A mixer based on a substrate integrated fin-line structure

Abstract

The application discloses a kind of mixers based on substrate integrated fin line structure, belong to radio frequency technical field.The mixer based on substrate integrated fin line structure described in the application has the advantages such as low manufacturing cost, simple manufacturing method, can form self-encapsulated whole, freely replace design module etc.;It is realized by multilayer dielectric substrate laminated compression, has lower loss, weak dispersion, simple structure, small size, low cost, can realize self-encapsulation and easily integrated with other radio frequency circuits etc.Advantages.Compared with the existing fin line structure using multilayer dielectric substrate, the application solves the problem that various devices and functional modules are loaded on the fin line, and makes the modules of device can be flexibly replaced, expands the function realized by substrate integrated fin line, increases application scenario;Three-dimensional functional structure becomes two-dimensional functional structure, which is conducive to directly designing fin line functional area in integrated circuit, so that circuit and substrate integrated fin line can be effectively combined.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency technology, and specifically relates to a mixer based on a substrate integrated fin structure. Background Technology

[0002] With the development of microwave technology and millimeter-wave circuits, multilayer board circuit technology has rapidly developed to achieve miniaturization of circuit structures and high integration of radio frequency circuits, and has been widely researched and applied in various communication devices. Multilayer board circuits can integrate active and passive circuits and enable the miniaturization of communication system equipment. In general microstrip fin transition structures, a metal waveguide is required, and the microstrip fin transition structure needs to be fixed to the waveguide center perpendicular to the H-plane. This traditional transition structure is costly, difficult to install, and not conducive to integration with active devices. In transmission line structures, the fin is a quasi-planar structure embedded in the E-plane of a rectangular waveguide. The fin's propagation mode is a mixed mode, characterized by low loss, weak dispersion, and large single-mode bandwidth. On the other hand, the transmission cutoff frequency of the fin structure is lower than that of the encapsulated waveguide, so the required size is smaller than that of traditional waveguides while retaining some of the advantages of waveguides. However, the fin requires the fabrication of a mechanical cavity for enclosure, and grooves need to be left to install the fin to meet mechanical support and electromagnetic shielding requirements. Therefore, additional assembly work is required to mechanically assemble it with the waveguide before it can function. Today, microwave components require a high degree of integration. Fin structures within waveguides are difficult to integrate with other active components, and their transmitted electromagnetic waves are also difficult to control. Traditional fin structures have large metal cavities, and their size remains substantial after integration with circuit boards, making miniaturization of RF components difficult. Existing fin structures require mounting in rectangular waveguides, which is difficult to fabricate, has high manufacturing costs, and is not easily integrated with other circuits and electronic components.

[0003] Existing technology discloses a method for constructing fin structures in a multilayer dielectric substrate stacked structure using discontinuous vias, demonstrating the feasibility of using multilayer dielectric substrates to construct fins. However, this structure only features fins as a transmission structure, and the possibility of converting other transmission forms to fin structures in a multilayer dielectric substrate has not been verified, leaving the question of its applicability to circuit systems unresolved. Furthermore, because it uses discontinuous vias as signal transmission constraints, the processing precision of the multilayer board needs to be sufficiently high to ensure that all corresponding vias are aligned to avoid affecting transmission performance. This, compared to traditional metal devices, cannot effectively reduce the assembly difficulty and precision processing cost of this structure. Moreover, the signal ports in this structure still use standard metal waveguides, perpendicular to the circuit plane. This defect prevents the fin structure constructed from multilayer dielectric substrates from being integrated into the circuit, requiring vertical signal ports and creating significant space utilization issues. Finally, because the structure uses a non-cut-out dielectric substrate, various devices and functional modules, such as diodes, cannot be mounted in the fin structure, and the various module components cannot be flexibly replaced according to design needs, significantly reducing the functionalities achievable by this fin structure. In summary, the existing structure cannot simultaneously meet the requirements of low assembly cost, low precision, wide range of application scenarios, and efficient integration with circuits. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a mixer based on a substrate-integrated fin structure. This mixer can realize the formation of a mixer structure from microstrip to fin to suspension strip by riveting multilayer circuit boards, solving the technical problems of existing fin structures requiring the processing of mechanical cavities and additional manual assembly, as well as the integration of fin structures with other planar circuits.

