High-speed feed circuit for realizing low-reflection transmission of intermediate-frequency signals in broadband

Abstract

The invention discloses a high-speed feed circuit for realizing low-reflection transmission of an intermediate frequency signal in a broadband, relates to the technical field of direct modulation and sub-terahertz-terahertz communication, and solves the problems of large reflection, poor signal integrity and narrow intermediate frequency bandwidth of an existing feed circuit. The antenna comprises a first coaxial connector, a first transition structure and a microstrip line, the first coaxial connector comprises a first coaxial probe extending towards the microstrip line, the first transition structure comprises a dielectric substrate, back metal and a first metal groove, one end of the dielectric substrate is connected with the first coaxial connector, and the other end of the dielectric substrate is connected with the second coaxial connector. The microstrip line is arranged on the upper surface of the dielectric substrate, one end of the microstrip line is connected with the first coaxial probe, the lower surface of the dielectric substrate is covered with the back metal, the first metal groove is formed in the face, away from the dielectric substrate, of the back metal, and the position of the first metal groove corresponds to the position of the first coaxial probe. The structure is simple and symmetrical, and intermediate-frequency signal low-reflection transmission can be realized in a broadband.

Description

Technical Field

[0001] The present invention relates to the technical field of direct modulation and sub-terahertz-terahertz communication, and in particular to a high-speed feeding circuit for realizing low-reflection transmission of intermediate frequency signals within a broadband. Background Art

[0002] The rapid development of terahertz frequency multipliers and low-noise amplifiers has significantly improved the output power and receiver sensitivity of terahertz communication systems. While terahertz direct amplitude modulators, a core component of terahertz communication systems, have made significant progress in high-speed and high-deep modulation, they still face challenges in achieving further breakthroughs in modulation rate and bandwidth, high return loss, imperfect direct modulation theory, and poor device consistency. These challenges hinder the development of terahertz communication towards compact, portable, and high-speed communication. Therefore, high-speed direct modulation devices are crucial for the development of high-bandwidth, miniaturized, and low-complexity high-speed communication systems. The modulator's feed circuit significantly influences its transmission rate.

[0003] The terahertz direct modulator achieves amplitude modulation by controlling the on and off switching of the diode. The quality and bandwidth of the input intermediate frequency signal will affect the performance of the modulator. The intermediate frequency signal is fed through a coaxial connector, input to the microstrip line through the coaxial-to-microstrip structure, and finally fed to the substrate where the diode is located through a gold jump wire. To ensure the effective feeding of the intermediate frequency signal, the reflection caused by impedance mismatch at the coaxial-to-microstrip junction must be reduced. In addition, in actual assembly, an air gap is easily formed between the coaxial probe and the microstrip line. Generally, pressure is applied to the coaxial probe to cause it to deform to achieve interconnection with the microstrip line. However, the degree of deformation of the coaxial probe under force is less controllable, which will further affect the impedance matching effect. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a high-speed feeding circuit that realizes low-reflection transmission of intermediate frequency signals within a broadband, solving the problems of large reflection, poor signal integrity and narrow intermediate frequency bandwidth of the existing feeding circuit.

[0005] A high-speed feeding circuit for achieving low-reflection transmission of intermediate frequency signals within a broadband range includes a first coaxial connector, a first transition structure, and a microstrip line. The first coaxial connector includes a first coaxial probe extending toward the microstrip line. The first transition structure includes a dielectric substrate, a back metal, and a first metal groove. One end of the dielectric substrate is connected to the first coaxial connector. The microstrip line is provided on the upper surface of the dielectric substrate. One end of the microstrip line is connected to the first coaxial probe. The back metal covers the lower surface of the dielectric substrate. The first metal groove is provided on a side of the back metal away from the dielectric substrate. The position of the first metal groove corresponds to the position of the first coaxial probe.

[0006] Further, it further includes a ground plane. One end of the ground plane is in contact with the first coaxial connector, and one side of the ground plane is in contact with the side of the back metal away from the dielectric substrate. By adjusting the width, length of the first metal groove, and the distance between the top of the first metal groove and the side of the ground plane close to the back metal, impedance matching between the first coaxial connector and the microstrip line is achieved.

[0007] Further, the first transition structure further includes a first trapezoidal soldering structure, and the first coaxial probe is connected to the microstrip line through the first trapezoidal soldering structure.

[0008] Further, the upper surface of the first trapezoidal soldering structure is connected to the lower surface of the first coaxial probe, the lower surface of the first trapezoidal soldering structure is connected to the dielectric substrate, and the inclined surface of the first trapezoidal soldering structure is connected to one end of the microstrip line.

