Horizontally polarized high-gain omnidirectional antenna

Abstract

This invention discloses a horizontally polarized high-gain omnidirectional antenna, relating to the field of communication antenna technology. The omnidirectional antenna includes a feeding structure and an antenna radiating structure. The antenna radiating structure includes a first substrate, with a top metal layer formed on the upper surface and a back metal layer formed on the lower surface. A plurality of vertically arranged metallized vias are formed along the rear, left, and right sides of the first substrate. The first substrate and the three-sided metallized vias combine to form a dielectric integrated waveguide. The lower end of the feed source is connected to the feeding structure, and the upper end of the feed source passes sequentially through the back metal layer, the first substrate, and the top metal layer before extending out from the top metal layer. A plurality of phase-conversion structures are respectively arranged on the antenna radiating structure on both sides of the feed source. The omnidirectional antenna has the advantages of simple structure and high radiation efficiency.

Description

Technical Field

[0001] This invention relates to the field of antenna technology for communication, and in particular to a simple-structured horizontally polarized high-gain omnidirectional antenna. Background Technology

[0002] Omnidirectional antennas have a large radiation range and are therefore widely used in various communication systems, such as indoor wireless local area networks, outdoor television broadcasting, and point-to-point communication systems. Compared to the complex and expensive phased array antennas, omnidirectional antennas have outstanding advantages: simple structure, low cost, and the ability to meet communication needs in most situations. Since their inception, many novel and high-performance omnidirectional high-gain antennas have been developed to meet different requirements. Omnidirectional high-gain antennas can be broadly divided into two categories: one is designed using pattern synthesis analysis methods in the form of omnidirectional high-gain array antennas; the other is omnidirectional high-gain antennas implemented using electrically large dimensions, increasing the aperture or adding lenses to improve the antenna gain. Summary of the Invention

[0003] The technical problem to be solved by the present invention is how to provide a horizontally polarized high-gain omnidirectional antenna with simple structure and high radiation efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a horizontally polarized high-gain omnidirectional antenna, characterized in that it includes a feeding structure and an antenna radiating structure. The antenna radiating structure includes a first substrate, a top metal layer formed on the upper surface of the first substrate, a bottom metal layer formed on the lower surface of the first substrate, and a plurality of vertically arranged metallized vias formed along the rear side, left side, and right side of the first substrate. The upper end of the metallized via is connected to the top metal layer and its upper end face is exposed from the upper surface of the top metal layer. The lower end of the metallized via is connected to the bottom metal layer and its lower end face is exposed from the lower surface of the bottom metal layer. The first substrate, the top metal layer, the bottom metal layer, and the three-sided metallized vias are combined to form a dielectric integrated waveguide. The lower end of the feed source is connected to the feeding structure, and the upper end of the feed source passes through the bottom metal layer, the first substrate, and the top metal layer in sequence and extends out from the top metal layer. A plurality of phase conversion structures are respectively arranged on the antenna radiating structure on both sides of the feed source.

[0005] A further technical solution is that each phase transition structure includes a curved groove located on the top metal layer, the front end of the curved groove extends to the front side of the first substrate, the rear end of the curved groove extends to the metallized via on the rear side of the first substrate, a plurality of periodic peaks and troughs are formed on the curved groove, and a short-circuit metallized via is provided in each peak and trough, the upper end of the short-circuit metallized via is connected to the top metal layer, and the lower end of the short-circuit metallized via is connected to the bottom metal layer.

[0006] A further technical solution is that the feeding structure is located on the left or right side of the antenna radiation structure. The feeding structure includes a second substrate, the upper surface of the second substrate is in contact with the bottom metal layer, and a transmission line extending along its length is formed on the lower surface of the second substrate. One end of the transmission line is connected to a connector, and the other end of the transmission line is connected to a feed source located in the middle of the first substrate.

[0007] A further technical solution is that the transmission line includes a first transmission segment, a second transmission segment, and a third transmission segment, which are connected sequentially. The width of the first transmission segment is the same as that of the third transmission segment and is greater than that of the second transmission segment. An outwardly extending portion is formed in the middle of the second transmission segment, and the width of the extension portion is greater than that of the first transmission segment.

