JP2006238055A - High-frequency line/waveguide converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency line/waveguide converter having high conversion efficiency. <P>SOLUTION: The high-frequency line/waveguide converter is provided with: a high-frequency line 1 consisting of a line conductor 3 formed on the upper surface of the dielectric layer 2 and a identical-plane grounding conductor layer 4 formed on the upper surface of the dielectric layer 2 so as to surround the one-end part of the line conductor 3; a slot 5 formed in the identical-plane grounding conductor layer 4 so as to intersect with the one-end part of the line conductor 3 at right angles and electromagnetically coupled with the line conductor 3; a grounding conductor layer 8 where an aperture is formed on the inner layer or lower surface of the dielectric layer 2 so as to surround the slot 5 in plane perspective; and a shield conductor part 7 formed so as to surround the one-end part of the line conductor 3 and the slot 5 in plane perspective and electrically connect the identical-plane grounding conductor layer 4 and the grounding conductor layer 8, wherein the center of gravity of the aperture of the grounding conductor layer 8 is located so as to be deflected to the tip side of the line conductor 3 from the center of gravity of the slot 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 used in a microwave or millimeter-wave region into a waveguide, and connecting 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, there is a problem that the high-frequency signal is attenuated by a high-frequency line such as a microstrip line structure constituting the circuit due to the high frequency of the high-frequency signal.

  It is known that a transmission loss of a high-frequency signal is small in a waveguide as compared with a high-frequency line such as a microstrip line structure. For example, compared to the impedance (50Ω) of a normal high-frequency line such as a microstrip line, the impedance of the waveguide (which varies depending on the frequency but is designed on the order of about 500Ω) is large. The contribution of the electric field transmitted through the dielectric to the generated signal is large, whereas the waveguide uses air having a dielectric loss tangent of almost zero as its dielectric, The current flowing through the waveguide tube wall can be small, and since the current flows in a relatively large area of the waveguide tube wall, the electrical resistance is reduced and the conductor loss is reduced. Is due to being.

  The waveguides are usually connected with screws. Therefore, since it can be easily attached and detached, if a waveguide is used for the connection between the high-frequency circuit module and the antenna, each inspection is performed using each waveguide port before assembly, and non-defective products are combined. A high-frequency front end can be assembled, and the manufacturing yield can be increased. For these reasons, a front end using a waveguide for transmission between a high-frequency circuit module and an antenna, which often has a long transmission distance, has been conventionally used.

  Such a high-frequency front end 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 of the dielectric layer, and an antenna formed on 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 portion formed so as to connect the waveguide and the same-surface grounded conductor layer inside the dielectric layer. A high-frequency line-waveguide converter is proposed (see Patent Document 1 below).

  According to this converter, by setting the distance from the slot to the interface between the dielectric layer and the inside of the waveguide to be ¼ of the wavelength of the electromagnetic wave transmitted through the dielectric layer, The path difference between the reflected wave reflected at the interface between the layer and the inside of the waveguide, reflected again from the ground conductor layer on the same plane and reaching the interface, and the electromagnetic wave transmitted directly from the slot to the interface (direct wave) Since the phase is inverted when the reflected wave magnetic field is reflected at the interface between the dielectric layer and the inside of the waveguide, the direct wave and the reflected wave are in phase at the interface. Will propagate to the waveguide.

That is, the dielectric layer interposed between the slot and the waveguide and having a thickness set to ¼ of the wavelength of the electromagnetic wave functions as a matching unit between the slot and the waveguide having different impedances. Become.
JP 2004-32321 A

  However, since the transmission mode of the high-frequency line-waveguide converter differs between the high-frequency line and the slot, the characteristic impedance of each transmission line changes, resulting in an increase in reflection loss between the high-frequency line and the slot. There was a problem that efficiency deteriorated.

  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 conversion efficiency.

  The high-frequency line-waveguide converter of the present invention includes a line conductor formed on an upper surface of a dielectric layer and a coplanar ground conductor layer formed so as to surround one end of the line conductor on the upper surface of the dielectric layer. A high-frequency line comprising: a slot formed on the same-surface ground conductor layer so as to be orthogonal to the one end of the line conductor and electromagnetically coupled to the line conductor; and an inner layer or a lower surface of the dielectric layer A ground conductor layer having an opening formed so as to surround the slot when seen in a plan view, and surrounding the one end portion and the slot of the line conductor when seen in a plan view, and the coplanar ground conductor layer and the ground conductor layer A high-frequency line-waveguide converter comprising a shield conductor portion formed so as to be electrically connected to each other, wherein the center of gravity of the opening of the ground conductor layer is set to be higher than the center of gravity of the slot. Characterized in that is positioned at the front end side of the body.

  The high-frequency line-waveguide converter of the present invention is formed between the line conductor and the ground conductor layer because the center of gravity of the opening of the ground conductor layer is positioned closer to the tip end side of the line conductor than the center of gravity of the slot. Therefore, the impedance of the slot portion can be increased. Therefore, a large impedance difference between the slot having a lower impedance than the high-frequency line and the high-frequency line can be alleviated, and a sudden impedance change can be effectively prevented to suppress reflection loss. As a result, the conversion efficiency can be made very high.

