Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure

Abstract

The invention provides a Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure, which comprises a structural cavity, a microstrip line connected in the structural cavity, a dielectric substrate, a rectangular waveguide arranged below the structural cavity, and a pin which is vertically connected with the microstrip line and vertically penetrates through the dielectric substrate to extend into the rectangular waveguide, the upper metal ring surrounds the periphery of the top of the contact pin, the metalized through holes uniformly connect the upper metal ring with a lower metal plate of the dielectric substrate, the sleeve and the air cavity are connected between the dielectric substrate and the rectangular waveguide and sequentially wrap the contact pin, the sleeve is connected to the bottom of the dielectric substrate, and the air cavity is connected to the top of the rectangular waveguide. Compared with a traditional microstrip-coaxial-waveguide transition structure, a quasi-coaxial-coaxial coplanar compensation transition structure is adopted, the metalized through holes are introduced around the contact pin bonding pad, field leakage and reflection loss are reduced, transmission efficiency is improved, the capacitance effect is compensated through the high-resistance transmission line, reflection is eliminated, transmission loss is reduced, and transmission efficiency is improved. And the transmission bandwidth is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical components, and in particular to a Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure. Background Art

[0002] In microwave and millimeter wave integrated circuits, microstrip lines, coaxial lines, and waveguides are common signal transmission lines. Existing high-power, low-loss microwave and millimeter wave circuits are often cascaded using rectangular waveguides. With the development of circuit printing technology, microstrip circuits can achieve very high circuit quality, and most of the circuits currently used are of this type. Therefore, how to achieve a broadband, low-loss transition from microstrip to waveguide is currently a focus of microwave circuit research. Existing waveguide-microstrip transition types include microstrip probe-waveguide conversion structure, microstrip-ridge waveguide conversion structure, microstrip-fin line-waveguide conversion structure, and microstrip-coaxial line-waveguide conversion structure. Among them, the microstrip-coaxial-waveguide conversion structure has serious electromagnetic field leakage problems during signal transmission, resulting in the disadvantages of high loss and narrow bandwidth of this structure. Summary of the Invention

[0003] The present invention aims to solve the loss problem of the transition structure and provides a low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide. It adopts a coplanar compensation transition structure similar to coaxial-coaxial. Compared with the traditional microstrip-coaxial-waveguide transition structure, the present invention introduces metallized through-holes around the pin pads to reduce field leakage, reduce reflection loss, and improve transmission efficiency. The capacitance effect is compensated and reflection is eliminated through the high-resistance transmission line, thereby reducing transmission loss and increasing transmission bandwidth.

[0004] The present invention provides a Ku-band microstrip-to-coaxial-to-waveguide low-loss vertical transition structure, comprising a structural cavity, a microstrip line and a dielectric substrate sequentially connected to the structural cavity from top to bottom, a rectangular waveguide disposed below the structural cavity, a pin vertically connected to the microstrip line and vertically passing through the dielectric substrate and extending into the rectangular waveguide, an upper metal ring surrounding the top of the pin, a metallized through-hole uniformly connecting the upper metal ring to the lower metal plate of the dielectric substrate, a sleeve connected between the dielectric substrate and the rectangular waveguide and sequentially wrapped around the outside of the pin, and an air cavity, wherein the sleeve is connected to the bottom of the dielectric substrate, and the air cavity is connected to the top of the rectangular waveguide.

[0005] The pins are composed of a first section of pins connected to the dielectric substrate, a second section of pins connected to the sleeve, and a third section of pins connected to the air cavity.

[0006] The first section of pins, metallized through-holes and dielectric substrate constitute the first section of quasi-coaxial line; the sleeve, the second section of pins and the metal structural cavity outside the sleeve constitute the second section of coaxial line; the third section of pins, the air in the air cavity and the metal structural cavity outside the air cavity constitute the third section of coaxial line quasi-air coaxial line.

[0007] The low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide described in the present invention is preferably configured such that the insertion loss of the low-loss vertical transition structure can be changed by changing the distance from the metallized through-hole to the pin, the length of the pin inserted into the rectangular waveguide, the sleeve diameter and length, and the diameter and length of the air cavity.

