WO2014121568A1

WO2014121568A1 - Low-loss flat transmission line

Info

Publication number: WO2014121568A1
Application number: PCT/CN2013/076224
Authority: WO
Inventors: 孙劲; 何其娟; 李立忠
Original assignee: 上海安费诺永亿通讯电子有限公司
Priority date: 2013-02-07
Filing date: 2013-05-24
Publication date: 2014-08-14
Also published as: CN103117440A; CN103117440B

Abstract

A low-loss flat transmission line comprises a plurality of solder mask layers, a plurality of bonding layers, a plurality of dielectric layers, and a plurality of connecting layers. The solder mask layers are used for preventing oxidization of a metal area and contact between a shielded transmission line structure and a peripheral good conductor, the bonding layers are used for physical vertical bonding, and the dielectric layers are used in an energy transmission area. A first signal island and a first gap surrounding the first signal island are arranged on at least one end of a first connecting layer, and at least one signal line via hole is arranged on the first signal island. A signal transition area and a plurality of gaps on the signal transition area are arranged on at least one end of a second connecting layer. A second signal island and a second gap surrounding the second signal island are arranged on at least one end of a third connecting layer. The signal line via hole of the first connecting layer is communicated with signals of the first signal island, the second signal island, and the signal transition area, and the signal transition area is connected with a signal line. By introducing the connecting structure of the present invention, L1 and C1 are optimized, which greatly reduces the impact of discontinuity, and reduces an insertion loss of the transmission line structure to the greatest extent.

Description

Low loss flat transmission line

The present invention relates to a communication antenna, and more particularly to a low loss flat transmission line associated with a communication antenna. Background technique

An antenna is a device that receives and transmits signals using frequency characteristics. In recent years, the design and performance of mobile terminal antennas for wireless communication have increasingly affected the development direction of mobile communications. In particular, portable mobile terminals such as mobile phones, PDA (Personal Digital Assistance), MP3/MP4. Several main indicators of antenna design are: With proper multi-frequency resonance, the antenna realizes both signal propagation and energy radiation based on the resonance of a certain frequency. If an antenna can resonate at multiple frequencies, the antenna will be able to operate at multiple frequencies.

In recent years, more and more wireless terminals have adopted a low profile structure design. That is, the thickness of the terminal is getting smaller and smaller, and "thin" is the goal pursued by many mobile phones. In order to achieve this goal, many mobile phones use a discrete PCB board design, that is, two PCB boards are respectively located at the two ends of the mobile phone. You can use the motherboard to refer to one of them. There are usually RF modules on the top, and the small board refers to another piece. There are some connection and matching circuits on the top. The top of the small board is usually an antenna. A small diameter coaxial cable connects the small board to the motherboard to direct RF signals from the motherboard to the board. The smaller the diameter of the coaxial line, the greater the loss per unit length. However, because the space integration of mobile phones is getting higher and higher, it is required to use coaxial wires as small as possible. This is exactly the contradiction between reducing losses. How to reduce the space occupied by this coaxial cable as much as possible without increasing the loss is a challenge we face. In recent years, the use of microstrip lines to implement transmission lines is a possible option. However, the microstrip line is a semi-open structure for the signal, and the shielding of the signal is problematic, and signal interference is easily generated. A transmission line implemented with a stripline structure is a good choice. The signal line is located in the middle of the two layers of ground, and the signal is well shielded and is not prone to interference. On the other hand, for RF performance and manufacturing stability, the width of the signal line is generally not less than 0.1 mm. This has certain requirements on the thickness of the strip line. It is necessary to design a via hole for connecting the RF connector and the strip line. Usually, the via hole here is a blind hole connecting the signal line and the surface conductor, that is, the via hole only passes through the thickness of the partial strip line. The thicker the strip line is, the more difficult it is to make the blind hole, which will seriously affect the yield of the product. There are certain restrictions on the fabrication of blind holes. Assuming that R is the radius of the blind hole and h is the height of the blind hole, then R/h must satisfy certain conditions. In order to achieve stable and reliable conduction, R/h must be greater than 0.9. But because R can't be arbitrarily large, for example, it is limited by the size space. Then at this time, h must not be too big, That is to say, the height of the hole is limited, for example, h does not exceed 50 microns. Moreover, the production of holes requires the use of a laser machine, which is costly. At the same time, since the connector of SMT (Surface Mounted Technology) is connected at both ends of the transmission line, although the connector of the SMT is 50 ohm impedance, the characteristic impedance of the transmission line is also 50 ohms, and the structure of the connection line connecting the transmission line is still structurally The discontinuity causes the characteristic impedance to deviate from 50 ohms. This phenomenon is particularly noticeable in high frequency bands, such as above 3Ghz, resulting in transmission line insertion loss becoming worse in the high frequency band.

