CN108123196A - Wideband filtered based on vertical two-sided parallel strips integrates three-dimensional balun - Google Patents

Abstract

An embodiment of the present invention provides a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines, wherein the first, second and third port feeders are all composed of microstrip transmission lines; The hole surface is connected to a plurality of first metal vias; the ground plane of the second layer is connected to the via surface through the first metal vias; on the vertical board, the filter has a top filtering stub; the filter and a quarter The wavelength impedance converters are connected and are composed of vertical double-sided parallel strip lines, and are symmetrically located on the third and fourth floors; the common ground is located in the middle of the third and fourth floors; the top filtering branch passes through the second metal The via hole is connected to the common ground; the impedance gradient structure located on the fourth layer is respectively connected to the feeder line of the first port, the via hole surface and the filter. Thus, the embodiment of the present invention realizes a single balun for balanced-unbalanced conversion from a microstrip line to a vertical double-sided parallel strip line, and also incorporates a filtering function to improve integration.

Description

Broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines

technical field

The invention relates to the field of radio frequency technology, in particular to a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines.

Background technique

The main function of the balun is to realize that when one input signal arrives at two output ports, the two output signals output are of equal amplitude and phase inversion, and vice versa. In addition, when the front and rear circuits of the balun do not match, it can also play the role of impedance transformation. In short, a balun converts a high-frequency signal from a single-ended unbalanced input to a double-ended balanced output with impedance matching. Therefore, as a three-port device, baluns are widely used in the balanced layout of radio frequency circuits, such as filters, power amplifiers and antenna feed networks, which directly affect the performance and quality of wireless communications. At present, baluns and filters, as adjacent components of the feed front end, have become indispensable components such as radio frequency systems.

In recent years, as a balanced transmission line, the double-sided parallel strip line has become a research hotspot in the field of radio frequency due to its characteristic of frequency-independent phase inversion.

However, at present, in this field, there is still a gap in the research on combining the vertical double-sided parallel strip line with the single balun and making it have a filtering function.

Therefore, how to provide a balun that combines the vertical double-sided parallel strip line with a single balun and makes it have a filtering function has become a technical problem to be solved.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines. By combining the vertical double-sided parallel strip lines with a single balun, the balun can realize the filtering function .

In order to achieve the above object, the following technical solutions are provided:

A broadband filtering integrated three-dimensional balun based on vertical double-sided parallel strip lines, comprising: a horizontal feed board and a vertical board perpendicular to the horizontal feed board; wherein:

The horizontal feeder board is provided with a first port, a second port, a third port, a first port feeder, a second port feeder and a third port feeder; the first port feeder, the second port feeder and all The third port feeders are all composed of microstrip transmission lines, and the first port feeder is connected to the first port, the second port feeder is connected to the second port, and the third port feeder is connected to the The third port is connected;

The horizontal feed board includes a first layer and a second layer and a plurality of first metal vias; wherein the via surface is connected to the plurality of first metal vias, and the first layer includes vias plane; the second layer includes a ground plane, and the ground plane is connected to the via plane through the first metal via hole;

The vertical board includes a third layer, a common ground with a cross slit, a fourth layer, an impedance gradient structure, a second metal via, a filter, and a quarter-wavelength impedance converter, wherein the common ground is located at The third layer is in the middle of the fourth layer; the filter has oppositely bent top filtering branches; the filter is connected to the quarter-wavelength impedance converter and is composed of vertical double-sided parallel It is composed of striplines, and they are respectively located symmetrically on the third layer and the fourth layer; the top filter branch is connected to the common ground through the second metal via; the impedance gradient structure is located on the The fourth layer is connected to the first port feeder, the via surface and the filter respectively;

Wherein, the first port, the first port feeder, the impedance gradient structure, the filter, the common ground, the quarter-wavelength impedance converter, the second port feeder, the The third port feeder, the second port and the third port form a signal transmission path.

Optionally, the microstrip transmission line, the vertical double-sided parallel strip line, the ground plane, the via plane, and the common ground are all conductive metals.

Optionally, the conductive metal is brass.

Optionally, the plurality of first metal vias are arranged in two columns with the same pitch.

Optionally, the first port, the second port and the third port are SMA connectors.

Optionally, the horizontal feed board and the vertical board have the same dielectric constant.

Optionally, the horizontal feed board and the vertical board have different thicknesses.

Optionally, the number of the plurality of first metal vias is 10.

