A miniaturized 5G broadband automotive glass antenna

Abstract

The present invention relates to a miniaturized 5G broadband automotive glass antenna, comprising: a first component having a groove first formed thereon, the arrangement of which forms a defective ground structure; a second component serving as a feed structure for powering the antenna; a third component connected to the second component for powering the third component, the third component being a monopole structure; and a fourth component connected at one end to the first component, the fourth component having a bend for reducing the area of ​​the radiating structure and adjusting low-frequency impedance matching. The miniaturized 5G broadband automotive glass antenna of the present invention utilizes a single-sided design based on a glass dielectric, reducing the possibility of damage to the three-dimensional structure while preserving the mechanical properties of the glass. The bandwidth covers both the 4G LTE band and the commonly used 5G band, and exhibits a good +z radiation pattern within each band. The defective ground structure significantly reduces the need for a large metal floor while achieving excellent low-frequency broadband.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a miniaturized 5G broadband automobile glass antenna. Background Art

[0002] Existing in-vehicle ultra-wideband 5G antennas often use monopole antennas integrated into shark fins. This three-dimensional antenna design, standing upright on the vehicle roof, has a high profile and is susceptible to external influences and damage. However, with the increasing use of panoramic sunroofs and the automotive industry's demand for streamlined bodies, antenna layout space has been significantly limited. Therefore, traditional shark fin antenna designs are difficult to adapt to new design requirements.

[0003] Through the study of existing shark fin antennas, it was found that different shark fin antennas have different problems:

[0004] 1) A broadband monopole antenna capable of covering the 698 to 960 MHz and 1710 to 2690 MHz frequency bands. However, these antennas are often three-dimensional structures with high cross-sections, making them susceptible to damage from the external environment. Furthermore, the shark fin antenna's requirement for a large sheet metal structure makes it difficult to adapt to the design requirements of a panoramic sunroof. Furthermore, to achieve the compact design of the shark fin structure, multiple antennas are often integrated within a limited space, resulting in significant mutual interference and making the design even more difficult.

[0005] 2) A printed planar monopole broadband antenna successfully covers the 698MHz-960MHz and 1653MHz-3058MHz frequency bands by incorporating a ground strip and loop structure. However, this antenna also requires a large metal ground structure to support its broadband characteristics, resulting in a large footprint. If the metal ground surface is reduced, the antenna's low-frequency bandwidth will be significantly reduced, making it difficult to meet the 5G broadband coverage requirements.

[0006] 3) A double-layer 5G antenna successfully covers 0.824 GHz to 6 GHz using a double-layer ground structure and radiating elements. However, this double-layer ground structure requires vias for connection. Drilling holes in the glass would severely damage its mechanical properties, making it unsuitable for actual automotive applications. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the following problems in the prior art:

[0008] 1) Traditional monopole antennas embedded in shark fins are typically three-dimensional structures, placed vertically on a metal floor. This creates a high profile and is susceptible to environmental damage. Furthermore, multiple antennas integrated within a limited space can interfere with each other, making design difficult and costly.

[0009] 2) Currently, in order to maintain wide-band coverage, planar broadband antennas often use large metal environments to ensure impedance bandwidth performance, resulting in a large occupied area and difficulty in miniaturization.

[0010] 3) Although the double-layer structure successfully expands the bandwidth, it still fails to cover the 4G LTE700 frequency band. At the same time, this type of solution often requires punching holes in the dielectric plate, which will seriously damage the mechanical properties of the glass and increase the difficulty of antenna design and processing costs.

