JP2020068489A - Transmission line structure - Google Patents

Abstract

To obtain a transmission line structure that makes it easy to secure broadband characteristics.SOLUTION: A transmission line structure includes a first waveguide 40, an impedance adjusting unit 50 including a transformer waveguide 51 that is provided on one end side in the waveguide direction of the first waveguide 40 and has an H surface that is narrower than the H surface of the first waveguide 40, and a second waveguide 60 connected to the transformer waveguide 51 via a slit 55, having a lower impedance than that of the first waveguide 50, and extending in a direction intersecting an E surface of the first waveguide 50.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a transmission line structure.

  A waveguide (a hollow rectangular waveguide) is often used for input to an antenna for a very high frequency such as a millimeter wave antenna. Further, as an antenna for a very high frequency such as a millimeter wave antenna, a printed circuit board antenna is used because of its low cost. A microstrip line formed on a printed circuit board is often used for feeding power to the printed circuit board antenna.

K. Seo, “Planar Microstrip-To-Waveguide Transition in Millimeter-Wave Band,” Advancement in Microstrip Antennas with RecentApplications, ed. A. Kishk, pp.249-277, 2013. [Search on September 25, 2018] , Internet <URL: https: //www.intechopen.com/books/advancement-in-microstrip-antennas-with-recent-applications>

  Therefore, the transmission line for feeding power is composed of the waveguide and the microstrip line. As a result, a converter (waveguide-microstripline converter) for converting a mode between the waveguide and the microstripline is required.

  In order to secure the wide band property of the antenna, the waveguide-microstrip line converter also needs to have the wide band property. For example, in the millimeter wave radar, the band is 1 GHz in the 76 GHz band, but is 4 GHz in the 79 GHz band. Therefore, a broader waveguide-microstripline converter is desired. However, widening the band is not easy.

  Here, Non-Patent Document 1 discloses a structure for waveguide-microstrip line conversion in the millimeter wave band. The structure disclosed in Non-Patent Document 1 is one in which a waveguide is connected to a printed circuit board on which microstrip lines are formed. In Non-Patent Document 1, the waveguide-microstrip line conversion is realized by a metal component called back short mounted on a printed circuit board. However, the structure of Non-Patent Document 1 requires a component called back short circuit, which causes an increase in cost. Further, it is necessary to attach the back short to the printed circuit board, which complicates the manufacturing work.

  The present inventors have found a novel transmission line structure suitable for realizing broadband waveguide-microstrip line conversion and the like without using a component such as a back short.

  An aspect of the present disclosure relates to a transmission line structure. The transmission line structure includes a first waveguide and an impedance adjustment including a transformer waveguide that is provided on one end side of the first waveguide in the waveguide direction and has an H-plane that is narrower than the H-plane of the first waveguide. And a second waveguide connected to the transformer waveguide through a slit, having a lower impedance than the first waveguide, and extending in a direction intersecting the E plane of the first waveguide.

  According to the present disclosure, it is possible to obtain a transmission line structure in which it is easy to secure a wide band property.

FIG. 1 is a plan view of the antenna device. FIG. 2 is a sectional view of the antenna device. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a sectional view taken along line IV-IV of FIG. FIG. 5 is a sectional view taken along line VV of FIG. FIG. 6 is a sectional view taken along line VI-VI of FIG. FIG. 7 is a cross-sectional view of the modified example of FIG. FIG. 8 is a sectional view of the equivalent circuit of FIG. FIG. 9 is a cross-sectional view of the modified example of FIG. FIG. 10 is a plan view of the antenna device according to the second embodiment. FIG. 11 is a plan view of the antenna device according to the second embodiment. It is a polar chart which shows the simulation result of 1st Embodiment. It is a VSWR characteristic view which shows the simulation result of 1st Embodiment. FIG. 14A is a polar chart of a reflection characteristic when there is no stub in the third embodiment. FIG. 14B is a polar chart of the reflection characteristic in the case of the third embodiment (with stub). FIG. 15A is a VSWR characteristic diagram of the reflection characteristic when there is no stub in the third embodiment. FIG. 15B is a VSWR characteristic diagram of the reflection characteristic in the case of the third embodiment (with stub). FIG. 16A is a pass characteristic diagram when there is no stub in the third embodiment. FIG. 16B is a pass characteristic diagram in the case of the third embodiment (with stubs).