[0005] The technical problem addressed by this invention is solved as follows:

[0006] A mixer based on a substrate integrated fin structure includes a mixer circuit structure as the main body; the mixer circuit structure includes a multilayer circuit board, each circuit board including a dielectric substrate and metal layers printed on the upper and lower surfaces of the dielectric substrate.

[0007] The mixer circuit structure is a planar three-port circuit, and the multilayer circuit board includes a first circuit board, a second circuit board, a third circuit board, a fourth circuit board, and a fifth circuit board that are tightly attached to each other from top to bottom;

[0008] Each circuit board has a metal strip-shaped straight via and two metal strip-shaped L-shaped vias on its upper and lower surfaces, which are parallel to the long side of the dielectric substrate. One branch of the metal strip-shaped L-shaped via is parallel to the metal strip-shaped straight via, while the other branch of the metal strip-shaped L-shaped via extends away from the metal strip-shaped straight via. The metal strip-shaped straight via is offset from the center point of the dielectric substrate, and the metal strip-shaped straight via and the metal strip-shaped L-shaped via penetrate five layers of the circuit board.

[0009] Among them, the transmission function area on the upper surface of the third circuit board is located within the T-shaped area formed by the metal elongated straight via and the two metal elongated L-shaped vias; on the dielectric substrates of the first, second, and fifth circuit boards, signal ports are opened at the short sides of the dielectric substrates at the beginning and end of the metal elongated straight vias and at the end of the dielectric substrates between the two metal elongated L-shaped vias, respectively inputting local oscillator (LO), radio frequency (RF), and intermediate frequency (IF) signals; the dielectric substrates of the second and fourth circuit boards have hollowed-out dielectric substrates and metal layers within the T-shaped area of ​​the three metal elongated vias;

[0010] On the upper surface of the dielectric substrate of the third circuit board, a microstrip-fin-suspended strip-microstrip line structure is provided in the transmission functional area; a low-pass filter of the low-pass filter structure is laterally connected in the suspended strip line section; the microstrip-fin-suspended strip-microstrip line structure mainly includes a first microstrip segment, a first impedance transformation segment, a microstrip-fin transition segment, a fin functional segment, a suspended strip line functional segment, a suspended strip line-microstrip line transition segment, a bandpass filter segment, and a second microstrip segment connected in sequence; wherein, the low-pass filter structure includes a low-pass filter and a third microstrip segment; two Schottky diodes are arranged between the fin functional segment and the suspended strip line functional segment, and the two Schottky diodes are placed in parallel in opposite directions;

[0011] On the lower surface of the dielectric substrate of the third circuit board, a defective structure is etched in the internal space of three long metal vias. The defective structure spans the microstrip-fin transition section, the fin functional section, the suspended strip functional section, and the suspended strip-microstrip transition section. It is a trapezoidal structure with the hypotenuse of the trapezoidal structure being either a curve or a straight line.

[0012] Furthermore, the metal layer on the dielectric substrate is formed by coating copper on the surface of the dielectric substrate.

[0013] Furthermore, the first microstrip segment includes a first microstrip line, one end of which is located at the edge of the transmission functional area, and the other end extends into the transmission functional area.

[0014] Furthermore, the first impedance transformation section includes a second microstrip line and a third microstrip line connected in sequence. The two ends of the second microstrip line are respectively connected to the first microstrip line and the third microstrip line, and the other end of the third microstrip line extends into the transmission functional area.

[0015] Furthermore, the microstrip-fin transition section includes a gradient microstrip line, a semi-circular de-resonance structure, and a fin gradient line; the left edge of the gradient microstrip line extends curvedly from the left end of the microstrip-fin transition section to the left end of the third microstrip line, and the right edge of the gradient microstrip line is flush with the right side of the third microstrip line; the center of the semi-circular de-resonance structure is located inside the straight through-hole of the left metal strip, and the semi-circle protrudes to the right; the fin gradient line has a near-right-angled trapezoidal structure, with a gap between it and the right side of the gradient microstrip line, and the right edge of the fin gradient line is connected to the L-shaped through-hole of the right metal strip, and the hypotenuse of the near-right-angled trapezoidal structure is a sine function curve.

