CN110277619B - Balun transformer - Google Patents
Balun transformer Download PDFInfo
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- CN110277619B CN110277619B CN201910528761.7A CN201910528761A CN110277619B CN 110277619 B CN110277619 B CN 110277619B CN 201910528761 A CN201910528761 A CN 201910528761A CN 110277619 B CN110277619 B CN 110277619B
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- 239000000758 substrate Substances 0.000 claims abstract description 48
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- 239000003822 epoxy resin Substances 0.000 claims description 16
- 229920000647 polyepoxide Polymers 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 15
- JIYIUPFAJUGHNL-UHFFFAOYSA-N [O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[Mn++].[Mn++].[Mn++].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Zn++].[Zn++] Chemical group [O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[Mn++].[Mn++].[Mn++].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Zn++].[Zn++] JIYIUPFAJUGHNL-UHFFFAOYSA-N 0.000 claims description 10
- 230000002708 enhancing effect Effects 0.000 claims description 6
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- 238000003466 welding Methods 0.000 claims description 6
- 238000004891 communication Methods 0.000 claims description 3
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- 238000003780 insertion Methods 0.000 abstract description 8
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F17/00—Fixed inductances of the signal type
- H01F17/04—Fixed inductances of the signal type with magnetic core
- H01F17/06—Fixed inductances of the signal type with magnetic core with core substantially closed in itself, e.g. toroid
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/29—Terminals; Tapping arrangements for signal inductances
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P5/00—Coupling devices of the waveguide type
- H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
- H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced with unbalanced lines or devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F17/00—Fixed inductances of the signal type
- H01F2017/0093—Common mode choke coil
Abstract
The invention provides a balun transformer, which comprises a substrate with a circuit, a signal input port, two differential signal output ports, a common-mode inductor and a first shielding wire, wherein the signal input port is arranged on the substrate; the first conductive wire of the first shielding wire connects the signal input port with the input end of the common mode inductor, the second end of the first conductive wire is connected with the input end of the common mode inductor, and the first shielding layer of the first shielding wire is grounded. When the transformer is used, an input signal is transmitted to the common mode inductor from the signal input port through the first conductive wire, electromagnetic coupling matching is carried out on the input signal through the common mode inductor, an external interference signal is led into the ground through the first shielding layer, induced current generated by the first conductive wire is avoided, and interference caused by radiation of the signal transmitted on the first conductive wire is prevented, so that the transformer has better amplitude balance degree and lower insertion loss.
Description
Technical Field
The invention belongs to the technical field of communication electronic elements, and particularly relates to a balun transformer.
Background
Balun (Balun, also known as a balanced feed converter or transmission line balancer) is a key component of balanced circuit layout for filters, microwave balanced mixers, frequency multipliers, push-pull amplifiers and antenna feed networks. Currently, common balun transformers mainly realize balance-unbalance conversion through high-frequency transformers, and inductance coils of the high-frequency transformers need to be connected to a signal input port and/or a signal output end of the balun through enameled wires so as to transmit high-frequency signals through the enameled wires. However, the enameled wire can generate induced current in the high-frequency signal transmission process, and the induced current easily causes unstable line-to-line capacitance to form signal interference, so that the balun transformer is unstable in balance-to-unbalance conversion amplitude, the balun transformer is low in balance degree of balance-to-unbalance conversion performance, and the broadband point-to-point communication standard requirement cannot be met.
Disclosure of Invention
The invention aims to provide a balun transformer, which aims to solve the problem that the balun transformer is low in balance degree due to unstable balance-unbalance conversion amplitude in the prior art.