[1. Outline of Embodiment]

(1) The transmission path structure of the embodiment has a first waveguide and a transformer provided on one end side of the first waveguide in the waveguide direction and having an H-plane narrower than the H-plane of the first waveguide. An impedance adjusting unit including a waveguide, and a second waveguide connected to the transformer waveguide through a slit, having a lower impedance than the first waveguide, and extending in a direction intersecting the E plane of the first waveguide. And According to this transmission path structure, the first waveguide is converted into the second waveguide having a low impedance, so that it becomes easy to secure the wide band property when the second waveguide is connected to the microstrip line.

(2) The transmission line structure includes a microstrip line formed on a printed circuit board, a converter for the second waveguide and the microstrip line formed on the printed circuit board,
Can be further provided. The second waveguide is preferably formed on the printed circuit board. In this case, it is easy to secure a wide band property in the converter.

(3) The transmission line structure preferably further includes an antenna formed on the printed circuit board and fed by the microstrip line. In this case, an integrated structure in which the second transmission line, the microstrip line, the converter, and the antenna are formed on the printed circuit board is obtained.

(4) It is preferable that the second waveguide is a substrate integrated waveguide in which a post wall is constituted by a plurality of vias connecting the first conductor pattern and the second conductor pattern serving as a ground plane. In this case, a thin second waveguide having a low impedance can be easily obtained.

(5) It is preferable that the impedance adjusting section includes one or a plurality of impedance adjusting vias provided in a range surrounded by the plurality of vias forming the post wall in the substrate integrated waveguide. In this case, impedance adjustment becomes easy.

(6) The first conductor pattern has a pattern end serving as an output end of the substrate integrated waveguide, and of the plurality of vias forming the post wall, the center of the output end via closest to the pattern end. To the end of the pattern is preferably 0.1 λg or less (λg is a wavelength in the substrate integrated waveguide). In this case, it is possible to prevent an electromagnetic wave leakage path from the output end via to the pattern end.

(7) The first conductor pattern has a pattern end serving as an output end of the substrate integrated waveguide,
It is preferable to have an output end via closest to the pattern end among the plurality of vias forming the post wall and a stub for shorting the pattern end. In this case, it is possible to suppress a leakage path from the output end via to the pattern end by short-circuiting from the output end via to the pattern end.

(8) It is preferable that the stub is an open stub formed at a position that short-circuits the output end via and the pattern end. In this case, it is possible to easily make a short between the output end via and the pattern end.

(9) When a short is made between the output end via and the pattern end by the stub, the length from the center of the output end via to the pattern end is 0.1 λg (λg is a wavelength in the substrate integrated waveguide. ) May be greater than. Even if the length from the output end via to the pattern end is large, a short circuit between the output end via and the pattern end prevents a leakage path from the output end via to the pattern end. it can.

(10) The impedance of the second waveguide is preferably 1/45 or more of the impedance of the first waveguide and 1 / 1.2 or less of the impedance of the first waveguide.

(11) The impedance of the second waveguide is preferably 1/20 or more of the impedance of the first waveguide.

(12) The impedance of the second waveguide is preferably 1 / 1.3 or less of the impedance of the first waveguide.

[2 Details of Embodiment]

[2.1 Antenna Device Having Transmission Line Structure According to First Embodiment]

  1 to 6 show an antenna device 10 having a transmission line structure according to the first embodiment. The antenna device 10 is for millimeter wave radar, for example, and is used for receiving or transmitting electromagnetic waves. In the following description, the antenna device 10 is assumed to be for 76.5 GHz (wavelength λ: 3.92 mm) as an example.

