CN106252808B

CN106252808B - Radio frequency coaxial microstrip structure

Info

Publication number: CN106252808B
Application number: CN201610805315.2A
Authority: CN
Inventors: 赵会臣; 张红伟
Original assignee: Shenzhen Sunway Communication Co Ltd
Current assignee: Shenzhen Sunway Communication Co Ltd
Priority date: 2016-09-06
Filing date: 2016-09-06
Publication date: 2022-05-27
Anticipated expiration: 2036-09-06
Also published as: CN106252808A

Abstract

The invention discloses a radio frequency coaxial microstrip structure, which comprises a coaxial outer conductor, a coaxial inner conductor and a PCB, wherein a microstrip line is arranged on the PCB, a transition structure is also arranged on the PCB, the transition structure comprises a first connecting part and a second connecting part, the first connecting part is connected with the coaxial inner conductor, and the second connecting part is connected with the microstrip line. The transition structure is arranged between the coaxial inner conductor and the microstrip line without using an RF connector, so that the test cost and the manufacturing process are effectively reduced, the transition structure can be used in electronic communication equipment to replace an RF wiring on a PCB, and the internal radio frequency interference of the PCB is reduced.

Description

Radio frequency coaxial microstrip structure

Technical Field

The invention relates to the technical field of radio frequency coaxial microstrip connection, in particular to a radio frequency coaxial microstrip structure.

Background

The radio frequency coaxial microstrip connector has the characteristics of simple operation, easy maintenance, excellent electrical performance, flexible use in occasions with limited space and the like, and is widely applied to the fields of optical communication equipment, measuring equipment, wireless equipment, radio frequency modules and the like. The radio frequency coaxial microstrip connector plays a key role in radio frequency signal transmission and is the only path for connecting the antenna and the mainboard, so the standing-wave ratio of the connection mode of the coaxial line and the mainboard becomes a key factor for restricting the quality of radio frequency signals, the sensitivity of an antenna system can be influenced by the superposition of the quality of radio frequency parameters, and therefore, in practical application, in order to reduce the connection reflection among different transmission lines, a special connector is used, and the cost is higher.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a radio frequency coaxial microstrip structure is provided that does not use a radio frequency coaxial microstrip connector.

In order to solve the technical problems, the invention adopts the technical scheme that: the utility model provides a coaxial microstrip structure of radio frequency, includes coaxial outer conductor, coaxial inner conductor and PCB board, be equipped with the microstrip line on the PCB board, still be equipped with transition structure on the PCB board, transition structure includes first connecting portion and second connecting portion, coaxial inner conductor is connected to first connecting portion, the microstrip line is connected to second connecting portion.

Further, the transition structure is square.

Further, the transition structure is T-shaped.

Further, the coaxial inner conductor is welded to the first connection portion.

Further, the coaxial outer conductor is welded on the PCB.

Furthermore, the PCB board is a double-layer PCB board, and the thickness of copper on the surface layer and the bottom layer is 1 Oz.

The invention has the beneficial effects that: a transition structure is arranged between the coaxial inner conductor and the microstrip line without using an RF connector, so that the test cost and the manufacturing process are effectively reduced, and the transition structure can be used in electronic communication equipment to replace an RF wiring on a PCB and reduce the internal radio frequency interference of the PCB.

Drawings

FIG. 1 is a perspective view of a radio frequency coaxial microstrip structure of the present invention;

FIG. 2 is a top view 1 of a radio frequency coaxial microstrip structure according to the present invention;

FIG. 3 is a diagram of a return loss test result of S-parameters of a T-shaped transition structure according to an embodiment of the present invention;

FIG. 4 is a graph of S-parameter insertion loss test results for a T-shaped transition structure according to an embodiment of the present invention;

FIG. 5 is a graph showing VSWR characteristics of a T-shaped transition structure according to an embodiment of the present invention;

FIG. 6 is a characteristic curve diagram of a TDR Impedance of a T-shaped transition structure according to an embodiment of the present invention;