[0008] In the Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure described in the present invention, as a preferred embodiment, the signal mode transmitted by the microstrip line is a quasi-TEM mode, and the signal mode transmitted by the first coaxial-like section, the second coaxial-like section, and the third coaxial-like section is a TEM mode.

[0009] The signal is transmitted from the microstrip line to the pin, and then transmitted to the rectangular waveguide through the first coaxial line, the second coaxial line and the third coaxial line air coaxial line in sequence. The exposed pins in the rectangular waveguide radiate electromagnetic energy and realize the transition from TEM mode to TE10 mode through coupling.

[0010] In the Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure described in the present invention, as a preferred embodiment, the jump capacitors of the first coaxial-like section, the second coaxial-like section, and the third coaxial-like air coaxial section are all:

[0011] C=2πf(r1)+2πf(R1);

[0012] Where r1 is the inner conductor size jump value, f(r1) is the function of r1, R1 is the outer conductor size jump value, f(R1) is the function of R1.

[0013] In the Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure described in the present invention, as a preferred embodiment, r1 is the radius of the pin, and R1 is the radius of the sleeve or the radius of the air cavity.

[0014] In the Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure described in the present invention, the sleeve is preferably a polytetrafluoroethylene sleeve;

[0015] The pin is inserted into the rectangular waveguide perpendicular to the wide wall of the rectangular waveguide;

[0016] The sleeve diameter is greater than the diameter of the air cavity, and the sleeve length is greater than the length of the air cavity.

[0017] In the low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide described in the present invention, as a preferred embodiment, the sleeve is made of polytetrafluoroethylene and the pin passes through the center of the sleeve.

[0018] The low-loss vertical transition structure of the Ku-band microstrip-coaxial-waveguide described in the present invention preferably has metallized through-holes evenly arranged around the pins. The metallized through-holes can suppress the parasitic transmission mode between the upper metal ring and the lower metal plate, thereby reducing insertion loss.

[0019] Adjusting the distance between the pin and the inner wall of the rectangular waveguide can reduce the return loss.

[0020] The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure described in the present invention preferably further includes an SMA connector connected to the microstrip line and located outside the structural cavity.

[0021] The present invention uses a quasi-coaxial-coaxial pin to connect the upper microstrip line and the lower waveguide, and can be used as a microwave radio frequency circuit component.

[0022] The present invention has the following advantages:

[0023] The present invention adopts a coaxial-coaxial coplanar compensation transition structure. Compared with the traditional microstrip-coaxial-waveguide transition structure, it introduces metallized through-holes around the pin pads to reduce field leakage, reduce reflection loss, and improve transmission efficiency. The capacitance effect is compensated and reflection is eliminated through the high-resistance transmission line, thereby reducing transmission loss and increasing transmission bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A three-dimensional schematic diagram of a low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide;

[0025] Figure 2 A schematic diagram of a microstrip-coaxial transition structure with a low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide;

[0026] Figure 3 Schematic diagram of a coaxial-waveguide transition structure with a low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide.

[0027] Reference numerals:

[0028] 1. Structural cavity; 2. Microstrip line; 3. Dielectric substrate; 4. Rectangular waveguide; 5. Pin; 6. Upper metal ring; 7. Metallized through hole; 8. Sleeve; 9. Air cavity; 10. SMA connector. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] Example 1

[0031] like Figures 1 to 3 As shown, a low-loss vertical transition structure of Ku-band microstrip-coaxial-waveguide consists of a structural cavity 1, a microstrip line 2, a dielectric substrate 3, a waveguide cavity 4, a metal pin 5, an upper metal ring 6, a metalized through-hole 7, a polytetrafluoroethylene sleeve 8, an air cavity 9 and an SMA connector 10.

[0032] The metal pins 5 extend perpendicularly from the dielectric substrate 3, with a circle of plated through-holes 7 surrounding the pins' pads. The metal pins 5, attached to the bottom surface of the dielectric substrate 3, are wrapped in a Teflon sleeve 8 and inserted perpendicularly into the waveguide through a small air cavity 9. The coaxial line can be divided into three sections. The metal pins 5 (the first section of pins), the plated through-holes 7, and the dielectric substrate 3 in the dielectric substrate 3 form the first quasi-coaxial section. The Teflon sleeve 8, the metal pins 5 (the second section of pins), and the metal structural cavity below the dielectric substrate 3 form the second coaxial section. The metal structural cavity, air, and the metal pins 5 (the third section of pins) above the waveguide 4 form the third coaxial section, a quasi-air coaxial section.

