CN103117440B - Low-loss flat transmission line - Google Patents

Abstract

A low-loss flat transmission line, including several solder resist layers used to prevent oxidation of the metal area and shield the transmission line structure from contacting with the surrounding good conductors, several adhesive layers for physical up and down bonding, and a number of bonding layers for the energy transmission area Several dielectric layers and several connection layers. At least one end of the first connection layer is provided with a signal island 1 and a first slit surrounding the signal island 1, and at least a signal line via is provided on the signal island 1, and at least one end of the second connection layer is provided with a signal transition area and in the signal island 1. Several gaps are set on the transition area, signal island 2 and the second gap around signal island 2 are set on at least one end of the third connection layer, and signal line vias in the first connection layer are connected to signal island 1, signal island 2 and signal transition The signal of the area, the signal transition area is connected with the signal line. The connection structure of the present invention is introduced, L1 and C1 are optimized, the influence of discontinuity is greatly reduced, and the insertion loss of the transmission line structure is reduced to the greatest extent.

Description

A low-loss flat transmission line

technical field

The invention relates to a communication antenna, in particular to a low-loss flat transmission line related to the communication antenna.

Background technique

An antenna is a device that uses frequency characteristics to receive and transmit signals. In recent years, the design and performance of mobile terminal antennas for wireless communication have more and more influence on the development direction of mobile communication. Especially portable mobile terminals such as mobile phones, PDA (Personal Digital Assistance), MP3/MP4. The main indicators of the antenna design are: there is a suitable multi-frequency resonance, and the antenna realizes signal propagation and energy radiation based on the resonance of a certain frequency. If an antenna can resonate at multiple frequencies, then the antenna will work at multiple frequencies.

In recent years, more and more wireless terminals adopt low-profile structural design. That is to say, the thickness of the terminal is getting smaller and smaller, and "thinness" is the goal pursued by many mobile phones. In order to achieve this goal, many mobile phones adopt a discrete PCB board design, that is, two PCB boards are located at both ends of the mobile phone, and the main board can be used to refer to one of them, which usually has a radio frequency module on it, and the small board refers to the other. , with some simple connections and matching circuits above. Above the small board is usually the antenna. A coaxial cable with a very thin diameter connects the small board and the main board, and is used to guide the radio frequency signal from the main board to the small board. The smaller the diameter of the coaxial line, the greater the loss per unit length. However, because the spatial integration of mobile phones is getting higher and higher, it is required to use a coaxial cable with a diameter as small as possible. This is exactly in contradiction with reducing loss. How to reduce the space occupied by this section of coaxial cable as much as possible without increasing loss is the challenge we face. In recent years, implementing transmission lines with microstrip 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, which is prone to signal interference. 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, the signal is well shielded, and it is not easy to cause interference. On the other hand, for the sake of radio frequency 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 stripline. Connecting the RF connector and the stripline requires the design of vias. Usually, the vias here are blind holes connecting the signal line and the surface conductor, that is, the vias only pass through part of the thickness of the stripline. The thicker the stripline is, the more difficult it is to make blind holes, which will seriously affect the yield of the product. There are certain restrictions on the manufacture 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 meet certain conditions. In order to achieve stable and reliable conduction, R/h must be greater than 0.9. But because R cannot be arbitrarily large, for example, it is limited by the size space. Then at this time, h must not be too large, that is to say, the height of the hole is limited, for example, h does not exceed 50 microns. Moreover, a laser machine is needed to make the hole, which is costly. At the same time, since the SMT (Surface Mounted Technology) connector is connected to both ends of the transmission line, although the SMT connector has an impedance of 50 ohms, the characteristic impedance of the transmission line is also 50 ohms, and there is still a structural problem at the part where the connector connects to the transmission line. discontinuity, which causes the characteristic impedance to deviate from 50 ohms. This phenomenon is particularly obvious in high frequency bands, such as above 3Ghz, which causes the insertion loss of the transmission line to deteriorate in the high frequency band.