[0008] A further technical solution is that: the feeding structure is located in the middle of the antenna radiation structure, the feeding structure includes a second substrate, the upper surface of the second substrate is in contact with the bottom metal layer, a transmission line extending along its length is formed on the lower surface of the second substrate, the middle part of the transmission line is connected to a connector, and the two ends of the transmission line are connected to feed sources located on both sides of the first substrate.

[0009] A further technical solution is that: the transmission line includes a fourth transmission segment and a fifth transmission segment, the fourth transmission segment is perpendicular to the fifth transmission segment, and a symmetrical transmission line structure is connected to each end of the fifth transmission segment. The transmission line structure includes a sixth transmission segment, a seventh transmission segment, an eighth transmission segment, and a ninth transmission segment connected in sequence. The width of the sixth transmission segment is greater than the width of the fifth transmission segment and less than the width of the seventh transmission segment. The width of the seventh transmission segment is equal to the width of the ninth transmission segment. The width of the eighth transmission segment is less than the width of the fifth transmission segment.

[0010] The beneficial effects of adopting the above technical solution are as follows: This application provides several vertical metallized vias along the rear side, left side and right side of the first substrate. The first substrate and the three-sided metallized vias are combined to form a dielectric integrated waveguide (SIW), so that one side of the first substrate forms an opening. Each half wavelength along the transmission direction is a radiation unit, which can be equivalent to a magnetic dipole (MD). A phase conversion structure is placed at a position every half wavelength from the feed point to rotate the electric field opposite to the target electric field direction by 180 degrees to the desired electric field direction.

[0011] The addition of a phase-conversion structure effectively rotates the target electric field direction by 180 degrees, improving the radiation pattern. The advantage of this structure is that it can be seamlessly embedded in the open waveguide (first dielectric layer), converting the phase of the target electric field to the desired state without sealing any part of the radiation aperture, thus achieving high radiation efficiency. Attached Figure Description

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0013] Figure 1 This is a schematic diagram of the antenna structure described in Embodiment 1 of the present invention;

[0014] Figure 2 This is a top view of the antenna structure described in Embodiment 1 of the present invention;

[0015] Figure 3 This is a schematic diagram of the main view structure of the antenna described in Embodiment 1 of the present invention;

[0016] Figure 4 This is a bottom-view structural diagram of the antenna described in Embodiment 1 of the present invention;

[0017] Figure 5 This is an exploded structural diagram of the antenna described in Embodiment 1 of the present invention;

[0018] Figure 6a This is a three-dimensional structural diagram of the antenna described in Embodiment 1 of the present invention;

[0019] Figure 6b yes Figure 6a Enlarged structural diagram at point A:

[0020] Figure 7 This is a three-dimensional structural diagram of the antenna described in Embodiment 1 of the present invention;

[0021] Figure 8a This is a cross-sectional view of the antenna described in Embodiment 1 of the present invention.

[0022] Figure 8b yes Figure 8aEnlarged structural diagram at point B:

[0023] Figure 8c yes Figure 8a Enlarged structural diagram at point C:

[0024] Figure 8d yes Figure 8a Enlarged structural diagram at point D:

[0025] Figure 9 This is a schematic diagram of the transmission line structure in the antenna described in Embodiment 1 of the present invention;

[0026] Figure 10 This is a partial structural diagram of the connector in the antenna described in Embodiment 1 of the present invention;

[0027] Figure 11 This is a schematic diagram of the antenna structure described in Embodiment 2 of the present invention;

[0028] Figure 12 This is a top view of the antenna structure described in Embodiment 2 of the present invention;

[0029] Figure 13 This is a schematic diagram of the main view structure of the antenna described in Embodiment 2 of the present invention;

[0030] Figure 14 This is a bottom-view structural diagram of the antenna described in Embodiment 2 of the present invention;

[0031] Figure 15 This is an exploded structural diagram of the antenna described in Embodiment 2 of the present invention;

[0032] Figure 16a This is a three-dimensional structural diagram of the antenna described in Embodiment 2 of the present invention;

[0033] Figure 16b yes Figure 16a Enlarged structural diagram at point A:

[0034] Figure 17 This is a three-dimensional structural diagram of the antenna described in Embodiment 2 of the present invention;

[0035] Figure 18a This is a cross-sectional view of the antenna described in Embodiment 2 of the present invention.