[0009] Further, by changing the height and width of the first trapezoidal soldering structure, broadband matching can be achieved within a tolerance range of ±50 μm.

[0010] Further, the material of the dielectric substrate is one of rogers 5880 and rogers 3003.

[0011] Further, it further includes a second transition structure symmetrically arranged with the first transition structure on the left and right. The second transition structure has the same structure as the first transition structure, and the other end of the microstrip line connected by the second transition structure is connected to the second coaxial connector.

[0012] The beneficial effects of the present invention include:

[0013] The present invention realizes broadband impedance matching between the coaxial connector and the microstrip line by introducing a suspended microstrip through slotting on the back of the microstrip line. At the same time, a trapezoidal soldering structure is introduced to fill the air gap between the coaxial probe and the microstrip gold layer. The structure is simple and symmetric, and low-reflection transmission of intermediate-frequency signals can be achieved within a wide band. Description of the Drawings

[0014] Figure 1 It is a planar circuit structure diagram related to Embodiment 1 of the present application. The A side is the top view, and the B side is the bottom view.

[0015] Figure 2 It is a planar circuit structure diagram related to Embodiment 2 of the present application. The A side is the top view, and the B side is the bottom view.

[0016] Figure 3 It is a three-dimensional circuit structure related to Embodiment 4 of the present application Figure 1 .

[0017] Figure 4 It is a three-dimensional circuit structure related to Embodiment 4 of the present application Figure 2 .

[0018] Figure 5 This is the S-parameter simulation result related to Embodiment 5 of the present application.

[0019] Figure 6 This is the measured S-parameter result related to Embodiment 5 of the present application.

[0020] Reference numerals

[0021] 1 - First coaxial connector, 10 - First insulating medium, 11 - First coaxial probe, 2 - Second coaxial connector, 20 - First insulating medium, 21 - Second coaxial probe, 3 - Microstrip line, 4 - Dielectric substrate, 5 - Back metal, 61 - First trapezoidal solder structure, 62 - Second trapezoidal solder structure, 71 - First metal groove, 72 - Second metal groove, 81 - Upper cavity, 82 - Lower cavity. Detailed implementation manners

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are only a part rather than all of the embodiments of the present application. Therefore, the detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0023] Embodiment 1

[0024] A high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband, as Figure 1 shown, includes a first coaxial connector 1, a first transition structure, and a microstrip line 3. The first coaxial connector 1 includes a first coaxial probe 11 extending in the direction of the microstrip line 3. The first transition structure includes a dielectric substrate 4, a back metal 5, and a first metal groove 71. One end of the dielectric substrate 4 is connected to the first coaxial connector 1. The microstrip line 3 is disposed on the upper surface of the dielectric substrate 4. One end of the microstrip line 3 is connected to the first coaxial probe 11. The back metal 5 covers the lower surface of the dielectric substrate 4. The first metal groove 71 is disposed on the side of the back metal 5 away from the dielectric substrate 4, and the position of the first metal groove 71 corresponds to the position of the first coaxial probe 11.

[0025] Specifically, it further includes a ground plate. One end of the ground plate is in contact with the first coaxial connector 1, and one side of the ground plate is in contact with the side of the back metal 5 away from the dielectric substrate 4. By adjusting the width, length, height of the first metal groove 71 and the distance between the top of the first metal groove 71 and the side of the ground plate close to the back metal 5, the impedance matching between the first coaxial connector 1 and the microstrip line 3 is achieved.

[0026] The first transition structure further includes a first trapezoidal soldering structure 61. The first coaxial probe 11 is connected to the microstrip line 3 through the first trapezoidal soldering structure 61.

[0027] The upper surface of the first trapezoidal soldering structure 61 is connected to the lower surface of the first coaxial probe 11. The lower surface of the first trapezoidal soldering structure 61 is connected to the dielectric substrate 4. The inclined surface of the first trapezoidal soldering structure 61 is connected to one end of the microstrip line 3. By changing the height and width of the first trapezoidal soldering structure 61 within the tolerance range of ±50um, broadband matching can be achieved.

[0028] The material of the dielectric substrate 4 is one of rogers 5880 and rogers 3003.

[0029] Embodiment 2

[0030] The difference between this embodiment and Embodiment 1 is that it further includes a second transition structure symmetrically arranged with the first transition structure on the left and right. The structure of the second transition structure is the same as that of the first transition structure. The second transition structure connects the other end of the microstrip line 3 to the second coaxial connector 2. As Figure 2 shown, it includes a microstrip line 3 and symmetrically arranged first coaxial connector 1 and second coaxial connector 2. The first coaxial connector 1 includes a first coaxial probe 11 extending towards the microstrip line 3, and the second coaxial connector 2 includes a second coaxial probe 21 extending towards the microstrip line 3.

