JP2006186437A - High frequency line-waveguide converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency line-waveguide converter exhibiting excellent transmission characteristics and high conversion efficiency by preventing generation of an unwanted mode effectively at the joint of a high frequency line and a waveguide. <P>SOLUTION: The high frequency line-waveguide converter comprises a first dielectric layer 2, a high frequency line 1 consisting of a line conductor 3 and a flush ground conductor layer 4, a slot 5 coupled electromagnetically with the line conductor 3, a lower ground conductor layer 8 formed on the lower surface of the first dielectric layer 2 in frame-shape surrounding the slot 5 in the plan view and being connected with a waveguide 6 at the outer circumferential part, and a shield conductor 7 formed to surround one end of the line conductor 3 and the slot 5 in the plan view and to connect the flush ground conductor layer 4 and the lower ground conductor layer 8 electrically wherein an upper ground conductor layer 9 is formed in frame-shape on the upper major surface of a second dielectric layer 10 having a dielectric constant smaller than that of the first dielectric layer 2, and the upper ground conductor layer 9 is soldered to the lower ground conductor layer 8 while opposing the openings to each other. <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, 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, there is a problem that the high frequency signal is attenuated by the high frequency line 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.

  FIG. 2 is a cross-sectional view for explaining the structure of the high-frequency front end. According to FIG. 2, the front end 60 is configured by connecting a module 61 and an antenna 62 with a waveguide member 63. The module 61 is mounted on a metal chassis 65 having a waveguide opening 64. The front end 60 has a high-frequency line composed of a microstrip substrate 66 on which a microstrip line as a high-frequency line is formed, and a waveguide composed of a waveguide opening 64 and a short-circuit termination member 67. A waveguide converter 68 is configured. A wiring board 69 on which high-frequency components are mounted is connected to the microstrip line of the microstrip board 66 by wire bonding.

The high-frequency line-waveguide converter 68 in the front end 60 is separated from the short-circuit termination surface of the short-circuit termination member 67 by a distance of 1/4 of the wavelength (intra-wavelength wavelength) of the electromagnetic wave excited by the high-frequency signal in the waveguide. The probe formed on the microstrip substrate 66 from the side surface of the waveguide (the portion where the line conductor is extended but the ground conductor is not formed) is approximately 1/4 of the signal wavelength. It is the type of inserted part.
JP 2001-177712 A International Publication No. 96/27913 Pamphlet

  However, this conventional high-frequency line-waveguide converter 68 is assembled so that a line conductor corresponding to a quarter of the guide wavelength is inserted into the waveguide. Due to the deviation, electromagnetic coupling variation occurs, and the conversion loss of the high-frequency line-waveguide converter is likely to increase. In this case, there is a problem that assembly is poor and all the used members are wasted.

  Further, the high-frequency line-waveguide converter 68 is in a state in which a line conductor corresponding to ¼ of the in-tube wavelength is inserted into the waveguide. Therefore, the high-frequency line-waveguide converter 68 is large. Had the problem of becoming.

  In order to solve such a problem, for example, 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 , 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 There has been proposed a high-frequency line-waveguide converter comprising:

  According to this configuration, the coplanar line and the slot are formed in the same plane, the relative positional relationship between the two is less likely to change, and the variation in the length of the protruding portion of the line conductor with respect to the slot is reduced. Therefore, variation in electromagnetic coupling can be reduced.

  The coplanar line ground plane conductor layer functions as a ground for the coplanar line, and the electromagnetic wave radiated from the slot is reflected at the interface between the dielectric layer and the inside of the waveguide and returns to the slot side (reflection). It also functions as a reflector that reflects the wave again.

  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.

  However, in this configuration, since the coplanar line and the matching unit made of the dielectric layer are in contact, a part of the electromagnetic wave of the signal transmitted through the coplanar line is distributed in the matching unit, which is an unnecessary electromagnetic wave in the matching unit. There is a problem in that a distribution (referred to as a mode here) is generated and transmission of a high-frequency signal to the waveguide is likely to be hindered.

  For example, just below the line conductor of the coplanar line, the magnetic field due to the signal is parallel to the surface of the dielectric layer. This magnetic field excites the TM mode, which is the resonance mode when the matching device is a dielectric waveguide, and the signal energy of the TE mode, which is the transmission mode, shifts to the TM mode and resonates to reflect the signal. There has been a problem that conversion to a waveguide cannot be performed satisfactorily.