Optionally, there are two second metal vias; the first port, the first port feeder, the impedance gradient structure, the filter, the common ground, the quarter The wavelength impedance converter, the second port feeder, the third port feeder, the second port, and the third port form two signal interaction transmission paths.

An embodiment of the present invention provides a broadband filter integrated three-dimensional balun based on vertical double-sided parallel strip lines, which includes: a horizontal feed board and a vertical board perpendicular to the horizontal feed board; wherein the horizontal feed board is set There are a first port, a second port, a third port, a first port feeder, a second port feeder, and a third port feeder; the first port feeder, the second port feeder, and the third port feeder are each composed of a microstrip transmission line, and The first port feeder is connected to the first port, the second port feeder is connected to the second port, and the third port feeder is connected to the third port; the horizontal feeder board includes a first layer, a second layer and a plurality of first metal vias ; Wherein, the first layer includes a via surface, and the via surface is connected to a plurality of first metal vias; the second layer includes a ground plane, and the ground plane is connected to the via surface through the first metal via; the vertical plate includes the first The third layer, the common ground with a cross gap, the fourth layer, the impedance gradient structure, the second metal via, the filter and the quarter-wavelength impedance converter, wherein the common ground is located between the third layer and the fourth layer; The filter has oppositely bent top filtering branches; the filter is connected to the quarter-wavelength impedance converter and is composed of vertical double-sided parallel strip lines, and is symmetrically located on the third and fourth layers; the top The filtering branch is connected to the common ground through the second metal via; the impedance gradient structure is respectively connected to the first port feeder, the via surface and the filter; the impedance gradient structure is located on the fourth layer; wherein, the first port, the first port feeder, The impedance gradient structure, the filter, the common ground, the quarter-wavelength impedance converter, the second port feeder, the third port feeder, the second port and the third port form a signal transmission path.

Compared with the prior art, the embodiment of the present invention adopts the above-mentioned technical solution to form the first port feeder, the second port feeder and the third port feeder by using the microstrip line, and connect the first port feeder, the second port feeder and the third port feeder The three-port feeder is connected to the first port, the second port and the third port respectively; then, utilizes the vertical double-sided parallel strip line to form a filter and a quarter wavelength impedance converter; and the filter and a quarter The whole wavelength impedance converter is symmetrically located on the third layer and the fourth layer respectively, and is respectively connected with the impedance gradient structure, the feeder line of the first port, the feeder line of the second port, and the feeder line of the third port. The first port feeder, the impedance gradient structure, the filter, the common ground, the quarter wavelength impedance converter, the second port feeder, the third port feeder to the signal transmission path of the second port and the third port; thus, the present invention In the embodiment of the invention, the balun and the filter are integrated together, and the impedance matching between the vertical plate and the horizontal feed plate is realized through a quarter-wavelength impedance converter; The balanced-unbalanced conversion single-body balun with vertical double-sided parallel strip lines also incorporates the filtering function, eliminates parasitic coupling, reduces loss, and is smaller in size than the overall size of the balun and filter designed separately Small, improved integration.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Of course, implementing any product or method of the present invention does not necessarily need to achieve all the above-mentioned advantages at the same time.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

1 is a schematic structural diagram of a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines according to an embodiment of the present invention;

2 is a schematic structural diagram of a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines according to an embodiment of the present invention;

Fig. 3a is an electric field distribution and an equivalent schematic diagram of a first virtual port according to an embodiment of the present invention;

Fig. 3b is an electric field distribution and an equivalent schematic diagram of a second virtual port according to an embodiment of the present invention;

Fig. 4 is a schematic structural view of a vertical plate according to an embodiment of the present invention;

Figure 5a is a schematic diagram of a traditional double-sided parallel stripline placed in a high-power metal shielding box;

Fig. 5b is a schematic diagram of a balun placed in a high-power metal shielding box according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of an equivalent circuit of the balun shown in FIG. 2 according to an embodiment of the present invention;

FIG. 7a is a schematic circuit diagram of the equivalent circuit of the balun shown in FIG. 2 obtained by using the odd-even mode method under odd-mode excitation according to an embodiment of the present invention;

Fig. 7b is a schematic circuit diagram of the equivalent circuit of the balun shown in Fig. 2 obtained by using the odd-even mode method under even-mode excitation according to an embodiment of the present invention;

Fig. 8a is a schematic diagram of the structural dimensions of a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines according to an embodiment of the present invention;

Fig. 8b is a schematic diagram of the structural dimensions of a broadband filtering integrated stereo balun vertical plate based on vertical double-sided parallel strip lines according to an embodiment of the present invention;

