Patent Publication Number: US-8970440-B2

Title: Waveguide/planar line converter

Description:
TECHNICAL FIELD 
     The present invention relates to a waveguide/planar line converter, and more specifically to a waveguide/planar line converter provided with a waveguide through which microwaves or millimeter waves are electrically transmitted, and a planar line substrate for amplifying or converting the frequency of these waves. 
     BACKGROUND ART 
     In order to amplify microwaves or millimeter waves electrically transmitted through a waveguide, or in order to convert the frequency thereof, a waveguide/planar line converter is provided in an interface unit joining a waveguide and a planar line circuit. 
     Patent Literature 1 discloses a waveguide/planar line converter including a cylindrical waveguide and a planar line substrate furnished on this waveguide. 
     The planar line substrate includes a laminated structure in the vertical direction. The top layer of the planar circuit substrate is formed in a frame shape compatible with the opening end in the waveguide, and includes a first grounding conductor to which the opening end of this waveguide is adhered and anchored to, and an antenna pattern positioned within the frame of this grounding conductor which comprises a λ/2 resonant antenna. 
     In addition, the bottom layer of the planar line substrate includes a strip conductor the tip of which extends as far as a position opposite the antenna pattern, and a second grounding conductor positioned surrounding this strip conductor. 
     PRIOR ART LITERATURE 
     Patent Literature 
     Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. H08-139504 
     SUMMARY OF INVENTION 
     Problems to be Solved by the Invention 
     With the waveguide/planar line converter noted in Patent Literature 1, an electric field is generated inside the waveguide when electrically transmitting via the waveguide. At such times, the position of the maximum electric field inside the waveguide is on the center line of the waveguide in the direction of width, and the direction of this maximum electric field is a direction facing from one side to the other side in this center line and is orthogonal to the direction in which the planar line substrate is laminated. On the other hand, at this time an electric field is generated near the edge of the antenna pattern in the planar line substrate in the direction in which the planar line substrate is laminated. Because this electric field has a direction differing from the aforementioned maximum electric field generated inside the waveguide, the joining of the electromagnetic field distribution caused by the antenna pattern and the electromagnetic field distribution caused by the waveguide is suppressed. Through this, the conversion properties of the waveguide/planar line converter deteriorate. 
     In consideration of the foregoing, it is an object of the present invention to provide a waveguide/planar line converter having superior conversion properties. 
     Means for Solving the Problem 
     In order to achieve the above object, the waveguide/planar line converter according to the present invention comprises a waveguide and a planar line substrate to which an opening end of the waveguide is adhered and anchored; wherein a pair of antenna patterns is positioned facing each other with a gap in between, surrounding the opening end of the waveguide on the planar line substrate; and the waveguide and the pair of antenna patterns are positioned such that the position and direction of an electric field generated between the pair of antenna patterns match the position and direction of the maximum electric field inside the waveguide. 
     Effect of the Invention 
     With the present invention, the position and direction of the electric field generated between a pair of antenna patterns match the position and direction of the electric field generated inside the waveguide, so joining of the electromagnetic field distribution caused by the antenna patterns and the electromagnetic field distribution caused by the waveguide is easy. Through this, superior conversion properties can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded oblique view of a waveguide/planar line converter according to a first embodiment. 
         FIG. 2  is a planar view of a first conductor layer according to the first embodiment. 
         FIG. 3  is a planar view of a second conductor layer according to the first embodiment. 
         FIG. 4  is an exploded oblique view of the waveguide/planar line converter according to a second embodiment. 
         FIG. 5  is a planar view of a variation on the second conductor layer according to the second embodiment. 
         FIG. 6  is an exploded oblique view of the waveguide/planar line converter according to a third embodiment. 
         FIG. 7  is a planar view of a first conductor layer according to the third embodiment. 
         FIG. 8  is an exploded oblique view of the waveguide/planar line converter according to a fourth embodiment. 
         FIG. 9  is a planar view of a first conductor layer according to the fourth embodiment. 
         FIG. 10  is an exploded oblique view of the waveguide/planar line converter according to a fifth embodiment. 
         FIG. 11  is an exploded oblique view of the waveguide/planar line converter according to a sixth embodiment. 
         FIG. 12  is an exploded oblique view of the waveguide/planar line converter according to a seventh embodiment. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Below, the preferred embodiments of the present invention are described in detail with reference to the drawings. The same reference numbers are appended to the same or corresponding parts in the drawings. 