[0036] Figure 18b yes Figure 18a Enlarged structural diagram at point B:

[0037] Figure 18c yes Figure 18a Enlarged structural diagram at point C:

[0038] Figure 18d yes Figure 18aEnlarged structural diagram at point D:

[0039] Figure 19 This is a schematic diagram of the transmission line structure in the antenna described in Embodiment 2 of the present invention;

[0040] Figure 20 This is a partial structural diagram of the connector in the antenna described in Embodiment 2 of the present invention;

[0041] Figure 21a This is the radiation pattern after adding a phase conversion structure in an embodiment of the present invention;

[0042] Figure 21b It is a radiation pattern without a phase-transformation structure.

[0043] The components are: 1. Top metal layer; 2. Metallized via; 3. Short-circuit metallized via; 4. First substrate; 5. Bottom metal layer; 6. Second substrate; 7. Feed source; 8. Transmission line; 801. First transmission segment; 802. Second transmission segment; 803. Third transmission segment; 804. Fourth transmission segment; 805. Fifth transmission segment; 806. Sixth transmission segment; 807. Seventh transmission segment; 808. Eighth transmission segment; 809. Ninth transmission segment; 9. Connector; 901. Center post; 902. Connector head; 10. Bending groove; Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Example

[0046] like Figures 1-10As shown, this embodiment of the invention discloses a horizontally polarized high-gain omnidirectional antenna, including a feeding structure and an antenna radiating structure. The antenna radiating structure includes a first substrate 4, with a top metal layer 1 formed on the upper surface of the first substrate 4 and a bottom metal layer 5 formed on the lower surface of the first substrate 4. The top metal layer 1 and the bottom metal layer 5 are made of the same material, preferably copper. A plurality of vertically arranged metallized vias 2 are formed along the rear side, left side, and right side of the first substrate 4. The metallized vias 2 can be fabricated using materials available in the prior art. The upper end of the metallized via 2 is connected to the top metal layer 1, and its upper end face is exposed from the upper surface of the top metal layer 1 (that is, its upper end is not covered). The lower end of the metallized via 2 is connected to the bottom metal layer 5, and its lower end face is exposed from the lower surface of the bottom metal layer 5 (that is, its lower end is not covered). The first substrate 4, the top metal layer 1, the bottom metal layer 5, and the three-sided metallized vias 2 together constitute a dielectric integrated waveguide (SIW). The lower end of the feed source 7 is connected to the feeding structure, and the upper end of the feed source 7 passes through the bottom metal layer 5, the first substrate 4, and the top metal layer 1 in sequence before extending out from the top metal layer 1 (the feed source can be a feed source in the prior art, and the upper end of the feed source 7 is higher than the height of the top metal layer 1). Several phase conversion structures are respectively arranged on the antenna radiation structure on both sides of the feed source 7. Furthermore, the distance between the phase conversion structure adjacent to the feed source 7 and the feed source is 1 / 2 wavelength (the wavelength corresponding to the center frequency), and the distance between the phase conversion structures at other positions is also 1 / 2 wavelength.

[0047] like Figure 1 , Figure 2 , Figure 5 , Figures 6a-6b As shown, each phase transition structure includes a curved groove 10 located on the top metal layer 1, with the front end of the curved groove 10 extending to the front side of the first substrate 4. The rear end of the curved groove 10 extends to a metallized via 2 on the rear side of the first substrate 4. The curved groove 10 has a plurality of periodic peaks and troughs, and each peak and trough contains a short-circuit metallized via 3. The upper end of the short-circuit metallized via 3 is connected to the top metal layer 1, and the lower end of the short-circuit metallized via 3 is connected to the bottom metal layer 5. Preferably, the curved groove 10 is a periodic rectangular wave, with a metallized via 3 in each peak and trough of the rectangular wave.