FIG. 7 is a top view 2 of a radio frequency coaxial microstrip structure according to the present invention;

FIG. 8 is a plot of the VSWR characteristics of a two-square transition structure in accordance with an embodiment of the present invention;

FIG. 9 is a TDR Impedance characteristic curve diagram of a second square transition structure according to an embodiment of the present invention;

description of reference numerals:

1. feeding electricity coaxially; 2. a coaxial outer conductor; 3. a coaxial inner conductor; 4. a PCB board; 5. a microstrip line; 6. a transition structure; 7. a first connection portion; 8. a second connecting portion; 9. an RF connector.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

The most key concept of the invention is as follows: a transition structure is arranged between the coaxial inner conductor and the microstrip line, and an RF connector is not used, so that the test cost and the manufacturing process can be effectively reduced.

Referring to fig. 1, 2 and 7, a radio frequency coaxial microstrip structure includes a coaxial outer conductor, a coaxial inner conductor and a PCB board, the PCB board is provided with a microstrip line, the PCB board is further provided with a transition structure, the transition structure includes a first connection portion and a second connection portion, the first connection portion is connected to the coaxial inner conductor, and the second connection portion is connected to the microstrip line.

From the above description, the beneficial effects of the present invention are: the transition structure is arranged between the coaxial inner conductor and the microstrip line without using an RF connector, so that the test cost and the manufacturing process can be effectively reduced, and the transition structure can be used in electronic communication equipment to replace an RF wiring on a PCB and reduce the internal radio frequency interference of the PCB.

Further, the transition structure is square.

Further, the transition structure is T-shaped.

As can be seen from the above description, the transition structure may be designed to be square or T-shaped, and when the transition structure is T-shaped, the compatibility between the signal line and the return path may be increased, and the impedance of the transition region may be effectively reduced.

Further, the coaxial inner conductor is welded to the first connection portion.

As can be seen from the above description, the coaxial inner conductor can be soldered directly to the transition structure without the use of a special connector.

Further, the coaxial outer conductor is welded on the PCB.

Example one

Referring to fig. 1 to 6, a first embodiment of the present invention is: as shown in fig. 1, a radio frequency coaxial microstrip structure includes a coaxial feed 1 and a PCB board 4. As shown in fig. 2, the coaxial feed 1 includes a coaxial outer conductor 2 and a coaxial inner conductor 3, a microstrip line 5 is disposed on the PCB 4, a transition structure 6 is further disposed on the PCB 4, the transition structure 6 includes a first connection portion 7 and a second connection portion 8, the first connection portion 7 is connected to the coaxial inner conductor 3, the second connection portion 8 is connected to the microstrip line 5, and the other end of the microstrip line 5 is connected to the male end of the RF connector 9. In this embodiment, the transition structure 6 is T-shaped, the smaller end of the T-shaped structure is connected to the microstrip line 5, the coaxial inner conductor 3 is directly welded to the first connection portion 7, and the coaxial outer conductor is directly welded to the PCB 4. The PCB 4 was 8mm by 0.6mm in size, the substrate was conventional FR4, the dielectric constant was 4.2, the loss tangent angle was 0.016, and the top and bottom copper thicknesses were 1 Oz. In this embodiment, the transition from the coaxial feed 1-turn microstrip line 5 to the male end of the RF connector 9 is completed through the double-layer PCB 4.

In this embodiment, the performance of the T-shaped transition structure is tested, as shown in fig. 3, which is a result of S-parameter return loss test in this embodiment, and it can be seen from the figure that S11 and S22 reach below-17 dB at a frequency range of 0-6GHz, and have better return loss. As shown in FIG. 4, the insertion loss test results of this embodiment show that S21 and S12 are both in the range of-0.25, and have better insertion loss. As shown in FIG. 5, for the standing wave ratio VSWR characteristic curve, the maximum value at 6GHz is 1.3203, which is much smaller than the RFcable specification Max VSWR 1.45@0-6GHz, and it can be seen from the standing wave ratio characteristic that the T-shaped transition effectively reduces the reflection when the PCB board 4 is coaxially connected. As shown in fig. 6, which is a TDR Impedance characteristic curve, when the coaxial feed 1 is transferred to the PCB 4, the Impedance of the thinner coaxial inner conductor 3 directly soldered to the trace pad of the PCB 4 is higher, the transition structure 6 is added, the compatibility of the signal line and the return path is increased, the Impedance of the transition region is effectively reduced, and the Impedance is stabilized below 50 ohms, the Impedance at the lowest point in the diagram is the Impedance at the RF connector 9, and the Impedance characteristic is inevitably smaller, which meets the characteristic specification of 50+/-5 ohms. In this embodiment, the size of the transition structure 6 is determined by the size of the male portion of the RF connector 9.