       FIG. 1  is an exploded oblique view of a waveguide/planar line converter  1  according to a first embodiment.  FIG. 1  shows with hatching solid parts in a first conductor layer  9  and a second conductor layer  11  in order to distinguish between solid parts and empty space (such as bored out parts). The same is true in the drawings below as well. 
     The waveguide/planar line converter  1  includes a rectangular-tube-shaped waveguide  3  through which microwaves or millimeter waves are electrically transmitted, and a planar line substrate  7  which is attached to the opening end  5  of the waveguide  3  and which accomplishes amplification and frequency conversion on these waves. Here, a direction parallel to the long axis of the opening end  5  of the waveguide  3  shall be called the widthwise direction, a direction parallel to the short axis thereof shall be called the heigthwise direction and the direction in which the waveguide  3  extends shall be the vertical direction. 
     The planar line substrate  7  is a thin plate comprising a first conductor layer  9  to which the waveguide  3  is connected, a second conductor layer  11  and a dielectric body  13  as an intermediate layer positioned between these two. Here, these layers are laminated in the vertical direction and bonded into a single body. The first conductor layer  9  and the second conductor layer  11  comprise a below-described pair of antenna patterns and a planar line connected to these antenna patterns. 
       FIG. 2  is a planar view of the first conductor layer according to the first embodiment. 
     The first conductor layer  9  is composed of a conductive thin film such as copper thin film, for example, and functions as a conductor-backed coplanar line. The first conductor layer  9  includes a pair of antenna patterns  15  and a first grounding conductor  17 . The pair of antenna patterns  15  is composed of two rectangular conductors arranged line-symmetrically with a prescribed gap GA positioned inside the opening end  5  of the waveguide  3 . The first grounding conductor  17  is positioned around the pair of antenna patterns  15  and is adhered and anchored to the opening end  5  of the waveguide  3 . 
       FIG. 3  is a planar view of the second conductor layer  11  according to the first embodiment. 
     The second conductor layer  11  is composed of a conductor thin film such as a copper thin film, for example, and functions as a coplanar line. The second conductor layer  11  includes a strip conductor  19  and a second grounding conductor  21 . The strip conductor  19  extends in a direction in which the antenna patterns  15  are lined, and faces each of the antenna patterns  15 . In addition, the strip conductor  19  is electrically connected to the antenna patterns  15  through via holes  23  passing through the dielectric body  13  in the direction of depth and being filled inside with a conductor. The second grounding conductor  21  is positioned around the strip conductor  19  and is electrically connected to the first grounding conductor  17  by via holes  25  passing through the dielectric body  13  in the direction of depth and filled inside with a conductor as similar to the via holes  23 . 
     As shown in  FIGS. 1 and 2 , the pair of antenna patterns  15  contact the part  29  overlapping the strip conductor  19  out of the junctions with the opening end  5  of the waveguide  3  and the first grounding conductor  17 , and the open ends  31  face each other with the gap GA interposed in between. Each of antenna patterns  15  in a pair comprises a λ/4 resonant antenna. Here, the resonant frequencies of these differ. 
     When electrically transmitting via the waveguide  3 , the position where the electric field inside the waveguide  3  is a maximum is on the center line B in the direction of width inside the waveguide  3 , and the direction of that maximum electric field is in the direction facing from one side to the other side on the center line B. In addition, with the planar line substrate  7 , between the pair of antenna patterns  15  (in other words, in the gap GA), an electric field directing from one antenna pattern  15  to the other antenna pattern  15  is generated by antenna coupling. In the present embodiment, the antenna patterns  15  are positioned such that the center line B of the waveguide  3  and the gap GA overlap. As a result, the position and direction of the electric field generated between the pair of antenna patterns  15  (in the gap GA) match the position and direction of the maximum electric field generated inside the waveguide  3 . 
     With the present embodiment, because the position and direction of the electric field generated between the pair of antenna patterns  15  as described above match the position and direction of the electric field generated inside the waveguide  3 , bonding between the electromagnetic field distribution from the antenna patterns  15  and the electromagnetic field distribution from the waveguides  3  becomes easy. Through this, a high conversion efficiency is obtained and conversion properties excel. 
