A coaxial microstrip-to-microstrip conversion device

Abstract

The application relates to a conversion device for converting a microstrip into a microstrip through a coaxial structure, which comprises a microstrip substrate, a signal transmission microstrip line arranged on the microstrip substrate, a signal receiving microstrip line and a conversion structure, 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; the application has the technical effect of optimizing the matching between the coaxial structure and the transmission line, realizing the conversion of signals between the two microstrip lines, significantly reducing the reflection loss of the device and improving the transmission capacity of the equipment.

Description

Technical Field

[0001] This application relates to the field of microwave radio frequency technology, and in particular to a microstrip to microstrip conversion device that achieves microstrip conversion via coaxial connection. Background Technology

[0002] With the continuous development of communication technology, microwave technology has been widely used in wireless communication, radar, satellite communication 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 require appropriate devices to reduce reflection loss and improve transmission efficiency when connected or switched.

[0003] Patent application number 202211740704.3 discloses a coaxial microstrip conversion structure, including a radio frequency insulator, an insulator probe, a coaxial metal cavity, a microstrip line, and a metal carrier. The microstrip line includes a microstrip line dielectric substrate disposed on the metal carrier and an impedance-gradient center conductor disposed on the microstrip line dielectric substrate. One end of the radio frequency insulator is flush with one end sidewall of the metal carrier, and the other end of the radio frequency insulator is positioned on the metal carrier through the coaxial metal cavity. The insulator probe passes through the central axis of the radio frequency insulator and extends at both ends of the radio frequency insulator. 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 structure and overlaps the impedance-gradient center conductor of the microstrip line. This conversion structure enables microstrip lines to connect to coaxial connectors via coaxial structures, and these coaxial connectors then connect to coaxial cables to transmit signals. Current conversion structures are all coaxial-microstrip conversion structures / circuits, which realize signal transmission from microstrip lines to coaxial cables. However, for circuits that require two or more microstrip lines to be used continuously, due to limitations in the size, characteristic impedance, and materials of microstrip lines, it is often impossible to achieve the goal of transmitting one microstrip signal to another adjacent microstrip signal.

[0004] Regarding the aforementioned technologies, the inventors believe that existing technologies have the drawback of being unable to achieve signal conversion between two microstrip lines. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a microstrip to microstrip conversion device that achieves microstrip conversion via coaxial connection.

[0006] This application provides a microstrip to microstrip conversion device via coaxial connection, which adopts the following technical solution:

[0007] A microstrip to microstrip conversion device via coaxial connection includes a microstrip substrate, a signal transmission microstrip line and a signal receiving microstrip line disposed 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 disposed outside the coaxial connector.

[0008] By adopting the above technical solution, using coaxial connectors and metal cavities, the matching between the coaxial cable and the transmission line 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 capability of the device.

[0009] Preferably, the coaxial connector includes a coaxial cylinder, an inner conductor sleeved outside the coaxial cylinder, and an outer conductor sleeved outside a portion of the inner conductor. The inner conductor, which is close to the signal transmission microstrip line, is located within the metal cavity. Both ends of the coaxial cylinder pass through the inner conductor and are respectively connected to the signal transmission microstrip line and the signal receiving microstrip line. The portion of the coaxial cylinder that extends out of the inner conductor is located outside the metal cavity. The outer conductor is located close to the signal receiving microstrip line, and the gap between the outer conductor and the inner conductor is filled with a dielectric material.

[0010] By adopting the above technical solution, a coaxial cylinder is set as the transition structure for signal transmission between two microstrip lines. The inner conductor maintains electrical isolation, while the metal cavity reduces dielectric loss. An outer conductor is placed outside the inner conductor, and the gap between them is filled with dielectric, forming a coaxial structure. This structure not only acts as a bridge but also provides electromagnetic shielding. In this way, the radio frequency signal is converted from a microstrip signal to a coaxial signal through the conversion structure. When the signal propagates in the coaxial path, it can achieve better shielding and anti-interference capabilities. At the output end, the coaxial signal is converted back into microstrip form for smooth transmission to subsequent circuits.

