Hybrid coupler and method for producing hybrid coupler

Abstract

A hybrid coupler is disclosed. The hybrid coupler includes a printed circuit board having a first metallization layer and a second metallization layer disposed below the first metallization layer. The first metallization layer comprises at least two input ports and at least two output ports. The hybrid coupler also includes a plurality of couplers coupled adjacent to each other on the first metallization layer. Each coupler of the plurality of couplers includes a transmission trace electrically coupled with a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The hybrid coupler also includes a defected ground structure having a predefined shape, the defected ground structure defined in the second metallization layer below each coupling joint formed between the transmission traces of the plurality of couplers.

Description

[0001] Citation of priority application

[0002] This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 63 / 395,928, filed on August 8, 2022, the disclosure of which is hereby incorporated by reference herein. Technical Field

[0003] The present disclosure relates to communication systems, and in particular to hybrid couplers for dual beam antennas. Background Art

[0004] The information in this section merely provides background information related to the present disclosure and may not constitute prior art with the present disclosure.

[0005] Cellular communication systems are used to provide wireless communications to fixed and mobile users (referred to herein as "users"). A cellular communication system may include a plurality of base stations, each of which provides wireless cellular services for a designated coverage area, generally referred to as a "cell". Each base station may include one or more antennas for transmitting radio frequency ("RF") signals to and receiving RF signals from users within the cell served by the base station. Antennas are directional devices that can focus RF energy transmitted in specific directions (or received from these directions). The "gain" of an antenna in a given direction is a measure of the antenna's ability to focus RF energy in that specific direction. The "radiation pattern" of an antenna is a compilation of the antenna's gain in all different directions. The radiation pattern of an antenna is typically designed to serve a predefined coverage area, generally referred to as a "sector", such as a cell or a portion thereof. An antenna may be designed to have a maximum gain level throughout its predefined coverage area, and it is generally desirable for the antenna to have a much lower gain level outside the coverage area to reduce interference between sectors / cells.

[0006] Typically, these multiple sector antennas are configured on a tower, with the (multiple) radiation beams generated by each antenna directed outward to serve the corresponding cell. Dual-beam / Twin-beam antennas (or multi-beam antennas) can be used to increase the capacity of a base station. For example, a dual-beam antenna generates two separate antenna beams, each of which has a reduced size in the azimuth plane and each points to a different direction in the azimuth plane, thereby dividing the sector into two smaller sub-sectors. Many dual-beam / multi-beam antennas employ beamforming networks (BFNs) to generate multiple beams. The BFN may include a hybrid coupler, which is a passive device that couples a defined amount of RF signals input at one or more input ports to one or more output ports. A hybrid coupler is designed to equally or unequally split the power of an RF signal input at one or more of its input ports.

[0007] The known hybrid couplers used in dual beam antennas cannot meet the desired broadband requirements and consume high energy during operation. In addition, the known hybrid couplers may not promote equal power distribution. A known solution to overcome the technical problems includes integrating a "Xinger" integrated circuit (IC) into a hybrid coupler. However, integrating the Xinger IC into the coupler increases the manufacturing cost because the materials (i.e., copper) used in the Xinger IC and the design of the integrated coupler assembly are expensive. In addition, the Xinger IC can exhibit low power handling capacity. The Xinger IC is a Xinger semiconductor with a smaller size, so it has a low power handling capacity. If more power is applied, the Xinger chip is very likely to fail. Since the coupler can be used in different antennas, the power handling capacity of the coupler becomes a challenge. The antenna is able to handle the load when the input arrives at the antenna in an indirect manner (i.e., after a phase shift). However, when the input is directly provided to the antenna, it becomes a challenge for the antenna to handle a large amount of power / load.

[0008] Therefore, there is a need for an improved hybrid coupler that addresses at least the problems identified above and provides improved broadband operation, optimized power distribution, and reduced manufacturing costs. Summary of the invention

[0009] One or more disadvantages of the prior art are overcome by the claimed system, and additional advantages are provided by providing a system as claimed in the present disclosure. Additional features and advantages are achieved by the technology of the present disclosure. Other embodiments and aspects of the present disclosure are described in detail herein and are considered a part of the claimed disclosure.

[0010] According to an embodiment of the present disclosure, in one aspect, a hybrid coupler is disclosed. The hybrid coupler includes a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The hybrid coupler also includes a plurality of couplers coupled adjacent to each other on the first metallization layer. Each coupler of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The hybrid coupler also includes a defective ground structure having a predefined shape, the defective ground structure being defined in the second metallization layer below each coupling joint formed between the transmission traces of the plurality of couplers.

[0011] In another non-limiting embodiment of the present disclosure, the predefined shape of the defective grounding structure is a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangle dumbbell, a round dumbbell, a square dumbbell or a rectangular dumbbell.

[0012] In another non-limiting embodiment of the present disclosure, the hybrid coupler includes four coupler units on the first metallization layer.

[0013] In another non-limiting embodiment of the present disclosure, the defective ground structure is configured to increase the electrical length of the trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz.

[0014] In another non-limiting embodiment of the present disclosure, the electrical length of the traces extending between the transmission traces is 25 mm.

[0015] In another non-limiting embodiment of the present disclosure, the defective ground structure has a length of 9.40 mm and a width of 6.90 mm.

[0016] In another non-limiting embodiment of the present disclosure, the hybrid coupler is a 3dB 90-degree hybrid coupler.

