JP6437779B2 - Circuit board - Google Patents

Description

  The present invention relates to a circuit board.

  For example, in a radar or communication device using millimeter waves, a transmission line is required to connect the transmission / reception antenna and the millimeter wave oscillation circuit. Therefore, there is a transmission line provided on a circuit board.

  As such a circuit board, there is one in which a desired high-frequency circuit is configured by connecting a substrate forming a microstrip line and a substrate forming a strip line. Further, for example, FIG. 5 of Patent Document 1 discloses a circuit board in which substrates of different types are stacked and connected to each other.

Special table 2012-521716 gazette

As described above, when a circuit board is configured by connecting a substrate that forms a microstrip line and a substrate that forms a stripline, reflection occurs due to impedance mismatch at the line change point between the microstripline and the stripline. There is a problem that the transmission efficiency is lowered.
Furthermore, when the reflected wave at the changing point of the line is large, the reflected wave interferes with the incident wave, and a standing wave (resonance) is generated or ringing (signal distortion) is generated. In addition, noise is increased at the resonance frequency from the viewpoint of electromagnetic compatibility, and resonance in the transmission line is not preferable for correctly transmitting the waveform of the digital signal.

  Accordingly, an object of the present invention is to suppress the occurrence of reflection in a circuit board configured by connecting a microstrip line and a strip line.

  The circuit board of the present invention is provided on the other side of the first substrate portion, the first ground made of a conductive foil provided on one surface of the first substrate portion, and the first substrate portion. A microstrip line having a first line made of a linear conductor foil, a second substrate portion provided side by side with the first substrate portion, and the same side as the first ground among the second substrate portions. A second ground made of a conductive foil provided on one side surface, a third ground made of a conductive foil provided on the other side surface of the second substrate part, and an inside of the second substrate part A strip line having a second line made of a linear conductor foil, and a circuit board in which the first line and the second line are connected to form one line. The strip line has the third group. The second line and the overlapping portion of the command, notches opening at the boundary side of the microstrip line is provided.

  According to the present invention, the notch provided in the third ground of the stripline can alleviate impedance mismatch at the change point of the line between the microstripline and the stripline. Can be suppressed.

  Moreover, it is preferable that the said notch has a part from which the space | interval becomes large as it goes to the opening side. In this case, reflection caused by impedance mismatching at the change point of the line can be more effectively suppressed.

  According to the present invention, impedance mismatch at the changing point of the line between the microstrip line and the strip line can be alleviated, and the occurrence of reflection can be suppressed. As a result, loss is reduced and transmission efficiency can be improved.

It is a top view which shows one Embodiment of the circuit board of this invention. It is a cross-sectional view of the circuit board shown in FIG. It is sectional drawing of the circuit board shown in FIG. It is sectional drawing of the circuit board shown in FIG. It is a rear view of the circuit board shown in FIG. It is explanatory drawing of a notch part. It is a simulation result about the amount of reflection and the amount of permeation in a circuit board. It is a simulation result about the transmission amount in a circuit board. It is a simulation result about the amount of reflection in a circuit board. It is a simulation result about the transmission amount in a circuit board. It is explanatory drawing explaining the modification of a notch part. It is explanatory drawing explaining another modification of a notch part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The circuit board 1 of the present invention is a board having a transmission path for connecting a (transmission / reception) antenna and a (millimeter wave) oscillation circuit, for example, used in a radar or communication device using millimeter waves. In the circuit board 1 described below, the use frequency band is 60 GHz.

  FIG. 1 is a plan view showing an embodiment of a circuit board 1 of the present invention. FIG. 2 is a cross-sectional view of the circuit board 1 shown in FIG. FIG. 3 is a cross-sectional view of the circuit board 1 shown in FIG. FIG. 4 is a cross-sectional view of the circuit board 1 shown in FIG. The circuit board 1 is composed of a single board, and has a microstrip line 2 and a strip line 3 on the single board. Here, the microstrip line 2 side is the input side, and the strip line 3 side is the output side.

The microstrip line 2 includes a first substrate portion 10, a first ground 12 made of a conductive foil provided on one surface 10 a of the first substrate portion 10, and a surface 10 b on the other side of the first substrate portion 10. The first line 11 made of a linear conductor foil is provided to form a transmission line for transmitting high frequencies.
The strip line 3 includes the second substrate portion 20, the second ground portion 22 made of a conductive foil provided on one surface 20 a of the second substrate portion 20 on the same side as the first ground 12, and the second substrate portion. 20 has a third ground 23 made of a conductor foil provided on the other surface 20 b of the substrate 20 and a second line 21 made of a linear conductor foil provided inside the second substrate portion 20. And constitutes a transmission path for transmitting high frequencies.
And in this circuit board 1, the 1st track | line 11 and the 2nd track | line 21 are connected, and the track | line 9 which is one linear form is comprised.