[0011] Preferably, the conversion structure further includes a rectangular metal block, which includes a first rectangular block and a second rectangular block located to the right of the first rectangular block. The first rectangular block has a metal cavity on its end face near the signal transmission microstrip line, and the metal cavity penetrates 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 setting up stepped rectangular metal blocks, impedance matching can be optimized, reflections can be reduced, and high-frequency performance can be improved.

[0013] Preferably, the rectangular metal block has curved transition sections on its front and rear end faces. The curved transition sections extend from the middle part of the end face of the first rectangular block to the right edge of the end face of the second rectangular block. The curved transition sections are formed by the end face of the first rectangular block protruding in a direction away from the axis of the inner conductor and the end face of the second rectangular block being recessed in a direction close to the axis of the inner conductor, and the curvature of the curved transition sections gradually decreases.

[0014] By adopting the above technical solution, the right-angled steps of the stepped rectangular metal block are changed to a gradual transition of slope, which can reduce the reflection caused by impedance abrupt change.

[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, while the outer diameter is adapted to the outer conductor. A gap is provided between the matching ring, the outer conductor, and the rectangular metal block, and the bottom of the matching ring is disposed on the microstrip substrate through a ring base.

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

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

[0018] By adopting the above technical solution, a rectangular groove can be opened at the edge of the second rectangular block to widen the working bandwidth.

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

[0020] By adopting the above technical solution, adding rounded corners to the edges of the metal cavity can reduce the maximum electric field strength.

[0021] Preferably, the microstrip substrate is further provided with two trapezoidal seats, 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 of the trapezoidal seat is recessed downward to form an arc-shaped groove, and the coaxial cylinder is disposed in the arc-shaped groove.

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

[0023] Preferably, the bottom of the trapezoidal base has multiple through holes arranged in an array, and the through holes extend along the height direction of the trapezoidal base.

[0024] By adopting the above technical solution, a through hole is opened at the bottom of the trapezoidal base to realize the 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, both the signal transmission microstrip line and the signal receiving microstrip line have multiple cascaded impedance transformers on the side near the conversion structure, and the radius of each impedance transformer gradually increases from the signal transmission microstrip line or the signal receiving microstrip line side towards the conversion structure side, and each impedance transformer connection point has a chamfer.

[0026] By adopting the above technical solution, multiple impedance transformers can be set in the transition region between microstrip lines and coaxial structures, which can cover a wider frequency band.

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

[0028] 1. The matching between the coaxial cable and the transmission line was optimized, enabling signal conversion between the two microstrip lines. This significantly reduced the reflection loss of the device and improved its transmission capability.

[0029] 2. The inner conductor maintains electrical isolation, the metal cavity reduces dielectric loss, and the outer conductor provides electromagnetic shielding. The radio frequency signal is converted from a microstrip signal to a coaxial signal by the conversion structure. When the signal propagates in the coaxial path, it can achieve better shielding and anti-interference capabilities. At the output end, the signal is converted back into microstrip form for smooth transmission to subsequent circuits. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a microstrip to microstrip conversion device according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of a microstrip to microstrip conversion device according to another embodiment of the present invention, which achieves microstrip to microstrip conversion via coaxial connection.

[0032] Figure 3 yes Figure 2 A partial front view.

[0033] Figure 4 This is a schematic diagram of the trapezoidal base in this invention.

[0034] Explanation of reference numerals in the attached figures: 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 slot; 44. Rounded corner; 5. Trapezoidal base; 51. Arc-shaped groove; 52. Through hole; 6. Matching ring; 7. Ring substrate; 8. Impedance transformer. Detailed Implementation

[0035] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0036] This application discloses a microstrip to microstrip conversion device that uses a coaxial connection. (See also...) Figure 1-2 It includes a microstrip substrate 1, a signal transmission microstrip line 2 and a signal receiving microstrip line 3 disposed on the microstrip substrate 1, and a conversion structure 4. The conversion structure 4 includes a coaxial connector 41 connected to the signal transmission microstrip line 2 and the signal receiving microstrip line 3, and a metal cavity 42 disposed outside the coaxial connector 41.

