Coaxial microstrip-to-microstrip conversion device

Abstract

The invention relates to a coaxial microstrip-to-microstrip conversion device, which comprises a microstrip substrate, a signal transmission microstrip line, a signal receiving microstrip line and a conversion structure, wherein the signal transmission microstrip line, the signal receiving microstrip line and the conversion structure are arranged on the microstrip substrate; the conversion structure comprises a coaxial connector connected with the signal transmission microstrip line and the signal receiving microstrip line and a metal cavity arranged outside the coaxial connector; according to the invention, matching between the coaxial line and the transmission line is optimized, signal conversion between the two microstrip lines is realized, the reflection loss of the device is substantially reduced, and the transmission capability of the device is improved.

Description

Technical Field

[0001] The present application relates to the technical field of microwave radio frequency, and in particular to a microstrip to microstrip conversion device via coaxial transmission. Background Art

[0002] With the continuous development of communication technology, microwave technology has been widely used in wireless communications, radar, satellite communications and other fields. In these applications, microstrip lines are commonly used transmission line structures. However, due to the structural characteristics of microstrip lines, they often need to pass through appropriate devices when connecting or switching to reduce reflection loss and improve transmission efficiency.

[0003] The patent application number 202211740704.3 discloses a coaxial microstrip conversion structure, including an RF insulator, an insulator probe, a coaxial metal cavity, a microstrip line and a metal carrier. The microstrip line includes a microstrip line dielectric plate provided on the metal carrier and an impedance gradient center conductor provided on the microstrip line dielectric plate; one end of the RF insulator is flush with the side wall of one end of the metal carrier, and the other end of the RF insulator is positioned on the metal carrier through the coaxial metal cavity; the insulator probe passes through the central axis of the RF insulator and extends at both ends of the RF insulator, wherein one end of the insulator probe can be connected to a coaxial connector, and the other end of the insulator probe passes through the coaxial metal cavity to form an air coaxial line and is overlapped with the impedance gradient center conductor of the microstrip line. This conversion structure realizes the connection of a microstrip line to a coaxial connector through a coaxial structure, and the coaxial connector is connected to a coaxial cable to realize signal transmission. The current conversion structures are all coaxial-microstrip conversion structures / circuits, which realize signal transmission from a microstrip line to a coaxial cable. However, for circuits that require two or more microstrip lines to be used continuously, due to the limitations of the size, characteristic impedance, material, etc. of the microstrip lines, it is often impossible to achieve the purpose of transmitting one microstrip signal to another adjacent microstrip signal.

[0004] With respect to the above-mentioned related technologies, the inventor believes that there is a defect in the existing technologies in that they cannot realize signal conversion between two microstrip lines. Summary of the Invention

[0005] In order to solve the above technical problems, the present application provides a microstrip to microstrip conversion device through coaxial transmission.

[0006] The present application provides a microstrip to microstrip conversion device using coaxial cable, which adopts the following technical solution:

[0007] A conversion device for realizing microstrip to microstrip through coaxial transmission includes a microstrip substrate, a signal transmission microstrip line and a signal receiving microstrip line arranged on the microstrip substrate, and a conversion structure. The conversion structure includes a coaxial connector connected to the signal transmission microstrip line and the signal receiving microstrip line, and a metal cavity arranged outside the coaxial connector.

[0008] By adopting the above technical solution, using coaxial connectors and metal cavities, the matching between the coaxial and transmission lines is optimized, and the signal conversion between the two microstrip lines is realized, which significantly reduces the reflection loss of the device and improves the transmission capacity of the equipment.

[0009] Preferably, the coaxial connector includes a coaxial cylinder, an inner conductor sleeved outside the coaxial cylinder, and an outer conductor sleeved outside part of the inner conductor, the inner conductor close to the signal transmission microstrip line is located in the metal cavity, the two ends of the coaxial cylinder respectively pass through the inner conductor, and are respectively connected to the signal transmission microstrip line and the signal receiving microstrip line, and the part of the coaxial cylinder passing through the inner conductor is arranged outside the metal cavity, the outer conductor is arranged close to the signal receiving microstrip line side, and the gap between the outer conductor and the inner conductor is filled with a medium.

[0010] By adopting the above technical solution, a coaxial cylinder is set as a transition structure for signal transmission between two microstrip lines. The function of the inner conductor is to maintain electrical isolation, and the metal cavity can reduce dielectric loss. An outer conductor is set outside the inner conductor, and the gap between them is filled with dielectric to form a coaxial structure. It not only acts as a bridge, but also the outer conductor acts as an electromagnetic shield. In this way, the radio frequency signal is converted from the microstrip signal to the coaxial signal through the conversion structure. When the signal propagates in the coaxial line, it can obtain better shielding effect and anti-interference ability. At the output end, the coaxial signal is converted into a microstrip form again for smooth transmission to the subsequent circuit.