  As shown in FIG. 2, the antenna device 10 according to the embodiment includes a printed circuit board 13 on which the antenna 30 is formed, and a waveguide block 11 attached to the printed circuit board 13. The antenna device 10 includes a transmission path 20 formed on the waveguide block 11 and the printed circuit board 13, and an antenna 30 formed on the printed circuit board 13. The transmission line 20 of the embodiment includes a first waveguide 40, a transformer waveguide 51, a slit 55, a second waveguide 60, a converter 70, and a microstrip line 80.

  As shown in FIG. 2, the printed circuit board 13 includes a first conductor pattern 15, a second conductor pattern 17, and a dielectric base material 19. The first conductor pattern 15 is provided on one surface side (upper side in FIG. 2) of the dielectric base material 19. The second conductor pattern 17 is provided on the surface of the dielectric substrate 19 opposite to the first conductor pattern 15 (lower side in FIG. 2). The second conductor pattern 17 is a ground plane.

  As shown in FIG. 4, the second conductor pattern 17 is formed on the entire surface of the dielectric substrate 19 opposite to the first conductor pattern 15 (excluding the area of the slit 55). In the following description, the dielectric base material 19 is assumed to have, for example, a non-dielectric constant εr: 3.2, a dielectric loss tangent tan δ: 0.001, and a substrate thickness: 0.127 mm.

  As shown in FIG. 1, in the embodiment, the first conductor pattern 15 forms a pattern 65 forming the second waveguide 60, a pattern forming a converter (tapered portion) 70, and a microstrip line 80. And a pattern forming the antenna 30. As a result, the printed circuit board 13 of the embodiment integrally includes the second waveguide 60, the converter 70, the microstrip line 80, and the antenna 30.

  As shown in FIG. 2, the waveguide block 11 is attached to the printed circuit board 13 on the second conductor pattern 17 side. The waveguide block 11 includes therein an opening that functions as the first waveguide 40 and an opening that functions as the transformer waveguide 51.

  As the first waveguide 40, for example, a standard waveguide defined in a standard relating to a waveguide can be used. For example, the first waveguide 40 is a hollow rectangular waveguide with a model name WR-10 of EIA standard (inner diameter nominal dimension: 1.27 mm × 2.54 mm). The impedance of the first waveguide 40 is, for example, 368.2Ω. In FIG. 2, the waveguide direction of the first waveguide 40 (direction in which electromagnetic waves are transmitted) is the y direction (vertical direction in FIG. 2). In FIG. 2, the first waveguide 40 has a waveguide end at the upper end and a waveguide start end outside the drawing. As shown in FIG. 1, the printed circuit board 13 is provided parallel to the xz plane orthogonal to the y direction. That is, the waveguide direction of the first waveguide 40 intersects the plane direction of the printed circuit board 13, more specifically, is orthogonal.

  As shown in FIG. 6, the first waveguide 40 includes an E-plane that is a wide wall and is formed parallel to the xy plane. In addition, the first waveguide 40 includes an H-plane that is a narrow wall and is formed in parallel with the yz plane. The H plane is orthogonal to the E plane.

  The transformer waveguide 51 shown in FIG. 2 is formed so as to communicate with the opening forming the first waveguide 40 on one end side (upper end side in FIG. 2) of the first waveguide 40 in the waveguide direction which is the end of the waveguide. Has been done. The transformer waveguide 51 functions as the impedance adjusting unit 50. The impedance adjusting unit 50 matches the first waveguide 40 and the second waveguide 60. The impedance of the transformer waveguide 51 is set to an arbitrary value between the impedances of the first waveguide 40 and the second waveguide 60.

  The transformer waveguide 51 has a length of about λ / 4 in the waveguide direction (y direction). The transformer waveguide 51 is a hollow rectangular waveguide. The transformer waveguide 51 is narrower than the first waveguide 40 in the z direction so as to have an impedance smaller than that of the first waveguide 40. As shown in FIGS. 5 and 6, the transformer waveguide 51 has an E surface having the same width as the E surface of the first waveguide 40. Further, the transformer waveguide 51 has an H-plane that is narrower than the H-plane of the first waveguide 40. That is, the H surface of the transformer waveguide 51 has a smaller dimension in the z direction than the H surface of the first waveguide 40. Also in the transformer waveguide 51, the E plane is parallel to the xy plane, and the H plane is parallel to the yz plane.