That is to say, there is a discontinuity at the part where the connector is connected to the transmission line, and a defect that the characteristic impedance deviates from 50 ohms occurs.

Contents of the invention

The purpose of the present invention is to provide a low-loss flat transmission line, especially suitable for high-frequency bands, to solve the discontinuity of the connector connecting the transmission line in the prior art, and the defect that the characteristic impedance deviates from 50 ohms occurs, resulting in transmission line A technical problem where insertion loss becomes worse at high frequencies. A low-loss flat transmission line, including several solder resist layers used to prevent oxidation of the metal area and shield the transmission line structure in contact with the surrounding good conductors, several adhesive layers for physical up and down bonding, and for the energy transmission area Several dielectric layers and several connection layers, the connection layers at least include a first connection layer, a second connection layer and a third connection layer, wherein,

At least one end of the first connection layer is provided with a signal island 1 and a first slit surrounding the signal island 1, and at least a signal line via is provided on the signal island 1, and the signal island 1 and the first slit are used to adjust the first slit of the transmission line. A capacitive characteristic,

At least one end of the second connection layer is provided with a signal transition area and several slits provided on the signal transition area, and corresponding signal line vias are provided at corresponding positions of the signal transition area, and the signal transition area and its several slits are used for adjust the inductance characteristics of the transmission line,

At least one end of the third connection layer is provided with a signal island 2 and a second slit surrounding the signal island 2, and a corresponding signal line via is provided at a corresponding position of the signal island 2, and the signal island 2 and the second slit are used to adjust the transmission line. The first capacitance characteristic,

The signal line vias in the first connection layer are connected to the signals of the signal island 1, the signal island 2 and the signal transition area, and the signal transition area is connected to the signal line.

Preferably, three slots are set on the signal transition area: the third slot, the fourth slot and the fifth slot, and the third slot, the fourth slot and the fifth slot adjust the inductance characteristic of the transmission line.

Preferably, the third slit, the fourth slit and the fifth slit are juxtaposed respectively, the slit openings of the third slit and the fifth slit are in the same direction, and are opposite to the slit opening of the fourth slit, and the fourth slit is located between the third slit and the fifth slit. between the fifth gap.

Preferably, the second slit can be arranged in a ring around the second signal island, or can be arranged in a semi-enclosed shape around the second signal island, and the first slit can be arranged in a ring around the first signal island, or can be arranged in a semi-enclosed shape around the first signal island type.

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

Preferably, several solder resist layers include a top layer and a bottom layer, the top layer includes a non-conductive area of the shielded transmission line structure, and several connection seams for the position of the soldering pad of the connector are arranged on the non-conduction area, and one of the connection seams is physically connected Connector signal line conductor.

Preferably, several series of via holes and periodic via holes are also arranged on the first connection layer. The series of via holes and the series of via holes can be symmetrical up and down about the center line, and the series of via holes can be parallel to the center line and mirrored to the center line. On the one hand, the repetition period is the distance between the centers of the via holes.

Preferably, the adhesive layer has two layers, one of which is located below the top layer, and the other is located above the bottom layer.

Preferably, the medium layer is two layers, one of which is located between the first connection layer and the second connection layer, and the other 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, if the periodic L0 and C0 are directly connected to the 50 ohm connector, the discontinuity introduced by the high-frequency loss is very large. Introduce the connection structure of the present invention, optimize L1, C1, greatly reduce the impact of discontinuity, and minimize the insertion loss of the transmission line structure. Facts have proved that the return loss of the transmission line structure processed in this way is reduced by 5dB at 6GHz, and the insertion loss at 6GHz is 20% lower than that of the public product.