[0011] Preferably, the conversion structure also includes a rectangular metal block, the rectangular metal block includes a first rectangular block and a second rectangular block arranged on the right side of the first rectangular block, the metal cavity is opened on the end face of the first rectangular block close to the signal transmission microstrip line, and the metal cavity passes through the bottom end face of the first rectangular block, the length of the second rectangular block is greater than the length of the first rectangular block, and the right end face of the second rectangular block is connected to the outer conductor.

[0012] By adopting the above technical solution and arranging stepped rectangular metal blocks, impedance matching can be optimized, reflection can be reduced, and high-frequency performance can be improved.

[0013] Preferably, a curved transition section is respectively provided at the front and rear end faces of the rectangular metal block, and the curved transition section extends from the middle part of the end face of the first rectangular block to the right edge position of the end face of the second rectangular block. The curved transition section is formed by the end face of the first rectangular block convex in the direction away from the axis of the inner conductor and the end face of the second rectangular block concave in the direction close to the axis of the inner conductor, and the curvature of the curved transition section gradually decreases.

[0014] By adopting the above technical solution, the right-angle steps of the stepped rectangular metal block are changed into a sloped gradual transition, which can reduce the reflection caused by the impedance mutation.

[0015] Preferably, a matching ring is provided between the outer conductor and the rectangular metal block, the matching ring is coaxially arranged with the outer conductor, the cross-section of the matching ring is trapezoidal, and the inner diameter of the matching ring is adapted to the inner conductor, and the outer diameter is adapted to the outer conductor; there is a spacing between the matching ring and the outer conductor and the rectangular metal block, and the bottom of the matching ring is provided on the microstrip substrate through a ring base.

[0016] By adopting the above technical solution and adding a matching ring between the second rectangular block and the outer conductor, high-frequency response can be improved through capacitive loading.

[0017] Preferably, rectangular grooves are provided at the edges of the front and rear end surfaces of the second rectangular block, and the rectangular grooves are arranged in a one-to-one correspondence at the front and rear positions.

[0018] By adopting the above technical solution and providing a rectangular groove at the edge of the second rectangular block, the working bandwidth can be widened.

[0019] Preferably, the bottom edge of the metal cavity is formed with a rounded corner, and the shape of the metal cavity is arc-shaped.

[0020] By adopting the above technical solution and adding rounded corners to the edge of the metal cavity, the maximum field strength can be reduced.

[0021] Preferably, two trapezoidal seats are further provided on the microstrip substrate, the bottoms of the two trapezoidal seats are respectively soldered to the signal transmission microstrip line and the signal receiving microstrip line, the upper end surface of the trapezoidal seat is recessed downward to form an arc-shaped groove, and the coaxial cylinder is arranged in the arc-shaped groove.

[0022] By adopting the above technical solution, the trapezoidal seat can provide stable support for the coaxial cylinder, and the arc-shaped groove can be used to position and fix the coaxial cylinder to ensure good mechanical contact and electrical connection. The solder connection is for conductivity and fixation. This design can reduce impedance mutation and improve signal transmission efficiency.

[0023] Preferably, a plurality of through holes are provided at the bottom of the trapezoidal seat, and the through holes are arranged in an array, and the through holes extend along the height direction of the trapezoidal seat.

[0024] By adopting the above technical solution, a through hole is opened at the bottom of the trapezoidal seat to realize vertical interconnection between the microstrip line and the coaxial cylinder, and to realize the transmission between the microstrip signal and the coaxial signal.

[0025] Preferably, the signal transmission microstrip line and the signal receiving microstrip line are both provided with a multi-section cascaded impedance converter on one side close to the conversion structure, and the radius of each section of the impedance converter gradually increases from the side of the signal transmission microstrip line or the signal receiving microstrip line to the side of the conversion structure, and the connection of each section of the impedance converter is provided with a chamfer.

[0026] By adopting the above technical solution and arranging a multi-section impedance transformer in the transition region between the microstrip line and the coaxial structure, a wider frequency band can be covered.

[0027] In summary, this application includes at least one of the following beneficial technical effects:

[0028] 1. The matching between the coaxial and transmission lines is optimized, and the signal conversion between the two microstrip lines is realized, which significantly reduces the reflection loss of the device and improves the transmission capacity of the equipment.

