Termination type coaxial waveguide adapter and optimization method thereof
By optimizing the termination type coaxial waveguide adapter through coupling probes and metal diaphragm structure, the problems of high frequency band processing difficulty and high cost are solved, and low-loss broadband switching is achieved, which is suitable for millimeter wave radar, communication and electronic countermeasures systems.
Patent Information
- Application Number
- CN202511294552.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2026-01-20
AI Technical Summary
Existing terminated coaxial waveguide adapters are difficult and costly to manufacture at high frequencies, and the multi-level stepped ridge structure is difficult to assemble with high precision within a narrow waveguide cavity.
By employing a coupling probe and a metal diaphragm structure, combined with a primary waveguide cavity, impedance transformation is achieved through optimized structural parameters, reducing fabrication complexity and cost.
While maintaining broadband low-loss performance, it reduces processing difficulty and production costs, and is suitable for signal switching at higher frequency bands.
Smart Images
Figure CN121367043A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a kind of end type coaxial waveguide adapter and its optimization method, which is suitable for millimeter wave radar, communication, electronic countermeasure and test system, for the adapter of millimeter wave signal between rectangular waveguide transmission line and coaxial transmission line. BACKGROUND
[0002] In 60GHz above frequency band, rectangular metal waveguide is always the mainstream signal transmission line form due to its low loss and easy to make characteristics.But the rigid characteristics of metal waveguide make the interconnection between waveguide transmission lines have stronger constraint, need higher waveguide port alignment accuracy, and the space position adjustable allowance is very small.The coaxial line has the characteristics of flexibility and bendability, and is more flexible in use.Especially with the higher-order mode suppression ability of 1.0mm, 0.8mm or even smaller diameter coaxial line and the gradual entry into practical stage of matching connector, in the frequency range of 60-220GHz, the mixed use of coaxial line and rectangular waveguide in the system will gradually increase.Therefore, it is necessary to solve the wideband and low loss adapter problem between rectangular waveguide interface and 1.0mm and higher specification coaxial connector.
[0003] The adapter structure between rectangular waveguide and coaxial connector is generally divided into two types, namely vertical type and end type.The vertical type means that the waveguide port direction and the coaxial port direction are perpendicular to each other in space, while the end type means that the waveguide port direction and the coaxial port direction are parallel and collinear in space.The existing end type coaxial waveguide adapter basically needs to use multi-stage stepped ridge structure.The stepped ridge is either integrally processed and made with the waveguide cavity, or separately made, and then fixed with the waveguide cavity by welding or screw and the like.The inner conductor of the coaxial connector is inserted into the stepped structure from the rear end of the waveguide, and then gradually impedance-transformed through the stepped ridge structure, and finally transitioned to the rectangular waveguide port at the front end.But in the frequency band above 60GHz, the cross-sectional size of rectangular waveguide gradually decreases as the frequency increases, and the multi-stage stepped ridge structure configured in the waveguide cavity is smaller.High-precision processing and assembly of multi-stage stepped ridge in narrow waveguide cavity require strong error control capability, and the requirements for process equipment and processing cost are relatively high. SUMMARY
[0004] The first object of the present application is to provide an end type coaxial waveguide adapter with lower processing and assembly difficulty and production cost while maintaining the wideband and low loss performance of the adapter;The second object of the present application is to provide an optimization method for the end type coaxial waveguide adapter.
[0005] Technical solution: The terminal type coaxial waveguide adapter of the application comprises a coaxial connector and a waveguide adapter fixedly connected, the coaxial connector has an inner conductor, the waveguide adapter has a waveguide adapter lower cavity and a waveguide adapter upper cavity, the waveguide adapter lower cavity has a waveguide adapter cavity structure, the waveguide adapter cavity structure comprises a primary waveguide cavity, a metal diaphragm and a standard rectangular waveguide arranged in sequence, the inner conductor extends into the primary waveguide cavity along the center of the primary waveguide wide side by a certain length, and the center of the inner conductor is kept at a certain distance from the short circuit surface of the waveguide cavity; the metal diaphragm is integrally formed in the waveguide adapter lower cavity, used for realizing impedance matching between the primary waveguide and the standard rectangular waveguide, deflecting the signal along the transmission direction of the waveguide by 90°, and realizing parallel collineation of the coaxial interface and the waveguide interface; the waveguide adapter upper cavity is in contact with the waveguide adapter lower cavity in the form of plane crimping, realizing the structural closure of the waveguide.