  As shown in FIG. 7, the transformer waveguide 51 having a narrow H plane may be arranged in the z-direction width of the first waveguide 40 near the center in the z-direction. However, as shown in FIG. 2, the transformer waveguide 51 is preferably arranged such that one E surface is flush with one E surface of the first waveguide 40. The arrangement of the transformer waveguide 51 in FIG. 2 facilitates processing of the first waveguide 40 and the transformer waveguide 51.

  The waveguide end (upper end in FIG. 2) of the transformer waveguide 51 is connected to the second waveguide 60 formed on the printed board 13 via the slit 55 formed on the second conductor pattern 17 of the printed board 13. Has been done.

  As shown in FIG. 1, the second waveguide 60 is configured as a substrate integrated waveguide (SIW). The substrate integrated waveguide is a waveguide formed on a printed circuit board. In the substrate integrated waveguide, a post wall is formed by a plurality of vias 61 and 63. As shown in FIG. 1, since the first conductor pattern 15 constitutes the second waveguide 60, the first conductor pattern 15 has a rectangular second waveguide pattern 65 in a plan view. The vias 61 and 63 are formed in the second waveguide pattern 65 so as to penetrate the dielectric base material 19 in order to connect the first conductor pattern 15 and the second conductor pattern 17 serving as the ground surface. (See FIG. 3). The via may be called a through hole. Here, the term "via" is used as a concept including a through hole.

  In addition, in FIG. 1, the waveguide direction of the second waveguide 60 is the z direction (the horizontal direction in FIGS. 1 and 2). In FIG. 1, in the second waveguide 60, the slit 55 is the input end, and the front end 65A on the microstrip line 80 side is the second waveguide end (output end). That is, the second waveguide 60 extends in the z direction, which is the direction intersecting the E plane of the first waveguide 40. By extending the second waveguide 60 in a direction intersecting the E plane of the first waveguide 40, the second waveguide 60 can be formed on the same plane as the microstrip line 80.

  The vias 61 and 63 forming the post wall include the via 61 formed on the rear side in the waveguide direction and the vias 63 formed on both sides in the width direction (x direction) as viewed in the waveguide direction (z direction). . As shown in FIG. 1, the via 61 is provided along the side of the rear end 65D of the second waveguide pattern 65. The via 63 is provided along the side of the left end 65B and the side of the right end 65C of the second waveguide pattern 65.

  The second waveguide 60 is formed so that the width L2 in the x direction is 2.54 mm, which is the same as the width of the first waveguide 40 and the transformer waveguide 51. Further, since the thickness of the dielectric base material 19 is 0.127 mm, the second waveguide 60 is an SIW having an inner diameter of 0.127 mm × 2.54 mm. The impedance of the second waveguide 60 is, for example, 14.4Ω.

  As shown in FIG. 4, the above-mentioned slit 55 is provided within a range surrounded by a plurality of vias 61 and 63 forming the post wall. The slit 55 is formed so that its longitudinal direction coincides with the x direction. In addition, as shown in FIG. 5, the slit 55 is formed so as to be located in the range of the opening of the transformer waveguide 51.

  Here, FIG. 8 shows a modification of the transmission line structure shown in FIGS. In the second waveguide 60 shown in FIG. 8, the via 61 does not form the post wall on the pattern rear end 65D side, but the conductor film 101 formed on the side surface of the rear end of the dielectric substrate 19. Constitutes the post wall. The circuit of the transmission line structure of FIG. 8 and the circuit of the transmission line structure of FIG. 2 are equivalent. In this case, a slit 55 that connects the transformer waveguide 51 and the second waveguide 60 is formed near the conductor film 101.

