CN1851978A - Wide-frequency-band double-way-band incongruous medium transmission wire - Google Patents

Abstract

Translated fromChinese

一种宽频带双通带异向介质传输线，它涉及涉及异向介质技术领域，它解决了现有的异向介质传输线电尺寸大、加工困难、成本高、带宽窄的问题。本发明的异向介质传输线由多个异向介质单元串联构成，每个异向介质单元中第一层介质板(1)的上表面的中间沿Y方向刻蚀有一个金属条带(1－1)，第一C形金属方环(1－3)和第二C形金属方环(1－2)以金属条带(1－1)为对称轴对称设置；第二层介质板(2)的上表面的中间沿X方向刻蚀有第三C形金属方环(2－1)和第四C形金属方环(2－2)；底层金属箔(3)上设置有两个相同且相互连通的方形通孔。本发明的异向介质传输线具有双通频带特性，单元体积小、加工容易、成本低廉，且带宽宽、损耗小。

A wide-band double-pass-band heterotropic medium transmission line relates to the technical field of heterotropic mediums, and solves the problems of the existing heterotropic medium transmission lines such as large electrical size, difficult processing, high cost and narrow bandwidth. The anisotropic dielectric transmission line of the present invention is composed of a plurality of anisotropic dielectric units connected in series, and in each anisotropic dielectric unit, a metal strip (1- 1), the first C-shaped metal square ring (1-3) and the second C-shaped metal square ring (1-2) are arranged symmetrically with the metal strip (1-1) as the symmetrical axis; the second layer of dielectric board (2 ) is etched with a third C-shaped metal square ring (2-1) and a fourth C-shaped metal square ring (2-2) along the X direction in the middle of the upper surface; the bottom metal foil (3) is provided with two identical and interconnected square through holes. The anisotropic dielectric transmission line of the present invention has the characteristics of double-pass frequency band, small unit volume, easy processing, low cost, wide bandwidth and low loss.

Description

Translated fromChinese

一种宽频带双通带异向介质传输线A wide-band double-pass-band anisotropic dielectric transmission line

技术领域technical field

本发明涉及异向介质技术领域。The invention relates to the technical field of heterotropic media.

背景技术Background technique

异向介质是20世纪90年代末期出现的一种新型周期结构的人工电磁媒质，它同时具有负值的介电常数和负值的磁导率，导致在该媒质中传播的电磁波的电场E，磁场H以及波矢量k三者构成左手系，而不是遵循常规媒质的右手法则，故而其又被称为异向介质。异向介质的概念雏形需要追溯到20世纪60年代，前苏联物理学家Veselago首次从理论上对它进行了研究，并且预言了异向介质具有一系列超常规的电磁特性，包括：左手特性，负折射特性，逆多普勒效应，逆切伦科夫辐射效应等。由于自然界中并没有发现异向介质，所以异向介质理论在此后近三十年的时间里缺乏实验证实一直停留在理论的层面。2000年Smith基于Pendry的研究结果通过将细导线阵列与开口方环阵列合理布局，历史上第一次制造出了异向介质，这一突破性成果使得该领域的研究进入了实质性阶段。然而上述的异向介质因其结构复杂、带宽窄、损耗大以及体积大的问题使其距离实际应用有较大的差距。Anisotropic medium is a new type of artificial electromagnetic medium with periodic structure that appeared in the late 1990s. It has both negative permittivity and negative magnetic permeability, resulting in the electric field E of the electromagnetic wave propagating in the medium, The magnetic field H and the wave vector k form a left-handed system, instead of following the right-handed rule of conventional media, so it is also called an anisotropic medium. The prototype of the concept of heterotropic medium needs to be traced back to the 1960s. Veselago, a former Soviet physicist, studied it theoretically for the first time, and predicted that the heterotropic medium has a series of unconventional electromagnetic properties, including: left-handed characteristics, Negative refraction characteristics, inverse Doppler effect, inverse Cerenkov radiation effect, etc. Since no heterotropic medium has been found in nature, the theory of metaisotropic medium has remained at the theoretical level for nearly three decades without experimental confirmation. In 2000, based on Pendry's research results, Smith produced a heterotropic medium for the first time in history by rationally arranging the thin wire array and the open square ring array. This breakthrough made the research in this field enter a substantive stage. However, the above-mentioned anisotropic medium has a large gap from practical application due to its complex structure, narrow bandwidth, large loss and large volume.