[0006] Further, the coaxial connector is a detachable connector with the wave bead and the flange separated from each other.
[0007] Further, the coaxial connector is an air wall-penetrating connector or a medium wall-penetrating connector.
[0008] Further, the cylindrical wall-penetrating structure of the coaxial connector is formed in the waveguide adapter lower cavity.
[0009] Further, the coaxial connector is fixedly connected with the waveguide adapter in the mode of screwing and crimping the flange.
[0010] Further, a cylindrical recessed groove is arranged at the contact surface of the waveguide adapter lower cavity and the coaxial connector flange, the cylindrical recessed groove is tightly matched with the cylindrical boss on the coaxial connector, and the inner conductor is limited.
[0011] Further, the waveguide adapter lower cavity and the waveguide adapter upper cavity are fixedly connected in the mode of screwing and crimping or brazing.
[0012] The optimization method of the terminal type coaxial waveguide adapter comprises the following steps:
[0013] (1) according to the working frequency band, selecting the waveguide size of the standard rectangular waveguide to be converted and the specification of the coaxial connector; the waveguide size of the standard rectangular waveguide comprises width b and depth 2b;
[0014] (2) based on the diameter d1 of the inner conductor of the selected coaxial connector, establishing a three-dimensional electromagnetic simulation model, optimizing the waveguide size of the primary waveguide cavity, the length l1 of the inner conductor extending into the primary waveguide cavity along the center of the primary waveguide wide side and the distance l2 from the center of the inner conductor to the short circuit surface of the waveguide cavity; the waveguide size of the primary waveguide cavity comprises width b1 and depth 2b1. s The optimization target is to realize the minimum voltage standing wave ratio and insertion loss in the required working frequency band;
[0015] (3) Based on the waveguide size of the primary waveguide cavity and the waveguide size of the standard rectangular waveguide determined in step (2), an integrated metal iris is added, and the structural parameters of the metal iris are optimized, and the optimization target is also to realize the minimum voltage standing wave ratio and insertion loss in the required working frequency band; the structural parameters of the metal iris include the thickness t of the metal iris, the distance s1 of the metal iris from the end of the primary waveguide, and the distance s2 of the metal iris from the start of the standard rectangular waveguide.
[0016] Further, below 170GHz, a coaxial connector with a specification of 1.0mm is selected.
[0017] Further, in the range of 170-220GHz, a coaxial connector with a specification of 0.8mm is selected.
[0018] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages:
[0019] (1) The coupling probe, primary waveguide and metal iris structure proposed in the present application comprehensively realize impedance transformation, which has lower structural complexity, assembly difficulty and production cost than the conventional complex multi-stage stepped ridge structure while maintaining large bandwidth and low loss performance.
[0020] (2) The present application has more advantages in high frequency bands. As the adapter operating frequency increases to 110GHz or above, the waveguide cavity cross-sectional size becomes smaller and smaller, and the processing and manufacturing feasibility and cost performance of the multi-stage stepped ridge structure responsible for impedance transformation will decrease rapidly. The coupling probe, primary waveguide and metal iris structure of the present application has much lower requirements for fine size than the multi-stage stepped ridge structure, so it is easier to implement at higher operating frequencies. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 and Figure 2 are structure schematic diagrams of the end-terminated coaxial waveguide adapter provided by the embodiment of the present application from different perspectives, wherein Figure 1 is a coaxial side view, Figure 2 is a waveguide side view;
[0022] Figure 3 and Figure 4 are assembly structure diagrams of the end-terminated coaxial waveguide adapter provided by the embodiment of the present application from different perspectives, wherein Figure 3 is a coaxial side view, Figure 4 is a waveguide side view;
[0023] Figure 5 is a structure schematic diagram of the upper cavity of the waveguide adapter in the embodiment of the present application;
[0024] Figure 6is a structural schematic view of the lower cavity of the waveguide adapter in the embodiment of the present application;
[0025] Figure 7 is Figure 6 a top view;
[0026] Figure 8 is a structural dimension parameter marking view of the lower cavity of the waveguide adapter in the embodiment of the present application;
[0027] Figure 9 is a back-to-back performance curve of the E-band end-terminated coaxial waveguide adapter in the embodiment of the present application. DETAILED DESCRIPTION
[0028] The present application will be further described below in conjunction with the accompanying drawings.