[0037] In this embodiment, since microstrip lines with different linewidths have different characteristic impedances, direct connection will cause 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 path, it can obtain better shielding effect and anti-interference capability. At the output end, the coaxial signal is converted back into microstrip form for smooth transmission to the subsequent circuit.

[0038] Specifically, this invention optimizes the simulation by using the calculation and electromagnetic simulation software HFSS to adjust the width and length of the microstrip line, the radius of the coaxial connector 41, and optimize the shape of the microstrip line, the volume of the metal cavity 42, and the connection position. It also examines 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 is minimized throughout the conversion process, thereby improving the overall signal transmission efficiency.

[0039] Specifically, the microstrip substrate 1 is a double-sided copper-clad dielectric substrate. 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 substrate, or on the top and bottom layers of the dielectric substrate, 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. Its cavity height is preferably 3 mm, and its aspect ratio is 3:1 (to suppress higher-order modes).

[0040] Optionally, the coaxial connector 41 can be an SMA or BNC connector, and the characteristic impedance of the coaxial and microstrip is the same, 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 a portion of the inner conductor 412. The inner conductor 412, which is close to the signal transmission microstrip line 2, is located inside the metal cavity 42. Both ends of the coaxial cylinder 411 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 portion of the coaxial cylinder 411 that extends out of 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 the gap between the outer conductor 413 and the inner conductor 412 is filled with a dielectric.

[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 grounded to the ground plane, providing electromagnetic shielding and achieving better shielding and anti-interference performance. Simultaneously, an outer shielding layer is provided between the coaxial cylinder 411 and the inner conductor 412. The surface of the outer conductor 413 is coated with this outer shielding layer to fix the coaxial cylinder 411 and isolate the inner and outer conductors. The outer shielding layer is made of polytetrafluoroethylene (PTFE), 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 cavity wall of the metal cavity 42, forming capacitive coupling.

[0043] Conditions for suppressing higher-order modes in metal cavity 42:

[0044]

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

[0046] Specifically, when using HFSS simulation optimization, key modeling settings include boundary conditions, excitation ports, and mesh generation. Boundary conditions include the metal cavity 42 and the substrate. The substrate's conductivity σ = 5.8 × 10^7 S / m. The excitation port covers the coaxial cross-section plus a microstrip line extension of 3 times the linewidth. In mesh generation, the frequency is 40 GHz, and the accuracy is λ / 20 → mesh size 0.375 mm. Additionally, simulation optimization requires setting parameter scanning strategies, including coaxial radius optimization, transition line shape comparison, and the influence of the metal cavity 42 height. Coaxial radius optimization requires scanning the diameter d of the coaxial cylinder 411 (0.6-1.0 mm) with a step size of 0.1 mm, observing the minimum S11 point. The target position is S11 < -20 dB in the 30 GHz scenario. Adjusting the cavity height h = 2-5 mm, analyzing the Q value (capacitance and inductance) and resonant point offset, 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 = 1.0 mm -12.3dB -0.82dB <![CDATA[0.67V 2 / m 2 ]]>