[0011] In order to solve the above technical problems, the present invention provides a miniaturized 5G broadband automobile glass antenna, comprising: component one, which is used as a ground structure, and a groove one is provided on the component one, and the setting of the groove one makes the component one constitute a defective ground structure; component two, which is arranged on component one, and component two is used as a feeding structure for powering the antenna; component three, which is connected to component two, and a feeding point is provided between component two and component three, and component two is used to power component three, and component three is a monopole structure; the monopole structure of component three includes a monopole central branch extending outward from the feeding point position, a monopole left branch located on the left side of the monopole central branch, and two monopole right branches located on the right side of the monopole central branch; the monopole left branch is located on the side of component three close to the groove one, and the monopole left branch constitutes L Component seven has a rectangular bending structure, and component seven extends from one end of component three to be arranged opposite to groove one; the two monopole right branches include a horizontal right branch and a stepped right branch, and the end of the horizontal right branch away from component seven extends outward in a direction parallel to the long side of the rectangle of component one; the stepped right branch forms a stepped structure from left to right, forming a right-angle bending portion, and the right-angle bending portion is located at the corner position of component three close to component one, and the right-angle bending portion is recessed into component three; the right-angle bending portion is connected to the horizontal right branch at the connection point of the horizontal right branch, and the connection point is located at the non-end point of the horizontal right branch, so that a closed loop structure is formed between the right-angle bending portion, the monopole central branch and the horizontal right branch; component four, one end of which is connected to component one, and component four is provided with a bending portion, and component four is a short-circuit branch, and the bending portion is used to reduce the area of ​​the radiation structure and adjust the impedance matching of the low frequency; components one, three and four are all installed on the automobile glass. This miniaturized 5G broadband automotive glass antenna features: 1) a single-sided glass dielectric design, minimizing the risk of damage to the three-dimensional structure while preserving the mechanical properties of glass. 2) its bandwidth covers both the 4G LTE and commonly used 5G frequency bands, with excellent +z radiation patterns within each band. 3) its use of a defective ground structure significantly reduces the need for a large metal floor, while achieving excellent low-frequency broadband.

[0012] In one embodiment of the present invention, a feeding point is provided between the second component and the third component, and the feeding point is used to connect the second component and the third component.

[0013] In one embodiment of the present invention, the cross-section of component one is rectangular, the groove one is a rectangular groove, the groove one is arranged on the long side of one side of component one, the component two is arranged at one end of component one where groove one is provided, and the component four is connected to the long side of component one where groove one is provided.

[0014] In one embodiment of the present invention, component two is a coaxial line, and component two includes component five and component six, component five is the inner core of the coaxial line, component six is ​​the outer core of the coaxial line, and component six is ​​wrapped around the outer wall of component five, and one end of component five extends out of component six and is connected to the feeding point.

[0015] In one embodiment of the present invention, the component three is a "mouth" shaped structure, and a component seven is provided on the side of the component three close to the groove one. The component seven is an L-shaped bending structure, and the component seven extends from one end away from the component three to be arranged opposite the groove one.

[0016] In one embodiment of the present invention, a right-angle bend is provided on one side of component three close to component four. The right-angle bend is located at the corner of component three close to component one, and the right-angle bend is recessed into component three.

[0017] In one embodiment of the present invention, the component 4 extends from one end of the component 1 to form a straight portion, the straight portion is parallel to the long side of the rectangle of the component 1, and the straight portion extends to be opposite to the groove 1.

[0018] In one embodiment of the present invention, the straight portion and the bent portion are arranged at a right angle, and the straight portion is located on a side of component seven away from component one.

[0019] In one embodiment of the present invention, one end of the component seven is perpendicular to the side of the component three, and the side of the component seven perpendicular to the component three is parallel to the long side of the rectangle of the component one.

[0020] In one embodiment of the present invention, the bending portion is a U-shaped reciprocating bending structure.

[0021] The miniaturized 5G broadband automotive glass antenna of the present invention has the following advantages compared to the prior art:

[0022] 1) To address the issues with traditional 5G antennas using shark fin structures, which are susceptible to environmental influences and interference between multiple antennas, this invention proposes a planar design that integrates the antenna directly onto the glass. This significantly reduces the design requirements for the antenna's profile height and mitigates the vulnerability of the three-dimensional structure to damage. Furthermore, this invention's 5G automotive glass antenna eliminates the need for a compact layout, offers a high degree of design freedom, effectively minimizes interference between multiple antennas, and reduces antenna design complexity and manufacturing costs.