[0017] The hybrid coupler of the present disclosure, wherein the defective ground structure is defined in a second metallization layer disposed below a first metallization layer having a plurality of couplers, eliminates the need to add (a plurality of) Xinger ICs in the coupler assembly and provides uniform power distribution in the hybrid coupler. In addition, the hybrid coupler of the present disclosure provides an improved operating broadband frequency, optimized power distribution, and reduced manufacturing cost compared to conventional hybrid couplers. Furthermore, the hybrid coupler of the present disclosure is embodied as a broadband 3-dB orthogonal coupler operable between 1.695-2.690 GHz, and provides technical advantages of high power, 0.2 dB insertion loss, better than 18 dB return loss, and better than 25 dB isolation in the frequency range of 1.695 to 2.69 GHz.

[0018] According to another aspect of the present disclosure, a method for manufacturing a hybrid coupler is disclosed. The method includes designing a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The method also includes arranging a plurality of couplers coupled adjacent to each other on the first metallization layer. Each of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The method also includes defining a defective ground structure having a predefined shape below each coupling joint formed between the transmission traces of the plurality of couplers in the second metallization layer.

[0019] In another non-limiting embodiment of the present disclosure, defining the defective grounding structure in the predefined shape includes defining a defective grounding structure in the shape of a rectangle, diamond, square, trumpet-shaped dumbbell, triangular dumbbell, circular dumbbell, square dumbbell or rectangular dumbbell.

[0020] According to another aspect of the present disclosure, a dual-beam antenna is disclosed. The dual-beam antenna includes a hybrid coupler, which is suitable for mounting a radiating element thereon. The hybrid coupler includes a printed circuit board, which has a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The hybrid coupler also includes a plurality of couplers coupled adjacent to each other on the first metallization layer. Each coupler of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The hybrid coupler also includes a defective ground structure having a predefined shape, which is defined in the second metallization layer and below each coupling joint formed between the transmission traces of the plurality of couplers.

[0021] In another non-limiting embodiment of the present disclosure, the predefined shape of the defective grounding structure is a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangle dumbbell, a round dumbbell, a square dumbbell or a rectangular dumbbell.

[0022] In another non-limiting embodiment of the present disclosure, the hybrid coupler includes four coupler units on the first metallization layer.

[0023] In another non-limiting embodiment of the present disclosure, the defective ground structure is configured to increase the electrical length of the trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz.

[0024] In another non-limiting embodiment of the present disclosure, the electrical length of the traces extending between the transmission traces is 25 mm.

[0025] In another non-limiting embodiment of the present disclosure, the defective ground structure has a length of 9.40 mm and a width of 6.90 mm.

[0026] In another non-limiting embodiment of the present disclosure, the hybrid coupler is a 3dB 90-degree hybrid coupler.

[0027] In another non-limiting embodiment of the present disclosure, the radiating elements are arranged in a staggered arrangement and are electrically coupled to the hybrid coupler.

[0028] In another non-limiting embodiment of the present disclosure, the staggered arrangement of the radiation elements includes a horizontal layout, a vertical layout, an offset layout, or a combination thereof of the radiation elements.

[0029] A dual-beam antenna including a hybrid coupler of the present disclosure (wherein a defective ground structure is defined in a second metallization layer disposed below a first metallization layer having a plurality of couplers) eliminates the need to add (multiple) Xinger ICs in the coupler assembly and provides equal power distribution in the hybrid coupler. In addition, compared to conventional known hybrid couplers, the dual-beam antenna of the present disclosure provides an improved operating broadband frequency, optimized power distribution, and reduced manufacturing cost. Furthermore, in the dual-beam antenna, the hybrid coupler of the present disclosure is embodied as a broadband 3-dB orthogonal coupler operable between 1.695-2.690 GHz, and provides technical advantages of high power, 0.2 dB insertion loss, better than 18 dB return loss, and better than 25 dB isolation in the frequency range of 1.695 to 2.69 GHz.

[0030] It should be understood that the aspects and embodiments of the present disclosure described above can be used in any combination with each other. Several aspects and embodiments can be combined together to form another embodiment of the present disclosure.

[0031] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The novel features and characteristics of the present disclosure are set forth in this specification. However, the disclosure itself, as well as the preferred mode of use, other objects and advantages thereof, will be best understood by reference to the following description of illustrative embodiments when read in conjunction with the accompanying drawings. One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, wherein like reference numerals represent like elements, and in the drawings:

[0033] Figure 1 is a perspective view of a hybrid coupler including a circuit board having a first metallization layer and a second metallization layer;

[0034] Figure 2 for Figure 1 A top view of a hybrid coupler showing a transmission trace formed on a first metallization layer;

[0035] Figure 3 for Figure 1 A side view of a hybrid coupler showing a first metallization layer and a second metallization layer;

[0036] Figure 4 for Figure 1 A bottom view of a hybrid coupler of FIG. 1 showing a defective ground structure in the second metallization layer;

[0037] Figure 5 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure having a rectangular shape;

[0038] Figure 6 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a diamond shape;

[0039] Figure 7 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a square dumbbell shape;

[0040] Figure 8 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a flared dumbbell shape;

[0041] Fig. 9 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a triangular dumbbell shape;

[0042] Fig.10 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a rectangular dumbbell shape;

[0043] Fig.11 for Figure 1 A top view of a hybrid coupler of claim 1, wherein a first metallization layer having a transmission trace is superimposed on a second metallization layer defining a defective ground structure in a circular dumbbell shape;

[0044] Fig.12 shows a staggered arrangement of radiating elements (of a dual beam antenna) that may be electrically coupled to a hybrid coupler according to an embodiment of the present disclosure; and

[0045] Fig.13 A staggered arrangement of radiating elements that may be electrically coupled to a hybrid coupler according to another embodiment of the present disclosure is shown.