  Further, FIG. 9 shows a transmission line structure in which a via 61 is formed at the position of the conductor film 101 shown in FIG. FIG. 9 also shows a circuit structure equivalent to that of FIGS. The via 61 of FIG. 9 is formed closer to the slit 55 than the via 61 of FIG. When the structure of FIG. 9 and the structure of FIG. 2 are compared, the manufacturing of FIG. 2 is easier. That is, in FIG. 9, the via 61 and the slit 55 are very close to each other. Since the via 61 and the slit 55 are portions where the second conductor pattern 17 needs to be processed, the processing becomes difficult when the via 61 and the slit 55 are close to each other.

  On the other hand, as shown in FIG. 2, when the via 61 is separated by about λg / 2 (where λg is the wavelength in the substrate integrated waveguide), the via 61 and the slit 55 are equivalent to the structure of FIG. Since the distance L1 can be increased, processing becomes easy. Note that the distance between the via 61 and the slit 55 may be (λg / 2) × N (N is an integer of 1 or more), but the smaller N is advantageous in ensuring wide band performance.

  Further, as shown in FIG. 8, the slit 55 should be close to the rear end surface (the left side surface in FIG. 8) of the transformer waveguide 51. However, in this case, the slit 55 needs to be located inside the opening of the transformer waveguide 51 while being located around the opening of the transformer waveguide 51, which requires high assembly accuracy. That is, when the slit 55 is located outside the opening of the transformer waveguide 51 due to an assembly error between the printed circuit board 13 and the waveguide block 11, the characteristics are significantly deteriorated. In order to allow a relatively large assembly error, the slit 55 is preferably located near the center in the width direction of the opening of the transformer waveguide 51, as shown in FIGS. 2 and 5.

  As shown in FIG. 1, FIG. 3 and FIG. 4, in the embodiment, as the impedance adjusting section 50, in addition to the above-mentioned transformer waveguide 51, a via (formed in the second waveguide 60 (printed circuit board 13) ( An impedance adjusting via) 53 is provided. The via 53 allows a greater adjustment of impedance. The via 53 is provided within a range surrounded by the plurality of vias 61 and 63 forming the post wall. In the embodiment, the via 53 is provided between the slit 55 and the second waveguide terminal end 65A. The via 53 is formed so as to penetrate through the dielectric base material 19 in order to connect the first conductor pattern 15 and the second conductor pattern 17 serving as the ground surface.

  In the embodiment, the via 53 is provided near the slit 55 to facilitate impedance adjustment. The impedance adjusting element in the via 53 is, for example, the diameter of the via 53 or the distance between the via 53 and the slit 55. The number of the vias 53 may be one, but if the number is two or more as shown in the figure, impedance adjustment becomes easy. That is, when the plurality of vias 53 are provided, the spacing between the plurality of vias 53 can also be used as the impedance adjusting element. The direction in which the plurality of vias 53 are arranged is preferably parallel to the longitudinal direction (x direction) of the slit 55.

  As shown in FIG. 1, the first conductor pattern 15 includes a pattern forming a converter 70 formed at the front end 65A of the second waveguide pattern 65. The pattern forming the converter 70 is tapered. The converter 70 performs mode conversion between the second waveguide 60 and the microstrip line 80.

  The first conductor pattern 15 has a pattern that forms the microstrip line 80 continuously with the pattern that forms the converter 70. The impedance of the micro stop line is, for example, 67Ω. The microstrip line 80 is connected to the antenna 30 formed on the printed board 13. The antenna 30 is, for example, a patch antenna and is fed by the microstrip line 80.

  Since the second waveguide 60 and the microstrip line 80 are both provided on the printed circuit board 13, the converter 70 having a tapered pattern formed on the printed circuit board 13 does not ensure wide bandwidth of the converter 70. It's easy.

  When mode conversion is performed between the hollow waveguide such as the first waveguide 40 and the microstrip line 80 formed on the printed circuit board 13, since the impedance of the hollow waveguide is large, widening of the band is not possible. It's not easy. As a result, another component such as a back short described in Non-Patent Document 1 is required for widening the band. On the other hand, in the present embodiment, the first waveguide 40, which is a hollow rectangular waveguide, is converted to the second waveguide 60 that is thin and has low impedance like the microstrip line 80 via the transformer waveguide 51. Has been done. As a result, the converter 70 only needs to perform mode conversion between the thin second waveguide 60 and the microstrip line 80, so that it is easy to secure a wide band property in the converter 70. Therefore, the converter 70 of the second waveguide-microstrip line 80 may be a tapered pattern formed on the printed circuit board 13.