[0016] Furthermore, the fin line functional segment is a fin line etched with an impedance matching structure; the suspended strip line functional segment includes a suspended strip line etched with an impedance matching structure and diode position marks; two Schottky diodes are disposed at the gap between the fin line functional segment and the suspended strip line functional segment, symmetrical about the fin line slot, and the two Schottky diodes are placed in parallel in opposite directions; the other end of the suspended strip line is connected to the suspended strip line-microstrip line transition segment; a low-pass filter structure is laterally connected in the middle of the suspended strip line functional segment; the other end of the low-pass filter structure is connected to the third microstrip segment; the third microstrip segment includes a fourth microstrip line, one end of which is located at the edge of the transmission functional area and receives the radio frequency signal RF, and the other end extends into the transmission functional area and connects to the low-pass filter structure.

[0017] Furthermore, the suspended strip-microstrip line transition section includes an isosceles trapezoidal structure for the suspended strip-microstrip line transition and a fifth microstrip line; the lower base of the isosceles trapezoidal structure for the suspended strip-microstrip line transition is connected to the suspended strip line, and the upper base is connected to the fifth microstrip line; the other end of the fifth microstrip line is connected to the bandpass filter section; the other end of the bandpass filter section is connected to the second microstrip section; the second microstrip section includes a sixth microstrip line; one end of the sixth microstrip line is located at the edge of the transmission functional area and receives the local oscillator signal LO, while the other end extends into the transmission functional area and connects to the bandpass filter section.

[0018] The beneficial effects of this invention are:

[0019] The mixer based on substrate integrated fin structure described in this invention has advantages such as low manufacturing cost, simple fabrication method, ability to form a self-encapsulated whole, and built-in low-frequency filtering effect. It can be realized by laminating multiple dielectric substrates, effectively overcoming the disadvantages of existing metal device circuits, such as mechanical cavity processing, bulky structure, and high cost. It has advantages such as low loss, weak dispersion, simple structure, small size, low cost, self-encapsulation, and easy integration with other RF circuits.

[0020] Compared to existing fin structures constructed using multilayer dielectric substrates, the substrate-integrated fin structure of this invention solves the problem of mounting various devices and functional modules on the fins. Furthermore, each module component can be flexibly replaced according to design needs, expanding the functionality of the substrate-integrated fins and increasing application scenarios. Transforming the three-dimensional functional structure into a two-dimensional one facilitates the direct design of fin functional areas within the integrated circuit, enabling effective integration of the circuit and the substrate-integrated fins. The elongated via design used in this invention also significantly reduces the processing precision requirements of the dielectric substrate and the assembly complexity, effectively lowering manufacturing costs. Attached Figure Description

[0021] Figure 1 This is a side view of the overall structure of the mixer based on substrate integrated fin structure described in this invention;

[0022] Figure 2 This is a schematic diagram of the upper surface structure of the first layer circuit board of the mixer with substrate integrated fin structure described in this invention;

[0023] Figure 3 This is a schematic diagram of the lower surface structure of the first layer circuit board of the mixer with substrate integrated fin structure described in this invention;

[0024] Figure 4 This is a schematic diagram of the upper surface structure of the second layer circuit board of the mixer based on the substrate integrated fin structure described in this invention;

[0025] Figure 5 This is a schematic diagram of the lower surface structure of the second layer circuit board of the mixer based on the substrate integrated fin structure described in this invention;

[0026] Figure 6 This is a schematic diagram of the upper surface structure of the third layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0027] Figure 7 This is a schematic diagram of the lower surface structure of the third layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0028] Figure 8 This is a schematic diagram of the upper surface structure of the fourth layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0029] Figure 9 This is a schematic diagram of the lower surface structure of the fourth layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0030] Figure 10 This is a schematic diagram of the upper surface structure of the fifth layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0031] Figure 11This is a schematic diagram of the lower surface structure of the fifth layer circuit board of the mixer based on substrate integrated fin structure described in this invention;

[0032] Figure 12 This is a schematic diagram showing the division of the upper surface of the third layer circuit board in the mixer described in this invention;

[0033] Figure 13 This is a schematic diagram showing the division of the lower surface section of the third layer circuit board in the mixer described in this invention;

[0034] Figure 14 This is a schematic diagram of the frequency conversion loss simulation results of the substrate-integrated finned mixer described in the embodiment.

[0035] Figure 15 This is a schematic diagram of the simulation results of the three-port isolation of the substrate-integrated finned mixer described in the embodiment.