[0029] 2. The inner conductor maintains electrical isolation, the metal cavity reduces dielectric loss, and the outer conductor acts as an electromagnetic shield. The RF signal is converted from the microstrip signal to the coaxial signal through the conversion structure. When the signal propagates in the coaxial cable, it can obtain better shielding effect and anti-interference ability. At the output end, the coaxial signal is converted into microstrip form again for smooth transmission to the subsequent circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a schematic structural diagram of a device for converting microstrip to microstrip via coaxial transmission according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of a microstrip to microstrip conversion device implemented through coaxial transmission according to another embodiment of the present invention.

[0032] Figure 3 yes Figure 2 Partial front view of .

[0033] Figure 4 It is a structural schematic diagram of the trapezoidal seat in the present invention.

[0034] Explanation of the accompanying symbols: 1. Microstrip substrate; 2. Signal transmission microstrip line; 3. Signal receiving microstrip line; 4. Conversion structure; 41. Coaxial connector; 411. Coaxial cylinder; 412. Inner conductor; 413. Outer conductor; 414. Curved transition section; 42. Metal cavity; 43. Rectangular metal block; 431. First rectangular block; 432. Second rectangular block; 433. Rectangular groove; 44. Rounded corner; 5. Trapezoidal seat; 51. Arc groove; 52. Through hole; 6. Matching ring; 7. Ring base; 8. Impedance converter. DETAILED DESCRIPTION

[0035] The following is combined with Figure 1-4 This application is described in further detail.

[0036] The embodiment of the present application discloses a device for converting microstrip to microstrip by coaxial connection. Figure 1-2 , including a microstrip substrate 1, a signal transmission microstrip line 2, a signal receiving microstrip line 3 and a conversion structure 4 arranged on the microstrip substrate 1, the conversion structure 4 including a coaxial connector 41 connected to the signal transmission microstrip line 2 and the signal receiving microstrip line 3 and a metal cavity 42 arranged outside the coaxial connector 41.

[0037] In this embodiment, since the characteristic impedances of microstrip lines of different line widths are different, direct connection will lead to reflection. Therefore, a conversion structure 4 is set between the two microstrip lines. When the radio frequency signal passes through, the microstrip signal can be converted into a coaxial signal through the conversion structure 4. When the signal propagates in the coaxial line, it can obtain better shielding effect and anti-interference ability. At the output end, the coaxial signal is converted into a microstrip form again for smooth transmission to the subsequent circuit.

[0038] Specifically, the present invention optimizes the simulation by adjusting the width and length of the microstrip line, the radius of the coaxial connector 41, and optimizing the shape of the microstrip line, the volume of the metal cavity 42, and the connection position through calculation and electromagnetic simulation software HFSS, and checks the S parameters, especially S11 and S21, to evaluate the matching effect between the transmission line and the coaxial line. Multiple optimizations ensure that the loss in the entire conversion process is minimized, thereby improving the overall transmission efficiency of the signal.

[0039] Specifically, the microstrip substrate 1 is a double-sided copper-clad dielectric board. The signal transmission microstrip line 2 and the signal receiving microstrip line 3 can be located on the left and right sides of the dielectric board, respectively, or on the top and bottom layers of the dielectric board, respectively. The thickness of the microstrip substrate 1 is preferably 0.508 mm, and the dielectric constant is preferably 3.66. The metal cavity 42 is used to control the distribution of high-frequency electromagnetic fields and reduce the equivalent dielectric constant. The cavity height is preferably 3 mm, and the aspect ratio is 3:1 (to suppress high-order modes).

[0040] Optionally, the coaxial connector 41 may be an SMA or BNC connector, and the characteristic impedance of the coaxial cable is consistent with that of the microstrip cable, which is 50Ω.

[0041] In some embodiments, the coaxial connector 41 includes a coaxial cylinder 411, an inner conductor 412 sleeved outside the coaxial cylinder 411, and an outer conductor 413 sleeved outside part of the inner conductor 412. The inner conductor 412 close to the signal transmission microstrip line 2 is located in the metal cavity 42. The two ends of the coaxial cylinder 411 respectively pass through the inner conductor 412 and are respectively connected to the signal transmission microstrip line 2 and the signal receiving microstrip line 3. The part of the coaxial cylinder 411 that passes through the inner conductor 412 is located outside the metal cavity 42. The outer conductor 413 is located close to the side of the signal receiving microstrip line 3, and the gap between the outer conductor 413 and the inner conductor 412 is filled with a medium.