基于这种状况，很多学者在新型异向介质设计方面展开研究。到目前为止已经有多种新型结构的异向介质被设计、制造出来，其中包括传输线结构异向介质，结构单元为Ω形的异向介质，开口方环结构的异向介质，结构单元为S型、双S形的异向介质，结构单元为螺旋型的异向介质，由CLSs和CLLs相交替构成的异向介质等。虽然异向介质的新型结构层出不穷，但是它们可以归纳为两大类：一类是基于Smith教授的开口方环结构的改进或者衍生结构，另一类是基于传输线结构异向介质改进或衍生结构，尤其需要指出的是，传输线结构异向介质由于其更多地以一种具有异向介质电磁特性的传输线的形式被应用，因此其又被称为异向介质传输线。最初的异向介质的相对带宽很窄(约0.5％)，尺寸较大(约0.2个波长)，而且不宜于加工，经过持续的改良和衍生之后性能已经有了很大的改善。例如由陈抗生等学者在2005年提出的结构单元为双S形的左手介质，其工作频带从10～16GHz，相对带宽达到46％；Smith等人在2004年通过优化SRRs和细导线尺寸，设计出了单元损耗小于0.3dB的低损耗左手介质。然而遗憾的是这些结构单元在应用方面仍然存在较大的限制，因为为了能够激发出单元结构的负介电常数和负磁导率，这些单元结构对电场和磁场的方向都有严格的要求，导致这些异向介质单元只有在腔体结构的应用场合容易获得激发条件，而对于微波或毫米波平面电路器件的应用场合则不如异向介质传输线方便，然而这种单元结构的电尺寸比较大，有的甚至接近0.2个波长。传统的异向介质传输线和早期的异向介质在本质上是一致的。因为在传输线结构的等效电路中，通常能够得到串联的等效电感和并联的等效电容，它们其实代表了传输线的有效磁导率和有效介电常数，因此只要能用传输线实现负值的等效电感和负值的等效电容即可，而负的电感本质上就是电容，负的电容本质上就是电感，因此只要能在传输线的等效电路中实现串联的电容和并联的电感就可以实现左手传输线。但是要获得串联的等效电容和并联的等效电感并不容易，目前有些异向介质传输线为了获得它们甚至借助LTCC等昂贵的技术手段。Based on this situation, many scholars have carried out research on the design of new heterotropic media. So far, a variety of heterotropic media with new structures have been designed and manufactured, including transmission line structure metaisotropic media, structural units are Ω-shaped heterotropic media, open square ring structure metaisotropic media, structural units are S Type, double S-shaped anisotropic medium, structural unit is a helical anisotropic medium, anisotropic medium composed of CLSs and CLLs alternately, etc. Although new structures of heterotropic media emerge in endlessly, they can be classified into two categories: one is based on the improved or derived structure of Professor Smith's open square ring structure, and the other is based on the improved or derived structure of transmission line structure metaisotropic media. In particular, it should be pointed out that the transmission line structure metaisotropic medium is more commonly used in the form of a transmission line having the electromagnetic properties of the metaisotropic medium, so it is also called a metaisotropic medium transmission line. The initial anisotropic medium has narrow relative bandwidth (about 0.5%), large size (about 0.2 wavelength), and is not suitable for processing. After continuous improvement and derivation, the performance has been greatly improved. For example, the structural unit proposed by Chen Kangsheng and other scholars in 2005 is a double S-shaped left-handed medium. Its operating frequency band is from 10 to 16 GHz, and the relative bandwidth reaches 46%. A low-loss left-handed medium with unit loss less than 0.3dB is produced. Unfortunately, these structural units still have great limitations in application, because in order to be able to stimulate the negative permittivity and negative magnetic permeability of the unit structure, these unit structures have strict requirements on the direction of the electric field and magnetic field. As a result, these metaisotropic dielectric units are easy to obtain excitation conditions only in the application of cavity structure, but it is not as convenient as the anisotropic dielectric transmission line for the application of microwave or millimeter wave planar circuit devices. However, the electrical size of this unit structure is relatively large, Some are even close to 0.2 wavelengths. The traditional meta-media transmission line is essentially the same as the early meta-media. Because in the equivalent circuit of the transmission line structure, the equivalent inductance in series and the equivalent capacitance in parallel can usually be obtained, which actually represent the effective permeability and effective permittivity of the transmission line, so as long as the transmission line can be used to achieve a negative value The equivalent inductance and the equivalent capacitance of the negative value are enough, and the negative inductance is essentially the capacitance, and the negative capacitance is essentially the inductance, so as long as the series capacitance and the parallel inductance can be realized in the equivalent circuit of the transmission line Implement a left-handed transmission line. However, it is not easy to obtain the equivalent capacitance in series and the equivalent inductance in parallel. At present, some heterotropic transmission lines even use expensive technical means such as LTCC to obtain them.

