JP2016025476A - Converter for coaxial cable and microstrip line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter for a coaxial cable and a microstrip line, capable of improving a conversion characteristic in millimeter wave power conversion.SOLUTION: The converter includes: an earth plate 12 which is formed on a second surface of a dielectric substrate 10, to which an outer conductor 23 is connected, and which has an opening 12a disposed to face an inner conductor 21 and an insulator 22; a power supply electrode 13 which is formed on a first surface of the dielectric substrate 10 so as to face the inner conductor 21 and to which a MSL 3 is connected; a power supply through hole 17 which penetrates through the dielectric substrate 10 in the opening 12a, to make the inner conductor 21 conductive with the power supply electrode 13; an extraneous emission suppression electrode 14 which is formed on the first surface of the dielectric substrate 10, covers the opening 12a and includes a notch 14a for disposing the power supply electrode 13; and a grounding through hole 16 which penetrates through the dielectric substrate 10 and makes the earth plate 12 conductive with the extraneous emission suppression electrode 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coaxial cable / microstrip line converter, and more particularly to a coaxial cable / microstrip line converter for millimeter waves.

  A coaxial cable / MSL (microstrip line) converter is a power conversion circuit that performs power conversion between a coaxial cable and a microstrip line formed on a dielectric substrate. A coaxial cable is a transmission line including an inner conductor, an insulator that surrounds the inner conductor, and an outer conductor that surrounds the insulator. The microstrip line is a transmission line including a dielectric substrate, a microstrip conductor extending along the surface of the dielectric substrate, and a ground plate that covers the back surface of the dielectric substrate.

  A conventional coaxial cable / MSL converter has a through-hole penetrating the dielectric substrate, an annular land formed on the surface of the dielectric substrate adjacent to the through-hole, and connected to the microstrip line, It is comprised by the opening part of the ground plate formed in the position facing a land (for example, patent document 1). The end of the coaxial cable is accommodated in the opening, the outer conductor of the coaxial cable is connected to the ground plate, and the inner conductor protruding from the end face of the coaxial cable is accommodated in the through hole of the dielectric substrate. . The tip of the inner conductor protrudes from the surface of the dielectric substrate and is fixed to the land using solder.

JP 2000-232304 A

  The conventional coaxial cable / MSL converter as described above has a problem that the conversion characteristic in the power conversion of millimeter wave is not good. For example, when power is supplied from a coaxial cable to a microstrip line, there is a problem that unnecessary radiation is generated from the land portion. There is also a problem that the amount of reflection by the land portion is large and the insertion loss of power is large.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a coaxial cable / microstrip line converter capable of improving conversion characteristics in millimeter wave power conversion. In particular, an object of the present invention is to provide a coaxial cable / microstrip line converter capable of suppressing generation of unnecessary radiation from a converter even when converting high-frequency power in a frequency band exceeding 40 GHz. . Another object of the present invention is to provide a coaxial cable / microstrip line converter capable of suppressing the amount of reflection by the converter and reducing the insertion loss of power.

  In the coaxial cable / microstrip line converter according to the first aspect of the present invention, a microstrip line is formed on a first surface of a dielectric substrate, and an internal conductor is connected to the second surface of the dielectric substrate via an insulator. A coaxial cable / microstrip line converter that performs power conversion between the microstrip line and the coaxial cable with the end surfaces of the coaxial cable surrounded by an outer conductor facing each other, and is formed on the second surface of the dielectric substrate. A ground plate having an opening facing the inner conductor and the insulator, connected to the outer conductor, and formed on the first surface of the dielectric substrate, facing the inner conductor, and the microstrip. A power supply electrode to which a line is connected, and a power supply thread that penetrates the dielectric substrate in the opening and electrically connects the internal conductor to the power supply electrode. A hole, an unnecessary radiation suppression electrode formed on the first surface of the dielectric substrate, covering the opening, and having a notch for disposing the feeding electrode, and penetrating the dielectric substrate, A grounding plate and a grounding through hole for conducting the unnecessary radiation suppressing electrode are provided.

  In this coaxial cable / microstrip line converter, an unnecessary radiation suppressing electrode which is electrically connected to the ground plate and covers the opening of the ground plate facing the inner conductor and the insulator of the coaxial cable is formed on the first surface of the dielectric substrate. A power supply electrode is arranged in the notch of the unnecessary radiation suppressing electrode. For this reason, when power is supplied from the coaxial cable to the microstrip line, it is possible to suppress leakage of electromagnetic waves around the power supply electrode. Therefore, even when high-frequency power in a frequency band exceeding 40 GHz is converted, generation of unnecessary radiation from the converter can be suppressed. Moreover, since unnecessary radiation from the converter is suppressed, it is possible to reduce power insertion loss.

