High-frequency transmission structure

Abstract

To provide a high frequency transmission structure capable of transmitting a high frequency signal by utilizing a connector of a general-purpose non-coaxial structure.SOLUTION: A high frequency transmission device 1 comprises: a multilayer substrate 3 in which a connector 2 is mounted in a first layer; a microstrip line 41 which is provided in the first layer and of which one end is connected to an input connector mounting land; a coplanar line 42 of which one end is connected to the microstrip line 41 and the other end is defined as an output end; an impedance matching element 5 connected to the coplanar line 42 at a position closer to the side of the microstrip line 41; a mat ground pattern provided in a layer of the multilayer substrate 3 lower than the first layer; and a hollow part which is provided between the first layer of the multilayer substrate 3 and the layer including the mat ground pattern and in which a copper foil is not provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high frequency transmission structure for transmitting high frequency signals between a daughter board and a backplane, for example. [Background technology]

[0002] An electronic device whose functions can be expanded or changed includes a daughterboard that is inserted into or removed from a housing, and a backplane that is disposed on the rear surface of the housing and connects to the daughterboard. The daughterboard and backplane are connected via a connector. Among such electronic devices, a wireless communication device transmits high-frequency signals between the daughterboard and the backplane. Generally, a coaxial connector is used to transmit high-frequency signals between boards (see, for example, Patent Document 1). In particular, a high-density multi-type coaxial connector that can be fitted with multiple coaxial contacts (for example, the CJ2 series coaxial connector by Japan Aviation Electronics Industry, Ltd.) is used between the daughterboard and backplane of a wireless communication device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 3-79511 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, production of high-density multi-type coaxial connectors has been declining due to declining demand, making stable supply difficult. While alternative coaxial connectors exist, their specifications are excessive and expensive for use in wireless communication devices.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a high-frequency transmission structure that is capable of transmitting high-frequency signals using a general-purpose connector with a non-coaxial structure. [Means for solving the problem]

[0006] In order to solve the above problem, the invention described in claim 1 is a high-frequency transmission structure for transmitting a high-frequency signal input to a connector having a non-coaxial structure, the connector comprising: Impedance matching circuit and coaxial connector attached to a first layer of a multilayer substrate; and The connector has a number of terminals, each of which is inserted into a connector mounting land. one end is connected a microstrip line connected to the first layer, and a microstrip line provided on the first layer, one end of which is connected to the microstrip line; The other end of the first terminal is connected to the impedance matching circuit. A coplanar line, a second coplanar line provided on the first layer, one end of which is connected to the impedance matching circuit and the other end of which is connected to the coaxial connector; a solid ground pattern that is provided in a layer below the first layer of the multilayer substrate and that constitutes the microstrip line; and a cutout portion where copper foil is removed, that is provided in a layer between the first layer of the multilayer substrate and the layer on which the solid ground pattern is provided. the impedance matching circuit is connected between the first coplanar line and the second coplanar line, and the recessed portion is provided at a position corresponding to the microstrip line of the first layer. It is characterized by:

[0007] The invention described in claim 2 is characterized in that, in the high-frequency transmission structure described in claim 1, the microstrip line is wired so as to pass between the multiple connector mounting lands. [Effects of the Invention]

[0008] According to the invention of claim 1, a high-frequency signal input to a non-coaxial connector is transmitted via a microstrip line and a coplanar line, and impedance is matched by a cutout in a multilayer substrate and an impedance matching circuit. This makes it possible to transmit high-frequency signals with low reflection loss and low insertion loss using a general-purpose non-coaxial connector that is inexpensive and readily available.

[0009] Furthermore, according to the invention described in claim 2, since the microstrip line is routed between a plurality of connector mounting lands, there is no need to provide a space on the multilayer substrate just for forming the microstrip line, which makes it possible to miniaturize the high frequency transmission structure. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are a plan view and a side view of a high-frequency transmission device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view showing the layer structure within the rectangular frame of the multilayer substrate shown in FIG. [Figure 3] 3 is a plan view showing patterns of the first, second and third layers of the multilayer substrate shown in FIG. 2. FIG. [Figure 4] 1 is a graph showing the reflection loss and insertion loss on the input side, which are the transmission characteristics of a high-frequency transmission device. [Figure 5] 10 is a graph showing the insertion loss and return loss on the output side, which are the transmission characteristics of a high-frequency transmission device. [Figure 6] 10 is a graph showing VSWR values ​​of return loss on the input side and return loss on the output side, which are transmission characteristics of a high-frequency transmission device. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on the illustrated embodiments.

[0012] 1 to 6 show a high-frequency transmission structure according to an embodiment of the present invention, and Fig. 1(A) and (B) show a plan view and a side view of a high-frequency transmission device 1 using the high-frequency transmission structure according to the present invention. The high-frequency transmission device 1 is connected, for example, between a daughter board and a backplane of a wireless communication device, and is a device for transmitting high-frequency signals in the UHF band.