[0042] In this embodiment, the inner conductor 412 serves to maintain electrical isolation, while the metal cavity 42 reduces dielectric loss and improves the structure's anti-interference capability. The outer conductor 413 is directly connected to the ground plane, providing electromagnetic shielding and achieving better shielding and anti-interference capabilities. Furthermore, an outer shielding layer is provided between the coaxial cylinder 411 and the inner conductor 412. The outer shielding layer is coated on the surface of the outer conductor 413 to secure the coaxial cylinder 411 and isolate the inner and outer conductors. The outer shielding layer is made of polytetrafluoroethylene, preferably with a dielectric constant of 2.1. The radius of the coaxial cylinder 411 is preferably 0.8 mm, the radius of the inner conductor 412 is preferably 2.8 mm, and the radius of the outer conductor 413 is preferably 4.8 mm. Furthermore, a gap of 0.1-0.3 mm is maintained between the inner conductor 412 and the wall of the metal cavity 42, forming capacitive coupling.

[0043] Conditions for suppressing high-order modes of the metal cavity 42:

[0044]

[0045] If =40GHz, then a×b<7.5×3.75mm 2 (TE10 model).

[0046] Specifically, when using HFSS simulation optimization, the key modeling settings include boundary conditions, excitation ports, and meshing. The boundary conditions include the metal cavity 42 and the substrate. The conductivity of the substrate is σ = 5.8 × 10^7 S / m. The excitation port covers the coaxial section + the microstrip line extends 3 times the line width. The meshing frequency is 40 GHz, the accuracy is λ / 20 → the mesh size is 0.375 mm. In addition, the simulation optimization also requires setting parameter scanning strategies, including coaxial radius optimization, transition line shape comparison, and the influence of the height of the metal cavity 42. Among them, the coaxial radius optimization requires scanning the diameter d = 0.6-1.0 mm of the coaxial cylinder 411 with a step size of 0.1 mm. The minimum value of S11 is observed. The target is S11 <-20 dB in the 30 GHz scenario. The cavity height h is adjusted to 2-5 mm. The Q value (capacitance and inductance) and the resonance point offset are analyzed. The results are as follows:

[0047] Parameter combination S11 (30GHz scenario) S21 (40GHz scenario) Field uniformity (E-field variance) d=0.8mm -24.5dB -0.28dB <![CDATA[0.15V 2 / m 2 ]]> d=1.0mm -12.3dB -0.82dB <![CDATA[0.67V 2 / m 2 ]]>

[0048] According to the above experimental results, it can be seen that the solution of the present invention has been verified in the frequency band below 40 GHz and can achieve the purpose of improving the overall transmission efficiency.

[0049] In some embodiments, the conversion structure 4 also includes a rectangular metal block 43, which includes a first rectangular block 431 and a second rectangular block 432 located on the right side of the first rectangular block 431. The first rectangular block 431 is provided with the metal cavity 42 on one end face close to the signal transmission microstrip line 2, and the metal cavity 42 passes through the bottom end face of the first rectangular block 431. The length of the second rectangular block 432 is greater than the length of the first rectangular block 431, and the right end face of the second rectangular block 432 is connected to the outer conductor 413.

[0050] Specifically, the rectangular metal block 43 in this embodiment is made of aluminum alloy, its surface is silver-plated, and the surface roughness Ra is less than 0.8μm. The metal cavity 42 and the inner conductor 412 are bonded with conductive adhesive, and the gap between the two is positioned by laser welding. The gap uniformity error is less than 0.005mm. In addition, the parallelism between the inner conductor 412 and the metal cavity 42 is less than 0.02mm.

[0051] Specifically, through the segmented design of the stepped metal block, multi-band impedance changes are achieved, for example: 50Ω→75Ω→50Ω; in addition, the stepped structure of the metal block can enhance the assembly rigidity and reduce the contact impedance fluctuation caused by high-frequency vibration; a controllable capacitor is formed between the metal cavity 42 and the gap formed between it and the inner conductor 412 to compensate for the difference in dielectric constant between the microstrip line and the coaxial structure; in addition, the first rectangular block 431 and the outer conductor 413 are contacted by an RF reed, and the contact pressure is less than 3N.

[0052] Specifically, the capacitance of the metal cavity 42 is:

[0053]

[0054] Where A is the gap area and d is the gap distance. High-frequency capacitive reactance is compensated by adjusting d.

[0055] In the step impedance transformation, the length of each step is set to λ / 4 (center frequency), and the impedance transition is in a geometric sequence, for example: Z2=Z target .

[0056] Specifically, the metal cavity 42 and the inner conductor 412 form a gap, and the gap distance is less than the skin depth, that is, δ≈1.26μm (in a frequency scenario of 10GHz), to avoid high-frequency current leakage; the inner conductor 412 can be gold-plated on the surface, and its thickness is greater than 2μm to reduce conductor loss.

[0057] Specifically, the sizes of the first rectangular block 431 and the second rectangular block 432 are selected as follows:

[0058] First block depth Among them, ∈ eff is the effective dielectric constant of the metal cavity 42.

[0059] The second depth Match the medium wavelength.