  A coaxial cable / microstrip line converter according to a second aspect of the present invention is the coaxial cable / microstrip line converter according to the present invention, wherein the power feeding electrode extends substantially in the line length direction of the microstrip line, and one end of the power feeding electrode is the microstrip line. And the other end is configured to have a curved shape whose width decreases as the distance from the center of the power supply through hole increases.

  According to such a configuration, compared to the case where the power feeding electrode has a shape having an apex angle, leakage of electromagnetic waves from the power feeding electrode to the surroundings can be suppressed, and power insertion loss can be reduced. it can. Moreover, since the change in impedance is suppressed from one end to the other end of the power supply electrode, the amount of reflection by the converter can be suppressed, and the insertion loss of power can be reduced.

  A coaxial cable / microstrip line converter according to a third aspect of the present invention is configured so that, in addition to the above configuration, the microstrip line has a distance in the line length direction from the center of the feed through hole that is approximately ¼ times the guide wavelength. The position is configured to have a step in the line width direction.

  In this coaxial cable / microstrip line converter, the traveling wave reflected at the center of the feedthrough hole interferes with the traveling wave reflected at the step on the microstrip line and propagated to the center of the feedthrough hole. Cancel each other out. For this reason, even when converting high-frequency power in a frequency band exceeding 40 GHz, the amount of reflection by the converter can be suppressed, and the insertion loss of power can be reduced.

  A coaxial cable / microstrip line converter according to a fourth aspect of the present invention includes, in addition to the above configuration, the unnecessary radiation suppression electrode via two or more grounding through holes arranged along the periphery of the opening. It is configured to be in conduction with the ground plate. According to such a configuration, leakage of electromagnetic waves to the periphery of the power feeding electrode can be blocked by the plurality of grounding through holes.

  A coaxial cable / microstrip line converter according to a fifth aspect of the present invention is configured such that, in addition to the above configuration, the grounding through-holes are arranged with an interval of about 1/4 times or less of the guide wavelength. The According to such a configuration, the electromagnetic wave leaking out around the power feeding electrode can be canceled by interference.

  ADVANTAGE OF THE INVENTION According to this invention, the coaxial cable microstrip line converter which improved the conversion characteristic in the power conversion of millimeter wave can be provided. In particular, even when high-frequency power in a frequency band exceeding 40 GHz is converted, it is possible to provide a coaxial cable / microstrip line converter that can suppress generation of unnecessary radiation from the converter. Further, it is possible to provide a coaxial cable / microstrip line converter capable of suppressing the amount of reflection by the converter and reducing the insertion loss of power.

It is the perspective view which expanded and showed one structural example of the coaxial cable and the MSL converter 1 by embodiment of this invention. It is the figure which showed the structural example of the coaxial cable and MSL converter 1 of FIG. 1, and the upper surface of the coaxial cable and MSL converter 1 is shown. It is sectional drawing which showed the structural example of the coaxial cable and MSL converter 1 of FIG. 2, and the cut surface at the time of cut | disconnecting the coaxial cable and MSL converter 1 by the AA cut line is shown. It is sectional drawing which showed the structural example of the coaxial cable and MSL converter 1 of FIG. 2, and the cut surface at the time of cut | disconnecting the coaxial cable and MSL converter 1 by the BB cutting line is shown. It is the figure which showed an example of the operation characteristic of the coaxial cable and MSL converter 1 of FIG. 1, and the transmission characteristic and reflection characteristic at the time of changing a frequency are shown. It is the figure which showed an example of the operation characteristic of the coaxial cable and MSL converter 1 of FIG. 1, and the transmission characteristic and reflection characteristic at the time of changing the line | wire width Wm of MSL3 are shown. It is the figure which showed the other structural example of the coaxial cable and MSL converter 1, and the case where the electrode 13 for electric power feeding is extended in the line | wire length direction of MSL3 by substantially equal width is shown. It is the figure which showed the other structural example of the coaxial cable and the MSL converter 1, and the case where the level | step difference 11a of the line | wire width direction is provided in MSL3 is shown. It is the figure which showed an example of the operation characteristic of the coaxial cable and MSL converter 1 of FIG. 8, and the transmission characteristic and reflection characteristic at the time of changing the position of the level | step difference 11a are shown. FIG. 2 is a diagram illustrating an example of a manufacturing process of the coaxial cable / MSL converter 1 of FIG. 1, in which a process of forming a grounding through hole 16 and a power feeding through hole 17 is illustrated.

<Coaxial cable / MSL converter 1>
FIG. 1 is a perspective view showing a configuration example of a coaxial cable / MSL converter 1 according to an embodiment of the present invention developed in the vertical direction. In this figure, a coaxial cable / MSL conversion in which the coaxial cable 2 is attached to the ground plate 12 with the central axis of the coaxial cable 2 aligned with the vertical direction and the end face of the coaxial cable 2 facing the lower surface of the dielectric substrate 10. Container 1 is drawn.