[0013] The high-frequency transmission device 1 includes a non-coaxial connector 2 to which a high-frequency signal is input, a multilayer substrate 3 to which the connector 2 is attached, a transmission line 4 provided on the multilayer substrate 3, an impedance matching element (impedance matching circuit) 5 attached to the multilayer substrate 3, and a coaxial connector 6 that outputs the high-frequency signal.

[0014] The connector 2 is, for example, a hard metric connector with a terminal pitch of 2 mm that complies with the industry standard "IEC 61076-4-101." The connector 2 is connected to, for example, a connector provided on a daughter board, and high-frequency signals are input from the daughter board. This type of non-coaxial connector 2 is unsuitable for transmitting high-frequency signals, and has not traditionally been used to connect a daughter board and a backplane of a wireless communication device.

[0015] The multilayer substrate 3 is a printed circuit board in which multiple insulating substrates and copper foils are laminated, and circuit patterns can be formed on the copper foil of the inner layers. The connector 2, impedance matching element 5, and coaxial connector 6 are attached to the first layer, which is the top layer of the multilayer substrate 3.

[0016] The transmission line 4 is provided on the first layer of the multilayer substrate 3, and transmits a high-frequency signal input from the daughter board via the connector 2 to the backplane via the coaxial connector 6. The transmission line 4 includes a microstrip line 41 provided in the mounting portion of the connector 2, and a coplanar line 42 connecting the microstrip line 41 and the coaxial connector 6.

[0017] The impedance matching element 5 is an element equipped with a circuit that matches the impedance of a high-frequency signal transmitted by the transmission line 4. The impedance matching element 5 is connected between one end (the microstrip line 41 side) and the other end (the coaxial connector 6 side, which is the output end) of the coplanar line 42. In order to quickly match the impedance of a high-frequency signal input to the connector 2, the impedance matching element 5 is arranged closer to the microstrip line 41 side than the other end side.

[0018] 2 shows the layer structure of the multilayer substrate 3 in the portion indicated by the dashed rectangular frame C in the side view of Fig. 1(A). The multilayer substrate 3 includes, as copper foil layers, a first layer 31 on which the transmission line 4 is formed, a second layer 32 formed below the first layer 31 with an insulating substrate 3a sandwiched therebetween, and a third layer 33 formed below the second layer 32 with an insulating substrate 3b sandwiched therebetween.

[0019] A transmission line 4 is formed on the first layer 31. A cutout 8 is provided on the second layer 32, where the copper foil has been removed. Note that the cutout 8 is actually filled with prepreg, filler, or the like. A solid ground pattern 9 that constitutes a microstrip line 41 is provided on the third layer 33. The cutout 8 is provided to adjust the distance between the transmission line 4 and the solid ground pattern 9 and to match the impedance of the transmission line 4 to a predetermined level (for example, about 50 Ω).

[0020] 3A, 3B, and 3C show plan views of the patterns provided on the first layer 31, the second layer 32, and the third layer 33 of the multilayer substrate 3, respectively. The first layer 31 is provided with a solid ground pattern 31a covering substantially the entire area. Furthermore, connector mounting lands 31b into which numerous terminals of the connector 2 are inserted and connected are provided at positions on the first layer 31 where the connector 2 is to be attached. Of these connector mounting lands 31b, only the input connector mounting land 31c, which is provided approximately in the center of the numerous connector mounting lands 31b, receives high-frequency signals from the daughter board. Therefore, the connector mounting lands 31b other than the input connector mounting land 31c are connected to the solid ground pattern 31a.

[0021] A microstrip line 41 is connected to the input connector mounting land 31c on the first layer 31. This microstrip line 41 is routed so as to pass between the multiple connector mounting lands 31b. Therefore, there is no need to provide a space on the multilayer substrate 3 that is necessary just for forming the microstrip line 41, and the high-frequency transmission device 1 can be made smaller.

[0022] At the end of microstrip line 41, coplanar line 42 is formed, with two slots provided between it and solid ground pattern 31a. Coplanar line 42 is divided at a position close to microstrip line 41 to connect to impedance matching element 5, forming first coplanar line 42a on the microstrip line 41 side and second coplanar line 42b on the coaxial connector 6 (output end) side. Second coplanar line 42b is connected to mounting land 31d of coaxial connector 6.

[0023] A solid ground pattern 32a is provided over substantially the entire second layer 32. Furthermore, at positions on the second layer 32 where the connector 2 is attached, connector mounting lands 32b and input connector mounting lands 32c are provided at positions corresponding to the connector mounting lands 31b and input connector mounting lands 31c on the first layer 31. Furthermore, a cutout 8a is provided on the second layer 32 at a position corresponding to the microstrip line 41 on the first layer 31. Furthermore, cutouts 8b and 8cf are provided on the second layer 32 at positions corresponding to the first coplanar line 42a and second coplanar line 42b on the first layer 31.