[0036] In the diagram: 1. First layer circuit board, 2. Second layer circuit board, 3. Third layer circuit board, 4. Fourth layer circuit board, 5. Fifth layer circuit board, 6. Dielectric substrate, 7. Copper cladding layer, 8. Cutout area A, 9. Cutout area B, 10. Fin slot, 11. Elongated via, 12. Metal via, 13. Elongated metallized via, 14. Copper cladding area, 15. L-shaped elongated metallized via, 16. Non-copper cladding area, 17. Cutout area, 18. Schottky diode, 19. First microstrip 20. First impedance change loop segment, 21. Microstrip-fin transition segment, 22. Fin functional segment, 23. Suspended strip functional segment, 24. Suspended strip-microstrip transition segment, 25. Bandpass filter segment, 26. Second impedance change loop segment, 27. First microstrip segment, 28. Radio frequency (RF) port, 29. Low-pass filter, 30. Intermediate frequency (IF) port, 31. Local oscillator (LO) port, 32. Ground, 33. First ground change segment, 34. Ground without copper cladding area, 35. Second ground change segment. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] A mixer based on a substrate integrated fin structure includes a first circuit board, a second circuit board, a third circuit board, a fourth circuit board and a fifth circuit board that are tightly bonded together from top to bottom. The circuit boards include a rectangular dielectric substrate and metal layers printed on the upper and lower surfaces of the dielectric substrate.

[0039] A long, straight metal via is arranged parallel to the long side of a rectangular dielectric substrate. Two long, L-shaped metal vias are parallel to the straight via on one side and adjacent to each other on the other side. The L-shaped metal vias penetrate five layers of the circuit board. The straight metal via is located slightly to the left of the center point of the dielectric substrate. The space within the T-shaped area containing the straight metal via and the two L-shaped metal vias serves as the transmission functional area. On the dielectric substrates of the first, second, and fifth circuit boards, signal ports are respectively opened at the short sides of the dielectric substrates at both ends of the straight metal via and on the right side of the L-shaped metal via. The three signal ports can respectively input local oscillator (LO), radio frequency (RF), and intermediate frequency (IF) signals. The dielectric substrates of the second and fourth circuit boards have all the space within the area of ​​the three long metal vias hollowed out, forming a cutout area.

[0040] The upper surface of the dielectric substrate of the first circuit board is entirely copper-clad, and the lower surface is entirely copper-clad except for the transmission functional area; the upper and lower surfaces of the dielectric substrates of the second and fourth circuit boards are entirely copper-clad except for the transmission functional area; the upper surface of the dielectric substrate of the third circuit board is entirely copper-clad except for the transmission functional area, and the lower surface is entirely copper-clad; the upper surface of the dielectric substrate of the fifth circuit board is entirely copper-clad except for the transmission functional area, and the lower surface is entirely copper-clad.

[0041] On the upper surface of the dielectric substrate of the third circuit board, a microstrip-fin-suspended strip-microstrip line structure is provided in the transmission functional area. A low-pass filter structure is laterally connected to the right in the suspended strip-microstrip line section. The microstrip-fin-suspended strip-microstrip line structure includes a first microstrip segment, a first impedance transformation segment, a microstrip-fin transition segment, a fin functional segment, a suspended strip-microstrip line functional segment, a suspended strip-microstrip line transition segment, a bandpass filter segment, and a second microstrip segment. The low-pass filter structure includes a low-pass filter and a third microstrip segment. Two Schottky diodes are placed between the fin functional segment and the suspended strip-microstrip line functional segment, and the two Schottky diodes are placed in parallel in opposite directions.

[0042] On the lower surface of the dielectric substrate of the third circuit board, a defective structure is etched in the internal space of three long metal vias. The defective structure spans the microstrip-fin transition section, the fin functional section, the suspended strip functional section, and the suspended strip-microstrip transition section. It is a trapezoidal structure with the hypotenuse of the trapezoid being either a curve or a straight line.