[0060] Specifically, performance simulation and actual measurement verification were performed in the 28 GHz frequency band according to the above parameters. The simulation results are as follows:

[0061] parameter No step structure Ladder optimization structure Return loss (S11) -12dB -23dB Insertion loss (S12) 0.45dB 0.18dB Phase consistency ±15℃ ±5℃

[0062] During actual measurement comparisons, a vector network analyzer (Keysight N5245B (10MHz-50GHz)) calibration method was used: TRL calibration to eliminate fixture errors. The results showed: the bandwidth was extended, the -15dB return loss bandwidth was increased from 5GHz (traditional structure) to 12GHz (stepped structure), and the power capacity was >10W (at a frequency of 30GHz) without arc breakdown.

[0063] As a modified embodiment, Figure 2As shown, a curved transition section 414 is respectively provided at the front and rear end faces of the rectangular metal block 43. The curved transition section 414 extends from the middle part of the end face of the first rectangular block 431 to the right edge position of the end face of the second rectangular block 432. The curved transition section 414 is formed by the end face of the first rectangular block 431 protruding in the direction away from the axis of the inner conductor 412 and the end face of the second rectangular block 432 being concave in the direction close to the axis of the inner conductor 412, and the curvature of the curved transition section 414 gradually decreases.

[0064] In this embodiment, the right-angle steps of the first rectangular block and the second rectangular block are changed to a gradual transition of an arc slope. The transition zone changes smoothly according to an exponential curve, and the curvature gradually decreases, which can make the impedance matching more continuous. This setting can achieve excellent ultra-wideband performance and extremely small reflection.

[0065] Specifically, the length of the curve transition section (L taper ) determines the electrical length of the gradient zone, usually 0.1λ-0.25λ (λ is the wavelength of the center frequency of the target frequency band), such as 30GHz band (λ=10mm), take L taper = 2.5mm (0.25λ); the exponential gradient curvature is given by the equation y(x) = D1 + (D2 - D1) * (1 - e -kx ) is controlled, k is the attenuation coefficient, where D1 and D2 are the depth values ​​of the first rectangular block and the second rectangular block respectively; in addition, low dielectric constant foam (such as 1.5) can be filled in the curve transition section to further smooth the field distribution.

[0066] Specifically, when performing simulation analysis, taking 40GHz ultra-wideband as an example, set the parameter L taper =5mm, k=0.4, ΔD(D2-D1)=2mm, and the simulation results show that S11<-30dB and S21 loss is only 0.1dB. It can be seen that the setting of this structure can significantly improve the broadband performance of microstrip-to-coaxial conversion.

[0067] In some embodiments, a matching ring 6 is provided between the outer conductor 413 and the rectangular metal block 43. The matching ring 6 is coaxially arranged with the outer conductor 413. The cross-section of the matching ring 6 is trapezoidal, and the inner diameter of the matching ring 6 is adapted to the inner conductor 412, and the outer diameter is adapted to the outer conductor 413. There is a spacing between the matching ring 6 and the outer conductor 413 and the rectangular metal block 43, and the bottom of the matching ring 6 is provided on the microstrip substrate 1 through a ring base 7.

[0068] In this embodiment, a matching ring is provided between the rectangular metal block and the outer conductor to improve high-frequency impedance matching and suppress signal reflection.

[0069] Specifically, the matching ring is a closed metal ring, which is arranged around the left side of the outer conductor and is 0.05-0.15mm away from the outer conductor to form a controllable capacitive coupling. It is 0.1-0.3mm away from the second rectangular block, and the capacitive reactance is adjusted by the air gap. The width of the metal ring is 0.5-2mm and the thickness is 0.2-0.5mm to ensure mechanical strength.

[0070] In some embodiments, rectangular grooves 433 are formed at the edges of the front and rear end surfaces of the second rectangular block 432 , and the rectangular grooves 433 are arranged in a one-to-one correspondence at the front and rear positions.

[0071] In this embodiment, by opening a groove at the edge of the second rectangular block 432, the active control parasitic capacitance can be adjusted and the high-frequency impedance matching can be optimized. At the same time, the edge of the groove needs to be chamfered, and the chamfer radius is about 0.05 mm.

[0072] Specifically, the length of the rectangular groove (L slot ) is usually λ / 8-λ / 4 (λ is the target frequency wavelength), such as the bandwidth of the 30GHz band, λ=10mm, the length is about 1.25-2.5mm, the width of the rectangular slot (W slot ) is usually 0.1-0.5mm, the depth of the groove (D slot ) is about 0.2-1mm; each slot can be regarded as a parallel capacitor, and its capacitance is approximately:

[0073]

[0074] Optionally, the rectangular slots can be replaced by U-shaped slots to enhance edge field coupling, or by periodic tooth slots to transmit surface waves in a specific frequency band through a periodic structure, or by arc slots to smooth the electric field transition and reduce radiation loss.