  On the other hand, the transmission line 20 of the present embodiment has a first waveguide 40 that is a hollow waveguide and a second waveguide 60 that is formed on the printed circuit board 13. Therefore, the impedance adjusting unit 50 is required to match the first waveguide 40 and the second waveguide 60. Moreover, the impedance of the first waveguide 40, which is a hollow waveguide, is relatively large (for example, 368.2Ω), whereas the impedance of the thin second waveguide 60, which is formed on the printed circuit board 13, is relatively large. Small (eg, 14.4Ω).

  The impedance of the second waveguide 60 is preferably small in view of the relationship with the microstrip line 80. From this viewpoint, the impedance of the second waveguide 60 is, for example, 1 / 1.2 or less of the impedance of the first waveguide 40. When the impedance of the second waveguide 60 becomes 1 / 1.2 or less of the impedance of the first waveguide 40, the impedance adjusting unit 50 such as the transformer waveguide 51 is often needed. The impedance of the second waveguide 60 may be 1 / 1.3 or less, 1/2 or less, or 1/5 or less of the impedance of the first waveguide 40, and 1 It may be / 10 or less.

  If the impedance of the second waveguide 60 is too small, matching will be difficult even if the impedance adjusting section 50 is provided, so it is preferable not to be too small. From this viewpoint, the impedance of the second waveguide 60 is, for example, 1/45 or more of the impedance of the first waveguide 40. The impedance of the second waveguide 60 may be 1/30 or more, or 1/20 or more of the impedance of the first waveguide 40.

  As described above, even if the impedance ratio between the first waveguide 40 and the second waveguide 60 is large, the impedance adjusting unit 50 according to the present embodiment allows the first waveguide 40 and the second waveguide 60 to be separated. Alignment is ensured. Moreover, since the impedance adjusting unit 50 has not only the transformer waveguide 51 but also the via 53, it is possible to cope with a large impedance ratio.

  As an example of the impedance ratio, the impedance of the second waveguide 60 can be, for example, 1/45 or more and 1 / 1.3 or less of the impedance of the first waveguide 40. In this case, it is possible to adjust to VSWR <1.3 in the ± 2 GHz band of the frequency 76.5 GHz band, and the wide band property can be easily ensured.

  As another example of the impedance ratio, the impedance of the second waveguide 60 may be, for example, 1/20 or more of the impedance of the first waveguide 40 and 1 / 1.2 or less. In this case, it is possible to adjust to VSWR <1.2 in the ± 2 GHz band of the frequency 76.5 GHz band, and it is possible to easily secure the wide band property.

[2.2 Second Embodiment]

  FIG. 10 shows an antenna device having a transmission line structure according to the second embodiment. The second embodiment differs from the first embodiment in the size of the second waveguide pattern 65. In the second embodiment, the second waveguide pattern 65 is formed in such a size that its left end 65B, right end 65C, and rear end 65D reach the peripheral edge of the printed circuit board 13. That is, the distance from the via 63 forming the post wall to the pattern left end 65B is L12 in the first embodiment (FIG. 1), while it is L22 in the second embodiment (FIG. 10), and L12 <L22. Is. Further, the distance from the via 63 forming the post wall to the pattern right end 65C is L13 in the first embodiment (FIG. 1), while it is L23 in the second embodiment (FIG. 10), and L13 <L23. Is. Further, the distance from the via 61 forming the post wall to the pattern rear end 65D is L14 in the first embodiment (FIG. 1), while it is L24 in the second embodiment (FIG. 10), and L14 < It is L24.

  As in the second embodiment shown in FIG. 10, even if the first conductor pattern 15 is larger than the size required for the second waveguide 60, the same characteristics as in the first embodiment can be obtained.