[0043] Furthermore, the first microstrip segment includes a first microstrip line, one end of which is located at the edge of the transmission functional region, and the other end extends into the transmission functional region; the first impedance transformation segment includes a second microstrip line and a third microstrip line connected in sequence, with the two ends of the second microstrip line connected to the first microstrip line and the third microstrip line respectively, and the other end of the third microstrip line extending into the transmission functional region; the microstrip-fin transition segment includes a tapered microstrip line, a semi-circular de-resonance structure, and a fin tapered line; the left edge of the tapered microstrip line begins at the left end of the microstrip-fin transition segment. The curve extends to the left end of the third microstrip line, and its right edge is flush with the right side of the third microstrip line; the center of the semi-circular de-resonance structure is located at the left metal strip-shaped through-hole, which protrudes to the right; the fin tapered line has a near-right-angled trapezoidal structure, with a gap between it and the right side of the tapered microstrip line, and its right edge is connected to the right metal strip-shaped L-shaped through-hole, with the hypotenuse of the right-angled trapezoid forming a sine function curve; the fin functional segment is a fin with an etched impedance matching structure; the suspension strip functional segment includes a suspension strip with an etched impedance matching structure and diode position markings; Two Schottky diodes are placed at the gap between the fin line functional segment and the suspended strip line functional segment, symmetrical about the fin line slot, and are arranged in reverse parallel. The other end of the suspended strip line is connected to the suspended strip line-microstrip line transition section. A low-pass filter structure is laterally connected in the middle of the suspended strip line functional segment. The other end of the low-pass filter structure is connected to the third microstrip segment. The third microstrip segment includes a fourth microstrip line, one end of which is located at the edge of the transmission functional area and receives the radio frequency (RF) signal, while the other end extends into the transmission functional area and connects to the low-pass filter. Wave structure; the suspended strip-microstrip line transition section includes an isosceles trapezoidal structure of the suspended strip-microstrip line transition, the fifth strip line, the lower base of the isosceles trapezoidal structure of the suspended strip-microstrip line transition is connected to the suspended strip line, the upper base is connected to the fifth microstrip line, the other end of the fifth microstrip line is connected to the bandpass filter section; the other end of the bandpass filter section is connected to the second microstrip section; the second microstrip section includes a sixth microstrip line, one end of the sixth microstrip line is located at the edge of the transmission functional area, inputting the local oscillator signal LO, and the other end extends into the transmission functional area, connecting to the bandpass filter section.

[0044] Furthermore, at the three signal ports, the first, second, and third microstrip segments are connected to external circuits or SMA adapters, respectively. Furthermore, the widths of the first, second, third, and fifth microstrip lines are different.

[0045] Furthermore, the low-pass filter structure and band-pass filter components can be replaced, including microstrip line filters, cavity filters, chip filters, and chip filter banks.

[0046] Furthermore, several circular metal through holes are opened outside the signal ports and transmission function areas of the five-layer circuit board for fixing the five-layer circuit board; the signal ports of the third and fourth circuit boards have two metal through holes for fixing the signal adapters, which serve as the input and output ports of the mixer.

[0047] Furthermore, the dielectric substrate of the third circuit board is made of Rogers RT / duroid 5880, with a relative permittivity of 2.2 and a substrate thickness of 0.254 mm; the dielectric substrates of the other circuit boards are made of F4B, with a relative permittivity of 2.65 and a substrate thickness of 2 mm.

[0048] Furthermore, the Schottky diodes are arranged in reverse parallel configuration, symmetrical about the fin slot as the central axis.

[0049] The following is a more specific example:

[0050] This embodiment provides a mixer based on a substrate-integrated finned structure, and its overall structural side view is shown below. Figure 1 As shown, a planar three-port circuit includes a first circuit board, a second circuit board, a third circuit board, a fourth circuit board, and a fifth circuit board that are tightly attached to each other from top to bottom. The circuit boards include a rectangular dielectric substrate and metal layers printed on the upper and lower surfaces of the dielectric substrate.

[0051] A long, rectangular metal via is arranged parallel to the long side of a rectangular dielectric substrate. Two long, L-shaped metal vias are parallel to the long, rectangular via on one side and adjacent to each other on the other side, penetrating five layers of the circuit board. The long, rectangular metal vias are located slightly to the left of the center point of the dielectric substrate. The space within the T-shaped area containing the long, rectangular metal vias and the two long, L-shaped metal vias serves as the transmission functional area. On the dielectric substrates of the first, second, and fifth circuit boards, signal ports are respectively opened at the short sides of the dielectric substrates at both ends of the long, rectangular metal vias and on the right side of the long, L-shaped metal vias. The three signal ports can respectively input local oscillator (LO), radio frequency (RF), and intermediate frequency (IF) signals. The dielectric substrates of the second and fourth circuit boards have all the space within the area of ​​the three long, rectangular metal vias hollowed out, forming a cutout area.