9 is a schematic diagram of a simulation curve of a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Facing the ever-changing information and network technology, electronic information systems such as smart wireless mobile communication and multi-system radar are developing towards multi-frequency and multi-mode, dynamic cognition, miniaturization and low power consumption. Therefore, more stringent performance requirements are imposed on the units in the radio frequency system. For example, due to the single function of traditional microwave devices, the application requirements of multi-frequency and multi-channel parallelism make the front-end of the radio frequency system face the trend of doubling the number of devices, which in turn leads to the bulky, complex structure and functional complexity of the entire electronic information system. High energy consumption, low energy efficiency and other defects.

At present, although extensive research has been carried out on the integrated filtering function of radio frequency devices in this field, there is still a blank in the research on combining vertical double-sided parallel strip lines and single baluns to make them have filtering functions. How to provide a balun that combines the vertical double-sided parallel strip line with a single balun and makes it have a filtering function has become a technical problem to be solved. To this end, an embodiment of the present invention provides a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines.

FIG. 1 is a schematic structural diagram of a broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines provided by an embodiment of the present invention. The balun includes: a horizontal feed board 1 and a vertical board 2 perpendicular to the horizontal feed board 1; wherein, the horizontal feed board 1 is provided with a first port 11, a second port 12, a third port 13, a One port feeder 14, the second port feeder 15 and the third port feeder 16; the first port feeder 14, the second port feeder 15 and the third port feeder 16 are all made of microstrip transmission lines, and the first port feeder 14 and the first port feeder The ports 11 are connected, the second port feeder 15 is connected to the second port 12, and the third port feeder 16 is connected to the third port 13;

The horizontal feed board 1 includes a first layer 17 and a second layer 18, and a plurality of first metal vias 1711; wherein, the first layer 17 includes a via surface 171, and the via surface 171 and a plurality of first metal vias 1711 connected; the second layer 18 includes a ground plane 181, and the ground plane 181 is connected to the via plane 171 through a first metal via 1711;

The vertical board 2 includes a third layer 21, a common ground 22 with a cross gap, a fourth layer 23, a filter 24, a quarter-wavelength impedance converter 25, a second metal via hole 26, and an impedance gradient structure 27, wherein , the public ground 22 is located in the middle of the third layer 21 and the fourth layer 23; the filter 24 has a top filter branch 241 bent opposite; It is composed of parallel strip lines, and they are respectively symmetrically located on the third layer 21 and the fourth layer 23; the top filter branch 241 is connected to the common ground 22 through the second metal via 26; the impedance gradient structure 27 is located on the fourth layer 23, and respectively Connected to the first port feeder 14, the via surface 171 and the filter 24;

Among them, the first port 11, the first port feeder 14, the impedance gradient structure 27, the filter 24, the common ground 22, the quarter wavelength impedance converter 25, the second port feeder 15, the third port feeder 16, the second The port 12 and the third port 13 form a signal transmission path.

In the embodiment of the present invention, by symmetrically arranging the filter 24 and the quarter-wavelength impedance converter 25 on the third layer 21 and the fourth layer 23 of the vertical plate 2, not only impedance matching is realized, but also by integrating the filter On the balun, the balun integrated with the filter has the functions of signal balance-unbalance conversion and frequency selection. Compared with the overall size of the two discrete components of the independent balun and filter, the size is reduced, which can improve the integration of the radio frequency system applying the balun and filter, can effectively reduce parasitic coupling and loss, and improve electronic information engineering stability. In addition, in this embodiment, the vertical plate 2 and the horizontal feed plate 1 are vertically arranged to realize a three-dimensional balun constructed with double-sided parallel strip lines in a vertical form, thereby ensuring the integrity of the horizontal ground and simplifying the metal structure. The installation process of the shielding box.

In the embodiment shown in FIG. 1 , the integrity of the ground plane 181 on the second layer 18 of the horizontal feed board 1 can be ensured by arranging the horizontal feed board 1 perpendicular to the vertical board 2 .

In some embodiments, the microstrip transmission line, the vertical double-sided parallel strip line, the ground plane 181 , the via plane 171 , and the common ground 22 are all conductive metals. Specifically, the conductive metal is brass.

In practical applications, except for the impedance gradient structure 27 on the vertical board 2 , other structures adopt vertical double-sided parallel strip lines.