发明内容Contents of the invention

为了解决现有的异向介质传输线电尺寸大、加工困难、成本高、带宽窄的问题，本发明提供了一种宽频带双通带异向介质传输线。In order to solve the problems of large electrical size, difficult processing, high cost and narrow bandwidth of the existing heterotropic dielectric transmission line, the present invention provides a broadband dual-passband heterotropic dielectric transmission line.

本发明的宽频带双通带异向介质传输线由至少一个异向介质单元构成，每个异向介质单元是由第一层介质板、第二层介质板和底层金属箔冲压在一起构成的；所述第一层介质板的上表面的中间沿Y方向刻蚀有一个金属条带，所述第一层介质板的上表面的中间沿X方向刻蚀有第一C形金属方环和第二C形金属方环，所述第一C形金属方环和所述第二C形金属方环以所述金属条带为对称轴对称设置，所述第一层介质板的下表面与第二层介质板的上表面相接触；所述第二层介质板的上表面的中间沿X方向刻蚀有第三C形金属方环和第四C形金属方环，所述第三C形金属方环位于所述第一C形金属方环的下方，且第三C形金属方环与第一C形金属方环的开口方向相反，所述第四C形金属方环位于所述第二C形金属方环的下方，且第四C形金属方环和第二C形金属方环的开口方向相反，所述第二层介质板的下表面与所述底层金属箔的上表面相接触；所述底层金属箔上设置有两个大小相同且相互连通的方形通孔，所述底层金属箔的两个方形通孔分别位于所述第三C形金属方环和第四C形金属方环的下方。当异向介质传输线由两个及两个以上异向介质单元构成时，多个异向介质单元沿金属条带的长度方向相互串联在一起，即多个异向介质单元沿Y方向相互串联在一起。The wide-band dual-passband heterotropic dielectric transmission line of the present invention is composed of at least one heterotropic dielectric unit, and each heterotropic dielectric unit is formed by punching together a first layer of dielectric board, a second layer of dielectric board and a bottom metal foil; A metal strip is etched in the middle of the upper surface of the first layer dielectric plate along the Y direction, and a first C-shaped metal square ring and a second metal square ring are etched in the middle of the upper surface of the first layer dielectric plate along the X direction. Two C-shaped metal square rings, the first C-shaped metal square ring and the second C-shaped metal square ring are symmetrically arranged with the metal strip as a symmetrical axis, and the lower surface of the first layer of dielectric board is connected to the second layer of dielectric board. The upper surface of the two-layer dielectric board is in contact; the middle of the upper surface of the second-layer dielectric board is etched with a third C-shaped metal square ring and a fourth C-shaped metal square ring along the X direction, and the third C-shaped metal square ring The metal square ring is located below the first C-shaped metal square ring, and the opening direction of the third C-shaped metal square ring is opposite to that of the first C-shaped metal square ring, and the fourth C-shaped metal square ring is located on the first C-shaped metal square ring. Below the two C-shaped metal square rings, and the opening directions of the fourth C-shaped metal square ring and the second C-shaped metal square ring are opposite, and the lower surface of the second layer of dielectric plate is in contact with the upper surface of the bottom metal foil. contact; the underlying metal foil is provided with two square through holes of the same size and connected to each other, and the two square through holes of the underlying metal foil are respectively located in the third C-shaped metal square ring and the fourth C-shaped metal ring Below the square ring. When the anisotropic dielectric transmission line is composed of two or more anisotropic dielectric units, multiple anisotropic dielectric units are connected in series along the length direction of the metal strip, that is, multiple anisotropic dielectric units are connected in series along the Y direction. Together.

