JP4247999B2 - High frequency line-waveguide converter - Google Patents

Description

  The present invention converts a high-frequency line such as a coplanar line forming a high-frequency circuit or a coplanar line with a ground, which is used in a microwave or millimeter wave region, into a waveguide, and connects the high-frequency circuit and the antenna or the high-frequency circuit. The present invention relates to a high-frequency line-waveguide converter that can easily mount and evaluate a system by performing the above-described process using a waveguide.

  In recent years, high-frequency signals used for information transmission have been studied to utilize frequencies from the microwave region to the millimeter wave region. For example, an inter-vehicle radar has been proposed as an application system using millimeter-wave high-frequency signals. In such a high frequency system, a front end using a waveguide has been adopted for transmission between the high frequency circuit module and the antenna.

As such a high-frequency front end, it functions as a dielectric layer, a coplanar line composed of a line conductor formed on the surface of the dielectric layer, and a coplanar ground conductor layer disposed on both sides thereof, and an antenna formed at the tip of the coplanar line. And a waveguide connected to a position facing the slot on the back surface of the dielectric layer, and a shield conductor formed so as to connect the waveguide and the same grounded conductor layer inside the dielectric layer. A high-frequency line-waveguide converter has been proposed (see Patent Document 1 below). A ground conductor layer having an opening facing the slot is formed on the back surface of the dielectric layer.
Japanese Patent Laid-Open No. 2004-32321

  However, in the conventional high-frequency line-waveguide converter, since the shield conductor is provided outside the opening of the dielectric layer in order to improve the shielding performance, the characteristic impedance changes abruptly and the ground conductor Impedance mismatch tends to occur between the layer opening and the shield conductor, resulting in increased reflection loss in the high-frequency line-waveguide converter, and conversion of transmission between the high-frequency line and the waveguide. There was a problem of low efficiency.

  The present invention has been devised in view of the above problems, and an object thereof is to provide a high-frequency line-waveguide converter having high transmission conversion efficiency between a high-frequency line and a waveguide.

  The high-frequency line-waveguide converter of the present invention is formed on a dielectric layer having first and second surfaces, and the first surface of the dielectric layer, and a line conductor and the line conductor A high-frequency line composed of a first ground conductor layer surrounding the end, and a slot formed on the first surface of the dielectric layer so as to intersect the line conductor and electromagnetically coupled to the line conductor A second grounding conductor layer formed in an inner layer of the dielectric layer or the second surface, having an opening facing the slot, and formed in the dielectric layer, 1 ground conductor layer and a shield conductor that electrically connects the second ground conductor layer, and a connection region of the shield conductor in the second ground conductor layer is the second ground conductor layer. It protrudes into the opening.

  In the high-frequency line-waveguide converter of the present invention, a plurality of the shield conductors are formed, and the shield conductors in the second ground conductor layer projecting into the opening of the second ground conductor layer. A plurality of connection regions are provided corresponding to the plurality of shield conductors.

  The high-frequency line-waveguide converter according to the present invention reduces the impedance discontinuity due to the connection area of the shield conductor in the second ground conductor layer protruding into the opening of the second ground conductor layer. It becomes possible. Therefore, the reflection loss in the high-frequency line-waveguide converter can be reduced, the transmission characteristics between the high-frequency line and the waveguide can be improved, and the usable band can be widened. The conversion efficiency of transmission to and from the wave tube can be increased.

  In the high-frequency line-waveguide converter of the present invention, a connection region of the shield conductor in the second ground conductor layer protruding from the opening of the second ground conductor layer is formed on the plurality of shield conductors. Correspondingly, the discontinuity of impedance can be further reduced by providing a plurality.

  The high-frequency line-waveguide converter of the present invention will be described in detail with reference to the accompanying materials. FIG. 1A is a plan view showing an example of an embodiment of a high-frequency line-waveguide converter of the present invention, and FIG. 1B is a high-frequency line-waveguide converter of FIG. FIG. 1C is a plan view of the ground conductor layer 8 of the high-frequency line-waveguide converter of FIG. 1A.

  The high-frequency line-waveguide converter of the present invention includes a dielectric layer 2, a high-frequency line 1 formed in the dielectric layer 2, a slot 5, and a second ground conductor having an opening 11 facing the slot 5. A layer 8 and a shield conductor 7 are provided.