In order to achieve the above purpose, the technical scheme adopted by the invention is to provide a balun transformer, which comprises a substrate, a signal input port and two differential signal output ports, wherein the signal input port and the two differential signal output ports are arranged on the substrate, and a coupling circuit for realizing that the signal input port is respectively communicated with the two differential signal output ports; the coupling circuit comprises a common-mode inductor for electromagnetic coupling and a first shielding wire for connecting the common-mode inductor to the signal input port, wherein the common-mode inductor is arranged on the substrate, and two output ends of the common-mode inductor are respectively connected with two differential signal output ports; the first shielding wire comprises a first conductive wire used for transmitting electric signals, a first shielding layer wrapped outside the first conductive wire and a first insulating layer wrapped outside the first shielding layer, one end of the first conductive wire is connected with the signal input port, the other end of the first conductive wire is connected with two input ends of the common mode inductor, the first shielding layer is grounded, and the first insulating layer is fixed on the substrate.
Further, the balun transformer further comprises second shielding wires for connecting the common-mode inductor to the two differential signal output ports respectively, the second shielding wires comprise two second conductive wires connected with the two differential signal output ports respectively, a second shielding layer wrapped outside the two second conductive wires and a second insulating layer wrapped outside the second shielding layer, the two second conductive wires are connected with the two output ends of the common-mode inductor respectively, the second shielding layers are grounded, and the second insulating layer is fixed on the substrate.
Further, the balun transformer further comprises a resistor for enhancing balance degree of balance-unbalance conversion amplitude, the resistor comprises a first resistor for signal isolation, a second resistor and a third resistor for grounding isolation, two differential signal output ports are respectively connected to two ends of the first resistor, two ends of the second resistor are respectively connected with one differential signal output port and a grounding point, and two ends of the third resistor are respectively connected with the other differential signal output port and the grounding point.
Further, the first resistor, the second resistor and the third resistor are thick film resistors, and the first resistor, the second resistor and the third resistor are respectively encapsulated on the substrate by epoxy resin layers.
Further, the resistances of the first resistor, the second resistor and the third resistor are equal in magnitude.
Further, a first circuit for connecting the first resistor and the second resistor, a second circuit for connecting the first resistor and the third resistor and a third circuit for connecting the second resistor and the third resistor are arranged on the substrate, and the distance between the first circuit and the second circuit is equal to the distance between pins at two ends of the first resistor; the distance between the first circuit and the third circuit is equal to the distance between pins at two ends of the second resistor; the distance between the second circuit and the third circuit is equal to the distance between the pins at two ends of the third resistor, and the third circuit is a grounding wire.
Further, the balun transformer further comprises a feedback inductor, a third shielding wire and a fourth shielding wire, wherein the feedback inductor is used for forming a signal feedback bypass, the third shielding wire comprises a third conductive wire, a third shielding layer wrapped outside the third conductive wire and a third insulating layer wrapped outside the third shielding layer, the third conductive wire is connected with the input end of the feedback inductor, the third shielding layer is respectively connected with one differential signal output port and a grounding point through the first circuit, and the third insulating layer is fixed on the substrate; the fourth shielding wire comprises a fourth conductive wire, a fourth shielding layer wrapped outside the fourth conductive wire and a fourth insulating layer wrapped outside the fourth shielding layer, the fourth conductive wire is connected with the output end of the feedback inductor, the fourth shielding layer is grounded, and the fourth insulating layer is fixed on the substrate.
Further, the substrate is a ceramic plate, and the first conductive wire is connected with the ceramic plate in an electronic spot welding mode.
Further, the common mode inductor comprises a manganese-zinc ferrite core and two coils wound on the manganese-zinc ferrite core.
Further, each of the coils is a flat coil.
The balun transformer provided by the invention has the beneficial effects that: compared with the prior art, the balun transformer provided by the invention adopts the first shielding wire to replace the enameled wire used by connecting the input end of the common-mode inductor with the signal input port, and the first shielding wire is used as the signal transmission wire of the input end of the common-mode inductor, so that the interference of the first conductive wire inside the first shielding wire on transmission signals caused by induction current is effectively avoided, the stable performance of balun transformer balance-unbalance conversion is improved, and the balun transformer has very excellent in-band amplitude and phase balance. Meanwhile, the first shielding wire is used as a signal transmission wire of the input end of the common mode inductor, so that external electromagnetic interference and radio frequency interference can be effectively prevented from entering the first shielding wire to increase loss of transmission signals, and the signal transmitted on the first conductive wire can be effectively prevented from radiating out to cause interference, thereby effectively reducing loss of transmission signals and enabling the transformer to have lower insertion loss.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a balun transformer according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a common mode inductor according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a substrate provided with a signal input port and a differential signal output port according to an embodiment of the present invention.
