4; the multiple second shielding holes 8 are arranged around the vertical metal probe 5.

[0019] The first shielding ground hole 6 and the second shielding ground hole 8 are provided to suppress signal leakage and maintain field integrity. The waveguide outer wall opening 7 allows for direct contact between the stepped transformation structure and the metal probe on the waveguide surface.

[0020] In some embodiments, the width of the stepped impedance transformation structure 2 is 1.3 mm, and the diameter of the hollow metal cylinder is 0.3 mm.

[0021] In some embodiments, the diameter of the vertical metal probe 5 is 0.2 mm.

[0022] In some embodiments, the diameter of the first shielding ground hole 6 is 0.15 mm, and the distance between two adjacent first shielding ground holes 6 is 0.38 mm.

[0023] In some embodiments, the diameter of the second shielding hole 8 is 0.15 mm, and the distance between two adjacent first shielding holes 6 is 0.38 mm.

[0024] In some embodiments, the long side a of the non-standard rectangular waveguide 1 is 9.5 mm and the short side b is 3 mm.

[0025] The working principle of this application is as follows: The signal is input through the stripline 3 and vertically coupled to the surface of the non-standard rectangular waveguide through the vertical metal probe 5. Through the design of the waveguide outer wall opening 7 of the non-standard rectangular waveguide, the stepped impedance transformation structure 2 extends upward and forms direct contact with the vertical metal probe 5, thereby achieving the following functions: ① Mode conversion: Convert the quasi-TEM mode of stripline 3 to the TE mode of the waveguide. 10 mold; ②Broadband matching: The stepped structure optimizes impedance transition and broadens the operating bandwidth.

[0026] The structure is connected to a waveguide network at its end, making it suitable for high-frequency applications and offering the advantages of low loss and wide bandwidth.

[0027] The microstrip-waveguide transition structure proposed in this application achieves the following: Figure 3 and Figure 4 It exhibits excellent performance with wide bandwidth and low loss.

[0028] Broadband matching characteristics: ① Achieve a relative bandwidth of 78% (16.68GHz-38.01GHz) under the condition that the VSWR ≤ 2. ② Under the condition that the VSWR ≤ 1.5, it can still achieve a relative bandwidth of 63% (17.23GHz-33.07GHz). Low loss characteristics: ① The maximum insertion loss across the entire frequency band is only 0.53dB; ② In the frequency band where VSWR≤1.5, the insertion loss is further reduced to 0.19dB.

[0029] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microstrip waveguide conversion structure, characterized in that, include: Non-standard rectangular waveguide; the top of the non-standard rectangular waveguide has an opening in the outer wall of the waveguide; Stepped impedance transformation structure; The stepped impedance transformation structure is integrated inside a non-standard rectangular waveguide. The stepped impedance transformation structure is formed as a stepped structure with the height gradually increasing from the first end to the second end. A hollow metal cylinder is vertically set on the second end of the stepped impedance transformation structure, and the second end of the stepped impedance transformation structure is placed in the opening on the outer wall of the waveguide. Dielectric substrate; the dielectric substrate is placed on top of the non-standard rectangular waveguide; Striplines are used for signal input; the striplines are printed on the surface of the substrate. Vertical metal probe; The vertical metal probe is installed inside the dielectric substrate. The lower end of the vertical metal probe is inserted into a hollow metal cylinder to form an electrical connection, and the upper end of the vertical metal probe is connected to the stripline.

2. The microstrip waveguide conversion structure according to claim 1, characterized in that, The microstrip waveguide conversion structure also includes multiple first shielding ground holes formed in the dielectric substrate, which are arranged in two rows on both sides of the stripline.

3. The microstrip waveguide conversion structure according to claim 1, characterized in that, The microstrip waveguide conversion structure also includes multiple second shielding ground holes formed within the dielectric substrate, which are arranged around the vertical metal probe.

4. A microstrip waveguide conversion structure according to claim 1, characterized in that, The width of the stepped impedance transformation structure is 1.3 mm, and the diameter of the hollow metal cylinder is 0.3 mm.

5. A microstrip waveguide conversion structure according to claim 1, characterized in that, The diameter of the vertical metal probe is 0.2 mm.

6. A microstrip waveguide conversion structure according to claim 1, characterized in that, The diameter of the first shielding ground hole is 0.15 mm, and the distance between two adjacent first shielding ground holes is 0.38 mm.

7. A microstrip waveguide conversion structure according to claim 1, characterized in that, The diameter of the second shielding hole is 0.15 mm, and the distance between two adjacent first shielding holes is 0.38 mm.

8. A microstrip waveguide conversion structure according to claim 1, characterized in that, The long side a of the non-standard rectangular waveguide has a length of 9.5 mm and a short side b has a length of 3 mm.

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