Description of drawings

Fig. 1 is an assembly diagram of an embodiment of the low-loss flat transmission line of the present invention;

Fig. 2 is an example diagram of an implementation of the top layer of the low-loss flat transmission line of the present invention;

Fig. 3 is the implementation example diagram of the first connection layer of the present invention;

Fig. 4 is the implementation example diagram of the second connection layer of the present invention;

Fig. 5 is the implementation example diagram of the third connection layer of the present invention;

Fig. 6 is an implementation example diagram of the bottom layer of the present invention;

7 is an equivalent circuit connection diagram of the distributed equivalent inductance and capacitance of the signal line of the connection structure of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

Please refer to Figures 1 to 6, a low-loss flat transmission line, including several solder resist layers used to prevent oxidation of the metal area and shield the transmission line structure from contacting the surrounding good conductors, several bonding layers for physically bonding the top and bottom layer, several dielectric layers and several connection layers for the energy transfer area.

Several solder resist layers include a top layer 11 and a bottom layer 19 . The top layer 11 and the bottom layer 19 are solder resist layers, which prevent oxidation of metal areas and shield the transmission line structure from contact with surrounding good conductors.

The bonding layer has two layers, one of which is located below the top layer, and the other is located above the bottom layer. That is, the middle layer 12 and the middle layer 18 are adhesive layers, and the main function is the physical upper-lower adhesion. The middle layer 12 and the middle layer 18 have a certain thickness, which will affect the transmission characteristics of the entire transmission line structure according to the different characteristics of the bonding materials. In order to achieve the best transmission performance and reduce the loss, the connection structure and the signal line need to be optimized. .

The medium layer is two layers, one of which is located between the first connection layer and the second connection layer, and the other is located between the second connection layer and the third connection layer. The medium layer is the energy transmission area. The characteristic parameters of the dielectric layer material, such as thickness and relative dielectric loss, have a great influence on the entire transmission line structure, and the dielectric material with smaller loss is the first choice for industrial application production. The middle layer 14 and the middle layer 16 are dielectric layers.

That is to say, a transmission line structure as shown in FIG. 1 includes a top layer 11, middle layers 12-18, a bottom layer 19 and a connecting mechanism. layer), the middle layer 15 (ie the second connection layer), and the middle layer 17 (ie the third connection layer) are respectively provided with signal lines and connection mechanisms. Wherein, the intermediate layer 13 and the intermediate layer 17 include a certain number and specific size vias 21 to 28 connected to each other, and the vias 21 to 28 run through the intermediate layer 13, and the intermediate layer 17 has a centrosymmetric structure. The intermediate layer 13 and the intermediate layer 15 are provided with signal lines, and the signal lines together with the intermediate layer 13 and the intermediate layer 17 constitute the main structure of the transmission line structure.

The top layer includes a non-conductive area that shields the transmission line structure, and several connection seams are provided on the non-conduction area for the positions of the pads of the connector, and one of the connection seams physically connects the conductor of the signal line of the connector. Please refer to FIG. 2 , which shows the specific structure diagram of the top layer 11 , and the oblique area indicated by 101 is a non-conductive area, an insulating material, and a shielded transmission line structure. The seams 102 to 105 are the positions of the 50 ohm connector pads, and the exposed positions of the seams 102, 103 and 105 are located in the area 302 of the middle layer 13, and are electrically connected to each other. The slit 104 exposed position is located in the 304 area of the middle layer 13. Physically connect the signal line conductors of the 50 ohm connector.

At least one end of the first connection layer 13 (that is, the intermediate layer 13) is provided with a signal island 1 304 and a first slit 303 surrounding the signal island 1, and at least one signal line via hole 29 is provided on the signal island 1 304, and the signal island 1 304 and the first slit 303 are used to adjust the first capacitance characteristic of the transmission line. Please refer to FIG. 7 , which is an equivalent circuit of the connection layer. The shape of the signal island 1 304 can be changed, and the first gap 303 around the signal island 1 can also be changed. The shape of the signal island can be changed, and the closed characteristic of the gap can be extended to a semi-surrounding according to the actual situation, such as opening along the central line A to the edge of the transmission line. That is to say, the shape and size of the signal island 1 304 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 for the signal island 1 304 and the first slit 303. After multiple experiments, the shape and size suitable for the material can be obtained.