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

[0049] In some embodiments, the conversion structure 4 further includes a rectangular metal block 43, which includes a first rectangular block 431 and a second rectangular block 432 disposed to the right of the first rectangular block 431. The first rectangular block 431 has a metal cavity 42 on one end face near the signal transmission microstrip line 2, and the metal cavity 42 penetrates 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, in this embodiment, the rectangular metal block 43 is made of aluminum alloy, its surface is silver-plated, and its surface roughness Ra < 0.8μm. The metal cavity 42 and the inner conductor 412 are bonded with conductive adhesive, and the gap between them is laser-positioned and welded, with a gap uniformity error of 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, the segmented design of the stepped metal block enables multi-band impedance changes, such as 50Ω→75Ω→50Ω. In addition, the stepped structure of the metal block enhances assembly rigidity and reduces contact impedance fluctuations caused by high-frequency vibration. A controllable capacitor is formed between the metal cavity 42 and the gap between it and the inner conductor 412 to compensate for the difference in dielectric constant between the microstrip line and the coaxial structure. Furthermore, the first rectangular block 431 and the outer conductor 413 are connected by an RF spring contact with a contact pressure of 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, and the high-frequency capacitive reactance is compensated by adjusting d.

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

[0056] Specifically, the metal cavity 42 and the gap formed between it and the inner conductor 412 are smaller than the skin depth, i.e., δ≈1.26μm (in the case of a frequency of 10GHz), to avoid high-frequency current leakage; the inner conductor 412 can be gold-plated on the surface, with a thickness greater than 2μm, to reduce conductor loss.

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

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

[0059] Second depth Match the wavelength of the medium.

[0060] Specifically, performance simulations and field tests were conducted on the 28GHz band using the parameters described above. The simulation results are as follows:

[0061] parameter Stepless structure Stepped optimization structure Return loss (S11) -12dB -23dB Insertion loss (S12) 0.45dB 0.18dB Phase consistency ±15℃ ±5℃

[0062] In the actual test comparison, the calibration method of the vector network analyzer (Keysight N5245B (10MHz-50GHz)) was adopted: TRL calibration to eliminate fixture error. The results are as follows: the bandwidth is extended, the -15dB return loss bandwidth is increased from 5GHz (traditional structure) to 12GHz (stepped structure), and the power capacity withstands power >10W (in the scenario of 30GHz frequency) without arc breakdown.

[0063] As a modified embodiment, such as Figure 2As shown, curved transition sections 414 are respectively provided on the front and rear end faces of the rectangular metal block 43. The curved transition sections 414 extend from the middle part 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 sections 414 are formed by the end face of the first rectangular block 431 protruding in a direction away from the axis of the inner conductor 412 and the end face of the second rectangular block 432 being recessed in a direction close to the axis of the inner conductor 412, and the curvature of the curved transition sections 414 gradually decreases.

[0064] In this embodiment, the right-angled steps of the first and second rectangular blocks are replaced with a gradual transition of curved ramps. The transition zone changes smoothly according to an exponential curve, and the curvature gradually decreases, which makes the impedance matching more continuous. This setting can make the ultra-wideband performance excellent and the reflection extremely small.

[0065] Specifically, the length of the transition section of the curve (L) taper The electrical length of the gradient region is determined, typically taken as 0.1λ-0.25λ (λ is the wavelength of the center frequency of the target frequency band). For example, in the 30GHz band (λ=10mm), L is chosen. taper = 2.5mm (0.25λ); the exponentially varying curvature is given by the equation y(x) = D1 + (D2 - D1) * (1 - e -kx The control is k, which is the attenuation coefficient, where D1 and D2 are the depth values ​​of the first and second rectangular blocks, 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, in the simulation analysis, taking 40GHz ultra-wideband as an example, the parameter L is set... taper =5mm, k=0.4, ΔD(D2-D1)=2mm, thus obtaining the simulation results: S11<-30dB, S21 loss is only 0.1dB. It can be seen that the setting of this structure can significantly improve the broadband performance of microstrip-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, while the outer diameter is adapted to the outer conductor 413. A gap is provided between the matching ring 6, the outer conductor 413, and the rectangular metal block 43. The bottom of the matching ring 6 is disposed on the microstrip substrate 1 through a ring base 7.

