JP6012220B2 - High frequency shield structure - Google Patents

Description

  The present invention relates to a high frequency shield structure for preventing radio wave leakage from a high frequency communication device mounted on a vehicle or the like.

  2. Description of the Related Art In recent years, sensors (high-frequency communication devices) that detect obstacles around a vehicle for driving assistance are known. In such a high-frequency communication device, leakage of unnecessary radio waves from the transmission / reception circuit on the surface of the high-frequency circuit board to the outside of the device, unnecessary radio waves jumping from the outside of the device to the transmission / reception circuit, and circuit components in the transmission / reception circuit Various shield structures are employed for the purpose of preventing unnecessary coupling and signal wraparound.

  Patent Document 1 discloses an exploded perspective view showing a configuration of a conventional high-frequency shield structure.

  As shown in Patent Document 1, in the high-frequency shield structure, the lower substrate and the upper substrate are provided with a number of holes at predetermined intervals at positions surrounding the high-frequency circuit. Metal pins are inserted into the holes provided in the lower and upper boards and the corresponding holes provided in the lower board, and the pins are electrically connected between the lower and upper boards. Has been. By setting the interval 1 between the pins and the interval L between the lower substrate and the upper substrate facing each other to λ / 4 or less, electromagnetic waves radiated from the high-frequency circuit to the surroundings are shielded by pins and the like, and radiated noise to the outside Leakage is prevented.

  Patent Document 2 discloses a cross-sectional view showing the configuration of another conventional high-frequency shield structure.

  In the high-frequency shield structure of Patent Document 2, the main circuit board and the sub circuit board are arranged with the shield plate interposed therebetween and are electrically connected by a flexible flat cable. In the state where the sub circuit board is assembled, the flexible flat cable is disposed in a state where the flexible flat cable is fixed to the shield plate by the double-sided tape, and the mountain folded portions A and C and the valley folded portion B are folded. Is done. The flexible flat cable is pressed against the shield plate and pressed in a state where the portion to which the shield material is attached is in contact with the shield plate, so that the shield material and the shield plate are electrically connected. Thereby, the radiation noise which generate | occur | produces from a flexible flat cable is reduced.

  Further, in recent years, in a high-frequency communication device such as an in-vehicle radar device, as shown in FIG. 7, a high-frequency circuit board 93 and a control circuit board 94 are opposed to each other in a housing 90 including an upper case 91 and a lower case 92. A configuration is employed in which these are arranged and connected by a board-to-board connector 96. In this configuration, the radiation noise is reduced by providing a shield case 95 that covers the high-frequency circuit board between the high-frequency circuit board 93 and the control circuit board 94 (FIG. 8).

JP 2001-284870 A JP 2007-31709 A

  However, in the conventional high-frequency communication devices as shown in Patent Document 1 and Patent Document 2, it is difficult to partition high-frequency circuits individually, and interference between high-frequency circuits is unavoidable. Further, Patent Document 1 does not specify a method for connecting signal lines between two circuit boards.

  In the conventional configuration in which the shield case and the board-to-board connector are connected as shown in FIG. 8, the radio wave radiated from the high-frequency circuit board leaks between the board-to-board connector and the shield case, and further propagates between the circuit boards. There is a problem of leaking outside. In addition, since the board-to-board connectors often have complicated shapes, radio waves are likely to be radiated from the connectors, and radio waves radiated from the board-to-board connectors propagate to the external connection connector and leak from the apparatus body to the outside. There is also a problem. Furthermore, in-vehicle radar devices need to keep the amount of radio wave leakage within a predetermined band below the standard value, but spurious is generated especially at the local oscillation frequency (quasi-millimeter band 10 to 30 GHz) and exceeds the specified value. Therefore, there is a demand to keep the radio wave leakage in these bands below the standard value.

  An object of the present invention is to provide a high frequency shield structure capable of suppressing leakage (radiation noise) of radio waves from the communication device main body to the outside in a configuration in which a control circuit board and a high frequency circuit board are connected by an inter-board connector. It is in.