     In addition, the antenna patterns  15  comprise λ/4 resonant antennas, so cross-polarized waves are theoretically not generated. For the same reason, even when symmetry in the shape of the antenna patterns  15  is lost due to manufacturing discrepancies, such as etching, generation of cross-polarized waves can be suppressed. In this manner, generation of electric power not coupled to the waveguide  3  or the strip conductor  19  from the antenna patterns  15  can be suppressed, so the waveguide/planar line converter  1  has reduced property deterioration caused by cross-polarized waves, and frequency properties excel. 
     In addition, the pair of antenna patterns  15  comprises resonant antennas whose resonant frequencies differ, so it is possible to cause double resonance neighboring the passthrough band of the resonant antennas. Through this, the bandwidth of the waveguide/planar line converter  1  becomes large compared to single resonance. 
     As explained above, with the present embodiment the pair of antenna patterns  15  is positioned facing each other with a gap GA inside the end  5  of the rectangular opening  4  of the waveguide  3 , as shown in  FIGS. 1 to 3 . The open ends of the pair of antenna patterns  15  face each other with the gap GA interposed in between. The gap GA is formed at a position where the center line D in the direction of height overlaps the center line C in the direction of height of the waveguide  3 . In addition, the pair of antenna patterns  15  is formed in a line-symmetrical shape centered on the center line D. Furthermore, the pair of antenna patterns  15  is formed at a position overlapping the center line B. 
     Next, second through seventh embodiments differing from the first embodiment will be described. Below, differences from the first embodiment and are mainly explained, and the same reference numbers are attached to common structures. 
       FIG. 4  is an exploded oblique view of the waveguide/planar line converter  35  according to a second embodiment. 
     In this embodiment, the via holes  23  shown in the first embodiment are omitted. The tip of the strip conductor  19  is an open end, and near the tip of the strip conductor  19  and one of the antenna patterns IS are electrically connected by a capacitance coupling. For parts where the capacitance bond is to be avoided, for example, the linewidth of the strip conductor  19  may be made finer or the dielectric constant of the dielectric body may be made lower than the surroundings. 
     With the present embodiment, it is possible to electrically connect the antenna patterns  15  and the strip conductor  19  without needing via holes. Through this, aligning the positions of the antenna patterns  15 , the strip conductor  19  and the via holes  25  becomes unnecessary, which is advantageous in terms of reducing variance in manufacturing. 
     With the present embodiment, a second conductor layer  12  shown in  FIG. 5  can be used in place of the second conductor layer  11 . With this second conductor layer  12 , the strip conductor  20  is connected at the tip thereof to the second grounding conductor  21  by a dielectric coupling, and is also connected to the antenna patterns  15  by a capacitance coupling. Even when using this second conductor layer  12 , the same effect as described above can be obtained. 
       FIG. 6  is an exploded oblique view of the waveguide/planar line converter  37  according to a third embodiment.  FIG. 7  is a planar view of a first conductor layer  39  according to the third embodiment. 
     With this embodiment, a semicircular pair of antenna patterns  41  each protruding toward the other, is provided on the first conductor layer  39  in place of the pair of antenna patterns  15 . Through this, there is no angled part of the outer edge of the antenna patterns  41 , so it is possible to reduce loss in the antennas. 
       FIG. 8  is an exploded oblique view of the waveguide/planar line converter  43  according to a fourth embodiment.  FIG. 9  is a planar view of a first conductor layer  45  according to the fourth embodiment. 
     With the present embodiment, a pair of antenna patterns  47 , each of which has a shape that gradually narrows away from the other, such as a trapezoid, is provided on the first conductor layer  45  in place of the pair of antenna patterns  15 . The width of the open ends  49  in these antenna patterns  47  is long compared to the width of the part  50  that contacts the first grounding conductor  17 . In this manner, the resonant frequency of the resonant antennas comprising the antenna patterns  47  becomes shorter. In order to raise the resonant frequency, it is desirable for the width of the part  50  that contacts the first grounding conductor  17  to be made long in comparison to the width of the open ends  49 , as opposite of the above. In addition, by regulating the width of the part  50  that contacts the first grounding conductor  17 , it is possible to change the operating frequency of the waveguide/planar line converter. 
       FIG. 10  is an exploded oblique view of the waveguide/planar line converter  53  according to a fifth embodiment. 
     The waveguide/planar line converter  53  according to this embodiment includes a shield cap  55  in addition to the configuration shown in  FIG. 1 . The shield cap  55  is positioned below the second conductor layer  11  and is connected to the second grounding conductor  21 . With the present embodiment, leakage of electric power from the bottom surface of the second conductor layer  11  is prevented by the shield cap  55 , so it is possible to avoid interference by this electric power with other elements of the planar circuit substrate. 