[0023] 2) In response to the technical problem that current printed 5G antennas use a large-scale metal environment for bandwidth performance, the present invention successfully introduces a new resonance point by utilizing a defective ground structure, which not only meets the antenna's low-frequency broadband coverage requirements, but also has a compact structure and occupies a small area, realizing a miniaturized broadband design.

[0024] 3) To address the problem that the current double-layer 5G broadband antenna requires drilling holes in the substrate, the present invention proposes a single-sided structural design with the advantage of multiple independently adjustable frequency bands, solving the technical problem of damaging the mechanical properties of the glass by requiring via holes to connect the antenna to the ground in order to achieve miniaturization and multi-bandwidth coverage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0026] Figure 1 This is a diagram showing the installation location of a miniaturized 5G broadband automotive glass antenna in a preferred embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of a miniaturized 5G broadband automotive glass antenna in a preferred embodiment of the present invention. Figure 1 ;

[0028] Figure 3 This is a side view of a miniaturized 5G broadband automotive glass antenna in a preferred embodiment of the present invention;

[0029] Figure 4 This is a dimensioned diagram of a miniaturized 5G broadband automotive glass antenna in a preferred embodiment of the present invention;

[0030] Figure 5 This is a simulation diagram of the reflection coefficient of the miniaturized 5G broadband automotive glass antenna in the preferred embodiment of the present invention;

[0031] Figure 6 This is a simulation diagram of the peak gain of the miniaturized 5G broadband automotive glass antenna in the operating frequency band in the preferred embodiment of the present invention;

[0032] Figure 7The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 0.7 GHz in the preferred embodiment of the present invention;

[0033] Figure 8 The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 0.8 GHz in the preferred embodiment of the present invention;

[0034] Figure 9 The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 2.0 GHz in the preferred embodiment of the present invention;

[0035] Figure 10 The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 2.3 GHz in the preferred embodiment of the present invention;

[0036] Figure 11 The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 3.8 GHz in the preferred embodiment of the present invention;

[0037] Figure 12 The radiation pattern of the miniaturized 5G broadband automotive glass antenna at 4.5 GHz in the preferred embodiment of the present invention;

[0038] Figure 13 This is the structural evolution process 1 of the miniaturized 5G broadband automotive glass antenna in the preferred embodiment of the present invention;

[0039] Figure 14 This is the second structural evolution process of the miniaturized 5G broadband automotive glass antenna in the preferred embodiment of the present invention;

[0040] Figure 15 This is the third structural evolution process of the miniaturized 5G broadband automotive glass antenna in the preferred embodiment of the present invention;

[0041] Figure 16 This is a performance change diagram of the evolution of the miniaturized 5G broadband automotive glass antenna in the preferred embodiment of the present invention.

[0042] Explanation of the reference numerals in the specification: automobile glass 1, component two 2, component five 21, component six 22, feeding point 3, component three 4, component seven 41, right-angle bending portion 42, component four 5, bending portion 51, straight portion 52, component one 6, groove one 61. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0044] Reference Figure 1-3As shown, the miniaturized 5G broadband automotive glass antenna of the present invention comprises: component 1 (6), component 2 (2), component 3 (4), and component 4 (5). Component 1 (6) serves as a ground structure and is provided with a groove 1 (61). This groove 61 creates a defective ground structure. Component 2 (2) is mounted on component 1 (6) and serves as a feed structure for powering the antenna. Component 3 (4) is connected to component 2 (2) and is used to power component 3 (4). Component 3 (4) is a monopole structure. Component 4 (5) has one end connected to component 1 (6) and is provided with a U-shaped reciprocating bend 51. Component 4 (5) is a short-circuit branch and is used to reduce the area of ​​the radiating structure and adjust low-frequency impedance matching. Components 1 (6), 3 (4), and 4 (5) are all mounted on automotive glass (1). Specifically, the glass has a dielectric constant of 7, a loss tangent of 0.01, and a thickness of 2.1 mm.

[0045] The miniaturized 5G broadband automotive glass antenna of the present invention proposes a new idea of ​​integrating the 5G antenna with the automotive functional glass, involving the field of wireless communications. The antenna bandwidth can cover the commonly used 4G LTE and 5G frequency bands.