[0075] In some embodiments, a rounded corner 44 is formed at the bottom edge of the metal cavity 42 , and the metal cavity 42 is arc-shaped.

[0076] In this embodiment, in order to solve the problem of sudden increase in high-frequency insertion loss, a rounded corner 44 with a radius of 0.1 mm is provided on the edge of the metal cavity 42 to reduce the maximum field strength.

[0077] In some embodiments, the inner wall of the metal cavity 42 is loaded with absorbing material.

[0078] Specifically, in order to solve the problem of multi-path resonance caused by the resonance of the metal cavity 42 , an absorbing material, such as ferrite, is loaded on the inner wall of the cavity.

[0079] Specifically, the present invention significantly outperforms traditional solutions in broadband matching and mechanical stability through the coordinated design of the stepped metal block and the metal cavity 42, and is particularly suitable for high-frequency, high-reliability scenarios, for example, millimeter-wave radar front-end: used for low-loss interconnection between T / R modules and antenna array elements; inter-satellite links: withstanding extreme temperatures (-180°C to +150°C) and reliable connection in a vacuum environment; 6G terahertz communication: combined with a photonic crystal structure, the operating frequency band is extended to 300GHz.

[0080] In some embodiments, two trapezoidal seats 5 are further provided on the microstrip substrate 1, and the bottoms of the two trapezoidal seats 5 are respectively soldered to the signal transmission microstrip line 2 and the signal receiving microstrip line 3, and the upper end surface of the trapezoidal seat 5 is recessed downward to form an arc-shaped groove 51, and the coaxial cylinder 411 is arranged in the arc-shaped groove 51.

[0081] In this embodiment, a trapezoidal seat 5 is provided for connecting the coaxial cylinder 411 to the micro-wire, ensuring good electrical connection and mechanical stability. In addition, insertion loss and return loss can be reduced in high-frequency applications.

[0082] Specifically, the top width of the trapezoidal seat 5 is smaller than the bottom width, forming an impedance gradient transition, and an arc-shaped groove 51 is opened on the top, whose curvature radius matches the diameter of the coaxial cylinder 411, for example, a cylinder with a diameter of 1mm corresponds to a groove with R=0.5mm, to ensure that the contact area is maximized; after the cylindrical conductor is embedded in the arc-shaped groove 51, it is filled with low-temperature solder, such as Sn63Pb37, to form an electrical connection and mechanical fixation, and the solder coverage area is controlled within the length of the arc-shaped groove 51, with a typical value of 3-5 times the cylinder diameter, to avoid overflow affecting the surrounding area.

[0083] Specifically, during the design, the continuity of impedance needs to be considered, which includes the trapezoidal seat 5 as a microstrip line width gradient section to achieve a smooth impedance transition:

[0084]

[0085] Wherein, Δw is the width variation of the trapezoidal seat 5, L is the length of the trapezoid, and L≥λ / 4.

[0086] Impedance continuity also needs to consider the distributed capacitance formed by the arc-shaped groove 51 and the solder, which must meet the following requirements:

[0087]

[0088] Where f is the maximum operating frequency.

[0089] Specifically, the material of the trapezoidal seat 5 is matched with the CTE of the microstrip substrate. For example, a Rogers RO4350B substrate is selected to match the copper-tungsten alloy seat. The trapezoidal seat 5 is micro-milled or laser-etched, with a side wall verticality of <1° and a surface roughness Ra of <0.4μm. The depth of the arc groove is greater than 1.2 times the radius of the coaxial cylinder 411. For example, a radius of 1mm is matched with a groove depth of 1.2mm to prevent falling off. The processing error is ±0.01mm and requires calibration with a three-dimensional measuring instrument. The solder is selected from a flexible alloy, such as In97Ag3, which can withstand cycles from -55℃ to 125℃ and has a filling rate greater than 90%. A microporous capillary penetration process is used to enhance adhesion, and a micro-dispensing machine is used to quantitatively inject solder paste with an accuracy of ±0.01mm. 3 The reflow temperature curve peak is 245℃±3℃, and the time is 8-10 seconds; the solder surface is streamlined and the edge thickness is less than 0.1mm to reduce edge field distortion.

[0090] Specifically, when designing the dimensions of the various components of the trapezoidal seat 5, refer to the following calculation formula:

[0091] Trapezoidal seat 5 length L: Among them, when used at 10 GHz, the length is preferably 4.3 mm and the dielectric constant is preferably 4.3;

[0092] The curvature radius R of the arc groove 51 is R=0.5D conductor , where D = 1 mm and R = 0.5 mm are preferred for 10 GHz applications;

[0093] Solder volume V: V = πR 2 L fill , in 10GHZ application, the preferred R = 0.5mm, L = 3mm, and the volume is V = 2.36mm 3 .