In order to achieve the above object, a high-frequency shield structure according to the present invention is disposed between a casing, a high-frequency circuit board and a control circuit board accommodated in the casing, and the circuit board, and shields the high-frequency circuit board. A high-frequency shield structure provided in a high-frequency communication device including a shield case to be connected to and an inter-board connector that is inserted into an opening provided in the shield case and electrically connects the high-frequency circuit board and the control circuit board. Te, the high frequency shield structure, in conjunction with the opening is a cylindrical member which covers the mounting et Re且 one said inter-board connector to the shield case, one end of the tubular member abuts on the shield case and the other end to abut against the control circuit board, wherein the high frequency shield structure has a plurality of protrusions formed on an inner surface of the tubular member, the double Projections, along the axial direction of the tubular member, wherein are arranged at approximately lambda / 4 equally spaced high frequency wave emitted from the high-frequency circuit board and said Rukoto.

The cylindrical member is a rectangular tube having a substantially rectangular cross section, and the inner dimension of the wide side of the cylindrical member is set to be equal to or less than the cutoff wavelength of the high frequency wavelength λ emitted from the high frequency circuit board.

  The cylindrical member may be constituted by a cylindrical unit formed by connecting a plurality of annular members whose axial cross-sections are substantially L-shaped.

  The annular member has a convex portion at one end and a concave portion into which the convex portion of the other annular member is fitted at the other end, and the convex portion of one annular member is adjacent to the annular member. The said annular member may be formed by being inserted in the recessed part of another annular member.

  The cylindrical member is preferably joined to the shield case and the control circuit board by a fitting mechanism or solder.

  According to the present invention, the high-frequency shield structure is configured by a cylindrical member that is attached in connection with the opening of the shield case and covers the inter-board connector. One end of the cylindrical member abuts on the shield case, and the other end abuts on the control circuit board. Therefore, the radio wave (radiated noise) radiated from the high frequency circuit board does not leak from the opening of the shield case, and does not propagate between the high frequency circuit board and the control circuit board and leak outside. Further, since the board-to-board connector is shielded from the outside by the high-frequency shield structure, the radio wave radiated from the board-to-board connector does not leak to the outside from the high-frequency shield structure. Therefore, it is possible to suppress radio wave leakage from the communication device main body to the outside.

1 is an exploded perspective view schematically showing a configuration of a high-frequency communication device to which a high-frequency shield structure according to a first embodiment of the present invention is applied. It is sectional drawing which shows the internal structure of the high frequency communication apparatus of FIG. It is an expanded sectional view of the high frequency shield structure of FIG. It is sectional drawing which shows the structure of the high frequency shield structure which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the modification of the high frequency shield structure of FIG. It is sectional drawing which shows the other modification of the high frequency shield structure of FIG. It is a disassembled perspective view which shows the structure of the conventional high frequency shield structure. It is sectional drawing of the high frequency shield structure of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an exploded perspective view schematically showing a configuration of a high-frequency communication device to which the high-frequency shield structure according to the first embodiment is applied. As this high-frequency communication device, for example, a vehicle-mounted UWB (Ultra Wide Band) having a bandwidth of 450 MHz or more for detecting a small obstacle using a quasi-millimeter wave band (24 GHz, 26 GHz band) conforming to domestic and foreign radio wave regulations is used. Wireless system).

  In FIG. 1, the high-frequency communication device 1 includes a casing 10 composed of an upper case 11 and a lower case 12, a high-frequency circuit board 13 accommodated in the casing 10, a control circuit board 14, and a high-frequency circuit board 13. And a shield case 15 that is disposed between the control circuit board 14 and covers the entire surface of the high-frequency circuit board 13. An external connection connector 20 for transmitting a signal from the signal processing board 14 to an external device is attached to the side surface of the lower case 12.