[0046] Skilled technicians will recognize that the elements in the drawings are shown for simplicity and are not necessarily drawn to scale. For example, the sizes of some elements in the drawings may be enlarged relative to other elements to help improve understanding of the embodiments of the present disclosure. DETAILED DESCRIPTION

[0047] Although the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the accompanying drawings and will be described in detail below. However, it should be understood that this is not intended to limit the present disclosure to the specific forms disclosed, but rather, the present disclosure will cover all modifications, equivalents and alternatives falling within the scope of the present disclosure as defined by the appended claims.

[0048] Before describing the detailed embodiments, it can be observed that the novel and inventive steps according to the present disclosure are present in a hybrid coupler, a method for manufacturing a hybrid coupler, and a dual-beam antenna including a hybrid coupler. It should be noted that a person skilled in the art may be inspired by the present disclosure and modify the various structures of the hybrid coupler, the method, and the dual-beam antenna. However, such modifications should be interpreted within the scope of the present disclosure. Therefore, the accompanying drawings show only those specific details that are relevant to understanding the embodiments of the present disclosure, so as to avoid obscuring the present disclosure with details that are easily understood by a person of ordinary skill in the art who has the benefit of the description herein.

[0049] In this disclosure, the term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or implementation of the presently disclosed subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0050] The terms "comprise," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a device comprising a list of components includes not only those components, but may also include other components not expressly listed or inherent to such device. In other words, one or more elements in a system or device followed by "comprising..." does not exclude the presence of other or additional elements in the system or device without more constraints.

[0051] Terms such as "at least one" and "one or more" may be used interchangeably or in combination throughout the description.

[0052] According to an embodiment of the present disclosure, in one aspect, a hybrid coupler is disclosed. The hybrid coupler includes a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The hybrid coupler also includes a plurality of couplers coupled adjacent to each other on the first metallization layer. Each coupler of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The hybrid coupler further includes a defective ground structure having a predefined shape, the defective ground structure being defined in the second metallization layer below each coupling joint formed between the transmission traces of the plurality of couplers.

[0053] The predefined shape of the defective ground structure may be, for example, a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangle-shaped dumbbell, a circular dumbbell, a square dumbbell or a rectangular dumbbell. The hybrid coupler comprises four coupler units on the first metallization layer.

[0054] In an embodiment, the defective ground structure is configured to increase the electrical length of the trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz. The electrical length of the trace extending between the transmission traces is 25 mm. In addition, the defective ground structure has a length of 9.40 mm and a width of 6.90 mm. In some embodiments, the hybrid coupler is a 3 dB 90 degree hybrid coupler.

[0055] According to another aspect of the present disclosure, a method for manufacturing a hybrid coupler is disclosed. The method includes designing a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The method also includes arranging a plurality of couplers coupled adjacent to each other on the first metallization layer. Each of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The method also includes defining a defective ground structure having a predefined shape in the second metallization layer below each coupling joint formed between two adjacent couplers of the first metallization layer. In addition, defining a defective ground structure having a predefined shape may include defining a defective ground structure having a shape such as a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangular dumbbell, a circular dumbbell, a square dumbbell, or a rectangular dumbbell.

[0056] According to another aspect of the present disclosure, a dual-beam antenna is disclosed. The dual-beam antenna includes a hybrid coupler, which is suitable for mounting a radiating element thereon. The hybrid coupler includes a printed circuit board, which has a first metallization layer and a second metallization layer arranged below the first metallization layer. The first metallization layer includes at least two input ports and at least two output ports. The hybrid coupler also includes a plurality of couplers coupled adjacent to each other on the first metallization layer. Each coupler of the plurality of couplers includes a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extend between an input port and an output port of the first metallization layer. The hybrid coupler further includes a defective ground structure having a predefined shape, which is defined in the second metallization layer and below each coupling joint formed between the transmission traces of the plurality of couplers. The predefined shape of the defective ground structure may, for example, have a rectangular, diamond, square, flared dumbbell, triangular dumbbell, circular dumbbell, square dumbbell or rectangular dumbbell shape. The hybrid coupler includes four coupler units on the first metallization layer.

[0057] In an embodiment, the defective ground structure is configured to increase the electrical length of the trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz. The electrical length of the trace extending between the transmission traces is 25 mm. The defective ground structure has a length of 9.40 mm and a width of 6.90 mm. In addition, the hybrid coupler is a 3 dB 90 degree hybrid coupler.

[0058] In another embodiment, the radiating elements are arranged in a staggered arrangement and electrically coupled to the hybrid coupler. The staggered arrangement of the radiating elements includes a horizontal layout, a vertical layout, an offset layout, or a combination thereof of the radiating elements.

[0059] It should be understood that the aspects and embodiments of the present disclosure described above can be used in any combination with each other. Several aspects and embodiments can be combined together to form another embodiment of the present disclosure.

[0060] Reference will now be made to exemplary embodiments of the present disclosure as illustrated in the accompanying drawings. Wherever possible, the same numbers will be used to refer to the same or like parts.

[0061] Reference in the following paragraphs Figures 1 to 13 Describe the embodiments of the present disclosure. Figures 1 to 13 In the drawings, one or more identical elements having the same or similar functions are indicated by the same reference numerals.

[0062] Figure 1 A perspective view of a hybrid coupler (100) according to an embodiment of the present disclosure is shown. In addition, Figure 2 and Figure 3 1 and 2 show a top view and a side view of a hybrid coupler (100) of the present disclosure, respectively. The hybrid coupler (100) may be included in a beam forming network (BFN) of a dual beam antenna (10), for example. Figure 1 and 2 As shown in , the hybrid coupler (100) may include a printed circuit board (112). Within the scope of the present disclosure, at least two input coaxial cables (120) and two output coaxial cables (130) (or other RF transmission line structures) may be connected to the hybrid coupler (100) to carry radio frequency (RF) signals to and from the hybrid coupler (100).