[0033] In the first section of the quasi-coaxial line, the metallized through-hole 7 introduced around the pad of the pin 5 can connect the lower metal plate of the dielectric substrate 3 and the upper metal ring 6, thereby suppressing the parasitic transmission mode between the metal ring 6 and the metal plate. In addition, the magnetic wall composed of this quasi-coaxial structure can suppress the leakage of the electromagnetic field and reduce the radiation loss during the transmission process.

[0034] The principle behind this scheme is that the signal mode transmitted by the microstrip line 2 is a quasi-TEM mode, while the signal mode transmitted by the coaxial line is a TEM mode, resulting in a good match in physical properties between the two. The vertical transition from microstrip to coaxial line begins by connecting the top microstrip line 2 to a metal pin 5. This is then inserted into the waveguide 4 via three coaxial sections. The exposed pins 5 radiate electromagnetic energy, enabling the transition from the TEM mode to the TE10 mode through coupling.

[0035] When the size of the inner and outer conductors of the coaxial line changes, a jump capacitance will be introduced. The value of this jump capacitance is related to the conductor radius, as shown in the following formula:

[0036] C=2πf(r1)+2πf(R1)

[0037] Wherein, C represents the jump capacitance value, r1 represents the jump value of the inner conductor size, and R1 represents the jump value of the outer conductor size. The inner conductor of the three-section coaxial line is a metal pin 5, whose size does not change. The impedance matching is achieved by changing the size and material of the outer conductor. Therefore, the jump capacitance value of the coaxial line is only related to the change in the size of the outer conductor. In order to suppress the reflection caused by the jump capacitance, the measure taken by the present invention is to optimize the outer conductor radius between different coaxial lines to form a high-impedance transmission line. This section of high-impedance transmission line can be equivalent to a π-type network consisting of two capacitors and one inductor, thereby compensating for the jump capacitance and reducing the insertion loss caused by impedance mismatch.

[0038] like Figures 1 to 3 As shown, a microstrip-to-coaxial-to-waveguide vertical transition simulation model was established using the 3D electromagnetic field simulation software HFSS11.0. Electrical performance simulations were performed. By optimizing the distance from the metallized via 7 to the pin 5, the length of the pin 5, the Teflon sleeve 8, the diameter and length of the air cavity 9, and the distance between the pin 5 and the internal structural wall of the rectangular waveguide 4, excellent electrical performance indicators for the broadband microstrip-to-coaxial-to-waveguide transition were achieved. Simulation results show that within the frequency range of 13 GHz to 16 GHz, the insertion loss is less than 0.1 dB, and the return loss is better than -20 dB, both exceeding those of traditional microstrip-to-coaxial-to-waveguide transition structures. Based on these simulation results, the patterned structure of cavity 1, dielectric substrate 3, rectangular waveguide 4, metal pin 5, and Teflon sleeve 8 was derived.

[0039] The probe of the SMA connector 10 is soldered to the microstrip line 2 of the dielectric substrate 3. The metal pin 5 extends from the dielectric substrate 3 into the waveguide cavity 4. The dielectric substrate 3 is designed with a circle of metallized through-holes 7 connecting the metal ring 6 above and the grounded metal surface below. The metal pin 5 is wrapped by a polytetrafluoroethylene sleeve 8 and an air cavity 9 in the middle section between the dielectric substrate 3 and the rectangular waveguide 4, thereby realizing the transition from microstrip to coaxial line to waveguide.

[0040] In this embodiment, the thickness of the dielectric substrate 3 and the height of the metallized through hole 7 are both 0.6 mm, the height of the polytetrafluoroethylene sleeve 8 is 2 mm, the height of the air cavity 9 is 0.5 mm, and the length of the metal pin 5 extending into the waveguide cavity 4 is 4 mm.

[0041] According to the above implementation, a high-efficiency, low-loss broadband microstrip-coaxial-waveguide vertical transition structure is assembled and can be used for engineering testing.