Wherein, the first reference mark of each drawing in the figure:
1-a substrate; 11-a signal input port; 12-a differential signal output port; 13-a first line; 14 second
A line; 15-a third line;
a 2-common mode inductor; 21-manganese zinc ferrite core; 22-coil;
3-a first shielding wire; 31-a first conductive line; 32-a first shielding layer; 33-a first insulating layer;
4-a second shield wire; 41-a second conductive line; 42-a second shielding layer; 43-a second insulating layer;
a 5-resistor; 51-a first resistor; 52-a second resistor; 53-a third resistor;
a 6-feedback inductor; 7-a third shielded wire; 71-a third shielding layer; 72-a third insulating layer;
8-fourth shielded wires; 81-a fourth shielding layer; 82-fourth insulating layer.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It will be understood that when an element is referred to as being "connected to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise. The meaning of "a number" is one or more than one unless specifically defined otherwise.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1 to 3, a balun transformer provided by an embodiment of the present invention will be described. The balun transformer provided by the invention comprises a substrate 1, a signal input port 11 and two differential signal output ports 12 which are arranged on the substrate 1, and a coupling circuit for realizing that the signal input port 11 is respectively communicated with the two differential signal output ports 12; the coupling circuit comprises a common mode inductor 2 for electromagnetic coupling and a first shielding line 3 for connecting the common mode inductor 2 to a signal input port 11, wherein the common mode inductor 2 is arranged on a substrate 1, and two output ends of the common mode inductor 2 are respectively connected with two differential signal output ports 12; the first shield wire 3 includes a first conductive wire 31 for transmitting an electric signal, a first shield layer 32 wrapped outside the first conductive wire 31, and a first insulating layer 33 wrapped outside the first shield layer 32, one end of the first conductive wire 31 is connected to the signal input port 11, the other end of the first conductive wire 31 is connected to both input ends of the common mode inductor 2, the first shield layer 32 is grounded, and the first insulating layer 33 is fixed on the substrate 1. When the transformer is used, an input signal is transmitted to the input end of the common mode inductor 2 from the signal input port 11 through the first conductive wire 31, electromagnetic coupling matching is carried out on the input signal through the common mode inductor 2, external interference signals such as external electromagnetic interference and radio frequency interference are led into the ground through the first shielding layer 32, induced current generated by the first conductive wire 31 can be avoided, meanwhile, interference caused by radiation of the signal transmitted on the first conductive wire 31 can be effectively prevented, and therefore the transformer has better amplitude balance degree and lower insertion loss.
Compared with the prior art, the balun transformer provided by the invention adopts the first shielding wire 3 to replace the enameled wire used by connecting the common-mode inductor 2 with the signal input port 11, and the first shielding wire 3 is used as the signal transmission wire of the input end of the common-mode inductor 2, so that the interference of induced current generated by the first conductive wire 31 in the first shielding wire 3 on transmission signals is effectively avoided, the stable performance of balun transformer balance-unbalance conversion is improved, and the balun transformer has very excellent in-band amplitude and phase balance. Meanwhile, the first shielding wire 3 is used as a signal transmission line of the input end of the common mode inductor 2, so that external electromagnetic interference and radio frequency interference can be effectively prevented from entering the first shielding wire 3 to increase loss of transmission signals, and the signal transmitted on the first conductive wire 31 can be effectively prevented from being radiated to cause interference, thereby effectively reducing loss of transmission signals and enabling the transformer to have lower insertion loss.