[0046] In the above structure, a feeding point 3 is provided between the second component 2 and the third component 4 , and the feeding point 3 is used to connect the second component 2 and the third component 4 .

[0047] In the above structure, the cross-section of component 1 (6) is rectangular, and the groove 1 (61) is a rectangular groove. The groove 1 (61) is located on the long side of component 1 (6). Component 2 (2) is located at the end of component 1 (6) where groove 1 (61) is located. Component 4 (5) is connected to the long side of component 1 (6) where groove 1 (61) is located. Component 3 (4) and component 4 (5) are located on the same side of groove 1 (61), with component 3 (4) located between component 4 (5) and groove 1 (61).

[0048] In the above structure, the component 2 2 is a coaxial cable, and the component 2 2 includes the component 5 21 and the component 6 22, the component 5 21 is the inner core of the coaxial cable, the component 6 22 is the outer core of the coaxial cable, and the component 6 22 is wrapped on the outer wall of the component 5 21, and one end of the component 5 21 extends out of the component 6 22 and is connected to the feeding point 3.

[0049] In the above structure, the third component 4 is in the shape of a square. A seventh component 41 is provided on the side of the third component 4 near the groove 1 61. This seventh component 41 has an L-shaped bend, extending from the end of the third component 4 to face the groove 1 61. A right-angled bend 42 is provided on the side of the third component 4 near the fourth component 5. This right-angled bend 42 is located at the corner of the third component 4 near the first component 6 and is recessed into the third component 4. One end of the seventh component 41 is perpendicular to the side of the third component 4, and the seventh component 41 is parallel to the long side of the rectangle of the first component 6.

[0050] In the above structure, the end of the component 4 (5) away from the component 1 (6) extends to form a straight portion 52. The straight portion 52 is parallel to the long side of the rectangle of the component 1 (6) and extends to face the groove 1 (61). The straight portion 52 is arranged at a right angle to the bent portion 51 and is located on the side of the component 7 (41) away from the component 1 (6).

[0051] The miniaturized 5G broadband automotive glass antenna of the present invention has an overall dimension of 150mm × 60mm × 2.1mm and is fed via a coaxial cable. Component 5 21 is the inner core of the coaxial cable, while Component 6 22 is the outer core. Feed point 3 is provided. Preferably, the antenna of the present invention is mounted on the lower right corner of the automotive glass 1. Its main components include an improved monopole structure (Component 3 4), a curved short-circuit branch (Component 4 5), and a defective ground structure (Component 1 6). The left monopole branch (Component 7 41) has an L-shaped bend, with the horizontal and vertical branches having different line widths. The right monopole branch (right-angle bend 42) is a right-angle structure, with the lower right corner forming a stepped structure from left to right. The short-circuit branch (Component 4 5) uses a continuously curved line structure to reduce the radiating structure area and adjust the low-frequency impedance matching. The defective ground structure (Component 1 6) creates a rectangular slot in the antenna's radiating ground.

[0052] Reference Figure 2As shown, the miniaturized 5G broadband automotive glass antenna of the present invention is mainly composed of a printed monopole structure. In order to better cover the required frequency band, the initial value of the length of the left branch AB of the monopole is set to a quarter wavelength of the 1GHz frequency, and the initial length of the branch AC is set to a quarter wavelength of the 2GHz frequency. The impedance matching characteristics of the monopole antenna can be effectively improved by adjusting the line width of component seven 41 and the stage structure of the right-angle bend 42. When the monopole antenna is excited, broadband coverage from 1.81GHz to 6GHz can be achieved. However, the low-frequency coverage of the antenna is poor at this time. For this reason, the present invention introduces a short-circuit structure component four 5, the vertical bend part is connected to the rectangular ground structure, and the other end extends out to form a horizontal straight strip parallel to the rectangular ground structure. The introduction of this structure can effectively improve the impedance matching near 1GHz. However, its low-frequency working bandwidth is still very narrow at this time. In order to further widen the low-frequency working bandwidth without affecting the characteristics of the medium and high frequencies, the present invention digs out a rectangular groove one 61 on the left side of the feeding point to form a defective ground structure. This defective ground structure can generate additional resonance points near 0.6 GHz. By adjusting the size and position of the gap, the operating bandwidth at low frequencies is greatly improved, ultimately successfully achieving coverage from 0.617 GHz to 0.96 GHz, meeting design requirements.