[0031] The first coaxial transition structure includes a first dielectric substrate, a first back metal, a first metal groove 71 and a first trapezoidal soldering structure 61. The second coaxial transition structure includes a second dielectric substrate, a second back metal, a second metal groove 72 and a second trapezoidal soldering structure 62. In this embodiment, the first dielectric substrate and the second dielectric substrate are the same piece, i.e., the dielectric substrate 4, and the first back metal and the second back metal are the same piece, i.e., the back metal 5. The two ends of the dielectric substrate 4 are respectively connected to the first coaxial connector 1 and the second coaxial connector 2. The two ends of the microstrip line 3 are respectively connected to the first coaxial probe 11 and the second coaxial probe 21. The first metal groove 71 and the second metal groove 72 are arranged on the side of the back metal 5 away from the dielectric substrate 4. The positions of the first metal groove 71 and the second metal groove 72 correspond to the positions of the first coaxial probe 11 and the second coaxial probe 21 respectively.

[0032] Specifically, the first coaxial connector further includes a first insulating medium 10, and the second coaxial connector 2 further includes a second insulating medium 20. The first coaxial probe 11 is perpendicular to the first insulating medium 10, and the second coaxial probe 21 is perpendicular to the second insulating medium 20. Both ends of the dielectric substrate 4 are respectively connected to the first insulating medium 10 and the second insulating medium 20.

[0033] The first coaxial probe 11 is connected to the microstrip line 3 through a first trapezoidal soldering structure 61, and the second coaxial probe 21 is connected to the microstrip line 3 through a second trapezoidal soldering structure 62.

[0034] By changing the height and width of the first trapezoidal soldering structure 61 and the second trapezoidal soldering structure 62, broadband matching can be achieved within a tolerance range of ±50 um.

[0035] The other end of the ground plane contacts the second coaxial connector 2. By adjusting the width, length, height of the second metal slot 72 and the distance between the top of the first metal slot 72 and the side of the ground plane close to the back metal 5, impedance matching between the second coaxial connector 2 and the microstrip line 3 is achieved.

[0036] Embodiment 3

[0037] The difference between this embodiment and Embodiment 2 is that the first back metal and the second back metal are not the same piece. They are arranged on the ground plane, and there is a gap between their adjacent sides. Similarly, there is also a gap between the adjacent sides of the first dielectric substrate and the second dielectric substrate.

[0038] Embodiment 4

[0039] As Figures 3-4 shown, the difference between this embodiment and Embodiment 2 is that it further includes a metal cavity. Both ends of the metal cavity are connected to the first coaxial connector 1 and the second coaxial connector 2. The metal cavity includes an upper cavity 81 and a lower cavity 82. The upper cavity 81 covers the upper surface of the dielectric substrate 4, and the lower cavity 82 covers the back metal 5 as a ground plane. By adjusting the width, length, height of the metal slot and the distance between the top of the metal slot and the side of the lower cavity 82 close to the back metal 5, impedance matching between the coaxial connector and the microstrip line 3 is achieved.

[0040] Embodiment 5

[0041] The difference between this embodiment and embodiment 4 is that the parameters of the first metal slot 71 and the second metal slot 72 are different for dielectric substrates 4 made of different materials and microstrip lines 3 of different widths. The current structure serves as the feeding structure of the terahertz amplitude modulator. Specifically, the suspended microstrip is introduced through the first metal slot 71 and the second metal slot 72 to achieve impedance matching between the first coaxial connector 1 and the microstrip line 3, thereby ensuring low-reflection transmission of the intermediate frequency signal within a broadband. In a terahertz direct modulation communication system, the intermediate frequency signal is fed from the first coaxial connector 1, transmitted through the microstrip line 3, and fed into the modulation main circuit via a jumper, and then the terminal voltage of the diode is controlled to achieve modulation.

[0042] To meet the current demand for low-reflection transmission of intermediate frequency signals within a broadband, the distance between the top of the metal slot and the side of the lower cavity 82 close to the back metal 5 was optimized in the HFSS simulation software to find an optimal value, which reduces the reflection of the overall structure within a broadband.