[0042] It can successfully and efficiently complete low-loss and high-efficiency transmission of Ku-band signals.

[0043] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A Ku-band microstrip-to-coaxial-to-waveguide low-loss vertical transition structure, characterized by: The invention comprises a structural cavity (1), a microstrip line (2) and a dielectric substrate (3) connected in sequence in the structural cavity (1) from top to bottom, a rectangular waveguide (4) arranged below the structural cavity (1), a pin (5) vertically connected to the microstrip line (2) and vertically passing through the dielectric substrate (3) and extending into the rectangular waveguide (4), an upper metal ring (6) surrounding the top of the pin (5), a metallized through hole (7) uniformly connecting the upper metal ring (6) to the lower metal plate of the dielectric substrate (3), a sleeve (8) connected between the dielectric substrate (3) and the rectangular waveguide (4) and sequentially wrapped around the outside of the pin (5), and an air cavity (9), wherein the sleeve (8) is connected to the bottom of the dielectric substrate (3), and the air cavity (9) is connected to the top of the rectangular waveguide (4); The pins (5) are composed of a first section of pins connected to the dielectric substrate (3), a second section of pins connected to the sleeve (8), and a third section of pins connected to the air cavity (9); The first section of the plug pins, the metallized through-holes (7) and the dielectric substrate (3) constitute a first section of the quasi-coaxial line; the sleeve (8), the second section of the plug pins and the metal structural cavity outside the sleeve (8) constitute a second section of the coaxial line; the third section of the plug pins, the air in the air cavity (9) and the metal structural cavity outside the air cavity (9) constitute a third section of the coaxial line quasi-air coaxial line.

2. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The insertion loss of the low-loss vertical transition structure can be changed by changing the distance from the metallized through-hole (7) to the pin (5), the length of the pin (5) inserted into the rectangular waveguide (4), the diameter and length of the sleeve (8), and the diameter and length of the air cavity (9).

3. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The signal mode transmitted by the microstrip line (2) is a quasi-TEM mode, and the signal mode transmitted by the first section of quasi-coaxial line, the second section of coaxial line, and the third section of coaxial line quasi-air coaxial line is a TEM mode; The signal is transmitted from the microstrip line (2) to the pin (5), and then sequentially transmitted through the first section of quasi-coaxial line, the second section of coaxial line, and the third section of coaxial line quasi-air coaxial line to the rectangular waveguide (4). The exposed pin (5) in the rectangular waveguide (4) radiates electromagnetic energy and realizes the transition from TEM mode to TE10 mode through coupling.

4. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The jump capacitances of the first section of quasi-coaxial line, the second section of coaxial line, and the third section of coaxial line quasi-air coaxial line are all: C=2πf(r1)+2πf(R1); Where r1 is the inner conductor size jump value, f(r1) is the function of r1, R1 is the outer conductor size jump value, f(R1) is the function of R1.

5. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 4, characterized in that: r1 is the radius of the pin (5), and R1 is the radius of the sleeve (8) or the radius of the air cavity (9).

6. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The sleeve (8) is a polytetrafluoroethylene sleeve; The pin (5) is inserted into the interior of the rectangular waveguide (4) perpendicularly to the wide wall of the rectangular waveguide (4); The diameter of the sleeve (8) is greater than the diameter of the air cavity (9), and the length of the sleeve (8) is greater than the length of the air cavity (9).

7. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The bandwidth of the transmission signal can be widened by adjusting the shape of the microstrip line (2).

8. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The material of the sleeve (8) is polytetrafluoroethylene, and the pin (5) passes through the center of the sleeve (8).

9. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: The metallized through holes (7) are evenly arranged around the pins (5), and the metallized through holes (7) can suppress the parasitic transmission mode between the upper metal ring (6) and the lower metal plate, thereby reducing insertion loss; Adjusting the distance between the pin (5) and the internal structural wall of the rectangular waveguide (4) can reduce the return loss.

10. The Ku-band microstrip-coaxial-waveguide low-loss vertical transition structure according to claim 1, characterized in that: It also includes an SMA connector (10) connected to the microstrip line (2) and located outside the structural cavity (1).

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