本发明在空间结构上实现了开口谐振环结构，底层金属箔为非理想接地结构，是光子带隙结构的一种发展形式。本发明可以通过传统的PCB加工工艺来实现，完全适合大批量低成本生产。本发明的异向介质传输线具有双通频带特性，单元体积小、加工容易、成本低廉，且带宽宽、损耗小，其在微波毫米波电路器件上具有良好的应用前景。The invention realizes the split resonant ring structure in the spatial structure, and the bottom metal foil is a non-ideal grounding structure, which is a developed form of the photonic bandgap structure. The invention can be realized through traditional PCB processing technology, and is completely suitable for mass production at low cost. The anisotropic dielectric transmission line of the present invention has dual-pass frequency band characteristics, small unit volume, easy processing, low cost, wide bandwidth and low loss, and has good application prospects in microwave and millimeter wave circuit devices.

附图说明Description of drawings

图1是本发明的异向介质单元侧面结构示意图，图2是本发明的异向介质单元立体结构示意图，图3是本发明的第一层介质板1的结构示意图，图4是本发明的第二层介质板2的结构示意图，图5是本发明的底层金属箔3的结构示意图。Fig. 1 is a schematic diagram of the side structure of the anisotropic dielectric unit of the present invention, Fig. 2 is a schematic diagram of the three-dimensional structure of the anisotropic dielectric unit of the present invention, Fig. 3 is a schematic structural diagram of the first layerdielectric plate 1 of the present invention, and Fig. 4 is a schematic diagram of the structure of the anisotropic dielectric unit of the present invention A schematic diagram of the structure of the seconddielectric plate 2, and FIG. 5 is a schematic diagram of the structure of theunderlying metal foil 3 of the present invention.