  The high-frequency line 1 includes a line conductor 3 formed on the first surface (upper surface) 2 a of the dielectric layer 2 and a first ground conductor layer (coplanar ground conductor layer) formed so as to surround the line conductor 3. 4 to form a coplanar line shape. Further, a slot 5 is provided in the same-surface ground conductor layer 4 on the upper surface 2 a of the dielectric layer 2, and is electromagnetically coupled to one end of the line conductor 3. Thereby, the high frequency signal transmitted to the high frequency line 1 is radiated from the slot 5 as an electromagnetic wave into the waveguide 6 arranged to extend downward.

  In this Embodiment, the front-end | tip of the line conductor 3 is a short circuit end short-circuited with the same surface grounding conductor layer 4, as shown in FIG. As another example, there is one in which the end of the line conductor 3 is an open end without being short-circuited.

  The dielectric layer 2 is shielded by a shield conductor 7 formed of a side conductor formed on its side surface or a through conductor disposed inside the dielectric layer 2 as shown in FIG. The electromagnetic wave radiated into the layer 2 is prevented from leaking and the conversion efficiency is prevented from being lowered. The shield conductor 7 is formed with a predetermined interval (not more than 1/4 times the wavelength of the signal transmitted through the high-frequency line 1) so as to surround the slot 5 when seen in a plan view.

  Further, a frame-like ground conductor layer 8 formed so as to surround the slot 5 in a plan view is disposed on the inner layer and the second surface (lower surface) 2b of the dielectric layer 2, and the same-surface ground conductor layer 4 is disposed. And the ground conductor layer 8 are connected via a shield conductor 7. The ground conductor layer 8 may be formed in a plurality of layers.

  The high-frequency line-waveguide converter according to the present invention forms a protruding opening 11 in the ground conductor layer 8 in which the opening 11 is formed so as to surround the slot 5 as seen in a plan view as shown in FIG. ing. As a result, the shield conductor 7 and the projecting opening 11 are prevented from being grounded due to misalignment and stable grounding is possible. Therefore, it is possible to reduce reflection loss in the high-frequency line-waveguide converter, improve the transmission between the high-frequency line 1 and the waveguide 6, and widen the usable band. The conversion efficiency of transmission between 1 and the waveguide 6 can be increased.

  Examples of the dielectric material for forming the dielectric layer 2 include ceramic materials mainly composed of aluminum oxide, aluminum nitride, silicon nitride, mullite, and the like, and glass ceramic formed by firing a mixture of glass and glass and ceramic filler. Materials, organic resin materials such as epoxy resins, polyimide resins, fluororesins such as tetrafluoroethylene resin, and organic resin-ceramic (including glass) composite materials are used.

  The conductor material for forming the line conductor 3, the ground conductor layer 4 on the same plane, the shield conductor 7 such as the through conductor, and the ground conductor layer 8 is metallized mainly composed of tungsten, molybdenum, gold, silver, copper, or gold. Metal foils mainly composed of silver, copper, aluminum or the like are used.

  In particular, when the high-frequency line-waveguide converter is built in a wiring board on which high-frequency components are mounted, the dielectric material for forming the dielectric layer 2 has a small dielectric loss tangent and can be hermetically sealed. It is desirable. Examples of such a dielectric material include ceramics and glass ceramic materials such as an aluminum oxide sintered body and an aluminum nitride sintered body. Such a hard material is preferable in terms of improving the reliability of the mounted high-frequency component because the dielectric loss tangent is small and the mounted high-frequency component can be hermetically sealed. In this case, it is desirable to use a metallized conductor capable of co-firing with a dielectric material as the conductor material in order to improve hermetic sealing and productivity.

  The high-frequency line-waveguide converter of the present invention is manufactured as follows. For example, when an aluminum oxide sintered body is used as a dielectric material, first, an appropriate organic solvent or solvent is added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to form a slurry. This is formed into a sheet shape by a known doctor blade method or calendar roll method to produce a ceramic green sheet. Further, a metallized paste is prepared by adding and mixing an appropriate solvent and solvent to a raw material powder such as refractory metal such as tungsten or molybdenum, aluminum oxide, silicon oxide, magnesium oxide, calcium oxide or the like.