[0029] The Figures 1 to 8 accompanying drawings in the drawings are as follows:
[0030] 1, coaxial connector; 1-1, inner conductor; 1-2, cylindrical boss;
[0031] 2, waveguide adapter lower cavity; 2-1, cylindrical recessed groove; 2-2, air through-wall section; 2-3, primary waveguide cavity; 2-3-1, waveguide cavity short-circuit surface; 2-4, metal diaphragm; 2-5, standard rectangular waveguide;
[0032] 3, waveguide adapter upper cavity.
[0033] Embodiment 1
[0034] As shown in Figures 1 to 8 , embodiment 1 provides an end-terminated coaxial waveguide adapter, which comprises a coaxial connector 1 and a waveguide adapter.
[0035] In this embodiment, the coaxial connector 1 is in the form of an air through-wall connector, which has an inner conductor 1-1 with a diameter d1 and a length l. A cylindrical boss 1-2 with a diameter D and a protrusion height h is arranged on the flange surface of the coaxial connector 1.
[0036] The waveguide adapter adopts a split waveguide form, i.e. the structure constituting the waveguide cavity is split into two, which are the waveguide adapter lower cavity 2 and the waveguide adapter upper cavity 3. An air through-wall section 2-2 and a waveguide adapter cavity structure are formed on the waveguide adapter lower cavity 2, and the waveguide adapter cavity structure comprises a primary waveguide cavity 2-3, a metal diaphragm 2-4 and a standard rectangular waveguide 2-5 arranged in sequence, wherein the metal diaphragm 2-4 is integrally formed in the waveguide adapter lower cavity 2. A cylindrical recessed groove 2-1 is arranged at the flange contact surface of the waveguide adapter lower cavity 2 and the coaxial connector 1, and the cylindrical recessed groove 2-1 has a diameter of D+0.01 mm and a depth of h.
[0037] The inner conductor 1-1 extends into the primary waveguide cavity 2-3 along the center of the wide side of the primary waveguide for a set length. At the same time, the center of the inner conductor 1-1 maintains a set distance from the short surface 2-3-1 of the waveguide cavity. Then, the conversion between the primary waveguide cavity 2-3 and the standard rectangular waveguide 2-5 is completed through the metal diaphragm 2-4.
[0038] The upper cavity 3 of the waveguide adapter contacts the lower cavity 2 of the waveguide adapter via a planar press-fit, achieving structural enclosure of the waveguide. The lower cavity 2 and the upper cavity 3 of the waveguide adapter are secured together by screw press-fit or brazing. The coaxial connector 1 is fixedly connected to the assembly of the lower cavity 2 and the upper cavity 3 of the waveguide adapter (i.e., the waveguide adapter) by screw press-fitting a flange. The inner conductor 1-1 passes concentrically through the air-through section 2-2 in the lower cavity 2 of the waveguide adapter, and the tight fit between the cylindrical recess 2-1 and the cylindrical boss 1-2 limits the movement of the inner conductor 1-1.
[0039] Example 2
[0040] Example 2 provides an optimization method for the terminated coaxial waveguide adapter described in Example 1, comprising the following steps:
[0041] (1) Select the waveguide dimensions of the standard rectangular waveguide 2-5 to be converted and the specifications of the coaxial connector 1 according to the operating frequency band; the waveguide dimensions of the standard rectangular waveguide 2-5 include the width b and the depth 2b; below 170GHz, select a 1.0mm specification coaxial connector, and the diameter d2 of the corresponding air-through section 2-2 is 1.0mm; in the range of 170 to 220GHz, select a 0.8mm specification coaxial connector, and the diameter d2 of the corresponding air-through section 2-2 is 0.8mm.