  In the via 63, the lengths L11 and L21 from the center of the via (output end via) 63 closest to the output end (pattern end) 65A of the second waveguide 60 to the pattern end 65A are the same as in the first embodiment. The second embodiment is the same. L11 and L21 are 0.3 mm, for example. Here, the lengths L11 and L21 from the center of the output end via 63 to the pattern end 65A are 0.1 λg or less (λg is the wavelength in the front substrate integrated waveguide). By setting the thickness to 0.1 λg or less, it is possible to prevent the electromagnetic wave from leaking from inside the second waveguide 60 to outside the second waveguide 60 between the output end via 63 and the pattern end 65A.

  In addition, in the second embodiment, vias 67 are additionally provided along the pattern ends 65A in order to prevent electromagnetic waves from entering from the pattern ends 65A, corresponding to the increase in L22 and L23. . The via 67 may be omitted.

  The second embodiment is the same as the first embodiment in that the description is omitted.

[2.3 Third Embodiment]

  FIG. 11 shows an antenna device having a transmission line structure according to the third embodiment. The third embodiment differs from the first embodiment in that the size of the second waveguide pattern 65 is different and the stub 110 formed in the second waveguide pattern 65 is present.

  The second waveguide pattern 65 of the third embodiment is formed larger than the second waveguide pattern 65 of the first embodiment. That is, L31 in FIG. 11 is longer than L11 in FIG. 1, L32 in FIG. 11 is longer than L12 in FIG. 1, and L3 in FIG. 11 is longer than L13 in FIG. By forming the second waveguide pattern 65 large, the length from the via 63 to the pattern ends 65A, 65B, 65C of the second waveguide pattern 65 can be increased, which facilitates the manufacture of the second waveguide pattern 65. .

  In the third embodiment, unlike the second embodiment, the length L31 from the center of the output end via 63 closest to the second waveguide pattern end 65A of the via 63 to the pattern end 65A is 0.1λg ( λg is set to 0.65 mm, which is larger than the wavelength in the front substrate integrated waveguide). For this reason, there is a risk of a leakage path of electromagnetic waves from the inside of the second waveguide 60 to the outside of the second waveguide 60 between the output end via 63 and the pattern end 65A.

  Therefore, in the third embodiment, a structure for preventing a leakage path from the output end via 63 to the pattern end 65A is adopted. In this structure, the actual via 63 is not provided between the output end via 63 and the pattern end 65A, but the virtual via 63A is arranged between the output end via 63 and the pattern end 65A. This structure has a stub 110 formed on the second waveguide pattern 65. In the third embodiment, the stub 110 is configured as an open stub. The open stub 110 has a line length of λg / 4. The open stub 110 has an open front end and a short base. In addition, a short circuit occurs at a position λg / 2 away from the base short circuit position.

  Therefore, at the pattern ends (pattern ends 65B and 65C in FIG. 8) of the second waveguide pattern 65, positions λg / 2 apart from the position where the virtual via 63A is desired to be arranged (between the output end via 63 and the pattern end 65A). In addition, by forming the root of the open stub 110, the position where the virtual via 63A is desired to be placed becomes a short circuit. The shorts can form post walls similar to vias 63. Although the stub 110 is formed in a bent shape in FIG. 11, it may be formed in a linear shape. When the stub is formed in a bent shape, it is possible to prevent the printed board 13 from increasing in size. A short stub may be used as the stub 110.

[2.4 Simulation results]

  12 and 13 show the simulation results of the reflection characteristics of the transmission line structure of the first embodiment. 12 shows a polar chart of reflection characteristics, and FIG. 13 shows VSWR (voltage standing wave ratio). In the simulation, the diameter of the vias 61 and 63 was 0.2 mm, and the interval (center interval) between the vias 61 and 63 was 0.7 mm. Further, L11, L12, L13, and L14 shown in FIG. 1 were each set to 0.3 mm so as to be about 0.1 λg.

  As shown in FIG. 13, the range in which VSWR is 1.2 or less is in the range of 73.48 GHz to 82.28 GHz (the range of 8.8 GHz), and it can be seen that wide bandwidth can be secured.