[0053] Reference Figure 4 As shown in the figure, the specific dimensions of the antenna are as follows: GND_X=30mm; GND_Y=150mm; ANT_X=30mm;ANT_Y=68mm; CX=25mm; CY=30mm; C1=0.5mm; L1=29mm; L2=16.2mm; L3=25mm; T1=12.4mm; T2=10mm; H1=18.2mm; H=2.1mm; D1=1mm; D2=4mm.

[0054] Reference Figure 13-15 As shown, the structural evolution process of the miniaturized 5G broadband automotive glass antenna of the present invention is as follows: In order to achieve 5G multi-frequency coverage, the present invention first adopts a single basic printed monopole structure, such as Figure 13 As shown in Model 1, it can well meet the coverage of the mid- and high-frequency bands, with the reflection coefficient amplitude from 1.81GHz to 6GHz being less than -6dB. However, its low-frequency matching characteristics are poor. In order to widen the bandwidth of the low-frequency band, the present invention adds a short-circuit structure to introduce a new resonance point, such as Figure 14 As shown in Model 2, the reflection coefficient at 1GHz is improved to close to -6dB, while the characteristics of the mid- and high-frequency frequencies remain basically unchanged. On this basis, by adding a defective ground structure, such as Figure 15As shown in Model 3, the current path of the floor is changed, a new resonance point is introduced at low frequency, and the low-frequency resonance of the monopole structure is further compensated, thereby obtaining a low-frequency broadband covering 0.617GHz-1.1GHz. Figure 16 As shown, the performance changes of the miniaturized 5G broadband automotive glass antenna of the present invention are shown.

[0055] Figure 5 The simulated and measured graphs show the relationship between the antenna's reflection coefficient and frequency. The graphs show that the antenna's reflection coefficient is less than -6dB within the commonly used bandwidths of 0.617GHz-0.96GHz, 1.71GHz-2.69GHz, and 3.3GHz-5GHz, which are the 4G LTE and 5G bands. The antenna also exhibits good resonance, with the deepest resonance points falling well within the operating frequency band.

[0056] Figure 6 The actual gain of the antenna within the operating frequency band is shown. The peak gain is above 2.8dB in the 0.617GHz-0.96GHz range, around 8dB in the 1.71GHz-2.69GHz range, and around 5dB in the 3.3GHz-5GHz range. The maximum peak gain can reach 8dB.

[0057] Figure 7-12 The radiation patterns of the antenna of the present invention at different frequencies in the XOZ and YOZ planes are shown. The antenna radiation pattern can maintain a good radiation effect in the +z direction at different frequencies.

[0058] The miniaturized 5G broadband automotive glass antenna of the present invention:

[0059] 1) Utilizes the concept of direct integration of the radiating element with the vehicle's glass. Unlike traditional monopole antennas, this invention utilizes a conformal design of the radiating element to the vehicle's glass, resulting in a two-dimensional planar structure that reduces the antenna's vulnerability to damage from external influences.

[0060] 2) Design using defective ground structure to improve low-frequency resonance. This invention uses defective ground structure to change the current path of the floor, allowing the floor to form effective resonance, significantly reducing the reliance on large-area metal floors and effectively reducing antenna size.

[0061] 3) 5G broadband features covering the entire frequency band. Compared with existing 5G antennas, this invention achieves coverage of the frequency bands from 0.617GHz to 0.96GHz and 1.71GHz to 5GHz, and stable +Z direction radiation.