Since the vertical double-sided parallel strip line has frequency-independent anti-phase characteristics, the balun provided by the embodiment of the present invention has good broadband performance.

In practical applications, the microstrip transmission line can be implemented by cladding copper on the horizontal feeder board 1; The third layer 21 and the fourth layer 23 are implemented by pouring copper; similarly, the common ground 22, the ground plane 181 and the via surface 171 can also be implemented by pouring copper.

In some embodiments, the plurality of first metal vias 1711 are arranged in two rows with the same pitch.

In some optional embodiments, the number of the first metal vias 1711 is ten.

In this embodiment, the first metal via hole 1711 can be implemented by covering the surface of the via hole with copper. Among them, brass can be used. The first metal via 1711 connects the via surface 171 on the first layer 17 to the ground plane 181 on the second layer 18 through a metal (for example, brass) on the inner wall.

In some embodiments, the first port 11 , the second port 12 and the third port 13 are SMA connectors. Wherein, the first port 11 , the second port 12 and the third port 13 are used for connecting with external devices. In practical applications, the first port 11, the second port 12 and the third port 13 are reasonably distributed on the horizontal feed board 1 as the three feeding ports of the balun provided by the embodiment of the present invention; wherein the first port as input ports and the other two ports as output ports.

In some embodiments, the dielectric constant of the horizontal feed board 1 and the vertical board 2 is the same, for example, the dielectric constant is 3.48.

In some embodiments, the thicknesses of the above-mentioned horizontal feed board 1 and the above-mentioned vertical board 2 are different. Specifically, the horizontal feed plate 1 may be 0.762 mm thick, and the vertical plate 2 may be 1.016 mm thick.

The boards of the horizontal feed board 1 and the above-mentioned vertical board 2 in the above embodiment can use Rogers (Rogers) 4350B boards and the like.

In the embodiment shown in Fig. 1, the filter 24 and the quarter-wavelength impedance converter 25 are symmetrically located at the third layer 21, and the fourth layer 23 refers to the filter 24 and the quarter-wavelength impedance converter 25 respectively. The whole body is correspondingly arranged on the third layer 21 and the fourth layer 23 of the vertical plate 2 respectively, and the shapes and sizes on the third layer 21 and the fourth layer 23 are the same.

In some embodiments, there are two second metal vias 26; The second port feeder 15 , the third port feeder 16 , the second port 12 and the third port 13 form two signal exchange transmission paths.

In this embodiment, the common ground 22 with a cross gap is located in the middle of the third layer 21 and the fourth layer 23 of the vertical board 2, and the top filtering branch 241 on the filter 24 is grounded through two second metal vias 26 , so that two signal interaction transmission paths are formed on the vertical board 2 .

Here, for the convenience of describing the embodiment of the present invention, as shown in FIG. 2, the following definitions are made:

The first virtual port 28A: the connection between the impedance gradient structure 27 and the input port feeder 14, and the first virtual port is also connected to the via surface 171;

The second virtual port 28B: the connection between the quarter wavelength impedance converter 25 of the third layer 21 and the fourth layer 23 of the vertical board 2 and the first output port feeder 15 and the second output port feeder 16 respectively.

Since the conduction band widths of the third layer 21 and the fourth layer 23 on the first virtual port are quite different; therefore, in this embodiment, an impedance gradient structure 27 is provided on the fourth layer 23 of the vertical board 2 . 1 and 2 show that the impedance gradient structure 27 is located on the vertical plate 2 near the first port 11, but the present invention is not limited thereto, for example, the impedance gradient structure 27 can also be provided on both sides of the vertical plate 2 .

Based on the above description of the embodiments of the present invention, the following compares the balun provided by the embodiments of the present invention with the prior art to illustrate the technical effects achieved by the embodiments of the present invention.

Filters and baluns, as adjacent components of the feed front end, are indispensable components such as radio frequency systems. The traditional method is to design the filter and balun independently, and then connect them. In this way, it is not conducive to the miniaturization and integration of the radio frequency system. Also, this traditional approach introduces parasitic coupling and losses due to the connection between the two separate components.

However, in the embodiment of the present invention, the filter 24 is arranged on the vertical board 2, and the balun and the filter 24 are integrated together to replace the traditional independent balun and filter with a single balun that integrates the filtering function. Components are smaller in size than connecting two discrete baluns and filters, can improve the integration of radio frequency systems using baluns and filters, can effectively reduce parasitic coupling and loss, and improve the stability of electronic information engineering .