That is to say, the discontinuity of the connection portion connecting the transmission line occurs, and a defect in which the characteristic impedance deviates from 50 ohms occurs.

Summary of the invention

The object of the present invention is to provide a low-loss flat transmission line, which is especially applicable to a high frequency band, so as to solve the discontinuity of the connecting line connecting the transmission line in the prior art, and the occurrence of a characteristic impedance deviation of 50 ohms occurs, thereby causing the transmission line. The insertion loss is a technical problem that becomes worse in the high frequency band. A low-loss flat transmission line comprising a plurality of solder resist layers for preventing oxidation of a metal region and shielding the transmission line structure from contact with surrounding good conductors, a plurality of bonding layers for physically upper and lower bonding, and an energy transfer region a plurality of dielectric layers, a plurality of connecting layers, the connecting layer comprising at least a first connecting layer, a second connecting layer and a third connecting layer, wherein

a signal island 1 and a first slot surrounding the signal island 1 are disposed on at least one end of the first connection layer, and at least a signal line via hole is disposed on the signal island, and the signal island 1 and the first slot are used to adjust the transmission line. a capacitive characteristic,

a signal transition region and a plurality of slits disposed on the signal transition region are disposed on at least one end of the second connection layer, and corresponding signal line via holes are disposed at corresponding positions of the signal transition region, and the signal transition region and a plurality of slots thereof are used for Adjust the inductance characteristics of the transmission line,

a signal island 2 and a second slot surrounding the signal island 2 are disposed on at least one end of the third connection layer, and corresponding signal line vias are disposed at corresponding positions of the signal island 2, and the signal island 2 and the second slot are used to adjust the transmission line. First capacitance characteristic,

The signal line via of the first connection layer connects the signals of the signal island 1, the signal island 2 and the signal transition region, and the signal transition region is connected to the signal line.

Preferably, three slits are arranged on the signal transition region: a third slit, a fourth slit and a fifth slit, and the third slit, the fourth slit and the fifth slit adjust the inductance characteristics of the transmission line.

Preferably, the third slit, the fourth slit and the fifth slit are juxtaposed, respectively, the third slit and the fifth slit The slit opening is in the same direction as the slit opening of the fourth slit, and the fourth slit is located between the third slit and the fifth slit.

Preferably, the second slot may be arranged in a ring shape around the signal island 2, or may be arranged in a semi-enclosed shape around the signal island 2, the first slot may be arranged in a ring shape around the signal island, or may be semi-enclosed around the signal island. type.

Preferably, the shape of the signal island 2 and the second slit is substantially the same as the shape formed by the signal island 1 and the first slit.

Preferably, the plurality of solder resist layers comprise a top layer and a bottom layer, the top layer comprises a non-conductive region of the shield transmission line structure, and a plurality of joint seams for the position of the joint head soldering disc are disposed on the non-conductive region, and one of the joint seams is physically connected Connector signal line conductor.

Preferably, the first connection layer is further provided with a plurality of series of via holes and periodic via holes. The series of via holes and the series of via holes may be symmetric about the center line, and the series of via holes may be parallel to the center line and mirrored to the center line. On one side, the repetition period is the center positional spacing between the vias.

Preferably, the bonding layer is two layers, one of which is located below the top layer and the other of which is located above the bottom layer. Preferably, the dielectric layer is two layers, one of which is located between the first connection layer and the second connection layer, and is located between the second connection layer and the third connection layer.

Preferably, the connector is a 50 ohm connector.