  The coaxial cable / MSL converter 1 is a power conversion circuit for converting high frequency power in the millimeter wave band between the coaxial cable 2 and the MSL (microstrip line) 3, and includes a dielectric substrate 10, a microstrip conductor 11, The ground plate 12, the feeding electrode 13, the unnecessary radiation suppressing electrode 14, the inner conductor electrode 15, the grounding through hole 16 and the feeding through hole 17 are configured.

  For example, the coaxial cable / MSL converter 1 can be used for a transmission antenna or a reception antenna of a monitoring vehicle-mounted radar or a high-speed wireless communication device using a millimeter wave having a frequency of about 30 to 300 GHz. An unnecessary radiation suppression electrode 14 is provided in the coaxial cable / MSL converter 1, and the power supply electrode 13 is disposed in the notch 14 a and is electrically connected to the ground plate 12 through the ground through hole 16, thereby converting the power of millimeter waves. The conversion characteristics are improved.

  The coaxial cable 2 is a transmission line for transmitting electrical signals and high-frequency power, and includes an internal conductor 21, an insulator 22 that surrounds the internal conductor 21, and an external conductor 23 that surrounds the insulator 22. 21 and the outer conductor 23 are coaxially arranged. The coaxial cable 2 extends in the vertical direction, and the inner conductor 21, the insulator 22, and the outer conductor 23 are exposed at the upper end surface. When the coaxial cable 2 is cut along a horizontal plane, the cut surface is circular.

  The inner conductor 21 is also called a center conductor and has a circular cross-sectional shape. The insulator 22 is a member for insulating the inner conductor 21 and the outer conductor 23, and is made of a dielectric material such as polyethylene. The outer conductor 23 has an annular cross-sectional shape and surrounds the inner conductor 21 via an insulator 22. For example, the outer diameter of the outer conductor 23 is 1 mm to 2 mm. The thickness of the insulator layer and the dielectric constant of the insulator 22 are determined according to the frequency, bandwidth, etc. of the electromagnetic wave to be transmitted.

  The dielectric substrate 10 is a substrate made of a dielectric. For example, the dielectric substrate 10 is a resin substrate for an antenna made of an insulating resin such as a fluororesin. The dielectric substrate 10 has a rectangular shape. For example, the relative permittivity of the insulator 22 of the coaxial cable 2 is about 2.0, whereas the relative permittivity of the dielectric substrate 10 is 2.7.

  The MSL 3 is a transmission line through which traveling waves propagate, and is formed on the upper surface of the dielectric substrate 10. The MSL 3 is configured by a microstrip conductor 11 that extends substantially at the same width along the upper surface of the dielectric substrate 10 and a ground plate 12 formed on the lower surface of the dielectric substrate 10.

  The ground plate 12 is a conductor pattern that functions as a ground electrode with respect to the conductor pattern on the upper surface of the dielectric substrate 10, and substantially covers the entire lower surface of the dielectric substrate 10. The ground plate 12 is connected to the outer conductor 23 of the coaxial cable 2 and is provided with an opening 12 a facing the inner conductor 21 and the insulator 22. The opening 12a is a punching pattern having a circular peripheral edge.

  The power supply electrode 13 is a conductor pattern for supplying power to the MSL 3, is formed on the upper surface of the dielectric substrate 10, faces the internal conductor 21 of the coaxial cable 2, and is connected to the MSL 3. The power supply electrode 13 extends in a substantially equal width in the line length direction of the MSL 3, one end thereof reaches the MSL 3, and the other end is formed of a circular region.

  The inner conductor electrode 15 is a conductor pattern for contacting the inner conductor 21 of the coaxial cable 2, is formed on the lower surface of the dielectric substrate 10, and is disposed in the opening 12 a of the ground plate 12.

  The unnecessary radiation suppressing electrode 14 is a conductor pattern for suppressing the generation of unnecessary radiation from the converter, is formed on the upper surface of the dielectric substrate 10, covers the opening 12 a of the ground plate 12, and is a feeding electrode. 13 is provided with a notch 14a. The unnecessary radiation suppression electrode 14 has a rectangular shape whose length in the front-rear direction is shorter than that of the dielectric substrate 10.

  The notch 14 a is a punching pattern that opens at the front side of the unnecessary radiation suppressing electrode 14 and extends substantially at the same width toward the center of the unnecessary radiation suppressing electrode 14, and accommodates the circular region of the power supply electrode 13. The inner wall surface of the notch 14a faces the side end surfaces of the MSL 3 and the power feeding electrode 13.