[0063] like Figure 3 As shown in , the printed circuit board (112) may include a dielectric substrate (114) having a first or "top" metallization layer (116) on its top side and a second or "bottom" metallization layer (118) on its bottom side. The dielectric substrate (114) may be a low loss dielectric substrate having a suitable dielectric constant. In an exemplary embodiment, the dielectric substrate (114) may be a 30 mil ZYF300CA-C substrate. Those skilled in the art will appreciate that different types of dielectric substrates (114) may also be used in the present disclosure. The various components of the first and second metallization layers (116, 118) will be referenced in subsequent paragraphs. Figures 1 to 5 Further detailed discussion.

[0064] Figure 1 ,2 , 3 and 5 show in more detail various structures included in the first metallization layer (116) of the printed circuit board (112) of the hybrid coupler (100). Within the scope of the present disclosure, the first metallization layer (116) includes at least two input ports (140) and at least two output ports (150). Figure 1 , 2 As shown in Figures 1 and 5, the first metallization layer (116) includes two input ports (140) and two output ports (150). Figure 2 and Figure 5 In the exemplary embodiment shown, the first metallization layer (116) includes first and second input ports (142, 144) and first and second output ports (152, 154), each of which is implemented as a corresponding conductive pad. The center conductors of the input coaxial cable and the output coaxial cable (120, 130) can be soldered to the corresponding input port and output port (140, 150) for electrical transmission and / or RF signal transmission on the hybrid coupler (100). In addition, the hybrid coupler (100) can include a first input conductive trace (146) connected to the first input port (142) and a second input conductive trace (148) connected to the second input port (144). In the embodiment, the first input conductive trace and the second input conductive trace (146, 148) can each form part of the first metallization layer (116). Within the scope of the present disclosure, the first input conductive trace (146) may form part of a first input microstrip transmission line implemented in a printed circuit board (112), and the second input conductive trace (148) may form part of a second input microstrip transmission line implemented in a printed circuit board (112). The hybrid coupler (100) may also include a first output conductive trace (156) connected to the first output port (152) and a second output conductive trace (158) connected to the second output port (154). In the described embodiment, the first output conductive trace and the second output conductive trace (156, 158) may also form part of the first metallization layer (116). The first output conductive trace (156) may form part of a first output microstrip transmission line implemented in a printed circuit board (112), and the second output conductive trace (158) may form part of a second output microstrip transmission line implemented in a printed circuit board (112).

[0065] In an embodiment of the present disclosure, the input transmission line and the output transmission line can each be implemented as a serpentine microstrip transmission line. This allows the physical length of the hybrid coupler (100) to be reduced while allowing the transmission line to have a desired electrical length. In another embodiment, the output transmission line can include a delay line (not shown) incorporated into the output transmission line. Due to the addition of the delay line, the output transmission line with the delay line has a longer electrical length than the other output transmission line.

[0066] In the context of this disclosure, reference Figure 1 , 2 and 5. The hybrid coupler (100) may include a plurality of couplers (160). The plurality of couplers (160) may be arranged adjacent to each other on a first metallization layer (116) of a printed circuit board (112). According to the present disclosure, the couplers (160) are coupled to each other so that the first metallization layer (116) of the printed circuit board (112) is embodied as a cascade arrangement of the couplers (160). In the cascade arrangement, the conductive traces (146, 148, 156, 158) or transmission lines discussed above may be conceived as conductive traces formed on the plurality of couplers (160). In addition, the first input port and the second input port (142, 144) and the first output port and the second output port (152, 154) of the first metallization layer (116) (discussed above) may be conceived as the first input port and the second input port (142, 144) and the first output port and the second output port (152, 154) of the plurality of couplers (160).

[0067] Within the scope of the present disclosure, each of the plurality of couplers (160) may include a transmission trace (170), such as Figure 1 , 2 and 5. The transmission trace (170) of each coupler (160) can be adapted to electrically couple with the transmission trace (170) of an adjacent coupler (160), such that the transmission traces (170) of the plurality of couplers (160) extend between the first and second input ports (142, 144) and the first and second output ports (152, 154) of the hybrid coupler (100). For example, Figure 5 As shown in the figure, the transmission trace (170) of the first coupler (162) of the plurality of couplers (160) is electrically coupled to the transmission trace (170) of the second coupler (164) of the plurality of couplers (160), and so on, so that the transmission traces (170) of the plurality of couplers (160) extend between the first and second input ports (142, 144) and the first and second output ports (152, 154) of the hybrid coupler (100).

[0068] In an exemplary embodiment of the present disclosure, the hybrid coupler (160) includes four couplers arranged adjacent to each other on the first metallization layer (116), such as Figure 1 , 2 and 5. In the embodiment, the first input port and the second input port (142, 144) are connected to the first coupler (162), and the first output port and the second output port (152, 154) are connected to the fourth coupler (168). In addition, the second coupler (164) and the third coupler (166) are arranged between the first coupler and the fourth coupler (162, 168). Each of the first, second, third and fourth couplers (162, 164, 166, 168) includes a transmission trace (170) formed thereon, such that the transmission trace (170) of the first coupler (162) is electrically coupled to the transmission trace (170) of the second coupler (164), the transmission trace of the second coupler is in turn electrically coupled to the transmission trace (170) of the third coupler (166), and the transmission trace of the third coupler is further electrically coupled to the transmission trace (170) of the fourth coupler (168), thereby electrically coupling the first and second input ports (142, 144) provided on the first coupler (162) with the first and second output ports (152, 154) provided on the fourth coupler (168) for electrical transmission and / or RF signal transmission on the hybrid coupler (100).