  The shield case 15 is made of metal and shields radio waves radiated from high-frequency components mounted on the high-frequency circuit board 13 by being electrically connected to the GND of the high-frequency circuit board 13 and the control circuit board 14. Is possible. In addition, it is not limited to metal, and may be formed of a resin or elastomer having a radio wave absorption property, or a non-conductive material and having a conductive resin layer on the surface thereof.

  A board-to-board connector 16 is disposed between the high-frequency circuit board 13 and the control circuit board 14. An opening 17 is formed at a predetermined position of the shield case 15, and the inter-board connector 16 is inserted through the opening 17. A convex connector 16a is attached to the surface of the high-frequency circuit board 13, and a concave connector 16b is attached to the surface of the control circuit board 14, respectively. By connecting the convex connector 16a and the concave connector 16b, the above two The circuit board is electrically connected. The unevenness of the connector is an example, and a concave connector may be attached to the surface of the high-frequency circuit board 13 and a convex connector may be attached to the surface of the control circuit board 14.

  As shown in FIG. 2, the high-frequency shield structure 30 according to the present invention is attached between the high-frequency circuit board 13 and the control circuit board 14 so as to be connected to the opening 17 of the shield case 15. It is a metal substantially cylindrical member arrange | positioned so that it may cover. In a state where the high-frequency communication device 1 is assembled, one end of the high-frequency shield structure 30 is in contact with the shield case 15 and the other end is in contact with the control circuit board 14 and is electrically connected. Thereby, the space A defined by the high-frequency circuit board 13, the shield case 15, the high-frequency shield structure 30 and the control circuit board 14 is isolated from the outside, and the inter-board connector 16 is shielded from the outside by the high-frequency shield structure 30.

  FIG. 3 is an enlarged view of the high-frequency shield structure of FIG. 2, wherein (a) is a cross-sectional view and (b) is a plan view.

  3A and 3B, the high-frequency shield structure 30 is preferably a rectangular tube having a substantially rectangular cross section that covers the outer periphery of the inter-board connector 16, and one end 30a of the high-frequency shield structure 30 is a shield case. 15, and the other end 30 b is in contact with the control circuit board 14. Various methods can be used for the contact between the high-frequency shield structure 30 and the shield case 15 and the contact between the high-frequency shield structure 30 and the control circuit board 14, and preferably a fitting mechanism using an uneven shape, or Solder bonding is used. Thus, by eliminating the gap between the high-frequency shield structure 30 and the shield case 15 and eliminating the gap between the high-frequency shield structure 30 and the shield case 15, radio waves propagating in the high-frequency shield structure 30 can be transmitted to the shield structure. Leakage to the outside can be prevented.

  As the radio wave propagating in the high frequency shield structure 30, for example, a high frequency transmitted or radiated from the high frequency circuit board 13 or the inter-board connector 16 can be considered. The high-frequency shield structure 30 plays a role of suppressing the propagation of radio waves to the external connection connector 20 by preventing these high frequencies from leaking out of the shield structure.

ここで、Ｃ０は光速、ｍ，ｎはａ，ｂ方向の導波管モード数

式（２）を代入し、遮断波長λｃを求めると
λｃ＝２ａ ・・・（３）
と表される。そこで本実施形態では、高周波シールド構造３０の内寸の長辺ａが、高周波回路基板１３から放射される高周波波長λの１／２以下とすることが望ましい。換言すれば、高周波シールド構造３０における広幅辺の内寸をカットオフ波長以下とする。これにより、高周波回路基板１３あるいは基板間コネクタ１６から放射される高周波が、高周波シールド構造３０内で、送受信回路基板１３から制御回路基板１４に向かう方向に進行するのを防止することが可能となる。例えば、１２ＧＨｚのノイズの進行を防止したい場合、対象とするノイズの波長は２５ｍｍとなる。このとき、内寸の長辺ａの長さを波長の１／２である１２．５ｍｍ以下とすればよい。 Further, when this rectangular tube is assumed to be a rectangular waveguide, the cut-off frequency fc in the rectangular waveguide is expressed by the following equation, where a is the inner dimension of the long side and b is the inner dimension of the short side. It is represented by (1).