  The present invention has been devised in view of the above problems, and its purpose is to effectively prevent the generation of unnecessary modes at the connection portion between the high-frequency line and the waveguide, thereby improving the transmission characteristics and high conversion efficiency. It is to provide a line-waveguide converter.

  The high-frequency line-waveguide converter of the present invention includes a first dielectric layer, a line conductor from the outer periphery of the upper surface of the first dielectric layer toward the center, and the upper surface of the first dielectric layer. A high-frequency line composed of the same-surface ground conductor layer formed so as to surround the line conductor, and formed on the same-surface ground conductor layer so as to be orthogonal to one end portion of the line conductor, and electromagnetically with the line conductor. A coupled slot, a lower ground conductor layer formed in a frame shape so as to surround the slot on the lower surface of the first dielectric layer, and having a waveguide connected to the outer periphery thereof; And a shield conductor formed to surround the one end of the line conductor and the slot and to electrically connect the coplanar ground conductor layer and the lower ground conductor layer. With a wave tube converter And forming a frame-like upper ground conductor layer on the upper principal surface of the second dielectric layer having a lower dielectric constant than the first dielectric layer, and the upper ground conductor layer being the lower ground conductor layer. Are characterized by being brazed with their openings facing each other.

  The high-frequency line-waveguide converter of the present invention forms a frame-like upper ground conductor layer on the upper main surface of the second dielectric layer having a lower dielectric constant than the first dielectric layer, and Since the ground conductor layer is brazed to the lower ground conductor layer with the openings facing each other, the TM mode, which is a resonance mode generated in the dielectric layer, has the strongest magnetic field and is in contact with the inside of the waveguide. The dielectric layer lower portion and the first dielectric layer and the second dielectric layer upper portion where the high frequency line is formed can be separated by the internal ground conductor layer, so that the electromagnetic field mode for transmitting the high frequency line can be used. It is possible to effectively prevent the signal energy transmitted through the high-frequency line from being combined with a certain TE mode and TM mode from shifting to the TM mode. As a result, signal reflection due to resonance can be effectively prevented, and good signal conversion from the high-frequency line to the waveguide can be performed.

  In addition, since the first and second dielectric layers are joined, it is only necessary to join the second dielectric layer adjusted to a desired thickness as compared with the case where these are integrally manufactured. The thickness of the dielectric layer, in particular, the thickness variation of the lower portion of the second dielectric layer below the internal ground conductor layer can be effectively prevented from causing a defect and the manufacturing yield can be improved. The thickness of the lower part of the dielectric layer can be made very accurate. As a result, it is radiated from the slot, reflected at the interface between the lower main surface of the second dielectric layer and the inside of the waveguide, reflected again by the internal ground conductor layer, and again below the second dielectric layer. Path difference between the reflected wave returning to the interface between the main surface and the inside of the waveguide and the direct wave transmitted directly from the slot to the interface between the lower main surface of the second dielectric layer and the inside of the waveguide It is possible to effectively prevent the dispersion of the electromagnetic wave, and to extremely reduce the variation in the transmission property of the electromagnetic wave guided to the waveguide by overlapping the direct wave and the reflected wave.

  Furthermore, since the periphery of the second dielectric layer is covered with a waveguide without a gap, the grounding property can be improved by the waveguide, and the electromagnetic wave transmitted through the second dielectric layer can be transmitted. The property can be made better.

  In addition, since the dielectric constant of the second dielectric layer is lower than the dielectric constant of the first dielectric layer, the capacitance component can be gradually changed when transmitting from the slot to the waveguide. Rapid changes can be mitigated. Therefore, it is possible to effectively improve the transmission performance at the connection portion between the high-frequency line and the waveguide and to widen the band.

  Next, the first invention in 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 according to the present invention, and FIG. 1B is a diagram of A of the high-frequency line-waveguide converter of FIG. FIG. In FIG. 1, 1 is a high-frequency line, 2 is a first dielectric layer, 3 is a line conductor, 4 is a common ground conductor layer, 5 is a slot formed in the common ground conductor layer 4, and 6 is a waveguide. , 7 is a shield conductor portion, 8 is a lower ground conductor layer, 9 is an upper ground conductor layer, and 10 is a second dielectric layer, which 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 first 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 first 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.