In addition, under the condition of not adding a capacitor, the balun transformer provided by the invention not only can ensure the excellent filtering characteristic, but also has the capability of converting balun unbalance into balanced signals, and has the advantages of good electrical performance, good impedance matching effect, low insertion loss, good high passband selectivity and high output signal amplitude balance characteristic, and the balun transformer is simple and compact in structure and small in volume.
Preferably, referring to fig. 2 together, as a specific implementation manner of the balun transformer provided by the embodiment of the present invention, the common-mode inductor 2 includes a manganese-zinc ferrite core and two coils 22 wound on the manganese-zinc ferrite core 21, and the inductor is manufactured by adopting the manganese-zinc ferrite core 21 with low loss, so that the balun transformer achieves the purpose of being applicable to low frequency band use, has the broadband characteristic (0.5 MHz-6 GHz) of low frequency to high frequency ultra-bandwidth application, realizes the application requirements of the balun transformer that the balun transformer can work in a wider bandwidth and has low insertion loss and high-amplitude balance, expands the variety of the balun transformer, saves the assembly space, meets the test requirements of GJB1661 and GJB360B, and meets the military requirements. Other components and working principles of the transformer and the inductor are realized by adopting the prior art known to those skilled in the art, and are not described herein.
Preferably, referring to fig. 2, as a specific implementation of the balun transformer provided by the embodiment of the present invention, the coil 22 is a flat coil. The flat coil is combined with the maximum area of the manganese-zinc ferrite core 21, so that the magnetic induction intensity is high, the performance is stable, the specific saturated magnetic density and the specific cross section of the manganese-zinc ferrite core 21 can be applied to reduce the magnetic conductivity of the manganese-zinc ferrite core 21, the influence of bias current can be reduced, the maximum utilization of the magnetic induction intensity is achieved, the loss is low, the environmental adaptability is particularly good, the performance is stable, and the normal operation of an electromagnetic interference device is prevented.
Further, referring to fig. 1 together, as a specific implementation manner of the balun transformer provided in the embodiment of the present invention, the balun transformer further includes a second shielding wire 4 for connecting the common-mode inductor 2 to the two differential signal output ports 12, the second shielding wire 4 includes two second conductive wires 41 connected to the two differential signal output ports 12 respectively, a second shielding layer 42 wrapped around the two second conductive wires 41, and a second insulating layer 43 wrapped around the second shielding layer 42, where the two second conductive wires 41 are connected to the two output ends of the common-mode inductor 2 respectively, the second shielding layer 42 is grounded, and the second insulating layer 43 is fixed on the substrate 1.
In this embodiment, the second shielding wire 4 is used to replace the enameled wire used for connecting the common-mode inductor 2 with the signal output end, and the second shielding wire 4 is used as the signal transmission wire of the output end of the common-mode inductor 2, so that the interference of the induced current generated by the second conductive wire 41 inside the second shielding wire 4 on the transmission signal is effectively avoided, the stability of balun transformer balance-unbalance conversion is improved, and the balun transformer has very excellent in-band amplitude and phase balance. Meanwhile, the second shielding wire 4 is used as a signal transmission wire at the output end of the common mode inductor 2, so that the loss of a transmission signal can be effectively reduced, and the transformer has lower insertion loss.
Further, referring to fig. 1 together, as a specific implementation manner of the balun transformer provided by the embodiment of the present invention, the balun transformer further includes a resistor 5 for enhancing the balance degree of the balun amplitude, the resistor 5 includes a first resistor 51 for signal isolation, and a second resistor 52 and a third resistor 53 for ground isolation, two ends of the first resistor 51 are respectively connected to two differential signal output ports 12, two ends of the second resistor 52 are respectively connected to one differential signal output port 12 and a ground point, and two ends of the third resistor 53 are respectively connected to the other differential signal output port 12 and the ground point.