[0068] In this embodiment, setting a matching ring between the rectangular metal block and the outer conductor can 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 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 provided at the edges of the front and rear end faces of the second rectangular block 432, and each of the rectangular grooves 433 is provided in a one-to-one correspondence at the front and rear positions.

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

[0072] Specifically, the length (L) of the aforementioned rectangular groove slot The width of the rectangular slot is typically λ / 8-λ / 4 (λ is the target frequency wavelength). For example, in the 30GHz band, λ = 10mm, and the length is approximately 1.25-2.5mm. slot The depth of the groove (D) is typically 0.1-0.5 mm. slot The diameter is approximately 0.2-1mm; each slot can be considered as a parallel capacitor, with an approximate capacitance value of:

[0073]

[0074] Optionally, the rectangular groove can be replaced with a U-shaped groove to enhance edge field coupling, or with a periodic toothed groove to continuously transmit surface waves of a specific frequency band through a periodic structure, or with an arc-shaped groove to smooth the electric field transition and reduce radiation loss.

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

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

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

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

[0079] Specifically, this invention, through the collaborative design of a stepped metal block and a metal cavity 42, significantly outperforms traditional solutions in terms of broadband matching and mechanical stability, making it particularly suitable for high-frequency, high-reliability scenarios, such as millimeter-wave radar front-ends: used for low-loss interconnection between T / R modules and antenna array elements; inter-satellite links: reliable connections that can withstand extreme temperatures (-180℃ to +150℃) and vacuum environments; 6G terahertz communication: combined with photonic crystal structures, extending the operating frequency band to 300GHz.

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

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

[0082] Specifically, the top width of the trapezoidal base 5 is smaller than the bottom width, forming a gradual impedance transition. An arc-shaped groove 51 is opened at the top, and its radius of curvature matches the diameter of the coaxial cylinder 411. For example, a 1mm diameter cylinder corresponds to a groove with R=0.5mm, ensuring maximum contact area. After the cylindrical conductor is embedded in the arc-shaped groove 51, it is filled with low-temperature solder, such as Sn63Pb37, to form electrical connection and mechanical fixation. The solder coverage area is controlled within the length of the arc-shaped groove 51, typically 3-5 times the cylinder diameter, to avoid overflow affecting the surrounding area.

[0083] Specifically, during the design process, impedance continuity needs to be considered, including using trapezoidal base 5 as a microstrip line width gradient section to achieve a smooth impedance transition:

[0084]

[0085] Where Δw is the change in width of 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, and must satisfy:

[0087]

[0088] Where f is the highest operating frequency.

[0089] Specifically, the trapezoidal base 5 is made of a microstrip substrate 1CTE matched with a copper-tungsten alloy base, for example, a Rogers RO4350B substrate. This trapezoidal base 5 is micromilled or laser-etched, with a sidewall perpendicularity of <1° and a surface roughness Ra of <0.4μm. The depth of the arc-shaped groove is greater than 1.2 times the radius of the coaxial cylinder 411; for example, a 1mm radius paired with a 1.2mm groove depth prevents detachment. Its processing error is ±0.01mm, requiring calibration with a three-dimensional measuring instrument. The solder is a flexible alloy, such as In97Ag3, which can withstand cycles from -55℃ to 125℃, with a fill rate greater than 90%. Microporous capillary penetration technology is used to enhance adhesion, and a micro-dispensing machine is used to quantitatively inject the solder paste with an accuracy of ±0.01mm. 3 The reflow soldering temperature profile peaks at 245℃±3℃, with a time of 8-10 seconds. The solder surface is streamlined and shaped with an edge thickness of <0.1mm to reduce edge field distortion.

[0090] Specifically, when designing the dimensions of each component of the trapezoidal base 5, refer to the following calculation formula:

[0091] Trapezoidal seat 5, length L: In particular, the length is preferably 4.3 mm and the dielectric constant is preferably 4.3 when used in 10 GHz applications;

[0092] The radius of curvature R of the arc-shaped groove 51 is R = 0.5D. conductor For 10GHz applications, D=1mm and R=0.5mm are preferred.