  The first dielectric layer 2 is a shield composed of a side conductor formed on the side surface of the first dielectric layer 2 or a through conductor disposed inside the first dielectric layer 2 as shown in FIG. Shielded by the conductor 7 and reflected at the interface between the electromagnetic wave radiated from the slot 5 into the first dielectric layer 2 and the lower main surface of the second dielectric layer 10 and the inside of the waveguide 6. Electromagnetic waves are prevented from leaking out and conversion efficiency is prevented from decreasing. In addition, the shield conductor part 7 is formed at a constant interval (less than 1/4 times the wavelength of the signal transmitted through the high-frequency line 1) so as to surround the slot 5 in a plan view.

  Further, a frame-like lower ground conductor layer 8 formed so as to surround the slot 5 in a plan view is disposed on the lower surface of the first dielectric layer 2, and the same-surface ground conductor layer 4 and the lower ground conductor layer 8 are The connection conductor 7 is connected. Further, a second dielectric layer 10 having a frame-like upper ground conductor layer 9 formed on the upper main surface is brazed to the lower ground conductor layer 8 with an Au—Sn brazing material or the like. The opening of the conductor layer 9 and the opening of the lower ground conductor layer 8 face each other.

  By adopting such a structure, the second dielectric layer 10 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, and the high-frequency line 1 are formed. Since the first dielectric layer 2 formed can be separated by the upper ground conductor layer 9 and the lower ground conductor layer 8, the TE mode and the TM mode, which are electromagnetic field modes that transmit the high-frequency line 1, are coupled. Thus, it is possible to effectively prevent the signal energy transmitted through the high-frequency line 1 from shifting to the 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.

  Examples of the dielectric material forming the first and second dielectric layers 2 and 10 include ceramic materials mainly composed of aluminum oxide, aluminum nitride, silicon nitride, mullite, glass, and a mixture of glass and ceramic filler. Used are glass ceramic materials formed by firing, organic resin materials such as epoxy resins, polyimide resins, fluororesins such as tetrafluoroethylene resin, and organic resin-ceramic (including glass) composite materials. It is done.

  In the present invention, the second dielectric layer 10 has a lower dielectric constant than the first dielectric layer 2. Preferably, the dielectric constant of the second dielectric layer 10 is 0.2 to 0.9 times that of the first dielectric layer 2. If it is less than 0.2 times, it is difficult to gradually change the capacitance component during transmission from the slot 5 to the waveguide 6, and it is difficult to mitigate a rapid change in impedance. On the other hand, if it exceeds 0.9 times, an abrupt change in impedance tends to occur between the first dielectric layer 2 and the second dielectric layer 10.

  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 lower ground conductor layer 8, and the upper ground conductor layer 9, tungsten, molybdenum, gold, silver, copper, etc. 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 tangent is small as the dielectric material forming the first and second dielectric layers 2 and 10, And it is desirable that airtight sealing is possible. 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, through holes are formed in the ceramic green sheets to be the first and second dielectric layers 2 and 10 for forming the shield conductor portion 7 as a through conductor by, for example, a punching method, A metallized paste is embedded in the through hole, and then the metallized paste is printed in the shape of the line conductor 3, the same-surface ground conductor layer 4, the lower ground conductor layer 8, and the upper ground conductor layer 9. Further, when the first and second dielectric layers 2 and 10 have a laminated structure of a plurality of dielectric layers, similarly, a ceramic green sheet printed with a metallized paste or embedded in a through hole is laminated, You may pressurize and pressure-bond.

  The ceramic green sheets to be the first and second dielectric layers 2 and 10 are fired at a high temperature (about 1600 ° C.). Furthermore, if necessary, 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 8, the upper ground conductor layer 9, and the like, for example, nickel plating and gold plating Adhere.

  Thereafter, the lower ground conductor layer 8 of the first dielectric layer 2 and the upper ground conductor layer 9 of the second dielectric layer 10 are brazed, and the second dielectric is formed on the outer periphery of the lower ground conductor layer 8. By connecting the waveguide 6 so as to surround the layer 10, a high-frequency line-waveguide converter is completed.

  The shield conductor portion 7 of the present invention is disposed on the side surface or the inside of the first dielectric layer 2 so as to surround the slot 5 and electrically connects the same-surface ground conductor layer 4 and the lower 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 lower 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 first dielectric layer 2, a so-called castellation conductor in which a conductor layer is deposited on the inner wall of the cutout portion on the side surface of the first dielectric layer 2, A so-called through-hole conductor in which a conductor layer is deposited on the inner wall, a so-called via conductor in which the inside of the through hole is filled with a conductor, and the like can be given.

  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 8 by joining with a brazing material, tightening with a screw or the like, and the waveguide 6 and the lower ground conductor layer 8 are electrically connected.