[0048] Further, such as Figure 1 , Figure 3 , Figure 4 , Figure 5 , Figure 7 as well as Figure 8aAs shown, the feeding structure is located on the left (or right) side of the antenna radiation structure. The feeding structure includes a second substrate 6. The upper surface of the second substrate 6 is in contact with the bottom metal layer 5. A transmission line 8 extending along its length is formed on the lower surface of the second substrate 6. One end of the transmission line 8 is connected to a connector 9, and the other end of the transmission line 8 is connected to a feed source 7 located in the middle of the first substrate 4.

[0049] Further, such as Figure 1 , Figure 3 , Figure 4 , Figure 5 , Figure 7 as well as Figure 8a As shown, preferably, in this application, the second substrate 6 is located to the left of the first substrate 4, the connector 9 is located at the left end of the second substrate 6, and the right end of the second substrate 6 extends to the middle of the first substrate 4. The first substrate 4 and the second substrate 6 can be made of the same or different materials.

[0050] Further, such as Figure 9 As shown, the transmission line 8 is made of copper and includes a first transmission segment 801, a second transmission segment 802, and a third transmission segment 803. The first transmission segment 801, the second transmission segment 802, and the third transmission segment 803 are connected sequentially. The first transmission segment 801 and the third transmission segment 803 have the same width, but the width is greater than that of the second transmission segment 802. An outwardly extending portion is formed in the middle of the second transmission segment 802, and the width of the extension portion is greater than the width of the first transmission segment 801. It should be noted that the transmission line 8 can also be in other forms. Example

[0051] like Figures 11-20As shown, this embodiment of the invention discloses a horizontally polarized high-gain omnidirectional antenna, including a feeding structure and an antenna radiating structure. The antenna radiating structure includes a first substrate 4, with a top metal layer 1 formed on the upper surface of the first substrate 4 and a bottom metal layer 5 formed on the lower surface of the first substrate 4. The top metal layer 1 and the bottom metal layer 5 are made of the same material, preferably copper. A plurality of vertically arranged metallized vias 2 are formed along the rear side, left side, and right side of the first substrate 4. The metallized vias 2 can be fabricated using materials available in the prior art. The upper end of the metallized via 2 is connected to the top metal layer 1, and its upper end face is exposed from the upper surface of the top metal layer 1 (that is, its upper end is not covered). The lower end of the metallized via 2 is connected to the bottom metal layer 5, and its lower end face is exposed from the lower surface of the bottom metal layer 5 (that is, its lower end is not covered). The first substrate 4, the top metal layer 1, the bottom metal layer 5, and the three-sided metallized vias 2 together constitute a dielectric integrated waveguide (SIW). The lower end of the feed source 7 is connected to the feeding structure, and the upper end of the feed source 7 passes through the bottom metal layer 5, the first substrate 4, and the top metal layer 1 in sequence before extending out from the top metal layer 1 (the feed source can be a feed source in the prior art, and the upper end of the feed source 7 is higher than the height of the top metal layer 1). Several phase conversion structures are respectively arranged on the antenna radiation structure on both sides of the feed source 7. Furthermore, the distance between the phase conversion structure adjacent to the feed source 7 and the feed source is 1 / 2 wavelength (the wavelength corresponding to the center frequency), and the distance between the phase conversion structures at other positions is also 1 / 2 wavelength.

[0052] like Figure 1 , Figure 2 , Figure 5 , Figures 6a-6b As shown, each phase transition structure includes a curved groove 10 located on the top metal layer 1, with the front end of the curved groove 10 extending to the front side of the first substrate 4. The rear end of the curved groove 10 extends to a metallized via 2 on the rear side of the first substrate 4. The curved groove 10 has a plurality of periodic peaks and troughs, and each peak and trough contains a short-circuit metallized via 3. The upper end of the short-circuit metallized via 3 is connected to the top metal layer 1, and the lower end of the short-circuit metallized via 3 is connected to the bottom metal layer 5. Preferably, the curved groove 10 is a periodic rectangular wave, with a metallized via 3 in each peak and trough of the rectangular wave.

[0053] Further, such as Figure 1 , Figure 3 , Figure 4 , Figure 5 , Figure 7 as well as Figure 8aAs shown, the embodiment of the present invention differs from the first embodiment in that: the feeding structure is located in the middle of the antenna radiation structure, the feeding structure includes a second substrate 6, the upper surface of the second substrate 6 is in contact with the bottom metal layer 5, the lower surface of the second substrate 6 has a transmission line 8 extending along its length direction, the middle part of the transmission line 8 is connected to a connector 9, and the two ends of the transmission line 8 are connected to feed sources 7 located on both sides of the first substrate 4.