[0062] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A miniaturized 5G broadband automotive glass antenna, characterized in that: include: Component 1, which serves as a ground structure, is provided with a groove 1, and the arrangement of the groove 1 causes component 1 to form a defective ground structure; Component 2, which is disposed on component 1 and serves as a feeding structure for supplying power to the antenna; Component three is connected to component two, and a feeding point is provided between component two and component three. Component two is used to supply power to component three, and component three is a monopole structure; the monopole structure of component three includes a monopole central branch extending outward from the feeding point position, a monopole left branch located on the left side of the monopole central branch, and two monopole right branches located on the right side of the monopole central branch; the monopole left branch is located on the side of component three close to groove one, and the monopole left branch constitutes component seven of an L-shaped bending structure, and component seven extends from one end of component three to the groove one and is arranged opposite thereto; the two monopole right branches include a monopole central branch located on the left side of the monopole central branch, and a monopole left branch located on the right side of the monopole central branch; the monopole left branch is located on the side of component three close to groove one, and the monopole left branch constitutes component seven of an L-shaped bending structure, and component seven extends from one end of component three to the groove one and is arranged opposite thereto; the two monopole right branches include a monopole central branch located on the left side of the monopole central branch, and the monopole left branch is located on the left side of the monopole central branch, and the monopole left branch is located on the right side of the monopole central branch, and the monopole left branch is arranged on the right side of the monopole central branch; the monopole left branch is located on the side of component three close to groove one, and the monopole left branch constitutes component seven of an L-shaped bending structure, and the monopole left branch is located on the left side of the monopole central branch, and the monopole left branch is located on the left side of the monopole central branch, and the monopole left branch is arranged on the right side of the monopole central branch; the monopole left branch is located on the left side of the monopole central branch, and the monopole left branch is arranged on the right side of the monopole central branch; the monopole left branch is The invention comprises a horizontal right branch and a stepped right branch, wherein the end of the horizontal right branch away from component seven extends outward in a direction parallel to the long side of the rectangle of component one; the stepped right branch forms a stepped structure from left to right, forming a right-angled bend portion, the right-angled bend portion is located at the corner position of component three close to component one, and the right-angled bend portion is recessed into the interior of component three; the right-angled bend portion is connected to the horizontal right branch at a connection point of the horizontal right branch, and the connection point is located at a non-end point of the horizontal right branch, so that a closed loop structure is formed between the right-angled bend portion, the monopole central branch and the horizontal right branch; Component 4, one end of which is connected to component 1 and provided with a bent portion, which is a short-circuit branch. The bent portion is used to reduce the area of ​​the radiation structure and adjust the low-frequency impedance matching; The component one, component three and component four are all installed on automobile glass.

2. The miniaturized 5G broadband automotive glass antenna according to claim 1, characterized in that: A feeding point is provided between the second component and the third component, and the feeding point is used to connect the second component and the third component.

3. The miniaturized 5G broadband automotive glass antenna according to claim 1, characterized in that: The cross-section of component one is rectangular, the groove one is a rectangular groove, the groove one is arranged on the long side of one side of component one, the component two is arranged at the end of component one where groove one is provided, and the component four is connected to the long side of component one where groove one is provided.

4. The miniaturized 5G broadband automotive glass antenna according to claim 2, characterized in that: Component 2 is a coaxial line, and component 2 includes component 5 and component 6. Component 5 is the inner core of the coaxial line, and component 6 is the outer core of the coaxial line. Component 6 is wrapped around the outer wall of component 5, and one end of component 5 extends out of component 6 and is connected to the feeding point.

5. The miniaturized 5G broadband automotive glass antenna according to claim 1, characterized in that: The fourth component extends from one end of the first component to form a straight portion, the straight portion is parallel to the long side of the rectangle of the first component, and the straight portion extends to be arranged opposite to the first groove.

6. The miniaturized 5G broadband automotive glass antenna according to claim 5, characterized in that: The straight portion is arranged at a right angle to the bent portion, and the straight portion is located on a side of component seven away from component one.

7. The miniaturized 5G broadband automotive glass antenna according to claim 1, characterized in that: One end of the component seven is perpendicular to the side of the component three, and the side of the component seven perpendicular to the component three is parallel to the long side of the rectangle of the component one.

8. The miniaturized 5G broadband automotive glass antenna according to claim 1, characterized in that: The bending portion is a U-shaped reciprocating bending structure.

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