Compared with the prior art, the present invention has the following technical advantages:

According to the traditional transmission line theory, the periodic L0, CO is directly connected to the 50 ohm connector, and the discontinuity introduced at the high frequency loss is large. The connection structure of the present invention is introduced, and LI, C1 are optimized, the influence of discontinuity is greatly reduced, and the insertion loss of the transmission line structure is minimized. It has been proven that the transmission line structure processed in this way reduces the return loss at 6 GHz by 5 dB, and the insertion loss at 6 GHz is 20% lower than that of the public product.

DRAWINGS

1 is an assembled view of an embodiment of a low loss flat transmission line of the present invention;

2 is a diagram showing an example of a top layer of a low-loss flat transmission line of the present invention;

3 is a diagram showing an example of implementation of a first connection layer of the present invention;

4 is a diagram showing an example of implementation of a second connection layer of the present invention;

Figure 5 is a diagram showing an example of the implementation of the third connection layer of the present invention;

Figure 6 is a diagram showing an example of the implementation of the bottom layer of the present invention. detailed description

The invention will be specifically described below with reference to the accompanying drawings.

Please refer to FIG. 1 to FIG. 6 , a low-loss flat transmission line, including a plurality of solder resist layers for preventing oxidation of the metal region and shielding the transmission line structure from contacting the surrounding good conductor, and a plurality of bonding for physically upper and lower bonding. Layer, several dielectric layers for the energy transfer region, and several tie layers.

The plurality of solder resist layers include a top layer 11 and a bottom layer 19. The top layer 11 and the bottom layer 19 are solder masks that prevent oxidation of the metal regions and shield the transmission line structure from contact with surrounding good conductors.

The bonding layer is two layers, one of which is located below the top layer and the other of which is located above the bottom layer. That is, the intermediate layer 12 and the intermediate layer 18 are adhesive layers, which mainly function as physical upper and lower adhesion. The intermediate layer 12 and the intermediate layer 18 have a certain thickness, and depending on the characteristics of the bonding material, the transmission characteristics of the entire transmission line structure are affected correspondingly, in order to achieve optimal transmission performance and reduce loss, the connection structure and the signal line need to be optimized. .

The dielectric layer is a two layer, one of which is located between the first connection layer and the second connection layer, and two of which is located between the second connection layer and the third connection layer. The dielectric layer is the energy transfer area. The characteristic parameters of the dielectric layer material such as thickness and relative dielectric loss have a significant impact on the overall transmission line structure, and the less lossy dielectric material is the first choice for industrial application production. The intermediate layer 14 and the intermediate layer 16 are dielectric layers.

That is, a transmission line structure as shown in FIG. 1 includes a top layer 11, an intermediate layer 12-18, a bottom layer 19 and a connection mechanism, the intermediate layer 13 is connected to a 50 ohm joint, and the intermediate layer 13 (ie, the first connection) The layer), the intermediate layer 15 (ie, the second connecting layer), and the intermediate layer 17 (ie, the third connecting layer) are respectively provided with signal lines and connection mechanisms. The intermediate layer 13 and the intermediate layer 17 include a certain number and a specific size of the via holes 21 connected to the via holes 28, and the via holes 21 to the via holes 28 penetrate the intermediate layer 13 and the intermediate layer 17 has a central symmetric structure. The intermediate layer 13 and the intermediate layer 15 are provided with signal lines which together with the intermediate layer 13 and the intermediate layer 17 constitute a main structure of the transmission line structure.

The top layer includes a non-conductive area of the shielded transmission line structure, and a plurality of connection slits for the position of the bonding pad of the bonding head are disposed on the non-conductive area, and one of the connecting slits is physically connected to the connector signal line conductor. Please refer to FIG. 2, which shows the specific structure of the top layer 11, and the oblique line area shown in 101 is a non-conductive area, an insulating material, and a shielded transmission line structure. The slits 102 to 105 are 50 ohm head pad positions, and the slits 102, 103 and 105 are exposed at positions 302 of the intermediate layer 13 to be electrically connected to each other. The slit 104 is exposed at the 304 area of the intermediate layer 13. A signal line conductor physically connected to a 50 ohm connector.