Example two

Referring to fig. 7 to 9, a second embodiment of the present invention is shown, and the difference between the second embodiment and the first embodiment is that, as shown in fig. 7, the transition structure 6 in the present embodiment is square. Fig. 8 shows the standing wave ratio VSWR characteristic curve of the present embodiment, which has a maximum value of 1.70 at 0-6GHz, which is slightly larger than the predetermined maximum value of 1.45, and fig. 8 shows the TDR Impedance characteristic curve, which shows that the Impedance rapidly increases at the time of transition, and the Impedance matching is not as good as that of the T-shaped transition structure.

Compared with the first embodiment and the second embodiment, the impedance matching of the T-shaped transition structure is better than that of the square transition structure, and the practical application value is better. The reason for this is that the impedance value Z at the transition junction is about √ L/C, L being determined mainly by the diameter of the coaxial inner conductor and cannot be changed any more; the transition point capacitance C is determined by the parallel area of the signal line at the welding position and the signal return path, and the capacitance C can be effectively increased when the distance is shorter and the parallel area is larger. Since the diameter of the coaxial inner conductor is far away from GND at the initial bending part, L is large, and C is effectively increased by adding the T-shaped transition structure, so that 50 ohm matching of Z is guaranteed. The square transition structure only ensures 50 ohm impedance of the microstrip line in the PCB, and does not consider that large inductance L is generated when the microstrip line is connected with the coaxial inner conductor, so that the square transition structure can generate impedance larger than 50 ohm, and the impedance matching performance is poor.

In summary, the radio frequency coaxial microstrip structure provided by the present invention includes a coaxial outer conductor, a coaxial inner conductor, and a PCB, where the PCB is provided with a microstrip line, and the PCB is further provided with a transition structure, where the transition structure includes a first connection portion and a second connection portion, the first connection portion is connected to the coaxial inner conductor, and the second connection portion is connected to the microstrip line. The transition structure is arranged between the coaxial inner conductor and the microstrip line without using an RF connector, so that the test cost and the manufacturing process are effectively reduced, the transition structure can be used in electronic communication equipment to replace RF wiring on a PCB, and the internal radio frequency interference of the PCB is reduced; the shape of the transition structure can be designed according to the requirement, and when the transition structure is in a T shape, the impedance matching is better than that of a square transition structure.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention and the contents of the accompanying drawings, which are directly or indirectly applied to the related technical fields, are included in the scope of the present invention.

Claims

1. A radio frequency coaxial microstrip structure comprises a coaxial outer conductor, a coaxial inner conductor and a PCB, wherein the PCB is provided with a microstrip line, and the radio frequency coaxial microstrip structure is characterized in that the PCB is also provided with a transition structure, the transition structure comprises a first connecting part and a second connecting part, the first connecting part is connected with the coaxial inner conductor, the second connecting part is connected with the microstrip line, the coaxial inner conductor is welded on the first connecting part, the transition structure is T-shaped, the width of the first connecting part is greater than that of the second connecting part, and the width of the second connecting part is greater than that of the coaxial inner conductor; the PCB is a double-layer PCB, and the copper thickness of the surface layer and the copper thickness of the bottom layer are both 1 Oz.

2. The radio frequency coaxial microstrip structure of claim 1 wherein the coaxial outer conductor is soldered to the PCB board.