Please refer to FIG. 3 for details. The middle layer 13 shown includes a copper-clad region 302, a series of vias 21 to 28, a signal line island 304, a signal line via 29, and a slit 303 surrounding the signal island 1. Area 301 indicates the separation distance between the intermediate plane and the outer edge of the transmission line and the intermediate plane 13. The series of via holes 21, 22 and via holes 23, 24 are symmetrical up and down about the central line 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 with a repeating period of the via 27 to via 28 center position spacing, mirrored about the center line A to the other side. The repetition period from via hole 27 to via hole 28 is far less than a quarter of the highest working frequency of the transmission line structure according to the optimized design. The signal line vias 29 are different from the series of vias, the number of the signal line vias 29 is far less than the series of vias, and the positions of the signal line vias need to be optimized. It can be seen from FIG. 3 that a signal island 1 304 and a first slit 303 surrounding the signal island 1 are respectively arranged at both ends of the middle layer 13 , which is an implementation manner.

At least one end of the second connection layer 15 (that is, the intermediate layer 15) is provided with a signal transition area 502 and several gaps provided on the signal transition area 502, and corresponding signal line vias 29 are provided at the corresponding positions of the signal transition area. Transition region 502 is characterized by inductance. Referring to FIG. 7 , taking the second connection layer 15 as an example, the signal transition region 502 and the gaps provided 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 several slits are also variable. It only needs to go through many experiments to get the shape and size suitable for the material.

At least one end of the third connection layer 17 is provided with a signal island 2 703 and a second slit 704 surrounding the signal island 2 703, and a corresponding signal line via hole 29 is provided on the corresponding position of the signal island 2 703, and the signal island 2 703 and the second slit 704 The second gap 704 is used to adjust the first capacitor C1.

The signal line via hole 29 of the first connection layer is connected to the signals of the signal island 1 304 , the signal island 2 703 and the signal transition area 502 , and the signal transition area 502 is connected to the signal line 506 .

Figure 2 to Figure 5 illustrate the connection structure. The connection structure includes signal island 1 304 of the middle layer 13 and the slit 303 surrounding the signal island 1, the signal transition regions 502 to 505 of the middle layer 15, and the signal island 2 703 shown in the middle layer 17 and the irregularities surrounding the signal island 2. Slot structure 704 . The gap 303 is used to adjust the first capacitor C1. That is to say, the gap 303 and the gap 704 jointly regulate the first capacitance C1. C1 as shown in Figure 7.

The signal transition area 502 is an irregular smooth area, and the signal line via hole 29 connects the signal island 1 304 , the signal island 2 703 signal and the signal transition area 502 . The signal transition area 502 is connected to the signal line 506. The slots 503, 504, 505 are used to adjust the electrical parameters of the signal transition region, ie the inductance characteristic L1 of the transmission line. The signal line 506 is a uniform conductor with equal width, and its distributed equivalent inductance and capacitance are L0 and C0 respectively. The equivalent circuit is shown in Figure 7.

According to the traditional transmission line theory, if the periodic L0 and C0 are directly connected to the 50 ohm connector, the discontinuity introduced by the high-frequency loss is very large. Introduce the connection structure of the present invention, optimize L1, C1, greatly reduce the impact of discontinuity, and minimize the insertion loss of the transmission line structure. Facts have proved that the return loss of the transmission line structure processed in this way is reduced by 5dB at 6GHz, and the insertion loss at 6GHz is reduced by 20% compared with the public product.

501 in FIG. 4 represents a non-metallic region on the intermediate plane 15 . Among Fig. 5, 701 represents the non-metallic region of the middle surface 17, and the hatched part shown in 702 is a metal region. Figure 6 shows the underlying structure diagram, the hatched area is a non-conductive area, and the transmission line structure is shielded. There is no limit to the implementation process of the transmission line. The embodiment of the present invention is a circuit board method, which adopts lamination, photo-etching, chemical plating process.