The balun provided by the present invention will be described in detail below with reference to Fig. 2, 3a, 3b and Fig. 4 in specific embodiments.

In this embodiment, the first port 11 is the input port, the second port 12 is the first output port, the third port 13 is the second output port, the first port feeder 14 is the input port feeder, and the second port feeder 15 is The first output port feeder line and the third port feeder line 16 are used as the second output port feeder line as an example for description.

As shown in FIG. 2 , the broadband filtering integrated stereo balun based on vertical double-sided parallel strip lines includes: a horizontal feed board 1 and a vertical board 2 . in:

The horizontal feed board 1 is a two-layer printed circuit board, which includes a first layer (also referred to as a top layer in this embodiment) 17 and a second layer (also referred to as a bottom layer in this embodiment) 18; The board 1 is provided with an input port 11, a first output port 12, a second output port 13, an input port feeder 14, a first output port feeder 15, a second output port feeder 16, and 10 first metal vias 1711; , the input port 11 is connected with the input port feeder 14, the first output port 12 is connected with the first output port feeder 15, the second output port 13 is connected with the second output port feeder 16, the input port 11, the first output port 12 and the second output port The impedance of the two output ports 13 is 50 ohms; the input port feeder 14, the first output port feeder 15 and the second output port feeder 16 are implemented in the form of three sections of microstrip lines; 10 first metal vias 1711 are arranged on the horizontal feeder In the electric board 1, 10 first metal vias 1711 are arranged in two rows at the same interval; the first layer 17 of the horizontal feed board 1 is provided with a via surface 171; the second layer 18 of the horizontal feed board 1 is provided with ground plane 181;

The vertical board 2 is a three-layer printed circuit board, which includes: a third layer 21, a common ground 22 with cross slits, a fourth layer 23, and two holes penetrating the third layer 21, the common ground 22 and the fourth layer 23. The second metal via hole 26; wherein, the third layer 21 and the fourth layer 23 are symmetrically provided with a filter 24 and a quarter-wavelength impedance converter 25 which are all composed of vertical double-sided parallel strip lines; wherein, the filter The device 24 has a pair of oppositely bent top filter branches 241; the common ground 22 grounds the pair of oppositely bent top filter branches 241 through the second metal via 26 to form two An interactive transmission path;

The impedance gradient structure 27 is arranged on the side of the vertical board 2 close to the input port 11, and is connected with the input port feeder 14, the via surface 171, and the filter 24, so as to realize the transition from the microstrip line to the vertical double-sided parallel strip line. conversion.

Here, for the convenience of describing the embodiments of the present invention, the following definitions are made:

The impedance of half of the vertical double-sided parallel stripline is defined as Z ₁ ~ Z ₅ ; therefore, the impedance of the vertical double-sided parallel stripline is defined as 2Z ₁ ~ 2Z ₅ ;

Odd-mode excitation means that the excitation signals of the first virtual port 28A and the second virtual port 28B are out of phase with equal amplitude; even-mode excitation means that the excitation signals of the first virtual port 28A and the second virtual port 28B are in phase with equal amplitude; Z _ino , Z _ine represents the equivalent input impedance under odd and even mode excitation respectively; when Z _ino and Z _ine tend to infinity, the resonant frequency of the filter can be obtained.

As shown in FIG. 2, a first virtual port 28A and a second virtual port 28B are shown therein.

Fig. 3a exemplarily shows the electric field distribution and equivalent schematic diagram of the first virtual port 28A; Fig. 3b exemplarily shows the electric field distribution and equivalent schematic diagram of the second virtual port 28B. Among them, ε _r represents the dielectric constant; 2h ₂ represents the thickness of the vertical plate 2, for example, 1.016 mm; Z _s represents the input impedance; 2Z _L represents the output impedance; θ represents the electrical length of the transmission line.

In this embodiment, since the conduction band widths of the first dummy port 28A on the third layer 21 and the fourth layer 23 on the vertical board 2 are quite different, the first dummy port 28A can be equivalent to a section distributed in the vertical A microstrip line with a thickness of 2h ₂ and an input impedance of Z _s on board 2. Since the output signals of the first output port 12 and the second output port 13 of the balun are equal amplitude and anti-phase, the second virtual port 28B can be regarded as the series connection of the first output port 12 and the second output port 13, namely It is equivalent to a double-sided parallel stripline distributed on the vertical plate 2 with a thickness of 2h ₂ and an output impedance of 2Z _L.