[0024] A solid ground pattern 33a is provided over substantially the entire area of ​​the third layer 33. Furthermore, at positions on the third layer 33 where the connector 2 is attached, connector mounting lands 33b and input connector mounting lands 33c are provided at positions corresponding to the connector mounting lands 31b and input connector mounting lands 31c on the first layer 31. Furthermore, the third layer 33 has solid ground pattern 33a (corresponding to solid ground pattern 9 in FIG. 2) at positions corresponding to the microstrip line 41 on the first layer 31 and at positions corresponding to the first coplanar line 42a and second coplanar line 42b.

[0025] 4 and 5 are graphs showing the S-parameter (scattering parameters) of the input return loss S11 and insertion loss S12, and the output insertion loss S21 and return loss S22, as the transmission characteristics of the high-frequency transmission device 1. Furthermore, FIG. 6 is a graph showing the VSWR (Voltage Standing Wave Ratio) values ​​of the input return loss S11 and the output return loss S22. These graphs show the transmission characteristics S1 of the high-frequency transmission device 1 of this embodiment, as well as the transmission characteristics of six types of high-frequency transmission devices, including a case where the cutout between the transmission line 4 and the solid ground pattern 9 is three-layered, a case where the cutout is five-layered, and a case where the cutout is one-layered, three-layered, and five-layered and the coaxial connector 6, which serves as the output terminal, is provided on the back surface of the multilayer substrate 3 (the surface opposite the connector 2).

[0026] 4 to 6, the high-frequency transmission device 1 of this embodiment can transmit high-frequency signals with reflection loss and insertion loss reduced to the same extent as that of conventional coaxial connectors. Furthermore, when the number of cutouts is set to three or five layers, even when the output coaxial connector 6 is placed on the back surface of the multilayer substrate 3, the transmission characteristics do not deteriorate significantly, and it is therefore possible to adjust the distance between the transmission line 4 and the solid ground pattern 9 according to the layer configuration of the multilayer substrate used.

[0027] As described above, according to the high-frequency transmission device 1 of this embodiment, a high-frequency signal input to the non-coaxial connector 2 is transmitted via the microstrip line 41 and the coplanar line 42, and impedance matching is performed by the cutout 8 in the multilayer substrate 3 and the impedance matching element 5. This makes it possible to transmit a high-frequency signal with small reflection loss and insertion loss using the inexpensive, readily available, general-purpose non-coaxial connector 2.

[0028] Furthermore, according to the high-frequency transmission device 1 of this embodiment, the microstrip line 41 is wired to pass between the multiple connector attachment lands 31b, so there is no need to provide a space on the multilayer substrate 3 that is necessary just for forming the microstrip line 41. Therefore, the high-frequency transmission device 1 can be made smaller.

[0029] In the above embodiment, the high frequency transmission structure of the present invention is described as a high frequency transmission device provided on one multilayer substrate, but the high frequency transmission structure may be incorporated into a backplane or the like.

[0030] Although many of the connector mounting lands 31b into which the terminals of the connector 2 are inserted are connected to the solid ground pattern 31a and are not used, some of the connector mounting lands 31b may be used for transmitting signals that do not affect the transmission of high-frequency signals, such as transmitting power signals, etc. This allows the connector 2 to be used not only for inputting high-frequency signals but also as a connector for supplying power. [Explanation of symbols]

[0031] 1. High frequency transmission device 2 connectors 3 Multilayer board 31 1st layer 32 2nd layer 33 3rd layer 4 Transmission Lines 41 Microstrip Line 42 Coplanar line 5 Impedance matching element (impedance matching circuit) 6 Coaxial Connectors 8 Hollowed-out section 9 Solid ground pattern

Claims

1. A high-frequency transmission structure for transmitting a high-frequency signal input to a non-coaxial connector, a multilayer substrate on which the connector, the impedance matching circuit, and the coaxial connector are attached to a first layer; a microstrip line provided on the first layer of the multilayer substrate, the microstrip line having one end connected to a connector mounting land into which a number of terminals of the connector are inserted; a first coplanar line provided on the first layer, one end of which is connected to the microstrip line and the other end of which is connected to the impedance matching circuit; a second coplanar line provided on the first layer, one end of which is connected to the impedance matching circuit and the other end of which is connected to the coaxial connector; a solid ground pattern that is provided in a layer below the first layer of the multilayer substrate and that constitutes the microstrip line; a cutout portion formed by removing copper foil, the cutout portion being provided in a layer between the first layer of the multilayer board and a layer on which the solid ground pattern is provided; Equipped with the impedance matching circuit is connected between the first coplanar line and the second coplanar line; the cutout portion is provided at a position corresponding to the microstrip line of the first layer. A high frequency transmission structure characterized by:

2. the microstrip line is wired to pass between the plurality of connector mounting lands; 2. The high frequency transmission structure according to claim 1.

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