[0043] In the simulation process, the parameters of the first transition solder structure 61 and the second transition solder structure 62 are adjusted and simulated, and the influence of the height and width of the first transition solder structure 61 and the second transition solder structure 62 on the overall result is determined by the simulation results, which is equivalent to simulating the influence of the uncertainty of the contact between the conductive glue and the probe in actual processing.

[0044] The optimized parameters obtained by specific simulation are: the coaxial connector model is D550M0202F07, the dielectric substrate 4 material is rogers5880, the dielectric substrate 4 thickness is 127um, the microstrip line 3 width is 400um, the microstrip line 3 and the back metal 5 thickness are both 1um, the first trapezoidal solder structure 61 (the second trapezoidal solder structure 62) is 230um high, 430um wide, the length of the upper surface is about 50um longer than the length of the first coaxial probe 11 (the second coaxial probe 21), and the length of the lower surface is about 250um longer than the length of the first coaxial probe 11 (the second coaxial probe 21). The length of the first metal groove 71 (the second metal groove 72) is 1.676mm, the width is 600um, and the height is 40um (the same as the distance between the top of the metal groove and the side of the lower cavity 82 close to the back metal 5), and the length of the metal cavity is 10.54mm. The corresponding simulation results are as follows: Figure 5 、 Figure 6 shown.

[0045] Figure 5 The blue solid line is the reflection coefficient S11, and the red dotted line is the transmission coefficient S21. For this embodiment, the reflection coefficient S11 is less than -20 dB in the range of 0-50 GHz.

[0046] Figure 6This is the measured S-parameter result graph for this embodiment. The black solid line represents the reflection coefficient S11, and the red solid line represents the transmission coefficient S21. For this embodiment, the reflection coefficient S11 from 1 to 59 GHz is lower than -10 dB, and in most frequency bands, it is lower than -15 dB. The transmission coefficient between 1 and 45 GHz is basically lower than 1 dB. For the frequency band above 45 GHz, the insertion loss gradually increases with frequency and approaches 2.8 dB. The overall frequency band shows a relatively low reflection coefficient, and there is a certain gap in performance compared with the simulation.

[0047] The above-described embodiments merely represent the specific implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application.

Claims

1. A high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband, characterized in that, It includes a first coaxial connector (1), a first transition structure, and a microstrip line (3). The first coaxial connector (1) includes a first coaxial probe (11) extending towards the microstrip line (3). The first transition structure includes a dielectric substrate (4), a back metal (5), and a first metal groove (71). One end of the dielectric substrate (4) is connected to the first coaxial connector (1). The microstrip line (3) is disposed on the upper surface of the dielectric substrate (4). One end of the microstrip line (3) is connected to the first coaxial probe (11). The back metal (5) covers the lower surface of the dielectric substrate (4). The first metal groove (71) is disposed on the side of the back metal (5) away from the dielectric substrate (4). The position of the first metal groove (71) corresponds to the position of the first coaxial probe (11).

2. The high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband according to claim 1, wherein It further includes a ground plane. One end of the ground plane is in contact with the first coaxial connector (1). One side of the ground plane is in contact with the side of the back metal (5) away from the dielectric substrate (4). By adjusting the width, length of the first metal groove (71), and the distance between the top of the first metal groove (71) and the side of the ground plane close to the back metal (5), impedance matching between the first coaxial connector (1) and the microstrip line (3) is achieved.

3. A high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband according to claim 1, characterized in that, The first transition structure further includes a first trapezoidal soldering structure (61). The first coaxial probe (11) is connected to the microstrip line (3) through the first trapezoidal soldering structure (61).

4. A high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband according to claim 3, characterized in that The upper surface of the first trapezoidal soldering structure (61) is connected to the lower surface of the first coaxial probe (11). The lower surface of the first trapezoidal soldering structure (61) is connected to the dielectric substrate (4). The inclined surface of the first trapezoidal soldering structure (61) is connected to one end of the microstrip line (3).

5. The high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband according to claim 3, characterized in that By changing the height and width of the first trapezoidal soldering structure (61), broadband matching can be achieved within a tolerance range of ±50um.

6. A high-speed feeding circuit for realizing low-reflection transmission of intermediate-frequency signals within a wideband, as claimed in claim 1, wherein The material of the dielectric substrate (4) is one of rogers 5880 and rogers 3003.

7. A high-speed feeding circuit for achieving low-reflection transmission of intermediate-frequency signals within a wideband, according to any one of claims 1-6, characterized in that, It further includes a second transition structure symmetrically arranged with the first transition structure on the left and right. The second transition structure has the same structure as the first transition structure. The second transition structure connects the other end of the microstrip line (3) to a second coaxial connector (2).

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