Based on the positions of the first and second virtual ports (28A, 28B) shown in FIG. One end is aligned with the center position of the second virtual port 28B and connected accurately so that the signal can pass through with maximum energy; the other end of the input port feeder 14, the other end of the first output port feeder 15 and the second output port feeder The other end of 16 is used for connecting external equipment.

In addition, because the first virtual port 28A is connected to the input port feeder 14 on the one hand, and the other side is connected to the via surface 171; therefore, considering the size of the input port feeder 14 and the via surface, and in order to reduce the discontinuous signal transmission Therefore, in this embodiment, on the side of the vertical board 2 close to the input port 11, specifically, on the fourth layer 23 of the vertical board 2, the side where the first virtual port 28A is connected to the via surface is provided Impedance gradient structure 27 . Thus, the discontinuity of signal transmission is reduced through the impedance gradient structure 27 , and a good impedance matching from the first virtual port 28A to the second virtual port 28B is further realized. Wherein, the material of the impedance gradient structure 27 is realized by pouring copper. Thus, the embodiment of the present invention utilizes the microstrip line to form the input port feeder 14, the first output port feeder 15 and the second output port feeder 16, and the input port feeder 14, the first output port feeder 15 and the second output port feeder 16 is connected with input port 11, first output port 12 and second output port 13 respectively; Then, utilize vertical double-sided parallel strip line to form filter 24 and quarter-wavelength impedance converter 25 again; And impedance tapered structure 27 are respectively connected with the input port feeder 14, the via surface 171 and the filter 24, thereby realizing the balanced-unbalanced conversion from the microstrip line to the vertical double-sided parallel strip line.

Fig. 4 exemplarily shows a schematic structural view of the above-mentioned vertical plate. Among them, the impedance gradient structure 27 is distributed on the left side of the vertical board 2, and by connecting the input port feeder 14, the via surface 171 and the filter 24 of the horizontal feeder board 1, it realizes the transformation from the microstrip line to the vertical double-sided parallel Conversion with lines. For the specific implementation process of the filter 24, please refer to the following literature: 2013, Novelminiaturization method for wideband filter design with enhanced upperstopband, IEEE Trans. Microw. Theory Techn.

This embodiment is based on the signal interference technology (transversal signal-interaction concepts), by setting a common ground 22 with a cross gap between the third layer 21 and the fourth layer 22, and through, for example, two second metal vias 26, the A pair of oppositely bent top filtering stubs 241 are grounded, so that the balance conversion function of the balun provided by this embodiment is more stable, the filtering bandwidth is expanded, and the stop-band attenuation performance is steep and deep.

In summary, in this embodiment, the integrity of the ground plane 181 on the second layer 18 of the horizontal feed board 1 is ensured by arranging the horizontal feed board 1 and the vertical board 2 vertically; at the same time, the vertical board 2, except for the impedance gradient structure 27, the filter 24 and the quarter-wavelength impedance converter 25 all adopt vertical double-sided parallel strip lines, thus, using the frequency-independent anti-phase characteristics of the vertical double-sided parallel strip lines , to achieve the broadband performance of the balun provided by the embodiment of the present invention; moreover, by setting a common ground 22 with a cross gap in the middle of the third layer 21 and the fourth layer 22, two interactive surfaces are formed on the vertical board 2 The transmission path of the transmission signal makes the balance conversion function of the balun provided by the embodiment of the present invention not only stable, but also expands the filtering bandwidth, and has a steep and deep stop-band attenuation performance, realizing a vertical double-sided parallel Miniaturized broadband filter integrated single stereo balun with line.

The technical effect obtained by the embodiment of the present invention will be described in detail below in conjunction with FIGS. 5a and 5b.

In order to visually demonstrate the technical effect of the embodiment of the present invention, the embodiment of the present invention and the traditional double-sided parallel strip line are both placed in a high-power metal shielding box for comparison.

Assume that the distance between the bottom stripline of the traditional double-sided parallel stripline and the bottom of the high-power metal shielding box is S ₁ ; the distance between the stripline of the balun provided by the embodiment of the present invention and the side wall of the high-power metal shielding box is S ₂ .

Figure 5a exemplarily shows a schematic diagram of a traditional double-sided parallel strip line placed in a high-power metal shielding box; Figure 5b exemplarily shows a balun provided by an embodiment of the present invention placed in a high-power metal shielding box schematic diagram.