[0069] In addition, the hybrid coupler (100) may further include a transmission trace adapted to be connected to the transmission traces (170) of the plurality of couplers (160) and to extend between the transmission traces of the plurality of couplers. Figure 2 The hybrid coupler (100) may include a transmission trace (172) adapted to be connected to a transmission trace (170) of a first coupler (162) and to extend between the transmission traces of the first coupler. The hybrid coupler (100) may also include a transmission trace (174) adapted to be connected to a transmission trace (170) of a second coupler (162) and to extend between the transmission traces of the second coupler. In addition, the hybrid coupler (100) may include a transmission trace (176) adapted to be connected to a transmission trace (170) of a third coupler (166) and to extend between the transmission traces of the third coupler. In addition, the hybrid coupler (100) may include a transmission trace (178) adapted to be connected to a transmission trace (170) of a fourth coupler (168) and to extend between the transmission traces of the fourth coupler.

[0070] refer to Figure 1 ,3 , 4 and 5, the hybrid coupler (100) further includes a second metallization layer (118) disposed below the first metallization layer (116). The second metallization layer (118) may include a ground plane layer. The ground plane layer may include a mostly solid metal layer formed on the bottom surface of a dielectric substrate (114) of the printed circuit board (112). The ground plane layer may serve as a ground plane for an input microstrip transmission line and an output microstrip transmission line, wherein the dielectric substrate (114) separates its conductive / transmission traces from the ground plane layer. In an embodiment, the outer conductors of the input coaxial cable and the output coaxial cable (120, 130) may be soldered to the ground plane layer to provide a ground reference for the ground plane layer. Within the scope of the present disclosure, and with reference to Figure 4 and 5 , the second metallization layer (118) of the printed circuit board (112) may include a defective ground structure (180) defined in a ground plane layer of the second metallization layer (118). In an embodiment, the defective ground structure (180) may be embodied as a (multiple) cutout or (multiple) groove defined in the ground plane layer of the second metallization layer (118). In an alternative embodiment, the defective ground structure (180) may be embodied as metal omitted from the ground plane layer and / or the second metallization layer (118) of the printed circuit board (112).

[0071] According to this disclosure, Figure 5 As shown in , a defective ground structure (180) is defined in the second metallization layer (118) below each coupling joint formed between the transmission traces (170) of the plurality of couplers (160) included in the first metallization layer (116). Figure 5 In the exemplary embodiment of a hybrid coupler (100) including four couplers (160) (wherein a first metallization layer (116) having a transmission trace (170) is superimposed on a second metallization layer (118) defining a defective ground structure (180)), the hybrid coupler (100) includes a defective ground structure (180) formed at each coupling joint formed between the transmission traces (170) of the plurality of couplers (160). Specifically, as Figure 5As can be seen, a first defective ground structure (182) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the first coupler (162) of the first metallization layer (116), a second defective ground structure (184) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the second coupler (164) of the first metallization layer (116), a third defective ground structure (186) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the third coupler (166) of the first metallization layer (116), and a fourth defective ground structure (188) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the fourth coupler (168) of the first metallization layer (116).

[0072] Within the scope of this disclosure, Figure 4 and Figure 5 As shown in , each defective ground structure (180) of the second metallization layer (118) is embodied to have a predefined shape. Therefore, the predefined shape can be selected so that the shape is suitable for reducing the insertion loss in the hybrid coupler (100) during operation of the hybrid coupler (100). Figure 4 and Figure 5 In the exemplary embodiment shown, each defective ground structure (180) in the second metallization layer (118) is embodied in the shape of a rectangle.

[0073] In another embodiment of the present disclosure, the predefined shape of the defective ground structure (180) may be in the shape of a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangular dumbbell, a circular dumbbell, a square dumbbell or a rectangular dumbbell. For example, Figure 5 A top view of a hybrid coupler (100) of the present disclosure is shown, wherein a first metallization layer (116) having a transmission trace (170) is superimposed on a second metallization layer (118) defining a defective ground structure (180) having a "rectangular" shape according to a first embodiment of the present disclosure. Figure 6 A top view of a hybrid coupler (600) of the present disclosure is shown, wherein a first metallization layer (616) having a transmission trace (670) is superimposed on a second metallization layer (618) defining a defective ground structure (680) having a "diamond" shape according to a second embodiment of the present disclosure. Figure 7 A top view of a hybrid coupler (700) of the present disclosure is shown, wherein a first metallization layer (716) having a transmission trace (770) is superimposed on a second metallization layer (718) defining a defective ground structure (780) having a "square dumbbell" shape according to a third embodiment of the present disclosure. Figure 8A top view of a hybrid coupler (800) of the present disclosure is shown, wherein a first metallization layer (816) having a transmission trace (870) is superimposed on a second metallization layer (818) defining a defective ground structure (880) having a "flared dumbbell" shape according to a fourth embodiment of the present disclosure.

[0074] also, Fig. 9 A top view of a hybrid coupler (900) of the present disclosure is shown, wherein a first metallization layer (916) having a transmission trace (970) is superimposed on a second metallization layer (918) defining a defective ground structure (980) having a "triangular dumbbell" shape according to a fifth embodiment of the present disclosure. Fig.10 A top view of a hybrid coupler (1000) of the present disclosure is shown, wherein a first metallization layer (1016) having a transmission trace (1070) is superimposed on a second metallization layer (1018) defining a defective ground structure (1080) having a "rectangular dumbbell" shape according to a sixth embodiment of the present disclosure. Fig.11 A top view of a hybrid coupler (1100) of the present disclosure is shown, wherein a first metallization layer (1116) having a transmission trace (1170) is superimposed on a second metallization layer (1118) defining a defective ground structure (1180) having a "circular dumbbell" shape according to a seventh embodiment of the present disclosure.