In this embodiment, a resistor 5 is provided between the common mode inductor 2 and the signal output to enhance the amplitude balance of balun transformer balun balance-unbalance conversion. Specifically, the resistor 5 includes a first resistor 51, a second resistor 52 and a third resistor 53 connected in series, and the first resistor 51, the second resistor 52 and the third resistor 53 are integrated on the substrate 1 in a triangle arrangement, signals are isolated by the first resistor 51, the second resistor 52 and the third resistor 53 are isolated from the ground, so that the amplitude of signals output by the signal output end is smoother, the in-band excellent amplitude and the phase balance degree of the balun transformer are enhanced, and the balun transformer has lower insertion loss.
Further, the first resistor 51, the second resistor 52 and the third resistor 53 are thick film resistors, and the first resistor 51, the second resistor 52 and the third resistor 53 are respectively encapsulated on the substrate 1 by adopting epoxy resin layers, so that the first resistor 51, the second resistor 52 and the third resistor 53 are integrally formed on the substrate 1, the volume of the balun transformer is reduced, and the balun transformer and other circuit elements are conveniently integrated.
Preferably, the resistances of the first resistor 51, the second resistor 52 and the third resistor 53 are equal in size, so that the amplitude of balun transformer balun balance-unbalance conversion is further kept stable, and the amplitude balance degree of balun transformer balance-unbalance conversion is enhanced.
Preferably, the first resistor 51, the second resistor 52 and the third resistor 53 are each 150Ω.
Preferably, the substrate 1 is a ceramic substrate, and the first conductive wire 31 of the first shielding wire 3 is connected with the ceramic substrate by an electronic spot welding manner, so as to reduce the capacitance between the first shielding wire 3 and the ceramic substrate, thereby optimizing the amplitude of balun transformer balun balance-unbalance conversion and enhancing the amplitude balance of balun transformer balance-unbalance conversion.
Preferably, the second conductive wire 41 is connected to the ceramic substrate by electronic spot welding, and the first insulating layer 33 and the second insulating layer 43 are encapsulated on the ceramic substrate by using epoxy resin layers, so as to reduce capacitance between the second conductive wire 41, the first insulating layer 33 and the second insulating layer 43 and the ceramic substrate, thereby optimizing the amplitude of balun transformer balun transformation and enhancing the amplitude balance of balun transformer balun transformation.
Further, referring to fig. 1 together, as a specific implementation manner of the balun transformer provided in the embodiment of the present invention, a first circuit 13 connected to the first resistor 51 and the second resistor 52, a second circuit 14 connected to the first resistor 51 and the third resistor 53, and a third circuit 15 connected to the second resistor 52 and the third resistor 53 are disposed on the substrate 1, where a distance between the first circuit 13 and the second circuit 14 is equal to a distance between pins at two ends of the first resistor 51; the distance between the first circuit 13 and the third circuit 15 is equal to the distance between the pins at the two ends of the second resistor 52; the distance between the second circuit 14 and the third circuit 15 is equal to the distance between the pins at the two ends of the third resistor 53, and the third circuit 15 is a ground line.
The first circuit 13, the second circuit 14 and the third circuit 15 are printed on the substrate 1 in a printing manner, and pads for welding connection are arranged on the first circuit 13, the second circuit 14 and the third circuit 15, so that the welding connection of wiring and electronic elements is facilitated, and the volume of the balun transformer is reduced.
In this embodiment, the first resistor 51 and the second resistor 52 are welded through the first circuit 13, the first resistor 51 and the third resistor 53 are welded through the second circuit 14, the second resistor 52 and the third resistor 53 are welded through the third circuit 15, the use of connecting wires between the first resistor 51, the second resistor 52 and the third resistor 53 is reduced, the interference of capacitance between the connecting wires is effectively avoided, the amplitude balance degree of balun transformer balance-unbalance conversion is enhanced, the trouble of wiring is reduced, and the volume of balun transformer is reduced.