[0054] Further, such as Figure 1 , Figure 3 , Figure 4 , Figure 5 , Figure 7 as well as Figure 8a As shown, the second substrate 6 is located in the middle of the first substrate 4, the connector 9 is located in the middle of the second substrate 6, the two ends of the second substrate 6 extend to the two sides of the first substrate 4, the transmission line 8 has a left-right symmetrical structure, and the two ends of the transmission line 8 are respectively connected to a feed source 7.

[0055] Further, such as Figure 9 As shown, the transmission line 8 is made of copper and includes a fourth transmission segment 804 and a fifth transmission segment 805, with the fourth transmission segment 804 perpendicular to the fifth transmission segment 805. A symmetrical transmission line structure is connected to each end of the fifth transmission segment 805. This transmission line structure includes a sixth transmission segment 806, a seventh transmission segment 807, an eighth transmission segment 808, and a ninth transmission segment 809 connected sequentially. The width of the sixth transmission segment 806 is greater than the width of the fifth transmission segment 805 but less than the width of the seventh transmission segment 807. The width of the seventh transmission segment 807 is equal to the width of the ninth transmission segment 809. The width of the eighth transmission segment 808 is less than the width of the fifth transmission segment 805. It should be noted that the transmission line 8 can also be in other forms.

[0056] like Figure 10 As shown, the connector is a connector in the prior art. The connector 9 includes a connector head 902, and a central post 901 is fixed at the center of the connector head 902. The central post 901 is connected to the transmission line 8.

[0057] An opening is made on the side of the rectangular waveguide (first substrate) to form a TE0.5,0 mode transmission state. The open portion of the rectangular waveguide has a radiating element at every half-wavelength along the transmission direction, which can be equivalent to a magnetic dipole (MD). A phase conversion structure is placed at every half-wavelength distance from the feed point (feed source) to rotate the electric field, which is opposite to the target electric field direction, by 180 degrees to the desired electric field direction. Figure 21 shows a schematic diagram with the added phase conversion structure. The phase conversion part is placed at a distance of 1 / 2 wavelength from the feed point. Without the phase conversion structure, there is an electric field component opposite to the main electric field direction, which affects the far-field radiation pattern. Therefore, a phase conversion structure is added to achieve the effect of rotating the electric field direction by 180 degrees.

[0058] Working principle of phase conversion structure:

[0059] The phase-switching structure comprises bent slots and metal vias etched into the metal surface (top metal layer). This structure can be equivalent to an LC circuit, with the bent slots acting as capacitors and the short-circuit vias as inductors. By adjusting the position and size of the bent slots and metal vias, the equivalent LC circuit functions as a bandpass filter, thus providing a 180-degree phase shift. The comparison of the radiated electric fields before and after the shift is shown below. Figure 21a and 21b As shown, the addition of the phase conversion structure effectively rotates the target electric field direction by 180 degrees, improving the radiation pattern. The advantage of this structure is that the phase conversion structure can be seamlessly embedded in the open waveguide, converting the phase of the target electric field to the desired state without sealing any part of the radiation aperture, thus achieving high radiation efficiency.

[0060] In the two antenna structures of this invention, the principles are completely the same, only the feed point position differs. It is determined based on the number of elements in the array and the corresponding electric field distribution (6 radiating elements in Embodiment 1, and 8 radiating elements in Embodiment 2). The basic principle is to convert the electric field direction distributed near the phase conversion structure to the desired direction (Note: the phase conversion structure can only convert the electric field in one direction). After determining the feed point position, the position of the SMA connector is also determined.