  The grounding through-hole 16 is made of a conductive layer that penetrates the dielectric substrate 10 and makes the grounding plate 12 and the unnecessary radiation suppressing electrode 14 conductive. The dielectric substrate 10 is provided with two or more grounding through-holes 16, and the unnecessary radiation suppressing electrode 14 is connected to the grounding plate 12 through these grounding through-holes 16 arranged along the periphery of the opening 12 a. And continuity. The grounding through hole 16 is provided outside the opening 12 a of the grounding plate 12. With this configuration, leakage of electromagnetic waves around the power supply electrode 13 can be blocked by the plurality of grounding through holes 16.

  The power feed through hole 17 is made of a conductive layer that penetrates the dielectric substrate 10 in the opening 12 a of the ground plate 12 and makes the internal conductor 21 conductive to the power feed electrode 13. The power supply electrode 13 is electrically connected to the internal conductor electrode 15 through the power supply through hole 17.

  The grounding through hole 16 and the power feeding through hole 17 may be any one that electrically connects the conductor pattern on the upper surface side of the dielectric substrate 10 and the conductor pattern on the lower surface side of the dielectric substrate 10. The shape and manufacturing method of the grounding through hole 16 and the power feeding through hole 17 are not particularly limited. For example, the grounding through hole 16 and the power feeding through hole 17 are made of a metal layer covering the inner wall of the through hole penetrating the dielectric substrate 10, and the vicinity of the center of the through hole is hollow.

  The conductor pattern constituting the MSL 3, the ground plate 12, the power feeding electrode 13, the unnecessary radiation suppressing electrode 14 and the inner conductor electrode 15 is obtained by attaching a metal thin film, for example, copper foil on the dielectric substrate 10. This metal thin film is manufactured by patterning by etching or the like. The grounding through-hole 16 and the power-feeding through-hole 17 are formed, for example, by forming a through-hole by drilling in the dielectric substrate 10 to which a metal thin film is attached, and then forming a plating layer made of a metal such as copper as a dielectric. It is manufactured by forming on the substrate 10.

  The line width of the MSL 3 is determined according to the frequency of the electromagnetic wave to be transmitted, the bandwidth, the thickness of the dielectric substrate 10, the dielectric constant of the dielectric substrate 10, and the like. The line width of MSL3 is narrower than the in-tube wavelength λg of electromagnetic waves. The guide wavelength λg is the wavelength of the electromagnetic wave propagating through the MSL 3 formed on the dielectric substrate 10.

  FIG. 2 is a diagram illustrating a configuration example of the coaxial cable / MSL converter 1 of FIG. 1, and illustrates an upper surface of the coaxial cable / MSL converter 1. In this figure, the coaxial cable / MSL converter 1 is drawn so that the longitudinal direction of the MSL 3 extending in the front-rear direction coincides with the vertical direction of the figure, and the direction perpendicular to the paper surface coincides with the central axis of the coaxial cable 2.

  The unnecessary radiation suppressing electrode 14 is formed of a rectangular thin flat plate, and of the long sides extending in the left-right direction, the rear long side is made coincident with the long side of the dielectric substrate 10 and the short side extending in the front-rear direction is a dielectric. It is arranged on the dielectric substrate 10 so as to coincide with the short side of the substrate 10.

  The microstrip conductor 11 of the MSL 3 has a shape in which the line width Wm is constant and extends in the front-rear direction, and its front end reaches the front end of the dielectric substrate 10 and is exposed from the front end surface of the dielectric substrate 10. The line width Wm is the length in the left-right direction. The MSL 3 is arranged on a straight line connecting the midpoints of the long sides of the dielectric substrate 10.

  The power feeding electrode 13 has a circular area facing the inner conductor electrode 15, and the circular area is connected to the rear end of the MSL 3. The circular region of the power supply electrode 13 is a curved region whose width decreases as the distance from the center of the power supply through hole increases. The horizontal length L1, that is, the maximum value of the width is wider than the line width Wm. . The circular region of the power supply electrode 13 is symmetrical with respect to a straight line in the front-rear direction passing through the center of the power supply through hole 17. By making the shape of the power supply electrode 13 line-symmetric, impedance mismatching can be made difficult to occur.

  The notch 14 a of the unnecessary radiation suppressing electrode 14 is formed along the contours of the microstrip conductor 11 and the power feeding electrode 13, and the inner wall faces the side end surfaces of the microstrip conductor 11 and the power feeding electrode 13. The unnecessary radiation suppression electrode 14 projects to the front side of the opening 12a of the ground plate 12, and the notch 14a extends in the front-rear direction across the periphery of the opening 12a. The distance between the inner wall surface of the notch 14a and the side end surfaces of the microstrip conductor 11 and the feeding electrode 13 is 0.1 mm or more.