具体实施方式Detailed ways

具体实施方式一：参见图1至图5，本具体实施方式的宽频带双通带异向介质传输线由多个异向介质单元构成，每个异向介质单元是由第一层介质板1、第二层介质板2和底层金属箔3冲压在一起构成的，如图2所示；如图3所示，所述第一层介质板1的上表面的中间沿Y方向刻蚀有一个金属条带1-1，所述第一层介质板1的上表面的中间沿X方向刻蚀有第一C形金属方环1-3和第二C形金属方环1-2，所述第一C形金属方环1-3和所述第二C形金属方环1-2以所述金属条带1-1为对称轴对称设置，所述第一层介质板1的下表面与第二层介质板2的上表面相接触；如图4所示，所述第二层介质板2的上表面的中间沿X方向刻蚀有第三C形金属方环2-1和第四C形金属方环2-2，所述第三C形金属方环2-1位于所述第一C形金属方环1-3的下方，且第三C形金属方环2-1与第一C形金属方环1-3的开口方向相反，所述第四C形金属方环2-2位于所述第二C形金属方环1-2的下方，且第四C形金属方环2-2和第二C形金属方环1-2的开口方向相反，所述第二层介质板2的下表面与所述底层金属箔3的上表面相接触；如图5所示，所述底层金属箔3上设置有两个大小相同且相互连通的方形通孔，所述底层金属箔3的两个方形通孔分别位于所述第三C形金属方环2-1和第四C形金属方环2-2的下方；多个异向介质单元沿金属条带1-1的长度方向相互串联在一起，即多个异向介质单元沿Y方向相互串联在一起。所述金属条带1-1为铜金属条带；所述第一C形金属方环1-3、第二C形金属方环1-2、第三C形金属方环2-1和第四C形金属方环2-2都为铜金属方环。所述第一C形金属方环1-3、第二C形金属方环1-2、第三C形金属方环2-1和第四C形金属方环2-2的大小相同。所述第一层介质板1、第二层介质板2和底层金属箔3分别被XY平面所截成的三个截面为三个大小相同的正方形。Specific embodiment one: Referring to Fig. 1 to Fig. 5, the wide-band dual-pass band heterotropic dielectric transmission line of this specific embodiment is composed of a plurality of heterotropic dielectric units, and each heterotropic dielectric unit is composed of a first layer ofdielectric board 1, The second layer ofdielectric plate 2 and theunderlying metal foil 3 are punched together, as shown in Figure 2; as shown in Figure 3, a metal layer is etched in the middle of the upper surface of the first layer ofdielectric plate 1 along the Y direction Strip 1-1, a first C-shaped metal square ring 1-3 and a second C-shaped metal square ring 1-2 are etched in the middle of the upper surface of the firstdielectric board 1 along the X direction, the first A C-shaped metal square ring 1-3 and the second C-shaped metal square ring 1-2 are symmetrically arranged with the metal strip 1-1 as a symmetric axis, and the lower surface of the first layer ofdielectric board 1 and the second The upper surfaces of the two-layerdielectric board 2 are in contact; as shown in Figure 4, the middle of the upper surface of the second-layerdielectric board 2 is etched with a third C-shaped metal square ring 2-1 and a fourth C-shaped metal ring 2-1 along the X direction. Shaped metal square ring 2-2, the third C-shaped metal square ring 2-1 is located below the first C-shaped metal square ring 1-3, and the third C-shaped metal square ring 2-1 and the first The opening direction of the C-shaped metal square ring 1-3 is opposite, and the fourth C-shaped metal square ring 2-2 is located below the second C-shaped metal square ring 1-2, and the fourth C-shaped metal square ring 2 -2 is opposite to the opening direction of the second C-shaped metal square ring 1-2, and the lower surface of the second layerdielectric plate 2 is in contact with the upper surface of thebottom metal foil 3; as shown in Figure 5, the Thebottom metal foil 3 is provided with two square through holes of the same size and connected to each other. The two square through holes of thebottom metal foil 3 are respectively located in the third C-shaped metal square ring 2-1 and the fourth C-shaped metal ring 2-1. Below the metal square ring 2-2; a plurality of anisotropic dielectric units are connected in series along the length direction of the metal strip 1-1, that is, a plurality of anisotropic dielectric units are connected in series along the Y direction. The metal strip 1-1 is a copper metal strip; the first C-shaped metal square ring 1-3, the second C-shaped metal square ring 1-2, the third C-shaped metal square ring 2-1 and the first C-shaped metal square ring Four C-shaped metal square rings 2-2 are all copper metal square rings. The sizes of the first C-shaped metal square ring 1-3, the second C-shaped metal square ring 1-2, the third C-shaped metal square ring 2-1 and the fourth C-shaped metal square ring 2-2 are the same. The three cross-sections of the firstdielectric board 1 , the seconddielectric board 2 and thebottom metal foil 3 respectively cut by the XY plane are three squares of the same size.

在本具体实施方式中，所述第一层介质板1采用相对介电常数是10.2的RT-Duroid介质板；所述第二层介质板2采用相对介电常数是2.54的Teflon(铁氟龙)介质板；所有C形金属方环的带宽d₁＝0.35～0.45mm、开口距离d₂＝0.70～0.80mm、X方向上的长度d₃＝3.10～3.20mm；所述第一层介质板1和第二层介质板2沿Z方向的厚度分别为0.585～0.685mm和0.49～0.59mm；如图5所示，所述底层金属箔3上相连通方形通孔的尺寸为d₄＝0.2～0.3mm、d₅＝2.45～2.55mm、d₆＝1.15～1.25mm。本具体实施方式的异向介质传输线具有两个通频带，其分别处于4.90～5.9GHz和6～10GHz，其相对带宽分别为18.3％和50％，在中心频率处其电尺寸为0.09。In this specific embodiment, the first layer ofdielectric board 1 adopts the RT-Duroid dielectric board whose relative permittivity is 10.2; ) medium plate; the bandwidth of all C-shaped metal square rings d₁ =0.35-0.45mm, the opening distance d₂ =0.70-0.80mm, the length in the X direction d₃ =3.10-3.20mm; the first layer ofmedium plate 1 and the thickness of the seconddielectric board 2 along the Z direction are 0.585-0.685 mm and 0.49-0.59 mm respectively; as shown in Figure 5, the size of the connected square through hole on thebottom metal foil 3 is d₄ =0.2 ~0.3 mm, d₅ =2.45~2.55 mm, d₆ =1.15~1.25 mm. The heterotropic dielectric transmission line of this specific embodiment has two passbands, which are respectively at 4.90-5.9GHz and 6-10GHz, and their relative bandwidths are respectively 18.3% and 50%, and the electrical dimension at the center frequency is 0.09.