Further, as a specific implementation manner of the transformer balun provided by the embodiment of the present invention, the first circuit 13, the second circuit 14 and the third circuit 15 are printed on the ceramic substrate in a circuit printing manner, so as to reduce the volume of the transformer balun. The first epoxy resin layer which encapsulates the first circuit 13, the second circuit 14 and the third circuit 15 on the ceramic substrate is arranged on the ceramic substrate, and the first circuit 13, the second circuit 14 and the third circuit 15 are encapsulated on the ceramic substrate through the first epoxy resin layer, so that the stability of the first circuit 13, the second circuit 14 and the third circuit 15 attached on the ceramic substrate is enhanced, the first circuit 13, the second circuit 14 and the third circuit 15 are prevented from being easy to generate bending short circuit or even fracture when being subjected to vibration or impact, and the capacity of the transformer type balun against vibration and impact is effectively improved.
Further, as a specific implementation manner of the transformer balun provided by the embodiment of the invention, the pins of the input end and/or the output end of the common-mode inductor 2 are supported on the first epoxy resin layer, the first epoxy resin layer is provided with the second epoxy resin layer for encapsulating and fixing the pins of the input end and/or the output end of the common-mode inductor 2 on the first epoxy resin layer, and the common-mode inductor 2 is supported and fixed on the second epoxy resin layer, and the pins of the input end and/or the output end of the common-mode inductor 2 are encapsulated and fixed on the first epoxy resin layer through the second epoxy resin layer, so that the stability of the pins of the input end and/or the output end of the common-mode inductor 2 is enhanced, and the pins of the input end and/or the output end of the common-mode inductor 2 are prevented from being easy to generate bending short circuit or even fracture when being subjected to vibration or impact, thereby effectively improving the anti-vibration and anti-impact capability of the transformer type balun.
Further, as a specific implementation manner of the transformer balun provided by the embodiment of the invention, the second epoxy resin layer is provided with the third epoxy resin layer for encapsulating and fixing the common-mode inductor 2 on the second epoxy resin layer, so that the common-mode inductor 2 is prevented from being easily swayed or oscillated to be damaged when being vibrated or impacted, the stability of the common-mode inductor 2 arranged on the ceramic substrate is enhanced, and the vibration resistance and impact resistance of the transformer type balun are effectively improved.
Further, referring to fig. 1 together, as a specific implementation manner of the balun transformer provided by the embodiment of the present invention, the balun transformer further includes a feedback inductor 6 for forming a signal feedback bypass, a third shielding wire 7 and a fourth shielding wire 8, the third shielding wire 7 includes a third conductive wire, a third shielding layer 71 wrapped around the third conductive wire, and a third insulating layer 72 wrapped around the third shielding layer 71, the third conductive wire is connected to an input end of the feedback inductor 6, the third shielding layer 71 is connected to a differential signal output port 12 and a ground point through a first line 13, and the third insulating layer 72 is fixed on the substrate 1; the fourth shielding wire 8 comprises a fourth conductive wire, a fourth shielding layer 81 wrapped outside the fourth conductive wire and a fourth insulating layer 82 wrapped outside the fourth shielding layer 81, the fourth conductive wire is connected with the output end of the feedback inductor 6, the fourth shielding layer 81 is grounded, and the fourth insulating layer 82 is fixed on the substrate 1.