  The circular region of the power supply electrode 13, the power supply through hole 17, and the opening 12 a of the ground plate 12 are arranged coaxially, and the center positions in a plane parallel to the dielectric substrate 10 coincide. Each grounding through hole 16 is arranged on a circle concentric with the circular region of the power supply electrode 13 and the power supply through hole 17, and the circumferential interval L <b> 2 is substantially constant. That is, the grounding through holes 16 are arranged with a distance L2. The interval L2 is a distance between the inner walls of the adjacent grounding through holes 16 and is preferably about 1/4 times or less of the guide wavelength λg. By setting the interval L2 to be approximately ¼ or less of the guide wavelength λg, the electromagnetic waves leaking around the power supply electrode 13 can be canceled by interference.

  In this example, nine grounding through holes 16 are arranged at approximately equal intervals so as to surround the opening 12a of the grounding plate 12. The grounding through holes 16 are symmetrically arranged with respect to a straight line in the front-rear direction passing through the center of the power feeding through hole 17.

  3 and 4 are cross-sectional views showing a configuration example of the coaxial cable / MSL converter 1 of FIG. FIG. 3 shows a cut surface when the coaxial cable / MSL converter 1 is cut along an AA cutting line. FIG. 4 shows a cut surface when the coaxial cable / MSL converter 1 is cut along a BB cutting line.

  The coaxial cable 2 is fixed to the ground plate 12 with the upper end surface 2a facing the opening 12a of the ground plate 12, the internal conductor 21 is in contact with the internal conductor electrode 15, and the external conductor 23 is connected to the ground plate 12. Touching. The peripheral edge of the opening 12 a coincides with the outer edge of the insulator 22. The inner conductor electrode 15 has an outer diameter larger than the diameter of the inner conductor 21, and projects outward from the inner edge of the insulator 22.

  The power feeding electrode 13 includes a circular region 13 a that faces the inner conductor electrode 15, and a connection region 13 b that connects the circular region 13 a and the microstrip conductor 11. The connection region 13b extends with a substantially equal width in the line length direction of the microstrip line 3, that is, in the front-rear direction. One end of the connection region 13b reaches the microstrip conductor 11, and the other end is connected to the circular region 13a.

  The circular region 13a has a curved shape in which the width in the left-right direction decreases as the distance from the center of the power supply through hole 17 increases. The diameter of the circular region 13a is determined by impedance matching with the coaxial cable 2 and the MSL3.

  A part of the microstrip conductor 11 and the feeding electrode 13 are arranged in the notch 14 a of the unnecessary radiation suppressing electrode 14. The inner wall surface of the notch 14 a protrudes inward from the outer edge of the insulator 22.

  In this example, the microstrip conductor 11, the ground plate 12, the power feeding electrode 13, the unnecessary radiation suppressing electrode 14 and the inner conductor electrode 15 are constituted by copper foil layers 31 and 33 and a plating layer 32. The copper foil layers 31 and 33 are conductive layers formed by attaching copper foils to the lower surface and the upper surface of the dielectric substrate 10, respectively.

  The plating layer 32 is a conductive layer formed after forming a through hole in the dielectric substrate 10 to which the copper foil is attached, and is formed on the inner wall surface of the through hole and on the copper foil layers 31 and 33. Yes. The grounding through hole 16 and the power feeding through hole 17 are constituted by such a plating layer 32. The plating layer 32 is preferably made of the same material as the metal layer formed on the front and back surfaces of the dielectric substrate 10. For this reason, in this Embodiment, the plating layer 32 is formed by copper plating corresponding to the copper foil layers 31 and 33.

  The opening 12 a of the ground plate 12 and the notch 14 a of the unnecessary radiation suppressing electrode 14 are formed by patterning the copper foil layers 31 and 33 and the plating layer 32 after forming the plating layer 32.

  FIG. 5 is a diagram showing an example of operating characteristics of the coaxial cable / MSL converter 1 of FIG. 1, and shows transmission characteristics and reflection characteristics when the frequency is changed. This figure shows a case where the diameter of the circular region 13a of the power supply electrode 13 is 0.4 mm, and the line width Wm of the MSL 3 is matched with the diameter of the circular region 13a.

  (A) in the figure shows the transmission characteristics. In this figure, a characteristic curve showing the transmission characteristics is drawn with the vertical axis as the transmission amount and the horizontal axis as the frequency of electromagnetic waves. This characteristic curve monotonously decreases as the frequency increases within a frequency range of 40 GHz to 80 GHz. Specifically, within the range from 40 GHz to 60 GHz, the transmission amount is substantially constant within a range of −0.15 dB or less and −0.2 dB or more. Further, within the range from 60 GHz to 75 GHz, the transmission amount decreases from −0.2 dB to −0.4 dB, and when the frequency exceeds 75 GHz, the reduction rate of the transmission amount is further increased, and the transmission amount is 80 GHz. It has reached -0.58 dB.