具体实施方式二：本具体实施方式与具体实施方式一的不同点是：如图3所示，所述第一C形金属方环1-3和第二C形金属方环1-2的开口背向所述金属条带1-1；如图4所示，所述第三C形金属方环2-1和第四C形金属方环2-2的开口相对。其他组成和连接关系与具体实施方式一相同。Specific embodiment two: the difference between this specific embodiment and specific embodiment one is: as shown in Figure 3, the openings of the first C-shaped metal square ring 1-3 and the second C-shaped metal square ring 1-2 It faces away from the metal strip 1-1; as shown in FIG. 4 , the openings of the third C-shaped metal square ring 2-1 and the fourth C-shaped metal square ring 2-2 are opposite. Other components and connections are the same as those in the first embodiment.

Claims (7)

1, a kind of wide-frequency-band double-way-band incongruous medium transmission wire, it is characterized in that described anisotropic media transmission line is made of at least one anisotropic media unit, each anisotropic media unit is made of ground floor dielectric-slab (1), second layer dielectric-slab (2) and underlying metal paper tinsel (3) punching press together; The centre of the upper surface of described ground floor dielectric-slab (1) is etched with a metal band (1-1) along the Y direction, the centre of the upper surface of described ground floor dielectric-slab (1) is etched with a C shape metal Fang Huan (1-3) and the 2nd C shape metal Fang Huan (1-2) along directions X, a described C shape metal Fang Huan (1-3) and described the 2nd C shape metal Fang Huan (1-2) are that symmetry axis is symmetrical arranged with described metal band (1-1), and the lower surface of described ground floor dielectric-slab (1) contacts with the upper surface of second layer dielectric-slab (2); The centre of the upper surface of described second layer dielectric-slab (2) is etched with the 3rd C shape metal Fang Huan (2-1) and the 4th C shape metal Fang Huan (2-2) along directions X, described the 3rd C shape metal Fang Huan (2-1) is positioned at the below of a described C shape metal Fang Huan (1-3), and the 3rd C shape metal Fang Huan (2-1) is opposite with the opening direction of a C shape metal Fang Huan (1-3), described the 4th C shape metal Fang Huan (2-2) is positioned at the below of described the 2nd C shape metal Fang Huan (1-2), and the opening direction of the 4th C shape metal Fang Huan (2-2) and the 2nd C shape metal Fang Huan (1-2) is opposite, and the lower surface of described second layer dielectric-slab (2) contacts with the upper surface of described underlying metal paper tinsel (3); Described underlying metal paper tinsel (3) is provided with the square through hole that two sizes are identical and be interconnected, and two square through holes of described underlying metal paper tinsel (3) lay respectively at the below of described the 3rd C shape metal Fang Huan (2-1) and the 4th C shape metal Fang Huan (2-2).

2, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1, it is characterized in that a plurality of anisotropic medias unit is cascaded mutually along the length direction of metal band (1-1) when the anisotropic media transmission line is made of two and two above anisotropic media unit.

3, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1 is characterized in that described metal band (1-1) is the copper metal band.

4, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1 is characterized in that a described C shape metal Fang Huan (1-3), the 2nd C shape metal Fang Huan (1-2), the 3rd C shape metal Fang Huan (2-1) and the 4th C shape metal Fang Huan (2-2) are copper metal Fang Huan.

5, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1 is characterized in that a described C shape metal Fang Huan (1-3), the 2nd C shape metal Fang Huan (1-2), the 3rd C shape metal Fang Huan (2-1) are big or small identical with the 4th C shape metal Fang Huan's (2-2).

6, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1 is characterized in that three cross sections that described ground floor dielectric-slab (1), second layer dielectric-slab (2) and underlying metal paper tinsel (3) are cut into by the XY plane respectively are three squares that size is identical.

7, a kind of wide-frequency-band double-way-band incongruous medium transmission wire according to claim 1 is characterized in that the described dorsad metal band of opening (1-1) of a described C shape metal Fang Huan (1-3) and the 2nd C shape metal Fang Huan (1-2); Described the 3rd C shape metal Fang Huan (2-1) is relative with the opening of the 4th C shape metal Fang Huan (2-2).

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