       FIG. 11  is an exploded oblique view of the waveguide/planar line converter  57  according to a sixth embodiment. 
     In the waveguide/planar line converter  57  according to this embodiment, the second grounding conductor  21  and the via holes  25  are omitted from the configuration shown in  FIG. 1 . At this time, the transmission line in the strip conductor  19  is composed of a microstrip line and is connected to the antenna patterns  15  through the via holes  23 . With the present embodiment, the structure of the waveguide/planar line converter is simplified. 
       FIG. 12  is an exploded oblique view of the waveguide/planar line converter  59  according to a seventh embodiment. 
     The waveguide/planar line converter  59  according to this embodiment includes a dielectric body  61  positioned below the second conductor layer  11  and a third conductor layer  63  positioned below the dielectric body  61  in addition to the configuration shown in  FIG. 1 . In other words, the planar line substrate  7  is a single thin plate in which the topmost layer is composed of the first conductor layer  9 , the bottommost layer is composed of the third conductor layer  63  and the intermediate layer between these is composed of the dielectric body  13 , the second conductor layer  11  and the dielectric body  61 . 
     A third grounding conductor  65  is formed on the third conductor layer  63 . The first grounding conductor  17  of the first conductor layer  9  is connected to the third grounding conductor  65  through via holes  67  filled with a conductor and penetrating the dielectric bodies  13  and  61  in the direction of depth, and is composed as a triplate line with respect to the strip conductor  19 . 
     With the present embodiment, the strip conductor  19  is interposed between the first grounding conductor  17  and the third grounding conductor  65 , so that a transmission line in which leakage is suppressed is composed on the planar line substrate  7 . In addition, the opening of the waveguide  3  is sealed by the planar line substrate  7 , so the waveguide/planar line converter  59  is provided with airtight functionality. 
     In the waveguide/planar line converter according to the present invention, the planar line substrate, preferably, includes a laminated structure in the vertical direction; a first layer of the topmost layer of the planar line substrate includes a pair of antenna patterns positioned with a gap and positioned inside the opening end of the waveguide, and a first grounding conductor positioned surrounding the pair of antenna patterns and adhered and anchored to the opening end of the waveguide; a second layer positioned below the topmost layer of the planar line substrate includes a strip conductor which extends in a direction in which the pair of antenna patterns is lined, faces the pair of antenna patterns and is connected to the pair of antenna patterns, and a second grounding conductor positioned surrounding the strip conductor and connected to the first grounding conductor; and the pair of antenna patterns contacts the area positioned directly above the strip conductor, out of the areas of the first grounding conductor adhered and anchored to the opening end of the waveguide. 
     In addition, preferably the open ends of the pair of antenna patterns face each other via the gap, and the gap is positioned directly below the center line inside the waveguide in the widthwise direction. 
     In addition, preferably the strip conductor is connected to the antenna patterns via a capacitance bond. 
     In addition, preferably a dielectric body is positioned between the first layer and the second layer. 
     In addition, preferably the pair of antenna patterns comprises λ/4 resonant antennas. 
     In addition, preferably the pair of antenna patterns comprises resonant antennas having differing resonant frequencies. 
     This application is the National Phase of PCT/JP2010/050574, filed Jan. 19, 2010, which claims the benefit of Japanese Patent Application No. 2009-8868 filed on Jan. 19, 2009, the entire disclosure of which is incorporated by reference herein. 
     INDUSTRIAL APPLICABILITY 
     With the present invention, it is possible to realize a waveguide/planar line converter having superior conversion properties. 
     EXPLANATION OF SYMBOLS 
     
         
           1 ,  35 ,  37 ,  43 ,  53 ,  57 ,  59  waveguide/planar line converter 
           3  waveguide 
           4  opening 
           5  opening end 
           7  planar line substrate 
           9 ,  39 ,  45  first conductor layer 
           11 ,  12  second conductor layer 
           13 ,  61  dielectric body 
           15 ,  41 ,  47  antenna pattern 
           17 ,  51  first grounding conductor 
           19 ,  20  strip conductor 
           21  second grounding conductor 
           23 ,  25 ,  67  via holes 
           27  contact 
           31  open end 
           49  open end 
           55  shield cap 
           63  third conductor layer 
           65  third grounding conductor