  Next, a through hole for forming a shield conductor 7 as a through conductor is formed in the ceramic green sheet to be the dielectric layer 2 by, for example, a punching method, and a metallized paste is embedded in the through hole by, for example, a printing method. The metallized paste is printed in the shape of the line conductor 3, the same-surface ground conductor layer 4, the ground conductor layer 8, and the upper conductor layer 9. Further, when the dielectric layer 2 has a laminated structure of a plurality of dielectric layers, a ceramic green sheet printed with a metallized paste or embedded in a through-hole may be similarly laminated and pressed and pressed. Good.

  The ceramic green sheets to be the dielectric layers 2 are fired at a high temperature (about 1600 ° C.). Furthermore, for example, nickel plating and gold plating are applied to the surfaces of conductors exposed on the upper and lower surfaces, such as the line conductor 3, the same-surface ground conductor layer 4, and the ground conductor layer 8 as necessary.

  The shield conductor 7 of the present invention is disposed on the side surface or inside of the dielectric layer 2 so as to surround the slot 5 and electrically connects the same-surface ground conductor layer 4 and the ground conductor layer 8.

  The shield conductor 7 only needs to be able to electrically connect the same-surface ground conductor layer 4 and the ground conductor layer 8, and various means such as a side conductor and a through conductor are used. For example, a conductor deposited on the side surface of the dielectric layer 2, a so-called castellation conductor in which a conductor layer is deposited on the inner wall of the notch on the side surface of the dielectric layer 2, or a conductor layer is coated on the inner wall of the through hole. Examples include so-called through-hole conductors that are attached, and so-called via conductors in which the insides of the through-holes are filled with a conductor.

  The shape of the waveguide 6 is not particularly limited. For example, when a WR series standardized as a rectangular waveguide is used, a variety of measurement calibration kits are available, so that various characteristics can be easily evaluated. In order to reduce the size and weight of the system in accordance with the frequency of the high-frequency signal, a rectangular waveguide that is miniaturized within a range in which the waveguide is not cut off may be used. A circular waveguide may be used.

  The waveguide 6 can be composed of a metal or a dielectric having a metal layer formed on the inner surface. For example, the waveguide 6 can be formed into a tubular shape or a dielectric such as ceramics or resin is required. In this case, the inner surface is coated with a metal after being molded. The inner surface of the waveguide 6 may be covered with a noble metal such as gold or silver in order to reduce conductor loss due to current or prevent corrosion. The waveguide 6 is attached to the ground conductor layer 8 by joining with a brazing material, tightening with a screw, or the like, and the waveguide 6 and the ground conductor layer 8 are electrically connected.

  In order to attach the waveguide 6 to the ground conductor layer 8 by the brazing material, the connecting conductor layer 8 electrically connected to the same-surface ground conductor layer 4 and the shield conductor 7 is provided with an opening of the waveguide 6 to which the waveguide 6 is attached. It is good to form according to. For example, as shown in FIG. 1, a ground conductor layer 8 made of a metallized layer connected to a shield conductor 7 made of a shielding through conductor may be formed on the lower surface of the dielectric layer 2. If such a ground conductor layer 8 is formed, the electrical connection between the waveguide 6 and the shield conductor 7 and the coplanar ground conductor layer 4 when the waveguide 6 is attached to the high-frequency line-waveguide converter. This is preferable in that a reliable high-frequency line-waveguide converter can be configured.

  In the high-frequency line-waveguide converter of the present invention, the shield conductor connection region R in the second ground conductor layer 8 projects into the opening 11 of the second ground conductor layer 8. With such a configuration, the high-frequency line-waveguide converter of the present invention can reduce impedance discontinuities. Therefore, the reflection loss in the high-frequency line-waveguide converter can be reduced, the transmission characteristics between the high-frequency line and the waveguide can be improved, and the usable band can be widened. The conversion efficiency of transmission to and from the wave tube can be increased.

  Further, as shown in FIG. 1, the high-frequency line-waveguide converter of the present invention has a connection region R of the shield conductor 7 in the second ground conductor layer 8 protruding into the opening 11 of the second ground conductor layer 8. However, by providing a plurality of shield conductors 7 corresponding to the plurality of shield conductors 7, impedance discontinuities can be further reduced.