[0094] In some embodiments, a plurality of through holes 52 are formed at the bottom of the trapezoidal seat 5 . The through holes 52 are arranged in an array, and the through holes 52 extend along the height direction of the trapezoidal seat 5 .

[0095] In this embodiment, a through hole 52 is provided on the trapezoidal seat 5 to suppress surface waves. Preferably, a ground via array is provided, and the calculation formula for the hole spacing is as follows: Among them, the hole spacing is preferably 2.1mm when used at 10GHZ.

[0096] Specifically, the trapezoidal seat 5 structure was simulated using HFSS, which defined the trapezoidal seat 5 parametric variables, scanned L: 3-6mm, R: 0.4-0.6mm, optimized S11, and added the solder material property σ = 2×10 6S / m. After optimization, if the 10 GHz scenario is selected, S11 = -27 dB, S21 = 0.08 dB; if the 30 GHz scenario is selected, S11 = -18 dB, S21 = 0.22 dB.

[0097] From the above results, it can be seen that the purpose of reducing losses can be achieved through the coordinated design of the trapezoidal seat 5 and the arc-shaped groove 51.

[0098] In some embodiments, open lines are provided on both the front and rear end surfaces of the trapezoidal seat 5 .

[0099] In this embodiment, the open line is provided on the trapezoidal seat 5 in order to suppress high-frequency resonance.

[0100] In some embodiments, the signal transmission microstrip line 2 and the signal receiving microstrip line 3 are both provided with a multi-section cascaded impedance converter 8 on one side close to the conversion structure, and the radius of each section of the impedance converter 8 gradually increases from the side of the signal transmission microstrip line 2 or the signal receiving microstrip line 3 to the side of the conversion structure 4, and the connection of each section of the impedance converter 8 is provided with a chamfer.

[0101] In this embodiment, a multi-section λ / 4 impedance transformer is introduced in the transition region between the microstrip line and the coaxial line to achieve good matching performance in a wider frequency band.

[0102] Specifically, the characteristic impedance of each impedance transformer needs to meet In addition, the converter usually selects 2-5 sections, preferably 3 sections (2 sections are used as an example in the figure), the length of each section is about 1.8mm, and the dielectric constant is 3.5mm; when using HFSS modeling optimization, the optimization target in-band ripple (S11 fluctuation) is <0.5dB, the operating bandwidth (S11<-20dB) is ≥2:1, and the parameter design is: 3-section Chebyshev converter, the characteristic impedance of each section is Z1=56.6Ω, Z2=65.8Ω, Z3=75Ω, and the substrate is FR4 (dielectric constant 4.4), thus obtaining the optimization results: S11<-22dB, S21 loss<0.25dB; it can be seen that the setting of this structure can realize low-loss transmission of microstrip-to-coaxial conversion.

[0103] The working principle of a conversion device for realizing microstrip to microstrip through coaxial in the present application is as follows: the radio frequency signal converts the microstrip signal into a coaxial signal through the conversion structure 4, and the signal can obtain better shielding effect and anti-interference ability when propagating in the coaxial line. At the output end, the signal converts the coaxial signal into a microstrip form again to be smoothly transmitted to the subsequent circuit, wherein a coaxial cylinder 411 is set as a transition structure for signal transmission between two microstrip lines, the role of the inner conductor 412 is to maintain electrical isolation, and the metal cavity 42 can play a role in reducing dielectric loss, and an outer conductor 413 is set outside the inner conductor 412, and the gap between them is filled with dielectric, forming a coaxial structure, which not only plays the role of a bridge, but also The outer conductor 413 acts as an electromagnetic shield. In addition, the stepped rectangular metal block can optimize impedance matching, reduce reflection, and improve high-frequency performance. The right-angled steps of the rectangular metal block are changed to a gradual transition of an arc slope. The transition zone changes smoothly according to an exponential curve, and the curvature gradually decreases, which can make the impedance matching more continuous. Multiple slots are opened at the edge of the transition zone to adjust the active control of parasitic capacitance and optimize high-frequency impedance matching. At the same time, a matching ring is set between the rectangular metal block and the outer conductor to improve high-frequency impedance matching and suppress signal reflection. Connecting the microstrip line and the coaxial cylinder 411 through the trapezoidal seat 5 can reduce impedance mutation and improve signal transmission efficiency.