  According to this experimental result, the coaxial cable / MSL converter 1 is a case where the transmission amount is −0.4 dB or more within a range of 40 GHz or more and 75 GHz or less, and high frequency power in a frequency band exceeding 40 GHz is converted. However, it can be seen that the power insertion loss is extremely small.

  (B) in the figure shows the reflection characteristics. In this figure, a characteristic curve showing the reflection characteristic is drawn with the vertical axis as the reflection amount and the horizontal axis as the frequency of the electromagnetic wave. This characteristic curve monotonously increases as the frequency increases within a frequency range of 40 GHz to 80 GHz. Specifically, the reflection amount increases from −46 dB to −30 dB within the range from 40 GHz to 50 GHz, and the reflection amount increases from −30 dB to −20 dB within the range from 50 GHz to 63 GHz. . If the frequency exceeds 63 GHz, the rate of increase in the amount of reflection is substantially constant, and the amount of reflection reaches −12 dB at 80 GHz.

  According to this experimental result, the coaxial cable / MSL converter 1 has a reflection amount of −12 dB or less within a range of 40 GHz to 80 GHz, and converts high frequency power in a frequency band exceeding 40 GHz. It can be seen that the amount of reflection is extremely small.

  FIG. 6 is a diagram showing an example of the operating characteristics of the coaxial cable / MSL converter 1 of FIG. 1, showing the transmission characteristics and reflection characteristics when the line width Wm of the MSL 3 is changed. This figure shows a case where the diameter of the circular region 13a of the power supply electrode 13 is 0.4 mm and the frequency of the electromagnetic wave is 61 GHz. In the figure, the left vertical axis is the transmission amount, the horizontal axis is the transmission line width Wm, and the broken line shows the transmission characteristics, and the right vertical axis is the reflection amount, and the horizontal axis is the line width Wm, the reflection line shows the reflection characteristics. Is drawn.

  The transmission characteristics monotonously increase as the line width Wm increases within the range where the line width Wm is 0.1 mm or more and 0.4 mm or less. Specifically, the transmission amount is −0.75 dB at 0.1 mm, the transmission amount is −0.42 dB at 0.2 mm, the transmission amount is −0.26 dB at 0.3 mm, and 0.4 mm. The transmission amount is −0.20 dB at 0.5 mm, and the transmission amount is −0.30 dB at 0.5 mm.

  On the other hand, the reflection characteristic monotonously decreases as the line width Wm increases within the range where the line width Wm is 0.1 mm or more and 0.4 mm or less. Specifically, the reflection amount is -8.9 dB at 0.1 mm, the reflection amount is -12.2 dB at 0.2 mm, the reflection amount is -16.1 dB at 0.3 mm, and 0.4 mm. The reflection amount is -21.3 dB at 0.5 mm, and the reflection amount is -20.0 dB at 0.5 mm.

  According to this experimental result, when the line width Wm is 0.4 mm, that is, when the line width Wm matches the diameter of the circular region 13a of the feeding electrode 13, the amount of transmission is maximum and the reflection is performed. It can be seen that the amount is minimal and the conversion characteristics of the coaxial cable / MSL converter 1 are optimized.

  In the coaxial cable / MSL converter 1 according to the present embodiment, an unnecessary radiation suppressing electrode that is electrically connected to the ground plate 12 and covers the opening 12 a of the ground plate 12 facing the inner conductor 21 and the insulator 22 of the coaxial cable 2. 14 is formed on the upper surface of the dielectric substrate 10, and the feeding electrode 13 is disposed in the notch 14 a of the unnecessary radiation suppressing electrode 14. For this reason, when power is supplied from the coaxial cable 2 to the MSL 3, leakage of electromagnetic waves around the power supply electrode 13 can be suppressed. Accordingly, even when high-frequency power in a frequency band exceeding 40 GHz is converted, generation of unnecessary radiation from the converter 1 can be suppressed. Moreover, since unnecessary radiation from the converter 1 is suppressed, it is possible to reduce power insertion loss.

  In FIG. 2, the coaxial cable / MSL converter 1 in which the diameter of the circular region 13a of the power supply electrode 13 is larger than the line width Wm of the MSL3 has been described, but the present invention is based on the configuration of the power supply electrode 13. It is not limited. For example, the conversion characteristics of the converter 1 may be optimized by matching the diameter of the circular region 13a with the line width Wm of the MSL3.