Signal island-304 and surrounding signal are disposed on at least one end of the first connection layer 13 (ie, the intermediate layer 13) A first slot 303 of the island 1 and at least one signal line via 29 are disposed on the signal island 304. The signal island 304 and the first slot 303 are used to adjust the first capacitance characteristic of the transmission line. Referring to FIG. 7, which is an equivalent circuit of the connection layer, the shape of the signal island 304 is variable, and the first slit 303 surrounding the signal island 1 can also be varied. The shape of the signal island is variable, and the sealing property of the slit can be extended to a half envelope according to the actual situation, such as opening along the center line A to the edge of the transmission line. That is to say, the shape and size of the signal island 304 and the first slit 303 are related to the characteristics of the first capacitor, and the specific shape and size are also related to the materials used by the signal island 304 and the first slit 303, and only need to go through After many experiments, you can get the shape and size that suits the material.

Referring to Figure 3, the intermediate layer 13 is shown, including a copper-clad area 302, a series of vias 21 to 28, a signal line island 304, a signal line via 29, and a gap 303 surrounding the signal island. The area 301 indicates the distance between the intermediate face and the outer edge of the transmission line and the intermediate face 13. The series of vias 21, 22 and the vias 23, 24 are vertically symmetrical about the centerline A. The vias 25, 26 are parallel to the centerline A and mirrored to the other side of the centerline. In addition, the transmission line structure also has periodic vias 27, 28 having a repeating period of the center-to-center spacing of the vias 27 to the vias 28 and mirroring the centerline A to the other side. Via 27 to via 28 The repeat period is much less than a quarter of the highest frequency of operation of the transmission line structure. Signal Lines The vias 29 are different from the series of vias. The number of signal line vias 29 is much less than the series of vias. The position of the signal line vias needs to be optimized. As can be seen from Fig. 3, a signal island-304 and a first slit 303 surrounding the signal island 1 are disposed on both ends of the intermediate layer 13, respectively, which is an implementation.

A signal transition region 502 and a plurality of slits disposed on the signal transition region 502 are disposed on at least one end of the second connection layer 15 (ie, the intermediate layer 15), and corresponding signal line vias 29 are disposed at corresponding positions of the signal transition region, and the signal is Transition region 502 inductance characteristics. Referring to FIG. 7, in the second connection layer 15, the signal transition region 502 and the plurality of slits disposed on the signal transition region 502 can be equivalent to the first inductor L1. The shape of the signal transition region 50 is variable, and the shape and size of the slits can also vary. Only after a lot of experiments, you can get the shape and size that suits the material.

A signal island 703 and a second slot 704 surrounding the signal island 703 are disposed on at least one end of the third connection layer 17, and corresponding signal line vias 29 are disposed at corresponding positions of the signal islands 703, and the signal islands 703 and The second slot 704 is used to adjust the first capacitor C1.

The signal line via 29 of the first connection layer connects the signals of the signal island one 304, the signal island two 703, and the signal transition region 502, and the signal transition region 502 is connected to the signal line 506.

2 to 5 illustrate the connection structure. The connection structure includes the signal islands 304 and the middle layer 13 A slit 303 around the signal island, signal transition regions 502 to 505 of the intermediate layer 15, and a signal island 703 shown in the intermediate layer 17 and an irregular slit structure 704 surrounding the signal island 2. The slit 303 is for adjusting the first capacitance C1. That is, the slit 303 and the slit 704 collectively adjust the first capacitor C1. Cl as shown in FIG.

The signal transition region 502 is an irregular smooth region, and the signal line via 29 is connected to the signal island one 304, the signal island two 703 signal and the signal transition region 502. Signal transition region 502 is coupled to signal line 506. The gap 503, 504, 505 is used to adjust the electrical parameters of the signal transition region, that is, the inductance characteristic Ll of the transmission line. The signal line 506 is a uniform-width hook conductor, and its distributed equivalent inductance and capacitance are L0 and C0, respectively. The equivalent circuit is shown in Figure 7.

According to the conventional transmission line theory, the periodic L0, CO is directly connected to the 50 ohm connector, and the discontinuity introduced at the high frequency loss is large. The connection structure of the present invention is introduced, and LI, C1 are optimized to greatly reduce the influence of discontinuity, and the insertion loss of the transmission line structure is minimized. It has been proven that the return loss of the transmission line structure processed in this way is reduced by 5 dB at 6 GHz, and the insertion loss at 6 GHz is reduced by 20% compared to the public product.