[0052] The upper and lower surfaces of the dielectric substrate of the first circuit board are as follows: Figure 2-3 As shown, the upper surface is entirely copper-clad, and the lower surface, except for the transmission functional area, is entirely copper-clad; the upper and lower surfaces of the dielectric substrate of the second circuit board are as follows. Figure 4-5 As shown, the upper and lower surfaces, except for the transmission functional areas, are entirely copper-clad; the upper and lower surfaces of the dielectric substrate of the third circuit board are as follows. Figure 6-7 As shown, the upper surface, except for the transmission functional area, is entirely copper-clad, and the lower surface is entirely copper-clad; the upper and lower surfaces of the dielectric substrate of the fourth circuit board are as follows. Figure 8-9 As shown, the upper and lower surfaces, except for the transmission functional areas, are entirely copper-clad; the upper and lower surfaces of the dielectric substrate of the fifth circuit board are as follows. Figure 10-11 As shown, the upper surface is entirely copper-clad except for the transmission function area, and the lower surface is entirely copper-clad.

[0053] like Figure 12-13As shown, on the upper surface of the dielectric substrate of the third circuit board, a microstrip-fin-suspended strip-microstrip line structure is provided within the transmission functional area. A low-pass filter structure is laterally connected to the right in the suspended strip-microstrip line section. The microstrip-fin-suspended strip-microstrip line structure includes a first microstrip segment, a first impedance transformation segment, a microstrip-fin transition segment, a fin functional segment, a suspended strip-microstrip line functional segment, a suspended strip-microstrip line transition segment, a bandpass filter segment, and a second microstrip segment. The low-pass filter structure includes a low-pass filter and a third microstrip segment. Two Schottky diodes are disposed between the fin functional segment and the suspended strip-microstrip line functional segment, and the two Schottky diodes are placed in parallel in reverse. The first microstrip segment includes a first microstrip line. One end is located at the edge of the transmission functional area, and the other end extends into the transmission functional area; the first impedance transformation section includes a second microstrip line and a third microstrip line connected in sequence, with the two ends of the second microstrip line connected to the first microstrip line and the third microstrip line respectively, and the other end of the third microstrip line extending into the transmission functional area; the microstrip-fin transition section includes a gradient microstrip line, a semi-circular de-resonance structure, and a fin gradient line; the left edge of the gradient microstrip line curves from the left end of the microstrip-fin transition section to the left end of the third microstrip line, and the right edge is flush with the right side of the third microstrip line; the center of the semi-circular de-resonance structure is located at the left-side elongated metal via hole, protruding to the right; the fin gradient line has a near-right-angled trapezoidal structure. A gap is left between the right side of the gradient microstrip line and the right side of the trapezoid, which is connected to the right side of the metal strip-shaped L-shaped via. The hypotenuse of the trapezoid is a sine function curve. The fin line functional segment is a fin line with an etched impedance matching structure. The suspended strip line functional segment includes a suspended strip line with an etched impedance matching structure and diode position marks. Two Schottky diodes are placed at the gap between the fin line functional segment and the suspended strip line functional segment, symmetrical about the fin line slot, and the Schottky diodes are placed in parallel in opposite directions. The other end of the suspended strip line is connected to the suspended strip line-microstrip line transition segment. A low-pass filter structure is connected laterally in the middle of the suspended strip line functional segment. The other end of the low-pass filter structure is connected to the third microstrip segment. The third microstrip segment includes a fourth microstrip line. The fourth microstrip line has one end located at the edge of the transmission functional area, receiving the radio frequency (RF) signal, and the other end extending into the transmission functional area to connect to the low-pass filter structure. The suspended strip-microstrip line transition section includes an isosceles trapezoidal structure. The fifth strip line, with its lower base connected to the suspended strip line and its upper base connected to the fifth microstrip line, has the other end connected to the bandpass filter section. The other end of the bandpass filter section connects to the second microstrip section. The second microstrip section includes a sixth microstrip line, one end of which is located at the edge of the transmission functional area, receiving the local oscillator (LO) signal, and the other end extending into the transmission functional area to connect to the bandpass filter section.