[0075] Within the scope of the present disclosure, a defective ground structure (180) defined in the second metallization layer (118) facilitates increasing the electrical length of the trace extending between the transmission traces (170) of the plurality of couplers (160). Thus, the hybrid coupler (100) of the present disclosure provides an increased electrical length of the transmission trace (170) compared to known hybrid couplers. Furthermore, the hybrid coupler (100) of the present disclosure facilitates increasing the electrical length of the transmission trace (170) without increasing the physical length of the hybrid coupler (100). In fact, the hybrid coupler (100) of the present disclosure facilitates increasing the electrical length of the transmission trace (170) with the same or reduced physical length of the hybrid coupler (100). Furthermore, the hybrid coupler (100) of the present disclosure can obtain more output without increasing the physical size of the phase shifter and without affecting other properties of the RF signal (e.g., return loss, amplitude, power distribution, etc.).

[0076] According to the present disclosure, the increased electrical length of the traces extending between the transmission traces (170) helps to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz. In an embodiment of the present disclosure, the electrical length of the traces extending between the transmission traces (170) is 25 mm. In another embodiment of the present disclosure, the defective ground structure (180) defined in the second metallization layer (118) has a length of 9.40 mm and a width of 6.90 mm. In yet another embodiment of the present disclosure, the hybrid coupler (100) can be embodied as a 3 dB 90 degree hybrid coupler.

[0077] In addition, a method for manufacturing the hybrid coupler (100) of the present disclosure is provided. The method includes the steps of designing a printed circuit board (112), the printed circuit board having a first metallization layer (116) and a second metallization layer (118) arranged below the first metallization layer (116). The first metallization layer (116) may include at least two input ports (140) and at least two output ports (150). Figure 1 , 2 As embodied in 5, the first metallization layer (116) includes: two input ports (140), namely, a first input port and a second input port (142, 144); and two output ports (150), namely, a first output port and a second output port (152, 154). Each of the first input port and the second input port (142, 144) and the first output port and the second output port (152, 154) can be implemented as a corresponding conductive pad and is suitable for being soldered to the central conductor of the input coaxial cable and the output coaxial cable (120, 130) for electrical transmission and / or RF signal transmission on the hybrid coupler (100).

[0078] The method may further include the step of providing a plurality of couplers (160) coupled adjacent to each other on the first metallization layer (116). Each coupler (160) of the plurality of couplers (160) may include a transmission trace (170, 172-178) adapted to electrically couple with a transmission trace (170, 172-178) of an adjacent coupler (160). The transmission traces (170) of the plurality of couplers (160) may further extend between first and second input ports (142, 144) and first and second output ports (152, 154) of the first metallization layer (116). In addition, the hybrid coupler (100) may include a first input conductive trace (146) connected to the first input port (142) and a second input conductive trace (148) connected to the second input port (144). In the embodiment, the first input conductive trace and the second input conductive trace (146, 148) may each form part of the first metallization layer (116). Within the scope of the present disclosure, the first input conductive trace (146) may form part of a first input microstrip transmission line implemented in a printed circuit board (112), and the second input conductive trace (148) may form part of a second input microstrip transmission line implemented in a printed circuit board (112). The hybrid coupler (100) may also include a first output conductive trace (156) connected to the first output port (152) and a second output conductive trace (158) connected to the second output port (154). In the embodiment, the first output conductive trace and the second output conductive trace (156, 158) may also form part of the first metallization layer (116). The first output conductive trace (156) may form part of a first output microstrip transmission line implemented in a printed circuit board (112), and the second output conductive trace (158) may form part of a second output microstrip transmission line implemented in a printed circuit board (112). In an embodiment, the input transmission line and the output transmission line may each be implemented as a serpentine microstrip transmission line. This allows the physical length of the hybrid coupler (100) to be reduced while allowing the transmission line to have a desired electrical length. In another embodiment, the output transmission line may include a delay line (not shown) incorporated into the output transmission line. Due to the addition of the delay line, the output transmission line with the delay line has a longer electrical length than the other output transmission line.

[0079] The method further includes the step of defining a defective ground structure (180) having a predefined shape in the second metallization layer (180) below each coupling joint formed between the transmission traces (170) of the plurality of couplers (160) of the first metallization layer (116). The second metallization layer (118) may include a ground plane layer (not shown). The ground plane layer may include a mostly solid metal layer formed on the bottom surface of a dielectric substrate (114) of a printed circuit board. The ground plane layer may serve as a ground plane for an input microstrip transmission line and an output microstrip transmission line, wherein the dielectric substrate (114) separates its conductive traces from the ground plane layer. In an embodiment, the outer conductors of the input coaxial cable and the output coaxial cable (120, 130) may be soldered to the ground plane layer to provide a ground reference for the ground plane layer. It is within the scope of the present disclosure, and with reference to Figure 4 and Figure 5 , the second metallization layer (118) of the printed circuit board (112) may include a defective ground structure (180) defined in a ground plane layer of the second metallization layer (118). In an embodiment, the defective ground structure (180) may be embodied as a (multiple) cutout or (multiple) groove defined in the ground plane layer of the second metallization layer (118). In an alternative embodiment, the defective ground structure (180) may be embodied as metal omitted from the ground plane layer and / or the second metallization layer (118) of the printed circuit board (112).