As shown in Figure 5a, in order to avoid the ground loop caused by the direct contact between the bottom strip line of the traditional double-sided parallel strip line and the bottom of the high-power metal shielding box, the traditional double-sided parallel strip line needs to be suspended in the high-power metal shielding box . It can be seen that the traditional method not only increases the manufacturing difficulty, but also produces a parasitic response between the bottom strip line and the bottom of the high-power metal shielding box due to the existence of the distance _S1 . However, as shown in Figure 5b, the embodiment of the present invention arranges double-sided parallel strip lines on the vertical board 2 perpendicular to the horizontal feeder board 1, thereby ensuring the integrity of the ground plane 181 on the horizontal feeder board 1 sex. In actual engineering, when S ₂ >10h (h is the thickness of the dielectric plate), the influence of the side wall of the high-power metal shielding box on the vertical double-sided parallel strip line is negligible. Therefore, the balun provided by the embodiment of the present invention can directly contact the bottom of the high-power metal shielding box. Thus, not only the spurious resonance is eliminated, but also the installation process of the high-power metal shielding box is simplified.

The mirror image theory shows that when the opposite voltage is applied to the upper and lower ends of the double-sided parallel strip, the voltage in the middle of the dielectric plate in the middle is 0. Therefore, for the balun shown in FIG. 2 , when the common ground 22 with a cross gap is placed in the middle of the double-sided parallel strip line, the electric field distribution of the second virtual port 28B will not change. Based on this, the double-sided parallel stripline of the second virtual port 28B can be regarded as two microstrip lines arranged back-to-back on the same dielectric board, and the electrical length of each microstrip line remains unchanged, but the thickness of the dielectric board and the impedance The values are halved, which are h ₂ and Z _L , respectively.

Fig. 6 exemplarily shows the schematic diagram of the equivalent circuit of the balun shown in Fig. 2; Fig. 7a exemplarily shows the equivalent circuit of the balun shown in Fig. 2 obtained by using the odd-even mode method under odd-mode excitation Schematic diagram of the circuit; FIG. 7b exemplarily shows a schematic circuit diagram of the equivalent circuit of the balun shown in FIG. 2 obtained by using the odd-even mode method under even-mode excitation. Among them, two sections of double-sided parallel strip lines (2Z ₁ , θ2) and the open branch (2Z ₂ , θ) connected in the middle constitute a main transmission path 29B; a pair of double-sided parallel strip lines (2Z ₃ , θ) and short circuit Branch nodes (2Z ₄ , θ) are cascaded to form an auxiliary transmission path 29A. The two transmission paths (29B, 29A) interact with each other. Based on the signal mutual interference technology, the phase difference between the signals on the two transmission paths produces a wider stop band, and jointly transmit the signal from the first virtual port 28A to the second virtual port 28A. Two dummy ports 28B, thereby improving the balun's filtering, balanced conversion, and stopband attenuation performance. In addition, through a quarter-wavelength double-sided parallel strip line (2Z ₅ , θ) (that is, a quarter-wavelength impedance converter 25), the equivalent output impedance of the main transmission path 29B and the auxiliary transmission path 29A and The second virtual port 28B implements impedance matching 27 .

8a and 8b exemplarily show schematic diagrams embodying the structural dimensions of the balun provided by the embodiment of the present invention.

This embodiment assumes that the input impedance (ie Z _s ) and the output impedance (ie Z _L ) are 50 ohms (Ω); the electrical length (θ) is 90°; other circuit impedances are (unit: Ω): Z ₁ =70 , Z ₂ =16.5, Z ₃ =16, Z ₄ =49, Z ₅ =35.36. Under the condition that the operating frequency is 6GHz, the following physical dimensions (unit: mm) of the balun can be obtained by using the electromagnetic simulation application program (High Frequency Structure Simulator): L ₀ =10.0, W ₀ =1.7, L ₁ =4.3, W ₁ = 0.7, L ₂ = 5.1, W ₂ = 7.1, L ₃ = 7.0, W 3 = 5.3, L ₄ = 7.5, W ₄ = 1.2, L ₅ = 2.0, _{W 5 =} 1.9, W ₆ = 1.0, L ₇ = 10.0, W ₇ = 2.5, W ₈ = 8.9. Wherein, L ₀ ... L ₅ and L ₇ represent the length; W ₀ ... W ₈ represent the width.

FIG. 9 exemplarily shows a schematic diagram of a simulation curve of a balun provided by the embodiment shown in FIG. 2 .

Wherein, |S ₁₁ | represents the matching performance of the input port 11; |S ₂₁ | represents the transmission performance of the first output port 12; |S ₃₁ | represents the transmission performance of the second output port 13; ∠S ₂₁ -∠S ₃₁ represent The phase difference between the first output port 12 and the second output port 13 .