In this embodiment, the input signal is transmitted from the signal input port 11 to the common-mode inductor 2, and the input signal is distributed to the two differential signal output ports 12 after being subjected to balun transformation by the common-mode inductor 2, so that the line-to-line capacitance of the feedback inductor 6 has a bypass effect at the ground end, and forms signal feedback, and the line-to-line capacitance of the feedback inductor 6 is prevented from forming interference, thereby further optimizing the balun transformer amplitude, and enhancing the balun transformer amplitude balance.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (7)
1. The balun transformer comprises a substrate, a signal input port, two differential signal output ports and a coupling circuit, wherein the signal input port and the two differential signal output ports are arranged on the substrate, and the coupling circuit is used for realizing communication between the signal input port and the two differential signal output ports respectively; the method is characterized in that: the coupling circuit comprises a common-mode inductor for electromagnetic coupling and a first shielding wire for connecting the common-mode inductor to the signal input port, wherein the common-mode inductor is arranged on the substrate, and two output ends of the common-mode inductor are respectively connected with two differential signal output ports; the first shielding wire comprises a first conductive wire used for transmitting electric signals, a first shielding layer wrapped outside the first conductive wire and a first insulating layer wrapped outside the first shielding layer, one end of the first conductive wire is connected with the signal input port, the other end of the first conductive wire is connected with two input ends of the common mode inductor, the first shielding layer is grounded, and the first insulating layer is fixed on the substrate;
the balun transformer further comprises a resistor for enhancing the balance degree of the balance-unbalance conversion amplitude, the resistor comprises a first resistor for signal isolation, a second resistor and a third resistor for grounding isolation, two ends of the first resistor are respectively connected with two differential signal output ports, two ends of the second resistor are respectively connected with one differential signal output port and a grounding point, and two ends of the third resistor are respectively connected with the other differential signal output port and the grounding point;
the first resistor, the second resistor and the third resistor are thick film resistors, and the first resistor, the second resistor and the third resistor are respectively encapsulated on the substrate by adopting epoxy resin layers;
the resistances of the first resistor, the second resistor and the third resistor are equal.
2. Balun transformer according to claim 1, characterized in that: the balun transformer further comprises second shielding wires used for connecting the common-mode inductor to two differential signal output ports respectively, each second shielding wire comprises two second conductive wires connected with two differential signal output ports respectively, a second shielding layer wrapped outside the two second conductive wires and a second insulating layer wrapped outside the second shielding layer, the two second conductive wires are connected with two output ends of the common-mode inductor respectively, the second shielding layers are grounded, and the second insulating layer is fixed on the substrate.
3. Balun transformer according to claim 2, characterized in that: the substrate is provided with a first circuit for connecting the first resistor and the second resistor, a second circuit for connecting the first resistor and the third resistor and a third circuit for connecting the second resistor and the third resistor, and the distance between the first circuit and the second circuit is equal to the distance between pins at two ends of the first resistor; the distance between the first circuit and the third circuit is equal to the distance between pins at two ends of the second resistor; the distance between the second circuit and the third circuit is equal to the distance between the pins at two ends of the third resistor, and the third circuit is a grounding wire.
4. A balun transformer as claimed in claim 3, wherein: the balun transformer further comprises a feedback inductor, a third shielding wire and a fourth shielding wire, wherein the feedback inductor is used for forming a signal feedback bypass, the third shielding wire comprises a third conductive wire, a third shielding layer wrapped outside the third conductive wire and a third insulating layer wrapped outside the third shielding layer, the third conductive wire is connected with the input end of the feedback inductor, the third shielding layer is respectively connected with one differential signal output port and a grounding point through the first circuit, and the third insulating layer is fixed on the substrate; the fourth shielding wire comprises a fourth conductive wire, a fourth shielding layer wrapped outside the fourth conductive wire and a fourth insulating layer wrapped outside the fourth shielding layer, the fourth conductive wire is connected with the output end of the feedback inductor, the fourth shielding layer is grounded, and the fourth insulating layer is fixed on the substrate.
5. Balun transformer according to any one of claims 1 to 4, characterized in that: the base plate is a ceramic plate, and the first conductive wire is connected with the ceramic plate in an electronic spot welding mode.
6. Balun transformer according to any one of claims 1 to 4, characterized in that: the common mode inductor comprises a manganese-zinc ferrite core and two coils wound on the manganese-zinc ferrite core.
7. Balun transformer according to claim 6, characterized in that: each coil is a flat coil.
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| CN201910528761.7A CN110277619B (en) | 2019-06-18 | 2019-06-18 | Balun transformer |
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