In the present embodiment, the first substrate unit 10 and the second substrate unit 20 are provided side by side on the same surface (5-1a), and are configured from a common dielectric substrate 5. The dielectric substrate 5 is made of a dielectric containing glass epoxy resin, fluorine resin, or the like.
In the present embodiment, the dielectric layer 13 is provided on the other surface 10 b of the first substrate unit 10, and the first line 11 is provided inside the dielectric substrate 5. In the present embodiment, the thickness of the dielectric substrate 5 is the same on one side (left side in FIG. 2) and the other side (right side in FIG. 2).
Although not shown, one side (left side in FIG. 2) of the dielectric substrate 5 is configured to be thinner than the other side (right side in FIG. 2), and the thin plate portion is the first substrate portion 10 and the thick portion is It may be the second substrate unit 20. That is, the dielectric layer 13 may be omitted.

As described above, the circuit board 1 is provided with the microstrip line 2 provided on one side (left side in FIG. 2) of the dielectric substrate 5 and the strip line 3 provided on the other side (right side in FIG. 2).
The dielectric substrate 5 is configured by laminating a first layer portion 5-1 and a second layer portion 5-2, and on one surface 5-1a of the first layer portion 5-1, A first ground 12 included in the microstrip line 2 and a second ground 22 included in the strip line 3 are formed of conductive foil.
Moreover, the 1st track | line 11 which the microstrip line 2 has, and the 2nd track | line 21 which the strip line 3 has on the other side surface 5-1b of the 1st layer part 5-1 are formed with linear conductor foil. Has been.
Then, as shown in FIG. 4, the one-side surface 5-2a of the second layer portion 5-2 and the other-side surface 5-1b of the first layer portion 5-1 are combined with each other. 1 and the second layer portion 5-2. A third ground 23 included in the strip line 3 is formed of a conductive foil on the other surface 5-2b of the second layer portion 5-2.

  FIG. 5 is a rear view of the circuit board 1 shown in FIG. The first ground 12 of the microstrip line 2 and the second ground 22 of the strip line 3 are formed of a conductive foil provided on one surface (5-1a) of the dielectric substrate 5, and these The grounds 12 and 22 are continuous with each other. That is, a part of one ground is for the microstrip line 2 and the other part is for the strip line 3.

  Thus, the circuit board 1 has three layers of conductive foil, the first ground 12 and the second ground 22 are provided as the first layer, and the first line 11 as the second layer (intermediate layer). The second line 21 is provided, and the third ground 23 is provided as the third layer. The 1st track | line 11 and the 2nd track | line 21 exist in the same layer (2nd layer). Each of the conductor foils is a metal foil, and in this embodiment is a copper foil.

  As shown in FIGS. 1, 2, and 4, a cutout portion 27 is provided in the third ground 23 included in the strip line 3. As shown in FIGS. 2 and 6, the notch 27 is provided in a part K of the portion of the third ground 23 that overlaps the second line 21, and the boundary E with the microstrip line 2. It has a shape that opens at A boundary E between the microstrip line 2 and the strip line 3 is indicated by a two-dot chain line in each drawing.

  The notch 27 shown in FIG. 6 has a V shape, and as a whole, the interval becomes wider toward the opening side (boundary E: input side). In this embodiment, the width dimension W of the line 9 (the first line 11 and the second line 21) is 0.2 mm, and the opening angle of the notch 27 is θ. The opening angle θ is an inclination angle with respect to a straight line in the longitudinal direction of the line 9. In FIG. 6, the depth of the notch 27 (the distance in the longitudinal direction of the line 9) is h.

  FIG. 7 shows simulation results for the reflection amount and the transmission amount in the circuit board 1 having the above-described configuration. In FIG. 7, the depth h of the notch 27 is 2 mm, and the opening angle θ of the notch 27 is changed from 4 ° to 24 °. Further, when the notch 27 is not provided, the reflection amount is -10.93 dB, the transmission amount is -2.04 dB, the reflection amount (-10.93 dB) is shown by a one-dot chain line in FIG. (−2.04 dB) is indicated by a two-dot chain line.

  As shown in FIG. 7, according to the circuit board 1 having the notch 27, both the reflection characteristic and the transmission characteristic are improved (compared to the case where the notch 27 is not present). Further, both the reflection amount and the transmission amount change depending on the value of the opening angle θ of the notch 27.

  FIG. 8 is a simulation result of the transmission amount in the circuit board 1 having the above-described configuration, and is a result when the depth h of the notch 27 is 2 mm, 3 mm, and 4 mm. FIG. 9 is a simulation result of the amount of reflection on the circuit board 1 having the above-described configuration, and is a result when the depth h of the notch 27 is 2 mm, 3 mm, and 4 mm. 8 and 9, the width dimension W of the line 9 is 0.2 mm, and the opening angle θ of the notch 27 is changed.