[0093] Solder volume V: V = πR 2 L fill For 10GHz applications, the preferred dimensions are R = 0.5mm, L = 3mm, and the volume is V = 2.36mm². 3 .

[0094] In some embodiments, the bottom of the trapezoidal base 5 is provided with a plurality of through holes 52, which are arranged in an array and extend along the height direction of the trapezoidal base 5.

[0095] In this embodiment, through holes 52 are opened on the trapezoidal base 5 to suppress surface waves. Preferably, a grounding via array is provided, and the calculation formula for the hole spacing is as follows: In particular, the hole spacing is preferably 2.1 mm when applied at 10 GHz.

[0096] Specifically, the trapezoidal base 5 structure was simulated using HFSS. Five parametric variables were defined for the trapezoidal base, with scans of L: 3-6mm and R: 0.4-0.6mm. S11 was optimized, and the solder material property σ = 2 × 10⁻⁶ was added. 6After optimization, if the 10GHz scenario is selected, S11 = -27dB and S21 = 0.08dB; if the 30GHz scenario is selected, S11 = -18dB and S21 = 0.22dB.

[0097] The results above show 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, the trapezoidal base 5 has opening lines on both the front and rear end faces.

[0099] In this embodiment, an open circuit is provided on the trapezoidal base 5 to suppress high-frequency resonance.

[0100] In some embodiments, the signal transmission microstrip line 2 and the signal receiving microstrip line 3 are each provided with multiple cascaded impedance transformers 8 on the side near the conversion structure, and the radius of each impedance transformer 8 gradually increases from the side of the signal transmission microstrip line 2 or the signal receiving microstrip line 3 toward the conversion structure 4, and the connection of each impedance transformer 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 over a wide frequency band.

[0102] Specifically, the characteristic impedance of each impedance transformer section needs to meet the following requirements: Furthermore, the converter typically uses 2-5 sections, preferably 3 sections (2 sections are used as an example in the figure), with each section having a length of approximately 1.8 mm and a dielectric constant of 3.5 mm. When using HFSS modeling for optimization, the optimization target is an in-band ripple (S11 fluctuation) < 0.5 dB and an operating bandwidth (S11 < -20 dB) ≥ 2:1. The parameters are designed as follows: 3-section Chebyshev converter, with characteristic impedances of each section being Z1 = 56.6 Ω, Z2 = 65.8 Ω, and Z3 = 75 Ω, and a substrate of FR4 (dielectric constant 4.4). The resulting optimization is: S11 < -22 dB and S21 loss < 0.25 dB. It can be seen that this structure can achieve low-loss transmission in microstrip-to-coaxial conversion.

[0103] The working principle of the microstrip to microstrip conversion device using coaxial cable in this application is as follows: The radio frequency signal is converted from a microstrip signal to a coaxial signal via the conversion structure 4. The signal achieves better shielding and anti-interference capabilities when propagating within the coaxial cable. At the output end, the coaxial signal is converted back to microstrip form for smooth transmission to subsequent circuits. A coaxial cylinder 411 serves as a transition structure for signal transmission between two microstrip lines. The inner conductor 412 maintains electrical isolation, while the metal cavity 42 reduces dielectric loss. An outer conductor 413 is placed outside the inner conductor 412, with the gap between them filled with dielectric material, forming a coaxial structure that not only acts as a bridge but also… The outer conductor 413 serves as electromagnetic shielding. In addition, the stepped rectangular metal block optimizes impedance matching, reduces reflection, and improves high-frequency performance. Replacing the right-angled steps of the rectangular metal block with a gradual transition of curved ramps, with the transition region changing smoothly according to an exponential curve and the curvature gradually decreasing, makes the impedance matching more continuous. Multiple slots at the edge of this transition region can adjust the active control of parasitic capacitance and optimize high-frequency impedance matching. At the same time, setting a matching ring between the rectangular metal block and the outer conductor can 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 abrupt changes and improve signal transmission efficiency.