It can be seen from Figure 9 that when |S ₁₁ |<-15dB, the operating frequency band is 1.46GHz～3.48GHz, and within this bandwidth, |S ₂₁ | and |S ₃₁ | are always kept within the range of -3.1±1dB . In the range of 2.88GHz to 3.84GHz, ∠S ₂₁ -∠S ₃₁ fluctuates in the range of -180°±10°, and the resulting error is due to the signal superposition of the main transmission path 29B and the auxiliary transmission path 29A or metal vias caused by the inductive effect. In addition, in the upper stop band as wide as 5.13GHz (4.08GHz-9.21GHz), both |S ₂₁ | and |S ₃₁ | are less than -20dB. Among them, dB means decibel.

It can be seen from the simulation results shown in FIG. 9 that the balun provided by the embodiment of the present invention has at least the following beneficial effects: good input matching, small insertion loss, stable phase difference, wide filtering bandwidth, and steep and deep stopband attenuation.

In summary, compared with the traditional method of connecting two separate baluns and filters when applying baluns and filters, the prior art has parasitic coupling and loss; and the embodiment of the present invention integrates the balun and the filter 24 together, and realizes the impedance matching between the vertical plate and the horizontal feed plate through a quarter-wavelength impedance converter, ensuring the first virtual The impedance matching between the port 28A and the second virtual port 28B realizes a single balun for balanced-unbalanced conversion from the microstrip line to the vertical double-sided parallel strip line, and also incorporates a filtering function to eliminate parasitic coupling and reduce The loss is reduced, and the size of the embodiment of the present invention is smaller than the overall size of the separately designed balun and filter, which improves the degree of integration.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Each embodiment in this specification is described in a related manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. For related information, please refer to the description of the method embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims (9)

1. A broadband filter integrated stereo balun based on vertical double-sided parallel strip lines, characterized in that, comprising: a horizontal feed plate and a vertical plate perpendicular to the horizontal feed plate; wherein: The horizontal feeder board is provided with a first port, a second port, a third port, a first port feeder, a second port feeder and a third port feeder; the first port feeder, the second port feeder and all The third port feeders are all composed of microstrip transmission lines, and the first port feeder is connected to the first port, the second port feeder is connected to the second port, and the third port feeder is connected to the The third port is connected; The horizontal feed board includes a first layer and a second layer and a plurality of first metal vias; wherein the via surface is connected to the plurality of first metal vias, and the first layer includes vias plane; the second layer includes a ground plane, and the ground plane is connected to the via plane through the first metal via hole; The vertical board includes a third layer, a common ground with a cross slit, a fourth layer, an impedance gradient structure, a second metal via, a filter, and a quarter-wavelength impedance converter, wherein the common ground is located at In the middle of the third layer and the fourth layer; the filter has oppositely bent top filtering branches; the filter is connected to the quarter-wavelength impedance converter and is composed of vertical double-sided parallel It is composed of striplines, and they are respectively symmetrically located on the third layer and the fourth layer; the top filter branch is connected to the common ground through the second metal via; the impedance gradient structure is located on the The fourth layer is connected to the first port feeder, the via surface and the filter respectively; Wherein, the first port, the first port feeder, the impedance gradient structure, the filter, the common ground, the quarter-wavelength impedance converter, the second port feeder, the The third port feeder, the second port and the third port form a signal transmission path. 2. The balun according to claim 1, wherein the microstrip transmission line, the vertical double-sided parallel strip line, the ground plane, the via plane, and the common ground are all conductive Metal. 3. The balun of claim 2, wherein the conductive metal is brass. 4. The balun according to claim 2 or 3, wherein the plurality of first metal vias are arranged in two rows with the same pitch. 5. The balun according to claim 2, wherein the first port, the second port and the third port are SMA connectors. 6. The balun according to claim 5, wherein the dielectric constant of the horizontal feed plate and the vertical plate are the same. 7. The balun of claim 1, wherein the horizontal feed plate and the vertical plate have different thicknesses. 8. The balun according to claim 4, wherein the number of the plurality of first metal vias is 10. 9. The balun according to claim 1, wherein there are two second metal vias; the first port, the first port feeder, the impedance gradient structure, the filter , the common ground, the quarter-wavelength impedance converter, the second port feeder, the third port feeder, the second port, and the third port form two signal interaction transmission paths.