According to FIGS. 8 and 9, if the depth h of the notch 27 is increased (4 mm), the amount of transmission increases and the amount of reflection decreases when the opening angle θ of the notch 27 is small. .
Moreover, it is preferable that the width dimension B (see FIG. 6) at the opening end of the notch 27 is a predetermined ratio with respect to the width dimension W of the line 9. Specifically, the width dimension B of the notch 27 is preferably not less than twice and not more than four times the width dimension W of the line 9 (2 × W ≦ B ≦ 4 × W). Further, the opening angle θ of the notch 27 is preferably 3 ° or more and 10 ° or less. When the width dimension B of the notch 27 is too small or too large, it is estimated that the effect is reduced by approximating a form in which the notch 27 is not provided. The width dimension B at the open end of the notch 27 is the maximum value of the interval (notch width) of the notch 27.

  As described above, according to the circuit board 1 having the above-described configuration, a configuration in which the change between the microstrip line 2 and the strip line 3 is gradually performed by the notch 27 is obtained. Impedance mismatch at the changing point of the line 9 with the strip line 3 can be alleviated, the occurrence of reflection can be suppressed, and the reflection characteristics of the circuit board 1 can be improved. As a result, loss is reduced and transmission efficiency can be improved.

FIG. 10 shows a simulation result of the amount of transmission through the circuit board 1. The depth h of the notch 27 (see FIG. 6) is set to 2 mm, and the width dimension W of the line 9 is set to 0.2 mm. The result is 3 mm and 0.4 mm.
According to FIG. 10, the transmission amount increases as the width dimension W of the line 9 is reduced. In particular, if the width dimension W of the line 9 is reduced, the transmission amount when the opening angle θ of the notch 27 is small. Becomes larger.

  FIG. 11 is an explanatory diagram for explaining a modification of the notch 27. The cutout portion 27 shown in FIG. 11 has a shape that opens at a boundary E with the microstrip line 2 in a part K of the portion that overlaps the second line 21, as in the embodiment shown in FIG. 6. As a whole, the interval (notch width) becomes wider toward the opening side (boundary E). And the notch part 27 shown in FIG. 11 has the rounded part 27a as a part where a space | interval becomes still wider on the opening side. According to this configuration, impedance mismatch at the changing point of the line 9 can be relaxed, and reflection characteristics can be improved.

  FIG. 12 is an explanatory diagram for explaining still another modified example of the notch 27. The cutout portion 27 shown in FIG. 12 has a shape that opens at a boundary E with the microstrip line 2 in a part K of the portion overlapping the second line 21, similarly to the form shown in FIG. 6. As a whole, the interval becomes wider toward the opening side (boundary E). And the notch 27 shown in FIG. 12 has U shape instead of V shape.

Note that the cutout portion 27 may have other shapes, and as illustrated in FIGS. 6, 11, and 12, the cutout portion 27 is continuously spaced (notch width) toward the opening side (boundary E). ) May be other than a wide shape, for example, although not shown, the notch 27 has a staircase shape, and the gap may gradually increase toward the opening side (boundary E). Good.
In addition, the notch 27 is partially parallel to the line 9 and has a constant interval (notch width), except that the interval increases as it goes toward the opening side (boundary E) as a whole. The other portion may have a shape in which the interval becomes wider toward the opening side (boundary E).
As described above, the cutout portion 27 only needs to have a portion whose interval becomes wider toward the opening side. According to the cutout portion 27, the cutout portion 27 is caused by impedance mismatch at the change point of the line 9. Reflection can be suppressed more effectively.

  As mentioned above, according to the circuit board 1 of each said form, the microstrip line 2 and the strip line 3 are connected, the discontinuity of an impedance characteristic is relieve | moderated and it becomes possible to improve a reflective characteristic. That is, it can be said that the circuit board 1 includes a conversion unit that improves the transmission efficiency between the microstrip line 2 and the strip line 3.

  The circuit board 1 of the present invention is not limited to the form shown in the drawings, and may be in other forms within the scope of the present invention. For example, the circuit board 1 has been described as being usable in the millimeter wave band (60 GHz), but the radio wave band (frequency band) may be other than millimeter waves.

1: Circuit board 2: Microstrip line 3: Strip line 9: Line 10: First board part 10a: One side 10b: The other side 11: First line 12: First ground 20: Second board part 20a: Surface on one side 20b: Surface on the other side 21: Second line 22: Second ground 23: Third ground 27: Notch

Claims (2)

The first substrate portion, the first ground made of a conductor foil provided on one surface of the first substrate portion, and the linear conductor foil provided on the other side of the first substrate portion A microstrip line having a first line;
A second substrate part provided side by side with the first substrate part, a second ground made of a conductive foil provided on one side of the second substrate part, which is the same side as the first ground, A strip having a third ground made of a conductive foil provided on the other surface of the second substrate portion and a second line made of a linear conductive foil provided inside the second substrate portion. Line,
A circuit board in which the first line and the second line are connected to form one line,
Of the third ground that the stripline has, a portion that overlaps the second line is provided with a notch that opens on the boundary side with the microstrip line ,
The circuit board according to claim 1, wherein the notch has a U shape in which a depth side of the notch is arcuate .   The circuit board according to claim 1, wherein the notch has a portion whose interval becomes wider toward the opening side.

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