  14 to 16 show simulation results of reflection characteristics and passage characteristics of the transmission line structure according to the third embodiment. 14 to 16, FIGS. 14A, 15A and 16A show simulation results when the stub 110 is omitted from the third embodiment, and FIGS. 14B, 15B and 16B show simulation results of the third embodiment. There is. In the simulation, the diameter of the vias 61 and 63 was 0.3 mm, and the distance between the vias 61 and 63 was 0.8 mm. Further, L31, L32, and L33 shown in FIG. 11 were set to 0.65 mm, respectively. 0.65 mm is larger than 0.1 λg.

  Polar chart of reflection characteristics (FIGS. 14A and 14B), VSWR of reflection characteristics (FIGS. 15A and 15B), and passage characteristics (FIGS. 16A and 16B) where stub 110 is omitted (FIGS. 14A, 15A, 16A) Rather, the characteristics are improved when the stub is provided (FIGS. 14B, 15B, 16B).

[3. Note]

  It should be considered that the embodiments disclosed this time are exemplifications in all points and not restrictive. The scope of the present invention is shown not by the above meaning but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

10: antenna device 11: waveguide block 13: printed circuit board 15: first conductor pattern 17: second conductor pattern 19: dielectric base material 20: transmission line 30: antenna 40: first waveguide 50: impedance adjustment Part 51: Transformer waveguide 53: Via 55: Slit 60: Second waveguide 61: Via 63: Via 63A: Virtual via 65: Second waveguide pattern 65A: Front end 65B: Left end 65C: Right end 65D: Rear end 67: Via 70: Transducer 80: Microstrip line 101: Conductor film 110: Open stub

Claims (12)

A first waveguide,
An impedance adjusting unit that is provided on one end side of the first waveguide in the waveguide direction and includes a transformer waveguide that has an H-plane that is narrower than the H-plane of the first waveguide;
A second waveguide connected to the transformer waveguide via a slit, having a lower impedance than the first waveguide, and extending in a direction intersecting the E plane of the first waveguide;
A transmission line structure including. A microstrip line formed on a printed circuit board,
A converter of the second waveguide and the microstrip line formed on the printed circuit board;
Further equipped with,
The transmission line structure according to claim 1, wherein the second waveguide is formed on the printed circuit board. The transmission line structure according to claim 2, further comprising an antenna formed on the printed circuit board and fed by the microstrip line. The said 2nd waveguide is a board | substrate integrated waveguide which comprised the post wall by the several via | veer which connects the 1st conductor pattern and the 2nd conductor pattern used as a ground surface. The transmission line structure according to item. The transmission line according to claim 4, wherein the impedance adjustment unit includes one or a plurality of impedance adjustment vias provided in a range surrounded by the plurality of vias forming the post wall in the substrate integrated waveguide. Construction. The first conductor pattern has a pattern end serving as an output end of the substrate integrated waveguide,
Of the plurality of vias forming the post wall, the length from the center of the output end via closest to the pattern end to the pattern end is 0.1λg (λg is a wavelength in the substrate integrated waveguide) or less. The transmission line structure according to claim 4 or 5. The first conductor pattern is
A pattern end serving as an output end of the substrate integrated waveguide,
An output end via closest to the pattern end among the plurality of vias forming the post wall, and a stub for shorting the pattern end.
The transmission line structure according to claim 4 or 5. The transmission line structure according to claim 7, wherein the stub is an open stub formed at a position that short-circuits the output end via and the pattern end. The transmission line structure according to claim 7, wherein a length from a center of the output end via to the pattern end is larger than 0.1λg (λg is a wavelength in the substrate integrated waveguide). 10. The impedance of the second waveguide is 1/45 or more of the impedance of the first waveguide and is 1 / 1.2 or less of the impedance of the first waveguide. The transmission line structure according to item 1. The transmission line structure according to claim 10, wherein the impedance of the second waveguide is 1/20 or more of the impedance of the first waveguide. The transmission line structure according to claim 10 or 11, wherein the impedance of the second waveguide is 1 / 1.3 or less of the impedance of the first waveguide.

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