Here, C0 is the speed of light, and m and n are the number of waveguide modes in the a and b directions.

Substituting equation (2) to obtain the cutoff wavelength λc, λc = 2a (3)
It is expressed. Therefore, in this embodiment, it is desirable that the long side “a” of the internal dimension of the high-frequency shield structure 30 is not more than ½ of the high-frequency wavelength λ radiated from the high-frequency circuit board 13. In other words, the inner dimension of the wide side in the high-frequency shield structure 30 is set to be equal to or less than the cutoff wavelength. Thereby, it is possible to prevent the high frequency radiated from the high frequency circuit board 13 or the inter-board connector 16 from traveling in the direction from the transmission / reception circuit board 13 to the control circuit board 14 in the high frequency shield structure 30. . For example, when it is desired to prevent the progression of 12 GHz noise, the target noise wavelength is 25 mm. At this time, the length of the inner long side a may be set to 12.5 mm or less which is ½ of the wavelength.

  As described above, according to the present embodiment, the high-frequency shield structure 30 is configured by being connected to the opening 17 of the shield case 15 and configured by a cylindrical member that covers the inter-board connector 16. One end 30 a of the cylindrical member abuts on the shield case 15, and the other end 30 b abuts on the control circuit board 14. Therefore, the radio wave radiated from the high frequency circuit board 13 does not leak from the opening 17 of the shield case 15, and does not propagate between the high frequency circuit board 13 and the control circuit board 14 and leak outside. Further, since the board-to-board connector 16 is shielded from the outside by the high-frequency shield structure 30, radio waves radiated from the board-to-board connector 16 do not leak out from the high-frequency shield structure 30. Therefore, it is possible to suppress radio wave leakage from the main body of the high-frequency communication device 1 to the outside.

  FIG. 4 is a cross-sectional view showing the configuration of the high-frequency shield structure according to the second embodiment of the present invention. In the present embodiment, in relation to the dimensions of the board-to-board connector and other elements arranged in the vicinity of the board-to-board connector, when the inner dimension of the wide side in the high-frequency shield structure cannot be made equal to or less than the cutoff wavelength, It suppresses the propagation of radio waves in the connector fitting direction of the high frequency shield structure.

  In FIG. 4, the high-frequency shield structure 40 is a cylindrical member having a substantially rectangular cross section that covers the outer periphery of the inter-board connector 16. The high-frequency shield structure 40 has a plurality of protrusions 42 on its inner surface 41, and preferably, the plurality of protrusions 42 are formed on the four inner surfaces of the high-frequency shield structure 40. The plurality of protrusions 42 are arranged at equal intervals of approximately λ / 4 of the high frequency wavelength radiated from the high frequency circuit board 13 along the axial direction of the cylindrical member.

  That is, by forming an uneven structure (periodic structure) inside the high-frequency shield structure 40 and changing the high-frequency wave impedance radiated from the high-frequency circuit board 13, high isolation at a high-frequency frequency can be obtained. It becomes possible. Therefore, according to this configuration, propagation of radio waves in the connector fitting direction of the high frequency shield structure 40 can be suppressed, and leakage of radio waves from the main body of the high frequency communication device 1 to the outside can be suppressed.

  5 and 6 are cross-sectional views showing modifications of the high-frequency shield structure.

  The high-frequency shield structure 40 in FIG. 4 is an integrally formed cylindrical member, but the high-frequency shield structure 50 in FIG. 5 is a cylinder formed by connecting a plurality of annular members 51 whose axial cross-sections are substantially L-shaped. It consists of a shape unit.

  The annular member 51 has a protrusion 53 on its inner surface 52. By connecting a plurality of annular members 51 to form a cylindrical unit, an uneven structure is formed on the inner surface of the cylindrical unit. According to this configuration, since metal processing can be easily performed, the high-frequency shield structure 50 can be easily manufactured, and the cost can be reduced.