  Next, the invention of the present invention will be described in detail based on the attached material. 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. It is AA 'line sectional drawing of. In FIG. 1, 1 is a high-frequency line, 2 is a dielectric layer, 3 is a line conductor, 4 is a ground conductor layer on the same plane, 5 is a slot formed in the ground conductor layer 4 on the same plane, 6 is a waveguide, The shield conductor portion 8 is a ground conductor layer. These mainly form a high-frequency line-waveguide converter.

  The high-frequency line 1 is formed in a coplanar line shape by a line conductor 3 formed on the upper surface of the dielectric layer 2 and a coplanar ground conductor layer 4 formed so as to surround the line conductor 3. Further, a slot 5 is provided in the same grounded conductor layer 4 on the upper surface 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.

  As shown in FIG. 1, the end of the line conductor 3 may be short-circuited with the same-surface ground conductor layer 4 to be a short-circuited end, or may be an open end without being short-circuited.

  Further, the dielectric layer 2 is shielded by a shield conductor portion 7 formed of a side conductor formed on the side surface or a through conductor disposed inside the dielectric layer 2 as shown in FIG. The electromagnetic wave radiated into the body layer 2 and the electromagnetic wave reflected at the interface between the lower surface of the dielectric layer 2 and the inside of the waveguide 6 are prevented from leaking, and the conversion efficiency is prevented from being lowered. The shield conductor portion 7 is formed with a constant 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 lower surface of the dielectric layer 2, and the same-surface ground conductor layer 4 and the ground conductor layer 8 are shielded. The conductors 7 are connected.

  In the high-frequency line-waveguide converter of the present invention, the center of gravity of the opening 8a of the ground conductor layer 8 is closer to the tip side of the line conductor 3 than the center of gravity of the slot 5 (in FIG. Side). That is, when viewed through the plane, the opening 8a of the ground conductor layer 8 has a distance B between the outer periphery of the opening 8a and the outer periphery of the slot 5 on the tip end of the line conductor 3 (in FIG. 1, the short-circuited end with the same-surface ground conductor layer 4). The distance A is larger than the distance A on the opposite side.

  With this configuration, the capacitance formed between the line conductor 3 and the ground conductor layer 4 can be reduced, and the impedance of the slot portion can be increased. Therefore, a large impedance difference between the slot 5 having a lower impedance than the high-frequency line 1 and the high-frequency line 1 can be alleviated, and a sudden change in impedance can be effectively prevented to suppress reflection loss. As a result, the conversion efficiency can be made very high.

  Preferably, the distance B is 1.1 to 5.5 times the distance A. If the ratio is less than 1.1 times, a large impedance difference between the slot 5 and the high-frequency line 1 is relaxed, and an effect of effectively preventing a sudden impedance change and suppressing reflection loss tends to be reduced. If it exceeds 5.5 times, the distance between the shield conductor portion 7 and the slot 5 becomes large, the transmission performance is lowered, and the conversion characteristics are easily deteriorated.

  Preferably, the ground conductor layer 8 is formed in the inner layer of the dielectric layer 2. By adopting such a multilayer structure, the lower dielectric layer 2 in contact with the inside of the waveguide 6 having the strongest magnetic field of the TM mode, which is a resonance mode generated in the dielectric layer 2, and the high-frequency line 1 Can be separated from the upper dielectric layer 2 by the inner ground conductor layer 8, so that the TE mode and the TM mode, which are electromagnetic field modes for transmitting the high-frequency line 1, are combined to form the high-frequency line 1. Can be effectively prevented from shifting to TM mode. 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.

  Alternatively, the ground conductor layer 8 may be formed on the inner layer of the dielectric layer 2, and the lower ground conductor layer 11 for joining the waveguide 6 to the lower surface of the dielectric layer 2 may be formed. The lower ground conductor layer 11 is preferably a frame formed so as to surround the slot 5 in a plan view.

  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.

  As the conductor material for forming the line conductor 3, the same-surface ground conductor layer 4, the shield conductor portion 7 such as the through conductor, the ground conductor layer 8, and the lower ground conductor layer 11, tungsten, molybdenum, gold, silver, copper, and the like are used. Metallization having a main component or metal foil having gold, silver, copper, aluminum or the like as a main component is 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 the shield conductor portion 7 that is 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, Subsequently, a metallized paste is printed in the shape of the line conductor 3, the same-surface ground conductor layer 4, and the ground conductor layer 8. Further, when the dielectric layer 2 has a laminated structure of a plurality of dielectric layers, similarly, a metallized paste is printed on the surface and a ceramic green sheet embedded in the through hole is laminated, and pressed and pressed. May be.