[0080] According to the present disclosure, a hybrid coupler (100) may include a defective ground structure (180) formed at each coupling joint formed between transmission traces (170) of a plurality of couplers (160). Figure 5 As can be seen, a first defective ground structure (182) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the first coupler (162) of the first metallization layer (116), a second defective ground structure (184) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the second coupler (164) of the first metallization layer (116), a third defective ground structure (186) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the third coupler (166) of the first metallization layer (116), and a fourth defective ground structure (188) is defined in the second metallization layer (118) below the coupling joint between the transmission traces (170) of the fourth coupler (168) of the first metallization layer (116).

[0081] Within the scope of this disclosure, Figure 4 and Figure 5As shown in , each defective ground structure (180) of the second metallization layer (118) is embodied to have a predefined shape. Therefore, the predefined shape can be selected so that the shape is suitable for reducing the insertion loss in the hybrid coupler (100) during operation of the hybrid coupler (100). Figure 4 and Figure 5 In the exemplary embodiment shown, each defective ground structure (180) in the second metallization layer (118) is embodied in a rectangular shape. In other embodiments, without departing from the scope of the present disclosure, the predefined shape of the defective ground structure (180) may be in the shape of a diamond, a square, a trumpet-shaped dumbbell, a triangular dumbbell, a circular dumbbell, a square dumbbell, or a rectangular dumbbell.

[0082] The hybrid coupler (100) of the present disclosure, wherein a defective ground structure (180) is defined in a second metallization layer (118) disposed below a first metallization layer (116) having a plurality of couplers (160), eliminates the need to add (a plurality of) Xinger ICs in the coupler assembly and provides equal power distribution in the hybrid coupler (100). In addition, the hybrid coupler (100) of the present disclosure provides increased bandwidth, optimized power distribution, and reduced manufacturing costs compared to conventional known hybrid couplers. Furthermore, the hybrid coupler (100) of the present disclosure is embodied as a broadband 3-dB orthogonal coupler operable between 1.695-2.690 GHz, and provides technical advantages of high power, 0.2 dB insertion loss, better than 18 dB return loss, and better than 25 dB isolation in the frequency range of 1.695 GHz to 2.69 GHz.

[0083] Without departing from the scope of the present disclosure, the hybrid coupler (100) of the present disclosure is suitable for integration into a feed board for a dual beam antenna (10). For example, the hybrid coupler (100) discussed above can be mounted on a reflector of the dual beam antenna (10), and the metal of the reflector can provide a ground plane reference under the hybrid coupler (100). In addition, multiple radiating elements (12) can be mounted on a printed circuit board 112 of the hybrid coupler (100), so that the printed circuit board (112) is used to implement both the hybrid coupler (100) and the feed board for the radiating elements (12). Fig.12 and 13 As shown in , in some embodiments, the radiating elements (12) may be arranged in a staggered manner. According to an embodiment of the dual beam antenna (10), the staggered arrangement of the radiating elements (12) may include a horizontal arrangement, a vertical arrangement, an offset arrangement, or a combination thereof of the radiating elements (12). Fig.12 As shown in the exemplary embodiment of the present invention, the dual beam antenna (10) may include radiating elements (12) arranged in an offset layout. Fig.13 As shown in an exemplary embodiment of the present invention, a dual beam antenna (10) may include radiating elements (12) arranged in an array of radiating elements (12) having a combination of horizontal and vertical layouts. The staggered arrangement of the radiating elements (12) may facilitate increasing isolation between adjacent columns of radiating elements and / or increasing the gain of the dual beam antenna (10).

[0084] Various embodiments of the present disclosure have been described above with reference to the accompanying drawings. The present disclosure is not limited to the embodiments shown; on the contrary, these embodiments are intended to fully and completely disclose the subject matter of the present disclosure to those skilled in the art. In the accompanying drawings, the same reference numerals always represent the same elements. For the sake of clarity, the thickness and size of some components may be exaggerated.

[0085] For ease of description, spatially relative terms, such as "below", "below", "down", "above", "up", "top", "bottom", etc., may be used herein to describe the relationship of one element or feature to another element or feature as shown in the figure. It should be understood that spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, the elements described as being "below" or "below" other elements or features will be oriented as "above" other elements or features. Therefore, the exemplary term "below" can cover both the orientation of above and below. The device can be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0086] Herein, unless otherwise stated, the terms “attached,” “connected,” “interconnected,” “contacting,” “mounted,” “coupled,” and the like may mean direct or indirect attachment or contact between elements.

[0087] For brevity and / or clarity, well-known functions or constructions may not be described in detail.As used herein, the expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0088] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It will be further understood that when used in this specification, the terms "comprises", "comprising", "includes", and / or "including" specify the presence of the features, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, operations, elements, parts, and / or combinations thereof.

[0089] Although considerable emphasis has been placed herein on the specific features of the present disclosure, it should be recognized that various modifications and numerous changes may be made in the preferred embodiments without departing from the principles of the present disclosure. These and other modifications of the nature of the present disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it should be clearly understood that the above descriptive matters are interpreted only as illustrations of the present disclosure and not as limitations.

[0090] Reference numerals

[0091]

[0092]

[0093] Equivalent solutions:

[0094] The embodiments herein and their various features and advantageous details are explained with reference to the non-limiting examples in the description. Descriptions of well-known components and processing techniques are omitted so as not to unnecessarily confuse the embodiments herein. The examples used herein are intended only to facilitate an understanding of the ways in which the embodiments herein may be practiced, and also to enable those skilled in the art to practice the embodiments herein. Therefore, the examples should not be construed as limiting the scope of the embodiments herein.