[0042] (2) Based on the diameter d1 of the inner conductor 1-1 and the diameter d2 of the air-through section 2-2 of the selected coaxial connector 1, a three-dimensional electromagnetic simulation model is established. The waveguide dimensions of the primary waveguide cavity 2-3, the length l1 of the inner conductor 1-1 extending into the primary waveguide cavity 2-3 along the center of the wide side of the primary waveguide, and the distance l from the center of the inner conductor 1-1 to the short-circuit surface 2-3-1 of the waveguide cavity are calculated. s Optimization is performed to obtain the best performance. The optimization goal is to achieve the minimum voltage standing wave ratio (VSWR) and insertion loss within the required operating frequency band. The waveguide dimensions of the primary waveguide cavity 2-3 include width b1 and depth 2b (the depths of the primary waveguide cavity 2-3 and the standard rectangular waveguide 2-5 are consistent). In specific optimization, the initial values of the relevant structural dimensions are first roughly estimated based on basic electromagnetic theory and process parameter constraints. Then, the structural parameters are optimized using optimization algorithm toolkits built into the EDA software, such as the minimum gradient method and genetic algorithms.
[0043] (3) Based on the waveguide size of the primary waveguide cavity 2-3 and the waveguide size of the standard rectangular waveguide 2-5 determined in step (2), an integrated metal iris 2-4 is added, and the structural parameters of the metal iris 2-4 are optimized, and the optimization target is also to achieve the minimum voltage standing wave ratio and insertion loss in the required working frequency band. The structural parameters of the metal iris 2-4 include the thickness t of the metal iris 2-4, the distance s1 of the metal iris 2-4 from the end of the primary waveguide, and the distance s2 of the metal iris 2-4 from the start of the standard rectangular waveguide.
[0044] In the specific structural implementation, the length l of the air-through-wall section 2-2 in the waveguide adapter lower cavity 2 a = l - l1.
[0045] The optimization method provided in the embodiment can more efficiently achieve the optimization target in the premise of ensuring that the structural parameters are process-realizable through cascading optimization.
[0046] The working principle of the application is as follows:
[0047] The inner conductor 1-1 of the coaxial connector 1 extends into the waveguide cavity from the center of the wide side of the waveguide cavity by an appropriate length, in a manner of energy coupling probe, to convert the TEM mode electromagnetic wave in the coaxial transmission line into the TE mode transmitted in the waveguide. As a 1.0 mm or higher specification coaxial connector, the diameter of the inner conductor 1-1 is usually a fixed parameter corresponding to the connector specification and cannot be adjusted. Therefore, by controlling the length l1 of the coupling probe extending into the primary waveguide cavity 2-3, the narrow side width b1 of the primary waveguide cavity, and the distance l s of the coupling probe from the short-circuit surface of the primary waveguide cavity on the structure, the power coupling efficiency and the working frequency band can be optimized. In this structure, the inner conductor 1-1 of the coaxial connector 1 and the primary waveguide cavity 2-3 are perpendicular to each other, and in order to realize the parallel collineation between the coaxial connector and the waveguide port required by the termination structure, an integrated metal iris 2-4 is used with the waveguide adapter lower cavity 2, which deflects the signal along the transmission direction of the waveguide by 90° while realizing the impedance matching between the primary waveguide and the standard rectangular waveguide, thereby realizing the parallel collineation of the coaxial interface and the waveguide interface.
[0048] In order to illustrate the feasibility of the structure proposed in the application, a termination type waveguide coaxial adapter with a working frequency covering the E band (60-90 GHz) is designed, and the related structural parameters are as follows: b = 1.55 mm, t = 0.1 mm, s1 = 0.8 mm, s2 = 1.48 mm, l1 = 0.53 mm, l s = 0.78 mm, l a = 5.47 mm, b1 = 0.68 mm, d1 = 0.43 mm, d2 = 1.0 mm, and D = 4.4 mm. Figure 9The simulation performance curve shows that the S11 representing the return loss is less than -15 dB and the S21 representing the insertion loss is about 0.2 dB in the whole working frequency band, which achieves the expected design performance.