[0104] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A microstrip to microstrip conversion device via coaxial connection, characterized in that: The application relates to a microstrip substrate (1), a signal transmission microstrip line (2) arranged on the microstrip substrate (1), a signal receiving microstrip line (3) and a conversion structure (4), wherein the conversion structure (4) comprises a coaxial connector (41) connected with the signal transmission microstrip line (2) and the signal receiving microstrip line (3) and a metal cavity (42) arranged outside the coaxial connector (41); 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 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), both ends of the coaxial cylinder (411) penetrate the inner conductor (412) and are connected with the signal transmission microstrip line (2) and the signal receiving microstrip line (3) respectively, and the part of the coaxial cylinder (411) penetrating the inner conductor (412) is arranged outside the metal cavity (42); the outer conductor (413) is arranged on the side close to the signal receiving microstrip line (3), and the gap between the outer conductor (413) and the inner conductor (412) is filled with a medium; the conversion structure (4) further comprises a rectangular metal block (43), the rectangular metal block (43) comprises a first rectangular block (431) and a second rectangular block (432) arranged on the right side of the first rectangular block (431); a side end face of the first rectangular block (431) close to the signal transmission microstrip line (2) is provided with the metal cavity (42), and the metal cavity (42) penetrates the bottom end face of the first rectangular block (431); the length of the second rectangular block (432) is greater than that of the first rectangular block (431), and the right side end face of the second rectangular block (432) is connected with the outer conductor (413); curve transition sections (414) are arranged at the front and back side end faces of the rectangular metal block (43) respectively, the curve transition sections (414) extend from the middle part of the end face of the first rectangular block (431) to the right side edge position of the end face of the second rectangular block (432), the curve transition sections (414) are formed by the end face of the first rectangular block (431) being convex 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 curve transition sections (414) gradually decreases; a matching ring (6) is arranged 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, the inner diameter of the matching ring (6) is matched with the inner conductor (412), and the outer diameter of the matching ring (6) is matched with the outer conductor (413).The matching ring (6) is provided with a spacing between 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).

2. The device for converting microstrip to microstrip by means of a coaxial line according to claim 1, characterized in that: The edges of the front and back end faces of the second rectangular block (432) are provided with rectangular grooves (433), and each of the rectangular grooves (433) is arranged in one-to-one correspondence in front and back positions.

3. The device for converting microstrip to microstrip by means of a coaxial line according to claim 1, characterized in that: The bottom edge of the metal cavity (42) is formed with a round corner (44), and the shape of the metal cavity (42) is arc-shaped.

4. The device for converting microstrip to microstrip by means of a coaxial line according to claim 1, characterized in that: The microstrip substrate (1) is further provided with two trapezoidal seats (5), the bottoms of the two trapezoidal seats (5) are respectively soldered with the signal transmission microstrip line (2) and the signal receiving microstrip line (3), the upper end face of the trapezoidal seat (5) is downwardly recessed to form an arc-shaped groove (51), and the coaxial cylinder (411) is arranged in the arc-shaped groove (51).

5. The device for converting microstrip to microstrip through a coaxial line according to claim 4, characterized in that: The bottom of the trapezoidal seat (5) is provided with a plurality of through holes (52), each of the through holes (52) is arranged in an array, and the through holes (52) extend along the height direction of the trapezoidal seat (5).

6. The device for converting microstrip to microstrip by means of a coaxial line according to claim 1 or 4, characterized in that: The signal transmission microstrip line (2) and the signal receiving microstrip line (3) are provided with a plurality of cascaded impedance transformers (8) on the side close to the conversion structure (4), the radius of each impedance transformer (8) gradually increases from the signal transmission microstrip line (2) or the signal receiving microstrip line (3) side to the conversion structure (4) side, and the connection of each impedance transformer (8) is provided with a chamfer.

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