[0054] At the three signal ports, the first microstrip segment, the second microstrip segment, and the third microstrip segment are respectively connected to external circuits or SMA adapters.

[0055] The widths of the first, second, third, and fifth microstrip lines are different.

[0056] On the lower surface of the dielectric substrate of the third circuit board, a defective structure is etched in the internal space of three long metal vias. The defective structure spans the microstrip-fin transition section, the fin functional section, the suspended strip functional section, and the suspended strip-microstrip transition section. It is a trapezoidal structure with the hypotenuse of the trapezoid being either a curve or a straight line.

[0057] The devices in the low-pass filter structure and band-pass filter section can be replaced, and the categories include microstrip line filters, cavity filters, chip filters and chip filter banks.

[0058] Several circular metal through holes are provided outside the signal ports and transmission function areas of the five-layer circuit board for fixing the five-layer circuit board; two metal through holes are provided at the signal ports of the third and fourth circuit boards for fixing signal adapters, which serve as the input and output ports of the mixer.

[0059] In this embodiment, the dielectric substrate of the third circuit board is Rogers RT / duroid 5880 with a relative permittivity of 2.2 and a substrate thickness of 0.254 mm; the dielectric substrates of the other circuit boards are made of F4B with a relative permittivity of 2.65 and a substrate thickness of 2 mm.

[0060] The substrate-integrated finline mixer of this invention uses a finline structure with anti-parallel Schottky diodes to achieve the mixer function. The shape of the impedance matching section between the finline and the suspended strip is adjusted through simulation to achieve the best mixing effect and minimum insertion loss.

[0061] The performance characteristics of the mixer described in this invention are mainly reflected in the signal isolation between the three ports, i.e., the isolation degree; and the difference between the input signal strength and the output signal strength during mixing, i.e., the mixing loss.

[0062] The simulation results diagrams for the three-port signal connectivity of the substrate-integrated fin structure mixer described in this embodiment are as follows: Figure 14 and Figure 15 As shown. By Figure 14 As shown, when the input RF signal power is -5dBm and the local oscillator signal is 7dBm, the mixer conversion loss is less than 8dB in the frequency range of 8.25GHz to 10.0GHz. Figure 15This indicates that within the frequency range of 8.25GHz to 10.25GHz, the isolation between the local oscillator port (LO) and the radio frequency port (RF) is greater than 20dB; the isolation between the local oscillator port (LO) and the intermediate frequency port (IF) is greater than 50dB; and the isolation between the radio frequency port (RF) and the intermediate frequency port (IF) is greater than 65dB. This ensures that when the mixer is working normally, there is a high degree of isolation between the intermediate frequency signal, the radio frequency signal, and the local oscillator signal, avoiding mutual interference.

Claims

1. A mixer based on a substrate integrated finned array structure, comprising a mixer circuit structure as the main body; characterized in that, The mixer circuit structure includes a multilayer circuit board, each circuit board including a dielectric substrate and metal layers printed on the upper and lower surfaces of the dielectric substrate. The mixer circuit structure is a planar three-port circuit, and the multilayer circuit board includes a first circuit board, a second circuit board, a third circuit board, a fourth circuit board, and a fifth circuit board that are tightly attached to each other from top to bottom; Each circuit board has a metal strip-shaped straight via and two metal strip-shaped L-shaped vias on its upper and lower surface metal layers, which are parallel to the long side of the dielectric substrate. One branch of the metal strip-shaped L-shaped via is parallel to the metal strip-shaped straight via, and the other branch of the metal strip-shaped L-shaped via extends away from the metal strip-shaped straight via. The metal strip-shaped straight via is offset from the center point of the dielectric substrate, and the metal strip-shaped straight via and the metal strip-shaped L-shaped via penetrate five layers of the circuit board. Among them, the transmission function area on the upper surface of the third circuit board is located within the T-shaped area formed by the metal elongated straight via and the two metal elongated L-shaped vias; on the dielectric substrates of the first, second, and fifth circuit boards, signal ports are opened at the short sides of the dielectric substrates at the beginning and end of the metal elongated straight vias and at the end of the dielectric substrates between the two metal elongated L-shaped vias, respectively inputting local oscillator (LO), radio frequency (RF), and intermediate frequency (IF) signals; the dielectric substrates of the second and fourth circuit boards have hollowed-out dielectric substrates and metal layers within the T-shaped area of ​​the three metal elongated vias; On the upper surface of the dielectric substrate of the third circuit board, a microstrip-fin-suspended strip-microstrip line structure is provided in the transmission functional area; a low-pass filter of the low-pass filter structure is laterally connected in the suspended strip line section; the microstrip-fin-suspended strip-microstrip line structure includes a first microstrip segment, a first impedance transformation segment, a microstrip-fin transition segment, a fin functional segment, a suspended strip line functional segment, a suspended strip line-microstrip line transition segment, a bandpass filter segment, and a second microstrip segment connected in sequence; wherein, the low-pass filter structure includes a low-pass filter and a third microstrip segment; two Schottky diodes are arranged between the fin functional segment and the suspended strip line functional segment, and the two Schottky diodes are placed in parallel in opposite directions; On the lower surface of the dielectric substrate of the third circuit board, a defective structure is etched in the internal space of three metal strip vias. The defective structure spans the microstrip-fin transition section, the fin functional section, the suspended strip functional section, and the suspended strip-microstrip transition section. It is a trapezoidal structure, and the hypotenuse of the trapezoidal structure is either a curve or a straight line.