Claims
1. A terminated coaxial waveguide adapter, comprising: The coaxial connector (1) and the waveguide adapter are fixedly connected, the coaxial connector (1) has an inner conductor (1-1), the waveguide adapter has a waveguide adapter lower cavity (2) and a waveguide adapter upper cavity (3), the waveguide adapter lower cavity (2) has a waveguide adapter cavity structure, the waveguide adapter cavity structure comprises a primary waveguide cavity (2-3), a metal diaphragm (2-4) and a standard rectangular waveguide (2-5) arranged in sequence, the inner conductor (1-1) extends into the primary waveguide cavity (2-3) along the center of the primary waveguide wide side by a certain length, and the center of the inner conductor (1-1) is kept at a certain distance from a waveguide cavity short-circuit surface (2-3-1); the metal diaphragm (2-4) is integrally formed on the waveguide adapter lower cavity (2) and is used for realizing impedance matching between the primary waveguide and the standard rectangular waveguide (2-5) and deflecting the signal by 90 degrees along the transmission direction of the waveguide, thereby realizing parallel collineation of the coaxial interface and the waveguide interface; the waveguide adapter upper cavity (3) is in contact with the waveguide adapter lower cavity (2) in a planar crimping mode, thereby realizing structural closure of the waveguide.
2. The terminated coaxial waveguide adapter of claim 1, wherein, The coaxial connector (1) is a detachable connector in which the wave bead and the flange are separated from each other.
3. The terminated coaxial waveguide adapter of claim 1, wherein, The coaxial connector (1) is an air-through-wall connector or a medium-through-wall connector.
4. The terminated coaxial waveguide adapter of claim 3, wherein, The cylindrical wall-penetrating structure of the coaxial connector (1) is formed on the waveguide adapter lower cavity (2).
5. The terminated coaxial waveguide adapter of claim 4, wherein, The coaxial connector (1) is fixedly connected with the waveguide adapter by screwing and crimping the flange.
6. The terminated coaxial waveguide adapter of claim 5, wherein, A cylindrical recess (2-1) is arranged at the flange contact surface of the waveguide adapter lower cavity (2) and the coaxial connector (1), the cylindrical recess (2-1) is tightly matched with a cylindrical boss (1-2) on the coaxial connector (1), and the inner conductor (1-1) is limited.
7. The terminated coaxial waveguide adapter of claim 1, wherein, The waveguide adapter lower cavity (2) and the waveguide adapter upper cavity (3) are fixed by screwing and crimping or brazing.
8. A method of optimizing a terminated coaxial waveguide adapter as claimed in any one of claims 1 to 7, characterized in that, The method comprises the following steps: (1) selecting the waveguide size of the standard rectangular waveguide (2-5) to be converted and the specification of the coaxial connector (1) according to the working frequency band; the waveguide size of the standard rectangular waveguide (2-5) comprises a width b and a depth 2b; (2) based on the diameter d1 of the inner conductor (1-1) of the selected coaxial connector (1), a three-dimensional electromagnetic simulation model is established, and the waveguide size of the primary waveguide cavity (2-3), the length l1 of the inner conductor (1-1) extending into the primary waveguide cavity (2-3) along the center of the primary waveguide wide side, and the distance l2 of the center of the inner conductor (1-1) to the short-circuit surface (2-3-1) of the waveguide cavity are optimized s Optimization is performed, and the optimization target is to achieve the minimum voltage standing wave ratio and insertion loss in the required working frequency band; the waveguide size of the primary waveguide cavity (2-3) includes width b1 and depth 2b; (3) based on the waveguide size of the primary waveguide cavity (2-3) and the waveguide size of the standard rectangular waveguide (2-5) determined in step (2), an integrated metal diaphragm (2-4) is added, and the structural parameters of the metal diaphragm (2-4) are optimized, and the optimization target is also to realize the minimum voltage standing wave ratio and the insertion loss in the required working frequency band; the structural parameters of the metal diaphragm (2-4) comprise the thickness t of the metal diaphragm (2-4), the distance s1 from the end of the metal diaphragm (2-4) to the end of the primary waveguide, and the distance s2 from the metal diaphragm (2-4) to the start of the standard rectangular waveguide.
9. The method of optimizing a terminated coaxial waveguide adapter of claim 8, wherein, For below 170 GHz, a 1.0 mm specification coaxial connector is selected.
10. The method of optimizing a terminated coaxial waveguide adapter of claim 8, wherein, For 170-220 GHz, a 0.8 mm specification coaxial connector is selected.