[0104] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A coaxial microstrip to microstrip conversion device, characterized by: The invention comprises a microstrip substrate (1), a signal transmission microstrip line (2) and a signal reception microstrip line (3) provided on the microstrip substrate (1), and a conversion structure (4); the conversion structure (4) comprises a coaxial connector (41) connected to the signal transmission microstrip line (2) and the signal reception microstrip line (3), and a metal cavity (42) provided outside the coaxial connector (41).

2. The microstrip to microstrip conversion device according to claim 1, characterized in that: The coaxial connector (41) comprises a coaxial cylinder (411), an inner conductor (412) sleeved outside the coaxial cylinder (411), and an outer conductor (413) sleeved outside a portion of the inner conductor (412); the inner conductor (412) close to the signal transmission microstrip line (2) is located in the metal cavity (42); both ends of the coaxial cylinder (411) respectively pass through the inner conductor (412) and are respectively connected to the signal transmission microstrip line (2) and the signal receiving microstrip line (3); and the portion of the coaxial cylinder (411) that passes through the inner conductor (412) is located outside the metal cavity (42); the outer conductor (413) is located close to the signal receiving microstrip line (3), and a dielectric is filled in the gap between the outer conductor (413) and the inner conductor (412).

3. The device for converting microstrip to microstrip via coaxial transmission according to claim 2, characterized in that: The conversion structure (4) further includes a rectangular metal block (43), the rectangular metal block (43) including a first rectangular block (431) and a second rectangular block (432) arranged on the right side of the first rectangular block (431), the metal cavity (42) being provided on the end face of one side of the first rectangular block (431) close to the signal transmission microstrip line (2), and the metal cavity (42) passing through the bottom end face of the first rectangular block (431), the length of the second rectangular block (432) being greater than the length of the first rectangular block (431), and the right end face of the second rectangular block (432) being connected to the outer conductor (413).

4. The device for converting microstrip to microstrip via coaxial transmission according to claim 3, characterized in that: The front and rear end faces of the rectangular metal block (43) are respectively provided with a curved transition section (414), and the curved transition section (414) extends from the middle portion of the end face of the first rectangular block (431) to the right edge of the end face of the second rectangular block (432). The curved transition section (414) is formed by the end face of the first rectangular block (431) being convex in a direction away from the axis of the inner conductor (412) and the end face of the second rectangular block (432) being concave in a direction close to the axis of the inner conductor (412), and the curvature of the curved transition section (414) gradually decreases.

5. The device for converting microstrip to microstrip via coaxial transmission according to claim 4, characterized in that: A matching ring (6) is provided between the outer conductor (413) and the rectangular metal block (43); the matching ring (6) and the outer conductor (413) are coaxially arranged; the cross section of the matching ring (6) is trapezoidal; the inner diameter of the matching ring (6) is adapted to the inner conductor (412), and the outer diameter is adapted to the outer conductor (413); a spacing is provided between the matching ring (6), the outer conductor (413), and the rectangular metal block (43); and the bottom of the matching ring (6) is provided on the microstrip substrate (1) through a ring base (7).

6. The device for converting microstrip to microstrip via coaxial transmission according to claim 5, characterized in that: Rectangular grooves (433) are provided at the edge positions of the front and rear end surfaces of the second rectangular block (432), and the rectangular grooves (433) are arranged in a one-to-one correspondence at the front and rear positions.

7. The device for converting microstrip to microstrip via coaxial transmission according to claim 6, characterized in that: A rounded corner (44) is formed at the bottom edge of the metal cavity (42), and the shape of the metal cavity (42) is arc-shaped.

8. The device for converting microstrip to microstrip via coaxial transmission according to claim 2 or 4, characterized in that: Two trapezoidal seats (5) are further provided on the microstrip substrate (1); the bottoms of the two trapezoidal seats (5) are respectively connected to the signal transmission microstrip line (2) and the signal reception microstrip line (3) by soldering; the upper end surfaces of the trapezoidal seats (5) are recessed downward to form an arc-shaped groove (51); and the coaxial cylinder (411) is disposed in the arc-shaped groove (51).

9. The device for converting microstrip to microstrip via coaxial transmission according to claim 8, characterized in that: The bottom of the trapezoidal seat (5) is provided with a plurality of through holes (52), each through hole (52) is arranged in an array, and the through holes (52) extend along the height direction of the trapezoidal seat (5).

10. The device for converting microstrip to microstrip via coaxial transmission according to claim 2 or 8, characterized in that: The signal transmission microstrip line (2) and the signal receiving microstrip line (3) are both provided with a multi-section cascaded impedance converter (8) on one side close to the conversion structure (4), and the radius of each section of the impedance converter (8) gradually increases from the side of the signal transmission microstrip line (2) or the signal receiving microstrip line (3) to the side of the conversion structure (4), and the connection of each section of the impedance converter (8) is provided with a chamfer.

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