  Also, the high-frequency shield structure 60 shown in FIGS. 6A and 6B is a tube formed by connecting a plurality of annular members 61 whose axial cross-sections are substantially L-shaped, like the high-frequency shield structure 50 described above. It consists of a shape unit. A projection 63 is formed on the inner surface 62 of the annular member 61, similar to the annular member 51.

  The annular member 61 has a convex portion 64 at one end portion and a concave portion 65 at the other end portion. The annular member 61 is formed by fitting the convex portion of one annular member into the concave portion of another adjacent annular member. In this configuration, when the plurality of annular members 61 are stacked, the contact surfaces of the adjacent annular members 61 are not a single plane in the radial direction but a stepped plane. Thereby, it is possible to suppress radio wave leakage from the contact surfaces of the adjacent annular members 61. Moreover, since the annular members 61 can be easily joined together, the high-frequency shield structure 60 can be easily manufactured.

  In the above-described embodiment, the high-frequency shield structure is a cylindrical member having a substantially rectangular cross section, but is not limited thereto, and may be a cylindrical member having a substantially circular cross section. Also in this case, it is possible to suppress the progress of the radio wave in the cylinder by designing the inner dimension of the cylinder to be equal to or less than the cutoff wavelength.

  The high-frequency shield structure is formed of metal, but is not limited to this, and may be formed of a resin or elastomer having radio wave absorptivity or a non-conductive material having a conductive resin layer on the surface thereof. Good.

  In this case, the adhesion between the high-frequency shield structure and the shield case or the control circuit board can be improved, and the weight can be reduced as compared with the metal high-frequency shield structure. Moreover, metal processing is not required, and cost can be reduced by integrally molding the high-frequency shield structure with a molding machine or the like.

  As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.

DESCRIPTION OF SYMBOLS 1 High frequency communication apparatus 10 Case 11 Upper case 12 Lower case 13 High frequency circuit board 14 Control circuit board 15 Shield case 20 External transmission connector 17 Opening part 16 Inter-board connector 16a Convex connector 16b Concave connector 30 High frequency shield structure 30a, 30b End 40 High-frequency shield structure 41 Inner surface 42 Projection 50 High-frequency shield structure 51 Annular member 52 Inner surface 53 Projection 60 High-frequency shield structure 61 Annular member 62 Inner surface 63 Protrusion 64 Convex portion 65 Concave portion

Claims (5)

A housing, a high-frequency circuit board and a control circuit board housed in the housing, a shield case disposed between the circuit boards and shielding the high-frequency circuit board, and an opening provided in the shield case A high-frequency shield structure provided in a high-frequency communication device comprising an inter-board connector for electrically connecting the high-frequency circuit board and the control circuit board,
The high frequency shielding structure is a tubular member which covers the mounting et Re且 one said inter-board connector to the shield case and connected to the opening,
One end of the tubular member abuts the shield case and the other end to abut against the control circuit board,
The high-frequency shield structure has a plurality of protrusions formed on the inner surface of the cylindrical member,
Wherein the plurality of projections along the axial direction of the tubular member, the high frequency shield structures characterized by Rukoto arranged at approximately lambda / 4 equally spaced high frequency wave emitted from the high-frequency circuit board. The cylindrical member is a rectangular tube having a substantially rectangular cross section,
The high-frequency shield structure according to claim 1, wherein an inner dimension of the wide side of the cylindrical member is equal to or less than a cutoff wavelength of a high-frequency wavelength λ radiated from the high-frequency circuit board. The tubular member is characterized in that the axial cross-section is composed of a cylindrical unit formed by connecting a plurality of annular members are substantially L-shaped, high-frequency shielding structure of claim 1, wherein. The annular member has a convex portion at one end and a concave portion into which the convex portion of the other annular member is fitted at the other end.
The high-frequency shield structure according to claim 3 , wherein the annular member is formed by fitting a convex portion of one annular member into a concave portion of another adjacent annular member. It said tubular member, the fitting mechanism or solder, characterized in that it is joined to the shield case and the control circuit board, high frequency shield structure according to any one of claims 1 to 4.

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