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

  The thickness of the second dielectric layer 10 is preferably not more than ½ times the wavelength of the signal transmitted through the high-frequency line 1. As a result, the light is radiated from the slot 5 and reflected at the interface between the lower main surface of the second dielectric layer 10 and the inside of the waveguide 6, reflected again by the upper ground conductor layer 9, and again reflected by the second dielectric. The reflected wave returning to the interface between the lower main surface of the layer 10 and the inside of the waveguide 6, and directly from the slot 5 to the interface between the lower main surface of the second dielectric layer 10 and the inside of the waveguide 6 The transmitted direct wave can be in phase, and the reflected wave and the direct wave are intensified, so that the conversion efficiency from the high-frequency line 1 to the waveguide 6 can be further increased.

  The opening area of the upper ground conductor layer 9 may be larger or smaller than the opening area of the lower ground conductor layer 8. Or it may be the same. Preferably, the opening area of the upper ground conductor layer 9 is larger than the opening area of the lower ground conductor layer 8. Thus, a sudden change in impedance when electromagnetic waves are transmitted from the slot 5 formed in the high-frequency line 1 to the waveguide 6 can be mitigated by the ground conductor layer whose opening area is gradually increased. Therefore, it is possible to effectively improve the transmission performance at the connection portion between the waveguide 6 and the waveguide 6.

  More preferably, the opening area of the upper ground conductor layer 9 is 1.1 times or more than the opening area of the lower ground conductor layer 8. When the upper ground conductor layer 9 and the lower ground conductor layer 8 are brazed to be less than 1.1 times, the opening area in a state where the lower ground conductor layer 8 and the upper ground conductor layer 9 are joined due to misalignment Tends to vary, and variations in conversion efficiency are likely to occur.

  Further, there is a gap between the lower surface of the first dielectric layer 2 exposed inside the lower ground conductor layer 8 and the upper main surface of the second dielectric layer 10 exposed inside the upper ground conductor layer 9. It is good to be. As a result, the electromagnetic wave radiated from the slot 5 and reflected at the interface between the lower main surface of the second dielectric layer 10 and the inside of the waveguide 6 is reflected to the second dielectric layer inside the upper ground conductor layer 9. 10 and the gap can be favorably reflected, and the conversion efficiency can be further improved.

  Preferably, the distance between the lower surface of the first dielectric layer 2 exposed inside the lower ground conductor layer 8 and the upper main surface of the second dielectric layer 10 exposed inside the upper ground conductor layer 9 is It is good that it is 1-15 μm. If it is less than 1 μm, the effect of further improving the conversion efficiency tends to be small. On the other hand, if it exceeds 15 μm, the change in impedance becomes large and loss tends to occur.

  A dielectric is deposited on the lower surface of the first dielectric layer 2 exposed inside the lower ground conductor layer 8 and the upper main surface of the second dielectric layer 10 exposed inside the upper ground conductor layer 9. You may let them. Thereby, the dielectric loss between the 1st dielectric material layer 2 and the 2nd dielectric material layer 10 can be changed gradually, and it can control effectively that a reflective loss etc. arise.

  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 first dielectric layer 2, and the line conductor 3 is formed on the upper surface of the dielectric layer. It is good also as a coplanar line structure with a ground which provided the grounding conductor layer so that may be covered.

(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. It is sectional drawing which shows the example of the conventional high frequency track-waveguide converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... High frequency line 2 ... 1st dielectric material layer 3 ... Line conductor 4 ... Same surface grounding conductor layer 5 ... Slot 6 ... ································································································ 9

Claims (1)

A first dielectric layer, a line conductor extending from the outer periphery of the upper surface of the first dielectric layer toward the center, and the same interview formed so as to surround the line conductor on the upper surface of the first dielectric layer; A high-frequency line composed of a ground conductor layer; a slot formed on the same-surface ground conductor layer so as to be orthogonal to one end of the line conductor and electromagnetically coupled to the line conductor; and the first dielectric layer A lower ground conductor layer which is formed in a frame shape so as to surround the slot in a plan view and is connected to a waveguide on the outer periphery, and surrounds the one end portion and the slot of the line conductor in a plan view. And a shield conductor portion formed so as to electrically connect the coplanar ground conductor layer and the lower ground conductor layer, wherein the first dielectric Dielectric than body layer A frame-like upper ground conductor layer is formed on the upper main surface of the second low dielectric layer, and the upper ground conductor layer is brazed with the lower ground conductor layer facing each other's openings. A high-frequency line-waveguide converter.

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