  FIG. 7 is a diagram showing another configuration example of the coaxial cable / MSL converter 1, and shows a case where the power supply electrode 13 extends with a substantially equal width in the line length direction of the MSL 3. In this coaxial cable / MSL converter 1, the feeding electrode 13 extends in a line length direction (front-rear direction) of the MSL 3 with a substantially equal width, one end thereof reaches the MSL 3, and the other end of the feeding through hole 17. It has a curved shape in which the width in the left-right direction narrows away from the center.

  Specifically, the power supply electrode 13 is formed in a semicircular region formed on the rear side of the center of the power supply through hole 17 and on the front side of the center of the power supply through hole 17. And a connection region for connecting the microstrip conductors 11. The semicircular region of the feeding electrode 13 has a length in the left-right direction that matches the line width Wm.

  By comprising in this way, compared with the case where the electrode 13 for electric power feeding becomes a shape which has an apex angle, it can suppress that electromagnetic waves leak to the circumference | surroundings from the electrode 13 for electric power feeding, and reduce the insertion loss of electric power. be able to. Moreover, since the change in impedance is suppressed from the front end to the rear end of the power feeding electrode 13, the amount of reflection by the converter 1 can be suppressed, and the insertion loss of power can be reduced.

  In the present embodiment, an example in which the unnecessary radiation suppression electrode 14 is provided, the power supply electrode 13 is disposed in the notch 14a, and the ground plate 12 is made conductive with the ground through hole 16 has been described. The invention does not limit the configuration of the coaxial cable / MSL converter 1 to that shown in FIG. 2 or FIG. For example, the MSL 3 may be configured to suppress the amount of reflection by the converter 1 by providing a step in the line width direction.

  FIG. 8 is a diagram showing another configuration example of the coaxial cable / MSL converter 1, and shows a case where a step 11a in the line width direction is provided in the MSL3. The step 11a is a step in the line width direction (left-right direction) formed by discontinuously changing the line width Wm, and is disposed at a position where the line length L3 is approximately 1/4 times the guide wavelength λg. ing.

  The power supply electrode 13 extends in a substantially equal width in the line length direction of the MSL 3, one end thereof reaches the MSL 3, and the other end has a curved shape in which the width in the left-right direction is narrowed away from the center of the power supply through hole 17. . The line length L3 is a distance in the line length direction (front-rear direction) from the center of the feed through hole 17 to the step 11a. That is, in MSL3, the line width Wm on the rear side of the step 11a is wider than the front side of the step.

  With this configuration, the traveling wave reflected at the center of the feed through hole 17 and the traveling wave reflected at the step 11a and propagated to the center of the feed through hole 17 cancel each other out due to interference. For this reason, even when converting high-frequency power in a frequency band exceeding 40 GHz, the amount of reflection by the converter 1 is suppressed without changing the line width on the circuit element side such as a radiating element or a distributor, and the power Insertion loss can be reduced.

  FIG. 9 is a diagram showing an example of the operating characteristics of the coaxial cable / MSL converter 1 of FIG. 8, showing the transmission characteristics and the reflection characteristics when the position of the step 11a is changed in the front-rear direction. This figure shows a case where the diameter of the semicircular region of the feeding electrode 13 is 0.4 mm and the line width Wm on the circuit element side of the MSL 3 is 0.35 mm. The frequency of the electromagnetic wave is 61 GHz. In the figure, the left vertical axis is the transmission amount, the horizontal axis is the line length L3 and the broken line showing the transmission characteristics, and the right vertical axis is the reflection amount and the horizontal axis is the line length L3 and the broken line showing the reflection characteristics. Is drawn.

  As for the transmission characteristics, the transmission amount monotonously increases as the line length L3 increases within the range of the line length L3 from 0.3 mm to 0.9 mm, and the transmission amount is maximum at the line length L3 = 0.9 mm. (Maximum value -0.17 dB), and the transmission amount monotonously decreases as the line length L3 increases within the range of 0.9 mm to 1.9 mm.

  On the other hand, the reflection characteristic is such that the reflection amount monotonously decreases as the line length L3 increases within the range where the line length L3 is 0.3 mm or more and 0.9 mm or less, and the reflection amount at the line length L3 = 0.9 mm. Becomes the minimum (minimum value −26.3 dB), and the reflection amount monotonously increases as the line length L3 increases within the range of 0.9 mm to 1.9 mm.

  According to this experimental result, when the line length L3 is 0.9 mm, that is, when the line length L3 is approximately ¼ times the guide wavelength λg, the transmission amount is the maximum and the reflection amount is It can be seen that the conversion characteristics of the coaxial cable / MSL converter 1 are optimized.