[0095] The above description of specific embodiments will fully reveal the general nature of the embodiments herein so that others can easily modify and / or adapt various applications of such specific embodiments by applying current knowledge without departing from the general concept, and therefore, such adaptations and modifications should and are intended to be understood within the meaning and scope of the equivalents of the disclosed embodiments. It should be understood that the phrases or terms used herein are for descriptive and not limiting purposes. Therefore, although the embodiments herein have been described according to preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced by modification within the spirit and scope of the embodiments as described herein.

[0096] Throughout this specification, the word "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated element, integer or step, or a group of elements, integers or steps, but not the exclusion of any other element, integer or step, or a group of elements, integers or steps.

[0097] The use of the expression "at least" or "at least one" indicates the use of one or more elements or ingredients or amounts, as used in embodiments of the present disclosure to achieve one or more desired objectives or results.

[0098] Any discussion of documents, acts, materials, devices, articles of manufacture etc. included in this specification is solely for the purpose of providing a context for the present disclosure. It should not be taken as an admission that any or all of these matters form part of the prior art base or are common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

[0099] Numerical values ​​mentioned for various physical parameters, dimensions or amounts are approximations only, and values ​​above / below the numerical value assigned to the parameter, dimension or amount are contemplated to fall within the scope of the present disclosure unless the specification specifically states to the contrary.

Claims

1. A hybrid coupler, comprising: a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer, the first metallization layer comprising at least two input ports and at least two output ports; a plurality of couplers coupled adjacent to each other on the first metallization layer, each coupler of the plurality of couplers comprising a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extending between an input port and an output port of the first metallization layer; as well as A defective ground structure having a predefined shape is defined in the second metallization layer below each coupling joint formed between the transmission traces of the plurality of couplers.

2. The hybrid coupler according to claim 1, wherein the predefined shape of the defective ground structure is a rectangle, a diamond, a square, a trumpet-shaped dumbbell, a triangle-shaped dumbbell, a circular dumbbell, a square dumbbell or a rectangular dumbbell. 3 . The hybrid coupler of claim 1 , wherein the hybrid coupler comprises four coupler cells on the first metallization layer.

4. The hybrid coupler of claim 1, wherein the defective ground structure is configured to increase an electrical length of a trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz.

5. The hybrid coupler of claim 4, wherein the electrical length of the trace extending between the transmission traces is 25 mm. 6 . The hybrid coupler of claim 1 , wherein the defective ground structure has a length of 9.40 mm and a width of 6.90 mm. The hybrid coupler according to claim 1 , wherein the hybrid coupler is a 3 dB 90 degree hybrid coupler.

8. The hybrid coupler of claim 1, wherein the defective ground structure comprises one or more cutouts defined in a ground plane layer of the second metallization layer.

9. A method of manufacturing a hybrid coupler, the method comprising: Designing a printed circuit board, the printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer, the first metallization layer comprising at least two input ports and at least two output ports; Disposing a plurality of couplers coupled adjacent to each other on the first metallization layer, each of the plurality of couplers comprising a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extending between an input port and an output port of the first metallization layer; as well as A defective ground structure having a predefined shape is defined in the second metallization layer below each coupling joint formed between transmission traces of the plurality of couplers.

10. The method of claim 9, wherein defining the defective ground structure in the predefined shape comprises defining the defective ground structure in the shape of a rectangle, a diamond, a square, a flared dumbbell, a triangular dumbbell, a circular dumbbell, a square dumbbell, or a rectangular dumbbell.

11. A dual bean antenna, comprising: A hybrid coupler, the hybrid coupler being adapted to mount a radiating element thereon, the hybrid coupler comprising: a printed circuit board having a first metallization layer and a second metallization layer arranged below the first metallization layer, the first metallization layer comprising at least two input ports and at least two output ports; a plurality of couplers coupled adjacent to each other on the first metallization layer, each coupler of the plurality of couplers comprising a transmission trace electrically coupled to a transmission trace of an adjacent coupler, and the transmission traces of the plurality of couplers extending between an input port and an output port of the first metallization layer; and A defective ground structure having a predefined shape is defined in the second metallization layer below each coupling joint formed between the transmission traces of the plurality of couplers.

12. The dual bean antenna according to claim 11, wherein the predefined shape of the defective ground structure is a rectangle, a diamond, a square, a horn-shaped dumbbell, a triangle dumbbell, a circular dumbbell, a square dumbbell or a rectangular dumbbell.

13. The dual bean antenna of claim 11, wherein the hybrid coupler comprises four coupler elements on the first metallization layer.

14. The dual beam antenna of claim 11, wherein the defective ground structure is configured to increase an electrical length of a trace extending between the transmission traces to achieve uniform power distribution over a frequency band of 1.695 MHz to 2.690 MHz.

15. The dual beam antenna of claim 14, wherein the electrical length of the traces extending between the transmission traces is 25 mm.

16. The dual beam antenna of claim 11, wherein the defective ground structure has a length of 9.40 mm and a width of 6.90 mm.

17. The dual beam antenna of claim 11, wherein the hybrid coupler is a 3 dB 90 degree hybrid coupler.

18. The dual bean antenna of claim 11, wherein the radiating elements are arranged in a staggered arrangement.

19. The dual bean antenna of claim 18, wherein the staggered arrangement of the radiating elements comprises a horizontal layout, a vertical layout, an offset layout, or a combination thereof of the radiating elements.

20. The dual bean antenna of claim 11, wherein the defective ground structure comprises one or more cutouts defined in a ground plane layer of the second metallization layer.

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