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

The preferred embodiments of the invention are provided only to help illustrate the invention. The preferred embodiments are not exhaustive in all detail, nor are the inventions limited to specific embodiments described. Obviously, many modifications and variations can be made based on the contents of this specification. This description selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can make good use of the present invention. The invention is to be limited only by the claims, along with their full scope and equivalents.

Claims (10)

1. a low-loss flat transmission line, it is characterized in that, comprise for preventing metallic region is oxidized and strip line structure contacts with surrounding good conductor some solder masks, for some adhesive linkages, the some dielectric layers for Energy Transfer region, the some articulamentums for physically upper and lower adhesive effect, wherein:

Described tack coat is between described solder mask; Described articulamentum is between described tack coat; Described dielectric layer lays respectively between two articulamentums;

Described articulamentum at least comprises the first articulamentum, the second articulamentum and the 3rd articulamentum, wherein,

Signalization island one and the first gap around signal island one at least one end of first articulamentum, and at least one holding wire via hole is set on signal island one, described signal island one and the first gap for regulating the first capacitance characteristic of transmission line,

Signalization transitional region and some gaps of arranging on signal transition region at least one end of second articulamentum, and corresponding holding wire via hole is set on the correspondence position of signal transition region, described signal transition region and some gaps thereof are for regulating the inductance characteristic of transmission line

Signalization island two and the second gap around signal island two at least one end of 3rd articulamentum, and corresponding holding wire via hole is set on the correspondence position of signal island two, signal island two and the second gap for regulating the first capacitance characteristic of transmission line,

The signal in the holding wire via hole of the first articulamentum messenger island one, signal island two and signal transition region repeatedly, signal transition region is connected with holding wire.

2. low-loss flat transmission line as claimed in claim 1, is characterized in that, signal transition region is arranged three articles of gaps: the 3rd gap, the 4th gap and the 5th gap, and the 3rd gap, the 4th gap and the 5th gap regulate the inductance characteristic of transmission line.

3. low-loss flat transmission line as claimed in claim 2, it is characterized in that, 3rd gap, the 4th gap and the 5th gap are respectively side by side, the gap opening in the 3rd gap and the 5th gap in the same way, contrary with the gap opening in the 4th gap, further, the 4th gap is between the 3rd gap and the 5th gap.

4. low-loss flat transmission line as claimed in claim 1, it is characterized in that, annular is arranged to around signal island two in the second gap, or is arranged to semi-surrounding type around signal island two, annular is arranged to around signal island one in first gap, or is arranged to semi-surrounding type around signal island one.

5. low-loss flat transmission line as claimed in claim 4, is characterized in that, the shape that the shape that signal island two and the second gap are formed and signal island one and the first gap are formed is unanimous on the whole.

6. low-loss flat transmission line as claimed in claim 1, it is characterized in that, some solder masks comprise top layer and bottom, top layer comprises the non-conducting areas of strip line structure, and on non-conducting areas, arrange some connecting sewings for connector welded disc position, and one of them connecting sewing physically connects connector holding wire conductor.

7. low-loss flat transmission line as claimed in claim 1, it is characterized in that, first articulamentum is also arranged some serial via holes and periodicity via hole, series via hole is symmetrical up and down about center line between any two, or with centerline parallel and mirror image to center line opposite side, the repetition period of described periodicity via hole is the center spacing between via hole.

8. low-loss flat transmission line as claimed in claim 6, it is characterized in that, adhesive linkage is two layers, and one is positioned at the below of top layer, its two top being positioned at bottom.

9. low-loss flat transmission line as claimed in claim 8, it is characterized in that, dielectric layer is two layers, and one is between the first articulamentum and the second articulamentum, and it is two between the second articulamentum and the 3rd articulamentum.

10. low-loss flat transmission line as claimed in claim 1, it is characterized in that, connector is 50 ohm of joints.