  FIG. 10 is a diagram showing an example of a manufacturing process of the coaxial cable / MSL converter 1 of FIG. 1 and shows a process of forming the grounding through hole 16 and the power feeding through hole 17. (A) in the figure shows a step of attaching copper foils 41 and 42 to the front and back surfaces of a dielectric substrate 40 made of a fluororesin. The metal layer made of the copper foil 41 constitutes the feeding electrode 13 or the unnecessary radiation suppressing electrode 14, and the metal layer made of the copper foil 42 constitutes the ground plate 12 or the inner conductor electrode 15.

  (B) in the drawing shows a drilling step for forming a through hole 43 in the dielectric substrate 40 to which the copper foils 41 and 42 are attached. (C) in the drawing shows a step of surface-treating the inner wall of the through hole 43. In this surface treatment, the plating layer is easily attached by the roughening treatment for roughening the surface of the dielectric layer exposed on the inner wall of the through hole 43.

  (D) in the drawing shows a step of forming a metal layer 44 on the dielectric substrate 40 after the surface treatment by electroless copper plating. In this step, the metal layer 44 is deposited on the object to be plated using the oxidation phenomenon of the reducing agent contained in the plating solution. (E) in the drawing shows a step of forming a metal layer 45 by electrolytic copper plating on the dielectric substrate 40 after the metal layer 44 is formed. In this step, the metal layer 45 is deposited on the object to be plated using the reducing action by the current. The metal layers 44 and 45 are formed on the inner wall surface of the through hole 43 and the surfaces of the metal layers 41 and 42. Through such a process, the grounding through hole 16 and the power feeding through hole 17 are formed.

  In the present embodiment, an example in which the rear side of the power supply electrode 13 from the center of the power supply through hole 17 is circular has been described. However, the present invention limits the shape of the power supply electrode 13 to this. Instead, any other shape may be used as long as it has a curved shape whose width narrows away from the center of the power feed through hole. For example, a configuration in which the rear side of the power supply through-hole 17 of the power supply electrode 13 is formed of an ellipse, a parabola, a hyperbola, or other curved shapes may be employed.

  Further, in the present embodiment, an example in which an inner conductor electrode 15 that makes contact with the inner conductor 21 of the coaxial cable 2 is provided and the inner conductor electrode 15 and the feeding electrode 13 are electrically connected by the feeding through hole 17 is described. As described above, the present invention does not limit the connection method of the internal conductor 21 and the power supply electrode 13 via the power supply through hole 17. For example, the internal conductor 21 is not provided, and the internal conductor 21 protruding from the end face of the coaxial cable 2 is inserted into the feed through hole 17 so that the internal conductor 21 and the feed through hole 17 are made conductive. It may be a simple configuration.

1 Coaxial Cable / MSL Converter 10 Dielectric Substrate 11 Microstrip Conductor 12 Ground Plate 12a Opening 13 Feeding Electrode 14 Unwanted Radiation Suppressing Electrode 14a Notch 15 Internal Conductor Electrode 16 Grounding Through Hole 17 Feeding Through Hole 2 Coaxial Cable 21 Inner conductor 22 Insulator 23 Outer conductor 3 MSL

Claims (5)

A microstrip line is formed on the first surface of the dielectric substrate, and the end surface of the coaxial cable in which the inner conductor is surrounded by the outer conductor via the insulator is opposed to the second surface of the dielectric substrate, In the coaxial cable / microstrip line converter that performs power conversion between the line and the coaxial cable,
A ground plate formed on the second surface of the dielectric substrate, to which the outer conductor is connected, and having an opening facing the inner conductor and the insulator;
A feeding electrode formed on the first surface of the dielectric substrate, facing the inner conductor and connected to the microstrip line;
A feedthrough through hole that penetrates the dielectric substrate in the opening and connects the inner conductor to the feed electrode;
An unnecessary radiation suppressing electrode formed on the first surface of the dielectric substrate, covering the opening, and having a notch for arranging the feeding electrode;
A coaxial cable / microstrip line converter comprising a grounding through-hole penetrating the dielectric substrate and electrically connecting the ground plate and the unnecessary radiation suppressing electrode.   The power supply electrode extends in a line length direction of the microstrip line with a substantially equal width, one end of the microstrip line reaches the microstrip line, and the other end is a curve whose width decreases as the distance from the center of the power supply through hole increases. The coaxial cable / microstrip line converter according to claim 1, wherein the converter is a shape.   The microstrip line has a step in the line width direction at a position where the distance in the line length direction from the center of the feed through hole is approximately 1/4 times the guide wavelength. Coaxial cable / microstrip line converter.   4. The unnecessary radiation suppressing electrode is electrically connected to the ground plate through two or more grounding through-holes arranged along the periphery of the opening. Coaxial cable / microstrip line converter described in 1.   5. The coaxial cable / microstrip line converter according to claim 4, wherein the grounding through holes are arranged with an interval of about 1/4 times or less of the guide wavelength.

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