2. A mixer based on a substrate integrated fin structure according to claim 1, characterized in that, The metal layer on the dielectric substrate is formed by coating copper on the surface of the dielectric substrate.

3. A mixer based on a substrate integrated fin structure according to claim 1, characterized in that, The first microstrip segment includes a first microstrip line, one end of which is located at the edge of the transmission functional area, and the other end extends into the transmission functional area.

4. A mixer based on a substrate integrated fin structure according to claim 3, characterized in that, The first impedance transformation section includes a second microstrip line and a third microstrip line connected in sequence. The two ends of the second microstrip line are respectively connected to the first microstrip line and the third microstrip line, and the other end of the third microstrip line extends into the transmission functional area.

5. A mixer based on a substrate integrated fin structure according to claim 4, characterized in that, The microstrip-fin transition section includes a gradient microstrip line, a semi-circular de-resonance structure, and a gradient fin line. The left edge of the gradient microstrip line extends from the left end of the microstrip-fin transition section to the left end of the third microstrip line, and the right edge of the gradient microstrip line is flush with the right side of the third microstrip line; the center of the semi-circular de-resonance structure is located inside the long metal through hole on the left, and the semi-circle bulges to the right. The fin gradient line has a near-right trapezoidal structure, with a gap between it and the right side of the gradient microstrip line. The right edge of the fin gradient line is connected to the right side of the metal strip L-shaped via. The hypotenuse of the near-right trapezoidal structure is a sine function curve.

6. A mixer based on a substrate integrated fin structure according to claim 1, characterized in that, The fin line functional segment is a fin line etched with an impedance matching structure; the suspended strip line functional segment includes a suspended strip line etched with an impedance matching structure and diode position marks; two Schottky diodes are placed at the gap between the fin line functional segment and the suspended strip line functional segment, symmetrical about the fin line slot, and the two Schottky diodes are placed in parallel in opposite directions; the other end of the suspended strip line is connected to the suspended strip line-microstrip line transition segment; a low-pass filter structure is laterally connected in the middle of the suspended strip line functional segment; the other end of the low-pass filter structure is connected to the third microstrip segment; the third microstrip segment includes a fourth microstrip line, one end of which is located at the edge of the transmission functional area and receives the radio frequency signal RF, and the other end extends into the transmission functional area and connects to the low-pass filter structure.

7. A mixer based on a substrate integrated fin structure according to claim 1, characterized in that, The suspended strip-microstrip transition section includes an isosceles trapezoidal structure and a fifth microstrip line; the lower base of the isosceles trapezoidal structure is connected to the suspended strip line, and the upper base is connected to the fifth microstrip line; the other end of the fifth microstrip line is connected to the bandpass filter section; the other end of the bandpass filter section is connected to the second microstrip section; the second microstrip section includes a sixth microstrip line; one end of the sixth microstrip line is located at the edge of the transmission functional area and receives the local oscillator signal LO, while the other end extends into the transmission functional area and connects to the bandpass filter section.

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