  And the ceramic green sheet used as these dielectric material layers 2 is baked at high temperature (about 1600 degreeC). Furthermore, if necessary, for example, nickel plating and gold plating are applied to the surface of the conductor exposed on the upper and lower surfaces such as the line conductor 3, the same-surface ground conductor layer 4, the lower ground conductor layer 11, and the like. By connecting the waveguide 6 to the outer periphery of the ground conductor layer 11, a high-frequency line-waveguide converter is completed.

  The shield conductor portion 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, the ground conductor layer 8, and the lower ground conductor layer 11. ing.

  The shield conductor portion 7 only needs to be able to electrically connect the same-surface ground conductor layer 4, the ground conductor layer 8, and the lower ground conductor layer 11, 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 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 lower ground conductor layer 11 by joining with a brazing material, tightening with a screw, or the like, and the waveguide 6 and the lower ground conductor layer 11 are electrically connected.

  The length of the slot 5 in the direction orthogonal to the line conductor 3 is preferably equal to or shorter than the wavelength of the signal transmitted through the high-frequency line 1. Further, the width of the slot 5 in the direction parallel to the line conductor 3 is preferably not more than ½ times the wavelength of the signal transmitted through the high-frequency line 1. Thereby, electromagnetic waves can be radiated favorably from the high-frequency line 1 to the waveguide 6.

  When the ground conductor layer 8 is not inside the dielectric layer 2 but on the lower surface, the thickness of the dielectric layer 2, that is, the distance between the high frequency line 1 and the ground conductor layer 8 is transmitted through the high frequency line 1. It is good that it is 1/2 times or less of the wavelength of the signal. As a result, the light is radiated from the slot 5, reflected at the interface between the lower surface of the dielectric layer 2 and the inside of the waveguide 6, reflected again at the upper surface of the dielectric layer 2, and guided again to the lower surface of the dielectric layer 2. The reflected wave returning to the interface with the inside of the tube 6 and the direct wave transmitted directly from the slot 5 to the interface between the lower surface of the dielectric layer 2 and the inside of the waveguide 6 can be in phase and reflected. Since the wave and the direct wave strengthen each other, the conversion efficiency from the high-frequency line 1 to the waveguide 6 can be further increased.

  When there is one ground conductor layer 8 inside the dielectric layer 2, the thickness of the lower dielectric layer 2, that is, the distance between the ground conductor layer 4 and the lower surface of the dielectric layer 2 is determined by the high frequency line. 1 or less of the wavelength of the signal transmitting 1 is preferable. As a result, the light is radiated from the slot 5, reflected at the interface between the lower surface of the dielectric layer 2 and the inside of the waveguide 6, reflected again by the internal ground conductor layer 8, and guided again to the lower surface of the dielectric layer 2. The reflected wave returning to the interface with the inside of the tube 6 and the direct wave transmitted directly from the slot 5 to the interface between the lower surface of the dielectric layer 2 and the inside of the waveguide 6 can be in phase and reflected. Since the wave and the direct wave strengthen each other, the conversion efficiency from the high-frequency line 1 to the waveguide 6 can be further increased.

  Further, the shape of the opening 8a of the ground conductor layer 8 is preferably similar to that of the slot 5, and the area of the opening 8a of the ground conductor layer 8 is preferably 5 to 30 times the opening area of the slot 5. Thereby, the rapid change of the impedance from the high frequency line 1 to the waveguide 6 can be relieved, and electromagnetic waves can be transmitted satisfactorily.

  It should be noted that the present invention is not limited to the embodiments described above, and various modifications may be made without departing from the spirit of the present invention.

  For example, FIG. 1 shows an example in which the high-frequency line 1 has a coplanar line structure. For example, a dielectric layer is further laminated on the dielectric layer 2 and the line conductor 3 is covered on the upper surface of the dielectric layer. A grounded coplanar line structure in which a ground conductor layer is provided on the dielectric layer 2, the line conductor 3, the coplanar ground conductor layer 4, the slot 5, the waveguide 6, the shield conductor portion 7, and the ground conductor layer 8. By making the positional relationship similar to the example shown in FIG. 1, the same effect can be obtained.

(A) is a top view which shows the example of embodiment of the high frequency line-waveguide converter of this invention, (b) is the cross section in the AA 'line of the high frequency line-waveguide converter of (a). FIG.

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

Claims (1)

A line conductor formed on the top surface of the dielectric layer, a high-frequency line comprising a ground conductor layer on the same plane formed so as to surround one end of the line conductor on the top surface of the dielectric layer, and a ground conductor layer on the same plane A slot that is formed to be orthogonal to the one end of the line conductor and electromagnetically coupled to the line conductor, and an opening is formed in the inner layer or the lower surface of the dielectric layer so as to surround the slot in a plan view. A shield conductor formed so as to surround the one end portion of the line conductor and the slot and to electrically connect the same-surface ground conductor layer and the ground conductor layer, as seen through a plane, and to form the ground conductor layer formed A high-frequency line-waveguide converter, wherein the center of gravity of the opening of the ground conductor layer is positioned closer to the tip side of the line conductor than the center of gravity of the slot. That the high-frequency line - waveguide converter.

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