Claims

1. A horizontally polarized high-gain omnidirectional antenna, characterized in that: The device includes a feeding structure and an antenna radiating structure. The antenna radiating structure includes a first substrate (4), on the upper surface of which a top metal layer (1) is formed, and on the lower surface of which a bottom metal layer (5) is formed. A plurality of vertically arranged metallized vias (2) are formed along the rear, left, and right sides of the first substrate (4). The upper end of each metallized via (2) is connected to the top metal layer (1), and its upper end face is exposed from the upper surface of the top metal layer (1). The lower end of each metallized via (2) is connected to the top metal layer (1). The bottom metal layer (5) is connected and its lower end face is exposed from the lower surface of the bottom metal layer (5). The first substrate (4), the top metal layer (1), the bottom metal layer (5) and the three-sided metallized via (2) are combined to form a dielectric integrated waveguide. The lower end of the feed source (7) is connected to the feeding structure. The upper end of the feed source (7) passes through the bottom metal layer (5), the first substrate (4) and the top metal layer (1) in sequence and extends out from the top metal layer (1). Several phase conversion structures are respectively provided on the antenna radiation structures on both sides of the feed source (7). Each phase transition structure includes a curved groove (10) located on the top metal layer (1). The front end of the curved groove (10) extends to the front side of the first substrate (4), and the rear end of the curved groove (10) extends to the metallized via (2) on the rear side of the first substrate (4). A plurality of periodic peaks and valleys are formed on the curved groove (10). A short-circuit metallized via (3) is provided in each peak and valley. The upper end of the short-circuit metallized via (3) is connected to the top metal layer (1), and the lower end of the short-circuit metallized via (3) is connected to the bottom metal layer (5). The curved groove (10) is a periodic rectangular wave, and a metallized via (3) is provided in the crest and trough of the rectangular wave. The feeding structure is located on the left or right side of the antenna radiation structure. The feeding structure includes a second substrate (6). The upper surface of the second substrate (6) is in contact with the bottom metal layer (5). A transmission line (8) extending along its length is formed on the lower surface of the second substrate (6). One end of the transmission line (8) is connected to a connector (9), and the other end of the transmission line (8) is connected to a feed source (7) located in the middle of the first substrate (4). The feeding structure is located in the middle of the antenna radiation structure. The feeding structure includes a second substrate (6). The upper surface of the second substrate (6) is in contact with the bottom metal layer (5). A transmission line (8) extending along its length is formed on the lower surface of the second substrate (6). The middle part of the transmission line (8) is connected to a connector (9). The two ends of the transmission line (8) are connected to feed sources (7) located on both sides of the first substrate (4). The second substrate (6) is located in the middle of the first substrate (4), the connector (9) is located in the middle of the second substrate (6), the two ends of the second substrate (6) extend to the two sides of the first substrate (4), the transmission line (8) has a left-right symmetrical structure, and the two ends of the transmission line (8) are respectively connected to a feed source (7). The connector (9) includes a connector head (902), and a center post (901) is fixed at the center of the connector head (902). The center post (901) is connected to the transmission line (8). The transmission line (8) includes a fourth transmission segment (804) and a fifth transmission segment (805). The fourth transmission segment (804) is perpendicular to the fifth transmission segment (805). The two ends of the fifth transmission segment (805) are respectively connected to a symmetrical transmission line structure. The transmission line structure includes a sixth transmission segment (806), a seventh transmission segment (807), an eighth transmission segment (808), and a ninth transmission segment (809) connected in sequence. The width of the sixth transmission segment (806) is greater than the width of the fifth transmission segment (805) and less than the width of the seventh transmission segment (807). The width of the seventh transmission segment (807) is equal to the width of the ninth transmission segment (809). The width of the eighth transmission segment (808) is less than the width of the fifth transmission segment (805).

2. The horizontally polarized high-gain omnidirectional antenna as described in claim 1, characterized in that: The second substrate (6) is located to the left of the first substrate (4), the connector (9) is located at the left end of the second substrate (6), and the right end of the second substrate (6) extends to the middle of the first substrate (4).

3. The horizontally polarized high-gain omnidirectional antenna as described in claim 1, characterized in that: The transmission line (8) includes a first transmission segment (801), a second transmission segment (802), and a third transmission segment (803). The first transmission segment (801), the second transmission segment (802), and the third transmission segment (803) are connected in sequence. The width of the first transmission segment (801) and the third transmission segment (803) is the same and greater than the width of the second transmission segment (802). An outwardly extending extension is formed in the middle of the second transmission segment (802), and the width of the extension is greater than the width of the first transmission segment (801).

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