501 in Fig. 4 indicates a non-metallic region on the intermediate surface 15. In Fig. 5, 701 denotes a non-metal region of the intermediate surface 17, and a hatched portion indicated by 702 is a metal region. Figure 6 shows the underlying structure diagram. The shaded area is a non-conductive area, shielding the transmission line structure. The process of implementing the transmission line is not limited. The embodiment of the invention is a circuit board method, which adopts a lamination, photolithography etching process.

It should also be noted that the material of the intermediate surface 14, 16 may be a hard plate or a soft plate.

The preferred embodiments of the invention are only intended to aid in the description of the invention. The preferred embodiments are not intended to be exhaustive or to limit the details. Obviously, many modifications and variations are possible in light of the teachings herein. The present invention has been chosen and described in detail to explain the principles and embodiments of the present invention, so that those skilled in the art can. The invention is to be limited only by the scope of the appended claims and the appended claims.

Claims

claims

1. A low-loss flat transmission line, characterized by including a number of solder resist layers used to prevent oxidation of the metal area and shielding the transmission line structure from contact with surrounding good conductors, a number of adhesive layers used for physical upper and lower bonding, Several dielectric layers and several connection layers used in the energy transmission area, the connection layers include at least a first connection layer, a second connection layer and a third connection layer, wherein,

A signal island one and a first gap surrounding the signal island one are provided on at least one end of the first connection layer, and at least signal line vias are provided on the signal island one. The signal island one and the first gap are used to adjust the third of the transmission line. A capacitance characteristic,

A signal transition region and a number of gaps provided on the signal transition region are provided on at least one end of the second connection layer, and corresponding signal line vias are provided at corresponding positions of the signal transition region. The signal transition region and its several gaps are used for Adjust the inductance characteristics of the transmission line,

Signal island two and a second gap surrounding signal island two are provided on at least one end of the third connection layer, and corresponding signal line vias are provided at corresponding positions of signal island two. Signal island two and the second gap are used to adjust the transmission line The first capacitance characteristic,

The signal line via hole of the first connection layer connects the signal island one, the signal island two and the signal transition area, and the signal transition area is connected to the signal line.

2. The low-loss flat transmission line as claimed in claim 1, characterized in that three slits are provided in the signal transition area: the third slit, the fourth slit and the fifth slit, and the third slit, the fourth slit and the fifth slit are adjusted. Inductive properties of transmission lines.

3. The low-loss flat transmission line as claimed in claim 2, wherein the third slit, the fourth slit and the fifth slit are respectively juxtaposed, the openings of the third slit and the fifth slit are in the same direction, and the openings of the third slit and the fifth slit are in the same direction. The openings of the slits are opposite, and the fourth slit is located between the third slit and the fifth slit.

4. The low-loss flat transmission line as claimed in claim 1, wherein the second gap can be arranged in a ring shape around the second signal island, or can be arranged in a semi-encircled shape around the signal island two, and the first gap can be arranged in a semi-envelope shape around the signal island one. It can be set up in a ring shape, or it can be set up in a semi-encircled shape around the signal island.

5. The low-loss flat transmission line as claimed in claim 4, wherein the shape formed by the second signal island and the second gap is substantially consistent with the shape formed by the first signal island and the first gap.

6. The low-loss flat transmission line of claim 1, wherein a plurality of solder resist layers include a top layer and a bottom layer, the top layer includes a non-conductive area that shields the transmission line structure, and a plurality of solder resist layers are provided on the non-conductive area for connector welding. The connecting seams at the disc position, and one of the connecting seams physically connects the connector signal line conductor.

7. The low-loss flat transmission line as claimed in claim 1, wherein a number of series of vias and periodic vias are also provided on the first connection layer, and the series of vias and the series of vias can be symmetrical up and down with respect to the center line. The via holes can be parallel to the center line and mirrored to the other side of the center line, and the repeating period is the center position spacing between the via holes.

8. The low-loss flat transmission line as claimed in claim 6, characterized in that the adhesive layer is composed of two layers, one of which is located below the top layer, and the other two is located above the bottom layer.

9. The low-loss flat transmission line as claimed in claim 8, wherein the dielectric layer is two layers, one of which is located between the first connection layer and the second connection layer, and the other of which is located between the second connection layer and the third connection layer. between layers.

10. The low-loss flat transmission line as claimed in claim 1, wherein the connector is a 50-ohm connector.