  FIG. 2 shows a sectional view of another example of the embodiment of the high-frequency line-waveguide converter of the present invention. As shown in FIG. 2, the high-frequency line-waveguide converter of the present invention is provided with a dielectric plate 15 at a position located inside the waveguide 6 on the lower surface of the dielectric layer 2.

  Thus, the dielectric plate 15 in contact with the inside of the waveguide 6 having the strongest magnetic field of the TM mode, which is the resonance mode generated in the dielectric layer 2, and the dielectric layer 2 on which the high-frequency line 1 is formed are provided. Since it can be separated by the lower ground conductor layer 10, the TE mode, which is an electromagnetic field mode for transmitting the high-frequency line 1, and the TM mode are combined, and the signal energy transmitted through the high-frequency line 1 is shifted to the TM mode. It can be effectively prevented. As a result, it is possible to effectively prevent signal reflection due to resonance and perform good signal conversion from the high-frequency line 1 to the waveguide 6.

  Furthermore, since the periphery of the dielectric plate 15 is covered with the waveguide 6 without a gap, the grounding property can be improved by the waveguide 6, and the transmission property of the electromagnetic wave transmitted through the dielectric plate 15 can be improved. Can be better.

  The dielectric plate 15 may be integrated with the dielectric layer 2, or another dielectric plate 15 may be joined as shown in FIG. When joining another dielectric plate 15 in this way, a frame-shaped upper ground conductor layer 16 is formed on the upper surface of the dielectric plate 15, and a frame-shaped lower ground conductor layer 17 is formed on the lower surface of the dielectric plate 15. The upper ground conductor layer 16 and the lower ground conductor layer 10 can be joined by brazing with an Au—Sn brazing material or the like.

  In this way, when another dielectric plate 15 is bonded to the dielectric layer 2, it is only necessary to bond the dielectric plate 15 adjusted to a desired thickness as compared with a case where these are integrally manufactured. The manufacturing yield can be improved by effectively preventing the occurrence of defects due to the thickness variation of 15 and the thickness of the dielectric plate 15 can be made very accurate. As a result, the light is radiated from the slot 5 and reflected at the interface between the lower surface of the dielectric plate 15 and the inside of the waveguide 6, reflected again by the lower ground conductor layer 10, and again reflected from the lower surface of the dielectric plate 15 and the waveguide 6. It effectively prevents the path difference between the reflected wave that has returned to the interface with the inside and the direct wave transmitted from the slot 5 to the interface between the lower surface of the dielectric plate 15 and the inside of the waveguide 6 from varying. The dispersion of the transmission characteristics of the electromagnetic wave guided to the waveguide 6 by overlapping the wave and the reflected wave can be extremely reduced.

(A) is a top view which shows the example of embodiment of the high frequency line-waveguide converter of this invention, (b) is in the AA 'line of the high frequency line-waveguide converter of (a). It is sectional drawing, (c) is a top view of the grounding conductor layer 8 of the high frequency line-waveguide converter of (a). It is sectional drawing which shows the other example of embodiment of the high frequency line-waveguide converter of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... High frequency line 2 ... Dielectric layer 3 ... Line conductor 4 ... Same surface grounding conductor layer 5 ... Slot 6 ... Conduction Wave tube 7 ... Shield conductor 8 ... Ground conductor layer 11 ... Opening of the ground conductor layer

Claims (2)

A dielectric layer having first and second surfaces;
A high-frequency line formed on the first surface of the dielectric layer and comprising a line conductor and a first ground conductor layer surrounding an end of the line conductor;
A slot that is formed on the first surface of the dielectric layer so as to intersect the line conductor, and is electromagnetically coupled to the line conductor;
A second grounding conductor layer formed on an inner layer or the second surface of the dielectric layer and having an opening facing the slot;
A shield conductor that is formed inside the dielectric layer and electrically connects the first ground conductor layer and the second ground conductor layer;
A high-frequency line-waveguide converter, wherein a connection region of the shield conductor in the second ground conductor layer protrudes into the opening of the second ground conductor layer. A plurality of the shield conductors are formed;
The connection region of the shield conductor in the second ground conductor layer protruding from the opening of the second ground conductor layer is provided corresponding to the plurality of shield conductors. 1. The high-frequency line-waveguide converter according to 1.

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